Automatic impedance matching of an active antenna near the human operator by the steepest gradient algorithm

摘要

An automatic impedance matching technique for a normal mode helical antenna near the human operator has been investigated. The helical antenna incorporating varactor diodes for changing impedances maintains a good matching condition regardless of the distance between the helical antenna and the operator. This eliminates a power loss caused by the impedance mismatch due to the human body. The technique makes use of the steepest gradient algorithm that can achieve an adaptive control on impedance condition. An experiment has been made with regard to stability and convergence time of a control system by connecting the helical antenna and a microprocessor.