back ratio larger than 3 dB and this value is sufficient for a GPR where the lack of any reflecting ceiling is assumed.In order to complete our experimental characterization and to catch a glimpse of the radiation pattern in the 3D space, we report also the measured diagrams in the yz plane. Figures 6(a) and 6(b) show the measured diagrams for frequencies above and below 800 MHz, respectively: as it can be expected from the knowledge of the radiation diagram of a bow-tie, there is no radiation along the y axis. We observe that in this plane the agreement between the experimental and numerical findings is exceptionally good for all the frequencies taken into account and the gain reaches its maxima around 195 and 295 . CONCLUSIONWe have proposed a planar bow-tie antenna with a structured ground plane whose radiative characteristics are well-suited for wide band pulsed radar working in the 500-1600-MHz band. The directivity is augmented by shaping the ground plane that acts as a reflector; the electronic RF front-end of the radar and the antenna can share the same ground plane and the bow-tie feeding based on a coplanar stripline makes our layout fully compatible with the differential output of a RF chip. Although the maximum gain of the prototype oscillates between about 2.5 and 1 dB in the 800-1600-MHz frequency range, the gain can be lower than 25 dB in the 500-800 MHz range, nevertheless, the antenna can be used over the whole proposed bandwidth thanks to the reflection coefficient below the 210-dB level which guarantees an acceptable working condition for the RF front-end. Obviously, among the major benefits of the proposed planar antenna, in comparison to other antennas used for through-wall and GPRs, there are its low cost and compatibility with mass production.ABSTRACT: In this article, a compact and small coplanar waveguide fed (CPW-fed) monopole antenna is proposed for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. In the proposed antenna, the main target is to present a compact structure with a step-by-step design procedure on the patch. The antenna consists of a slotted rectangular patch as radiator, a partial CPW-ground plane. To excite WiMAX/WLAN bands, two Fshaped slits are inserted into the rectangular patch that resonates at the frequencies of 3.5 and 5.4 GHz. By suitable adjusting the lengths of the F-shaped design, much wider impedance bandwidth can be produced, especially at the lower band of WLAN/WiMAX. The size of the antenna is 15 3 15 3 1.6 mm 3 . A prototype of the designed antenna is constructed and experimentally investigated. The 210 dB S 11 bandwidths of them are (3.15-4.63 GHz) and (4.75-6.62 GHz), respectively, which can cover both the WLAN bands GHz) and the WiMAX bands (3.4-3.6 GHz and 5.25-5.85 GHz). Proper omnidirectional radiation pattern characteristics and enough gains are obtained over the operating bands.

In this letter, a planar antenna with band‐notched characteristic is designed for ultrawideband application.Distinctive features of this antenna in comparison with the other reported antennas are the compact dimensions and omnidirectional radiation across the whole band of operation using slotted conductor‐backed plane. The ground plane is located at the bottom layer, which also includes a Γ‐shaped conductor‐backed plane used to widen the impedance bandwidth. Also, band‐notched characteristic is achieved by a Γ‐shaped form inside the slotted conductor‐backed plane. The measured results of the manufactured (18 × 18 mm2) antenna on 0.8‐mm FR4 substrate show that the antenna operates with VSWR less than 2 over the frequency band from 3.05 to 12.9 GHz, except a frequency notched band of 3.3–4.3 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2237–2241, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27063

A simple rectangular monopole antenna with dual bandnotched characteristics is proposed. The main features of the antenna are the compact dimensions and omnidirectional radiation across the whole band of operation. Dual band-notched characteristics are achieved by two pair of mirror inverted L-shaped slots at the two sides of the radiator. The measured results show that the proposed antenna operates over the frequency band between 2.5 and 11.9 GHz (131%), defined by VSWR < 2, except two frequencies notched bands of 3.25-4.25 GHz and 5.1-6 GHz. The designed antenna has a small size of 12 Â 14 mm 2 . Experimental and simulated antenna results show that the proposed antenna has a desirable VSWR level, radiation pattern, and gain characteristics for ultrawideband frequency band range.