Amplitude flatness and phase linearity calibration for RF sources

摘要

An amplitude flatness and phase linearity calibration method for an RF source across a wide frequency bandwidth uses a simple square law diode detector and at least a pair of equal amplitude frequency tones. A baseband generator for the RF source generates the tones, which are applied in series to a correction filter and an up-converter to produce an output RF signal. The tones are stepped across a specified frequency bandwidth, and at each average frequency for the tones a magnitude and group delay is measured as well as a phase for the beat frequency between the tones. The resulting measurements are used to calibrate filter coefficients for the correction filter to assure amplitude flatness and phase linearity across the specified frequency bandwidth.

主权项

1. A method of calibrating an RF signal source, the RF source being of the type having a baseband signal generator, a correction filter and an up-converter coupled in series, for amplitude flatness and phase linearity of an RF signal output comprising the steps of:
generating from the baseband signal generator a plurality of equal amplitude frequency tones having a specified average frequency and specified frequency separations between the tones such that the equal amplitude frequency tones are non-harmonic with respect to each other; computing from the RF output signal a magnitude and group delay for the specified average frequency; computing a phase response for the specified frequency separations; stepping the specified average frequency from the baseband signal generator across a specified frequency bandwidth and repeating the generating and computing steps at each specified average frequency; and calculating filter coefficients for the correction filter from the magnitude and phase responses so that the RF signal output has amplitude flatness and phase linearity across the specified frequency bandwidth.