Richard J. Langley

Dual-Band Wearable Textile Antenna on an EBG Substrate

Performance of a dual-band coplanar patch antenna integrated with an electromagnetic band gap substrate is described. The antenna structure is made from common clothing fabrics and operates at the 2.45 and 5 GHz wireless bands. The design of the coplanar antenna, band gap substrate, and their integration is presented. The band gap array consists of just 3 times 3 elements but reduces radiation into the body by over 10 dB and improves the antenna gain by 3 dB. The performance of the antenna under bending conditions and when placed on the human body are presented.

Design Methodology for a Miniaturized Frequency Selective Surface Using Lumped Reactive Components

The design methodology is described for a miniaturized frequency selective surface (FSS) using lumped reactive components. Capacitive and inductive elements are utilized in metallic patches to create current loops similar to that observed in bandpass aperture type FSS. It is shown that the resonant frequency of the FSS is controlled mainly by the values of the lumped components and to a lesser extent by the distance between the components. It is insensitive to the periodicity. Issues such as the effects of component loss and oblique incidence are reported using full field predictions. Measurements are shown for an FSS with unit cell periodicity of ¿/36.

Meshed patch antennas

Conventional microstrip patch antennas are printed with continuous solid copper shapes and ground planes. The general properties of meshed patches are presented in this paper where both the patch itself and the ground plane are meshed. The gain, cross-polarization, bandwidth and radiation patterns are discussed for different combinations of patch and ground plane. The radiation patterns are not significantly affected by meshing the patch alone, but meshing the ground plane increases the back radiation. The gain can suffer by up to 3 dB or more when compared to a standard patch. Cross-polarization is improved providing that the correct mesh line geometry is chosen for the excitation mode. Meshing lowered the resonant frequency in some cases by up to 30% and also improves the bandwidth by a factor of up to 2.5 in some modes. Overall, the meshed patch offers a complex tradeoff between parameters but gives opportunities for improving the bandwidth and reducing the cross polarization and the antenna dimensions at the expense of the gain.

Crumpling of PIFA Textile Antenna

The performance of a PIFA textile antenna under different crumpling conditions is presented. The PIFA was designed for integration into clothing and other textile applications and the bending and crumpling conditions studied are typical of those found under normal use conditions both on and off body. Input impedance, efficiency and radiation patterns are investigated based on numerical and experimental methods at 2.4 GHz. Crumpling can have a serious effect on the resonant frequency, bandwidth and radiation from textile antennas.

Multiband PIFA vehicle telematics antennas

Compact, low-cost antennas for multiband telematics applications on vehicles are described. The multifrequency band antennas are variations on the printed inverted-F antenna (PIFA) principle. One type of PIFA is a compact variation of a conventional antenna while the other is a novel planar version customized for different mounting positions such as bumpers, window, and roof mount. In both derivations the dimensions are small and have been specifically designed for low-cost production. Each antenna was designed for mobile telephone band coverage from 890 to 2100 MHz. Results from free-space simulations are included but more work needs to be carried out as the vehicles have a significant effect on antenna performance. On-vehicle tests are described where the antennas were placed on glass and plastic areas and integrated into an existing multipurpose roof mount antenna.

Hidden Automotive Antenna Performance and Simulation

A new printed antenna system mounted in an aperture in the roof of a car is evaluated for broadcast signal reception from 88-108 MHz. Results from simulations on the vehicle are compared with measurements. The overall performance of the antenna is also compared to common types of vehicle antennas, the roof monopole and a glass based antenna. Overall the average gain of the antennas was better than -3 dBi for vertical polarization and -10 dBi for horizontal while the input return loss was generally better than -2 dB before matching sections in the tuners and comparable with common automotive antennas. The antennas in the roof aperture offer an alternative place to mount antennas on automobiles

Adaptive Wideband Beamforming With Frequency Invariance Constraints

A response variation (RV) element is introduced to control the consistency of an adaptive wideband beamformers response over the frequency range of interest. By incorporating the RV element into the linearly constrained minimum variance (LCMV) beamformer, we develop a novel linearly constrained beamformer with an improved output signal-to-interference-plus-noise ratio (SINR), compared to both the traditional formulation and the eigenvector based formulation, due to an increased number of degrees of freedom for interference suppression. In addition, two novel wideband beamformers robust against look direction estimation errors are also proposed as a further application of the RV element. One is designed by imposing a constraint on the RV element and simultaneously limiting the magnitude response of the beamformer within a pre-defined angle range at a reference frequency; the other one is obtained by combining the RV element and the worst-case performance optimization method. Both of them are reformulated in a convex form as the second-order cone (SOC) programming problem and solved efficiently using interior point method. Compared with the original robust methods, a more efficient and effective control over the beamformers response at the look direction region is achieved with an improved overall performance.

Single and double layer planar multiband PIFAs

A compact multiband planar inverted-F antenna (PIFA) suitable for distributed radio-over-fiber repeater networks is modified into a planar structure. It is shown that the planar antenna performance is not degraded with respect to the original PIFA and further, a two layer design is demonstrated to offer improved feed matching. The European bands for GSM, DCS-1800, DECT, UMTS, Bluetooth and HiperLAN2 are all covered. A model of the antenna is introduced as a first stage to developing an equivalent circuit

Wearable EBG antenna bending and crumpling

In this paper, we present the performance of a dual-band textile CPW antenna under different bending and crumpling conditions. The performance of the antenna is presented together with an electromagnetic band gap material (EBG) to improve the wearable antenna performance. The input impedance and radiation pattern are investigated based on numerical and experimental methods at 2.45 GHz and 5.8 GHz.

A Class of Constrained Adaptive Beamforming Algorithms Based on Uniform Linear Arrays

A new class of adaptive beamforming algorithms is proposed based on a uniformly spaced linear array by constraining its weight vector to a specific conjugate symmetric form. The method is applied to the well-known reference signal based (RSB) beamformer and the linearly constrained minimum variance (LCMV) beamformer as two implementation examples. The effect of the additional constraint is equivalent to adding a second step in the derived adaptive algorithm. However, a difference arises for the RSB case since no direction-of-arrival (DOA) information of the desired signal is available, which leads to a two-stage structure for incorporating the imposed constraint. Compared to the traditional algorithms, the proposed ones can achieve a faster convergence speed and a higher steady state output signal-to-interference-plus-noise ratio, given the same stepsize.