Development, Frequency Synthesizer Based On Dds Technology Of Millimeter-wave Radar Transceivers

Radar transceiver is one of the most significant elements in the radar system. With the rapid development of microwave circuits, a desire for radar transceiver with high performance is increasing rapidly. For the radar system in millimeter wave band, local oscillator has direct influence on the communication system. Besides, the local oscillator is always acheived by frequency synthesis technology. To achieve high-performance quality of communication, it is generally required to have good performance in frequency stability, spectral purity and frequency switching speed. Based on these key points, this thesis designs a radar transceiver in millimeter wave band, with low phase noise, low spurs and high frequency-switching speed.First of all, in the thesis, we analyze the theory and characteristics of frequency synthesis technology. We also analyze the phase noise and spurs of DDS and mixer. Then, according to the requirements of tasks, we propose a system configuration of millimeter wave band radar transceiver by using Direct Digital Synthesis (DDS) and Direct Synthesis method. By designing and realizing the local oscillator of radar transceiver in millimeter wave, the feasibility of this system configuration has been proved.In this thesis, by combining the characteristics of DDS, such as high resolution and fast frequency switching speed, with the frequency-conversion function of mixer and multiplier, and making full use of Field-Programmable Gate Array (FPGA) to control the system, this frequency synthesizer has realized the excellent performance in spectrum purity (phase noise and spur level), and frequency-switching speed. In millimeter wave band, the phase noise level is less than -90 dBc/Hz@1KHz, -100dBc/Hz@10KHz, -104dBc/Hz@100KHz, and the maximum frequency-switching time is less than 1μs. The spurious levels at both RF and LO are less than -63dBc, and the minimum frequency step of this radar transceiver is 0.894Hz. The bandwidth is 160MHz.At the end of this paper, we have provided some measures to improve the shortcomings of this frequency synthesizer. Moreover, the configuration proposed in this paper has considerable value for the future research and design work in the frequency synthesizer of millimeter wave radar system.