Performance of dielectric resonator oscillator for spacecraft transponding modem

A new Spacecraft Transponding Modem (STM) is being developed for deep space communication applications. The STM receives an X-band (7.17 GHz) uplink signal and generates an X-band (8.4 GHz) and a Ka-band (32.0 GHz) coherent or noncoherent downlink signals. The STM architecture incorporates three miniature dielectric-resonator-oscillators (DRO). These DROs are used in receiver and exciter frequency synthesis phase-locked loops (PLL) in the STM. The DROs are designed with custom developed monolithic microwave integrated circuit (MMIC) negative resistance oscillator chips. DROs are laid out on alumina substrates in RF cavity fixtures of 18 mm×18 mm×8 mm. The receiver and the exciter DRO designs meet the following requirements: frequency stability of ±2 ppm/°C, the free running single-sideband phase noise of -50 dBc at 1-kHz offset frequency, tuning linearity of ±10% over the ±1.75-MHz locking range, and output power of +10 dBm±1 dB over a design temperature range of -55°C to +85°C. The phase-locked loop DRO frequency synthesizers are designed using sampling downconverter and phase detector MMIC chips. These PLL frequency synthesizers meet the following requirements: pull-in range of ±1.75 MHz, loop noise bandwidth of 100 kHz, and a single-sideband phase noise of -144 dBc at 1-kHz offset frequency