RF Propagation - Science topic

The impedance of microstrip is affected by fields above the top line, as well as several line-widths or substrate thicknesses each side, so you need to make your port big enough if the port impedance is to be the same as the impedance of the microstrip. A discrete port will not be a very good match to the microstrip you show, I think. A waveguide port with a port 3 times the height of the substrate and 6 times as wide as the line or the substrate thickness should get the right impedance. It doesn't take long to check. CST has the option in the simulation window to just calculate the port modes, so you can change the size and see what happens. The port modes are in 2D results and can be plotted. If the fields are significant near the open port edges then the port is too small.

Yes, there is a difference in accuracy between testing a four-port device with a four-port VNA and with a two-port VNA.

A four-port VNA can measure all four S-parameters of a four-port device directly, without any need for approximation or extrapolation. This provides the most accurate measurement of the device's performance.

A two-port VNA can only measure two S-parameters at a time. To measure all four S-parameters, the device must be connected to matched loads on the unused ports. This can introduce errors into the measurement, as the matched loads may not be perfect and the reflections from the unused ports may not be negligible.

In addition, the two-port renormalization technique, which can be used to calculate the missing S-parameters from the measured S-parameters, is not always accurate. The accuracy of the two-port renormalization technique depends on the accuracy of the measured S-parameters and the reflection coefficients of the matched loads.

As a result, the accuracy of testing a four-port device with a four-port VNA is generally better than the accuracy of testing a four-port device with a two-port VNA.

Here is a table summarizing the accuracy of the two methods:

If you need to measure the S-parameters of a four-port device with the highest possible accuracy, then you should use a four-port VNA. If you do not have a four-port VNA, then you can use a two-port VNA with matched loads, but be aware that the accuracy of the measurement will be less than ideal.

Dear Sohaib Bin Altaf Khattak ,

You can monitor your RSS of the accessed WIFI networks using the methods described in the site:https://www.lifewire.com/how-to-measure-your-wifi-signal-strength-818303

Best wishes

Ryan Kao Based on your attachments I assume you are procuring R&S instruments. If you look at section 2.4 in both the attachments, it lists the devices and options required to conduct the tests. [This is just one example from the documents.] Typically, such capablities are licensed software options that must be purchased with the instrument (or even a later purchase of license can enable the feature!).

It will be best to go through the instrument documents, which are quite tedious to navigate through; you may save some time by reaching out to the vendor application engineer (AE) who might be interacting with your department/ institute. Understanding the test environment system is key to correct test execution and measurement.

If you need some insight into RF measurements in general, you may want to check out my book "RF & μWave Measurements: For Design, Verification and Quality Control", which is available at select amazon marketplaces. However, it does not address your 3GPP specific question.

/rgds

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:

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

Dear Denis Jaisson:

Thanks your advise to correct my mistake , thank you.

Dear Sreenath,

The steps to plot RCS vs Frequency:

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.

Thanks Puran for showing the way :P

Do you have a specification to define wht "a good match" is? And do you have a loss specification for your matching network? 

The antenna has quite a sharp resonance, with an associated Q factor larger than 20. I very much doubt whether matching is possible with a lossless network to a reasonable VSWR spec over the full bandwidth. You could do better if you may also use lossy elements or materials, but that comes at a cost that may be unacceptable.

You could perhaps consider a friendlier antenna element, like maybe a sinuous antenna.

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. 

Hallo there,

RF modelling is quite a well researched topic in Comsol, Also, I believe the developed RF interface is strong. An appropriate starting point is to understand the underlining physics, the rest is just finding the correct parameter to represent the propagating material. My favorite book on the subject is "Microwave/RF Applicators and probes for material heating sensing and plasma generation" by "Mehrdad Mehdizadeh". The book was introduced brilliantly and I am sure it will help you as it did to me.

Concerning the RF modeling, i advise you to follow the Comsol Blog entries provided by Walter Frei, which are nicely and informatively written and include a lot of RF modeling.

Keep looking through the pages, you will reach RF modeling then.

Hope that helps. Happy holidays

thank you for your answer, you are absolutely right, but I want to model the channel by a deterministic model so it must apply the ray tracing method and add the model in Uniform Theory of Diffraction (UTD).

Can you help me?

However, there may be an extreme case, when scattering by a spherical particle into a certain partial mode is completely suppressed, so that the corersponding Mie coefficient becomes zero [see Ref below], which is of course purely imaginary. 

A simple way is to radiate strong carrier such that  LNA of enemy's receiver  is saturated and and hence does not amplify the FH signals. The requirement is high gain antenna and higher power amplifier.

Another method is to radiate noise in the entire FH band. This is complex and difficult to implement. 

Thank you for your help. 

So far I'm attempting to emulate the Doppler shift associated with satellites in LEO so I can see how different receivers will interoperate. So far I haven't found anyone else working on this. I was hoping others had started experimenting with similar equipment in field of study.

Self-bias ferrite is basically, concentrate signal density or change the polarisation. The permanent magnet is main source to have the effect.

For antenna, probably it can improve directivity or polarisation can be changed 

We done such investigation and publish results in paper of  W. E. Antciperov, O. V. Evseev, G. K. Mansurov, A. V. Ponikar "Variability of received signal strength value in IEEE 802.15.4 (ZigBee) sensor nets and its influence on inaccuracy of mobile objects positioning" (http://jre.cplire.ru/jre/jun11/index_e.html). Unfortunatly it is published in russian. Nevertheless, there are a lot of pictures and formulas, so anyone can easilly reconstruct the content.

Many thanks Mohamed, I am currently using Wireless Insite for RF Ray Tracing simulations in the publications below. It is a god software. However the problem with Wireless Insite is that it is not "open source" and does not give the full freedom in manipulating the RF environment dynamically . For example you can't interface directly between Matlab and Wireless Insite.

The critical frequency of the ionosphere is not a fixed value. It roughly varies with time of day, day of the year, and the 11-year long solar cycle. Short term variation is influence by many factors, of which the solar radiation and the earth magnetic field are the main drivers.

Solar flares may disturb the more usual arrangement of the ionosphere, and can be seen as anomalies in ionospheric radio wave propagation, sometimes even totally disrupting all ionospheric propagation.

The critical frequency of the F-layer is measured near real-time by ionosonde stations. Please take a look at them, they are very informative. The following link is from an ionosonde in Belgium, but there are several in your area as well:

Is your interest driven by radio wave propagation issues, or earth science interest?

For an estimate of the accuracy of the LR model in the broadcasting bands you can take a look here:

There are several cases where the LR model does not exactly predict field strength, at longer distances in the FM radio band (most probably due to ground reflection) and behind multiple hills oe mountains (due to multiple diffraction).

However, I cannot overemphasize that you should insist on the precision of your measurements !!!

1- Run a simulation and see what field strength you should expect

2-Then go to measure and move around a measurement point in order to avoid local variability effects.

3-For the last reason you should always choose slightly over-elevated measurement points with respect to local terrain.

4-Be very careful in using precision AND Accurately calibrated measurement antennas with the correct AF (Antenna Factor) !!!

5-The same applies for cables and connectors. DO NOT use adaptor connectors.

DO NOT use no name cables.

6-Re-calibrate antennas, cables yourself, if you have the necessary equipment.

I hope this might be helpful for you

1. Calculate the attenuation value of each point in a region and plot on an image (as coverage) with rgb values ​​are equivalent to the value of attenuation

2. Place the image as a layer overlay on google map at coordinates corresponding to then region.

3. If users click the image then convert the RGB pixel values ​​to the attenuation value

The great advantage of the Longley-Rice model is that by including digital elevation maps, the model is able to asses the received signal strenghth with good accuracy, including Fresnel zone clearance and diffraction effects.

Without the terrain info, the model will only provide the free space loss, which is rarely adequate in paractical applications.

See WNDW.net

Thanks a lot to all for answers

Hello,

I hope this will help:

%let us take circle of unit radius

R = 1;

t = linspace(0,2*pi,100);

x = R*sin(t);

y = R*cos(t);

%now create uniform mesh over square with some given cell size cs

cs = 0.01;

xm = linspace(-1,1,2/cs);

ym = linspace(-1,1,2/cs);

[X,Y] = meshgrid(xm,ym);

%check for points inside the circle

inside = (X.^2+Y.^2<R^2);

plot(x,y,'r',X(inside),Y(inside),'xb')

%the coordinates you are looking for are given in (X(inside),Y(inside))

Greetings

Piotr

Mauricio,

MATLAB can do it (quiver plot). However I recommend to you Tecplot. It is such an advanced tool for graphing that you can generate very elegant plots for any field (scalar or vector). I have personally used Tecplot before and will always do.

Dear Jai,

While going through the "Senseless" technology, I got to know that, cognitive wireless networks is the basic motivation for the design approach model of white space sensing. Please go through my reference below