High-Performance Smooth-Walled Horn Antennas for THz Frequency Range: Design and Evaluation

Abstract

Traditionally, corrugated conical horn antennas have been the main choice for use in astronomical receivers in the range of millimeter and submillimeter waves. They present low cross-polar level and high coupling efficiency into the fundamental Gaussian mode. However, this type of antenna is difficult to manufacture, inevitably increasing its price and extending the production process. In this article, we present two kinds of feed horn antennas, aimed for use in a frequency range equivalent to atacama large millimeter/submillimeter array (ALMA) Band 6 (211-275 GHz), which can be fabricated in a much simpler way with the conventional machining tools. Specifically, we present the design and performance comparison of smooth-walled spline-profile horns in two geometries, diagonal, and conical. Optimization of the designs has been made by means of an algorithm that allowed us to obtain models whose electrical and mechanical characteristics make them competitive when compared with corrugated horns. In particular, they are 40% shorter than the conventional corrugated horns suited for this band, representing an advantage given the stringent space constraints of most astronomical receivers. We also demonstrate that they can be coupled efficiently to an astronomical-grade optical system, using ALMA Band-6 receiver as an example. Furthermore, we have constructed the diagonal horn and characterized it thoroughly. Experimental results of the radiation pattern at room temperature show a good cross-polar performance with levels below −20 dB and Gaussicity above 96%. Our calculations show a good antenna-efficiency level with losses less than 1%. All these properties demonstrate the feasibility of this type of horns to become the main option at the time of choosing a feed system for cutting-edge astronomical applications.

Dual-Band Piecewise-Linear Profile Feed-Horns for the Copernicus Imaging Microwave Radiometer Mission

“…Among the possible feed-horn configurations, including corrugated [7]- [10], choked [11], and spline/piecewise-linear [12]- [16] architectures, the latter was selected for electromagnetic and mechanical reasons. Indeed, this architecture provides the degrees of freedoms necessary to synthesize the desired radiation patterns, while being a compact and lightweight solution compatible also with 3D printing technologies [15].…”

“…This architecture was initially introduced for implementing high-efficiency feed-horns in multi-beam antenna subsystems for high/very-high throughput communication satellites [13]], [14]. Then its applicability to radio-astronomy and astrophysics receivers was also investigated [12], [16].…”

Design of 94GHz Dual-Polarization Antenna Fed by Diagonal Horn for Cloud Radars

“…A three-dimensional (3D) printed cassegrain antenna for THz near-field focusing is used in back scattered side-channel detection, and the parameters and performance of 3D printed cassegrain antenna were analyzed in [7]. To achieve excellent gain, bandwidth, polarization, and radiation patterns, diagonal horn antennas are widely used in MMW and THz applications [8]- [10]. Two symmetrical pyramidal horn antennas are used to enhance electromagnetic signal collection and radiation in the sub-THz measurement system [8].…”

“…A modification of the traditional diagonal horn design using a spline-curve "S" shape modulation in the depth of the "V" groove was introduced in [9]. In [10], the performance of two smoothwalled spline-profile horns, conical and diagonal, was analyzed; the diagonal antenna was found to exhibit very good performance in terms of radiation, cross-polarization level , and efficiency. In [11], [12], dual-polarization cassegrain antenna is applied in W-band cloud radars.…”

A Fast and Accurate Method of Synthesizing X-Wave Launchers by Metallic Horns

“…Such horns are designed by optimizing their profile to match the far-field to a specified radiation pattern. Excellent characteristics of spline-profiled horns have also been reported, such as low cross-polarization [35], multiband operation [36], low sidelobe level [37], and high Gaussicity at THz frequencies [38], [39]. Performance of such antennas can be further improved by, for instance, integrating a dielectric lens [40], [41].…”