Coefficients Optimization Based Quasi-constant Envelope Multiplexing Technique and Its Applications

T. Yan, J. Wei, Z. Tang, Y. Cao

Abstract:	A significant feature of the modernized GNSS signals is that there are more than one service signal at a carrier frequency, and each service signal includes a data component and a pilot component. That means there may be more than four signal components needing to be transmitted at the same carrier frequency. Therefore it is a problem how to combine multiple signals becoming a constant envelope composite signal with the highest combination efficiency. To solve this problem, we propose a coefficients optimization based quasi-constant-envelope multiplexing technique in this paper. This method is based on the following conclusion, namely final composite signal can be seen as the sum of useful single signals, undesirable 2-order inter-modulation (IM) signals, … , N-1 order IM signals and N-order IM signals. Our method achieves the constant envelope composite signal by optimizing these complex coefficients of all signals. All combinations of N binary PRN signals form a matrix, and all complex coefficients form a column vector. Each complex coefficient is expressed by amplitude and phase angle. The power constraint and phase constraint among signals can be directly achieved by setting coefficients, thus there is not 180 degrees phase ambiguity problem. Only the constant envelope constraint needs to be considered in our method. When we need to suppress some IM signals due to special requirements, we can reach it by setting corresponding coefficients to be 0. This method can work in two ways, and corresponding objective functions are given out. One is to obtain the highest combination efficiency, which is the same with POCET technique. The other is to pre-set the combination efficiency, which may help us further understand the nature of signal combination. It is noted that the final envelope is close to constant in our method, thus we call it as quasi-constant envelope multiplexing technique. To verify its performance, we present several fact application examples. Results show our method is effect and achieves above expected function.
Published in:	Proceedings of the 2014 International Technical Meeting of The Institute of Navigation January 27 - 29, 2014 Catamaran Resort Hotel San Diego, California
Pages:	825 - 834
Cite this article:	Yan, T., Wei, J., Tang, Z., Cao, Y., "Coefficients Optimization Based Quasi-constant Envelope Multiplexing Technique and Its Applications," Proceedings of the 2014 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2014, pp. 825-834.
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