Study Of K-band FMCW Radar System Components

Along with the more developed algorithm technology、chip devices and gradually opened frequency band, millimeter radars have been getting more and more applications in many fields, such as target recognition, flight navigation, ship and automotive anti-collision. FMCW radar systems use linear frequency modulation microwave signal to calculate distance and angle of the target. Because of its advantages of high resolution, simpler algorithm, all-weather operations and smaller size, microwave and millimeter-wave FMCW radars have received more and more attention in many fields. As one of the most important part of an anti-collision radar system, FMCW frequency synthesizer has been widely studied and produced in recent years. The research of FMCW frequency synthesizer on miniaturization, low power consumption and high performance has important engineering significance and social value.The main content of this paper is divided into two parts. In the first part, a Ku-band frequency synthesizer using PLL loop extrapolation mixing scheme is produced as the local oscillator source of a K-band radar system on the basis of analysis of the main advantages and disadvantages of several frequency synthesizer architectures, which mainly focus on the phase noise and spurs. The realization of the proposed frequency synthesizer uses many technologies, such as PLL、DDS and mixer. Measured results show that the proposed system operating in 13GHz~14GHz achieves the goal that the phase noise of output signal lower than-85dBc/Hz@10KHz 、spurious suppression higher than 30 dBc and power flatness less than 1dB.A K-band sub-harmonically pumped image rejection mixer based on GaAs pHEMT process is designed in the second part of this paper. At first some commonplace MMIC components and their models are presented. After that, the basic structure of sub-harmonically pumped image rejection mixer and operating principle are discussed. Finally, the principle and detail design procedure of the mixer and EM simulation results are presented. The image-reject mixer uses the second harmonic signal of the local oscillator as local reference signal to produce IF signal. Simulation results show the mixer designed in this paper achieves conversion gain of about 11 dB, image rejection better than 25 dB, noise figure less than 22 dB, isolation better than 30 dB, input P1 dB better than 4dBm for RF frequency from 25GHz-31 GHz.