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.

Method for displaying the modulation error of a multiple carrier signal

Abstract: The invention relates to a method for displaying the mean modulation error MERRMS of a multiple carrier (OFDM) signal in which: a) The square of the error vector is calculated according to the relation (I) for each actual modulation symbol I of each individual carrier k of the multiple carrier signal; b) this value mk is offset with the content of a storage location of a memory, said storage location being assigned to the same carrier k, which comprises the same number of storage locations as the OFDM signal carrier, according to relation (II) (iteration formula) with A2k,l+1: new measured value (instant l+1) which should be filed in storage location k of the memory A2; A2k,l: previous measured value (instant l) from storage location k of memory A2; mk: Actual measured error square for carrier k; k: Carrier number within the OFDM spectrum, grows with the frequency, k=0 ... Kmax; l: number of the symbol, grows with time, 0≤l; c) the mean modulation error MERRMS is subsequently calculated for each carrier from these values of the storage locations according to relation (III), whereby VM is the quadratically weighted mean value of the amplitude of all ideal signal states of the modulation type, used each time, of a carrier modulated with useful data, and finally, d) this MERRMS value is then graphically represented with the number of the carriers as an abscissa for each individual carrier k as an ordinate value of a diagram.

Compensation of Laser Frequency Fluctuations and Phase Noise in 16-QAM Coherent Receivers

Abstract: Frequency fluctuations caused by mechanical vibrations, power supply noise, and other mechanisms are detrimental to the phase estimator performance in high speed intradyne coherent optical receivers. In this letter, we propose the use of a low-latency parallel digital phase lock loop in combination with common feed-forward carrier phase recovery algorithms in order to compensate both the phase noise and laser frequency fluctuation effects on 16-quadrature amplitude modulation receivers. Numerical results demonstrate the excellent behavior of the proposed two-stage carrier recovery scheme.

Carrier phase estimation for 16-QAM optical coherent systems using QPSK partitioning with barycenter approximation.

Abstract: This paper presents a hardware-efficient carrier phase estimator with high-linewidth tolerance for 16-QAM optical coherent systems. The laser phase noise is estimated using quaternary phase-shift keying (QPSK) partitioning complemented with a low complexity angle-based barycenter approximation as opposed to the classical Viterbi and Viterbi algorithm. The various stages necessary for partitioning and removing the modulation on the received symbols for carrier phase recovery are presented. We show that the phase offset in the middle ring for a 16-QAM constellation can be removed through a simple comparison with the symbols lying on the inner and outer rings of the constellation thus enabling all the symbols to be efficiently utilized for carrier phase recovery. We assess the performance of different filter structures for 16-QAM with filter half width 8 and 16. Simulation results demonstrate that combined linewidth symbol duration product $\Delta u \cdot T_s$ of $10^{-4}$ is tolerable at the target BER of $10^{-2}$ and $10^{-3}$ when using the barycenter algorithm. Finally, carrier phase recovery in a 16-QAM experiment is investigated to validate the performance of the proposed algorithm.