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.

Spread spectrum transmitter

Abstract: A technique for modulating and demodulating CPM spread spectrum signals and variations of CPM spread spectrum signals. A transmitter divides a signal data stream into a plurality of data streams (such as I and Q data streams), independently modulates the I and Q data streams using CPM or a related technique, and superposes the plurality of resultants for transmission. A receiver receives the superposed spread spectrum signal and simultaneously attempts to correlate for a plurality of chip sequences (such as I and Q chip sequences), and interleaves the correlated I and Q data streams into a unified signal data stream. In one embodiment, a spread spectrum transmitter comprises a plurality of lookup tables for storing spread spectrum code chip sequences, at least one preamble code chip sequence, and at least one fill code chip sequence. An output from each of the tables is provided to a selection circuit (e.g., a multiplexer) that selects, under control of a controller, chips from each of the tables to construct a unified chip sequence. The unified chip sequence is divided into a stream of odd chips and a stream of even chips, which are provided to separate waveform generators. An output from each waveform generator is combined and modulated as a continuous phase modulation signal.

Symbol Error Probability Bounds for Coherently Viterbi Detected Continuous Phase Modulated Signals

Abstract: Recently the minimum Euclidean distance and bandwidth properties of continuous phase modulated (CPM) signals have been considered. It has also been shown that, for rational modulation indexes, a state description of these signals is possible and that the Viterbi algorithm (VA) can be used for demodulation. In this paper the performance analysis of CPM systems is extended to obtain bounds on the symbol error probability when the VA is used. The calculation of these bounds is based on the transfer function technique, which has been generalized. From numerical comparisons of the upper and lower bounds, it is concluded that the minimum Euclidean distance is a good performance measure for a broad class of CPM signals, even when the symbol error probability is as large as 10-2.

Transmission limitations of CPFSK coherent lightwave systems due to stimulated Brillouin scattering in optical fiber

Abstract: Transmission limitations imposed by stimulated Brillouin scattering (SBS) are investigated for repeaterless coherent lightwave systems, particularly for continuous phase-shift keying (CPFSK). The effects of SBS on the modulated signals in optical fibers are studied for CPFSK, amplitude shift keying (ASK), and phase shift keying (PSK). A generalized model based on the maximum power spectrum density (PSD) in the modulated signals is proposed for SBS analysis. This model is useful to estimate the Brillouin gain and its threshold to determine the optical power limitation of the fiber for any modulated signal with non-negligible linewidth. It is clarified theoretically that the Brillouin gain with CPFSK approaches that with ASK and PSK at higher bit rates if the modulation index is 1 and 0.65, respectively. The dependency of Brillouin gain on bit rate and linewidth of a laser diode transmitter are evaluated. SBS induced by CPFSK modulated signals was measured to clarify the modulation condition dependences and to verify the model. >

System and method for combining two data streams while maintaining the continuous phase throughout the combined data stream

Abstract: A system and method for a generating a data stream for encoding by combining data from a multiple of sources. In order to maintain a continuous phase in the combined data stream, any phase differentials between the data supplied from the multiple sources are eliminated upon combination of the source data. The phase differential between the data from any two different sources is eliminated by trimming data from one of the sources such that when the trimmed data is combined with the data from the other source the resulting combined stream has a continuous phase.