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We have developed a cartridge-type receiver covering the frequency band of 385-500 GHz as a qualification model of Atacama Large Millimeter/submillimeter Array (ALMA) band 8. It receives two orthogonal polarizations and down-converts the sideband-separated signals to intermediate frequencies (IF) of between 4 and 8 GHz. The cartridge-type receiver consists of cold optics, two feed horns, a wire grid, mirrors, two sideband-separating SIS mixers, cryogenic multipliers of a local oscillator (LO), cryogenic and warm IF amplifiers, a cartridge body, and sensors/wirings. These components were individually tested, and then the cartridge was integrated and tested as a complete assembly. We have also developed equipment for efficiency tests of both the components and the integrated receiver. The single sideband (SSB) noise temperature of this receiver is 100 K at the band center and 300 K at the band edges. The beam pattern and cross-polarization pattern are consistent with a physical optical calculation. The amplitude stability is around $3 \times 10^{-4}$ in 1 s. The phase stability is less than 2.0D on a time scale of 0.1 s to 10 min. These results are promising for a receiver in the ALMA.

We present design and evaluations of a submillimeter double-ridged waveguide ortho-mode transducer (OMT) for ALMA Band 8 (385-500 GHz) cartridge receiver. The measured transmission loss of the OMT at 4 K was 0.4-0.5 dB according to noise measurements with an SIS mixer. The polarization isolation was measured to be larger than 29 dB from quasioptical measurements. The OMT consists of a Bfifot junction and a double-ridged guide. A robust design with allowable mechanical errors of 20 μm has been demonstrated.