Experimental investigations of a new adaptive dual-antenna array for handset applications

This paper presents the design and implementation of a new adaptive dual-antenna array for mitigation of both interference and multipath effects in digital mobile communications at the handset level. This proposed system employs a nonlinear adaptive algorithm in the front end of the receiver to enhance the transmission quality in confined areas. The enhancement is blind since no priori knowledge of spatial signatures or training sequences is required. Furthermore, to obtain a compact antenna array system, a miniaturized shorting postmicrostrip antenna that operates in the 1.9 GHz PCS band is used as a radiating element. Using this microstrip antenna, a new experimental adaptive dual-antenna array prototype was designed and implemented. To examine the expected performance of this approach, experimental measurements were carried out and the measured performances indicate that gain improvement of 7 dB can be achieved by using this approach.     

Rectangular dielectric resonator antenna for ultrawideband applications

A new dielectric resonator antenna (DRA) is introduced for ultrawideband applications. A rectangular dielectric resonator, a bevel feeding patch and an airgap between the DR and ground plane are used to obtain an ultrawideband impedance bandwidth. The effective dielectric constant and the Q-factor can be reduced by using the airgap and the bevel-shaped feeding mechanism, which can provide a smooth transition from one resonant mode to another. Measured results demonstrate that the proposed DRA has a wide bandwidth from 2.6 to 11 GHz with VSWR less than two, covering the frequency range of more than 120%. Experimental and numerical results are carried out and discussed, showing good agreement.     

High gain microstrip antenna design for broadband wireless applications

This article presents a new broadband microstrip antenna for personal communications systems (PCS) applications. Using multilayer substrate structure with aperture‐coupled feed, a rectangular microstrip patch antenna operating at 1.9‐GHz band is designed and experimentally validated. This antenna configuration uses a quarter‐wave transformer to enhance the matching between the feed transmission line and the antenna patch. To demonstrate the design procedure, a first experimental broadband microstrip antenna prototype is designed and implemented. To analyse its performance, measurements are carried out and good performances are achieved. However, this prototype has a low front‐to‐back ratio. To overcome this drawback, an optimization process is proposed, and a second prototype is designed and successfully realized. To examine the effect of the optimization, experimental investigations are carried out on the second prototype. Very good agreement is obtained between numerical and measured results. Experimental results indicate that the proposed antenna achieves a bandwidth of 21%, a gain of 9.5 dB, and a front‐to‐back ratio of 20 dB, which are very sufficient for broadband wireless applications. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13, 511–517, 2003.     

Wall reflection modelling for horn directional antenna at EHF

The effect of directional horn antenna radiation patterns is important to characterise an indoor radio channel. Instead of a single ray, the main possible rays of departure and arrival are considered according to the directional horn transmitter and receiver antenna radiation patterns using ray tracing. Computation results fit well with the measurements upon wall reflection at the EHF band.     

Experimental investigation of a new butler matrix using slotline technology for beamforming antenna arrays

The design and realisation of a 4 times 4 Butler matrix for multibeam antenna arrays operating at 5.8timesGHz are described. The matrix is implemented on a single layer slotline structure to avoid using air bridges as required in coplanar waveguide technology. In this design, a new hybrid coupler and a crossover using slotline technology were designed and fabricated, and they are used to build a new Butler matrix. To examine the performances of the proposed matrix, numerical simulations and experimental measurements were carried out; the comparison between simulated and experimental results shows a good agreement.     

Design and implementation of a substrate integrated waveguide phase shifter

The design and implementation of a phase shifter based on the substrate integrated waveguide (SIW) technique operating at 10 GHz are presented. The proposed phase shifter consists of a SIW section with two inserted metallic posts. The phase shifting in this configuration is achieved by changing the diameter and the position of these posts. Numerical simulations have been carried out for different diameters and positions, which have shown good agreement with the theory. A parametric study was also conducted to assess the impact of errors made on the diameter and position of the two metallic posts. To prove the concept, prototypes were fabricated and measured. Experimental results agree well with simulations and SII was better than -14 dB, S21 better than -1.08 dB and the phase error was less than 1.5deg.     

Wideband slot antenna using a new feeding technique for wireless applications

This article presents a new wideband slot antenna for wireless applications at 5.8 GHz. To improve the antenna bandwidth, a new feeding mechanism based on a capacitively‐ and inductively‐coupled slot is proposed. To demonstrate this approach, an experimental antenna prototype operating at the 5.8‐GHz band was designed, fabricated, and measured. The obtained results indicate very good agreement between the numerical and experimental results. The proposed antenna achieves a 28.5% bandwidth, a 5.7‐dBi gain, and a ?15‐dB front‐to‐back ratio, which are very sufficient for broadband wireless applications. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Ultra-wideband bandpass filter using back-to-back CBCPW-to-CBCPW transition

A new ultra-wideband bandpass filter using a back-to-back CBCPW-to-CBCPW transition structure is presented. The filter is composed of two CBCPW-to-CBCPW transitions and a section of a CBCPW line section used as a multiple-mode resonator. Using this transition, a new ultra-wideband filter prototype was designed, fabricated and measured. Obtained results show that the proposed filter can easily cover the band from 3.1 to 10.6 GHz.     

Ultra-wideband microstrip to CB-CPW transition applied to broadband filter

A new ultra-wideband microstrip to conductor backed coplanar waveguide (CB-CPW) transition structure is presented and implemented. Results show good performance in terms of bandwidth, which is about 12 GHz. Using this transition, a new ultra-wideband filter was designed and fabricated. Simulated and measured results show that the filter can cover the band from 3.1 to 10.6 GHz (-10 dB bandwidth)     

A nonlinear algorithm for output power maximization of an indooradaptive phased array

An adaptive receiving phased-array antenna is considered as one of the desirable features of the next generation of personal wireless indoor system. Such a feature will render this communication system much less sensitive to the signal fluctuations due to multipath propagation. This paper presents a prototype adaptive phased array based on an original nonlinear method. This adaptive algorithm which uses as performance criterion the maximization of the array output power to adjust a phase angle, is developed and applied to antenna system in order to control automatically its directivity pattern. Numerical results for a linear eight element array are presented. To test the algorithm experimentally, an eight element 20-GHz array, constructed using horn antennas and analog phase shifters, was used. The results obtained so far with such an array are discussed in the context of its eventual, implementation in MHMIC