A Mismatch Detector for Adaptive Antenna Impedance Matching

The efficiency of a mobile phone's power amplifier suffers from the antenna impedance mismatch caused by the body-effect of its user. A mismatch detector used for an innovative antenna matching algorithm which is based on adaptive correction of the reactive part of the antenna impedance mismatch has been designed, implemented and measured. The mismatch detector which consists of a wideband 90deg phase shifter, a limiter and a Gilbert-cell multiplier detects the phase of the reflection coefficient. The dynamic range of the mismatch detector is up to 142deg at the standard GSM frequencies (900MHz, 1800MHz and 1900MHz) for input power not less than -20dBm. This mismatch detector fulfills the function of determining the mismatch property according to the presented adaptive antenna impedance matching algorithm