Band-1 receiver front-end cartridges for Atacama Large Millimeter/submillimeter Array (ALMA): design and development toward production

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.