A dual log detector can be used to measure the reflection coefficient of an antenna, that is, the ratio of reflected to transmitted RF power. Here, two directional couplers are used, one to sense forward power and one to sense reverse or reflected power. Additional attenuation is generally required before applying these signals to the detectors. The AD8302 dual detector has a gain measurement range of ±30dB. Each detector has a recommended input power range for good linearity and temperature stability. Care must be taken in setting the attenuation levels so the reflection coefficient can be measured over the desired output power range. In this example, the expected output power range from the high power amplifier is 30dB, from +20dBm to +50dBm. Over this power range, it is desired to be able to accurately measure reflection coefficients from 0dB up to –20dB. Each of the AD8302's detectors has a nominal input range from 0dBm to –60dBm. In this example, the maximum forward power of +50dBm is padded down (attenuated) to –10dBm at the detector input. So the maximum power at the detector is comfortably within its linear operating range. Also, when the HPA is transmitting at its lowest power level of +20dBm, the detector sees a power of –40dBm, still well within its input range.