A simple mechanical beam steering antenna concept is proposed for ground mobile terminals of Ka-band satellite and high altitude platform (HAP) providing broadband access services. The wide-angle elevation beam steering is achieved by in-plane translation of a thin offset flat lens in front of a stationary primary feed while full azimuth coverage is obtained by simple 360° rotation of the lens. A new strategy is also proposed to reduce the effective F/D of the focusing system and consequently the total antenna height without increasing beam distortion: a second small flat lens is added on top of the primary feed to create a virtual focus located well below the feed phase center. The challenge is to conciliate high gain both with wide beam scanning and reduced antenna height. Design rules are presented for this antenna concept along with a 27.3-dBi gain fabricated example for the up-link Ka-band (29.5–30 GHz), with circular polarization, 0° to 50° elevation scan, better than 2.8-dB scan loss and an effective F/D of only 0.55. Both lenses are 3.35-mm thick, formed by a suitable assembly of phase shifting unit cells with less than 0.4 dB of transmission loss in simulation. The main lens dimensions are $195\;\text{mm} \times 145\;\text{mm}$ and its weight is 215 g. Total antenna height, including the feed is 84 mm.

Circular Polarization Wide-Angle Beam Steering at Ka-Band by In-Plane Translation of a Plate Lens Antenna

Transmit array design is more challenging for dual-band operation than for single band, due to the independent 360° phase wrapping jumps needed at each band when large electrical length compensation is involved. This happens when aiming at large gains, typically above 25 dBi with beam scanning and $F/D \le 1$ . No such designs have been reported in the literature. A general method is presented here to reduce the complexity of dual-band transmit array design, valid for arbitrarily large phase error compensation and any band ratio, using a finite number of different unit cells. The procedure is demonstrated for two offset transmit array implementations operating in circular polarization at 20 GHz(Rx) and 30 GHz(Tx) for Ka-band satellite-on-the-move terminals with mechanical beam-steering. An appropriate set of 30 dual-band unit cells is developed with transmission coefficient greater than −0.9 dB. The full-size transmit array is characterized by full-wave simulation enabling elevation beam scanning over 0°–50° with gains reaching 26 dBi at 20 GHz and 29 dBi at 30 GHz. A smaller prototype was fabricated and measured, showing a measured gain of 24 dBi at 20 GHz and 27 dBi at 30 GHz. In both cases, the beam pointing direction is coincident over the two frequency bands, and thus confirming the proposed design procedure.

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High Gain Dual-Band Beam-Steering Transmit Array for Satcom Terminals at Ka-Band

Thin artificial surfaces that act as high frequency bandgap structures have been recently studied for the design of gap waveguides, hard surfaces, and planar lenses. Here, we propose a circuit-based method to analyze glide-symmetric corrugated metasurfaces that are embedded in a thin parallel plate waveguide. Our closed-form solution is based on rigorous analytical derivations. It achieves remarkable agreement with full-wave solvers, even when the waveguide thickness is extremely thin. In contrast, classical homogenization approaches are shown to be inaccurate for thin waveguides due to the interaction of higher order Floquet modes between the surfaces. Numerical results validate our theoretical analysis and show the utility of the proposed method.

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Accurate Equivalent-Circuit Descriptions of Thin Glide-Symmetric Corrugated Metasurfaces

This paper presents a flat, high gain, wide scanning, broadband continuous transverse stub (CTS) array. The design procedure, the fabrication, and an exhaustive antenna characterization are described in details. The array comprises 16 radiating slots and is fed by a corporate-feed network in hollow parallel plate waveguide (PPW) technology. A pillbox-based linear source illuminates the corporate network and allows for beam steering. The antenna is designed by using an ad hoc mode matching code recently developed for CTS arrays, providing design guidelines. The assembly technique ensures the electrical contact among the various stages of the network without using any electromagnetic choke and any bonding process. The main beam of the antenna is mechanically steered over $\pm 40^\circ$ in elevation, by moving a compact horn within the focal plane of the pillbox feeding system. Excellent performances are achieved. The features of the beam are stable within the design 27.5–31 GHz band and beyond, in the entire Ka-band (26.5–40 GHz). An antenna gain of about 29 dBi is measured at broadside at 29.25 GHz and scan losses lower than 2 dB are reported at $\pm 40^\circ$ . The antenna efficiency exceeds 80% in the whole scan range. The very good agreement between measurements and simulations validates the design procedure. The proposed design is suitable for Satcom Ka-band terminals in moving platforms, e.g., trains and planes, and also for mobile ground stations, as a multibeam sectorial antenna.

/pdf/continuous-transverse-stub-array-for-ka-band-applications-zc3ehhn5uv.pdf

Continuous Transverse Stub Array for Ka-Band Applications

We study the wave propagation between two glide-symmetric metallic plates drilled with periodic rectangular holes. A mode-matching method is proposed in order to derive efficiently the dispersive properties of these periodic structures. The method takes advantage of the higher symmetry of the structure reducing the computational cost by enforcing boundary conditions on the field on only one of the two surfaces. Physical insight on specific symmetry properties of Floquet harmonics in glide-symmetric structures is also gained. The code is validated with commercial software assessing its accuracy when varying the most influential/critical parameters. We confirm the potential of glide-symmetric structures to tune the effective refractive index. Specifically, we demonstrate that glide-symmetric structures with rectangular shapes can be employed to synthesize anisotropic refractive indexes with a large band of operation, which makes such metasurface structures applicable for the realization of ultrawideband planar lenses.

/pdf/glide-symmetric-all-metal-holey-metasurfaces-for-low-x58m2lp14q.pdf

Glide-Symmetric All-Metal Holey Metasurfaces for Low-Dispersive Artificial Materials: Modeling and Properties

The growing need for bidirectional mobile satellite communications in the Ka-band necessitates the development of dedicated antenna systems. In this article, we describe two different solutions for mobile user-terminal antennas intended for an operation in emergency scenarios. The first solution, a high-gain antenna, consists of a Cassegrain reflector, fed from a multimode monopulse tracking system for circular polarization at a satellite downlink frequency of 20 GHz. The structure is operational at 30 GHz to cover the uplink frequency range. The antenna system is mounted on a high-performance mechanical positioner to facilitate a fast compensation of the movements of the carrier vehicle. The second solution, a low-profile antenna, consists of leaky-wave antenna (LWA) panels employing two-layer partially reflective surfaces (PRSs). A hybrid tracking technique is used, and a unique feature of this antenna is its dual-band operation, to overcome the challenge of widely separated uplink and downlink ranges in the Ka-band. This article describes the design of the two types of antennas and analyzes the measurement results. Furthermore, tracking issues considered from the view of control engineering are addressed, and an evaluation of tracking accuracy is presented.

Ka-Band User Terminal Antennas for Satellite Communications [Antenna Applications Corner]

The growing interest in bi-directional mobile satellite communications in Ka-band necessitates the development of dedicated antenna systems and feeds. In this paper we describe a mobile satellite communications terminal with a cassegrain reflector antenna fed from a multimode monopulse tracking system for circular polarisation at the satellite downlink frequency of 20 GHz. The structure is operational at 30 GHz as well, to cover the uplink frequency range. The antenna system is mounted on a high-performance mechanical positioner to facilitate a fast compensation of the movements of the carrier vehicle. This work contributes to the development of a satellite terminal for mobile communications in disaster scenarios [1].

A dual-band multimode monopulse tracking antenna for land-mobile satellite communications in Ka-band

A satellite tracking antenna for mobile satellite communications in Ka-band was developed, employing a conical scan produced with a tilted and fast rotating sub-reflector. This tracking technique facilitates a simple and low-cost dual-frequency feed structure suitable for bidirectional operation. Two separate tracking voltages are generated by the system — one for elevation and one for azimuth. The antenna is able to detect misalignments up to 2° from the satellite direction with a bandwidth of 20 Hz.

Tracking antenna for mobile bi-directional satellite communications in Ka-band

The growing interest in bi-directional mobile satellite communications in Ka-band necessitates the development of dedicated antenna systems and feeds. In this paper we describe an operational feeding structure for a Cassegrain satellite reflector antenna which facilitates a multimode monopulse tracking system for circular polarisation at the satellite downlink frequency of 20 GHz. The basic principle can be extended to dual-band functionality, to cover the uplink at 30 GHz as well. This work contributes to the development of a satellite terminal for mobile communications in disaster scenarios [1], [2].

Multimode monopulse tracking feed with dual-band potential for land-mobile satellite communications in Ka-band

This paper describes the design and testing of a circularly polarised dual-band leaky-wave antenna panel operating at 20 and 30 GHz. The compact panel fits into a low-profile user-terminal antenna concept intended for mobile bidirectional Ka-band satellite communications. As a proof-of-principle, a dual-band partially reflective surface (PRS) with a physical aperture of 60 mm by 60 mm was manufactured and tested. Numerical simulations and measurement results prove the principle of operation.

Alexander Krauss

Papers

Ka-Band User Terminal Antennas for Satellite Communications [Antenna Applications Corner]

A dual-band multimode monopulse tracking antenna for land-mobile satellite communications in Ka-band

Tracking antenna for mobile bi-directional satellite communications in Ka-band

Multimode monopulse tracking feed with dual-band potential for land-mobile satellite communications in Ka-band

A dual-band circularly-polarised leaky-wave antenna for mobile Ka-band satellite communications