A rectangular slot antenna with perfectly conducting superstrate and reflector sheets for superior radiation in the 6–9 GHz band

Abstract

This paper presents the design and analysis of a rectangular slot antenna for producing a directional radiation pattern over a wide bandwidth of 6–9 GHz. A basic wideband slot antenna is designed for the desired frequency band by microstrip offset feed technique. This antenna is then loaded with a superstrate and a reflector, both made of conducting sheets. Analogous to a three-element Yagi antenna, the superstrate enhances the boresight gain, while the reflector improves the front-to-back ratio (FBR) of the basic slot antenna. The antenna is optimized for superior wideband performance with boresight gain ≥5 dBi, peak cross-pol level ≤−10 dB and FBR ≥10 dB, over the −10 dB impedance band of 6–9 GHz, which in this paper is termed as the radiation bandwidth. Prototype measurement demonstrates a radiation bandwidth of 6.05–8.22 GHz (or 30.41%), which is in decent agreement with the simulation.

Conducting sheets‐loaded slot antenna for high gain and wide 3 dB gain‐band operation

“…The basic rectangular slot antenna (without any conducting sheets in Figure 1) from 18 designed for the 6–8.5 GHz band (Electronic Communications Committee [ECC] UWB band) is used as the starting design element. As detailed in Reference 18, the slot length L slot = 13 mm approximately corresponds to half‐wavelength at the mid‐band frequency. Bandwidth optimization is achieved through adjustments of the slot aspect ratio ( W slot / L slot ) and the microstrip feed parameters ( L f and d ).…”

“…In the present work, a pair of conducting sidewalls is added to the former design and through design optimization, 6–10 GHz operation is enabled with a minimum gain of 9 dBi and a maximum gain of 12 dBi in the band. Although this design modification appears simple and increases the antenna size by ~4%, resulting performance improvement in terms of gain flatness is exceptional compared to 18 . Resulting antenna has a 3 dB gain‐band of 47% which is more than 90% of its own impedance band unlike 18 and most of the existing wideband antennas.…”

“…Although this design modification appears simple and increases the antenna size by ~4%, resulting performance improvement in terms of gain flatness is exceptional compared to 18 . Resulting antenna has a 3 dB gain‐band of 47% which is more than 90% of its own impedance band unlike 18 and most of the existing wideband antennas. In addition, the antenna has smaller size than majority of existing designs 11,15,31–35 and has fabrication easiness due to its design approach based on simple conducting sheets, than those using specialized pattern based designs 17,21,23,24,36 .…”

“…The proposed antenna covers the 6–8.5 GHz band, which is designated as European/Indian ultra‐wideband and also used for the level probing radar (LPR) 30 . The initial design leading to the proposed wideband design is adopted from the authors' own work 18 . It uses an offset‐fed rectangular slot antenna loaded with superstrate and reflector sheets giving an operating band of 6–9 GHz with a minimum gain of 5 dBi and a maximum gain of 10 dBi.…”

“…8 The technique of superstrate loading has been widely used to improve the gain of patch antennas, 9,10 dielectric resonator antennas, [11][12][13][14] and directional slot antennas. [15][16][17][18][19] Superstrate loaded antennas, also known as the resonant cavity antennas produce high gain through multiple reflections between itself and the ground plane through the Fabry-Perot cavity effect. 17,20,21 The cavity if properly designed also enhances the antenna bandwidth.…”