Vibration Sensitivity of Microwave Components

Vibration sensitivity is an important specification for oscillators on mobile systems, unmanned aerial vehicles (UAVs) etc. These systems must provide superior performance when subject to severe environmental conditions. Electronic oscillators often can provide sufficiently low intrinsic phase modulation (PM) noise to satisfy particular system requirements when in a quiet environment. However, mechanical vibration and acceleration can introduce mechanical deformations that degrade the oscillator´s otherwise low PM noise. This degrades the performance of an electronic system that depends on this oscillator´s low phase noise. Not only an oscillator, but most microwave components, such as microwave cables, circulators, and amplifiers are sensitive to vibration to some extent. Therefore, it is very important to select vibration-tolerant components in order to build a system with less vibration sensitivity. We study the performance of different microwave cables (flexible, semi-rigid as well as rigid) under vibration for different vibration profiles. Some good cables provide a vibration-sensitivity noise floor that provides sensitivity of 10^-11-10^-12 per g for an oscillator under test. We also verify the reproducibility of each measurement after disassembly and reassembly. We study the vibration sensitivity of a SiGe amplifier-based surface transverse wave (STW) oscillator and an air-dielectric cavity resonator oscillator (ACRO) and compare their performances with a commercially available dielectric resonator oscillator (DRO). We also describe passive and active vibration cancellation schemes to reduce vibration induced noise in oscillators.