Dbf Radar System Rf Components And Calibration Network

As a front-end component of a digital beamforming (DBF) radar system, the performances of a Radio Frequency (RF) tranmint and receive (T/R) module play a key role in Radar capabilities, such as range, sensitivity, anti-jamming, etc. In addition, the size of T/R module in a DBF radar should be limited to accommodate the requirements of the system. The consistency of all T/R modules in DBF radar system is also an important role, which guarantees the performances of the system. Therefore, the good calibrating network should be considered in the design. In this thesis, a RF front-end T/R module has been investigated. Furthermore, the calibrating network has been designed. The main work has been included in the following:1) T/R module:In the design, the superheterodyne receiver has been used to downconvert the RF singlal to the IF frequency. And the linear working mode is applied in the transmitter. The RF port and two local singals are co-used by the receiver and transmitter. Through the SPDT, the transmit and receive modes have been switched at difference time. The appropriate components have been chosen through the analysis of the system requirements. In the structure, the transmitter and receiver have been arranged at two layers. With careful design, a compact structure is achieved. The size of T/R module is 120mm×50mm×50mm. The simulated results have been given with the help of the theoretic method and the commercial software ADS. In the simulation results, the gain of the receiver is 60.2dB and the noise figure is less than 4dB, the maximum transmit power is 1W, and all the spuriouses can be suppressed to less than-50dB. They are all accommodated the requirements of the system. This T/R module has been manufactured and measured. In the measured results, the gain of the receiver is 59.6dB and the nosie figure is 3.8dB, the maximum transmit power is 28.4dBm (0.7W), and the spuriouses are suppressed to less than-50dB.2) Calibrating network:The calibrating network based on the Wilkinson divider is designed in this thesis. Firstly, the 2×2 sub-networks which designed on two different thick dielectric boards have been designed to investigate the effect of the dielectric board. Through comparison, the network on the thin dielectric board has the good performances. Then this sub-network on the thin dielectric board has been measured in difference times to test the stability:the variation of amplitude is less than 0.1 dB RMS and the variation of phase is less than 2°RMS in the center frequency. In the working bandwidth, the variation of amplitude is less than 0.3dB and the variation of phase is less than 5°. Furthermore, the 10×10 calibrating network is designed and manufactured in this thesis.