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Analysis of Intermodulation and Frequency Components

Suppose two tones are input to an amplifier. The tones are pure sinusoids with one at frequency 5 GHz and the other at frequency 5.02 GHz. Assume that the transfer characteristic of the amplifier is represented by Vout (please refer to the attachment for details).

List the output frequencies of all 3rd order (those near 15 GHz) and 4th order (those near 20 GHz) signals in ascending order of frequency. Try to be clever in your approach to this problem. It can be done by brute force but there is a better analytical way.


Solution Preview

Two sinusoids signals s1 & s2 are at f1 = 5 GHz, f2 = 5.02 GHz respectively.

Amplifier amplifies the combined input {s1 +s2} in a non linear way such that

Signal out s0 = ko + k1(s1+s2) + k2(s1+s2)power2 + k2(s1+s2)power3 + ...........k9(s1+s2)power9

This leads to 3rd order ...

Solution Summary

The mixing of signals and the resultant intermodulation of two pure sine wave signals at 5 and 5.02 GHz through an amplifier are considered. It is shown how to determine the output signals, their frequnecies, these being the 3rd order and 4th order products and harmonics.