In this review paper we explore different antenna technologies at terahertz frequencies for space science and other applications. We show that the antenna technologies generally used at lower frequencies are difficult to implement at terahertz frequencies. Additionally, one has to take a few extra steps and special care for designing antennas for space-based applications. In this paper, we review different design and implementation options for millimeter-wave and terahertz antennas for space applications. We detail how antenna design has to be a part of the overall system design for the success of the instruments for space missions. We also look into low-mass and low-profile conformal antenna technologies that will have a profound impact on future space instruments at terahertz frequencies.

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We have demonstrated corrugated horn antennas at 340 GHz and 560 GHz fabricated with deep reactive ion etching (DRIE) process on silicon. The measurement of a single 340 GHz antenna showed that the return loss and gain are approximately 25 dB and 21 dBi, respectively. The measurement of two of the 2x2 560 GHz array antenna showed that the return loss and directivity are 13 dB and 22 dB, respectively. All of the measured antennas had below -25 dB of the cross-polarization and symmetrical beam patterns. The silicon microfabrication technique allows fabrication of hundreds of horn antennas at once, allowing construction of multi-pixel heterodyne imagers and spectrometers at submillimeter wavelengths.

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This paper presents a lens antenna that scans the beam using an integrated piezomotor at submillimeter-wave frequencies. The lens antenna is based on the concept presented by Llombart et al. in 2011, a leaky-wave waveguide feed in order to achieve wide angle scanning and seamless integration with the receiver. The lens is translated from the origin of the waveguide producing the scanning of the beam over a 50° field of view (FoV) (or about 6.25 beamwidths) with a maximum scanning loss of 1 dB. The lens movement is achieved with a piezoelectric motor that is integrated within the antenna and receiver block. A prototype was built and measured at 550 GHz achieving scanning beam angles close to 20° with only 0.6 dB of loss. The scanning of the 50° FoV, which corresponds to a lens displacement of approximately 2 mm, takes about 0.9 s achieving a scanning rate of 0.75 Hz of the FoV. The accuracy in continuous mode of the piezoactuator has been measured to be less than 28 μ in the worse of cases for displacements of 2 mm, which corresponds to a beam steering of 0.76°, much smaller than the antenna half-power beamwidth of 8°.

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Terahertz antennas present a different set of challenges to the antenna designer typically striving for very high performance while at the very limit of the chosen fabrication process. Many of the same design techniques used at lower frequencies are still applied, but fabrication constraints impose significant limitations on the type of structure that can be used, forcing the designer to consider unique fabrication processes or completely new antenna structures. Through advances in fabrication and computational techniques, the variety of terahertz antennas is growing. This chapter presents a range of antennas applied at these frequencies from 1.9 THz horn antennas to superconducting planar arrays. The chapter will cover different antenna technologies and feeds such as corrugated horn antennas, smooth-walled profiled horn antennas, multi-flare angle horn antennas, lens antennas, microlens leaky wave antennas, metasurface antennas, antenna arrays, off-chip antennas, and others. It will detail theory, simulation, fabrication techniques, and state-of-the-art antenna results in all these different technologies at millimeter and terahertz frequencies. The chapter will also provide details for terahertz antennas in the context of terahertz systems.

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The aim of this paper is to present an integrated beam-scanning antenna for a submillimeter wave instrument. The ultimate goal is to be able to scan the limb of the Martian surface to measure the wind, temperature and water vapor. The scanning of the limb can be achieved by the mechanical translation of a micro-lens using a piezo-electric motor integrated with the receiver. A prototype has been fabricated and measured at 550 GHz, achieving a scanning loss lower than 0.4 dB for beam angles up to 15 degrees.@en

This article presents the latest developments of our work related to a micro-lens antenna integrated in a heterodyne receiver using silicon micromachining technology at Terahertz frequencies. The antenna is composed of a waveguide feed which uses a leaky wave cavity to enhance the directivity and illuminate a shallow lens efficiently. The receiver is a dual-polarized balanced heterodyne detector using hot-electron bolometers (HEB) as mixers. The front-end receiver, including the antenna, can be fabricated using silicon micromachining processes and has seamless integration, which reduces the overall size and losses.@en