DESIGN OF A MICROWAVE MULTISINE SOURCE USING ALLPASS FUNCTIONS ESTIMATED IN THE RICHARDS DOMAIN

In this paper a low-crest-factor microwave multisine source is develop ed. This is a broadband, periodic signal with a low crest factor (peak factor to effective value ratio). The design method consists of gener ating a pulse with a broad spectrum, amplitude filtering to get the de sired power spectrum, and phase filtering for lowering the crest facto r. A new technique to realize microwave phase filters is described. Fi rst, the properties of a rational allpass function in the Richards var iable are examined. This enables us to estimate the coefficients using a nonlinear optimization technique. The function is realized with cou pled transmission line filters. Using this general technique, a microw ave multisine consisting of 20 components in the band [100 MHz, 2 GHz] is realized with a crest factor of 2.