Reseach And Design Of FMCW Radar Material Level Measuring Instrument Transceiver Front-end

With the development of technology, distance detection of radar technology has become an indispensable tool either in industrial production or military applications. So the performance of radar has a direct impact on our awareness of the target distance. For radar, the difference of signal type has a inseparable relationship the performance of radar. Frequency modulation continuous wave radar is widely used because of the advantages such as large time-bandwidth product, very high frequency resolution and the absence of theoretical distance blind. This paper mainly studies the transceiver front-end of the frequency modulated continuous wave(FMCW) radar, including the FM signal source and the receiver circuit portion. The main purpose is to design a high-performance frequency source, so that the output signal has a high linearity, frequency stability, good phase noise and spurious suppression.First in this paper, describes several commonly used methods for how to design frequency modulated continuous wave signal source, introduces a detailed description of the direct digital frequency synthesis(DDS) technology and related theories phase-locked loop(PLL) technology. Simply describes the two methods triangle wave voltage modulating VCO and a loop formed by DDS and PLL. In the end of this part, also analyzes the pros and cons. In the last, we chose the plan which used a phase locked loop circuit consisted by the PLL chip ADF4159 and voltage-controlled oscillator(VCO) to produce a linear frequency modulated continuous wave signal. According to the design requirements of this project, we’ve identified relevant indicators, given design diagram, and designed the circuit schematics, PCB layout and the final physical. Bases on the above, the study designes a K-band chirp signal source, the center frequency is 24.5GHz, and the bandwidth is 1GHz. The receiving circuit part adopts the zero-IF receiver system, also in accordance with the project requirements and actual needs, determines the relevant indicators, designs the basic block diagram and the circuit schematics. In this part, we design a substrate integrated waveguide(SIW)bandpass filter through HFSS to filter the clutter in received signal.In this paper, the design of frequency source is regard as the key point, and used an innovative solution. Instead of using voltage-controlled oscillator modulated by triangular wave voltage signal and DDS+PLL frequency synthesizer. But to use the new pattern PLL chip ADF4159 to design frequency synthesizer, this circuit of this method is simpler, eliminating the DDS part, has lower cost and high degree of frequency control.In the last, this paper summarizes the whole project, analyzes the problem encountered in the testing process.