Two mu-zero resonance (MZR) resonators are etched in the patch of a microstrip antenna. The two MZR resonators generate two new resonances. As the MZR resonances are lower than the microstrip antenna resonance and the resonances merge with each other, size reduction and bandwidth enhancement were obtained. A prototype was designed and measured. The measured impedance bandwidth increased from 640 MHz (5.31-5.95 GHz, 11.33%) of the referenced microstrip antenna (RMA) to 940 MHz (4.99-5.93 GHz, 17.22%) of the proposed MZR loaded microstrip antenna (MZR-MA). Moreover, the patch size is decreased from 0.354λl × 0.283λl of the RMA to 0.332 λl × 0.266λl of the MZR-MA, and unidirectional radiation patterns are obtained for the microstrip patch and MZR resonances. A microstrip line based model was built to analyze the MZR resonators.
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