Hello rakesh,

where is the problem you are facing......

Generally, you need to use three columns, the first is frequency, second is simulated s11 and the third one is measured s11......

Now, in excel->go to insert then click on scatter...... Then you will get plot....... Now, label it accordingly.......

You can use a program its name sigma plot for comparing simulated and measured s11.

Simply create plot of S11 in dB scale. Then as Anvesh suggested, make three columns in csv file format. First column of frequency, 2nd of simulated result and 3rd for Measured result. You can also use www.plot.ly website to plot both the results simultaneously in the same graph. Register on the website mentioned and upload the csv file and draw line plot.

Generally when you export the measured data, it saved in dB (if you specify of course the dB choice), then choose the dB scale plot and export the simulated data from your software. You can save both datas in separate files, and by using MATLAB you can use the function plot(x1,y1,x2,y2) to plot both graphs on dB plot