The Wideband Test Modulator – Multirate (WTM-MR) generates QPSK, OQPSK, and AQPSK modulated signals on a 720 MHz carrier from low data rates to 320 Mb/s. It also generates BPSK at data rates up to 160 Mb/s. Serial ECL data and clock inputs are provided for OQPSK and QPSK operation and parallel ECL data and clock inputs are provided for BPSK and AQPSK operation. Eight different modulo four differential codes can be selected for QPSK operation. Modulo two differential coding is provided for OQPSK, AQPSK, and BPSK. Control and monitoring of selected differential code, modulation mode, and output level are available on the front panel and also through the remote interface.