Many communications and RADAR systems operate at radio frequency (RF) frequencies of Ku Band or higher. In many of these systems it is necessary to continuously monitor and adjust the power level of the transmitted RF signal and the gain of the receiver (or transmitter) in order to compensate for changing link conditions such as atmospheric changes in weather conditions, interference, movement or changes in orientation of the terminals. To accomplish this, RF power levels are sampled using an RF power detector and RF gain or signal levels are adjusted as appropriate.
The output of the power detector is typically a voltage representative of the power of the RF signal. However, there is a square law relationship between power and voltage, given as:P=V2/R  EQ. 1where V is the amplitude of the RF signal and R is the resistance presented to the RF signal. As shown in EQ. 1, as the amplitude of the RF signal increases, the resultant power increases exponentially. FIG. 1 illustrates a graph 5 of a typical power detector response, where the x-axis is power in dBm and the y-axis is the output detector voltage in Volts, labelled VDETECT. As shown in graph 5, VDETECT of the power detector exhibits a generally exponential response to a linear increase in the signal power in decibels per milliwatt (dBm). Therefore, at low power intensities the power detector exhibits very low sensitivity, while exhibiting high sensitivity at high power intensities. The change in output voltage is extremely rapid at higher power outputs, which generally exceeds the ability to properly read the signal, which is preferably constrained to be in the range of 200 mV to 800 mV. What is desired, and not provided by the prior art, is a power detector exhibiting an increased dynamic range with similar sensitivity for both low and high power levels.
USPTO Backgrounds
USPTO Backgrounds