Voltage Controlled SAW Oscillator (VCSO) Fundamentals

SAW Voltage Controlled Oscillators (VCSO) have been used for many years in telecommunications, military, and commercial applications requiring low phase noise and jitter at fundamental frequencies up to 1000 MHz. They have flown in space, on aircraft, on missiles, and have been a key component in modern telecommunications systems. They use a quartz SAW (Surface Acoustic Wave) delay line as the frequency controlling element. The SAW delay lines are fabricated on a 0.5 mm thick quartz wafer using planar processing similar to that of an IC. The frequency selective aluminum pattern is on the surface of the quartz allowing the delay line to be securely mounted in its package. This construction provides a small and rugged resonant element, that when used in a VCSO, results in very low vibration sensitivity.

VCSOs in many ways can be considered midrange between voltage controlled crystal oscillators (VCXO) and lumped constant voltage controlled oscillator (LC VCO). When there is a need for a high frequency, low noise, small and rugged oscillator, VCSOs should be given serious consideration. This white paper will provide details of just how a VCSO works and design trade-offs that can be made to optimize performance for a particular application.