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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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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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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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Hello All,
Coherer behavior, especially RF (Radio Frequency) coherer behavior, has defied explanation for more than 120 years. Many researchers have postulated that quantum tunneling may the mechanism by which small amounts of RF energy, applied to a coherer biased at a DC voltage difference much less than required to cause cohering, is the root cause of the conductivity increase that made coherers the first commercially viable RF detector. I believe that the first person to suggest quantum tunneling in one form or the other was responsible for coherer behavior was Angelika Maria Josefa Székely de Doba in 1924. Marconi employed coherers to detect very faint RF Morse code signals transmitted across the Atlantic Ocean.
Angelika Maria Josefa Székely de Doba ; Über die Art des Elektrizitätsüberganges zwischen Metallen, die sich lose berühren [On the Types of Electrical Behavior between Metals in loose Contact]; Zeitschrift für Physik; Vol. 22; February-March 1924; pp. 51-69.
Regards,
Tom Cuff
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I can understand that we need a strong nonlinearity in order to get a Rf demodulation (like a normal diode) but I do not see the need for tunneling effects.They may be there as well but I would say are not required.
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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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I’m looking for information or papers on the following:
The utilisation of RF technology in the human hand.
The utilisation of RF technology in manufacturing applications.
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Sadanand Pandey
thank you.
Im looking for conference or journal papers if anyone has any?
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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 am thinking of RF technology, will it work for me?
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As far as distance (range), Wi-Fi (802.11_) is a LAN (local area network) technology, so without some fancy RF tinkering like a number of college students have demonstrated in the past, range is limited to local areas; a room or two or maybe a few hundred feet line-of-sight. Less for the type of modules I described.
There are long range point-to-point communication modules from companies like Ubiquity that operate in the unlicensed ISM bands, some of which are based on modified 802.11 radios.
From there, you can look at various licensed network schemes including LoRa or the various cellular protocols. Again, all of these are more significant and costly undertakings.
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Hello,
I am a graduate student woking with Radiofrequency plasmas for chemical reactions and materials synthesis. I'd be extremely grateful if you can recommend me some literature or publications which can help me understand the selection of configuration and range of impedance for the matching network. Is there a way to measure the impedance of a chamber?
My reactor is Inductively Coupled Plasma using external RF coils and a quartz tube (1 inch) passing through the center of it. I'm trying to strike plasma in a 1/4 in OD tube but am not successful with it.
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Optimal plasma core diameter in ICP depends first of all on a frequency of electromagnetic field in the coil. Generally electromagnetic energy in the ICP is storing and oscillating in the output RF circuit including output coil. A part of the energy emitted by the coil as oscillating electric and magnetic field is partially reflecting back to the circuit from the plasma inside the coil and partially is absorbed by the plasma. The thickness of the energy deposition layer in plasma is determined by a thickness of current layer governed by skin-effect in plasma. The diameter of the output coil is generally designed to be about several times of skin-layer thickness. This diameter is treated to be optimal for ICP plasma stability. Thus the higher is frequency, the smaller is the coil and plasma diameter.
Some basics on the ICP plasma and bibliogrphy may be found in Plasma Chemistry by Alexander Fridman, Cambridge University Press, 2008.
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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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For simulating a dual-polarized transition, a trial with a basic patch structure with 2 orthogonal microstrip line (MSL) feeds is used to excite orthogonal modes in a Circular Dielectric Waveguide above. As both the MSL ports should act as input ports, I have tried initially with sequential excitation which gives the results (S Parameters etc) for each excitation individually.
My queries in this context are:
1) In order to know the transmission to the Waveguide port on top due to excitation of both the input ports is simultaneous excitation the only way out? (Are the results of transmission characteristics of simultaneous excitation a sum of those due to individual sequential ones)
2) Having tried out simultaneous excitation too 'F Parameter' term is obtained. Could the precise meaning of they precisely mean be clarified?
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Hi Arka Halder
For simultaneous port excitation in CST, you must use the following procedure.
1. Go to time domain solver setting.
2. Select "selection" in "Source type"
3. Click on "Excitation List...".
4. Select your desire ports.
5. Active "Active" option.
If something went wrong, let me know.
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I am reading about the capacitively coupled plasma but could not get any details explanation about the stochastic heating. Can I please get some elaboration of this method and hopefully if there are any good source materials. Thank you in advance.
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There are two main heating mechanisms for electrons in RF capacitive
discharges: ohmic heating and stochastic heating. Plasma resistivity
due to electron-neutral collisions leads to ohmic heating while momentum
transfer from high voltage moving sheaths leads to stochastic
heating. Thus, ohmic heating is mainly a bulk phenomena while
stochastic heating is localized in the sheaths areas.
Electrons absorb energy from the electric field E through the collisions, called Ohmic heating (OH).
There is also momentum transfer from high voltage sheaths that leads to stochastic heating (SH) at the sheath edge closer to the electrodes or chamber wall.
You may refer literature for more clarity:
M. A. Lieberman and A. J. Lichtenberg, “Principles of Plasma Discharges and Materials Processing”, Wiley, New York (1994)
Good luck!
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I'm researching a concept and need some help. Let's say we have two objects. While the two objects are essentially the same, they each have a slightly different resonate frequency. Is it possible to broadcast a signal that would have an effect on one of the objects with negligible effect on the other?
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Your application is related to wireless RF, so definitely  receiving objects contain antennas.  
In your question you mentioned that the objects are having a slight variation in resonant frequency.
So. both the antennas will receive the signals (It is difficult to design such a slight varying BW antennas) which you are broadcasting depends upon the bandwidth of the each antenna (strong and weak signals).
If you want to eliminate the effect of a signal on other object (which is not supposed to receive), make use of filters. 
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I'm doing recognition of activities from RF-signals which is device-free and I'm using USRP device.So what kind of activities do you think is suitable to measure with,because during the experiments they are many interference and noises.
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Could you be a bit more specific on the activities and how the measurements relate to the stress recognition ?
I ask this, because it is a bit complicated to answer your question without some further insight.
kind regards,
Marian
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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 would appreciate any help or insight or suggestions or ideas regarding simulating a WDCN based on 60 GHz wireless RF technology in MATLAB?
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Hi
You can use simulink for the same.
Thank you.
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Hello.
As far as I know, the coaxial cable has zero sum of current (sum of current between central conductor and outer shield conductor) thus inductance and radiation from the cable is very low.
However, I guess this current cancellation is only strictly true for DC. For AC, maybe phase of the signal has to be considered? Is this really true for AC such that current between two conductors are always in out-of-phase in principle? (I know real world is different from theory so I'm asking some comments rather involving principle first)
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Theory is an attempt at modeling the real world.
If the description is more accurate, the model is more complicated. (for the interviewer)
It is clear that all current must return to the signal source.
It's just such ways.
For lossless connection to a single coax the situation is simple.(see Mr.Zekry)
If it is connected multiple cables, an impedance model (parasitic coupling) is more complicated.
Always, however, they must pay KCL - for a closed (defined) space!
If the connection is not lossless, it can be part of the current "return through space".
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Do you know of any commercially/DIY available RF energy harvesting products besides those of Powercast?
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Hi Mr. Moullec,
In order to our RF energy harvesting experiments, these ICs (Linear Tech.) not suitable on Rf harvesting application because of their input impedance value. But, in application notes they are suitable option for other harvesting technology such as vibration, TEG and so on.
Perhaps, TI BQ255x series can be good option.
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I am a Physics person. I am stuck with this simple thing which could be very obvious. Please help me to resolve this issue.Cable Impedance of 50 ohm cable is always considered to be real in all calculations but the measurement of resistance by multimeter shows infinite which is obvious. Then, as we know that a lossless 50 ohm cable is modelled by many identical section which consists of series of inductance and parallel capacitance and the  impedance is given by square-root of (L/C). So, how this real impedance of 50 ohm ( if it is real it represents resistance) comes into picture and why we cannot measure it by multimeter? 
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if your coaxial cable were infinitely long and open at the end you would also measure 50 Ohm with a normal Ohmmeter...to mimic tis case you may terminate it with a real resistor (e.g. 50 Ohm) and you measure 50 ohm. But  when its open at the end and say 1 meter long you see at the normal ohmmeter the steady state situation for this case. If you use a fast Ohm meter with nanosecond resolution (i.e. TDR scope) then you really see in the first  few nanoseconds the char impedance (50 Ohm) and later to transition to infinity (if the cable is open)
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The concept of an "equivalent rounded obstacle" is used to account for radio propagation losses over various possible irregular terrain shapes, including
shapes which cannot easily be described geometrically.
I saw the previous paragraph in the attached paper, but I could not find any other useful document about this concept. Does anyone know more?
Also, I need a picture to see an example for replacing an irregular terrain with a rounded obstacle! I draw my imagination in the attached figures. Are they true?
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This ITU recommendation document may also be helpful.
Search for  FR-REC-P.526-7-200102-S!!MSW-E.doc
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I measure the power of RF ambient noise (radio noise) that is captured by the antenna with a sensitive receiver that has an true RMS detector. If the power of the ambient noise is only a few dB above the noise floor of the receiver, the measured power will be a combination of the ambient noise and the receiver noise. If the noise floor of the receiver is known, how can I calculate the true power of the ambient noise alone?
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I missed that you were measuring noise power with a noisy receiver. This is straightforward radiometry. Use the Y factor method.  Measure the output of the receiver with the input connected to a load at a known temperature. Measure the output of the receiver with the input connected to the load at a different known temperature (or to a calibrated noise source).  You can calculate the gain and noise temperature of the receiver.  (you may already have done this...)  
Now measure the output of the receiver with the unknown signal connected (whether it's noise or a sine wave or any waveform).  The added power is your unknown, scaled by the gain of the receiver to refer it to the input.  My previous answer tells you how to assess the uncertainty of the measurement.
There is a good description of this process in Kraus's book on Antennas, and in his book on radio astronomy.  Measuring the noise power of things beyond your antenna is what radio astronomy is all about.  
You could also look at the Deep Space Network literature, where they take truly obsessive care with measuring the system noise temperature.  http://descanso.jpl.nasa.gov would get you started, but that's probably overkill.
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Which techniques can I use to perform this? I hear using optical fiber can be useful but I don't have any details.
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The speed of light through coax or through fiber is approximately 2E8 meters/sec. Which means that if you add some length of fiber or coax to the transmit antenna feed, you will introduce delay. This has to be one of the simplest methods.
2E8 * 1E-6 = 200 meters of coiled fiber or coax, to delay the RF signal by 1 usec.
One reason for introducing delays like this might be to tune the transmit antennas in a single frequency network, I would think.
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We are working on designing a small research UAV system. However we are asking ourselves how to deal with the issues of doppler effect on our RF communications due to the motion of the vehicle.
What are the common techniques to deal with doppler in RF communications?
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PLL is usually implemented d in analog domain but digital locked loop also exist that do the same in discrete time domain. however the most useful techniques for your case would be frequency recovery technique in addition to clock and phase recovery. the book written by Mengali is great reference in synchronization technique.
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Minerals such as coal, porous coke, char, briquettes
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By now i am using the microvawe technique for drying. Is practically the most efficient method. the energy comsuption is less than 50% od thermal drying. is very effective where the thermal methos is not, for example in the latest steps, where the humidity is very low. The efficiency is very hign because in not humidity dependent, one drying step is used.
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The sample is a layered system where the lowere layer is a metal that act as an electric ground. The top layer acts as a dielectric. The stripline conductor should be attached on top of the upper layer independent of the sample growth process.
Thanks a lot for any comment!
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That's an interesting idea. I was thinking more of a lithographic process. But the sample is already grown by PLD, so one can maybe evaporate gold in the same setup.