It is difficult to package and interconnect components and devices at millimeter-waves (mm-waves) due to excessive losses experiences at these frequencies using traditional techniques. The problem is multiplied manifold at terahertz (THz) frequencies. In this article, we review the current state of THz packaging and describe several novel techniques. As we will show, micromachined packaging is emerging as one of the best choices for developing advanced THz systems.@en

Terahertz heterodyne spectrometer instruments have been traditionally limited to a single pixel or a handful of pixels due to integration and assembly constraints and a limited availability of local oscillator (LO) power. As a solution we propose a novel silicon-micromachined planar and modular packaging strategy, that will allow for a dense integration of a large number of pixels. Moreover, the RF- and LO signals will be quasi-optically coupled via two identical but opposite lens arrays, such that a single LO-source can efficiently pump all HEB-mixers of the 2x2 pixel demonstrator array simultaneously. This work reports on an intermediate step, where we validate the lens array performance and LO power coupling efficiency, by slightly modifying the silicon package into a transmit array configuration. In this way, the LO power coupled into the stack is directly reradiated on the other side, which is then measured using a liquid helium cooled bolometer.@en

This paper presents an overview of a sub-orbital flight demonstration with a 183 GHz and 540–600 GHz limb-sounding instrument aboard a stratospheric ballooncraft. The 183 GHz band provides soundings of stratospheric H 2 O and is implemented with a hybrid CMOS-InP receiver architecture which provides excellent sensitivity while remaining compact (162 g) and offering an extremely low DC power consumption (0.62 W). The 540–600 GHz channel sounds stratospheric O 3 and uses a combination of a CMOS local oscillator, GaAs Schottky mixer and micro-electro-mechanical-system (MEMS) RF switch for calibration, again offering competitive form factor (1.4 Kg) and low DC power consumption (6.6 W) compared to prior instruments. The instrument was flown on the NASA Reck-Tang Limb-sounding Experiment (ReckTangLE) ballooncraft and performed atmospheric soundings across New Mexico and Northwestern Texas on Oct. 17 2019.@en

In this paper, we present a quasi-optical power distribution architecture based on the use of an integrated lens antenna that generates a uniform aperture field distribution. By using such distribution in combination with an integrated lens array, an efficient and scalable quasi-optical power distribution can be achieved at THz frequencies. The proposed architecture is based on a leaky-wave waveguide feed that illuminates an elliptical lens with a top-hat distribution. This method can distribute the power from one antenna to a 7-pixel lens array in a hexagonal configuration with a power coupling efficiency of nearly 60%. This scheme could be potentially used for the local oscillator power distribution in heterodyne THz arrays. A prototype at 450-615GHz has been developed and characterized, achieving an aperture efficiency higher than 80%. @en

In this article, we propose a hybrid electromechanical scanning lens antenna array architecture suitable for the steering of highly directive beams at submillimeter wavelengths with field-of-views (FoV) of ±25°. The concept relies on combining electronic phase shifting of a sparse array with a mechanical translation of a lens array. The use of a sparse-phased array significantly simplifies the RF front-end (number of active components, routing, thermal problems), while the translation of a lens array steers the element patterns to angles off-broadside, reducing the impact of grating lobes over a wide FoV. The mechanical translation required for the lens array is also significantly reduced compared to a single large lens, leading to faster and low-power mechanical implementation. In order to achieve wide bandwidth and large steering angles, a novel leaky wave lens feed concept is also implemented. A 550-GHz prototype was fabricated and measured demonstrating the scanning capabilities of the embedded element pattern and the radiation performance of the leaky wave fed antenna.@en

The development of a low focal number and low-mass lens antenna is presented that enables terahertz spectroscopy applications on ultracompact platforms. The antenna operates efficiently over a 20% fractional bandwidth, from 450 to 550 GHz, with a gain of 50 dBi at 500 GHz. The antenna consists of a hyperbolic silicon lens that is placed in a record low focal number configuration (f#=0.27) with respect to an advanced waveguide feed. An incident field-matching analysis is applied to investigate the optimal feed radiation pattern that maximizes the lens aperture efficiency, which would result in a 20% increase in aperture efficiency (> 80%) with respect to a standard open-ended waveguide (< 60% aperture efficiency). A multilayer leaky-wave (LW) stratification is quasi-analytically optimized to approximate the optimal feeding pattern, resulting in a >70% lens aperture efficiency. An example LW stratification is synthesized using silicon micromachining technology and is fully characterized in combination with the dielectric lens. @en

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°.@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

The performance of a CMOS transmitter designed for planetary science in-situ molecular sensing applications having an operational bandwidth of 180-190 GHz and peak output power of 0.6 mW (-2.22 dBm) is evaluated with a series of spectroscopic-based experimental trials. Continuous wave frequency modulated absorption schemes are exploited to probe the Doppler and sub-Doppler lineshape profiles of the water rotational transition at 183.310 GHz. These results demonstrate the tuning finesse and phase-noise characteristics of the integrated circuit embedded phase lock loop used to generate coherent mm-wave radiation are sufficient for high-precision molecular spectroscopy applications. A description of the pulse modulator designed into the CMOS circuitry allowing for implementation of sensitive emission-based Fourier transform detection schemes is provided with performance characterized for spectroscopically relevant pulse durations (40-500 ns). Results are accompanied by a spectral analysis of the transmitter pulse signal leakage where the total isolation is measured to be 22 dB. The first emission-based molecular detections obtained with this source are presented demonstrating viability for this transmitter to be incorporated into future planned resonant cavity enhanced in-situ molecular sensing systems.@en

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.@en

This letter presents a numerical study of the best performance achievable using a spherical reflector with a point feed and without any corrective element. We evaluate in detail the aperture efficiency that can be obtained with a spherical reflector with linearly polarized Gaussian beam illumination. A 100 GHz, 30 cm diameter spherical reflector from a parent sphere of 30 cm radius has been built and measured. The maximum directivity of 46.1 dB agrees closely with the predictions of electromagnetic modeling, as does the increase in the directivity by more than 3 dB resulting from moving the feed by 0.7 cm closer to the reflective surface relative to the paraxial focal point.@en

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.@en

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.@en

NASA's Planetary Science Decadal Survey has concluded that isotopic measurements of cometary water vapor are a means to unraveling the mysteries involving the origin of Earth's water and the evolution of our solar system. To support this, a recent Jet Propulsion Laboratory internal research program has developed quantum limited superconductor-insulator-superconductor (SIS) receivers in the important 500-600 GHz submillimeter frequency band. These instruments can be used to detect the deuterated water (HDO) ground state (110-101), H216O ortho ground state (110-101), and the oxygen isotopologues H217O and H218O with exquisite sensitivity. To achieve the presented results, we have investigated aluminum oxide (AlOx) and aluminum nitride (AlNx) barrier SIS tunnel junction mixers on the 6-μm silicon-on-insulator substrate. The AlOx and AlNx junction mixer blocks utilize diagonal and smooth-profile conical horns, respectively. In both cases, a commercial 4-8-GHz intermediate frequency low-noise amplifier (LNA) has been integrated into the mixer block. The AlOx (low-current-density) barrier SIS junctions were fabricated with 2-μm gold beam-lead technology, whereas in the case of the AlNx SIS tunnel junction, we use capacitive RF decoupling tabs. The latter approach simplifies fabrication, increases yield, eases the mounting process, and facilitates scaling to higher frequencies. For an actual flight mission, with operation ≤4.2 K, the allowed heat dissipation of the mixer-integrated LNA needs to be minimized. In this article, we also investigate the receiver sensitivity as a function of the LNA dc power consumption. We find that the dc power consumption of the LNA can be reduced to ∼1.6 mW with minimal loss in sensitivity. It is anticipated that the continued InP HEMT development for quantum computer applications are likely to reduce the required LNA power dissipation even further.@en

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.@en

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.@en

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.@en

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

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.@en