The Atacama Large Millimeter/submillimeter Array (ALMA) Band 1 receiver covers the frequency range of 35-50 GHz. An extension of up to 52 GHz is on a best-effort basis. 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 Band 1 receiver. The infrastructure, integration, and evaluation of the fully-assembled Band 1 receiver system will be covered. Finally, a discussion of the technical and managerial challenges encountered for this large number of receivers will be presented.
The Atacama Large Millimeter/submillimeter Array(ALMA) Band 1 receiver covers the 35-50 GHz frequency band. Development of prototype receivers, including the key components and subsystems has been completed and two sets of prototype receivers were fully tested. We will provide an overview of the ALMA Band 1 science goals, and its requirements and design for use on the ALMA. The receiver development status will also be discussed and the infrastructure, integration, evaluation of fully-assembled band 1 receiver system will be covered. Finally, a discussion of the technical and management challenges encountered will be presented.
The ALMA Band-1 receiver front-end prototype cold and warm cartridge assemblies, including the system and key
components for ALMA Band-1 receivers have been developed and two sets of prototype cartridge were fully tested. The
measured aperture efficiency for the cold receiver is above the 80% specification except for a few frequency points.
Based on the cryogenically cooled broadband low-noise amplifiers provided by NRAO, the receiver noise temperature
can be as low as 15 – 32K for pol-0 and 17 – 30K for pol-1. Other key testing items are also measured. The receiver
beam pattern is measured, the results is well fit to the simulation and design. The pointing error extracted from the
measured beam pattern indicates the error is 0.1 degree along azimuth and 0.15 degree along elevation, which is well fit
to the specification (smaller than 0.4 degree). The equivalent hot load temperature for 5% gain compression is 492 -
4583K, which well fit to the specification of 5% with 373K input thermal load. The image band suppression is higher
than 30 dB typically and the worst case is higher than 20 dB for 34GHz RF signal and 38GHz LO signal, which is all
higher than 7 dB required specification. The cross talk between orthogonal polarization is smaller than -85 dB based on
present prototype LO. The amplitude stability is below 2.0 x 10-7 , which is fit to the specification of 4.0 x 10-7 for
timescales in the range of 0.05 s ≤ T ≤ 100 s. The signal path phase stability measured is smaller than 5 fs, which is
smaller than 22 fs for Long term (delay drift) 20 s ≤ T < 300 sec. The IF output phase variation is smaller than 3.5° rms
typically, and the specification is less than 4.5° rms. The measured IF output power level is -28 to -30.5 dBm with 300K
input load. The measured IF output power flatness is less than 5.6 dB for 2GHz window, and 1.3dB for 31MHz window.
The first batch of prototype cartridges will be installed on site for further commissioning on July of 2017.
ALMA covering 35-950 GHz is the largest existing telescope array in the world. Among the 10 receiver bands, Band-1,
which covers 35-50 GHz, is the lowest. Due to its small dimension and its time-variant frequency-dependent gain
characteristics, current solar filter located above the cryostat cannot be applied to Band-1 for solar observation. Here we
thus adopt new strategies to fulfill the goals. Thanks to the flexible dc biasing scheme of the HEMT-based amplifier in
Band-1 front-end, bias adjustment of the cryogenic low noise amplifier is investigated to accomplish solar observation
without using solar filter. Large power handling range can be achieved by the de-tuning bias technique with little
degradation in system performance.
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