TEMPERATURE COMPENSATED GAPO4 RESONATORS WITH Q FACTORS HIGHER THAN 10 MILLION AT 6 MHZ

摘要

Thickness shear resonators (6 MHz, fundamental mode) made of gallium orthophosphate (GaPO_4) crystals with a cut angle near Y-84° and a very low coupling have shown very high Q factors [2], thus it is called HiQ cut. The properties of some new HiQ resonators are investigated by a passive (HP network analyzer) and an active (oscillator) measurement method. The motional resistances of HiQ resonators are several kΩ at normal pressure conditions but decrease to several hundreds of Ω under vacuum conditions. Q factors between 5 and 6 million are obtained at a pressure of about 0.07 mbar with the active method and up to 13 million at 0.04 mbar with the passive method. Since high Q factors promise low phase noise, further investigations are focussed on the short time stability.