The Advantest R3541B Modulation Accuracy Measurment is a companion unit designed for use with the R3265?R3271 Spectrum Analyzer family. The R3541B measures the modulation accuracy of pi/4 DQPSK digital modulation in JCT-Japanese Cordless Telephone systems. The R3541B consists of a down converter, high-speed digitizer, digital signal processor, and interface to the R3265/R3271.