How to measure ip3 of a polyphase filter by trans analysis?

[mendenz]

how to measure ip3

the filter has two differential input pairs respective as Ip, In and Qp,Qn;
The for inputs has same common voltage,but has different phase;
So how to measure the paramete ip3 by trans?
the filte has bandpass 1.3meg hz~ 2.7Meg hz;
How to bulid the testbench,and how to get the ip3 in cadence?
Thanks !

 

[rfsystem]

how to measure intermod

I assume that you have a complex differential input!

So each signal as test signal need to have a cosine on I-input and a sine on Q-input. There are two effects. The first is inband intermodulation. The second is out of band intermodulation.

I assume that the IF frequency is (1.3MHz+2.7MHz)/2=2MHz. To test the inband intermodulation the intermodulation product have to be within the band. So use a two tone test signal at 1.8MHz and 2.2MHz. So the intermod is at 1.4MHz and 2.6MHz. The two tones are both complex differential. So increase the amplitude and record the amplitude of the intermod. The intercept is the IIP3 of the inband intermod.

The second test uses also two tones but both are ouf of band. So use for instance 19MHz and 21MHz. So the out of band intermod is at the filter IF. So you measure the intercept similar to the first case but the first orderincreasing amplitude is only seen at the input. The higher frequency is filtered in practice more than the intermod is generated.

 

[mendenz]

iip3 tran simulation 방법

So increase the amplitude and record the amplitude of the intermod. The intercept is the IIP3 of the inband intermod.

Do you have a convenience method to increase the ampitude in one simulation process ?
and can you display the intercept in wavescan windows?
thanks very much!

 

[rfsystem]

Re: How to measure ip3 of a polyphase filter by trans analy

To automate I suggest to use multiple simulations with different amplitudes. Extract the intermod from FFT at specific frequencies. Depending on the simulator you can run a script controlled simulation and doing the extraction.