Stephane Claude

Low-Cost and High-Efficient W-Band Substrate Integrated Waveguide Antenna Array Made of Printed Circuit Board Process

A novel class of low-cost, small-footprint and high-gain antenna arrays is presented for W-band applications. A 4 × 4 antenna array is proposed and demonstrated using substrate-integrated waveguide (SIW) technology for the design of its feed network and longitudinal slots in the SIW top metallic surface to drive the array antenna elements. Dielectric cubes of low-permittivity material are placed on top of each 1 × 4 antenna array to increase the gain of the circular patch antenna elements. This new design is compared to a second 4 × 4 antenna array which, instead of dielectric cubes, uses vertically stacked Yagi-like parasitic director elements to increase the gain. Measured impedance bandwidths of the two 4 × 4 antenna arrays are about 7.5 GHz (94.2-101.8 GHz) at 18 ± 1 dB gain level, with radiation patterns and gains of the two arrays remaining nearly constant over this bandwidth. While the fabrication effort of the new array involving dielectric cubes is significantly reduced, its measured radiation efficiency of 81 percent is slightly lower compared to 90 percent of the Yagi-like design.

ALMA front-end optics

The ALMA telescope will be an interferometer of 64 antennas, which will be situated in the Atacama desert in Chile. Each antenna will have receivers that cover the frequencies 30 GHz to 970 GHZ. This frequency range is divided into 10 frequency bands. All of these receiver bands are fitted on a cartridge and cooled, with bands 1 and 2 at 15K and the other 8 are SIS receivers at a temperature of 4K. Each band has a dual polarization receiver. The optics has been designed so that the maximum of the optics is cooled to minimize the noise temperature increase to the receivers. The design of the optics will be shown for each frequency bands. Test results with the method of testing on a near field amplitude and phase measurement system will be given for the first 4 frequency bands to be used, which are bands 3 (84-116 GHz), 6 (211-275GHz), 7 (275-375 GHz and 9 (600-702 GHz). These measurements will be compared with physical optics calculations.

Development of the ALMA Band-3 and Band-6 Sideband-Separating SIS Mixers

As the Atacama Large Millimeter/submillimeter Array (ALMA) nears completion, 73 dual-polarization receivers have been delivered for each of Bands 3 (84-116 GHz) and 6 (211-275 GHz). The receivers use sideband-separating superconducting Nb/Al-AlOx/Nb tunnel-junction (SIS) mixers, developed for ALMA to suppress atmospheric noise in the image band. The mixers were designed taking into account dynamic range, input return loss, and signal-to-image conversion (which can be significant in SIS mixers). Typical SSB receiver noise temperatures in Bands 3 and 6 are 30 and 60 K, respectively, and the image rejection is typically 15 dB.

Linear tapered slot antenna with substrate integrated waveguide feed

Tapered slot antennas (TSA) are lightweight, and low cost per element but retain directivity close to horn antennas. They are planar elements, so they can be integrated on the same substrate as an appropriate feed. The TSA design presented in this paper utilizes antipodal flares and the backwards extension match technique. However the design investigates techniques to increase element gain using high permittivity substrates and demonstrates the TSA capability at high frequency (18-24 GHz).

Minimizing RF Performance Spikes in a Cryogenic Orthomode Transducer (OMT)

The turnstile junction exhibits very low cross-polarization leakage and is suitable for low-noise millimeter-wave receivers. For use in a cryogenic receiver, it is best if the orthomode transducer (OMT) is implemented in waveguide, contains no additional assembly features, and may be directly machined. However, machined OMTs are prone to sharp signal drop-outs that are costly to overall performance since they show up directly as spikes in receiver noise. We explore the various factors contributing to this degradation and discuss how the current design mitigates each cause. Final performance is demonstrated at cryogenic temperatures.

Development of the ALMA-North America sideband-separating SIS mixers

As ALMA nears completion, 73 dual-polarization receivers have been delivered for each of Bands 3 (84-116 GHz) and 6 (211-275 GHz). The receivers use sideband-separating superconducting tunnel-junction (SIS) mixers, developed for ALMA to suppress atmospheric noise in the image band. The mixers were designed taking into account input return loss, dynamic range and signal-to-image conversion (which can degrade the image rejection). Results are given for typical production receivers.

A Compact High-Performance Orthomode Transducer for the Atacama Large Millimeter Array (ALMA) Band 1 (31–45 GHz)

This paper describes a compact high-performance orthomode transducer (OMT) with a circular waveguide input and two rectangular waveguide outputs based on the superimposition of three aluminum blocks. Several prototypes operating in the band 1 (31-45 GHz) of the atacama large millimeter array have been fabricated and measured. The design is based on the use of a turnstile junction that is machined in a single block, requiring neither alignment nor a high degree of mechanical tolerances. Thus, a high repeatability of the design is possible for mass production. Across the 31-45 GHz band, the isolation is better than 50 dB and the return losses at the input and outputs of the OMT are better than -25 dB.

Performance of the pre-production band 3 (84-116 GHz) receivers for ALMA

The Band 3 receiver, covering the 84-116 GHz frequency band is one of the 10 channels that will be installed on the Atacama Large Millimeter Array (ALMA). A total of 73 units have to be built in two phases: 8 preproduction and then 65 production units. This paper reports on the assembly, testing and performance of the preproduction series of these state-of-the-art millimeter receivers.

The Band 3 receiver (84-116 GHz) for ALMA

Test results are presented of the Band 3 module integrated into the Atacama large millimeter array (ALMA) front end receiver. The 84 to 116 GHz collected signal by the Band 3 receiver is split into two orthogonal polarisations using an orthomode transducer and then down-converted to 6 GHz over 4 GHz bandwidth using sideband separating mixers with better than 10 dB of image rejection. The single sideband systems low noise of 35 to 45 K is achieved by cascading superconductor-insulator-superconductor (SIS) mixers and low noise cryogenic amplifiers that consist of three stage high mobility transistors (HEMT) operating at 4 K.

Low-noise InP HEMT amplifier

This paper describes the development of a 3-stage cryogenic low noise InP HEMT amplifier for ALMA Band 3 receivers. A detailed design is given using Hughes 0.1 μm low noise InP HEMTs for producing a low power dissipation amplifier, < 9 mW. The amplifier design uses a hybrid circuit in order to provide the flexibility for optimizing the active devices and passive components. The optimal impedance matching for low noise and low input return loss were obtained by computer aided simulation to achieve 5 K noise temperature, 36 dB gain, flatness ±1 dB and -10 dB input return loss at 12 degrees Kelvin in the 4-9 GHz band. The amplifier will be used as a cold IF preamplifier with a SIS mixer in the Band 3 receivers now being constructed for the Atacama Large Millimetre Array (ALMA).