Minimization on power loss and distortion in a tuning circuit for a mobile terminal antenna

Abstract Broadband tuning circuits of small antennas may have high power losses and/or high distortion if the designer does not pay attention to the placement of the lossy and nonlinear components in the circuit. In this paper, experimental results of the distortion of an SPDT HEMT switch under different impedance environments are presented. The results motivate a broadband frequency tuning circuit design for a mobile handset antenna. The tuning circuit, using HEMT switches and lumped reactances, compromises between reasonable power loss and distortion caused by the switching components. The design is simulated and prototyped for E-GSM900 and GSM1800 using a capacitive coupling element based antenna.

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