Low phase noise microwave oscillators based on HTS shielded dielectric resonators

Abstract

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.

Microwave properties of tuneable TE01deltamode sapphire-loaded cavity resonators with YBa2Cu3O7-deltaendplates

“…Microwave technologies based on high temperature superconductor (HTS) films have been proved useful in realizing devices with high performance, which include oscillators with extremely low phase noise [1] as well as filters with very small insertion loss and high power handling capability. Tuneable microstrip resonators based on a YBCO microstrip and SrTiO 3 (STO) have been studied by many researchers, where the dependence of the dielectric constant of STO on the applied electric field is used for changing the resonant frequency (f 0 ) [2].…”

Applications of coupled dielectric resonators using SrTiO/sub 3/ pucks: tuneable resonator and novel thermometry

“…Mechanically adjustable elements within the resonator housing have also been used to provide tuning (see, for example. [ 5 ] ) . When the highest stability is required mechanical adjustment has the disadvantage that the mechanism will almost certainly be prone to vibrational instabilities.…”