SAW-based carrier recovery without phase ambiguity for 915 MHz BPSK wireless digital communications

A surface acoustic wave (SAW)-based nonlinear carrier recovery system for wireless digital communications employing a 915 MHz injection-locked SAW oscillator for demodulation of 2 Mb/s and 8 Mb/s binary phase shift keying (BPSK) input signals is described. The circuit does not permit the injection-locked SAW oscillator to follow the abrupt phase changes in the input BPSK signals, but assumes an output signal with a unique frequency signature that is dependent on the input phase transition. Measurements of the SAW oscillator phase noise are presented, together with receiver input and output spectra and waveforms. An indoor 915 MHz radio transmitter is used with this SAW-based carrier recovery circuit for measurements of bit-error-rate (BER) under fading and non-fading conditions. BERs of less than 4×10^-8 are obtained for 2 Mb/s and 8 Mb/s BPSK signals at 915 MHz, without differential encoding, using a digital transmission analyzer with 2¹⁵-1 pseudo-random code length