Continuous phase modulation

About: Continuous phase modulation is a research topic. Over the lifetime, 3199 publications have been published within this topic receiving 37245 citations. The topic is also known as: CPM.

Phase recovery from a single interferogram with closed fringes by phase unwrapping.

Abstract: We describe a new algorithm for phase determination from a single interferogram with closed fringes based on an unwrapping procedure. Here we use bandpass filtering in the Fourier domain, obtaining two wrapped phases with sign changes corresponding to the orientation of the applied filters. An unwrapping scheme that corrects the sign ambiguities by comparing the local derivatives is then proposed. This can be done, assuming that the phase derivatives do not change abruptly among adjacent areas as occurs with smooth continuous phase maps. The proposed algorithm works fast and is robust against noise, as demonstrated in experimental and simulated data.

Decision-Directed Symbol Timing Recovery for SOQPSK

Abstract: Shaped-offset quadrature phase shift keying (SOQPSK) is a highly bandwidth efficient modulation technique used widely in military and aeronautical telemetry standards. It can be classified as a form of continuous phase modulation (CPM), but its major distinction from other CPMs is that it has a constrained (correlated) ternary data alphabet. CPM-based detection models for SOQPSK have been developed only recently. While these detectors offer an appreciable performance gain over current detection schemes, one roadblock standing in the way of their being adopted is the lack of a CPM-based symbol timing recovery scheme that will work with SOQPSK. We show how an existing CPM-based timing error detector (TED) can be adapted to the unique characteristics of SOQPSK. The TED is formulated for a coherent detector but can be extended to the noncoherent case. We apply this timing recovery method to the versions of SOQPSK used in military (MIL-STD SOQPSK) and telemetry group (SOQPSK-TG) standards. We derive the theoretical performance limits on the accuracy of timing recovery for SOQPSK, as given by the modified Cramer-Rao bound (MCRB), and show that the proposed decision-directed TED (DD-TED) performs close to these bounds in computer simulations and is free of false-lock points. We also show that the proposed scheme outperforms a non-data-aided TED (NDA-TED) that was recently developed for SOQPSK. These results show that the proposed scheme has great promise in a wide range of applications due to its low complexity, strong performance, and lack of false-lock points.

Noncoherent demodulation of continuous phase modulated signals using Extended Kalman Filtering

Abstract: The paper addresses the problem of demodulating Continuous Phase Modulation (CPM) signals embedded in Gaussian noise. The paper introduces a description of CPM signals by a state-space model. Based on this model, a noncoherent demodulation method of CPM signals, that uses an Extended Kalman Filter (EKF), was developed. The performances of the demodulation method were tested on two types of CPM modulated signals, embedded in noise: Minimum Shift Keying (MSK) and Gaussian Minimum Shift Keying (GMSK). The results, obtained from simulations performed in MATLAB, leaded to the conclusion that, for moderately low Signal to Noise Ratios (SNR), the EKF algorithm provides satisfactorily even good results in noncoherent demodulation of CPM signals.

Coded continuous phase modulation with low-complexity noncoherent reception

Abstract: Coded continuous phase modulation based on a feedback-free modulator with noncoherent detection is discussed. Low-complexity receiver processing is achieved by using only two or three linear filters for demodulation and applying noncoherent sequence estimation with reduced-state Viterbi decoding and simple branch metric calculation. Overall, the proposed noncoherent receiver provides significant advantages over previously presented approaches.

System and method for power line communication

Abstract: A communication system for a power line is described. A transmission system of the communication system divides the time axis into a number of time slots synchronized such that one time slot can start about a zero crossing of the power line signal. These time slots are referred to as channels and are numbered from 1 to n. A modulation method is described to is narrow band continuous phase FSK, where a number m of modulating frequencies are used, arranged such that an integral number of full cycles fit into each channel time slot for all m frequencies. The system transmits during only a subset of the available time slots (channels) concentrated near the zero crossing of the power line waveform where the noise is typically minimal.