• Journal of Astronomy and Space Sciences
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• 제23권1호
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• pp.19-28
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• 2006

The noise temperature of existing millimeter-wave receivers is already within two or three times quantum noise limit. One of practical ways to increase the observation speed of single dish radio telescope without longer integration time is use of multi-beam focal plane array receiver as demonstrated in several large single dish radio telescopes. In this context the TRAO (Taeduk Radio Astronomy Observatory), which operates a 143n Cassegrain radio telescope, is planning to develop a 4 x 4 beams focal plane array SIS receiver system for 86-115 GHz band. Even though millimeter-wave HEMT LNA-based receivers approach the noise temperature comparable to the SIS receiver at W-band, it is believed that the receiver based on SIS mixer seems to offer a bit more advantages. The critical part of the multi-beam array receiver will be sideband separating SIS mixers. Employing such a type of SIS mixer makes it possible to simplify the quasi-optics of receiver. Otherwise, an SSB filter should be used in front of the mixer or some sophisticated post-processing of observation data is needed. In this paper we will present a preliminary design concept and components needed for the development of a new 3 mm band multi-beam focal plane array receiver.

• 전자공학회논문지A
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• 제33A권6호
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• pp.90-98
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• 1996

We have evaluated the theoretical conversion loss and noise temperature of mixer using the quantum mixer theory and the method to determine the embedding impedance of waveguide-type mixer mount. At fixed backshort position of the mixer, the calculated SSB mixer conversion loss and mixer noise temperature are 5 dB and 10K within frequency range form 85 GHz to 115 GHz, respectively. The SIS mixer has been developed by using through on the calculated rsutls to observe cosmic radio waves. SIS junction of mixer is Nb/Al-AlOx/Nb and it consists of four series array. Area of each of junction is about 2.5${\mu}m^{2}$. The average receiver noise temperature of manufactured receiver with this mixer is about 30 K(DSB). The receiver noise temperature is much lower than that of receiver with a mixer using mechanical tuning backshort.

• 한국전자파학회논문지
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• 제15권8호
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• pp.737-743
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• 2004

120∼180 GHz 대역의 고정 튜닝방식을 사용한 SIS(Superconductor-Insulator-Superconductor) 접합 믹서를 개발 하였다. 이 믹서는 노베야마 전파천문대에서 제작된 6개 직렬 연결 Nb/Al-A1$_2$O$_3$/Nb SIS 접합 소자를 사용하였으며 석영유리 기판에 제작된 이 SIS 칩은 전 주파수 대역에서 입력신호 결합을 향상시키기 위해 half-height 도파관의 중심에 놓여 있다. 본 논문에서 개발된 SIS 믹서는 기계적인 튜닝 장치를 사용하지 않으며 RF 신호와 LO 전력은 냉각된 십자형 방향성 결합기를 통해서 믹서에 공급된다. 또한 IF 신호 손실을 줄이기 위해 SIS 믹서의 IF 출력 임피던스를 IF 증폭단의 50 $\Omega$ 입력 임피던스에 정합 시켰다. SIS 수신기의 측정된 DSB 잡음온도는 120∼180 GHz 대역에서 32∼131 K이며 본 논문에서 개발된 SIS 믹서는 대덕전파천문대의 14 m 전파망원경에 설치되어 전파천문 관측에 사용되고 있다.

• 천문학회지
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• 제29권spc1호
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• pp.413-414
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• 1996

A 230 GHz SIS tunnel junction receiver has been being developed for radio astronomy in Nagoya University. In this heterodyne receiver, we use a $\~$1/3 reduced hight rectangular waveguide SIS mixer with two tuning elements as front end. The mixer block with SIS junction was cooled to 4K with a closed cycle He-gas refrigerator. So far, a double sideband receiver noise temperature lower than l00K in 222-237 GHz is obtained. The receiver exhibits a best DSB noise temperature of 69K at 236 GHz as well as 228 GHz.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2004년도 High Temperature Superconductivity Vol.XIV
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• pp.9-9
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• 2004

• 전자공학회논문지A
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• 제30A권10호
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• pp.12-19
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• 1993

Because of their high sensitivity and moderate bandwidth, superconducting receivers with SIS (Superconductor Insulator Superconductor) tunnel junction mixer are now widely used for millimeter wave radio astronomy. In this paper we have introduced how to determine the parameters of SIS tunnel junction which have to be optimized to achieve a good mixer performance. From these results of optimized junction parameters determined by this methods, SIS junctions which consist of a series array of four Nb/Al-AlOx/Nb junctions with each area 3.4${\mu}m^{2}$ have been fabricated by SNEP (Selective Niobium Etching Process) and RIE (Reactive Ion Eching). Also we have tested their DC current-voltage characteristics. These SIS junctions will be used as a mixer for 100GHz band cosmic waves receiver.

• 천문학논총
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• 제27권3호
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• pp.71-80
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• 2012

We have developed superconducting mixer receivers for 129 GHz VLBI observation in Korean VLBI Network (KVN). The developed mixer has a radial waveguide probe with simple transmission line L-C transformer as a tuning circuit to its 5 series-connected junctions, which can have 125 - 165 GHz as the operation radio frequency (RF). For intermediate frequency (IF) signal path a high impedance quarter-wavelength line connects the probe to one end of symmetric RF chokes. The double side band (DSB) receiver noise of the mixer was about 40 K over 4 - 6 GHz IF band, whereas we achieved the uncorrected single side band (SSB) noise temperature of about 70 K and better than 10 dB image rejection ratio in 2SB configuration with 8 - 10 GHz IF band. Insert-type receiver cartridges employing the mixers have been under commission for KVN stations.

• 천문학회지
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• 제36권1호
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• pp.43-48
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• 2003

We introduce and describe performance of the 6-meter telescope of Seoul Radio Astronomy Observatory (SRAO). All the softwares and instruments except the antenna structure and its driving system are developed for ourselves. The SIS mixer type receiver resulted in the receiver noise temperature less than 50 K (DSB) over the whole 3-mm radio window. An autocorrelation spectrometer, developed first in Korea, provides maximum 50 MHz band width over 1024 channels. Antenna surface is measured and adjusted using template method and radio holography which resulted in a superb surface accuracy bet-ter than 30${\mu}m$. Accordingly, the aperture and beam efficiences amount to $70\%$ and $75\%$, respectively, largely independent of frequency in the 85 - 115 GHz range. It is also found that telescope pointing errors are less than 10" in both azimuth and elevation and that antenna gain is almost constant against elevation greater than $20^{\circ}$, without adjusting sub-reflector position. The SRAO 6-meter telescope is now fully operational and all these characteristics verify that observations are carried out with high precision and fidelity.

• 천문학회지
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• 제47권6호
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• pp.319-325
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• 2014

We map two molecular clouds located in the exact anticenter region emitting in the (J = 1-0) transition of $^{12}CO$ and $^{13}CO$ using the 3-mm SIS mixer receiver on the 14-m radio telescope at Taeduk Radio Astronomy Observatory. The target clouds with anomalous velocities of $V_{LSR}{\sim}-20km\;s^{-1}$ are distinguished from other clouds in this direction. In addition, they are located in the interarm region between the Orion Arm and the Perseus Arm. Sizes of the clouds are estimated to be about 8.6 and 10.8 pc, respectively. The total mass is estimated to be about $4{\times}10^3$ $M_{\odot}$ using CO luminosity of the clouds. Several cores are detected, but no sign of star formation is found according to the IRAS point sources. Their larger linewidths, anomalous velocities, and their location at the interarm region make these clouds more distinguished, though their physical properties are similar to the dark clouds in the solar neighborhood in terms of mass and size.