Electromagnetic wave diffraction from an infinite array of complex-shaped microstrip reflectors

A numerical-analytical method is developed for solving surface integral equations (IEs) describing electromagnetic wave diffraction from arrays of complex-shaped planar reflectors. Solutions to these equations are regularized via analytical transformation of the separated singular part of the matrix kernel. Basis functions satisfying the metal-edge condition are determined on the entire surface of the complex region. The amplitude and phase responses of arrays consisting of polygonal reflectors are numerically investigated.

An integrated wideband multifunctional antenna using a microstrip patch with two U-slots

In this paper a multifunctional microstrip antenna is designed, fabricated and experimentally verified for operation in AWS, GSM, WiMAX and WLAN bands. This microstrip patch antenna has two U-shaped slots to achieve the dual wideband operation required to meet these specifications. The dimensions and locations of the U-slots are designed appropriately. The thick substrate used here helps in integrating the antenna with the existing aircraft panel material while achieving wide bandwidths. Experimental results of this single feed antenna indicate that it meets all current requirements for in-cabin wireless communication needs.

A Novel Quad-Polarization Agile Patch Antenna

In this communication we present a novel polarization-agile microstrip antenna design. To dynamically change the polarization state, the radiating patch is fed by a tunable quasi-lumped coupler. The whole structure can be dynamically altered to radiate electromagnetic waves with vertical linear, horizontal linear, right-handed circular or left-handed circular polarization simply by changing the operating mode of the quasi-lumped coupler. Due to its topology the coupler is simply reconfigured by switching the bias of two varactor diodes via a very simple DC bias circuitry: no additional capacitors or inductors are required. A prototype is fabricated with a 0.762-mm-thick upper layer substrate for the radiating element and a 0.130-mm-thick layer substrate for the coupler circuit, both with the same dielectric material relative permittivity of 2.22. The simulated and measured scattering parameters, the axial ratio in circular radiation-mode and the cross-polarization level in linear mode, the gain and the radiation patterns are presented. The agile polarization capabilities of this new antenna, as demonstrated in this communication, underscore its suitability for modern wireless communications in a multi-path propagation environment.

V-band 57-65 GHz receiver

A simple V-band radio IQ receiver architecture based around a six-port monolithic microwave integrated circuit (MMIC) is presented. The receiver assembly is designed to cover the 57-65 GHz broadband wireless communication system frequency allocation. The receiver that has an integral 10 dB microstrip antenna consumes 120 mW of dc power and occupies an area of 23 mm x 16 mm. The receiver can be used in heterodyne or in homodyne mode and has the capacity to demodulate quadrature amplitude modulation (QAM), binary phase shift keying (BPSK)/quadrature phase shift keying (QPSK)/offset quadrature phase shift keying (OQPSK). At 60 GHz the receiver can operate over 10 m range for transmitter effective isotropic radiated power (EIRP) of 20 dBm.

Molecular Phylogenies Support Homoplasy of Multiple Morphological Characters Used in the Taxonomy of Heteroscleromorpha (Porifera: Demospongiae)

Sponge classification has long been based mainly on morphocladistic analyses but is now being greatly challenged by more than 12 years of accumulated analyses of molecular data analyses. The current study used phylogenetic hypotheses based on sequence data from 18S rRNA, 28S rRNA, and the CO1 barcoding fragment, combined with morphology to justify the resurrection of the order Axinellida Lévi, 1953. Axinellida occupies a key position in different morphologically derived topologies. The abandonment of Axinellida and the establishment of Halichondrida Vosmaer, 1887 sensu lato to contain Halichondriidae Gray, 1867, Axinellidae Carter, 1875, Bubaridae Topsent, 1894, Heteroxyidae Dendy, 1905, and a new family Dictyonellidae van Soest et al., 1990 was based on the conclusion that an axially condensed skeleton evolved independently in separate lineages in preference to the less parsimonious assumption that asters (star-shaped spicules), acanthostyles (club-shaped spicules with spines), and sigmata (C-shaped spicules) each evolved more than once. Our new molecular trees are congruent and contrast with the earlier, morphologically based, trees. The results show that axially condensed skeletons, asters, acanthostyles, and sigmata are all homoplasious characters. The unrecognized homoplasious nature of these characters explains much of the incongruence between molecular-based and morphology-based phylogenies. We use the molecular trees presented here as a basis for re-interpreting the morphological characters within Heteroscleromorpha. The implications for the classification of Heteroscleromorpha are discussed and a new order Biemnida ord. nov. is erected.

Low-profile resonant cavity antenna with artificial magnetic conductor ground plane

A planar artificial magnetic conductor (AMC) ground plane is proposed as a means to reduce the profile of a highly directive resonant cavity antenna. The structure is formed by a printed microstrip patch antenna and a superimposed partially reflective surface. The antenna profile is reduced to approximately half by virtue of employing the AMC ground plane. A ray theory model is used to qualitatively describe the functioning of the antenna and theoretically predict the existence of quarter wavelength resonant cavities.

A double U-slot patch antenna with dual wideband characteristics

Microstrip patch antennas are strong candidates for use in many wireless communications applications. This paper proposes the use of a patch antenna with two U-shaped slots to achieve dual band operation. A thick substrate helps broaden the individual bandwidths. The antenna is designed based on extensive IE3D simulation studies. A prototype antenna is fabricated and experimentally verified for the required performance.

Compact quadrifilar helix antenna

Introduction: The quadrifilar helix antenna (QHA) is used widely for terrestrial [1] and space communication systems [2], where it is necessary to generate a circularly polarised cardioid-shaped radiation pattern with a high front-to-back ratio and low cross-polarisation. The radiating structure comprises four helical conductors which are excited in phase quadrature at the feed point, which is usually located at the centre of the top radials. The physical size of the quadrifilar antenna can be reduced by dielectric loading [3] or by meandering the printed linear elements [4]. However, in the former arrangement dielectric absorption reduces the radiation efficiency of the antenna, and the latter technique is not suitable for constructing free standing wire structures, which are normally used for spacecraft payloads in the VHF and UHF bands [2]. This Letter shows that a significant reduction in the axial length of a 1/2 turn half-wavelength QHA can be achieved by modifying the geometry of the helices in the region around the midpoint where a current null exists. Simulated and experimental results at L band are used to show that a size reduction of up to 15% is possible without significantly degrading the pattern shape and the bandwidth.

The design and performance of a 2.5-GHz telecommand link for wireless biomedical monitoring

This paper details the implementation and operational performance of a minimum-power 2.45-GHz pulse receiver and a companion on-off keyed transmitter for use in a semi-active duplex RF biomedical transponder. A 50-Ohm microstrip stub-matched zero-bias diode detector forms the heart of a body-worn receiver that has a CMOS baseband amplifier consuming 20 microamps from +3 V and achieves a tangential sensitivity of -53 dBm. The base transmitter generates 0.5 W of peak RF output power into 50 Ohms. Both linear and right-hand circularly polarized Tx-Rx antenna sets were employed in system reliability trials carried out in a hospital Coronary Care Unit, For transmitting antenna heights between 0.3 and 2.2 m above floor level, transponder interrogations were 95% reliable within the 67-m-sq area of the ward, falling to an average of 46 % in the surrounding rooms and corridors. Overall, the circular antenna set gave the higher reliability and lower propagation power decay index.

Artificial magnetic conductor surfaces and their application to low-profile high-gain planar antennas

Planar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate and they introduce a zero degrees reflection phase shift to incident waves. In this paper the AMC operation of single-layer arrays without vias is studied using a resonant cavity model and a new application to high-gain printed antennas is presented. A ray analysis is employed in order to give physical insight into the performance of AMCs and derive design guidelines. The bandwidth and center frequency of AMC surfaces are investigated using full-wave analysis and the qualitative predictions of the ray model are validated. Planar AMC surfaces are used for the first time as the ground plane in a high-gain microstrip patch antenna with a partially reflective surface as superstrate. A significant reduction of the antenna profile is achieved. A ray theory approach is employed in order to describe the functioning of the antenna and to predict the existence of quarter wavelength resonant cavities.

Patch antenna with linear polarisation tilt control

The design of a linearly-polarised agile antenna is presented. The antenna is fed by a quasi-lumped coupler which has the ability to tune the magnitude ratio between its two outputs from -30 dB to 15 dB by modifying the bias of two varactor diodes. In this way the relative power fed to each orthogonal port of a patch antenna can be varied. Consequently, tilt control of the radiated linearly-polarised waves is achieved over a range of 90 degrees.