A radio frequency (RF) detector is a device used to detect the presence of RF waves either in a wireless or wired (on RF Cable) physical transmission medium.  They are also known as RF power detectors or RF responding detectors and are available as devices or modules. RF Detectors can also refer to professional test products intended for the monitoring of signals or noise on a physical medium. They are used to test if equipment is working properly and for the presence of interfering signals. They can also be used to detect the presence of surveillance devices as part of a counter surveillance strategy.

RF power detectors are available in several types. They are useful in RF circuits and systems for detecting the transmit power level of the RF signal in a particular band. These are usually specified to operate over a dynamic range and a frequency spectrum band. They can be used to determine the Received Signal Strength Indicator (RSSI) level of a signal. They usually specify a typical response time to obtain an accurate power level and can incorporate envelope detection and tracking. There may be a requirement for external components to band limit the signal (selectivity) so that a specific, narrow portion of the bandwidth can be evaluated.

RF power detectors are used in applications like Wide-band Code Division Multiple Access (WCDMA) or other CDMA modulation links. They typically output an RMS power level and can be used as log-> Root-mean-square conversion for RF signals. Monitoring the signal strength and associated RSSI also provides improved efficiency of a transmitter by control of transmitter amplification power. Receivers can use these as part of their Automatic Gain Control (AGC) loop.