System simulation of low power FMCW-based X-band weather radar

Abstract

This paper presents the simulation system of low power X-band weather radar based on frequency-modulated continuous-wave (FMCW) signal. The system uses a chirp baseband signal which 10–60MHz up-chirp signal and 60–10MHz down-chirp signal which is generated using Direct Digital Synthesizer (DDS) of AD9850 with 125MHz clock rate. The baseband signal is up-converted at X-band using a mixer with 9.035GHz Voltage Controlled Oscillator (VCO) to be transmitted at frequency of 9GHz. The system uses a bandpass filter (BPF) made of lumped elements to eliminate spurious signals produced by the DDS at the transmitter, and a lowpass filer (LPF) at the receiver. The system also uses a microstrip BPF of Square Loop Resonator (SLR)type as RF filter for X-band frequency. The results show that the system has 10–60MHz bandwidth for baseband signal with 10MHz cut-off frequency for LPF, while RF filter has the bandwidth response of 49MHz at the center frequency of 9.0015GHz.