A Miniaturized Frequency Reconfigurable Antenna With Single Bias, Dual Varactor Tuning

Frequency reconfigurable antenna designs often suffer from limited tuning ranges and complex bias networks. This paper describes a dual varactor-tuned miniaturized antenna with a single bias introduced through the RF feed that addresses these challenges. The dual varactors provide a large tuning range (410-990 MHz, 2.1-3.5 GHz; VSWR = 2:1), while the single bias voltage applied to both varactors greatly simplifies the bias network. The introduction of the bias through the RF feed eliminates the need for separate bias lines. As a result, when the electrical size of the antenna is decreased through tuning, undesired bias line coupling and radiation effects are nonexistent. The design highlights the radiation efficiency limitations associated with the desirable planar topology for electrically small antennas with very wide tuning range requirements. An overview of the antenna's geometry and operation is presented along with detailed measurements to characterize its performance.