A matched-filter differential detector for continuous phase modulation is proposed and simulated error probability for this detector is presented. The detector consists of a conventional differential detector operating with a delay, a bank of matched filters, and a Viterbi processor to perform sequence decision. The author shows that quaternary schemes outperform binary schemes, when the schemes are compared in a power-bandwidth tradeoff. Schemes that lose about 3.4 dB compared to coherently detected minimum shift keying (MSK) at 10/sup -3/ on a Gaussian channel, but with a bandwidth of about 0.6 times the MSK bandwidth, are presented. >