Electronic full-space scanning with 1-D fabry-pérot LWA using electromagnetic band-gap

A novel mechanism to obtain full-space electronic scanning from a half-space scanning one-dimensional (1-D) Fabry-Pérot (FP) leaky-wave antenna (LWA) is proposed and experimentally demonstrated in this letter. By using a central feed that divides the structure into two independently controlled leaky lines, one each side, and making use of the electromagnetic band-gap (EBG) region of the FP resonator, the antenna can be electronically tuned to operate in three different regimes: backward scanning, forward scanning, and broadside radiation. Leaky-mode dispersion theory and experimental results of a fabricated prototype demonstrate a continuous electronic scanning from-25° to +25° at 5.5 GHz. © 2011 IEEE

Adaptive Antenna Arrays for Ad-Hoc Millimetre-Wave Wireless Communications

New technologies that employ millimetre-wave frequency bands to achieve high speed wireless links are gaining more attention (Dyadyuk et. al., 2007, 2009b, 2010a; Hirata et. al., 2006; Lockie & Peck, 2009; Kasugi et. al., 2009; Wells, 2009) due to increasing demand for wideband wireless communications. Very wide uncongested spectrum is available in the E—bands (71-76 GHz and 81-86 GHz) recently allocated for wireless communications in USA, Europe, Korea, Russia and Australia. The E-band provides an opportunity for line-of – sight (LOS) links with higher data rates, well suited for fibre replacement and backhaul applications. Future mobile and ad-hoc communications networks will require higher bandwidth and longer range. An ad-hoc or mobile (e.g. inter-aircraft) network that relies on high gain antennas also requires beam scanning. Adaptive antenna arrays have found a wide rage of applications and are becoming essential parts of wireless communications systems (Abbaspour-Tamijani & Sarabandi, 2003; Do-Hong & Russer, 2004; Gross, 2005; Guo, 2004; Krim & Viberg, 1996; Mailloux, 2005, 2007; Rogstad et al., 2003; Singh et al., 2008). While the spectrum available in the millimetre-wave frequency bands enables multi-gigabit-per second data rates, the practically achievable communication range is limited by several factors. These include the higher atmospheric attenuation at these frequencies and limited output power of monolithic microwave integrated circuits (MMIC) (Doan et al., 2004; Dyadyuk et al., 2008a; Kasper et al., 2009; Floyd et al., 2007; Reynolds et. al., 2006; Vamsi et. al., 2005, Zirath et al., 2004) due to physical constraints. Therefore, the performance of the ad-hoc or mobile millimetre-wave networks requires enhancement by using spatial power combining antenna arrays

Electronically steerable 1-d fabry-perot leaky-wave antenna employing a tunable high impedance surface

© 2012 IEEE. A novel fixed-frequency electronically-steerable one-dimensional (1-D) leaky-wave antenna is presented. The antenna is based on a parallel-plate waveguide loaded with a planar partially reflective surface and a tunable high impedance surface (HIS), which creates a 1-D Fabry-Perot leaky-waveguide. The tunable HIS consists of printed patches loaded with varactor diodes that allow the electronic tuning of the cavity resonance condition. Using a simple Transverse Equivalent Network, it is theoretically shown how the variation of the varactors' junction capacitance allows the scanning of the antenna pointing angle from broadside towards the endfire direction at a fixed frequency. Experimental results of an antenna prototype operating at 5.6 GHz are reported, demonstrating that the new reconfigurable leaky-wave antenna can provide electronic beam scanning in an angular range from 9° to 30°

Single-Layer Bandpass Active Frequency Selective Surface

A single-layer, bandpass, active FSS is presented. It shows good angle of incidence stability for TE incidence, at the operating frequency of 2.45 GHz. It is based on circular loop aperture with each unit cell having four PIN diodes. A novel method for dc biasing is used. About 12 dB average variation in transmission loss, between ON and OFF states, has been experimentally achieved at 2.45 GHz

Antennas for future very-high throughput wireless LANs

We describe a possible very-high throughput system for future indoor wireless local area networks (WLAN) with data rates up to 40 Gbps. We show that to implement such networks, using components available in the foreseeable future, moderate gain multiple beam antennas will be required. Several antennas that can potentially meet the gain requirements and multiple beam functionality are proposed.4 page(s

Multilayer frequency-selective-surface reflector for constant gain over ultra wideband

In this paper the gain enhancement of an ultra-wideband (UWB) antenna, achieved using an appropriately designed multi-layer frequency selective surface (FSS) reflector is demonstrated. The proposed novel FSS reflects effectively in-phase over a bandwidth of about 145%. Consequently, significant enhancement in antenna gain has been achieved with a low-profile configuration without compromising the impedance bandwidth of the UWB antenna. The composite structure is compact, with a total height of λ/4 where λ is the free-space wavelength at the lowest operating frequency of 3 GHz. Experimental results show an impedance bandwidth of 145% BW with FSS and 149% without FSS. The antenna gain is maintained around 9.3 dBi from 3 to 15 GHz with a variation of ±0.5 dB. The predicted wideband antenna performance and gain enhancement due to the presence of the FSS reflector are discussed.3 page(s

Compact ultra-wideband CPW-FED printed semicircular slot antenna

A new compact configuration of a printed CPW-fed semicircular slot antenna with a CPW-to-CPW step transition is presented. Its bandwidth is enhanced for ultra-wideband (UWB) operation by combining linear and stepped CPW-to-CPW transitions along the feed line. Its measured 10 dB return loss bandwidth is 3.1–13.8 GHz (126%). This, together with its nearly constant measured gain of 3.5 dBi ± 1 dB from 3 to 10 GHz, makes it suitable for UWB applications. Details of the proposed antenna are described, and both theoretical and experimental results are presented.6 page(s

A Reconfigurable high-gain partially reflecting surface antenna

A high-gain partially reflective surface (PRS) antenna with a reconfigurable operating frequency is presented. The operating frequency is electronically tuned by incorporating an array of phase agile reflection cells on a thin substrate above the ground plane of the resonator antenna, where the reflection phase of each cell is controlled by the bias voltage applied to a pair of varactor diodes. The new configuration enables continuous tuning of the antenna from 5.2 GHz to 5.95 GHz using commercially available varactor diodes, thus covering frequencies typically used for WLAN applications. Both the PRS and phase agile cell are analyzed, and theoretical and measured results for gain, tuning range, and radiation patterns of the reconfigurable antenna are described. The effect of the varactor diode series resistance on the performance of the antenna is also reported.9 page(s