RF Power Calibration Improves Performance of Wireless Transmitters

Measurement and control of radio frequency (RF) power is a critical consideration when designing a wireless transmitter. High power RF power amplifiers (PA s) rarely operate in open-loop mode (that is, when the power to the antenna is not in some way monitored). External factors such as regulatory requirements on the amount of power transmitted, network robustness, and the need to co-exist with other wireless networks require strong control of transmitted power. In addition to these external requirements, precise RF power control may result in improved spectral performance and may make the power amplifier of the transmitter more energy and cost efficient.

To regulate the transmitted power of the PA , some form of factory calibration of the PA output power may be necessary. Calibration algorithms vary vastly in terms of their complexity and effectiveness. This application note describes how to implement a typical RF power control scheme and compares the effectiveness and efficiency of various factory calibration algorithms for RF detectors with a linear-in-dB transfer function.