Design And Implementation Of Six - Port Radar System

Six-port-circuit is a highly symmetric microwave passive component. It can be used to accurately measure the phase difference between two import ports through the amplitude information of the four output ports. When applied to the direct conversion receiver, it can be used to replace the mixer in the receiver. Six-port-radar has the advantage of high measurement precision, simple processing, low cost, small volume, and it’s easy to integrate, therefore it has great research value.This paper first introduces the background of the six-port circuit, and elaborates on the significance of six-port technology. Then we discuss the development and application situation of six-port-technique, and briefly introduce the main signal processing methods of frequency modulated continuous wave radar.Next up is the formula derivation. Also we introduce the calibration of six-port, and the detailed analysis of the expression form of eco signal, the target distance, and the radial velocity for the six-port-Doppler radar and six-port-LFMCW radar. Then this paper realizes the six-port radar system, and we introduce the design and realization of the key part in the front end of six-port-LFMCW radar, focusing on the realization of frequency source based on DDS and PLL. In the testing process of the detector, we use least squares method to fit the curves between detection voltage and input power, and successfully correct the inconsistency of the detector. We also run a Matlab simulation on the process of signal processing algorithm of six-port-LFMCW-radar, and on the influence that the error lays upon target detection. There’s a lot of DC offset contained in the I、Q orthogonal signals which have different magnitude. This paper calculates the integral on multiple cycles to eliminate the DC offset and making I、Q signals have consistent amplitude. Meanwhile, this paper improves the target matching method for multiple target situations based on cosine similarity.Finally, this paper tests the six-port-radar system, and the test results indicate that the six-port-radar can successfully realize effective detection of the target.