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Microstrip antennas are highly resonant structures and, for simple patch configurations, the bandwidths of each mode is quite small. As an antenna, their most useful mode is the TM11 mode that radiates in the broadside direction with a good gain. All other modes, TMnm, radiate conical beams with a null in the broadside and have a pattern peak that moves towards the endfire direction by increasing...
The radiation characteristics of conical reflectors with a line source feed in the form of an array of dipoles are derived using a numerical integration of the physical optics currents. Representative radiation patterns are computed and presented.
A conventional transmit system design comprises a high gain antenna followed by a solid state power amplifier (SSPA). However, the SSPA used within a transmit system have in general multiple devices to provide the high output power and suffers from the combining losses within the unit. To reduce these losses, low to medium power amplifiers are integrated within an array architecture. Spatial power...
For the Synthetic Aperture Radar (SAR) applications antenna candidates with dual-polarized dual-band capability are investigated. The microstrip technology is considered and several antenna configurations are selected, analyzed, designed and evaluated. Here, three different candidates are presented that use different combinations of substrates and antenna geometries. Their performance is briefly reviewed...
Shaped beam reflector antennas are commonly used in satellite communications applications where performance considerations other than high gain may be of importance. For large antennas, the feed and reflector are usually considered to be uncoupled and are analysed separately [1]. The analysis of the feed requires a more exact solution technique with an integral equation formulation or mode expansion...
A circularly polarized dielectric resonator antenna has been developed recently for K-Band applications [1]. A microstrip aperture-coupled dielectric resonator element in the shape of a cross was designed as a feed element for a cylindrical cavity antenna. The analysis was performed using a Finite Difference Time Domain (FD-TD) method [2]. As part of the continuing development of this antenna, it...
The rapid growth of spectral utilization has necessitated the progress toward higher frequency bands to resolve the spectral crowding problem. However, before the successful transition to higher frequency bands can be realized, critical components and appropriate tools such as propagation modelling need to be developed. In the millimeter-wave band, many of these technologies have progressed rapidly...
A novel smart antenna based on metamaterial consisting of cut-wire metal rods which are formed a circle is presented. The antenna can operate in both directional and omnidirectional modes by choosing different the feed source automatically and adjusting the amplitude and phase of the feed source. The proposed designs can be used in high-speed communication networks.
A novel adaptive aperture antenna is presented. It can provide adaptive phase centre locations within a single aperture. It can be used to virtually make more than one antenna by controlling the excitation modes of the multimode primary feed illuminating the aperture. In this paper, the selected aperture is an offset reflector antenna fed by a dual-mode stacked microstrip. The resulting antenna has...
This work has studied and successfully demonstrated the ability of patch-array covers placed over PAF feeds comprising waveguide elements for achieving improved coupling and aperture efficiencies of singly-steered as well as multiple-overlapping beams, as compared to those of uncovered PAF feeds. Future work would be to include dielectric losses into the studies. Preliminary results are expected to...
This paper investigates the performance of two different feed structures for Vivaldi antennas. It is shown that cross polarization performance depends on both guiding and feed regions. The effect of feed region is very important and cross polarization can be decreased by reducing the feed radiation. The performance of a double layer Vivaldi antenna fed by stripline and a single layer one fed by Y2Y...
In this paper, the performance of small circular waveguide feeds with E- and H-plane slots is investigated. The slots are categorized by small and large slots depending on slot length. It is shown that for small slots, pattern broadening is possible with equal E- and H- plane patterns, at the expense of cross-polarization. For large slots, identical E- and H-plane pattern with pattern broadening is...
The effect of a dual-mode circular horn antenna, as a feed in offset reflector antennas, on the crosspolarization field is studied using the physical optics, geometrical optics, and geometrical theory of diffraction software GRASP. It will be shown that, one can reduce the crosspolarization of an offset reflector antenna by properly exciting two modes in circular horn antenna. These two modes are...
In this paper, a new compact microstrip square ring antenna is presented, which can be operated at multiple frequencies. It can be stated that within a stacked microstrip square ring configuration, a third square ring is accommodated, which operates at a higher frequency than that of the stacked configuration. Thus, three resonators are arranged in a compact form and fed capacitively to successfully...
A new application for reflector antennas is proposed and developed. Using the aperture theory, a phase center on the reflector aperture is determined and shown that, its location is dependent on the field distribution. The proposed concept is, initially, verified by using a symmetric reflector. It is shown that the phase center is located at the aperture geometric center, when the reflector is illuminated...
Triplate line fed arrays have been researched extensively over the last 10 years for DBS television subscriber antenna in Japan and Europe. The chief advantage of this type of planar array is the reduction of radiation from the array's feedlines. One class of triplate fed array employs a thin metal sheet with apertures punched for radiation from patches on the triplate layer [1], Figure 1. This type...
Local multi-point communication services, LMCS, is targeted for operation around 28 GHz with an initial bandwidth of 1 GHz. Different service scenarios are under investigation, and a preliminary multi-cell configuration assumes four transmitters per site alternating between vertical and horizontal polarizations. The beam widths will, of course, depend on the cell configuration and for the above four...
The design process of a corporate-fed microstrip patch antenna array relies on the aperture theory, and microstrip circuits design equations. Such an approach usually neglects mutual coupling between array elements, which is known to degrade the array performance. The design of the individual antenna elements can be a straight forward process for canonical shapes on single layer substrates. On the...
A general study on phased array is undertaken to evaluate the array performance in terms of its lattice structure, gain and sidelobe levels. For the array geometry both rectangular and circular shapes are considered and their performance for fully scanned and switched beam arrays is studied. The performance of arrays in G/T is also studied and estimated costs for each array are provided.
Aperture-coupled microstrip antennas have been developed for operation in the millimeter wave region. A combination of patch dimensions and aperture size determines the antenna's resonating frequency. The measured return loss indicated an achievable bandwidth of 1.2% for a VSWR of less than 2:1. The measured radiation patterns at 45 GHz display the expected characteristics of microstrip patch antennas...
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