p1db curve
what is the best way to fix up the extrapolation point to plot the IPN curves(say iip3).
usually we find the region having the slope 3 for the 3rd order intermodulation curve and taking the mid point of that we will fix the extrapolation point.
but unexpectedly, my 3rd order intermodulation curve is not having slope 3(it is varying between -5 and 2.5).
can any explain why this is so?
Start by checking linear relationship up to the 1 dB compression point, using a single carrier test. It shall look like the plot on page 1 in this document:
http://www.odyseus.nildram.co.uk/Sys.../Linearity.pdf
An explanation for your 3rd order intermodulation curve is not having slope 3 could be intermodulation between the two signal generators used for giving the two tone signal input. You should have a 10 dB attenuator at each signal generator's output in front of a high isolation power combiner.
What is the frequency separation between the two carriers?
thank you VSWR. the pdf u sent was very good.
i am attaching how my CP1 curve looks like.
it is linear till the 1 db compression point.
how to chose the extrapolation point for plotting the iip3?
the two input frequencies are seperated by 3MHz.
chacha
take care of what you are simulating.
If you look at left side of your plot, for a -80dBm input you got -190dBm(!) of output, so your circuit is an attenuator (-110 dB!) with poor linearity.
I think that you should correct your simulation parameters and/or results.
I hope it can help.
Mazz
yeah there is attenuation , is it a simulation of a mixer or what , and if it is a mixer , are u remeasuring the power of which harmonic the IF , or RF feed through
khouly
iam very sorry for that last attachment. this is the first time i am doing mixer design.
i was using 2 ports at the output. if i use a single port it is giving a different result.
this time its output power is -90dbm for a -80dbm rf input(taken at IF).
the conversion gain is 15db.
thank u....
dear chacha
how it is have a gain of 15 , and the input is -80 , and the output is -90 , this is attenuation , u need to get the gain the ouput should be -70 dbm
check ur simulation again
khouly