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Abstract-A microstrip monopolar patch antenna with shorting vias in the circular patch and coupled ring for bandwidth enhancement is proposed. The bandwidth of the proposed antenna with shorting vias in the annular coupled ring is over 40% wider than that of the antenna without shorting vias in the annular ring. The proposed antenna provides a wide bandwidth because of four resonant modes, including the TM 01 mode of the circular patch, TM 01 mode of the coupled annular ring, TM 02 mode of the circular patch, TM 02 mode of the coupled annular ring. These modes can generate an omnidirectional pattern in the azimuth plane like a monopole antenna. A prototype was fabricated to confirm the simulation verdictions. Measured results show that 10-dB return loss bandwidth of 38.4% from 4.42 to 6.52 and average gain of 5 dBi acrossing the operating band are achieved for the proposed antenna with a low profile of 0.027 wavelength.

This paper presents a compact wide stop band bandpass filter using loaded feeding structure to enhance the out-of-band performance. The filter is constructed by three shorted parallel coupled stepped impendence resonators(SIRs), and is fed by tapping microstrip lines with open stubs loaded. The three order bandpass filter effectively suppresses the spurious pass band so that it has a so wide stop band. Measured results accord well with the simulated results, showing good performance of the filter.Index Terms -SIR filter, wide stop band, feeding structure, harmonic suppression.

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