Design And Realization Of Adjustable Phase And Multi-channel Combined Signal Generator

In the radio navigation system, navigation stations transmitted ground-waves for navigation and positioning. Navigation receivers would be often subjected to sky-waves' interference, near-far effect and Doppler-frequency-shift. In order to facilitate the study of radio navigation system, the main signals should be simulated in the laboratory environment. The adjustable phase and multi-channel combined signal generator should have two functions to simulate 3 ground-waves and 6 sky-waves. First, carriers' amplitude, phase and frequency should be adjusted in high precision. Second, the initial value of PN code should be set.This paper began with the basic theory of spread spectrum communication. It introduced the basic model of the DS signal generator. After the research of the sky-waves and the ground-waves, the signal parameters were given. All of them were preparing for the implementation of the signal generator. The hardware circuit of the signal generator included MCU control system circuit, the carrier generator circuit, PN code generator circuit, filter circuit, amplifier circuit, modulation circuit and signals combining circuit. The software design was comprised of two parts. One part was completing the designs of communication interface, PN code generator and the delayed module, the other part was debugging the various waveforms through the MCU, which was used to control AD9854 and CPLD. Then, based on the debugging experience, the design principles of circuit board and the debugging experience were given. Finally, a variety of expected waveforms were tested.Test results indicated that the signal generator fully integrated hardware and software advantages. It had the characteristics of wide bandwidth, PN code phase and carrier phase adjustment, as well as little power loss of signal synthesis. It could reach the expected function.