To meet the specifications of future radar and communication system we developed a low phase noise microwave oscillator. This feedback oscillator consists of a commercial MESFET-amplifier at room temperature and a LaA103 dielectric resonator with high temperature superconducting (HTS) shielding at 63K. The resonator operating at a resonance frequency of 5.6GHz showed unloaded quality factors in the 10' to lo6 range. BY means of a strong resonator coupling (IS~lk6dB) and an amplifier gain of 20dB we obtained an output power of +15dBm. The phase noise L(fm) of the oscillator was below the detection limit for offset frequencies beyond 10kHz. For offset frequencies below 5kHz measurements revealed perfect Lvm)=f,"-behaviour according to the Leeson model. The phase noise was -1lOdBdHz at lkHz offset and -130dBdHz at 1OkHz. This phase noise performance is superior to state of the art SAW-or quartz oscillators for f,>lOkHz. To further reduce the phase noise performance close to the carrier we investigated the implementation of a phase locked loop (PLL).The long term temperature stability of the oscillator frequency can be enhanced by introducing a central cylinder made from rutile (Ti02). We will present numerical and experimental results on this compensation.
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