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Wideband planar monopole antennas have recently been proposed for use on digital mobile terminals. The square planar monopole is the simplest to analyze, and suffers little degradation of radiation pattern within the impedance bandwidth. The addition of a bevel on one or both sides of the feed probe is shown to increase the bandwidth with good control of the upper edge frequency. The impedance bandwidth ratio for this antenna is shown to vary from 2:1 to 6:1, which can be controlled by beveling the planar geometry. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 229–232, 2001.

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Abstract-A dual-band antenna with right-hand circular polarization for the first frequency and the counter polarization at the second frequency is realized with compact printed spiral slots. The coupled spiral slots are fed by a 50 Ω microstrip line. Dual-sense circularly-polarized performance is achieved by realizing oppositely-directed current rotation for the two frequency bands. A parametric study shows that the additional slot significantly improves the bandwidth for both frequency bands. Measured results show that the fractional impedance bandwidth is greater than 18% for both bands. The 3 dB axial-ratio bandwidths are 4.5% and 3.5% for the RHCP and LHCP bands, respectively.

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This paper describes a printed rectangular-plate monopole, fed by microstrip line.The effect of varying plate width, feed-gap height and feedline width on the impedance bandwidth is examined. It is shown that for a fixed ground-plane size, that optimisation of these parameters can yield an impedance bandwidth ratio of 4.3:1, without using any broadbanding techniques.