P-Band Frequency Synthesizer for Airborne Synthesis Aperture Radar

This paper describes the design, development and characterization of a microwave P-band frequency synthesizer for airborne synthetic aperture radar applications. The frequency synthesizer uses a direct frequency multiplication technique using a temperature compensated crystal oscillator (TCXO) as a source to generate multiple signal coherently. The signals generated by the frequency synthesizer are a 50 MHz reference signal from TCXO, a clock signal of 250MHz, 2 nos. of 450 MHz local oscillator signal and a linear frequency modulated (LFM) signal of $450 \pm 25 ~\mathrm{MHz}$. The LFM signal is synthesized by quadrature modulation of 450 MHz signal with modulating chirp input of 25 MHz bandwidth. The modulated transmit chirp signal exhibits side band suppression of $\gt20 \mathrm{dBc}$ and frequency response of $\lt \mathrm{2} ~\mathrm{d B}$ over the operating temperature range of $-10^{\circ} \mathrm{C}$ to $55^{\circ} \mathrm{C}$. The in-band and out-of-band spurious signals are $\gt20 \mathrm{dBc}$ and >40dBc, respectively. The frequency synthesizer is realized using microwave integrated circuits using space hardware development guidelines.