Theodore Reck

MKID development for SuperSpec: an on-chip, mm-wave, filter-bank spectrometer

SuperSpec is an ultra-compact spectrometer-on-a-chip for millimeter and submillimeter wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed readout will enable construction of powerful multibeam spectrometers for high-redshift observations. The spectrometer consists of a horn-coupled microstrip feedline, a bank of narrow-band superconducting resonator filters that provide spectral selectivity, and kinetic inductance detectors (KIDs) that detect the power admitted by each filter resonator. The design is realized using thin-film lithographic structures on a silicon wafer. The mm-wave microstrip feedline and spectral filters of the first prototype are designed to operate in the band from 195-310 GHz and are fabricated from niobium with at Tc of 9.2K. The KIDs are designed to operate at hundreds of MHz and are fabricated from titanium nitride with a Tc of ~ 2 K. Radiation incident on the horn travels along the mm-wave microstrip, passes through the frequency-selective filter, and is finally absorbed by the corresponding KID where it causes a measurable shift in the resonant frequency. In this proceedings, we present the design of the KIDs employed in SuperSpec and the results of initial laboratory testing of a prototype device. We will also brie describe the ongoing development of a demonstration instrument that will consist of two 500-channel, R=700 spectrometers, one operating in the 1-mm atmospheric window and the other covering the 650 and 850 micron bands.

Array technology for terahertz imaging

Heterodyne terahertz (0.3 - 3THz) imaging systems are currently limited to single or a low number of pixels. Drastic improvements in imaging sensitivity and speed can be achieved by replacing single pixel systems with an array of detectors. This paper presents an array topology that is being developed at the Jet Propulsion Laboratory based on the micromachining of silicon. This technique fabricates the arrays package and waveguide components by plasma etching of silicon, resulting in devices with precision surpassing that of current metal machining techniques. Using silicon increases the versatility of the packaging, enabling a variety of orientations of circuitry within the device which increases circuit density and design options. The design of a two-pixel transceiver utilizing a stacked architecture is presented that achieves a pixel spacing of 10mm. By only allowing coupling from the top and bottom of the package the design can readily be arrayed in two dimensions with a spacing of 10mm x 18mm.

Transceiver array development for submillimeter-wave imaging radars

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.

500–750 GHz submillimeter-wave MEMS waveguide switch

This paper presents a 500-750 GHz waveguide based single-pole single-throw (SPST) switch achieving a 40% bandwidth. It is the first ever RF MEMS switch reported to be operating above 220 GHz. The switch is based on a MEMS-reconfigurable surface which can block the wave propagation in the waveguide by short-circuiting the electrical field lines of the TE10 mode. The switch is designed for optimized isolation in the blocking state and for optimized insertion loss in the non-blocking state. The measurement results of the first prototypes show better than 15 dB isolation in the blocking state and better than 3 dB insertion loss in the non-blocking state for 500-750 GHz. The higher insertion loss is mainly attributed to the insufficient metal thickness and surface roughness on the waveguide sidewalls. Two switch designs with different number of blocking elements are fabricated and compared. The overall switch bandwidth is limited by the waveguide only and not by the switch technology itself.

500–600 GHz submillimeter-wave 3.3 bit RF MEMS phase shifter integrated in micromachined waveguide

This paper presents a 500-600 GHz submillimeter-wave MEMS-reconfigurable phase shifter. It is the first ever RF MEMS component reported to be operating above 220 GHz. The phase shifter is based on a micromachined rectangular waveguide which is loaded by 9 E-plane stubs, which can be individually blocked by using MEMS-reconfigurable surfaces. The phase-shifter is composed of three metallized silicon chips which are assembled in H-plane cuts of the waveguide. The measurement results of the first prototypes of the MEMS reconfigurable phase shifter show a linear phase shift of 20° in 10 steps (3.3 bit) and have a return loss better than 15 dB from 500-600 GHz. The insertion loss is better than 3 dB up to 540 GHz, and better than 5 dB up to 600 GHz for all phase states, of which the major part is contributed by the assembly of the microchips between waveguide flanges which has a reproducibility error between 2 and 6 dB measured for reference chips.

A 700-GHz MEMS Waveguide Switch

A low-loss microelectromechanical systems (MEMS) waveguide reflect switch is demonstrated operating across the WM-380 (WR-1.5) waveguide band. The design uses a large deflection MEMS actuator to mechanically obstruct a reduced height waveguide to create the switch. The MEMS device exhibits 3 dB of insertion loss across the band in the open state, over 20 dB of isolation when closed, and better than 20 dB of return loss. Lifetime testing of this device demonstrates 5.07 million cycles before it failed in the closed state.

500-600 GHz RF MEMS based tunable stub integrated in micromachined rectangular waveguide

This paper presents a 500-600 GHz switchable Eplane waveguide stub tuned MEMS device. It is the first ever RF MEMS component reported to be operating above 220 GHz. The micromachined E-plane stub can be blocked/unblocked from the micromachined waveguide by using a MEMS-reconfigurable surface. The surface is designed so that in the blocking state it is in the H-plane and comprises the roof of the main waveguide, whereas in the non-blocking state it comprises a transmissive Eplane surface for the stub. The measurement results of the first prototypes show a return loss better than 15 dB from 500-600 GHz. The insertion loss is better than 3 dB up to 550 GHz, and better than 4 dB up to 600 GHz. The switchable stub can be utilized as a basic reconfigurable device for tuning/matching of waveguide components under operation; the implemented prototype switchable stub achieves a (measured) tuning of 2.5° at 500 GHz, with a change in S21 better than 0.15 dB for the whole band. The paper further shows that the reconfigurable stub can also be operated in analog tuning mode. This paper also demonstrates that MEMS-reconfigurable E-plane surfaces can be designed and operated deep into the submillimeter-wave frequency range.

2.1 An integrated 0.56THz frequency synthesizer with 21GHz locking range and −74dBc/Hz phase noise at 1MHz offset in 65nm CMOS

Spectra from 0.5 to 0.6THz play critical roles in planetary science, astrophysics and radio-astronomy as various chemical species including water, nitrates (NO2, N2O, NH3) and organics (CH4 and HCN) can either absorb or reflect radiation in this frequency regime. Accordingly, NASA and ESA have developed a wide range of spectroscopic sounding instruments to investigate our solar system. Current LO chains for spectroscopic receivers are implemented with discrete III-V devices and heavy waveguide assemblies. For instance, the 600GHz NASA PISSARRO spectrometer for Europa begins with a 33GHz PLL, tripled to 100GHz, doubled to 200GHz, and then tripled again to 600GHz via multiple waveguides. This LO chain occupies over 3000cm3, weighs 2.5kg, and consumes 11.5W of DC power.

Terahertz antenna for arrays of hundreds of pixels

Array technology is currently being applied to terahertz (THz) remote sensing systems to improve sensitivity and scanning speed. An integral component to these arrayed systems is the antenna feed structures since they must satisfy challenging manufacturing requirements to support the high densities and high pixel counts required. This paper reviews the current technologies used for THz antennae and discusses their impediments to arraying. Several new antenna designs are efficiently arrayed are discussed.