The radiation and losses in microstrip antennas with a corporate feed network are studied. A surface current approach is applied in which the electrical currents in the feed lines are modeled as in ideal transmission lines. The free-space radiation and the surface-wave excitation of typical segments in printed feed networks are studied. A four-element array antenna with its printed feed network is analyzed and predicted radiation patterns, directivity, and gain are presented and compared with experimental results. The gain and directivity of large arrays of 16, 64, 256 and 1024 elements are calculated and measurements in the frequency range of 10 to 35 GHz are reported. >

A study of microstrip array antennas with the feed network

Metamaterial surfaces (metasurfaces) can generate tailored electromagnetic wavefronts with spatially varying phase and polarization profiles. In this study a common Gaussian beam is transformed into a vector Bessel beam, which is useful for particle trapping, near-field probes, and laser machining. Going forward, the design and fabrication methodology presented here could be used to create efficient metasurfaces even at optical wavelengths, enabling applications such as tractor beams in compact nanoscale devices.

Controlling Vector Bessel Beams with Metasurfaces

We design and fabricate various sizes of 76-GHz post-wall waveguide-fed parallel-plate slot arrays. The post-wall waveguide is an array of metalized via-holes with a narrow spacing in a grounded dielectric substrate. The antenna can be easily made at low cost by conventional PCB (printed circuit board) fabrication techniques such as via-holing, metal plating, and etching. We have obtained 40-50% efficiency for various sizes from 26 mm/spl times/24 mm to 104 mm/spl times/100 mm. We have measured 35.3 dBi gain with 39.3% efficiency at 77.0 GHz in an antenna sized 104 mm/spl times/100 mm.

Efficiency of 76-GHz post-wall waveguide-fed parallel-plate slot arrays

A single-layered radial line slot antenna (RLSA) is proposed for a direct broadcast from a satellite (DBS) subscriber antenna. It utilizes a radially outward-traveling wave and the aperture field is intolerably tapered if the uniform slots are used. Two novel techniques are applied. First, the slot design for uniform aperture field distribution is introduced. Second, the radial line is terminated by a matching spiral, in place of a dummy load. It suppresses reflection and radiates all the residual power in circular polarization. For a model antenna of 600-mm diameter, the efficiency of 65% is observed. >

A slot design for uniform aperture field distribution in single-layered radial line slot antennas

The waveguide-fed metasurface is an emerging concept for beam forming and wave-front shaping, with applications that include satellite and terrestrial communication, radar, rf imaging, and wireless power transfer. The present work provides in-depth analysis of metasurface antenna operation. A set of simple, closed-form analytical expressions can be used to quickly assess the radiation characteristics for a range of designs. These simple yet compelling guidelines should help to actualize the significant potential of metasurface antennas for dynamically reconfigurable apertures.

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Analysis of a Waveguide-Fed Metasurface Antenna

The analysis and design of novel planar antennas which can radiate circularly polarized pencil beams in x -band are presented for the application of receiving direct broadcast from a satellite (DBS). This antenna belongs to a class of slotted waveguide antennas and high efficiency is expected in principle. A circular two-dimensional aperture is located on the top plate of a twofold radial waveguide and is excited by a radially inward traveling transverse electromagnetic (TEM) mode in the upper waveguide. Slots are arrayed on the aperture spirally in such a way that they can couple with the radial currents flowing over the aperture plate to produce a circularly polarized broadside beam. Promising performances of the antenna are predicted theoretically. Experiments are performed with respect to basic characteristics of the antenna and they show the validity of the design and analysis.

Y. Ito

Papers

A radial line slot antenna for 12 GHz satellite TV reception