A biomimetic antenna in the shape of a bat’s ear

This letter presents a novel antenna that physically resembles the ear of a bat. The device consists of a circular ground plane with a central monopole element. An equilateral triangular conducting plate is curved around the ground so that the base of the triangle is electrically connected to the perimeter of the circle and is of the same length. The input characteristic is similar to the monopole above ground, providing there are a sufficient number of modes in the triangular plate at the frequency of interest. Certain frequencies yield a high gain and a radiation pattern with low side lobes

A method for forming distributed beams in time modulated planar arrays

The sidebands which originate in time modulated arrays can be used for numerous applications, including multipath signal separation and directional power transfer. In the present paper, a method of simultaneously producing a series of beams that are steered towards unique two-dimensional directions is presented by developing the theory of time-modulated linear arrays to time-modulated planar arrays. A planar array is modelled as two linear arrays on orthogonal axes and the binomial and Dolph-Chebyshev time-weighting distributions are applied to a 5 × 5 element array. The output of the array is shown in both the time and frequency domains

Acoustical direction finding with time-modulated arrays

Time-Modulated Linear Arrays (TMLAs) offer useful efficiency savings over conventional phased arrays when applied in parameter estimation applications. The present paper considers the application of TMLAs to acoustic systems and proposes an algorithm for efficiently deriving the arrival angle of a signal. The proposed technique is applied in the frequency domain, where the signal and harmonic content is captured. Using a weighted average method on harmonic amplitudes and their respective main beam angles, it is possible to determine an estimate for the signal’s direction of arrival. The method is demonstrated and evaluated using results from both numerical and practical implementations and performance data is provided. The use of Micro-Electromechanical Systems (MEMS) sensors allows time-modulation techniques to be applied at ultrasonic frequencies. Theoretical predictions for an array of five isotropic elements with half-wavelength spacing and 1000 data samples suggest an accuracy of ±1∘ within an angular range of approximately ±50∘ . In experiments of a 40 kHz five-element microphone array, a Direction of Arrival (DoA) estimation within ±2.5∘ of the target signal is readily achieved inside a ±45∘ range using a single switched input stage and a simple hardware setup

Accuracy of harmonic analysis techniques for direction of arrival estimation using time modulated arrays

This paper presents a comparison between two direction of arrival (DoA) estimation methods using time modulated linear arrays (TMLAs). The first method uses a two element array and numerically derives the signal DoA by using the ratio of the two harmonics created by array. The second method makes use of a greater number of elements and known steering angles of the array sidebands. Results of a numerical simulation are presented which detail the accuracy in direction finding when using the two techniques while the array is subject to environmental conditions such as noise and coherent signal interference. It is shown that whilst the second method requires a greater number of elements, it has greater immunity to noise and multipaths

Radiation characteristics of a conical monopole antenna with a partially corrugated ground plane.

In order to preserve broadband performance, the conical monopole antenna is ideally mounted on a semi-infinite ground plane. Practical finite ground planes can introduce unwanted effects in the radiation patterns such as significant back lobes. Periodic surfaces such as rotationally symmetric corrugated structures have been proven capable of improving the radiation characteristics of a variety of antennas. In this paper, the radiation patterns of a conical antenna with a PEC reflector are initially presented. The PEC reflector is then replaced with a partially corrugated reflector surface. The effects of the partially corrugated reflector on the radiation patterns and electric field distribution along the reflector surface are investigated. The simulation results reveal that the radiation patterns of a conical antenna with a partially corrugated reflector are more stable over a wide frequency band than that for the PEC reflector

A study on the effect of loop-like jewellery items worn on human hand on specific absorption rate (SAR) at 1900 MHz

Abstract: This paper presents simulation results that evaluate the effect of loop-like jewellery items (rings and bangles) worn on human fingers and wrist on SAR in the human head and the hand. The jewellery items were modelled as conducting objects with the typical commercial sizes available. Rings were placed on different fingers in a computer model for comparison purposes. The amount of energy absorbed in the head/hand and the effect brought about by the jewellery are shown to vary for different antennas. In this study, a monopole and a PIFA antenna have been employed. The results obtained indicated that: (i) by using a monopole antenna, the peak and average 1g SAR in the head are slightly decreased by the introduction of the ring and bangle, (ii) by using a PIFA, the peak and average 1g SAR in the head are increase by more than 12% and 11% respectively by the metallic rings

A study on the effect of a metallic ring worn on human fingers using a simple scannable block hand phantom

A simple geometrical representation of a human hand has been constructed which allow a metallic ring to be placed on the finger. The electric field magnitude within an isolated finger is measured and compared with the cases when the ring is worn. The ring has been found to significantly alter the electric field magnitude within the finger at 1800 MHz. This effect can also be found within the adjacent fingers at both 900 MHz and 1800 MHz

Performance metrics for the prediction of link and path availability in VANETs

In this paper metrics are produced which may be used for performance enhancement in Vehicular ad-hoc networks (VANETs) protocols. The method described makes use of the concept of link availability estimates which are produced on an individual link basis and which may be combined by multiplication to produce a quality metric for the whole route. The technique is discussed in the context of the Ad hoc On-demand Distance Vector (AODV) routing method

Polarisation dependent EBG surface with an inclined sheet via

This paper presents a novel polarisation dependent EBG (PDEBG) surface which makes use of sheet vias. The performance of the surface is analysed whilst varying the length, thickness and inclination of the vias. It is observed that the phase difference between the x-polarised and y-polarised component of the reflected wave can be controlled by varying these parameters. Furthermore, the surface exhibits a polarisation conversion property with potential use in a variety of antennas

Textile-to-rigid microstrip transition using permanent magnets

A novel transition between a rigid-substrate and a flexible-substrate microstrip for use in wearable devices is described. The contact force between the conductors of the two microstrips is supplied by a pair of rectangular magnets. A simulation and measurement study carried out on a test jig comprising a back-to-back pair of such transitions demonstrated an insertion loss of better than 0.5 dB/transition can be achieved in the range of 0-3 GHz