Pawel Kabacik

Parameter study of a broadband uniplanar quasi-Yagi antenna

A parameter study is performed of a broadband uniplanar quasi-Yagi antenna with regard to its design and use in a spatial power combiner. The uniplanar quasi-Yagi antenna consists of a director and a driver fed by a broadband microstrip to coplanar strip transition. The truncated ground plane on the backside of the substrate is used as a reflector. A 3D full-wave electromagnetic field analysis, using a commercially available 3D full-wave EM package, is applied to identify those parameters which most affect the design frequency and operational bandwidth of this antenna. Optimal design conditions are identified.

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 electromagnetic-field method modeling of a radial line planar antenna with coupling probes

This communications describes an electromagnetic model of a radial line planar antenna consisting of a radial guide with one central probe and many peripheral probes arranged in concentric circles feeding an array of antenna elements such as patches or wire curls. The model takes into account interactions between the coupling probes while assuming isolation of radiating elements. Based on this model, computer programs are developed to determine equivalent circuit parameters of the feed network and the radiation pattern of the radial line planar antenna. Comparisons are made between the present model and the two-probe model developed earlier by other researchers.

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.

TTC patch antennas made in a conformal form with small radius

Telemetry, teleranging and telecommand (TTC) communication is essential to maintain space missions. Antennas for TTC applications must feature wide - or even omnidirectional - radiation properties. In this paper we present results of our investigations on small size cylindrical arrays which can ensure such radiation properties. Due to small volume required they can be mounted at top and bottom of small spacecraft. Our interest is focused on the S-band, however, results can be extended onto upper microwave frequency bands. We attempted to optimize radiation and impedance properties of patch elements conformal to a small radius cylindrical surface, which is about a wavelength in diameter. The considered cylindrical arrays consist of three to seven probe-fed patches. As a further upgrade to the investigated cylindrical antenna we propose to use a spherical patch on a top of such cylindrical arrays. With use of less expensive materials, the proposed antenna concepts can be applied in wireless communication and in electronic instruments.

On omnidirectional coverage with minimum number of circularly polarized patch antennas placed on minisatellites

In the design of spacecraft, modern numerical electromagnetism can effectively deal with studies into optimization of antenna placement. Such studies are of great importance to reduce risks of disruption communication between spacecraft and ground stations (GS). We had carried out an extensive numerical modeling and experimental validation of the simulation results in this area. These efforts were concentrated on determination of a combined radiation pattern for several antennas mounted on minispacecraft. Size of a main body of the minispacecraft under analysis was up to ~60x60x70cm (23x23x27 inches). In the analysis we had drawn our attention to effects related to solar panels and we proposed technical means to mitigate impact of failed panel deployment to the communication subsystem.

Optimizing Circular Polarization within a Beam of Patch Antenna Elements

The paper presents the results of an investigation into patch antenna elements that would be capable of providing good circular polarization not only in the broadside direction, but also over a wide range of elevation angles.

The omnidirectional coverage of low-profile TTC antennas onboard minispacecraft

The optimization of antenna placement onboard minisatellites is key in shaping the coverage pattern of TTC (telemetry, teleranging and telecommand) links. A careful selection of phasing between two or more TTC antennas is needed to mitigate the occurrence of nulls and to maintain the directions of the majority of the radio wave propagation towards the Earth-facing side. In the case of a small spacecraft, the MoM offers acceptable computing time and accuracy.

Optimizing TT&C antenna placement on minisatellites

The paper presents results of our studies on electrical properties of microstrip antennas mounted on minisatellites. The main feature of minisatellite antennas is a lightweight structure and a high degree of integration of antenna elements and feeding circuits. The antennas onboard minisatellites is divided into two groups: telecommand/housekeeping telemetry antennas (TT&C) and payload antennas. The main objective of the research is the optimization of antenna placement onboard the minisatelliate.

Airborne radar antenna modules using lightweight temperature-resistant materials

In contemporary radar technology, increasingly complex antennas must maintain a low weight requirement and provide sufficient robustness to a harsh environment. Among many desired features, a high degree of antenna integration and the ability to incorporate the design into an aeroplanes fuselage or wings are of the highest priority. In order to meet such demands, advanced power dividing and phasing networks together with digital signal processors should be located close to the transmitting and receiving antennas preferably in multilayer architectures. Such architectures put stringent requirements on the electrical and mechanical properties of dielectric substrates. This paper presents some results concerning the design and development of multilayer antenna elements and the associated signal dividing and phasing networks using honeycomb and quartz-fibre composite materials, which are widely used in the aerospace industry.