Research Of Algorithm And Structure Of High Data Throughput Equalizer For Satellite Systems

With the increase of information content in the communication networks, the channelequalizer in the modern satellite high-speed data transmission system must have betterperformance, such as data throughput, margin and phase errors inhibition, convergencespeed and steady-state error, and so on. Currently, Bussgang-type algorithm, due to thesignificant algorithm performance and the low computational complexity, has attractedgreat attention in theory research and practical engineering. But Bussgang-type algorithmis restricted by its inherent mechanism. It has serious flaws in the phase error inhibitionfor the modulation signal with the circle envelope and the constellation characteristics, inthe equalization performance for the modulation signal with the multi-modulus, and in thedata throughput for the equalizer in practical engineering. Therefore, in this paper, thephase error inhibition of the modulation signal, the equalization performance of themulti-modulus modulation signal, and the data throughput of the equalizer are studiedbased on the satellite channel model. The satellite channel model has the characteristics ofnonlinear phase-frequency characteristic, which is established by the parameter of thegroup delay.To cancel the phase error of the transmission signal, the matched constellation phasealgorithm and the quadrant constant phase algorithm are proposed for the modulationsignal, respectively. The modulation signal has the single-modulus and multi-modulusconstellation characteristics of the circle envelope. According to the single-modulusconstellation characteristic of the circular envelope, the constellation phase errorcomposed of sine function is established. Then the constellation phase matching algorithmis obtained by weighting the cost function of constant modulus algorithm and the matchedconstellation phase error. According to the multi-modulus constellation characteristic ofthe circular envelope, the quadrant constant phase algorithm is obtained by constructingthe matched constellation phase based on the hypothesis that phase statistic in the quadrantis constant.To obtain the steady convergence of the algorithm and make a match between the algorithm and the constellation characteristic of multi-modulus modulation signal, thedual-mode constant modulus equalization algorithm and the dual-mode multi-modulusequalization algorithm are proposed for the modulation singal with the constellationcharacteristics of the circle envelop and rectangular envelope, respectively. The algorithmestimates the covergence status of equalizer by the recursive equation, and obtains thedecision threshold according to the distribution characteristics of the output signal in theconvergence process for equalizer. Then the algorithm realizes the dual-mode control forthe equalizar. The algorithm was set when equalizer worked in the mode of the constantmodulus. Just then the equalizer obtained the steady converengence. After the algorithm isbuilt, the equalizer works in the mode of the variable modulus. Now, the coverengenceand stability of the euqalizer are improved by matching the algorithm and constellationcharacteristic.To eliminate the constraint condition of the data throughput from the electronicdevices and to improve the throughput of equalizer, the parallel filter and pipelinealgorithm iterative equalizer is proposed. Then the equalization algorithm for thisequalizer is designed. Using the equalization algorithm proposed in this paper, thethroughput of equalizer is increased and the overall performance of the equalizer isimproved. In this equalizer, the parallel filter is used to eliminate the restriction ofmaximum data throughput when electronic devices operate on high rate. And the Pipelineis used to reduce the diminution of real time for electronic devices by iterative cycle. Butin this equalizer, the iterative cycle is increased and the singal transmission rate is reduced.Based on this, according to the variation of gradient descent principle and the tapcoefficient of the equalizer, the gradient pattern equalization algorithm is proposed.From these research contents, the equalizer design solutions which can eliminateconstraint on data throughput form electronic devices, implement suppression of phaseerror, and match the multi-modulus feature are proposed based on the representativemodulation method with all kinds of envelope and the modulus constellationcharacteristics. For example, the modulated signal of quadrature phase shift keying,8order phase shift keying,16order quadrature amplitude modulation, and16orderamplitude phase keying. At the end, the satellite data transmission test platform is built based on group delay characteristics. And the design soluations of electronic devicesFPGA for the algorithms are completee. The experiment results show the efficiency of thealgorithms by analyzing the error value on output signal of FPGA and the constellationdiagram.