Akihira Miyachi

The First Six ALMA Band 10 Receivers

The first six Atacama Large Millimeter/submillimeter Array (ALMA) Band 10 (787-950 GHz) receivers have been developed and characterized during the receiver preproduction phase. State-of-the-art measurement systems at THz frequencies have been implemented and successfully used to measure the performance of the first six receivers. Extensive tests ranging from receiver sensitivity and stability to optical aperture efficiency on the secondary antenna have been performed. Performance of all six receivers is well within the stringent ALMA requirements. Moreover, our extensive tests have shown that there are no big performance differences between receivers. These results indicate that the ALMA Band 10 receiver is ready for the production phase, during which an additional 67 receivers will be produced and characterized.

Performance of the ALMA Band 10 SIS Receiver Prototype Model

We have developed a dual polarization prototype model of the Atacama Large Millimeter/submillimeter Array (ALMA) Band 10 (787-950 GHz) receivers. The front-end optics comprises a pair of ellipsoidal mirrors, a wire grid, and two corrugated feed horns. A waveguide mixer block is attached to each feed horn in which a mixer chip employing Nb/AlOx/Nb juncions and NbTiN/SiO2/Al microstrip tuning circuits is mounted to a WR-1.2 full-height waveguide. A local oscillator (LO) signal receiving horn and a waveguide 10-dB LO coupler are integrated in the block to provide the LO signal to the mixer chip. A fixed-tuned multiplier with a diagonal horn located at the 110-K stage is used to transmit the LO power. The LO signal is then quasi-optically coupled to the mixer receiving horn. A very wide intermediate frequency (IF) system with a bandwidth of 4-12 GHz is employed. The receiver demonstrated double sideband (DSB) noise temperatures of about 160 K (4hν/kB) without any correction for loss in front of the receiver at the LO frequency of 834 GHz at an operating physical temperature of 4 K.

Optical Efficiencies of Lens-Antenna Coupled Kinetic Inductance Detectors at 220 GHz

We have been developing a terahertz camera based on antenna-coupled superconducting resonators, the so-called microwave kinetic inductance detectors (MKIDs), and a silicon lens array. The MKID consists of a coplanar waveguide coupled to a double slot antenna and is patterned on a high-quality aluminum film grown by molecular beam epitaxy. The camera is sensitive at frequencies of 200-240 GHz. Its bandwidth is limited by the impedance properties of the double slot antenna. The design, fabrication, and optical evaluations of the planar antennas and silicon lens arrays are presented in this paper. The MKID camera has been evaluated both in dark conditions and under optical radiation in a 0.1-K dilution refrigerator. The electrical noise equivalent power was around 5×10-18 W/√(Hz) in dark conditions and 4×10-16 W/√(Hz), which is much lower than the photon noise level, with the optical load. The optical efficiency of the camera was estimated by three independent methods, and the results were consistent with each other and equal to 20%-25% without an anti-reflection coating on the lens surface.

Tuning Circuit Material for Mass-Produced Terahertz SIS Receivers

A total of 73 dual polarization superconductor-insulator-superconductor (SIS) receivers for the Atacama Large Millimeter/submillimeter Array (ALMA) have been successfully produced to observe astronomical signals in the frequency band of 787-950 GHz. For the mass production of waveguide SIS mixer chips used in the receivers, we have tested two different compositions of Nb1-xTixN thin films for use in the mixers superconductor low-loss transmission lines. These components are being fabricated for mass-produced waveguide SIS mixer chips in receivers. One composition was prepared by employing a sputtering target with 20 wt.% Ti and 80 wt.% Nb (x = 0.2), and the other was prepared with a target composed of 30 wt.% Ti and 70 wt.% Nb (x = 0.3). Both films are deposited using dc magnetron sputtering on quartz substrates. We found that the ratio between the superconducting energy gap and the critical temperature (2Δ/kBTC) of the Nb0.8Ti0.2N films is larger than that of the Nb0.7Ti0.3N films. Since we obtained better sensitivities in the SIS mixers using the Nb0.8Ti0.2N films, they were used to produce all the receivers. These showed excellent performance complying with the stringent ALMA specifications.

ALMA band 10 (787-950 GHz): summary of the production of 73 receivers and first light results

This paper summarizes the performance of all the 73 ALMA band 10 cartridges in terms of noise performance and/or optical efficiencies compared to the required ALMA specifications. In particular, the measured optical performance is compared with the results of novel statistical Monte Carlo analyses carried out before receiver production. Some of the technical difficulties encountered during production are briefly described. Finally, some of the first light results of the first receivers used in Chile are presented.

C band GaN diode rectifier with 3W DC output for high power microwave power transmission applications

This research reports a 5.8-GHz band GaN (Gallium Nitride) diode rectifier for high power microwave power transmission (MPT) systems. Designed rectifier is fabricated and measured. The fabricated rectifier has Cu heat sink because of the high power operation. The GaN diode is directly mounted on the heat sink. Also, fabricated substrate is screwed to the heat sink. Measured RF-DC conversion efficiency and output DC power at 5.9GHz are 32.6% and 3042mW, respectively. This report makes a first step for future miniaturization by the hybrid semiconductor integrated circuit (HySIC) technology which utilizes different type semiconductor devices.

Design of dual-band rectifier using microstrip spurline notch filter

This paper proposes and demonstrates a novel dualband rectifier at 2.45 GHz and 5.8 GHz. The proposed rectifier employs a microstrip spurline notch filter to realize dual-band high RF-DC conversion efficiency. The control of reflected signals from the output filter to maximize the voltage swing at the diode, and use of the spurline notch filter provide high-level conversion efficiencies at both operating frequency bands. The fabricated proposed dual-band rectifier achieves the RF-DC conversion efficiencies of 55.9 % and 55.4 % at 2.15 GHz and 5.84 GHz, respectively. These results are top-level performances of the dualband rectifiers.

Uncertainty estimation for gallium nitride diode model based on VNA measurement at 5.8 GHz

This paper summarizes the uncertainty estimation for gallium nitride shottky diode based on vector network analyzer measurements at 5.8 GHz. The results were traceable to the metrology standard of S-parameter at NMIJ. Considering the uncertainty of the measurements, bias voltage must be applied over 2 V in measuring bias voltage dependence of reflection coefficient. The measurement uncertainty was propagated from reflection coefficient to impedance. As a result, the expanded uncertainty of real and imaginary part of impedance were 0.56 Ω and 0.57 Ω at 5.8 GHz, respectively.

Design of corrugated-horn-coupled MKID focal plane for CMB B-mode polarization

A focal plane based on MKID has been designed for cosmic microwave background (CMB) B-mode polarization experiments. We are designing and developing a focal plane with broadband corrugated horn array, planar OMT, 180 degree hybrid, bandpass filters, and MKIDs. The focal plane consists of 3 octave bands (55 - 108 GHz, 80 - 160 GHz, 160 - 320 GHz), 10 hexagonal modules. Broadband corrugated horn-array has been directly machined from an Al block and measured to have a good beam shape which is consistent with electromagnetic field simulations in octave bands. The horn array is designed to be low standing-wave, light weight, and electromagnetic shield. The broadband 4 probes ortho-mode transducer (OMT) is fabricated on Si membrane of an SOI wafer. A broadband 180 degree hybrid made with coplanar waveguide (CPW) is used to reduce higher modes of the circular waveguide. Two bandpass filters of each polarization are patterned with Nb microstrip. A prototype of the broadband corrugated horn coupled MKIDs has been fabricated and tested.

Wireless sensor network system with wireless powering by time division operation at 5.8 GHz in a reusable rocket

This paper demonstrates experimental evaluation results of a wireless sensor network system inside a reusable rocket for health monitoring system. The wireless sensor node is powered by microwave power transmission (MPT) to realize completely wireless, battery-less system. Both the MPT and wireless communication use same frequency, 5.8 GHz. Time division operation is utilized for the coexistence. Rectifier output DC power, received signal strength indicator (RSSI) and packet error rate (PER) is measured using the reusable vehicle test (RVT) to evaluate the feasibility of the coexistence.