FREQUENCY-VARIABLE ANTENNA AND COMMUNICATION DEVICE HAVING THE SAME

摘要

A radiation electrode (2), which acts as a monopole antenna, is shaped in such a loop that an open end (2K) of the radiation electrode (2) is opposed to a power supply end (2Q) thereof with a spacing therebetween. A frequency-variable circuit (3) is provided on the loop path of the radiation electrode (2). The frequency-variable circuit (3), which has a reactance component and a portion capable of varying the reactance component, uses the variable reactance component to vary the electrical length of the radiation electrode (2), thereby varying the resonance frequency of the radiation electrode (2). The provision of the frequency-variable circuit (3) on the loop path of the radiation electrode (2) can vary the resonance frequency of the radiation electrode (2), while maintaining an excellent matching between the radiation electrode (2) and the circuit side of a communication device (i.e., suppressing the degradation of the gain). The variability of the resonance frequency of the radiation electrode (2) in accordance with a frequency required for a communication allows the frequency-variable antenna (1) to have a wider bandwidth than the radiation electrode (2) itself.