Microstrip patch antennas are widely employed in several applications, thanks to their low profile, low cost, and easy manufacturing. However, the demand for new technologies providing compactness and high performance poses a long-lasting challenge for the antenna designer. Traditional methods for bandwidth improvement and size reduction have some drawbacks, tied mostly to poor radiation performance or troublesome implementation. In this letter, a novel, simple, but effective patch antenna layout exploiting the customizable form factor guaranteed by 3-D printing (or other fabrication techniques) is presented. An appropriate modification in the vertical profile of the radiator is introduced. Specifically, without loss of generality, a cylindrical shape has been selected as a proof of concept. The proposed solution allows to increase the impedance bandwidth from 2.9% of a standard flat microstrip patch to 9%. Additionally, the projected antenna resonant size can be reduced up to 38% compared to its flat counterpart.

A Curved 3-D Printed Microstrip Patch Antenna Layout for Bandwidth Enhancement and Size Reduction

This article proposes gain-enhanced circular patch antenna and array with introduction of multiple shorting pins. The antenna consists of a circular patch and several shorting pins. Equivalent inductance is brought to the patch after introducing shorting pins. Thus, resonance of the patch shifts at higher frequency. Compared to a conventional circular patch without any pins, radiation area of the proposed patch is enlarged given the same resonance frequency, hence leads to gain enhancement. The number of pins introduced to a circular patch can be set freely due to its symmetrical feature. Moreover, surface current is restricted within a small area around the center of the patch after introducing multiple pins, leading to more concentrated radiation. An equivalent circuit model is built for the proposed antenna. Layout and number optimization rules for introducing shorting pins are formulated. With these rules, gain of a circular patch can be maximized for the applications under certain size restrictions. A prototype operating at 5.8 GHz is designed and fabricated. Furthermore, a 2*2 array based on the gain-enhanced circular patch elements is implemented. In the measurements, high gain, high efficiency, and narrowed half-power beamwidth of the patch antenna and the array are observed.

High-Gain Circular Patch Antenna and Array With Introduction of Multiple Shorting Pins

For phased arrays used in satellite communications and radio astronomy, high sensitivity is required, and minimizing antenna losses is critical. Losses for single antennas can be minimized using high conductivity materials. It is less well understood that loss for array antennas is also influenced by mutual coupling between array elements and the beamformer weights applied to the signal from each element. In this paper, we study the antenna loss and receiving efficiency for phased array antennas and focal plane phased array feeds. To better elucidate the physics of array antenna loss related to mutual coupling and beamformer weights, losses for a coupled array can be lumped into an array effective resistance similar to the loss resistance of an equivalent single antenna. Numerical results show that although the antenna loss for a single isolated array element is low, the array antenna loss can be significantly increased by mutual coupling, particularly for beams with a large scan angle.

Antenna Loss and Receiving Efficiency for Mutually Coupled Arrays

Mid-air collisions (MACs) are commonly caused by temporary or permanent loss of flight control resulting in catastrophic damages and hence must be countered with suitable technology. The avionic industry has been using Traffic Alert and Collision Avoidance System (TCAS) for avoiding mid-air collisions since 1987. The TCAS either uses an Omni-directional antenna or a directional antenna for the surveillance of other nearby aircraft. The existing TCAS directional antennas, i.e., an array of monopole antennas are characterized by a maximum gain of 3.6 dB, which is regarded as low. As a result, many research has been carried out to find the alternative for the TCAS antenna and have found microstrip patch antenna (MPA) which yield some promising results such as feed flexibility, multiband, beam steering, etc. However, the MPA still suffers from disadvantages such as low gain and narrow bandwidth. Hence, lately, a tremendous amount of work has been carried out to enhance the gain of the MPA. In this paper, we first review the key methods that has been reported so far to improve the gain of the traditional TCAS antenna. We note that, in most of the reported work, conventional techniques such as parasitic patches, and shorting pins are used to improve the gain of MPA, and no substantial work was done using advanced techniques such as electromagnetic-band gap (EBG), metamaterials and metasurfaces. Hence, we further review the work that has been carried out to improve the gain of vertically polarized MPAs using advanced techniques for L- and S-band (up to 3 GHz). Many advanced structures that are easily adapted to enhance the gain of TCAS antenna are thoroughly discussed in this work.

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A Review on Gain Enhancement Techniques for Vertically Polarized Mid-Air Collision Avoidance Antenna for Airborne Applications

This paper presents a probe-fed compact multi-band microstrip patch antenna for wideband operation. The proposed antenna is composed of a shorted circular patch fed by folded-patch with a V...

Compact multi-band stacked circular patch antenna for wideband applications with enhanced gain

Reflector-based satellite communication (SatCom) terminals require high sensitivity to minimize overall antenna size, and in view of their simplicity and high radiation efficiency, horn antennas are used almost exclusively as reflector feeds. As these terminals become more complex, smaller and more compact feeds that can be directly integrated with microstrip circuits are desirable. Standard microstrip antennas (MSAs) have unacceptably low radiation efficiency for use as reflector feeds. We show that the stacked shorted annular patch (SSAP) can be used as a replacement for horn feeds and achieves higher radiation and spillover efficiencies than conventional patch antennas due to the absence of distribution networks and dielectric substrates. Using a half-wavelength stacked patch as a director realizes a pattern that achieves high illumination efficiency with standard parabolic reflector geometries. Simulation and measurements show that the compact SSAP may be the first reported nonwaveguide feed antenna to achieve sensitivity comparable to that of a conventional horn feed.

Kyle C. Browning

Papers

High-Efficiency Stacked Shorted Annular Patch Antenna Feed for Ku-Band Satellite Communications