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°.

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.

This paper presents a Ku -band (14-16 GHz) CMOS frequency-modulated continuous-wave (FMCW) radar transceiver developed to measure dry-snow depth for water management purposes and to aid in retrieval of snow water equivalent. An on-chip direct digital frequency synthesizer and digital-to-analog converter digitally generates a chirping waveform which then drives a ring oscillator-based Ku -Band phase-locked loop to provide the final Ku -band FMCW signal. Employing a ring oscillator as opposed to a tuned inductor-based oscillator (LC-VCO) allows the radar to achieve wide chirp bandwidth resulting in a higher axial resolution (7.5 cm), which is needed to accurately quantify the snowpack profile. The demonstrated radar chip is fabricated in a 65-nm CMOS process. The chip consumes 252.4 mW of power under 1.1-V supply, making its payload requirements suitable for observations from a small unmanned aerial vehicle.

A combination 95 GHz radar and 270/560 GHz spectrometer is being built as a space instrument prototype for probing plumes and jet phenomena in the solar system. Dubbed GAISR (Gas And Ice Spectrometer/Radar), the instrument's radar will make simultaneous range/Doppler measurements of 0.1-10 mm sized ice and dust particles out to a few km in range, while its tunable spectrometer will detect the abundance and velocities of gaseous water and other volatiles. Here we describe how the radar and spectrometer share a back-end architecture, and present some innovative elements of GAISR's frequency-modulated continuous-wave (FMCW) radar, including high-isolation and low-loss transmit/receive duplexing and a phase-noise-canceling RF architecture.

We designed and microfabricated a (2×2) silicon platelet horn antenna at 560 GHz, which is the highest frequency ever among silicon corrugated horn antennas. This was enabled by a silicon compression pin alignment technique of which inaccuracy is less than ± 2 μm in layer-to-layer. The simulation results show that the return loss and gain across the operation frequency of 490-600 GHz are approximately 25 dB and 22 dBi, respectively. The cross-polarization level is below -40 dB. The feature of batch processing will enable us simultaneously to build hundreds or thousands of horn antennas.

The development at 1.9 THz of a microlens antenna consisting of a leaky-wave waveguide feeding and a silicon microlens is presented in this paper. The antenna has excellent performances compared to horn antennas and can be fabricated entirely using silicon micromachining. Two antenna prototypes were developed: one with a 2.6-mm-diameter microlens and a directivity of 33.2 dB and the other with a 6.35-mm-diameter microlens and a directivity of 41.2 dB. Both prototypes were fabricated and measured, obtaining good agreements with simulations. The fabrication, assembly, and measurement process are explained and detailed in this paper.

This paper describes the design and realization of a modulated metasurface (MTS) antenna at 300 GHz. To overcome the hurdles associated with the use of dielectric substrates in the sub-millimeter wave range, we propose an MTS structure which consists of an array of metalized cylinders placed on a ground plane. The metal cylinders are arranged in a square lattice with sub-wavelength unit cell size. This MTS topology has been successfully used to design a spiral MTS antenna. The resulting structure has been micromachined out of a silicon wafer by means of deep reactive ion etching (DRIE). The performance of the antenna has been verified by full-wave simulations, and measurements will be available at the time of the conference.

Using newly developed silicon micromachining technology that enables low-loss and highly integrated packaging solutions, we are developing vertically stacked transmitters and receivers at terahertz frequencies that can be used for communication and other terahertz systems. Although there are multiple ways to address the problem of interconnect and packaging solutions at these frequencies, such as system-on-package (SOP), multi-chip modules (MCM), substrate integrated waveguide (SIW), liquid crystal polymer (LCP) based multilayer technologies, and others, we show that deep reactive ion etching (DRIE) based silicon micromachining with vertical integration allows the most effective solutions at terahertz frequencies.

We explore the use of a class of metasurface (MTS), which consists of metalized cylinders arranged in a square lattice and placed on a ground plane, for the realization of antennas at terahertz (THz) frequencies. This MTS is particularly appropriate for being micromachined out of a silicon wafer by means of deep reactive ion etching (DRIE).

Using newly developed silicon micromachining technology that enables low-mass and highly integrated receivers, we are developing state-of-the-art terahertz spectrometer instruments for space-based planetary and astrophysics orbiter missions. Our flexible receiver with integrated antenna architecture provides a powerful instrument capability in a light-weight, low-power consuming compact package which offer unprecedented sensitivity performance, spectral coverage, and scalability to meet the scientific requirements of multiple missions.

In this paper, we have microfabricated a 6.4 mm diameter silicon lens array on a 4 inch silicon wafer using silicon micromachining technique. The goal of this lens array is to build a 2×2 lens antenna array for 1.9 THz receiver application. It requires multiple thick photoresist coatings and long selective etching of silicon and photoresist after thermal reflow process. To the authors' knowledge, this is the biggest silicon lens ever microfabricated by semiconductor process.

Increasingly, terahertz systems are being used for multi-pixel receivers for different applications from mapping the star-forming regions of galaxies to stand-off radar imaging. Since microstrip patch antennas are too lossy and corrugated horn antenna arrays are difficult to machine at terahertz frequencies, suitable antenna array designs have been one of the key area of research for this field. Moreover, silicon micromachined waveguide housing for front-end integration is becoming very popular for multi-pixel terahertz instruments. This paper describes multi-pixel terahertz instruments with silicon-micromachined front-end and discusses design challenges for integrating terahertz antennas with such systems.

This contribution presents the last developments of THz antenna arrays based on silicon micro-machined lenses for heterodyne receivers. The antenna proposed in this manuscript consists of a leaky waveguide feed that illuminates a shallow lens. It achieves high efficiencies and a good coupling to optical systems. Moreover it can be fabricated in parallel using silicon micro-machining techniques, obtaining an array of reduced size and mass to be used for space applications. The current focus of our research is the design of an antenna array operating at 1.9THz based on this antenna for astronomy applications.