Three Millimeter Wave Rcs Measurement Radar Front-end Key Technologies

Radar Cross Section (RCS) means the ability of scattering electromagnetic wave of a target. As the rapid development of the current military technique, like stealth aircraft and Electronic warfare, RCS becomes more and more important when evaluating the characteristics of these military equipments. And the RCS measurement in 3mm-wave becomes necessary around the world because of the progressing technique. As an important component of RCS measurement system, the development of radar front-end deeply influences the progress of RCS measurement technique.In this dissertation, 3mm-wave radar front-end technology is analyzed in detail, including 3mm-wave receiver technology and 3mm-wave phase-locked oscillator (PLO) technology. Based on these technologies, 3mm-wave digital PLO with two loops and receiver with low noise, high gain and large dynamic range are fabricated. In the microwave PLO, the reference signal is compared with a VCO of C-band.The output of the VCO becomes the LO input of the harmonic mixer, while the 3mm-wave VCO is the RF signal. Then the reference signal is compared with the IF signal, and then the 3mm-wave VCO is phase locked. The measured results of the microwave PLOs show that the phase noise is up to -96.5dBc/Hz at 10 kHz offset from the carrier, the spurious is lower than -79dBc with the output power over 13dBm at 4.6GHz and 4.68GHz. The results of the millimeter-wave sources show that output power is over 11dBm at 93.32GHz with the spurious lower than -70dBc and the phase noise up to -67.83dBc/Hz at 10 kHz offset from the carrier. In order to enlarge the measurement range of the system, a phase-coherent controlling circuit is designed for the PLOs in transmitter and receiver, and this circuit can work in the situations of phase-coherent or non-phase-coherent.In the design of the receiver, an improving model of waveguide to microstrip transition using antipodal-finline is proposed for 3mm-wave LNA, and it is validated in back-to-back experiment. The result of the back-to-back transition shows that the return loss is lower than -15.83dB. Furthermore, a gain-controlling circuit is used for ensuring the receiver to work effectively at long-distance and short-distance states. The IF module of the receiver has 83dB gain at long-distance state and 57dB gain at short-range state, and the noise figure is 1.51dB at long-distance state.