Robert W. Weinert

Spectral performance of sapphire dielectric resonator-controlled oscillators operating in the 80 K to 275 K temperature range

This paper reports on the phase noise performance obtained for X-band oscillators using cooled, sapphire dielectric resonators as the frequency-determining element. We report on results obtained using: (1) a TE-cooled, high-order mode resonator purchased from Poseidon Industries exhibiting a loaded Q of 140,000 at an operating temperature of 275 K, and (2) a low-order (TE02) mode resonator fabricated at Westinghouse exhibiting a loaded Q of 350000 at an operating temperature of 77 K. The oscillator sustaining stage designs incorporate GaAs amplifier flicker-of-phase noise feedback reduction techniques as well as a technique that avoids the need for X-band signal amplification altogether. Sustaining stage open loop, flicker of phase noise levels obtained are typically 20 dB below those normally exhibited by GaAs X-band amplifiers.

LiTaO/sub 3/ lateral field resonators

High overtone lateral field resonators, fabricated on -16.5 degrees rotated Y-cut LiTaO/sub 3/ plates, were examined for high-Q operation in the frequency range between 300 MHz and 1000 MHz. QF products of up to 5*10/sup 13/ for unmounted plates and for hard-mounted plates have been measured. The QF product is higher than can be achieved with quartz, and the self-noise levels of these resonators compare favorably with those of the lowest-noise SAW (surface acoustic wave) resonators. The electrode design of these energy-trapped resonators is discussed.<<ETX>>

Are unexpected bulk waves produced by surface wave transducers

It was recently reported that a surface wave transducer could produce a beam of bulk waves whose tangential wave number was twice the fundamental wave number of the transducer; the wave numbers in the transducers electric field are odd multiples of the fundamental. In this investigation it is found that the extra beam comes from mode conversion of rays reflected at the ends of the sample; the beam is not directly generated by the transducer.

Low noise, UHF oscillators utilizing high overtone, lateral-field excitation, lithium tantalate resonators

The design and fabrication of high overtone, lateral-field excitation (LFE), LiTaO/sub 3/ resonators exhibiting unloaded Q values five times greater than those of similar frequency quartz surface acoustic wave (SAW) resonators were reported by R.W. Weinert et al. (1989). Recent improvements of that work with regard to suppression of resonator spurious modes are described, as is the design and performance of low-noise UHF oscillators incorporating the resonators as frequency control elements. Although excellent short-term frequency stability (near-carrier phase noise) performance has been demonstrated, resonator-controlled oscillator initial frequency drift rates are relatively high and appear to be reduced by electrode pattern design modifications made to obtain spurious modes suppression.<<ETX>>

SAW Attenuation in Hydrothermally Grown Single Crystal ZnO

Recently developed rf sputtering techniques have resulted in the heteroepitaxial deposition of ZnO thin films on ordered gold on sapphire. This result has prompted the comparison of propagation characteristics in the film and on a block of single c rystal ZnO. attenuation measurements were made using a standard laser probe technique for propagation in the basal plane which is elastically isotropic. It was found that attenuation varied as frequency squared between 100 MHz to 500 MHz with a value of approximately 1 db/cm at 100 MHz. Both conventional and unconventional surface polishing techniques were used, the latter to insure minimum surface damage. SAW