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.

Dual stage carrier phase estimation for 16-QAM systems based on a modified QPSK-partitioning algorithm

Abstract: Coherent optical communications based on higher order modulation formats are severely affected by the phase noise of transmitter and receiver lasers. In this work, a novel yet simple scheme is presented for carrier phase estimation (CPE) of 16-ary Quadrature Amplitude Modulation (16- QAM) formats, based on a modified QPSK-partitioning algorithm. The proposed algorithm can tolerate a linewidth times symbol duration product (Δv · Ts) of the order of 10-4, with 1 dB penalty at a bit error rate (BER) of 10-3. Tolerance can be further improved by introducing a maximum likelihood estimation (MLE) stage (Δv · Ts ≈ 1.432×10-4). Comparison of the scheme with other proposed algorithms is shown. The obtained results indicate that the presented approach can be used with the commercially available state of the art lasers for 16-ary Quadrature Amplitude Modulation (16- QAM) transmission at 100 Gbps.

Dual-phase continuous phase modulation for spread-spectrum multiple-access communication

Abstract: A new class of direct-sequence spread-spectrum multiple-access (DS-SSMA) systems with continuous phase modulation (CPM) is defined. The signals are unique in that the spreading is done by adding an extra phase term to the information phase while maintaining phase continuity, constant envelope, and efficient bandwidth usage. The spreading phase is formed from the spreading code and is independent of the information phase, which allows despreading to be done separately before data detection, which, in turn, allows a simple CPM detector to be employed for data detection. The information phase is considered in the minimum-shift keying (MSK) format, and a serial-MSK-type spread-spectrum receiver is considered for performance analysis. Expressions for the signal-to-noise ratio, the power spectral density, and the probability of bit error are developed, along with methods for computing their values to an arbitrarily close approximation. Numerical results show that the proposed system is an attractive alternative to the conventional DS-SSMA systems.

Continuous Phase-Modulated Halftones

Abstract: A generalization of periodic clustered-dot halftones is proposed, wherein the phase of the halftone spots is modulated using a secondary signal. The process is accomplished by using an analytic halftone threshold function that allows halftones to be generated with controlled phase variation in different regions of the printed page. The method can also be used to modulate the screen frequency, albeit with additional constraints. Visible artifacts are minimized/eliminated by ensuring the continuity of the modulation in phase. Limitations and capabilities of the method are analyzed through a quantitative model. The technique can be exploited for two applications that are presented in this paper: (a) embedding watermarks in the halftone image by encoding information in phase or in frequency and (b) modulating the screen frequency according to the frequency content of the continuous tone image in order to improve spatial and tonal rendering. Experimental performance is demonstrated for both applications.

Techniques for acquiring and tracking MIL-STD-181B signals

Abstract: The paper examines the use of spectral estimation and maximum likelihood estimation techniques in acquiring and tracking current MIL-STD-188-181B UHF SATCOM waveforms Digital signal processing (DSP)-based algorithms are presented that can acquire and track the carrier phase, carrier frequency offset, and symbol timing for the dual-h quaternary continuous phase modulated (CPM) waveforms The algorithms are derived mathematically first, then using computer simulations Performance is presented for various modulation rates, channel conditions, and different signal-to-noise ratio (SNR) levels Several methods are then proposed to enhance the performance of these algorithms without requiring additional computational resources The algorithms are easily configurable for different modulations and data rates, thus making them suitable for implementation in next generation software-defined UHF tactical radios

Adaptive HMM filters for signals in noisy fading channels

Abstract: Kalman filtering (KF) and hidden Markov model (HMM) signal processing techniques are coupled to demodulate signals transmitted through noisy fading channels. The demodulation scheme presented can be applied to both digital M-ary differential phase shift keyed (MDPSK) and analog frequency modulated (FM) signals. Adaptive state and parameter estimation algorithms are devised based on the assumption that the transmission channel introduces time-varying gain and phase changes, modelled by a stochastic linear system, and has additive Gaussian noise. Our technique is to use an HMM filter, for signal estimation, coupled with a KF, for channel parameter tracking. The approach taken can easily be generalised for other transmission schemes, such as continuous phase modulated (CPM) signals. >