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.

Model-based phase velocity and attenuation estimation in wideband ultrasonic measurement systems

Abstract: A parametric method to estimate frequency-dependent phase velocity and attenuation is presented in this paper. The parametric method is compared with standard nonparametric Fourier analysis techniques using numerical simulations as well as real pulse-echo experiments. Approximate standard deviations are derived for both methods and validated with numerical simulations. Compared to standard Fourier analysis, the parametric model gives considerably lower variance when estimating attenuation and phase velocity. In contrast to nonparametric techniques, the proposed estimator avoids the phase unwrapping problem because analytical expressions for the continuous phase velocity and attenuation can be derived

On Analysis and Design of Low Density Generator Matrix Codes for Continuous Phase Modulation

Abstract: We investigate the analysis and design of low density generator matrix (LDGM) codes for continuous phase modulation (CPM). The system uses LDGM codes as an outer code for CPM. For additive white Gaussian noise channels, we derive the union bound to analyze the error floor performance. Design principles for lowering error floors are suggested from this analysis. We propose a design approach of jointly considering the LDGM code degree and the CPM modulation index. Then we consider the rate-adaptive system for slowly fading channels. By changing the rate of the LDGM codes, the information rate of the CPM signals is adapted according to channel variations. We use a low-rate LDGM code as the mother code. Higher rates are achieved by puncturing the output of these codes. To exploit the rate-flexible property of punctured LDGM codes, a rate function is proposed to calculate the rate of each transmitted block. Thus, we can have a quasi-continuous information rate. Numerical results show that this approach can improve the energy efficiency from a discrete-rate adaptation. Using the rate-adaptive approach, up to 11 dB transmitted energy gain can be achieved from the non-adaptive scheme in the low bit-error-rate region (smaller than 10-3) for minimum shift keying (MSK).

Phase shifting and combining architecture for phased arrays

Abstract: Improved phased array techniques and architectures are provided. For example, a linear phased array includes N discrete phase shifters and N−1 variable phase shifters, wherein the N−1 variable phase shifters are respectively coupled between adjacent output nodes of the N discrete phase shifters such that the N discrete phase shifters reduce an amount of continuous phase shift provided by the N−1 variable phase shifters. Each of the N discrete phase shifters may select between two or more discrete phase shifts. The N discrete phase shifters also preferably eliminate a need for a variable termination impedance in the linear phased array.

Method and apparatus for quadriphase-shift-key and linear phase modulation

Abstract: A submultiple (30Fl) of an S-band transmitter output frequency (240Fl) is divided equally between a linear phase modulation branch and a QPSK modulation branch. The linear modulation branch includes a multiplier (X7) to increase the carrier frequency to a level (210Fl) which, when combined with the carrier in the QPSK branch in an up-converter (utilizing a mixer at the input thereof followed by a bandpass filter), produces the transmitter output frequency. This allows the QPSK modulator to operate at one-eighth of the output frequency where repeatable and precisely controlled modulation can be easily achieved. This also allows linear phase modulation at one-eighth the output frequency where low modulator deviation and good linearity can be easily maintained.

A blind carrier frequency estimation algorithm for digitally modulated signals

Abstract: In this paper, we consider estimation of the carrier frequency of a single-tone digitally modulated signal in the automatic modulation recognition (AMR) environment. This issue is quite different from that in the cooperative communications systems since the AMR receiver works in a non-cooperative mode with the transmitter. That is, the AMR receiver does not have any priori knowledge of the transmitted signal such as symbol rate, shaping pulse, modulation type, and constellation size. A blind carrier frequency estimation algorithm is presented in this paper based on the phase information of the autocorrelations of the received signal. The phase distribution has been analyzed, and an iterative mechanism has been employed to improve the accuracy of carrier frequency estimation. Simulations show that the algorithm works well for amplitude-shift keying (ASK), phase-shift keying (PSK), and quadrature amplitude modulation (QAM) signals.