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Questions related to RF Engineering
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I know that I should compare their actuation voltage, capacitance ratio, and S-parameters. Apart from the mentioned characteristics, are there any other ones that I should compare?
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Power rating, operating temperature range, package.
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In the circular monopole antenna with partial ground plane is there to make it ultra wide band or match the impedance of circular patch?
Please clear this confusion for me? Because, usually, we do inset feed to match the impedance. here we are not doing inset feed but edge feed. so, the purpose of partial ground plane is just to increase the bandwidth of antenna or to match the impedance as well?
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If this is a monopole then it is quarter wave resonant. You usually see matching slots in microstrip patches, which are half-wave resonant, however slots could still be used here to change the match.
Making the monopole round increases its bandwidth compared to a thin wire monopole. Thick monopoles have a wider bandwidth than thin monopoles. The shape of the ground changes both the match and the bandwidth, usually the match determines the bandwidth so changing one changes the other.
This is not a microstrip patch with a partial ground, it is a monopole fed from microstrip, with an edge ground rather than a flat ground perpendicular to the monopole.
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Hello good time
What metals can be used in the design of high frequency devices such as Coaxial transmission lines , waveguides, coaxial to waveguide adapters? (Diamagnetic, paramagnetic or ferromagnetic)
For example, can I use tungsten rod , which has a magnetic permeability coefficient of 1, to build a coaxial transmission line? (What is the appropriate magnetic permeability number for the metal used to have low insertion loss(S21)?)
Thank You
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PCB dimensions are 30mm*18mm. Substrate: FR4 (1.6mm).
Frequencies of interests: 868MHz and 2.4GHz (Dual Band antenna)
Omnidirectional pattern idealy.
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First of all,size is enough for designing an antenna which resonating frequency of less than 1ghz. But you need to cut some slots on the patch,and also cut some slots on the ground for greater return loss.
… Read more
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Hello to all
Two questions
1. Does the use of metals with high magnetic permeability, such as iron alloy in the waveguide, cause insertion losses?
2- What about chrome or copper plating?
If you know the article in this field, please introduce it. Thank you
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Please find the attached files.
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Hi,
I am trying to simulate an antenna placed on a FR4 substrate (snapshot attached). PCB top and bottom layer is metal. For this case, to assign a port, I have just drawn a rectangle at the edge of the PCB having a width same as the feedline and length same as the PCB height.
Is it the correct way of assigning lumped port for my case (grounded CPW)? If not, would you please tell how should I assign the port accurately?
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Thanks everyone.
I have found my answer through contacting Ansys team. My process of assigning lumped port (shown in the picture) for the grounded CPW structure is correct where top and bottom metal is connected through VIAs.
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I am looking for papers/articles concentrated on UAS/drone wing antennas. Any directions are appreciated.
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Dear Meenakshi Kohli:
You can benefit from these valuable Links, and articles about your topic:
I hope it will be helpful...
Best wishes....
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So, if I have data of one linear polarization and then 90 deg to the first polarization. How can I calculate these two amplitudes and phases so that it will be right hand circular polarized? Please guide
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Dear Meenakshi Kohli:
As you know, The polarization in which E field radiates energy in both the horizontal plane and vertical plane and in all the planes in between is known as circular polarization. In this polarization, electric field has two linear components which are perpendicular to each other with equal amplitude and 90 degree phase difference. The resulting E-field rotates in a circle around the direction of propagation. Based on direction of rotation there are two types viz. RHCP and LHCP. Circularly polarized light signal can be generated by passing linear polarized light signal through quarter wave plate (λ/4) at angle of 45 degree to the optical axis of plate.
############****
The advantages of Circular Polarization:
➨No polarization adjustment is required as it is fixed using OMT (Orthomode Transducer).
➨There is less chance of cross pol interference.
➨RFID reader does not have to be on the same plane and similar heights as RFID tags unlike linear polarization RFID reader.
➨RFID reader does not require to know the tag orientation unlike linear polarized RFID reader. Hence it is used for applications where one does not know the orientation of RFID tags while reading the data.
disadvantages of Circular Polarization
##########****
disadvantages of Circular Polarization:
➨It makes cost of antenna system higher.
➨It offers slightly lower cross pol isolation.
➨It offers shorter read range for RFID reader
You can benefit from this valuable article about your topic:
"Linear to left- and right-hand circular polarization conversion by using a metasurface structure"
Abstract:
By using a metasurface (MS) structure, a linearly polarized wave is converted to circularly polarized waves. Both right- and left-handed circular polarizations (RHCPs and LHCP) are obtained by a simple configuration in the proposed structure which consists of 16 unit cells arranged in a 4 × 4 layout. Each unit cell contains five horizontal and parallel strips embedded in a rectangular frame in which a single diagonal strip is placed from one corner to the opposed one. It is shown that the orientation of the diagonal line determines the handedness of the converted signal to be either LHCP or RHCP. In order to show the working conditions of the MS structure, scattering parameters are found for both co-polarized and cross-polarized responses. Axial ratio, an indicator for polarization conversion, is then obtained by dividing cross-polar response to co-polar response to demonstrate the transformation. The structure works for horizontally and vertically polarized linear waves in a wide band frequency range which is approximately 510 MHz. Since the suggested MS model is composed of a simple geometry for polarization conversion, it can be easily adjusted in any desired frequency bands for a variety of applications from the defence industry to medical, education, or communication areas.
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Also you can take a look at:
"Linear and circular-polarization conversion in X-band using anisotropic metasurface"
I hope it will be helpful...
Best wishes....
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Is electrical length and electrical length in degrees, the same thing? How to calculate electrical length in degrees?
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The first complete wavelength() for 360 degrees is calculated using the calculations shown below. The electrical length is represented by the phase shift in degrees. = c/frequency, where c= 3 x 108 m/sec.
The formula v=f v = f expresses the connection between velocity, frequency, and wavelength. If velocity is measured in meters per second and frequency is measured in cycles per second, then has units of meters/cycle. By comparing the length of a cable to its wavelength, we may tell if it is electrically short or long.
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I have designed a bilayered structure on CST which is having copper patches as upper and bottom layers and a substrate sandwiched in between but I want LC equivalent circuit for the whole structure.
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Dear Asfandiyar Khan thanks for asking this very interesting technical question on RG. As an inorganic chemist I'm absolutely not a proven expert in this field. However, I know that it often pays off to search the "Questions" and "Publications" sections of RG directly for helpful hints. In this context please have a look at the following closely related technical questions which have been posted earlier on RG. It might help you in your analysis when you check the answers given to those questions:
How can extract antenna equivalent circuit from CST microwave studio?
(9 answers)
and
How to draw equivalent circuit model for antennas?
(28 answers)
I hope this information is useful. Good luck with your work and best wishes!
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I have a DC/AC high voltage transformer to feed a spark plug to generate plasma using an arc discharge.
The output voltage goes up to 30kVpp and 400khz
When connecting one of the secondary of the transformer to GND at 5% of the breakdown (then the secondary is open circuit because spark gap voltage is under breakdown) high energy current is discharged to ground breaking Push-Pull circuit.
I have set a 150 ohms resistor to ground and measured 260mA.
The problem gets worse if the ground is connected to the Large plasma steel structure
I can not explain the problem using classical approach
Here is the circuit:
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Javier Luis López I would think mostly of capacitance between primary and secondary windings..
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Can I connect 2 capacitors in series/parallel to get 180 deg phase shift,? only 2 capacitors?
I need to have total impedance of 200 ohms at 2.4 GHz.
please advise
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Both are different things :
1.phase shift between input and output across a device
2. phase shift between current and voltage across a device
Two capacitors in series can not provide phase shift of 180 between input and output. So, it depends upon the quantities in which you need phase shift. No, nowadays amplifiers are available in miniature form or IC form (maybe you can use that, comparable or even smaller than the size of conventional capacitors).
That's how I can help, may be some faculty or researcher from the concerned domain may provide a useful answer and suggestion to your query.
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Is it possible to use a Dual polarized antenna instead of CP antenna? For example in RFID: Which antenna can detect most of the tag? Circulsr or dusl polarized antenna?
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Dear Debraj Kar ,
I think you already constructed your antenna.
But the circular polarized antenna will receive from either vertically or horizontally polarized antennas. The circular polarization is composed of two linear polarizations which are perpendicular to each other.
So, if you use double polarization it is preferred to be like the circular polarization.
Best wishes
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Dealing with a helix antenna, made with flexible material and not rigid like using a PCB board or wire. At the beginning of the helix is too close to the ground plane, causing coupling. How can I get rid of this inductance problem, if I cannot use a PCB board design here.
Please advise.
Thank you
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Hello, if I understand you correctly, I can advise you to use high impedance "barriers" (EBG - electromagnetic band-gap), which provide increased isolation of the radiator from the environment. You can use them both behind the emitter and on the side. egards, Yu
Hello, if I understand you correctly, I can advise you to use high impedance "barriers" (EBG - electromagnetic band-gap), which provide increased isolation of the radiator from the environment. You can use them both behind the emitter and on the side.
Regards, Yurii.
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I am using HFSS simulation to connect electric circuit (in series with resistor and DC bias) to metamaterial to study the response of the metamaterial to the external bias voltage. I do not know how to couple the external circuit to the metamaterial. Any help would be appreciated.
Thanks.
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Good question
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As part of my research, I need to couple a loaded, custom-sized, rectangular, waveguide (in which a hybrid mode propagates at 8.5GHz) to either a) a coaxial transmission line or b) to a standard X-band waveguide.
I need to understand the design and optimization processes for both including impedance matching and/or mode conversion as required.
What is the best, most efficient way of approaching such a task?
Any useful resources on the topic would also be very much appreciated.
Kind Regards
Simon
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ok I see ..some metamaterial..which definition for the "wave impedance" are you using.?.500 Ohm appears rather high to me and depends on the type of mode.For more detail you can consult the books by Pozar on microwave engineering
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I am unable to quantify the role of passive components when it is attached with the antenna. For various frequency bands like L,S,C,X the specifications of the active circuits changes but what will be the change in passive components and the antenna with respect to the frequency band.
Kindly give some answer or link , I am fully confused and I have to make a RF transceiver for demonstration purpose for the above mentioned frequency band.
If I get the block diagram with specs, it will be highly appreciated.
I hope I will get the answer at the earliest
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I am not asking about the discrete circuit, these all are plug and play circuit I'm asking about the passive components used in RF transreceiver design (example your mobile phone using patch antenna)
Regards
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I want to know the attenuation constant of a microstrip line. And I measured s11, s21, s22.
Can I draw attenuation of the line by subtracting both mismatch losses at the port and the load from s21 as shown below?
Mismatch loss at the port: sm1=10*log10((1-10.^(s11(:,2)./10)))
Mismatch loss at the load: sm2=10*log10((1-10.^(s22(:,2)./10)))
attenuation=s21-sm1-sm2
attenuation constant=ling length*attenuation
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My open-source software project called SignalIntegrity (www.pypi.org/SignalIntegrity) has a fitter that will fit RLGC as well as loss-tangent and skin-effect loss. You simply supply a two-port s-parameter file.
All of the details of how I do this are in my recently published book "S-Parameters for Signal Integrity" ( ), but like I said, the source code for all of this is in the project.
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I am using HFSS to simulate a periodic structure which extends to infinity in one direction and finite in other (n x infinity array) for s-parameters. I set the boundary condition on top and bottom to be PEC and master/slave on x-direction and assigned wave port excitation but it doesn't work. Can you please suggest me a suitable boundary condition for my problem?
Thanks
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Lets say you are making an FSS with infinite periodicity in x and only 5 elements or 1 element in y. Then you put periodic boundaries along x only and the exact no of elements along y. Now for y there are three options depending on the scenario you are simulating. Like TE or TM. PEC boundary will only be assigned if your E field in parallel to Y axis as declared in waveport. otherwise for E field normal to y axis use PMC. However a very common prob occurs that the dimension of radiation box starts resonating causing un necessary peaks so to avoid that the best solution for both TE and TM polarization is using PML on the finite sides also radiation can be used but best is using PML and the polarization is steered though port definition of E vector.
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Hello.
I used to run simulation for the antenna with lumped port till very recently.
However, realized that it is quite risky when it comes to monitor the real wave intensity and affect to other material.
However, every time when I try to run the simulation with wave port, error comes out.
even though it was run well on with lumped port.
i believe it was
Port refinement, process hf3d error: Port 1 is assigned to an internal face. Only allowed with lumped ports..
I tried quite many times to solve this problem.
But unable to fix it.
What I tried to do was make an antenna tuner on the loop antenna with 13.56MHz
Is there anyone able to help me with?
Thanks
and respect all whom read this.
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Many data sheets for power amplifiers state the P1O ( 1dB compression point) and Psat (saturated power) levels of the device. what is the difference between them, are they same?
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The saturation power is the maximum output power Ps. The one dB compression point is the point at the Po versus Pi curve where the saturation output power is reduced by one dB. I would like that you refer to the figure of Po vs.Pi in the link: https://ebrary.net/78582/computer_science/compression_point
Best wishes
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I have done the simulations to find the s-parameters of EM waves for metallic (copper) wire array system ion COMSOL. The EM waves is reflected back and there is hardly any transmission. However, the phase of the transmission coefficient is greater than zero (figures attached). Can anyone explain why is that so?
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The effect is produced by tiny rounding errors that add up when the amplitudes are very small. The cause is ultimately the math. co-processor in the computer.
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hello everyone
I am trying to import an axial electical field in a linac structure from CST in to ASTRA ,
Can anyone help me?
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Sounds like PITZ business :) First thing to check would be the phase. Is it MMMG for both? Mare sure MMMG, switch off space charge, track a single particle through and then compare the orbits (or with two particles for comparing the sizes). Maybe some clues already from the orbit. Besides, one could refine mesh lines for the field map imported to Astra. Or simply run a particle tracking job in CST tracking solver with the CST fields you got already. Generally, the paraxials should represent 3D fields if e.g. no asymmetry-induced kicks. Cheers.
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I've got a bunch of antennas with varying VSWRs and dBi ratings, and a couple of standard SMA headers from various 2.4Ghz radios. I would like to learn how antenna selection will affect RF power and range.
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Dear Mark,
welcome,
I would like to express the colleagues answer in an other way. In the link budget one defines also the effective isotropic radiated power EIRP which is the the transmit power Pt issued by the power amplifier at the input of the antenna times the antenna gain, that is the EIRP= Pt. At where At is the transmit antenna gain. Expressed in dBm= 10 log (Pt/1mw) + At ,
the EIRP is the quantity used to calculate the power reaching the receiver antenna. As the antenna gain increases the the received power will increase proportionally. This will increase the S/N ratio for the range and same receiver.
Best wishes
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I have calculated and plotted the dispersion relation for a cylindrical wave-guide partially loaded with an artificial dielectric. I now need to calculate and plot my cyclotron electron beam / wave-line on my dispersion plot. Can anyone explain how this is done?
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Sorry that I am not up to speed on the relativistic beams you are working with.
However - look out for the units used in your curves. Wavenumber times velocity is radians per second, which implies a rotation rate. Presumably the wavenumber gives the rotation of the mode as it progresses along the axis.
You need to make sure that your dispersion diagram has the correct things plotted so that a slope on it is in radians per second - perhaps the beta axis needs to be in radians (of mode pattern) per radian (of physical rotation).
I have a gut feeling that an upward shift (up the frequency axis based on the cyclotron frequency) could make sense, but no help to offer!
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Hi all
I am currently doing a project to make a wireless sensor, which should have the following structure: overview.png
My task is to connect the double split ring resonator (DSRR) and vector network analyser (VNA) wirelessly. DSRR is a microstrip resonator whose resonant frequency shifts if liquid is introduced to flow through the capillary. Therefore, it can be used as a sensor to detect liquid.
I know there are several possible ways to achieve the wireless connection, but I am totally stuck.
I tried to use rectangular patch antenna as TX/RX antennas similar to the paper “Wireless Sensing of Complex Dielectric Permittivity of Liquids Based on the RFID” (but the paper uses ultrawide band microstrip dipole antenna). However, I failed, my CST simulation results show no resonance.
I used cross polarization, so cross talk is not a big issue?
In addition, I guess because the DSRR does not have a distinctive peak, the overall frequency response cannot reflect the DSRR resonance.
I am not sure whether my interpretation is correct or not, can anyone help me?
Moreover, my supervisors suggest me to use antennas with higher directivity. Is there any microstrip antenna with simple structure can achieve much higher directivity?
Furthermore, is it also possible to use nfc antenna or near-field antenna for the wireless connection? But I don’t know how to realise it with microstrip at GHz. Neither don’t I know how to build the LC tank if the DSRR has inductive impedance.
Please help me out
Many thanks
Ran Tao
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I would propose to use ferrite cored transformers to couple the VNA to the split ring resonators. This would be a near field coupling. In order to decouple the transformers they must be perpendicularly oriented.
One other solution which may require more electronic effort is to input the output of your circuit on a peak detector using Schottky diodes and acquire this DC voltage and send it to nearby computer to store it and post process the data. You can also build the oscillator on the same board.
Best wishes
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I need to calculate the dispersion curve for a cylindrical waveguide partially loaded with an artificial material. For reference at present I have papers by Brand (2006) and Rao (2007). Can anyone suggest:
a) Any other reference material that may be useful.
b) Any commonly used methods used to complete the calculation.
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My colleague Justin G. Pollock published on metamaterial-lined cylindrical waveguides, including some dispersion analyses:
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Hello all,
I am trying to measure "Noise Figure (NF)" value of the LNA (IC of MAX2678) by using VNA (without Noise Source, and with perfect 50-ohm test systems) and I am following the steps in given "Vector Network Analyzer Application Note " as attached in the following link or in the attachment:
However, even though I am adjusting the LNA input power so that LNA does not enter compression (saturation) and besides, I am calibrating my VNA in the frequency range that meets with my LNA's operating frequency range, in the end, I am observing "negative Noise Figure" from the LNA measurements.
In theory, it is impossible to see negative NF. So; is there anyone who has experienced such a situation before? Or why I am observing "negative noise figure " from my LNA measurement with VNA (without Noise source)?
Best regards,
Thank you in advance.
Huriye.
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You are using the so called cold noise measurement technique. This type of measurement using measured s parameter data and noise power values obtained from source pulling about a reflection coefficient with a Gamma of 0.5 or so. Be certain that the device is stable and check to see if the s data returned during measurement makes sense. Is the device matched? As a sanity check that your cal is good, measure a simple item prior to your LNA DUT. A 3 db pad should return ~ a 3 dB NF.
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How do I create a three port s-parameters matrix of a three port device from a two port s-parameters measured between each of its two ports assuming the third is 50 ohm terminated.
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What you did manually is what most old multi-port VNAs did inside: Measuring one set of two-port s-parameter while terminating the other ports and switching the measured and terminated ports around to get all combinations.
You can directly take all the s-parameters from your three measurements. You'll have three sets of 4 parameters, that's 12 all in all. This gives you a good way of checking for consistency as you have two measurements for each of S11, S22 and S33. All other s-parameters are only in your measurement results once, so the only difficulty is not getting them mixed up, a good diagram should make that easy.
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Dear Genius,
I have faced a problem regarding the thickness of copper layer. I have designed a feed network (100 ohm) in RO3010 (permittivity 10.2) at 865 MHz. At first it was designed by 35 um thickness of copper. Due to manufacturing limitation, I had to change the thickness of copper. 
When I changed the thickness of copper layer then it showed completly different reflection loss.
At 865 MHz, the skin effect is 2.22 um . As far i know thar I have to take 3 times thicker than skin effect. But, at 18 um copper thickness, my result was not satisfactory at all.
It would be great if you can give me a suggestion about this issue
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Dear Denis Jaisson:
Thanks your advise to correct my mistake , thank you.
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I gotta admit I am rookie in this field. In my current working, I am encounter with some problems, I designed transmission line, grounded coplanar waveguide, return loss is not bad but insertion loss is not what I expected. Then I changed it into conductor backed coplanar waveguide, I designed the space between each grounding vias as quarter wavelength which I read from an article, both the return loss and insertion loss is fine. But due to there is too many grounding vias, the cycling time for manufacturing is a problem. As I changed them half wavelength, the insertion loss is even worse than grounded coplanar wave guide. I wanna ask that is there any solution for that?
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don't forget that conductor backed CPW has more complicated modes than simple cpw. And periodic vias provide band-gaps, which both can result in occasional mismatching
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While performing harmonic balance (HB) simulation by using oscport in ADS, an unwanted oscillation is detected prior to my desired frequency of oscillation. ADS detects the first one and gives HB simulation results of the unwanted oscillation, and no result is found for the actual oscillation. Although the active component is properly matched for enough gain and unstability at the desired frequency, this problem occurs while performing HB simulation. I am expecting some suggestions on this issue.
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Maybe "transient assisted Harmonic balance" in "initial guess" will help.
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I have 2 questions related to Microstrip Line characteristic impedance:
1) What would be the relation of characteristic impedance of a given microstrip line with frequency?
As effective permittivity increases with the frequency and gets closer to that of the substrate, according to formulae in Pozar Microwave Engg the characteristic impedance should decrease in my opinion. Could someone please clarify this?
An updated issue on the same is that according to a LineCalc tool in ADS, the Zc increases for a given line with increasing frequency which is exactly opposite to what I expected. Am I missing out on something here?
2) Why are there are 2 formulae for calculating Zc based on W/h greater or lesser than 1? (Reference Pozar Microwave Engg)
Does this mean that we can have 2 different possibilities to get say a 50 Ohm line on the same substrate for values of line width greater and lesser than that of the substrate respectively?
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Hi Arka,
within the frequency range where microstrips are used, with most materials the permittivity decreases but the loss increases with increasing frequency.
(I don't understand your statement "... and gets closer to that of the substrate, ...". The permittivity used in the formulae is that of the substrate. The only other permittivity involved in microstrips is that of air.)
Since with usual substrates and usual impedances of microstrips, the contribution of R and G (causing the loss) to the impedance is much smaller than that of C and L, with increasing frequency the impedance increases even with increasing loss.
Could you please name the page(s) where the 2 formulae are given? I cannot find them at the first look.
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Some of the books have always been used as a standard reference in that particular field. I am looking for such book on active components design theory and analysis; and that could have system level implementation/examples/models.
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Hello,
Practical Rf Circuit Design for Modern Wireless Systems, Volume II: Active Circuits ( by Rowan Gilmore (Author), Les Besser (Contributor) )
An Introduction To RF Circuit Design For Communication Systems 1st Edition
( Roger C. Palmer (Author) )
Thanks
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I have measured data of antenna radiation principal cuts in Theta(Angle) / Directivity form. Now I want to interpolate both the E and H plane cuts to make 3D radiation pattern. But I don't know how to arrange data in MATLAB & then perform interpolation. And can we do it in MATLAB's curve fitting tool ?
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Ah.. 3D reconsruction. Look at the figure below.
How many side lobes do you think are absent in your data?
Principal planes are taken because there are just two standard antenna orientations, and simple antennas have simple patterns.
And it is less complete without phase data relative to other components.
Reconstructing something that is absent is not correct for publishing, it can give people wrong impression on what was actually measured.
But for engineering demo, you can use any approach you like - trigonometric polar interpolation... Or I have an idea of taking inverse transforms to some 2D nearfield representation, filling that 2D image artistically(knowing your antenna peculiarities), then converting the image to 3D far-field again.
I never tried that so can not tell you details.
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im working on linear polarization in ISM band , and cross polarization will associate with co-polarization as side effect ,so is there any specific level form x-pol in that band ?
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Dear Alaa Imran,
I believe your question is pertaining to acceptable level of cross polarization, or response of your linear polarization antenna to its cross polarized component. Ideally speaking a linearly polarized antenna should not response to its cross polar component. but in real life it all ways response to some extant. Now the ward i have use "some extant" is need to be specified. For all practical/acceptable purpose we take this as -17 to -20 dB. this cross polarization isolation requirement became hire or stringent if you are using polarization diversity or dual polarized antenna, for this type of application its acceptable value will be typically -25 dB or batter. At last I would like to remind that all above figure are subject to system acceptability. Thus response of an antenna is not restrain by its operation frequency but it depends on the applicable system requirement.
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What is the main difference between dual band and dual radio?
Let
A system equipped with:
Dual Band= 2.4 GHz and 5 GHz
Dual Radio=802.11 and 802.14.5
where 802.11 with 5GHz is deploy between air to air link
and 802.11 with 2.4 GHz between air to ground.
similarly some nodes are also connected through 802.15.4 with 2.4 GHz between air to air.
The above system is dual band dual radio
or triple band dual radio
or triple band triple radio?
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Dual band refers to a device which uses two different frequencies to communicate.
Dual radio refers to a device which uses two different protocols to communicate.
Maybe an illustration would help. A dual band device is like a person at a party who can move between two different rooms (different frequencies) to talk with other people, while a single band device would be limited to talking to people in only one room. On the other hand, a dual radio device can speak with people who speak in two different languages, while a single radio device can only speak one language.
A dual radio device is typically used as an intermediary between two different networks like 802.11 (like WiFi) and 802.15.4 (like many wireless sensors).
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Is there some additional functionality in a VNA over an impedance analyzer? 
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A major difference between VNA's and Impedance analyzers is that the VNA uses an impedance, normally 50 Ohms, that can be easily matched to a transmission line. That allows you to use cables and PCB fixtures that have matched lines, so that you don't have to worry about parasitic inductance and capacitance in your setup. The higher the frequency, the more this matters.
As others have said, you can convert S-parameters to impedances, but the reference resistance is always 50 Ohms. This means that impedances that are far from 50 Ohms will be measured with large errors.
An impedance analyzer can modify its reference resistance based on the required measurement. This improves the accuracy of the measurement, but it means that the cables and fixtures behave as parasitic elements.
Thus the VNA is best for high frequencies and the impedance analyzer is best for low frequencies. Typically impedance analyzers are used from DC to 10s of MHz, and impedance analyzers are use from MHz to 10s of GHz
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I have a GNSS RF chip. I should connect the RF pin to an antenna connector with a 50 ohm microstrip transmission line.
I calculated the RF track width and printed the PCB
Now I want to measure the track impedance to verify calculation and design.
Is there any measurement device for that?
*The frequency of RF signal is about 1.5GHz.
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Denis:
My understanding of the 'exam question' that Farid Hosseinzadeh has set us is:
Given the PCB with GNSS chip installed, what piece of test equipment should be connected to the input connector of the PCB in order to find the characteristic impedance of the track connecting the input connector to the chip?
The picture I have in my head is that the track is in the order of a few cm in length and I am additionally assuming that no modification of the PCB to facilitate the measurement would be welcome.
From the assumption about track length I was then thinking along the lines of section 9.2 in Keysight Technologies, 'Time Domain Analysis Using a Network Analyzer' http://literature.cdn.keysight.com/litweb/pdf/5989-5723EN.pdf, which is saying that the TDR NWA should be operated with wide frequency span to resolve down to disconuity separations in the cm region.
If you could provide details of the measurement you thinking of, which answers the requirement as stated in this post, without using a wideband test pulse or a wide frequency span NWA test signal, I will happily be educated.
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I am trying to design a rectangular waveguide (WR12) power divider/combiner to split/combine my signal and at the same time maintain a good isolation between the two fan-out legs.
In my simulation, I have tried a simple T junction with a septum in the middle, it works well as a fan-out and combiner but the isolation is poor.
Does anyone know any design tricks so I can achieve a good isolation while maintaining a good power dividing insertion loss? I can't use isolator structure in my design since my signal will go both way.
Thanks!
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Hi Smrity,
Thank you very much for your answer and the paper. The SIW paper is very interesting! I could use it for a fanout design in one of our boards.
Best regards,
Wei
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RF transparent materials are materials where RF fields can penetrate with no heating happen. So far, I know some like Teflon, PPL, PVC, and ABS. They are made of plastics and have almost 0 dielectric loss factor. Anybody can suggest and give opinion about this.
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Dear Mr Macana, In RF terminology I think you are referring to radomes. Which allow unrestricted RF energy while physically protecting antennas, especially radar and avionics equipment antennas. The most common type is made by application of special resins on E or S glass fabrics. The resins are combination of some of the materials mentioned by Mr Mulla. But they do have a frequency response, at higher frequencies attenuation tends to increase for basic fabric/resin radomes. For higher frequencies usually glass based materials are used. Besides attenuation and heating deviation in the path of energy flow is also a measure of transparency of the material.
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In general, the microwave oven employs 2.45 GHz and most microwave ovens have similar cavity. As I guess, the transmitting length isn't finite. However, how about valid distance of the conventional microwave? Some people said that radio waves expand out using the inverse square law, meaning that the strength is 1/(distance squared). Then, how much distance is valid to increase temperature of target if there is no door and just with waveguide? If there is any scholar equation or base data about it, I hope to know that. For example, using the governing equation concerning with energy transmition of microwave, quantitatively calculate them.
Furthermore, recent commercialized microwave ovens have a stirrer in the wave guide. The stirrer do a role of microwave diffusion as I know. But it may interrupt microwave transmission or decrease the energy for target. Isn't it?
Thanks
Dongkyu Lee
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Te inverse square law holds for any point source. For microwave ovens or any other kind of RF propagation, what you are interested in determining is the ph
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What is your idea on protein denaturation after microwave or radio frequency heating?
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Hello Macana..."The microwave radiation as such has no detrimental
effect on the protein quality". Proteins treated with ionizing radiation results in cleavage of large protein molecules into smaller ones. Some studies demonstrated both fragmentation and aggregation occurs.
In general, sulfur containing and aromatic acids are the most sensitive to irradiation (Oxidation of the sulfur of thiol (S–H) and disulfide (S–S) groups of amino acids). In aromatic and heterocyclic amino acids, hydroxylation of aromatic ring is the principal reaction.
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Hello everyone. Although it is well-known that near 30 dB gain should be dedicated to RF chain of LNA and mixer in an RF front-end, for sure the precise choice especially when designing a discrete system and to select the near-optimum components is strictly application dependent. what are the main considerations to choose this conversion gain? All answers are appreciated.
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One consideration for lna+mixer gain is maximum input power at the lna required by system design. A larger lna gain means a larger maximum output power that may lead to gain compression, am-am + am-pm distortions and spectrum regrowth (that affects margin against blocking signals). You can design for a larger lna P1dB, which typically requires more dc power. The same arguments apply to mixer gain. In summary, lna+mixer gain is determined after considering trade-offs against distortion and dc power.
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Aside from Iron in blood, what are the magnetic materials in human body?
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Although mostly about dielectric properties, the book
Dielectric and Electronic Properties of Biological Materials Hardcover –
by Ronald R. Pethig
has additional information.
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Is expanded steel metal a magnetic material? Can it shield RF electric field and magnetic field?
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Whether steel is magnetic or not is easily checked with some permanent magnet...
But magnetic shielding is of lesser concern unless you generate large magnetic fields. The shielding of electrical fields is more important. As steel usually has a rather low conductance, it is way from ideal regarding the shielding of electrical fields. Here, copper is the better choice.
As an example for the meager shielding properties of steel: I have some underground flat where the light wells are covered by steel gratings (grid roughly 25 x 25 mm on the one side, 5 x 50 mm on the other side. Although these grids are way smaller than the wavelength of the frequencies of mobile phones, mobile operation underground is possible (with a bit of additional attenuation compared to above ground operation). That much about the shielding "quality" of steel gratings.
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What is the maximum distance of the conductor to transfer voltage and current from other conductor?
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Theoretically, there is no maximum distance limit; however, the magnetic field decays to levels at which the mutual induction or coupling becomes very small to be considered. The corresponding value depends on quantities such as the value of the current flow. Therefore, there is no a specific general maximum distance.
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Hi everyone,
Can you share with me some thoughts on how I can accurately calculate the impedance of mesh grid?I have attached the picture of ideal structure I am interested in. Basically, if you lay a mesh on top of dielectric, how can you simulate surface or sheet resistance of the mesh?What software can I use to model this structure?Any publication/paper/book that I can refer to? The structure I am working with is more complicated, however, if I can figure out this, then it will be much easier to tackle my design effectively.
I appreciate all the inputs.
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you can use HFSS or CST studio for model above design.
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Is there any equation or mathematical expression to generate the radiation pattern polar plot of standard Horn antenna (say 25 dB, 20 dB)?
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Thanks Puran for showing the way :P
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Waves can move at a speed of light. However, I am not sure if waves can travel more than its wavelength considering it is an open space.
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Light certainly travels from the sun to earth which is much farther than one wavelength. In fact, light will not stop propagating until something stops it.
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I have designed a triband  MIMO antenna for which MEG is one of the important parameters. I have difficulty in evaluating the MEG of the designed structure. I have designed and optimized using IE3D 14 simulator.
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IE3D
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What could be the maximum distance that one can control a UAV from?
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I'd use commercial 3G-4G mobile phone networks in order to send and receive short communication lines that help upload discrete commands (eg. Speed, Altitude, Go to a preset waypoint, Cancel mission, Go back home....) and download basic status information. Wouldn't work for downloading real time imaging, but maybe acquiring some basic environmental information.
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I am working on RF rectifiers. Tell me which book is more suitable for RF rectifiers. Many research paper uses non linear diode model for more precise results. I am new in this field.So tell, from where to start?
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First you need choice the frequency operation and the power level range that you go make the energy harvesting. The impedance of diode change with the frequency and with the power level. Zero bias schottky detector diodes are a good choice and the impedance is provided in site of the manufacturer in a file in the format s1p. Best regards
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I am designing a rectifier at microwave frequencies. But I don't know the exact procedure to calculate Impedance of diode used in it. I also want to know that how to decide the microstrip line length and width between different lumped components.How to calculate load value.
Thanks
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sir, could you please tell me the specifications of SMA connector used in the designing of the antenna hardware.
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Female edge mounted SMA connector
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I discussed this effect  upto some extent in my manuscript I think, It must be taken care for every current mode device  
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Not sure what you are asking exactly. Possibly, transconductance bimodal effect.
Resistance R = V / I
Conductance is the reciprocal of resistance, or I / V.
Transconductance is a term used for active components, tubes, bipolar transistors, or field effect transistors.
gm = dI (plate or collector or drain current) / dV (grid or base or gate voltage)
This has a direct effect on the gain of this device. If a small change to the grid/base/gate voltage creates a comparatively larger change in the plate/collector/drain current, then that device has higher gain that the device in which less of an increased current is experienced.
Or perhaps you are asking about transconductance bimodal effect? This is the strange behavior of gm, in cases where the device is operating below the base or gate threshold voltage. So, when the device is expected to be switched off, you might notice bumps in collector or drain current, even though you are expecting essentially zero current. See attached article.
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There are various excellent literature's available that derive the power consumption model of a macrocell base station using number of sector, traffic load etc. as variables. But none of them considered the impact of antenna gain. This is surprising, as in practice antenna gain is common and varies with scenarios, BS types etc.
Why is the antenna gain not incorporated in the base station power models? If so, then how would I integrate it's impact on the existing models?
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Dear Sir,
Study the topic  Link budget (Power budget) in Digital Communication book written by John.G.Proakias
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Please recommend differential amplifier with sensitivity (as low as -40dBm) and Gain above 20dB. Gain bandwidth from Dc to 1MHz?
Thanks
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Naveed.
You can estimate sensitivity as equal to = 10×log10(kTB)+NF+C⁄N
C/N is the desired carrier to noise ratio. NF is the noise figure of the amplifier.
plug into your numbers and choose a suitable amp.
we have developed a LNA using discrete components with  a NF of 1.0 dB.
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Probing resonance of Dirac equation with complex momentum representation,in this PRL . How to get (4) by putting the wave function (3) into (2). Who can give the derivation process?
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Hi,
I do not have the time to go into the details of the derivation in the PRL. I can only make some suggestions: If you don't see the direct path to the result, go back to the original derivations using some text book/related reference, since maybe you are not sufficiently familiar with the general approachor general methods of mathematical physics. In the present case, maybe there is some general stuff related to spherical harmonics and/or spherical Bessel functions.To overcome such hindrances may perhaps need some effort, that will pay however, in the long run.
Another possibility is to ask the authors.
Good luck
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I am trying to design a planar to dielectric waveguide transition with a schematic as shown in the figure alongwith. Despite a good S11 at a particular frequency, the S21 is not that good. I would like to know how to find out the power radiated in CST for example to understand where the power is going. Note that I have simulated all lossy dielectrics as lossfree and used PEC for the microstrip patch, so I guess its either being radiated or going into higher modes. WOuld be very obliged to have your opinions on this.
Figure below: Port 1 is the input port for the Microstrip line feed and port 2 the output port above the waveguide.
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The power in port 2 is negative because it is going out.  The power in port 1 is positive because it is going in.  Add them together and you get the power that doesn't go out of a port.  93.7% of the incident power (this is for input at port 1) gets in.  6.3% is reflected - this is 12 dB return loss (S11).  57.5% of the incident power goes out of port 2.  This is 2.4 dB insertion loss (S21).  The remaining power is about 36.2%, some of which is radiated, some lost in materials and some as the error term (if it is still there).
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Which RF PIN diode part is suitable for re configurable antenna(Frequency band 1GHz to 6GHz).Please suggest a part number which is easily available and low cost.
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Sir,
This is for prototyping in the communication equipment.Yes of course for receiver handling small power.
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Can we derive any conclusion on RF performance of device by seeing the transconductance or drain saturation current (Idss).
More specifically this question is on HEMT performance determination.
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Thank Barrie, for the reply.
I have searched a lot then also I was unable to find the related references on this topic. So I have posted this query in the researchgate forum.
I think you will share some references on this, which will enhance my knowledge.
Thanks and Regards
Shubhankar Majumdar
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Hi,
I'm designing a simple, lumped element low-Mhz level (1-100Mhz) detector circuit. But, I have some problems.
Before designing this detector circuit, I'd worked a Ghz and Sub-Ghz level RF/Microwave Energy Transmission project and I thought "I can use same RF schottky diodes for this application". 
Unfortunately, I noticed the input impedance of HSMS/SMS series schottky diode are not suitable for impedance matching around 50 Mhz (1-100Mhz band). They can easily match around Ghz although. 
I need to choose appropriate schottky diode around 50Mhz.
Which diode more useful for this situation?
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Hello Tahir, yes, PBR941B should work well. At 100 MHz, you can do without any striplines, and just build the basic emitter circuit. So, one amplifier stage might fit onto about 0.5 x 0.5 inches of PCB.
I'm not sure about the prospect of a biased Schottky detector. I guess it depends partly on where the output signal goes (manually operated volt meter or scope, threshold comparator?), and where the noise floor is, of course.
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How to design/simulate a planar balun for a passive double balanced mixer MMIC?
I have been stumped by a passive double balanced mixer for quit a long time. Problems mainly encountered are:
1.      Space between microstrip lines (clearance) must be greater or equal than 5um (technology limit), however, lower insertion loss requires smaller space.
2.      However I modify the microstrip line width(W), space between MS lines(S), number of turns(N), or length of microstrip line segments(L) of the balun,  I can never achieve a balance output, i.e. , equal amplitude with 180-deg phase difference, and the insertion loss is much higher than .ideal 3dB(greater than 6dB).
3.      Mixer realized with that balun suffers from a big conversion loss (greater than 10 dB) and poor port-to-port isolation and spur rejection.
4.      Simulation results of the same balun model carried out with ADS and HFSS differs a lot, where HFSS yield much better results with lower insertion loss and phase unbalance.
Questions are:
1.      How to design/simulate a planar balun for a passive double balanced mixer MMIC?
2.      Why is there so much difference between ADS and HFSS simulation results?
3.      Which one yields a more reliable result, ADS or HFSS?
4.      Can anyone help me with this design?
Any suggestion or discussion is welcome. Thanks a lot!
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Hi Dear Huan Xu
I am in new year holiday in iran. unfortunatly the high speed internet is not availble. please wait for 15 days later. i will check it and if i can help you 
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I need to establish an underwater surveillance system. Issues regarding that lets us discuss.
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 I wondered if anyone has tried a laser communication through water.
If it is for getting data from a camera I expect this will be a point to point link (and receiver and transmitter are stationary)?
The fundamental problem as explained above is that water acts like a conductor which  in general can be modelled as a plasma. Hence it should follow the Drude model for a plasma. The advantage however is that it is a relatively poor conductor so the plasma frequency should not be as high as that of metals. The link below suggests the plasma frequency of seawater is around 300GHz.
At frequencies above this the water should behave as a dielectric and the absorption is due to other mechanisms (e.g. free carriers) which is less that that predicted by the plasma drude model. However in practice since water is the great solvent that it is contains many impurities and the absorption curve needs to be measured. 
Doing a quick search on the internet suggests there is a huge null in absorption around 500nm (greenish blue light). 
A quick test might be to just get a green/blue laser around 500nm and measure the absorption of a water sample using an optical power meter. If you can get this to work all you need is a light modulator and you will have more bandwidth than you need.
If you know the actual plasma frequency for the type of water you have (and if it stays constant) there are lots of other interesting things you can do to overcome the classic skin depth problem. However plasma frequency is difficult to measure and you may need equipment around the 300GHz range of frequencies.
Good luck with your experiment. 
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I want to combine both of antenna and rectifier on single unit to have just 1 output 
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CST can import the dxf or gerber files output by ADS.  Import the dxf file then manipulate the shape - thicken it and add to CST shape, then export as dxf or Gerber
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ThingMagic Reader M5e
Single antenna 
G2iL tags
10 dBm power conditions.
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This problem can be solved in two parallel ways:
- Antenna part (matching, directivity, ...)
- System part (signal processing)
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I have designed an antenna which is operating in certain range but the solution frequency is beyond that range...If I am changing the solution frequency in to that bandwidth range then the performance is not that much good as that of previous one. Kindly suggest me what to do ? I am using HFSS 14.0
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Dear Sameer Sir, 
Thank you for your response and clear clarification. How ever I would like to inform you that, I do understand the selection of frequency range, actually I took random value just to watch the response of the antenna and when I found this type of result, to clarify my doubts I shared this experience.
Thanking You.
Sounik Kiran
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why pulse modulation of repeller voltage (and consequently the output power) is required in reflex klystron  while working in microwave laboratory, when continuous power can be obtained at a single frequency (without modulation)?
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By pulse modulation of a large fraction of the repeller voltage you can change the mean microwave power  emitted whose frequency varies on a relatively wide range. However different microwave sources, e.g. magnetron, are more suitable for a such application. In a reflex klystron, a small modulation of the repeller voltage is more often employed to fix the emitted frequency to that of a microwave resonator by a phase locking loop technique. 
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RF-based wireless energy transfer is attracting increasingly attention from wireless communications community. Simultaneous information and power transfer is a hot topic right now. Traditional information transmission may suffer from transmit oscillator jitters, e.g. carrier offset. Has any one considered their impact on wireless energy transfer? Are there any related materials on this issue? Thank you.
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We have been doing several projects on this in the past. Yes, if you go with resonance based methods (although it is more efficient), it will be affected by carrier offsets. One method we were experimenting was to track the carrier and adapt the resonator to capture maximum power. The other method is to use multiband resonator circuits and caputure the energy. best of luck