Astronomical surveys are demanding more throughput from telescope receivers. Currently, microwave/millimeter telescopes with mature cryogenic single pixel receivers are upgrading to multi-pixel receivers by replacing the conventional feed horns with phased array feeds (PAFs) to increase the field of view and, thus, imaging speeds. This step in astronomy instrumentation has been taken by only a few research laboratories world-wide and primarily in Lband (0.7-1.5 GHz). We present a K-band (18-26 GHz) 5x5 modular PAF to demonstrate the feasibility of higher frequency receiving arrays. The KPAF system includes a tapered slot antenna array, a cryogenic commercial GaAs MMIC amplifier block, and a mixing stage to down-convert to L band for an existing beamformer. The noise temperature and power budget are outlined. Full antenna S-parameters and far-field beam patterns are simulated and measured using both planar near-field and far-field techniques. Cryogenic and room temperature amplifier noise measurements with varying bias levels are presented.
The prototype cartridges for ALMA Band-1 receivers have been developed, based on the key components developed in ALMA Band-1 consortium laboratories. The prototype cartridges for each receiver consist of two parts, cold cartridge assembly and warm cartridge assembly. The cold cartridge assembly (CCA) consists of horn antenna, orthomode transducer and a pair of 35-52 GHz cold low-noise amplifiers, the amplified signals of both polarizations are transmitted to warm cartridge assembly by long waveguide sections. In warm cartridge assembly (WCA), two major modules incorporated, down-converter assembly including warm low-noise amplifier, high-pass filter, mixer and 4-12 GHz IF amplifier, and local oscillator based on a 31-40 GHz YIG-tunes oscillator. The frequency range is based on the upper sideband scheme. Based on the measured performance of the key components, the expected noise performance of the receiver will be 26-33K.
This work presents a complete study of the optical system for ALMA band 1, which covers the frequency range from 35 to 50 GHz, with the goal of extending the coverage up to 52GHz. Several options have been explored to comply with the stringent technical specifications, restrictions, and cost constraints. The best solution consists of a corrugated zoned lens, two infrared filters and a spline profiled corrugated horn. The calculated aperture efficiency is better than 75%, while the average noise contribution is lower than 10.3 K. The first prototypes of the system have been constructed and first evaluation results available.
ALMA Band 1, covering 31-45 GHz, is the lowest signal frequency band of the ALMA telescope and development of
the technology to be used for the front-end cartridge is currently in a research phase. We have made progress on various
key components designed for use in the ALMA Band 1 cartridge, including the orthomode transducer (OMT), low-noise
amplifier (LNA), lens, and down-converting mixer. Since the layout of the ALMA cartridges within the antenna is not
optimized for the lowest band, a dielectric lens is required to avoid blocking other bands. Using a lens necessitates
careful characterization of the dielectric properties controlling focal length and dielectric loss. It is also important to
match the index of refraction of the lens to minimize reflection while still providing equal performance for both linear
polarizations and not introducing any cross-polarization effects. Different anti-reflection techniques will be shown; for
example, a hole array, as an anti-reflection layer, has been used for a vacuum window and measured results are
compared with simulation. A test cryostat has been constructed by adding an extension to a commercial liquid helium
cryostat. Initial sensitivity measurements of a simplified prototype receiver will be given, incorporating an HDPE
window, commercial conical feedhorn, 3-stage LNA, and warm amplification stage. An overview of the system losses,
receiver noise budget, and system alignment tolerances will also be shown. Furthermore, there is interest in either
extending or shifting the existing frequency towards 50 GHz, and the impact on each component will be considered.
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 NRC Herzberg Institute of Astrophysics (NRC-HIA) is currently responsible to contribute Band 3 (84-116 GHz)
receivers to the international ALMA project - a partnership involving North America, Europe and, now, Asia. Not only
are the technical requirements for these receivers far more stringent than those for any existing radio astronomy receivers
operating at these frequencies, but the delivery schedule for these receivers is equally challenging. Since the Asian
partnership joined the ALMA project in 2006, NRC-HIA has been asked to deliver an additional 11 cartridges, for a total
of 73 units. Some of these new cartridges will be used for the ALMA Compact Array (ACA) and others as spares.
Moreover, the project has also requested that these additional cartridges be delivered in the same time period as the
original 62 units. To meet this requirement, production must increase from the existing rate of one unit every four weeks
to one every two, taxing the existing production infrastructure at NRC-HIA. Additional test facilities and human
resources must be planned to sustain the required production rate over the next several years. Industrial involvement is
one of the important elements in our production plan. In order to supplement the existing human resources at NRC-HIA,
we are planning to outsource a number of low-risk and labor-intensive tasks to industry. However, NRC-HIA will retain
overall project management responsibility and will conduct all the cartridge integration and acceptance test activities in-house.
This paper focuses on the resource estimation, planning and project management required to deliver the Band 3
receivers to the ALMA project on time and on budget.
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.
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).
Receiver B3 is a common-user facility instrument for the JCMT and was commissioned in December 1996. It includes the following features: (1) Frequency coverage of 315 to 372 GHz with optimum performance at 345 GHz. (2) Two spatially- coincident channels with orthogonal linear polarizations. (3) An IF of 4 GHz with an instantaneous bandwidth of 1.7 GHz in each channel. (4) Single side-band capability with the rejected side-band terminated on a cold load. (5) High- efficiency, frequency-independent optics. (6) Independent adjustment of the local oscillator power to the two mixers. (7) Internal ambient and cold loads for accurate receiver calibration. (8) Fully automated operation.
A low Tc Pb alloy Superconductor-Insulator-Superconductor (SIS) tunnel junction heterodyne receiver has been constructed for astronomical use and tested over the frequency range of 400 to 540 GHz. Various alloy structures have been investigated in order to allow the production of small area SIS junctions with stable electrical characteristics and resistance to stress on cooling from 300 K to 4.2 K. Improvements in photolithography and thin film deposition techniques have been made that allow the fabrication of reliable sub-micron area junctions using suspended photoresist stencil and E-beam evaporation techniques. A single sub-micron area junction is mounted in a reduced height two tuner waveguide structure, which provides an optimum impedance match between the junction and the received signal. Performance measurements made with the receiver installed on the James Clerk Maxwell Telescope, Hawaii, show a total system double sideband noise equivalent temperature of 160 K at 460 GHz and 220 K at 490 GHz, measured in a 1 GHz instantaneous IF bandwidth centered at 4 GHz. The receiver demonstrates that Pb alloy tunnel junctions provide excellent sensitivity at submillimetre wavelengths and are sufficiently stable and reliable to allow use at a remote observing site.