Microwave Close Ranging Transceiver Front-end Technology Research

Short-distance target detection technology is a kind of radar technology. It has been widely applied to the military and civil systems. According to the target distance (5~50m), a C-band transceiver for ranging was presented in this thesis. The focus of this work was on designing a C-band frequency-modulated continuous-wave (FMCW) frequency source, a receiver and microstrip antenna.In chapter 2, the advantages and disadvantages of the two ranging waveforms, namely, classical pulsed waveform and FMCW waveform, are compared in terms of the target distance. Since FMCW waveform has not blind distance, it was chosen for the system. And the waveform of the transmitted signals was designed based on the target distance (5~50m).The waveform is triangular FMCW with central frequency at 6GHz, modulation bandwidth 100MHz, modulation period 10μs, step frequency 0.2MHz, and step time 10ns. The theoretical ranging precision is less than 2m with this waveform.To meet the waveform requirements, DDS+Multiplier+Upconverter was used to realize the C-band FMCW frequency source. The tested results show that the designed C-band FMCW frequency source meets the waveform requirements, and its output power is more than 20dBm. However, the spur level was too high in the bandwidth. The receiver used two stages of down conversion. The total gain of receiver is more than 43dB.To meet the bandwidth requirements, a two-layer electromagnetically coupled rectangular microstrip antenna was introduced to the system. The influence of the inset position and the air thickness between the two layers on the impedance, resonant frequency, as well as the bandwidth was investigated. The tested two-layer antenna works at 6.1 GHz with a bandwidth (S11≤-10dB) of about 11%, 8-dBi gain. The 3-dB beamwidth in the E-plane and H-plane is 57o and 70o, respectively.In the end, the system experiments were conducted, and the results show that the system can be used for short-distance ranging.