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.

Frame and carrier synchronization for unbursted packetized transmissions using constant-amplitude continuous-phase frequency-modulation

Abstract: A system and method for performing frame and symbol timing synchronization on samples of a received signal that includes a series of frames. Each frame includes a known preamble and payload data. A start-of-frame time is estimated by scanning the received signal samples for the self similarity of two successive preambles. A carrier frequency offset (CFO) is estimated by maximizing a correlation between a magnitude spectrum of the received signal and a magnitude spectrum of a known preamble model. A fine estimate for the CFO is determined by computing a phase difference between samples separated by p repetitions of the base pattern for various values of index p, and computing a slope of a least squares affine fit to the phase differences. Additional operations are performed to find an optimal symbol starting point, to perform carrier phase synchronization and to detect the start of payload data.

Limiter-discriminator detection of continuous phase modulation (CPM) Tomlinson filtering

Abstract: Limiter-discriminator detection of continuous phase modulation (CPM) partial response signals is of special importance in systems in which phase coherence is very difficult to establish and/or maintain (e.g., mobile communications systems). The authors propose a Tomlinson-based approach which copes with the intersymbol interference (ISI) introduced by the baseband partial response frequency modulating pulses of the CPM schemes, (e.g., GTFM, GMSK, raised cosine (RC)). In this approach, the ISI equalization is divided between the transmitter and the receiver. The authors investigate, through simulation, the detectability performance and spectral properties of a number of CPM signals and receiver structures with special emphasis on the Tomlinson approach. It is shown that this novel application of the Tomlinson configuration allows the use of relatively simple receivers which exhibit almost the same performance as more complex Viterbi structured receivers. It is shown that a bandwidth-efficient narrow-band quaternary CPM-2RC modulation with either a Viterbi, a DFE or a Tomlinson receiver structure outperforms classical binary FSK (discriminator-integrate and dump detection) by approximately one db. It is pointed out in the paper that in general it is also possible to achieve detectability results similar to that of classical discriminator (integrate and dump) detection of binary CPFSK, for a number of bandwidth-efficient binary CPM schemes (e.g., GMSK) using the aforementioned receiver structures. >

Continuous phase modulation system and method with added orthogonal signals

Abstract: A system and method of the present invention forms a hybrid encoded signal. A signal generator generates a coded waveform having a trellis structure, such as a continuous phase modulated signal. A modulator is operative with the signal generator and adds at least one orthogonal or amplitude modulated waveform to a trellis structure of the coded waveform to create a non-constant envelope modulated signal that has at least one of increased bandwidth, improved bit error rate, or an increased number of bits encoded into a single symbol.

Methods of predicting power spectral density of a modulated signal and of a multi-h continuous phase modulated signal

Abstract: Methods for predicting the power spectral density of modulated waveforms are based on symmetric and Hermitian forms of a matrix equation. These forms facilitate the use of a Fourier transform method of prediction. In one embodiment, these methods are applied to a particular class of constant-envelope waveforms known commonly as multi-h continuous phase modulation. Various expressions for the power spectral density are then provided as well as an expression for an upper bound. These expressions facilitate the design of waveforms for practical use.

Algebraic Phase Unwrapping Based on Two-Dimensional Spline Smoothing Over Triangles

Abstract: Two-dimensional (2D) phase unwrapping is an estimation problem of a continuous phase function, over a 2D domain, from its wrapped samples. In this paper, we propose a novel approach for high-resolution 2D phase unwrapping. In the first step—SPline Smoothing (SPS), we construct a pair of the smoothest spline functions which minimize the energies of their local changes while interpolating, respectively, the cosine and the sine of given wrapped samples. If these functions have no common zero over the domain, the proposed estimate of the continuous phase function can be obtained by algebraic phase unwrapping in the second step—Algebraic Phase Unwrapping (APU). To avoid the occurrence of common zeros in SPS due to phase noise in the observed wrapped samples, we also propose a denoising step—Denoising by Selective Smoothing (DSS)—as preprocessing, which selectively smooths unreliable wrapped samples by using convex optimization. The smoothness of the proposed unwrapped phase function is guaranteed globally over the domain without losing any desired consistency with all reliable wrapped samples. Numerical experiments for terrain height estimation demonstrate the effectiveness of the proposed 2D phase unwrapping scheme.