Program and Abstract Book - SRON

19 th International Symposium on Space Terahertz Technology
9-5
Development of ALMA Band 8 (385-500 GHz)
Cartridge and its Measurement System
Y. Sekimoto 1 , Y. Iizuka 1 , N. Satou 1 , T. Ito 1 , K. Kumgai 1 ,
M. Kamikura 1 , Y. Serizawa 1 , M. Naruse 1 , and W. L. Shan 2
1 National Astronomical Observatory of Japan
2 Purple Mountain Observatory
We have developed a cartridge-type receiver covering from 385 to 500 GHz for ALMA
band 8. It 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 which are
modular to choose balanced combination. An integrated prototype cartridge has low
noise temperature of < 8 hf/k in SSB and image rejection ratio of > 10 dB in the 80 % of
ALMA Band 8 frequency.
We have also developed equipments to test
both components and integrated receiver
including submillimeter vector network
analyzer, near field beam scanner. The
beam pattern of the cartridge are consistent
down to -40 dB with physical optical
calculation [3]. The cross polarization is less
than -20 dB. The amplitude stability is
around 3x10 -4 in 1 sec. The phase stability
is less than 2.0 degree in a time scale from
0.1 sec to 10 minutes. These results are
promising for receiver production of the
Atacama Large Millimeter/submillimeter
Array (ALMA).
[1] M. Kamikura et al. 2008 this conference
[2] M. Kamikura et al. 2006 IJIRMW
[3] M. Naruse et al. 2008 this conference Figure 4 ALMA Band 8 cartridge 4 K part
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