Arkadiusz Byndas

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.

Broadening the bandwidth in terminal antennas by tuning the coupling between the element and its ground

The intensive research on terminal antennas in recent years examined new ideas that resulted in the formulation of guidelines on how specific antenna parameters could be accomplished. Among the more challenging variables in obtaining parameters, two gained our particular attention: a broad bandwidth and a radiation pattern that does not produce SAR values exceeding the permissible level. Broadening the bandwidth at the lowest resonance in multiresonant antennas featuring the highest possible scale of miniaturization was the most difficult task. Owing to the possible highest scale of miniaturization, various modifications of PIFAs have attracted much attention. We present an equivalent circuit model for a dual-band antenna. The model reflects the importance of a strong mutual coupling in miniaturized PIFAs. Providing very broad bandwidths with highly miniaturized antenna was possible when parts of the PIFA element were inserted into the slits in the small ground plate. The measured efficiency values are high and meet the expectations of modern wireless device designers.

An application of a narrow slot cut in the ground to improve multi-band operation of a small antenna

In general, small size multi-band antennas for hand held phones have to operate at low frequency bands below 1 GHz and at upper frequency bands, which are in the vicinity of 2 GHz and 5.5 GHz. When the desired number of resonances is generated in a small antenna, normally much effort must be spent to achieve the required bandwidth properties, usually expressed in terms of impedance match and radiation efficiency. To cope with this problem, we have investigated a modification which concerns the introduction of a slot cut in the ground plane supporting a small antenna. We investigate the effect of various shapes of slot cuts on the impedance properties and radiation pattern of a modified antenna. The use of suitable slots can significantly improve the return loss bandwidths. The introduction of a slot in the ground plane raises concerns about increasing radiation towards the user. We have observed that there is no preferred direction of the radiation propagating towards the. user for frequency bands below 1000 MHz when slots or cuts are inserted in the ground. For upper bands above 1000 MHz, the strongest radiation can occur towards the user, but such an effect is also observed in antennas with solid ground plates.

Determination of radiation efficiency by the integration method on the spherical pattern represented with a limited number of cut-planes

This paper presents use of this measuring system to determine radiation efficiency of small antennas with the direct approach, by integration field components onto the spherical radiation pattern.

Potential advantage of using non rectangular ground in small antennas featuring wideband impedance match

Domination of PIFAs could have satisfied demands set by designers of portable terminals for almost a decade. However, any other form of high efficiency antenna featuring a high degree of miniaturization raises interest both in terms of electromagnetic phenomenon explored and in terms of potential practical uses. Furthermore, some subtle details - neglected during research works - may gain a status go or no go factor in mass market uses. Driven with this motivation we put much attention in our studies into antenna miniaturization with other means than barely the PIFA concept. To bandwidth properties in miniature antennas, a paramount importance has an interaction between the ground and the element. Focus on this interaction turned out to be key to invent coaxially fed miniature antennas without any short which is presented in this paper.

A measurement system for determining radiation efficiency of a small antenna

The paper describes a system for measuring radiation efficiency of a small antenna operating alone or in the presence of objects similar to those as in an actual service. The system applies the direct approach to determining the antenna efficiency by measuring the radiated field over the entire sphere surrounding the tested antenna. In order to overcome problems associated with the conventional measuring equipment, the antenna under test is equipped with a miniature built-in VCO signal generator and supported by a low reflectivity dielectric positioner. The positioner is of sufficient size and strength to hold a human head phantom to investigate changes in radiation characteristics when the antenna operates in the presence of a human operator.

Radiation pattern measurements of small isolated antennas

We present a system developed for measuring small antennas; in particular, for measuring their radiation patterns in a spherical format. The antenna under test (AUT) is positioned with an elevation over the azimuth positioner made entirely from dielectric materials. The test signal can be fed from a built-in generator powered by a battery. Owing to the elimination of the feeding cable normally used in an antenna measuring setup, measurements are run in conditions that reconstruct the actual operational environment with accurate results. The measuring time is short, as the rotational speed of the dielectric positioner is sufficiently fast. With the use of a microwave backward projection technique, it is possible to estimate the field distribution inside a lossy object placed next to the AUT, thus providing a quick, nondosimetric evaluation of the SAR distribution inside a phantom head.

Foldeable wideband small antenna element

Various designs of dual or more band planar inverted-F antennas (PIFAs) were manufactured perhaps well in excess of a billion pieces over the last decade. Most PIFAs are single layer antenna elements with a volume of 3 to 7 cm3. Presently, there is a growing number of emerging applications which apparently call for other antenna concepts. The reasons could differ and range from a bandwidth beyond that available with PIFAs to wearable antennas made on fine substrates and operating in a strongly varying environment. Our research had addressed an emerging class of antenna for servers wirelessly serving commercial electronics. Antenna should be capable of being accommodated in many manners - on a PCB, at the front panel, as a plug-in device, in planar or conformal shape.

Low profile dual-polarized antenna array for operation at the K band

Gradual implementation of new services and new technologies at K-bands (i.e. 16-32 GHz), calls for major advancement in antenna array technology. Low-profile antenna are in particular desire. We present some results of investigations into antenna elements made for use in arrays. The main design objectives are antenna element capability to operate with a pair of orthogonal polarizations and low profile. The minimum bandwidth expressed in terms of not only impedance match, but with use of four other major antenna parameters is 1 GHz.

Polarization isolation limits for highly integrated dual-polarized x-band multilayer antenna array applied in novel airborne polarimetric radar

This paper focuses on dual-polarized antenna array technology making use of low-profile composite panels to integrate antenna elements with their polarization feed circuits and array beamforming network. It emphasizes two key technical parameters: isolation between polarizations and high bandwidth performance. The paper presents how modern computational electromagnetic techniques enables high degree of antenna array integration. In such highly integrated antennas after manufacturing there is little possibility to correct feed network circuits. Measurement techniques are possible only with indirect approaches. The discussion is supported by results of state-of-the-art antennas for X-band operation on satellite, airborne and maritime platforms.