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By Marcus C. Walden

Abstract: This paper presents the antenna G/T degradation incurred when communications systems use very inefficient receive antennas. This work is relevant when considering propagation predictions at HF (2-30 MHz), where it is commonly assumed that antennas are efficient/lossless and external noise dominates over internally generated noise at the receiver. Knowledge of the antenna G/T degradation enables correction of potentially optimistic HF predictions. Simple rules-of-thumb are provided to identify scenarios when receive signal-to-noise ratios might be degraded.

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By Marcus C. Walden

Abstract: This paper describes the design and characterization of a frequency-scanning meanderline antenna for operation at 60 GHz. The design incorporates SIW techniques and slot radiating elements. The amplitude profile across the antenna aperture has been weighted to reduce sidelobe levels, which makes the design attractive for radar applications. Measured performance agrees with simulations, and the achieved beam profile and sidelobe levels are better than previously documented frequency-scanning designs at V and W bands.

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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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