Ground radiation antenna utilizing characteristic mode theory

摘要

This article presents two ground radiation antennas with simple feeding structuresfor mobile applications. Characteristic mode theory is exploited to design the proposedantennas. For antenna 1, a small loop without any lumped elements is usedas the feeding structure. And the total length of the feeding loop is only 20.2 mm(0.06 λ_(0.9GHz)). The operating band of the proposed antenna 1 is 834-1020 MHz.Across the whole operating band, the measured efficiencies of antenna 1 arehigher than 72%. In addition, a new method to generate an extra resonant frequencyis proposed, which has little effect on the existed resonant modes at thelower band. The dual-mode antenna 2 without loading any lumped elements isobtained by implementing this method, which covers 812-940 MHz and1543-1576 MHz bands. Furthermore, the new resonant frequency can be controlledindependently. Namely, the higher frequency band of antenna 2 can beadjusted freely without changing the lower band. To validate the design strategy,two ground radiation antennas are fabricated and measured. The measuredresults indicate that the proposed antennas are suitable for mobile terminals.