Wideband microstrip‐fed slot antenna with end‐fire radiation under dual‐resonant modes

Abstract

In this paper, a microstrip-fed narrow slot antenna with end-fire radiation and expanded bandwidth under dual-resonant modes operation is proposed. At first, the open-ended slot radiator is studied and used to effectively suppress all the undesired even-order modes, reduce the antenna size, and form up the end-fire radiation pattern simultaneously. After that, by symmetrically introducing a pair of slot stubs near the electric-field distributions nodal lines of its second oddorder mode, the resonant frequency of second odd-order mode is gradually moved down. As such, the first and second odd modes could be effectively moved in proximity to each other, thus resulting in the improved impedance bandwidth of the slot antenna under dual-mode operation. To validate the predicted results, the proposed wideband microstrip-fed slot antenna is in final fabricated and measured. Both simulated and measured results are derived with good agreement. Measured results indicate that the impedance bandwidth of the slot antenna has achieved an immense enhancement up to about 25.5% (2.43-3.14 GHz). Moreover, the front-to-back ratio (FBR) beyond 6.0 dB has been successfully obtained across the whole operating band for end-fire radiation.

Hybrid lumped‐distributed loading design approach to wideband dual‐mode resonant monopole antennas

“…By incorporating a pair of short stubs near the feed of a dipole, the bandwidth can be enhanced, but at the cost of high cross‐polarization level due to the radiative stubs 6–8 . In order to circumvent the cross‐polarized radiations and maintain multi‐mode resonant wideband characteristic, slotline stubs, 9–15 short‐circuited strips 16 and branch metallic stubs 17,18 can be incorporated to the E‐field/E‐current nodes of the high‐order resonant mode. In those manners, the resonant modes can be flexibly perturbed to yield wideband operation on demand, while the stubs and strips rarely lead to significant spurious radiations, owing to their length of about one‐quarter wavelength.…”