Improvement of compact terminal antenna performance by incorporating open-end slots in ground plane

This letter describes a new idea of increasing operational bandwidth of a compact planar inverted F antenna (PIFA) by introducing open-end slots in the ground plane under the radiating patch. The slots are not in the way of active modules of a wireless transceiver and thus the proposed antenna size reduction method is attractive from the point of view of practical implementation.

A low-profile dual-band antenna for a wireless LAN access point

The design of dual-band 2.45/5.2 GHz antenna for an acces point of a Wireless Local Area Network (LAN) is presented. The proposed antenna is formed by a Radial Line Slot Array (RLSA) operating at 2.4 GHz and a Microstrip patch working at 5.2 GHz, both featuring circular polarization. The design of this antenna system is accomplished using commercially available Finite Element software. High Frequency Structure Simulator (HFSS) of Ansoft and an in-house developed iteration procedure. The performance of the designed antenna is assessed in terms of return loss (RL), radiation pattern and polarization purity in the two frequency bands.

Robust stability of sequential multi-input multi-output quantitative feedback theory designs

This paper re-examines the stability of multi-input multi-output (MIMO) control systems designed using sequential MIMO quantitative feedback theory (QFT). In order to establish the results, recursive design equations for the SISO equivalent plants employed in a sequential MIMO QFT design are established. The equations apply to sequential MIMO QFT designs in both the direct plant domain, which employs the elements of plant in the design, and the inverse plant domain, which employs the elements of the plant inverse in the design. Stability theorems that employ necessary and sufficient conditions for robust closed-loop internal stability are developed for sequential MIMO QFT designs in both domains. The theorems and design equations facilitate less conservative designs and improved design transparency.

On stability in nonsequential MIMO QFT designs

This paper reexamines the stability of uncertain closed-loop systems resulting from the nonsequential (NS) MIMO QFT design methodology. By combining the effect of satisfying both the robust stability and robust performance specifications in a NS MIMO QFT design, a proof for the stability of the uncertain closed-loop system is derived. The stability theorem proves that, subject to the satisfaction of a critical necessary and sufficient condition, the original NS MIMO QFT design methodology will provide a robustly stable closed-loop system. This necessary and sufficient condition provides a useful existence test for a successful NS MIMO QFT design. The results expose the salient features of the NS MIMO QFT design methodology. Two 2 x 2 MIMO design examples are presented to illustrate the key features of the stability, theorem.

Embedding partial G-designs where G is a 4-cycle with a pendant edge

Let D denote the graph consisting of a cycle of length 4 with a pendant edge. In this paper, two very different small embeddings of partial D-designs are presented. (c) 2005 Elsevier B.V. All rights reserved.

Existence of complementary pairs of proportionally balanced designs

Proportionally balanced designs (pi BDs) were introduced by Gray and Matters in response to a need for the allocation of markers of the Queensland Core Skills Test to have a certain property. Subsequent papers extended the theoretical results relating to such designs and provided further instances and general constructions. This work focused on designs comprising blocks of precisely two sizes, and when each variety occurs with one of precisely two possible frequencies. Two designs based on the set V of varieties are complementary if, whenever B is a block of one, then its complement with regard to the set V is a block of the other. Here we present necessary conditions for the existence of complementary pairs of such pi BDs and provide lists of some restricted parameter sets satisfying these necessary conditions. The lists are arranged according to the number of blocks. We demonstrate that not all of these parameter sets give rise to designs. However we establish by construction of the sets of blocks that, for every feasible number of blocks less than or equal to 100, with the possible exception of 63, there exists at least one pair of complementary pi BDs. We also investigate the conditions under which the complementary design can be isomorphic to the original design, and again provide a list of feasible parameters for pairs of such designs with at most 400 blocks.

PBG-assisted shared-aperture dual-band aperture-coupled patch antenna for satellite communication

Design and development of a photonic bandgap (PBG)-assisted shared-aperture dual-band orthogonal aperture-fed rectangular microstrip patch antenna element, which is suitable for a portable very small aperture terminal (VSAT), are presented in this paper. The dual-band dual-polarized antenna element achieves 21% input impedance bandwidth at the S- and C-bands. A comparison of the antenna with and without 2D PBG grids shows that the inclusion of PBG structures (PBGSs) improves the antenna performances. (c) 2005 Wiley Periodicals, Inc.

Distinct types of glial cells populate the Drosophila antenna

Background: The development of nervous systems involves reciprocal interactions between neurons and glia. In the Drosophila olfactory system, peripheral glial cells arise from sensory lineages specified by the basic helix- loop- helix transcription factor, Atonal. These glia wrap around the developing olfactory axons early during development and pattern the three distinct fascicles as they exit the antenna. In the moth Manduca sexta, an additional set of central glia migrate to the base of the antennal nerve where axons sort to their glomerular targets. In this work, we have investigated whether similar types of cells exist in the Drosophila antenna. Results: We have used different P( Gal4) lines to drive Green Fluorescent Protein ( GFP) in distinct populations of cells within the Drosophila antenna. Mz317:: GFP, a marker for cell body and perineural glia, labels the majority of peripheral glia. An additional similar to 30 glial cells detected by GH146:: GFP do not derive from any of the sensory lineages and appear to migrate into the antenna from the brain. Their appearance in the third antennal segment is regulated by normal function of the Epidermal Growth Factor receptor and small GTPases. We denote these distinct populations of cells as Mz317- glia and GH146- glia respectively. In the adult, processes of GH146- glial cells ensheath the olfactory receptor neurons directly, while those of the Mz317- glia form a peripheral layer. Ablation of GH146- glia does not result in any significant effects on the patterning of the olfactory receptor axons. Conclusion: We have demonstrated the presence of at least two distinct populations of glial cells within the Drosophila antenna. GH146- glial cells originate in the brain and migrate to the antenna along the newly formed olfactory axons. The number of cells populating the third segment of the antenna is regulated by signaling through the Epidermal Growth Factor receptor. These glia share several features of the sorting zone cells described in Manduca.

Longitudinal research designs in Music Therapy: Recommendations from a study of people with dementia.

Longitudinal research studies in music therapy are not frequently reported within the music therapy literature despite the need for these within the discipline. This article aims to encourage music therapists to undertake longitudinal research, by providing information on aspects of this type of research design. The authors discuss some advantages of longitudinal research approaches, and present the challenges expected to be faced by those conducting longitudinal research studies. Reflections on the authors' experiences in investigating long term effects of music therapy on people with dementia are described, along with recommendations as to how future researchers might address or accommodate some of these challenges

Combating interference in an indoor wireless-communication system using a phased-array antenna with switched-beam elements

A phased-array antenna with switched-beam elements used to combat interference in an indoor wireless communication system is described. The array uses I-bit phase shifters applied to its elements in order to point its main beam in a desired direction and internal switching of elements in order to form nulls towards interference. The array's capability of suppressing interference is verified by studying its radiation patterns and by performing interference-rejection experiments in an indoor multipath environment. (c) 2005 Wiley Periodicals, Inc.

Practical dual-helical antenna array for diversity/MIMO receiving antennas on mobile handsets

A practical, small-size, dual-helical antenna array mounted on a mobile handset model is designed for use as diversity/MIMO receiving antennas. The array is rigorously studied with respect to its diversity performance and the achievable channel capacity. It is found that a very low correlation coefficient, a high diversity gain, an equal-mean branch SNR, and a relatively matched input impedance can be achieved at the same time. It is shown that, at a remarkably small antenna separation (similar to 0.05 lambda), the signal correlation can be reduced to nearly zero, an almost ideal independent operation of the diversity antennas. The increase in MIMO channel capacity is 100% over a single antenna system. Both measured and simulation results are presented.

The performance of the maximum ratio combining method in correlated Rician-fading channels for antenna-diversity signal combining

The performance of the maximum ratio combining method for the combining of antenna-diversity signals in correlated Rician-fading channels is rigorously studied. The distribution function of the normalized signal-to-noise ratio (SNR) is expanded in terms of a power series and calculated numerically. This power series can easily take into account the signal correlations and antenna gains and can be applied to any number of receiving antennas. An application of the method to dual-antenna diversity systems produces useful distribution curves for the normalized SNR which can be used to find the diversity gain. It is revealed that signal correlation in Rician-fading channels helps to increase the diversity gain rather than to decrease it as in the Rayleigh fading channels. It is also shown that with a relative strong direct signal component, the diversity gain can be much higher than that without a direct signal component.

Embedding a restricted class of partial K-4-designs

Given a partial K-4-design (X, P), if x is an element of X is a vertex which occurs in exactly one block of P, then call x a free vertex. In this paper, a technique is described for obtaining a cubic embedding of any partial K-4-design with the property that every block in the partial design contains at least two free vertices.

A printed hemispherical helical antenna for GPS receivers

A self-matched printed hemispherical helical antenna for potential use in global positioning system receivers is introduced. Unlike wired hemispherical helical antennas, its printed form renders it a much more stable and endurable structure and also easier for fabrication. The optimized antenna shows an impedance bandwidth of 6%, a 3-dB axial ratio bandwidth of 6%-7%, a return loss greater than 20 dB, and a gain of about 9 dB at the center frequency. The patterns of the antenna show a larger mainlobe in the upper half space with relatively small backlobes. Both theoretical and experimental results will be presented.