Antennas and Propagation - Science topic

Several techniques can be employed to enhance the S11 (reflection coefficient) of a Vivaldi antenna to below -20 dB. These methods primarily focus on impedance matching and minimizing reflections at the feed point. Here are some effective approaches:

By implementing these techniques, one can effectively improve the S11 of a Vivaldi antenna to less than -20 dB, achieving better impedance matching and minimizing reflections.

There are two main methods to fit a distribution to a set of data in MATLAB:

1. Using the fitdist function

The fitdist function is the most versatile and commonly used method for fitting distributions to data in MATLAB. It takes two required arguments:

For example, to fit a normal distribution to the data vector x, you would use the following command:

Code snippet

pd = fitdist(x, 'normal');

content_copyUse code with caution. Learn more

The fitdist function returns a probability distribution object pd that contains the estimated parameters of the fitted distribution. You can use the pd object to evaluate the probability density function (PDF), cumulative distribution function (CDF), quantile function, and other properties of the distribution.

The Distribution Fitter app is a graphical user interface (GUI) that provides a convenient way to fit distributions to data in MATLAB. To use the Distribution Fitter app, follow these steps:

The Distribution Fitter app will display a variety of plots and statistics that can be used to assess the goodness of fit of the distribution.

Both the fitdist function and the Distribution Fitter app provide a number of additional options that you can use to customize the fitting process. For example, you can specify the fitting method (e.g., maximum likelihood, least squares), set confidence intervals, and plot the fitted distribution along with the data.

The best method for fitting a distribution to data in MATLAB depends on your specific needs. If you need more control over the fitting process, then the fitdist function is a good choice. However, if you are looking for a more user-friendly interface, then the Distribution Fitter app is a better option.

In reality CP does not exist. It is better to say multi-polarization. The easiest way to see if your antenna has CP in simulation is to check for the S11 and AR results around the resonant frequency. There should be two picks for S11 with your design freqquncy being at the middle. These two picks indicates the two E-fields. You can also see the angles between them from your AR generated file in CST or HFSS. Your AR should be close to 1 or 0dB. See the attachments below from my multi-polarized antenna.

In air the beams will not interact unless they are so high power as to cause srcing. They will form an interference pattern in space, which will be stationary if the two beams are coherent, but the two beams will pass through it unchanged.

In non-linear materials they will interact.

There will be side-lobes from both arrays that may point at the other array and that will mean they do pick up some of the other array's signal depending on the steering angle.

Thank you.

The attenuation coefficient, alpha is a function of frequency f.

alpha (f) means the attenuation coefficient in dB/m at frequency f.

Both the transfer functions are the same. The top function has the value alpha already substituted as 0.05 dB/km for 100 GHz.

Aamir Habib Would you know the average gain in each of the 2 layers when TM mode 3 - open loop spatial multiplexing - is used?

Dear Meenakshi

Please, see the following reference. It is a study about many wearable material parameters:

Dear Mridul Verma

I suggest you to go through the following articles:

1. https://arxiv.org/pdf/1806.04574.pdf

2. https://etd.ohiolink.edu/apexprod/rws_etd/send_file/send?accession=osu1274730653&disposition=inline

3. https://www.irjet.net/archives/V6/i3/IRJET-V6I31355.pdf

Kind Regards

The deviation between the experimental results and the simulation results may be attributed to:

- Idealized theoretical models of the antenna structures

- Tolerances in the dimensions and in the material properties

- stray electric and magnetic and electric fields.

- Errors associated with the measurements.

Best wishes

Bilawal ..

To answer your questions:

1) You want to excite the mode that you are interested in; typically this is done with a small section of unloaded waveguide that contacts the waveport -- this is what is trying to be communicated on your attached slide 3. I performed some similar simulations in my M.Sc. thesis, see Fig. 3.4 in particular (https://era.library.ualberta.ca/items/220b08a9-1b53-4dd0-8586-4119b891ed00/view/f362409f-9e22-471b-be49-0832d029f308/Barth_Stuart_-20E_201508_MSc.pdf) where I have small sections of parallel-plate waveguide interfacing with the linear cascade of unit cells.

2) You can still obtain accurate dispersion information through extraction of the transmission (e.g., S21) phase from a finite cascade of unit cells.

3) I'm not sure what exactly you're asking, but I feel I may have answered it already in my previous responses.

Bilawal .. A lot of good questions.

1) You're correct; if there's only one patch, the series gap capacitance of course does not exist. In this case, there is no "correct" number of unit cells -- you need a different model. While I've shown in some of my previous work that one unit cell can provide responses similar to those predicted by a periodic analysis, this is not always the case -- it depends on the structure. Two unit cells should give a response in reasonable agreement with the periodic circuit analysis -- though is there a reason you want to define 'N'? I would simply say there are two patches.

2) It's better to say that two unit cells do not sufficiently behave similarly to an infinite array. It sounds like your periodic simulation is correct. It's well understood that there will always be some deviation between the response of an infinite cascade, and a finite number of cells. I don't see a reason why you would want to augment your periodic analysis to match the finite case.

3) Are you talking about resonant cavity (Fabry-Perot) modes? These are simply the modes for which there are multiples of 180degrees existing across the length of your structure, or (180degrees/N)*n, where n is an integer. You can read these frequencies off of your dispersion diagram -- e.g., if there are three cells, the frequencies at which Bd = 60, 120, 180 degrees. Yes, these modes should always exist, although they may each have their own ease of excitation. Generally, we are not interested in all of these -- so only a few may be shown, yes.

Dear Meenakshi Kohli

as you well know the wavelength is inversely proportional to the frequency.

(lambda=c/f). So if you want a resonant dipole at higher frequencies, the size of the dipole should be smaller, proportionally to the formula described above.

In that case, making the dipole approximately 1.5 times shorter should give satisfactory results.

I hope that solved. If you have any other questions, do not hesitate to ask.

Best regards,

Miguell

The impedance of an antenna can be anything from a few ohms to very high. A properly designed antenna will match to the impedance of the driving source for optimum power transfer. The 50 ohm value of the port is arbitrary and can be set to any value desired. Cable impedances come in many different values, such as 50, 75 and 300 ohms. Sometimes a low value antenna impedance is desired such as 10 ohms when connected to a low impedance solid state circuit.

Hi,

You See Rotman Lens Antenna, it's the same exemple,

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.

For example:

I don't think so , you have to use a Matlab script to calculate it

Good question

Length of the Helical antenna gives its Axial Length, A= NS. Axial Length A=NS, value also gives the modes of operation.

The value of length of helix, NS can be selected based on the following conditions

1. A=NS must be much smaller than wavelength, Lamda of helical antenna. It gives maximum radiation along the axis of helix. (End-fire radiation)

2. Directivity is directly proportional to the axial length NS. for higher directivity number of turns in helix must be more.

Directivity, D= {(15NSC^2)/(lambda)^3}

3. Axial ratio (AR)= {1+(1/2N)}, Number of turns must be more to reduce axial ration.

4. HPBW and BWFN are inversely proportional to square root of axial length. Therefore for unidirectional radiation NS value must be more.

In general if number of turns is more then it gives high directivity and almost unidectional radiation.

Antennas at long wave (1500 m) are designed as you propose, because a 350 m monopole is very tall, so they use a shorter monopole (small capacitor) with a big inductor in a room at the bottom. See the bottom of this page: https://en.wikipedia.org/wiki/Antenna_tuner#AM_broadcast_transmitters

Coupling an antenna to a separate resonant circuit at a similar frequency is often done to increase its bandwidth, for instance in a slot-coupled patch. This is basically double-tuning, not what you suggest.

Please read my paper

Generation of any PDF from a Set of Equally Likely Random Variables

Also please read my work

A Good Way to Find a Model for Corona Effect

I hope you find a good answer.

Hello,

As I use CST, but you can simulate any antenna in receiving mode with far field source and excite your receiving model either lump port or wave port and then right click on Field overlays in Project manager and then click to edit source option and change the solved magnitude for 0 W in wave port case and for 0 V in lump port case for the excitation of receiving antenna. In this manner you can analyze your antenna in receiving mode.

Thanks,

Dear Meenakshi Kohli,

I suggest you read the attached articles and his references. I believe it will help you.

I think the the best array is which makes possible the the beam forming and the beam steering covering 360 azimuth angle. Also the arrangement must increase the number of users which means to make the number of beams as large as possible. So, one of the possible best array is the array at a cylindrical with uniform polygon cross section. In every side of the cylinder one puts a linear array of antennas.

Best wishes

I will not repeat the answer of my colleague Navid. I would like to add some conceptual comments which may be useful for the issue.

Which channel model is dominant depends on the transmission media. If the media is homogeneous the line of sight model is dominant. If the medium contains large obstacles such as building then lognormal channel model will prevail. If the medium is scattering rich it will be multipath dominant with Rayleigh fading is the most suitable model. In case of making a study one can study the effect of such propagation models on the system performance.

As far the variation of the channel model with time represented by resource element, depends on the time variation of the channel. Generally the channel can be considered consatnt during the correlation time which is dictated by the Doppler shift.

Best wishes

You can use active divider composed of emitter follower or source follower transistors connected in parallel. Every emitter follower has matching function to transform 50 ohm output resistance to 50 x16=800 ohm.

This will be a very wide band divider consisting of 16 emitter followers connected in parallel. The input will be capacitively coupled.

Best wishes

Graphene has both real and imaginary part in conductivity curve. The imaginary part is negative. I would recommend you to use CST microwave studio. CST has build in UI for defining Graphene material and you can get the Surface conductivity curve once you are done with defining Graphene Evandro Cesar Vilas Boas

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

In HFSS: right click on Results -> click Output Variables -> give a Name -> add the following in the Expression box -> click on Add

mag((mag((conjg(S(1,1))*S(1,2))+(conjg(S(2,1))*S(2,2))))/(((1-mag(S(1,1))^2-mag(S(2,1))^2)*(1-mag(S(2,2))^2-mag(S(1,2))^2))^(1/2))) After the simulation is complete... right click on Results -> go to Create Modal Solution Data Report -> Rectangular Plot -> click on Output Variables -> New Report.

Note: This formula using S-parameters is only valid for antennas with high efficiencies, i.e., very low loss resistance! For antennas with low radiation efficiencies one must rely on the formula involving radiation patterns.

I extracted metamamaterial paramters using this technique but its not giving me results as NRW method is giving...WIll the result be different

Hi Manjurul Ahsan Riheen , it looks like u have a problem in the basic design itself

I guess they are there so that the input port is well-defined, with a constant geometry for a few mesh cells, which wouldn't happen if round posts were used. I think that if there were no conducting edges to the aperture then the input mode would not correspond to the SIW mode and there would be a mismatch at the input.

You can have an antenna embedded in a metamaterial, or have the antenna on the surface of the metamaterial, or separated from the metamaterial. All these configurations, and others, are possible. Your metamaterial can be the antenna, with the feed being inside metamaterial. An example of this is a meta-material slab with infinite phase velocity which can be fed at any point to get uniform illumination over its surface.

Very useful question.

There are many issues should be clearly addressed and specific. Please clarify, sir.

u[p to 20 (i.e. 26 db) is rather easy.Higher values are possible but maybe not very stable in practice.It all depends on the setup (microwave or. optical ) and the transmission medium which itself may be depolarizing.

It means if we are getting gain of 3 dB , We can write 5.14 dBi .

both are equal with their respective antenna. 3 dB wrt Dipole and 5.14 dBi wrt isotropic antenna.

Please follow this paper....

They gave a procedure which is widely accepted.

They explained the way of obtaining RHCP and LHCP gain of an Circularly polarized antenna. i think it would clear all the doubts.

Of course YES.

Emad

Dear Atik,

Search the following Excel file for any journal you want to check if it has IF or not.

Regards,

If E and H are static, phase has no meaning. If it is an antenna, E and H will not be static because the antenna will be operating at some frequency. Now assuming the antenna is operating at some frequency, the far field is essentially just a plane wave in free space. All of the conclusions about E and H in the far field come from theory of waves instead of any sort of antenna specific theory. Because free space is isotropic and lossess, the E and H fields are perpendicular to each other and are in phase. If the wave is in a lossy medium, E and H will be out of phase, although usually the phase difference is very small. If the medium is anisotropic, E and H will not necessarily be perpendicular to each other, although they likely be very close to being perpendicular.

Dear Ekta and Sajeed,

a totally resistive input impedance is a good theoretical assumption but in practice it is very ideal.  In addition, in order to have the maximum power transfer from amplifier to antenna, the requirement is to have Z(input antenna) = Z*(output amplifier).

In my opinion (also considering the type and low complexity of the yagi design) the way to follows is to simulate the antenna and its changes by means of NEC Numerical Electromagnetic Code

 https://en.wikipedia.org/wiki/Numerical_Electromagnetics_Code

Regards,

Massimo

You can use PCAAD software to solve this problem.

In this software, you first go "wire" and analysis the unit dipole antenna. The go to the "array" and define  your problem.

Be success

Height of rad_box = lamda/4.....According to HFSS, lamda is the wavelength corresponding to solution freq. But,  I prefer to define lamda by lowest frequency (not, solution freq) and Height of rad_box = lamda (not, lamda/4)

Multiple-Input Multiple-Output (MIMO) is an antenna technology – Sometimes called smart antenna technology. MIMO uses multiple antennas to send multiple parallel signals (from transmitter). MIMO can be used to advance such applications as: Streaming video, music ,Video surveillance, Voice over Internet Protocol (VoIP), Video conferencing ,Interactive gaming, Mobile TV.

Please how can I know the radome parameter. Thanks

Hello Aju,

you find attached a useful document on the equivalent circuit. you can export your design from CST as dxf file.

B.regards

Carbon Fibre Reinforced Silicone Reflecting Surface is used for unfurlable reflector antennas.CFRS reflecting shell-membrane is composed of the two materials: triaxially woven carbon fiber fabric (TWF)  and room temperature cure silicone elastomer S 690.

Dear Hamza,

Please follow the link:

It is really useful and answer your question both theoretically and experimentally:http://homepages.spa.umn.edu/~sourabh/ngd.pdf

Best wishes

Hi,

Kindly follow these papers.

Thanks,

RTT is affected by packet length. I had some very surprising results while testing early WiMAX implementation. You should try ping with different packet lengths. There is an interplay between packets and packet scheduling on the air.

Hi Eesa,

Thank you for answering again. I have tried and it seems that it works, hopefully the results will be accurate.

thanks again.

Best

you can increase the  3dB  AR bandwidth and you can generate circular polarization with four linearly polarized antenna

Hi,

You should get both at the same frequencies. To have both at the same frequency fine tune any one dimension (length, width, feed position etc.) of the antenna. Also, try varying the slot dimensions to match the frequencies.

Aparna Murthy thanks! I have solved,there is a slight mistake in the In HFSS settings

I think that 0 dBm is the power measured at the input of the Tx antenna which must be highly directive and pointed toward Rx antenna. If this is the case, the equivalent isotropically radiated power (EIRP) is 50 dBm, therefore, the link budget is correct. The path loss is maybe higher than 40 dB, due to the cable losses and imperfect orientation of the Tx antenna toward Rx antenna. It seems that Tx antenna is very directive, with small half power beam width (HPBW).Therefore its effective gain can be smaller than 50 dB if the Tx antenna is not correctly pointed to Rx antenna.

I have been working on PIN diodes with Planar antennas as well,  and I use CST where we can use lumped components option and for different states of PIN diodes, we can select values of Resistance and Capacitance based on characteristics.

Natural resonance frequency, omega(o) = 1 / (LC)^(1/2)

But, PIN diode works as a Zener diode, so it will start during reverse bias, and in other half cycle, it will be off. so, you will have provide some biasing voltage for keeping it ON state always.

See this paper, It might be helpful for you.

Thanks,

thank you so much for your replies but i got higher voltage (50V) with using instrumentation amplifier.

Is it possible to design MIMO  cube antenna with meta materials?

The shown dependence of the antenna reactance points out that your antenna is equivalent to  a series resonance circuit that has a resonance at about 9.6 GHz. If you want to broaden the bandwidth using matching circuit., this is possible by adding a parallel resonance circuit . By adding such matching parallel resonance one realize three resonance frequencies one of them is the original one of the antenna and two others which are displaced by an appreciable amount of frequency deviation around the the original resonance frequency.

Also the real part will be transformed to an other value. This method of broad band matching is treated in full details in the paper at the link:http://upcommons.upc.edu/bitstream/handle/2117/20022/05504933.pdf

Best wishes

I understand your problem, and I must say, driven modal is better than driven terminal. Driven terminal is used, for the modal S-matrix solution computed  is expressed in

terms of the incident and reflected powers of the waveguide modes. This description does not lend itself to problems where several different quasitransverse electromagnetic (TEM) modes can propagate simultaneously. For structures like coupled transmission lines or connectors, which support multiple, quasi-TEM modes of propagation, it is often desirable to compute the Terminal S-Parameters.

So, basically, we define these two different solver as,

S-parameters

Y-parameters

Z-parameters

VSWR

Gamma (complex propagation constant)

Port Zo

S-parameters

Y-parameters

Z-parameters

VSWR

Power (at port)

Voltage Transform matrix (T)

Terminal Port Zo

Thanks,

Thank you, Ms. Murthy :) I tried to see if I can add the radio inside the drone so the user can talk to the third party in a distance, and we are trying to install the fpv also. :) drone is flying just using the controller haha..

Hi,

May be too late. You can check "Travelling Wave Mechanism and Novel Analysis of the Planar Archimedean Spiral Antenna in Free Space" of Teng-Kai Chen

In general, the input impedance of 200 ohms starts and goes to 0 ohms (short circuit) at the center of the patch at a given frequency.

Thus, vary the depth of a micro-line to find the 50 ohms which should be between 1/6 of the total length of the patch.

Dear Ankit,

You can estimate your reflection coefficient if you know the dielectric constant epsilon of the material and the permeability mu of the material such that you can calculate the wave impedance of the material Zm= sqr of mu/epsilon. Since Za the air characteristic impedance, then the reflection coefficient rm= Zm-Za/Zm+Za. You can then compare the measured S21 with reflection coefficient. This is one side pf the problem.

The other side, in order to be a measure of the reflection coefficient i think one has to satisfy some conditions:

The antennas must be identical

They have to make the same angle with the surface plane of the material

The antennas must be matched to the impedance of the network analyser .

In this way the emanating  waves from the analyser will be only reflected from the surface of the dielectric material.

I suspect that this value is less than the reflection coefficient and merely a some received power.

Best wishes

Hi Rama,

Your antenna has to radiate with circular polarization.

If you are able to excite two orthogonal polarization using two different ports, then you just need a phase shift of 90degree between these two ports to obtain a circularly polarized field. With four ports the phase shift of 90 degree is between two adjacent ports in a circle. Depending in the sign of this phase shift when you turn, the circular polarization will be left handed or right handed.

To see the result you can plot the circularly polarized field/gain or the axial ratio.

I hope this can help.

Hi Mohan, You can apply a linear phase shift between array element in the linear array.

If the distance between elements is d and the tilt angle that you want is theta (theta=0 is for no tilt), apply a phase shift of phi=k0dsin(theta) where k0 is the free space wave number. For example for 8 elements the phases for each sources would be: 0, phi, 2phi, 3phi, 4phi, 5phi, 6phi, 7phi

Dear Tashin,

The following paper focuses on the design of dual- and tripleband filters by employing the coupling matrix and the optimization of its entries. One of the major advantages of this approach is that topologies and certain coupling elements can be controlled from the onset. The basic design steps are shown here at the example of a triple-band filter with six resonators and four transmission zeros, each two of which are located between adjacent passbands. The individual passbands are centered at 2.65, 3, and 3.35 GHz, and more than 50-MHz bandwidth is to be retained in each of the bands. The conclusions emerged from this paper is that the coupling-matrix design procedure for dual- and triplepassband filters presents a viable alternative to current multiband filter design techniques. The method is flexible, not restricted to certain filter types or topologies, and is capable of including higher order mode effects. The coupling scheme and limitations for the coupling coefficients can be enforced during the design. The feasibility of this technique is demonstrated for filter configurations in microstrip and waveguide technology. The designs are verified by measurements and a number of different full-wave codes.

To view the full publication, please use the following link:

Hoping this will be helpful,

Rafik

Thank you for your reply which is helpful for me to my work.

Maybe something like that

Regards,

Joachim

The external Q is the ratio between the energy stored in the resonator, and the energy lost in one radian (period over two pi) to the coupled circuits.  If you have two coupled circuits (an input and an output) then there will be two external Q s, which can be combined as 1/Qe1+1/Qe2=1/Qetot.  In an undercoupled circuit the plot over the frequency band of the resonance on a Smith chart will not go round the centre, whereas for an overcoupled circuit the plot will go round the centre.  This is to do with whether the resonator resistance or conductance is greater or less than the characteristic impedance of the transmission line coupled to it - the place where the plot crosses the real axis is the normalised resistance or conductance of the resonator.  Which of these you need to use depends on whether your resonator looks like a series or parallel resonance, i.e. whether it is open circuit (right hand side of Smith chart) or short circuit (left hand side of Smith chart) a long way from resonance.

First of all, you need to have some literature about the function of the rectifier and its different configurations. once it is clear, you may start designing the schematic circuit that consists of the lumped components(diodes, capacitors, resistors) using ADS software. After obtaining the desired response of the schematic circuit, you can go a head for microstrip transformation, then to the layout stage where your design will be  ready for fabrication process... hope it helps