[SOLVED] Calculation and plot the group delay (ns) for a UWB planar microwave filter by MATLAB

I want to calculate and plot the group delay (ns) vs. frequency (GHz) for a UWB planar microwave filter by using the MATLAB.

Is it possible to calculate the group delay of UWB microwave filter in MATLAB? If possible please help me in this regard and send me the MATLAB code for this? If not, then tell me what are the other procedures to calculate and plot the group delay of UWB microwave filter?

Is it possible to plot the group delay by simulation using ANSOFT HFSS v9?

Please help me in this regard.

Hi,

Yes it is possible to plot Group Delay by Simulation in HFSS v12, i am not sur about v9 because i do not have it and neither worked on that version but i think it should be there. Go to Results-->Creat Modal Solution Report-->Rectangular Plot,A new window will pop up. In the Category field you will find 'Group Delay' option.

I have calculated and plotted Group Delay for antennas in Matlab and verified it via HFSS simulation. But i am not sure whether the same principle ll work in case microwave filter or not.

If you want me to explain antenna Group delay procedure both by HFSS n matlab, i can do it.

/SC

Hi,

Thanks for your reply regarding the group delay.

Yes, I want to know the group delay calculation in case of antennas. Please explain me how to calculate and plot the group delay in ANSOFT HFSS and also by MATLAB.

If you send me the MATLAB code for calculation and plot of group delay in case of antennas I shall be grateful to you.

With best wishes

JRP

In HFSS:
Simulate 2 identical antennas in HFSS by placing them apart from each other by some distance(distance bw antennas doesnt effect Group Delay), and see the Group Delay plot as i have told in my post above. 'OR' plot the S21 plot and extract S21 vlaus from HFSS and use Matlab to see the Group Delay by using Group Delay equation which you can find in any EMT book or just google it.

IN Real:
Place the actual antennas (separated by same distance as you have used in HFSS) face to face in Real and connect both of them to VNA. Extract the S21 data from VNA and plot Group Delay on basis of it using Matlab.

This way you can compare your simulated and actual Group delay results.

I have done it long time ago, do not have the code with me anymore. But if you struggle doing it, do msg here with your data files and i will do it for you.

Hope this helps.

/SC

Hi,

Thanks for replying to my quarries. You wrote that “after extracting S21 vlaus from HFSS and using MATLAB to one can draw the Group Delay graph by using Group Delay equation”.

So, I am struggling in doing so by using the MATLAB program. I am attaching the measured |S21| data in "s21notch.txt" format of an UWB notch antenna extracted from VNA. So, please by using the measured |S21| data and following the group delay equation of any EMT book, please draw the group delay graph by using MATLAB and please send me the MATLAB code to me.

With best wishes

JRP

What are the two columns? Is one mag[s21] and the other phase[s21]? The values look weird.

To compute group delay, you just need to compute T = delta phase/delta frequency. I believe you want radians and Hertz if you want seconds as the output units.

The First column is Frequency i believe and second is magnitude of S21 which is not good enough to get GD. To measure GD you do not need magnitude of S21. Here is the equation of GD for you

GD = dphi/dw where phi=phase and w= frequency

In order to get phase of S21, calculate complete (Real+imaginary) form of S21 and then use above equation to plot it against frequency.

/SC

Jyoti,

You have uploaded the appropriate Data for the Group Delay. have you solved it yourself ?

Hi,

I was not in my place for a few days. Now I have returned back. While leaving I was attached the “s21notch.txt” hurriedly. I have not processed the .txt file properly. Now I have processed the “s21notch.txt” properly. The first column contains the frequency (GHz) and the second column contains the S21 (dB), which are written on the top of the column in the .txt file itself.

In your earlier mail you have written that (sweetchoto) “after extracting S21 values from HFSS and using MATLAB to one can draw the Group Delay graph by using Group Delay equation”.

So, I am still struggling in doing so by using the MATLAB program. I am attaching the measured |S21| data in "s21notch.txt" format of an UWB notch antenna extracted from VNA. So, please by using the measured |S21| data and following the group delay equation of any EMT book, please draw the group delay graph by using MATLAB and please send me the MATLAB code to me.

With best wishes

JRP

Jyotio,

I have plotted the GD from the Data you have provided. you can see the plot in the attachment. I am not sure what is the second column? is it the magnitude or phase of S21??? It should be phase of S21. Anyways i plotted it using the data you have provided and you can see the result. I do not know what is the impedance bandwidth of your antenna because GD plot doesnt seem quite good and it is fluctuating alot. Maybe it is due to the fact that you have not collected enough data points in the Frequency range. If you are sure that 2nd column in your provided file is Phase of S21 then i am sure this is the Group Delay response of your antenna.
/SC

Hi guys, don't we need to remove the delay caused by free space separation between the two antennas? And also the delay by cables connected to the two antennas?

hi CNm,
The distance between the antennas has no effect on the Group Delay and before doing the measurements with the help of VNA,you calibrate the VNA along with the cables so you do not have to worry about the cable effects, it doesnt effect the result that much.

/SC

sweetchoto said:

hi CNm,
The distance between the antennas has no effect on the Group Delay and before doing the measurements with the help of VNA,you calibrate the VNA along with the cables so you do not have to worry about the cable effects, it doesnt effect the result that much.

/SC

Click to expand...

If I understand you correctly, you are using two identical antennas, and measure the total delay. Then each antenna's delay=total delay/2.

Did you calibrate out the free space delay between the two antennas? If not, the delay has to be removed during the calculation, so each antenna's delay=(total delay-free space separation delay)/2.

In free space, the wave has 1nS delay per foot roughly.

The two antennas have to be in the far field of each other. Depending on the frequency band selected, this spacing between the two could be far away, which is a lot of nS of delay that cannot be ignored, did I miss something?

Dear sweetchoto,

Thanks for sending the group delay graph generated from the |S21| data which I had provided to you. The second column of the “s21notch.txt” contains the magnitude of the |S21| parameter in dB.

The S21 data which I have provided to you belongs to a UWB notch antenna whose return loss band extends from 3.1 GHz to 10.6 GHz, which is the band for UWB operation, which you might know. This UWB antenna has a notch band from 5 GHz to 6 GHz, to eliminate the potential interference with the WLAN band (5 GHz to 6 GHz). That’s why the S21 graph has a dip at around 5 GHz to 6 GHz and you can see a huge non uniformity in the group delay graph at around 5 GHz to 6 GHz which you have generated and send to me.

Though the second column of S21 data is the magnitudes (should be phase of S21), it provides the appropriate group delay graph which I exactly wanted and you have provided the exact graph to me.

Thanks for the co-operation and immense help.

Since I am not so good in MATLAB programming, if you kindly send me only portion the codes for the group delay expression in MATLAB program (how you wrote the group delay equation in MATLAB) (No need to send the whole MATLAB program), I shall be really grateful to you.

If you want that nobody should know the MATLAB code through this forum, you can mail me the codes in my e-mail :- jyoti07610204@gmail.com

With best wishes

Jyoti

Can Any body tell me how can we calculate the distance for Group delay. I mean at what distance i should keep the other antenna. is there any numerical formula. For example i want to check the group delay of UWB antenna for 2 to 10 GHz. now i want the maximum distance which should be at lower frequency (2 GHz) but how can i calculate it.
Thanks

Hi,
I have the S21 result from patch UWB antenna, but i am not able to get group delay by using MATLAB code. I am struggling with this issue from few days, but not able to resolve by myself. Please, help me to resolve this issue. If any one have MATLAB code for this, than please share it.