H - Electricity – 04 – B
Patent
H - Electricity
04
B
H04B 1/40 (2006.01) H04L 27/233 (2006.01)
Patent
CA 2065647
RD-20,184 TANGENTAL TYPE DIFFERENTIAL DETECTOR FOR PULSE SHAPED .pi./4 SHIFTED DIFFERENTIALLY ENCODED QUADRATURE PHASE SHIFT KEYING ABSTRACT A digital radio receiver for synchronization of radiowave transmissions for digital and analog FM signals in TDMA systems such as cellular telephones uses a tangent type differential detector that minimizes the bit error rate. The differential detector employs an A/D converter circuit that samples a received signal, a sorter circuit that selects a predetermined number of samples to be used in the decoding, a sample and phase adjustment circuit that allows for a carrier phase adjustment and sample timing adjustment, a divider circuit that eliminates the need for a conventional limiter by causing a ratio of amplitudes to be processed instead of absolute signal amplitudes, an inverse tangent circuit creates a decoded phase angle from the ratio, a delay circuit and a summer circuit that create a differential signal, a modulo-2.pi. correction circuit that corrects for wrap-around errors about the real axis, and a four-phase decoder circuit to decode the signal into a pair of bits. An adjustment circuit minimizes phase error between a reference sequence of symbols and the decoded symbols by simultaneously adjusting the sample timing and carrier phase adjustments. The differential detector can be modified to decode conventional analog FM radio broadcasts by processing more samples per symbol, deactivating the adjustment circuit, and the SPA circuit, and bypassing the four-phase decoder.
Chennakeshu Sandeep
Saulnier Gary Jude
Company General Electric
Craig Wilson And Company
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