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

This article presents a low-loss silicon microelectrical mechanical system (MEMS) phase shifter operating in the 500-600 GHz band. The phase shifter consists of a \text{30-}\mu \text{m} thick perforated silicon slab that is moved in and out of a waveguide in the E-plane with a large deflection MEMS actuator. By implementing different hexagonal patterns in the silicon slab, a stepped permittivity is created to impedance match, and thus, reduce return loss. When the silicon slab is inserted into the waveguide, the phase velocity of the incoming wave is decreased, thus resulting in different phase shifts depending on the position of the slab inside the waveguide. The MEMS phase shifter is fully actuated at around 50\,{\text{V}} and can move up to \pm 95\,\mu \text{m}, depending on the applied voltage. The insertion loss, when the maximum phase shift is achieved, is measured to be \text{1.8}\,\text{dB}, compared to a 1.6\text{-}\text{dB} insertion loss for a waveguide of equivalent length. The return loss is better than \text{18}\,\text{dB} for the desired band. The measured phase shift, with the slab fully inserted into the waveguide at \text{550}\,\text{GHz} was 145^\circ. The MEMS phase shifter enables a variety of applications including phased array antenna systems with scanning capability for mapping of planetary surfaces with an electronically steerable antenna.

@en

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

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

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

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

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

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.

@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-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.

@en

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).

@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