Band-Limited Multicarrier Multiplexing Technique for Navigation Signals

In order to reduce the complexity of the payload on the satellite, the navigation signals located at several adjacent frequency points usually need to be multiplexed and transmitted through a common transmission link. Existing multicarrier multiplexing techniques usually require that the composite signal have a constant envelope to reduce nonlinear distortion caused by the high-power amplifier (HPA). However, due to the bandwidth limitation of the filter, the constant envelope characteristic of the composite signal is damaged to a certain extent, so HPA linearization is still needed. In this paper, we assume that the HPA is well linearized, and propose a band-limited multicarrier multiplexing technique for navigation signals. Firstly, the mathematical model of band-unlimited multicarrier multiplexing problem is established. In this band-unlimited model, we clarify that the composite signal is composed of navigation signals and auxiliary signals introduced to reduce the peak-to-average power ratio (PAPR) of the composite signal. Then, the band-unlimited navigation signals and the auxiliary signals are simultaneously filtered. Next, we establish an optimization problem which takes the linear combination coefficients of the filtered auxiliary signals as the optimization variables and minimizes of the infinite norm of the composite signal, so as to optimize the amplification efficiency of the useful navigation signals. This optimization problem is convex, therefore the global optimum can be obtained easily. At the same time, the proposed method ensures that the introduced auxiliary signals do not adversely affect the reception of useful signals. Simulation results show that the proposed method can achieve lower PAPR and higher amplification efficiency compared with existing methods. In addition, the proposed method has high flexibility, which deals with single carrier multiplexing and multicarrier multiplexing in a uniform framework, and can support diversified modulation schemes.