An improved method of data alignment for angle measurement in monopulse radar

Accurately measurement of target's range and angle are essential parts for the purpose of real time target tracing. The range between target and radar can be calculated by the time delay of target echo. Meanwhile, there are a variety of mature algorithms on target angle measuring. The monopulse angle measurement is a commonly adopted method. In monopulse radar system, we use the data sampled by sum channel and diff channel to calculate the target angle information. So the channel sampled data is important for angle calculation. The phase coherence between sum channel and diff channel is essential condition. On a PCB board based on high speed AD converter and FPGA, the length of multiple difference pairs of data lines usually are not equal, which will result in the different arrival time to the FPGA logic. It will cause phase offset between different data channels. In this case, it would not be carry out angle measurement precisely. On this background, this paper proposes an auto data alignment method based on first-in-first-out (FIFO) in FPGA. This paper introduces the method in detail and makes a comparison on the data results of alignment. The results validate the effectiveness. This method has been successfully used in radar systems.