Method and system for characterizing phase dispersion in intermediate frequency channel of receiver

摘要

A system and method supply a test signal having a first tone at a first RF frequency and a second tone at a second RF frequency to a frequency converter; provide a local oscillator (LO) signal to the frequency converter, wherein an IF output signal of the frequency converter is supplied to an input of an intermediate frequency (IF) filter, in response to which the IF filter provides a filtered IF output signal; for each of N>1 different LO frequencies, measure the filtered IF output signal at a pair of IF frequencies corresponding to differences between the first and second RF frequencies and the LO frequency, where the measurements of the filtered IF output signal measure time-invariant phase; and ascertain N−1 values of phase dispersion D of the IF filter at N−1 corresponding IF frequencies from the N measurements of the filtered IF output signal at the N different LO frequencies.

主权项

1. A method, comprising:
generating a test signal having a first tone at a first radio frequency (RF) frequency and a second tone at a second RF frequency; using a local oscillator (LO) signal to convert the test signal to an intermediate frequency (IF) signal; filtering the IF signal with an IF filter to produce a filtered IF output signal; setting the LO signal to a first LO frequency; measuring the filtered IF output signal at first and second IF frequencies while the LO signal is set to the first LO frequency, wherein the first IF frequency is a difference between the second RF frequency and the first LO frequency, and the second IF frequency is a difference between the first RF frequency and the first LO frequency; setting the LO signal to a second LO frequency, wherein a frequency difference between the second LO frequency and the first LO frequency is equal to a frequency difference Δf between the second RF frequency and the first RF frequency of the test signal; measuring the filtered IF output signal at the second IF frequency and at a third IF frequency while the LO signal is set to the second LO frequency, wherein the third IF frequency is a difference between the first RF frequency and the second LO frequency; and ascertaining a value D of a phase dispersion of the IF filter at the second IF frequency from the measurements of the filtered IF output signal, where the measurements of the filtered IF output signal measure time-invariant phase.