Abstract: A trellis-based lock detector and method for digitally modulated signals are presented. A global survivor for consecutive time indexes is computed as a maximum cumulative branch metric corresponding to a given time index for consecutive branches of the trellis structure. The invention is based on a concept that for a noise signal entering the lock detector, in contrast to an informative signal, the probability of a long succession of true evaluations of a global survivor is very small. The latter allows for using data, representative of the number of consecutive true conditions for a global survivor over an averaging time, as an informative parameter for making a decision on the status of lock detection.

Abstract: Three receivers are presented for the general case of noncoherent detection of multi-h continuous phase modulation. All three receivers yield performance gains using multi-symbol observations. The first is an existing receiver which has previously been applied to PCM/FM and is now applied to the Advanced Range Telemetry Tier II waveform. The second and third receivers are presented for the first time in this paper. The existing noncoherent receiver is found to perform poorly (and with high complexity) for the Advanced Range Telemetry Tier II case. For single-symbol observations, the new receivers outperform conventional FM demodulation for both telemetry waveforms, and for multi-symbol observation lengths their performance approaches that of the optimal coherent receiver. The performance is evaluated using computer simulations. Receiver performance is also evaluated using a simple channel model with varying carrier phase.

Abstract: Two receivers are presented for the general case of noncoherent detection of multi-h continuous phase modulation. Both receivers yield performance gains using multi-symbol observations. The first is an existing receiver which has previously been applied to PCM/FM and is now applied to the Advanced Range Telemetry Tier II waveform. The second receiver is presented for the first time in this paper. The existing noncoherent receiver is found to perform poorly (and with high complexity) for the Advanced Range Telemetry Tier II case. For single-symbol observations, the new receiver outperforms conventional FM demodulation for both telemetry waveforms, and for multi-symbol observation lengths its performance approaches that of the optimal coherent receiver. The performance is evaluated using computer simulations. Receiver performance is also evaluated using a simple channel model with varying carrier phase. The traditional FM demodulator approach is found to outperform both receivers as channel conditions worsen.