Radio Frequency (RF) Stability Explained

Radio frequency (RF) stability refers to the variation in the frequency of a signal source or device that generates a frequency. This variation is often caused by changes in temperature or the passage of time. It’s typically measured in parts per million (ppm).

The frequency drift of the local oscillator, synthesizer, or reference oscillator is a key factor determining the overall frequency stability of an RF transmitter or receiver. The smaller the frequency drift, the better the system’s performance.

Short Term vs. Long Term Frequency Stability

There are two primary ways to characterize frequency stability:

• Short Term Frequency Stability: This refers to the stability of an RF system over a shorter period, typically measured in days. For example, a specification might state that the short-term frequency stability of an RF up-converter is 0.001 ppm/day, or $1 \times 10^{-6}$ over a temperature range of 0°C to 50°C.

• Long Term Frequency Stability: This refers to the stability of an RF system over a longer period, usually measured in years. For example, a specification might state that the long-term frequency stability of an RF up-converter is 0.1 ppm/year, or $1 \times 10^{-7}$ per day for an RF transceiver.