Cecile Jung-Kubiak

Measurement of Silicon Micromachined Waveguide Components at 500–750 GHz

This paper presents techniques used to assemble and measure micromachined submillimeter-wave waveguide circuits operating from 500 to 750 GHz. A novel micromechanical compression pin is developed to improve wafer-to-wafer alignment to less than 1 μm. Connection between the silicon waveguide and the VNA is aligned through a silicon boss that inserts into the custom waveguide flange. Waveguide loss is characterized for both E- and H-plane split waveguides and is found to be similar to standard metal waveguides. Finally, measurement of a 3 dB hybrid coupler operating from 500 to 600 GHz is presented.

Silicon Micromachined Lens Antenna for THz Integrated Heterodyne Arrays

In this paper, we present the design, fabrication, and measurements of a lens THz antenna that can be fabricated using conventional photolithography and deep reactive etching processes. The antenna is composed of an extended hemispherical silicon lens and a leaky wave waveguide feed. Both elements are fabricated using silicon micromachining techniques, enabling the fabrication of future large antenna arrays with a parallel process. To show the concept, a first antenna prototype has been fabricated using this fabrication process. Measurements obtained at 550 GHz are presented.

Silicon Micromachined Canonical

In this letter, several bandpass filters operating in the WR-1.5 band (500 to 750 GHz) are presented. The deep reactive ion etching (DRIE) silicon micromachining process is used for the fabrication of the filters. Two canonical filter topologies based on E- and H-plane are implemented. The work presented here has two specific objectives: a) to get important fabrication process parameters, such as tolerances, vertical angles, surface roughness, and repeatability and b) to validate the proper working of the waveguide filters in the terahertz band. These filters do not have any tuning element. Experimental results show better than 10 dB return loss and approximately 1 and 2.5 dB insertion loss (for 6% fractional bandwidth) for the E- and H-plane topology, respectively. The obtained results are in agreement with fabrication tolerances of 2 μm and vertical angles deviations up to 3°.

{\hbox{E}}

A multiflare angle horn is optimized with an in-house software using Body of Revolution finite-difference time-domain solver (BoR-FDTD) combined with a genetic algorithm (GA). This antenna is optimized to demonstrate low cross polarization, low side-lobe level, good return loss, and excellent beam circularity over the 1700-2100-GHz frequency range. A prototype with a directivity of 31.7 dBi and a cross-polarization level below -22 dBi was measured at 1.9 THz with excellent agreement with calculation .

-Plane and

We report on the design, fabrication and characterization of a high-power and broadband 105-120 GHz Schottky diode frequency tripler based on a novel on-chip power combining concept that allows superior power handling than traditional approaches. The chip features twelve anodes on a 50 μm thick GaAs substrate. At room temperature, the tripler exhibits a 17% 3 dB bandwidth and a ~ 30% peak conversion efficiency for a nominal input power of around 350-400 mW, and ~ 20% efficiency for its maximum operational input power of 800-900 mW. This tripler can deliver maximum power levels very close to 200 mW. The on-chip power-combined frequency tripler is compared with a traditional tripler designed for the same band using the same design parameters.

{\hbox{H}}

An eight-pixel transceiver array for operation in a 340 GHz imaging radar is presented. Silicon micromachining is applied to fabricate the submillimeter-wave front-end components to increase the density and uniformity of the array while lowering the cost compared to metal machining. Performance comparable with discrete metal machined housings was achieved with the 340 GHz transmitter nominally producing 0.5 mW and the mixers having a DSB noise temperature of 2000 K with a conversion loss of 8 dB. Radar performance is primarily limited by the isolation of the hybrid coupler, which is typically 28 dB, but excellent imaging performance is still achieved and improvements in penetration compared to higher frequency imaging radars is demonstrated.

-Plane Bandpass Filters at the Terahertz Band

A silicon lens antenna suited for future integrated terahertz arrays has been proposed recently. The antenna consists of an extended hemispherical silicon lens fed by a leaky-wave waveguide feed. The primary advantage is that the antenna is compatible with silicon micro-fabrication techniques as only a small sector of the lens is actually used. Moreover, it can be easily integrated with other silicon micromachined front-end components. In this letter, the design and optimization details of such a micro-lens antenna is presented. The design is validated with a set of measurements at 550 GHz from a prototype that has been fabricated using laser micro-fabrication.

1.9-THz Multiflare Angle Horn Optimization for Space Instruments

We report on the development of a waveguide-based balanced superconducting mixer for operation near 2.7 THz. The mixer employs a pair of NbN hot-electron bolometers defined on 6 μm-thick silicon substrate that follows a 90 ° hybrid coupler. To produce the critical structures of the coupler and waveguide embedding circuit, we have utilized silicon micromachining techniques based on deep reactive ion etching. Operating near 4.2 K bath temperature, we have measured a minimum uncorrected DSB receiver noise temperature of less than 2000 K using Callen-Welton formula and local oscillator sideband noise rejection better than 13±3 dB at 2.74 THz. The concept is suitable for building arrays, readily scalable for higher frequencies up 5 THz, and could accommodate other mixer technologies, such as room-temperature Schottky diode mixers.

A High-Power 105–120 GHz Broadband On-Chip Power-Combined Frequency Tripler

Silicon micromachining technology is naturally suited for making THz components, where precision and accuracy are essentials. We report here the development of robust micromachining techniques to enable novel active and passive components in the submillimeter-wave region. These features will enable large format submillimeter-wave heterodyne arrays and 3-D integration in the THz region, where fabricating circuits and structures becomes difficult with conventional machining.

A Silicon Micromachined Eight-Pixel Transceiver Array for Submillimeter-Wave Radar

The Jet Propulsion Laboratory (JPL) is developing compact transceiver arrays housing discrete GaAs Schottky diodes with integrated waveguides in order to increase the frame rate and lower the cost of active submillimeter-wave imaging radar systems. As part of this effort, high performance diode frequency multiplier and mixer devices optimized for a 30 GHz bandwidth centered near 340 GHz have been fabricated using JPL’s MoMeD process. A two-element array unit cell was designed using a layered architecture with three-dimensional waveguide routing for maximum scalability to multiple array elements. Prototype two-element arrays have been built using both conventionally machined metal blocks as well as gold-plated micromachined silicon substrates. Preliminary performance characterization has been accomplished in terms of transmit power, and conversion loss, and promising 3D radar images of concealed weapons have been acquired using the array.