By Marcus C. Walden

Abstract: The design of a 16-element waveguide array employing radiating T-junctions that operates in the Ku band is described.

Amplitude weighting results in low elevation sidelobe levels, while impedance matching provides a satisfactory VSWR, that are both achieved over a wide bandwidth (15.7-17.2 GHz). Simulation and measurement results, that agree very well, are presented. The design forms part of a 16 x 40 element waveguide array that achieves high gain and narrow beamwidths for use in an electronic-scanning radar system.

I. INTRODUCTION: Design equations for optimum horn antennas have long been established [1]. This concept has been employed in an electronic-scanning ground surveillance radar system for nominal elevation beamwidths of 10° and 20°. Unfortunately, for narrower beamwidths, the optimum horn becomes impractically long for a man-portable system (e.g. for a desired 5° beamwidth, the length is ~1.5 m).

Because the antenna forms part of a 40-element array that defines the azimuth beamwidth, a 16-element waveguide array with a corporatefeed structure was selected to achieve the desired 5° elevation beamwidth with a short physical length.

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By Marcus C. Walden

Abstract: A lightweight, wideband tapered-slot antenna that uses an antipodal Vivaldi design and provides useable gain from ~5 GHz to in excess of 50 GHz is described. Simulations and measurements are presented that show excellent agreement. This antenna design is currently deployed in handheld test equipment.

I. INTRODUCTION: Numerous designs exist for wideband (multi-octave) antennas that also have good directivity. However, the selection pool reduces if the antenna is to be employed within handheld test and/or monitoring equipment. For example, the relative bulk and weight of standard gain or double-ridged waveguide horns is undesirable, as is their cost.

Microstrip antennas are attractive because they are, by comparison, lightweight and cheap. While a patch array is simple, its feed structure is more complicated and incurs losses, particularly at higher microwave frequencies. For desired operation from below ~20 GHz to above ~40 GHz, a tapered-slot or Vivaldi antenna was considered suitable [1]. Furthermore, an antipodal Vivaldi design was selected because it offers a simple microstrip-coax interface and provides good gain over a wide bandwidth [2].

Inevitably, some engineering design trade-offs are required.

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