Research And Design Of L-band TWDR RF Front-end

Through-the-wall Detecting Radar（TWDR）can penetrate a certain thickness of non-metal wallor other obstacle to find hidden target which behind it. Thus, they have been widely applied to the lawenforcement of public security, urban warfare, earthquake relief work, security and other fields. In thisthesis, we study and design through-the-wall radar RF front-end, including ultra-widebandArchimedean spiral antenna, L-band stepped frequency source and transceiver channel, which act asthe main components of the RF front-end.The work of this thesis content and innovation points include:1. TWDR system analysis and design: Based on TWDR working principle, we choose theirsystem works and determine system specifications. Then, we analyze indicators of system anddetermine the RF front-end and its main comments’ technical indicators.2. The design of ultra-wideband Archimedes spiral antenna: The simulation and design ofArchimedes spiral antenna with a regular balun, but its longitudinal size is larger. Therefore, to realizethe miniaturization structure, we improve the balun. At the same time, in order to obtain a one-wayradiation, antenna reflective cavity is designed. Then, we produce and measure this miniaturizedcavity-backed Archimedes antenna. In the wide frequency range of0.8~3GHz, VSWR of the antennaare located two or less, the maximum gain of the antenna is7.7dBi@2.2GHz. The test results andsimulation results are basically consistent.3. The L-band (1~2.024GHz) step frequency source design: According to the analysis ofTWDR system, we determine the step frequency source using PLL techniques. Under the conditionsgiven specifications, we select each chip of the step frequency source: Reference Crystal is DAPUCommunication Technology Co., Ltd. of temperature-compensated crystal oscillatorT10A-BSBN-10.00MHz,lock-chip is ADI company’s ADF4106, voltage-controlled oscillator andpower amplifier are respectively selected Mini-Circuit’s ROS-2150VW and ERA-4SM+.Consideringthe output frequency point is128, so we choose a representative four frequencies (1GHz,1.312GHz,1.712GHz,2.024GHz) for testing. Measured results of the step frequency source: output power arebetter than10dBm, the phase noise are less than-85dBc/Hz@1kHz, lock time are less than150us,spurious suppression are better than50dBc. Experimental results are better than the proposedtechnical indicators.4. Transceiver channel research: We study the implementation of through-the-wall radar RF frontend transceiver channel in detail. Because intermediate frequency is very low only1.25MHz, so the superheterodyne structure of transmitter can’t eliminate the mirror-frequency interference by. We usethe direct transformation of orthogonal modulation transmitter structure, and simulate it by the Agilentcompany’s simulation software ADS. Meanwhile, we use classic superheterodyne structure to realizereceiver and adopt the AppCAD simulation software to the link budget. Finally, the design of thetransceiver channel schematic diagram and PCB layout.