Improved oscillator phase noise characteristic under harsh environmental conditions by use of mechanical filters

Airborne radar and navigation transceivers require much improved spectral purity under very harsh environmental conditions. The use of mechanical filters, thereby partially isolating the quartz resonator from the perturbing random vibrations and acoustic noise, improves the performance loss of the oscillators. The initial results presented during the 1989 NEUCHATEL (Switzerland) and DENVER (USA) Symposium by L. Bidart, E. Girardet and P. Renoult in the article entitled “Mechanical and acoustic effects in low phase noise piezoelectric oscillators” have to be enhanced and confirmed with a series of new designs and tests. These tests allow comparative phase noise measurements under vibration between oscillators with and without mechanical filters. Comparisons were made of various types of crystal oscillators : XO, TCXO, VCXO and OCXO in various size packages