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.

Single-channel receiver limitations in Doppler radar measurements of periodic motion

Abstract: Periodic motion, such as that resulting from cardiopulmonary activity can be measured by direct-conversion microwave Doppler radar. In a direct-conversion receiver, motion is measured as phase modulation, and the baseline phase relationship between the received signal and local oscillator signal for a given position has a significant effect on the demodulation sensitivity, resulting in optimum and null case extreme target positions. Presented here is a mathematical analysis of this target-position sensitivity verified with measurements using a custom compact Doppler radar transceiver with separate quadrature outputs. The results indicate that increased error in respiration and heart rate measurements can be expected for null case positions due to significant changes in mathematical conditions as well as reduced sensitivity, and that these limitations can be accommodated using two receiver channels in quadrature.

Spectrally Precoded OFDM

Abstract: By bilinearly transforming the rectangularly pulsed multicarrier basis signals, new basis sets containing full-response continuous basis signals are developed for constructing spectrally efficient orthogonal frequency-division multiplexing (OFDM) signals with or without cyclic prefix (CP) or zero padding (ZP). Both multiple-product and linear-combination formats are presented for these basis sets. In the multiple-product format, the developed full-response basis signals are shown to be zero-valued at interval edges, and thus can be used to construct continuous-phase OFDM signals. It is analytically shown that the constructed continuous-phase OFDM signals exhibit relatively small power spectral sidelobes which fall off as f-4, and can thus provide much higher spectral efficiency than the traditional rectangularly pulsed OFDM signal. In the linear-combination format, the proposed basis signals are shown to be the linear combinations of rectangularly pulsed multicarrier basis signals, and thereby allow for the efficient realization of fast Fourier transform (FFT). Specifically, a spectrally precoded signaling structure is developed in conjunction with inverse FFT and guard insertion to construct continuous-phase OFDM signals with or without CP or ZP. The corresponding spectral decoders are also developed to enable zero-forcing (ZF) demodulation for spectrally precoded OFDM. With the zero-forcing demodulation, the spectrally precoded OFDM schemes are shown to outperform in average error-rate characteristics the conventional rectangularly pulsed and correlatively coded OFDM schemes on various delay-spread channels

Reduced state sequence detection of partial response continuous phase modulation

Abstract: A reduced state sequence detector (RSSD) which combines decision feedback with Viterbi decoding is proposed for partial response continuous phase modulation (CPM). This detector can successfully be used for both binary and high-level partial response CPM schemes. This detector is analysed by means of minimum Euclidean distance and by simulations of the symbol error probability. It is shown that the phase states in the receiver trellis of the maximum likelihood detector for partial response CPM can be exchanged by decision feedback in the metric calculations. This can be achieved without sacrificing minimum Euclidean distance of the first error event or symbol error probability. This RSSD is most attractive for narrow-band CPM schemes and at most about 2 dB in increased energy efficiency as compared with MSK is possible. Further reductions in number of states is possible, especially for high-level CPM schemes, by reducing the number of correlative states. For the most frequently used CPM schemes this can be done with a very small degradation in error performance. In this class of schemes, a complexity reduction of at least a factor five to ten is possible.

Trellis-coded continuous-phase frequency-shift keying with ring convolutional codes

Abstract: Trellis-coding techniques are applied to continuous-phase frequency-shift keying (CPFSK). A new coding scheme based on convolutional codes on the ring of integers modulo-P is shown to be a natural way to apply trellis coding to CPFSK. Previous work has decomposed CPFSK into two parts: a linear encoder, with memory called the continuous phase encoder (CPE), and a memoryless modulator (MM), where the CPE often has a code structure defined over the ring of integers modulo-P. The combination of a modulo-P convolutional channel encoder (CE) and the CPE is a linear modulo-P encoder. Design examples are given for rate-1/2 coded quaternary CPFSK with modulation indexes 1/2 and 1/4, and rate-2/3 coded octal CPFSK with modulation index 1/8. Combinations are optimized in the normalized minimum Euclidean distance sense for a given total number of states in the overall MLSE receiver. Numerical results show that this new coding scheme consistently obtains better performance than previous schemes. >

Linewidth-Tolerant and Low-Complexity Two-Stage Carrier Phase Estimation for Dual-Polarization 16-QAM Coherent Optical Fiber Communications

Abstract: Two novel linewidth-tolerant, low-complexity feedforward carrier phase estimation algorithms are described for dual-polarization 16-ary quadrature-amplitude-modulation with coherent detection. For both algorithms, the carrier phase is estimated in two stages. The first stage employs either a simplified quadrature-phase-shift-keying (QPSK) partitioning algorithm or the blind phase search (BPS) algorithm. The second stage employs a novel QPSK constellation transformation algorithm. The performance and linewidth tolerance of both algorithms are evaluated using experimental and simulation data, and the hardware complexity is assessed. For both proposed two-stage algorithms, the linewidth symbol duration product is 1.3 × 10-4 for a 1 dB penalty in optical signal-to-noise ratio at a bit error ratio of 10-3. This performance is comparable to a single-stage BPS algorithm with a large number of test phases, but with a reduction of the hardware complexity by factors of about 2.5-11.