M1B Evaluation of ALMA Band 8 S/N01 Cartridge

ALMA Band 8 (385 - 500 GHz) is one of frequency bands which cover atmospheric windows on the Atacama desert in the northern Chile. We have developed a cartridge-type receiver which receives two orthogonal polarizations and down-converts the sideband separated signals to intermediate frequencies (IF) between 4 and 8 GHz. A waveguide polarization splitter or ortho-mode transducer (OMT) has been developed, which enables the cryogenic optics quite simple. It achieved low loss of ~0.4 dB at 4 K and polarization isolation of -25 dB in 385 - 500 GHz (1). A sideband separating mixer consists of two DSB Nb-based SIS mixers and waveguide quadrature coupler (2). The receiver noise temperature was less than 8 hf/k or 196 K in SSB and the image rejection ratio of > 10 dB in the 90 % of ALMA Band 8 frequency. Gain compression of this receiver was measured. The amplitude and phase stabilities were confirmed to comply the ALMA specifications. The co-polar and cross polar beam patterns of this receiver were measured in five frequencies (3). Test results of S/N 01 cartridge will be presented.