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.

Serially Concatenated Space-Time Coded Continuous Phase Modulated Signals

Abstract: We investigate the detection of space time codes (STC) modulated using continuous phase modulation (CPM), in quasi-static fading channels. A symbol-by-symbol iterative detector with an optimum front-end is derived, and its reduced-complexity implementation is considered. Also, we have introduced several full-rank STC-CPM systems, constructed by combining full-diversity STCs with simple, widely-used CPM schemes, and introducing a small frequency offset. According to the simulation results, the bit error rate (BER) performance of the detector for quasi-static fading is around 1 dB from the case without fading. Furthermore, a comparison of the performance of the proposed detector with results from previous work on STC-CPM showed an improvement in the range of 2-3 dB. Moreover, the detector is robust to the errors in estimating the channel state information (CSI), which is a desirable feature for practical implementation.

Phase Only Liquid Crystal Light Modulator And Its Application In The Fourier Plane Of Optical Correlation Systems

Abstract: It has been shown theoretically that optical correlation systems which use phase only filters are capable of producing sharp correlation peaks and good discrimination between different input objects, whilst at the same time having high optical efficiency. In addition to this, the resolution required in the filter plane is very much lower than that required for an equivalent conventional Van der Lugt correlator using a matched filter which has been made holographically. Here, we describe a flexible phase only filter implemented using a special-purpose liquid crystal spatial light modulator, and present results which demonstrate how it can be applied in optical correlation systems. 1. INTRODUCTION There has recently been a great deal of interest in phase only filters as applied to optical correlation systems. This type of filter modifies the phase distribution of light passing through it, without altering the amplitude distribution. It has been shown by computer simulation that, when applied in the Fourier Plane of coherent optical,correlation systems, phase only^fliters are capable of giving very sharp correlation peaks and high optical efficiency .The work of Psaltis et. al. 3 and Flannery et. al. 45 ' has demonstrated very effectivelythat useful optical correlators can be constructed using phase only filters implemented with spatial light modulators which have limited pixel counts (typically 128 X 128 pixels).However, these authors used magneto-optic devices , which only allow binary phase modulation of the incoming light - i.e. the only phase modulation values allowed for each pixel are zero or PI. Whilst binary phase only filters can give good correlation performance in most situations, with some types of object (particularly self-symmetric, displaced, reference objects) they can give undesirably^ ghigh noise levels and even false correlation peaks in the output correlation plane ' . Even though the amount of information required to write binary phase only filters is lower, in many situations - particularly where safety ^considerations are involved - the true phase only filter is preferable. In previous work we have shown how it is possible to use a commercially available twisted nematic liquid crystal television panel as a continuous phase only modulator, but construction of a practical correlator using this technique would be very difficult since the phase modulation depth available is very limited, and the aberrations of the panel very high.In this paper, we describe a new special-purpose liquid crystal panel which can be used as a continuous phase only spatial light modulator, and it's application in an optical correlator system. The panel is not twisted nematic, and so phase modulation can be achieved in one pass with essentially very little change in the polarisation state of the light passing through it. The panel we used was designed to have a phase modulation depth in excess of 2PI, and low aberrations, and this enabled us to use it with high efficiency and with no aberration correction.

System and method for coherent multi-h continuous phase modulation waveform

Abstract: A system and method improves ECCM and data payload for a multi-h continuous phase modulated waveform with the addition of frequency hopping capabilities. The system and method exploit the short constraint length and rotational invariance of the multi-h CPM waveform to enable frequency hopping using current system capabilities. The transmitted data is structured such that the initial phase state of each hopping frame is in the zero state and the final phase state of each hopping frame is cycled to zero by the addition of flushing symbols and transition symbols. The transition symbols allow the oscillator to change frequency without disrupting the phase progression. The system and method uses synchronous demodulation of the transmitted data at a plurality of phase offsets and determines the best phase offset based on the total sum of the branch metrics for each symbol and phase offset. The system and method alternatively demodulated with a phase offset that is tracked and adjusted over each hop by accumulation of the frequency error.

Frequency modulation receiver circuits

Abstract: My present invention relates to frequency modulation receiver circuits, and more particularly to novel methods of, and means for, receiving frequency modulated carrier wave energy while simultaneously removing the effects of undesired amplitude modulation without the aid of a limiter per se....