Improved characterization of high speed continuous-time ΔΣ modulators using a duobinary test interface

Characterizing wide band continuous-time ΔΣ modulators is a challenge due to the high data rate at the output of the modulator. We propose the use of a duobinary test interface to extend the frequency range over which reliable laboratory measurements become possible. We show that using such an interface effectively randomizes the modulator output data and reduces high frequency content, thereby reducing the bandwidth demands made on the test equipment. Experimental results from a single-bit CTDSM operating at 4.4 GHz are given, demonstrating the efficacy of the technique.