Dual-band microstrip antenna using capacitive loading

A novel technique for obtaining a single-layer single-feed dual-band microstrip antenna loaded with narrow slots and chip capacitors is proposed and demonstrated. By embedding a pair of slots of proper lengths close to the radiating edges, the rectangular patch has been shown to realise dual-band broadside radiation. The range of the frequency ratio (FR) can be extended to 1.25 by using chip capacitor loading across the narrow slots to produce further capacitive loads. Simple semi-empirical formulas for the two operating frequencies have also been obtained. Dual circular polarisation (CP) radiation for a global positioning satellite (GPS) application using four slots and four chip capacitors on a square patch is also demonstrated. Details of the antenna design and experimental results are presented.