Simple adaptive matching antenna

The performance of handheld wireless devices can be affected when they are held close to parts of the human body. Deterioration can vary from person to person or even different forms or types of use. One of the problems is antenna impedance mismatch in different situations. Reported is an adaptive matching antenna realised by combining a simple monopole antenna and an oscillator with a phase-locked loop (PLL). The PLL helps to monitor return loss and to adjust the matching network automatically. It is found that the antenna can operate in the whole 2.4 GHz ISM band no matter how close it is to the human body after the adaptive matching circuit is applied.