Design And Implementation Of The Phased Array Beam Forming Based On FPGA

The Doppler Velocity Measuring System measures the moving speed of the ship relative to the seabed or the water layer by sending or receiving sound wave in the water. The application of phased array technique has solved the problem of sound velocity compensation in the system design, which improves the system precision of velocity measurement. When broadband signal is used, the system could have a better frequency resolution, but this will also bring higher requirements for the design of received signal beam forming.This paper focuses on the following tasks:the system hardware circuit design, the simulation and implementation on the FPGA for the phased array beam forming of the received broadband signal. The hardware circuit design comprises the choosing of the power chip, the circuit design for the signal sampling, serial data transmission and data storage, and the encryption design for the master DSP.A ninety degrees'phase shift need to be added to the received signals for the phased array beam forming. Originally analog devices are used to shift the phase of the single frequency signals, when broadband signal is adopted in the system, Hilbert filter is used to shift the signal phase, and the framework of phased array beam forming is designed which can be easily implemented on the FPGA.The paper designs the appropriate rank of the Hilbert filter by simulating the phase shifting characteristic of filters with different ranks. The phase shifting precision is analyzed, and the whole beam forming process is also simulated. According to the system framework and the data throughput requirements, detailed introduction is given to the program structure and the addressing method of the filtering and correlation module.Finally, the designed FPGA program is tested on board using different input signals to verify the correctness of the program.