Specifying Upper Bounds on Phase Noise in Phase-Locked Oscillators in Electronic Warfare Systems–Part I [Application Notes]

The purpose of this article is to present simple relations that allow one to find the upper bound on the phase noise of a phase-locked oscillator (PLO), its frequency stability, mean-square incidental phase noise modulation (Φ²) and phase jitter. Simple closed-form equations are derived that are not intend ed as design tools, but are intended to establish upper limit specifications for the phase noise levels of PLOs used in wideband electronic attack (EA) and electronic warfare (EW) systems. A block diagram of a hypothetical system is used to illustrate how an EA system is susceptible to degradation due to phase noise of PLOs. This part presents a technique to model the phase noise spectral density of a manufacturer's PLO. Based on the manufacturer's specifications, the model allows the prediction of the total phase noise, phase jitter and predicted frequency uncertainty (Allan Variance) of the PLO considered. Part II (to appear in the February 2012 issue of IEEE Microwave Magazine) will present a technique to calculate the common-mode coupling of the oscillator phase noise into the following intermedi ate frequency (IF) section of a mixer. The coupled noise may increase the noise figure of a receiver. A method to estimate the increase in phase noise due to vibration will also be presented. Some basic definitions and performance characteristics are described in "Performance Metrics for Electronic Warfare Receivers".