Two-Port Millimetre Wave Oscillators and Their Stabilisation with Phase-Locked Loops.

Available from UMI in association with The British Library. New two-port Gunn oscillator designs which are suitable for phase-locking are reported. The oscillators employ the cap resonator mounted in rectangular waveguide. InP and GaAs devices are used, operating in the fundamental and the second harmonic mode respectively. The bias tuning of the InP oscillator is investigated and used to stabilise it in a phase-lock loop at 88 GHz. The tuning of the GaAs harmonic-mode oscillator is achieved by an alternative method using a varactor tunable cavity coupled to the fundamental circuit by the Gunn device bias line. A small portion of the fundamental power is extracted to drive the phase-lock loop (PLL) monitor. This enables the phase-locking to be implemented at 35 GHz for a main output frequency of 70 GHz. The PLL stabilisation system described is a heterodyne arrangement which uses a thermally controlled VHF crystal reference source. Effective noise reduction is achieved by suitable selection of the loop parameters. Aided acquisition of lock is essential and the methods used to achieve this are described.