Group for Advanced Receiver Development

Radio & Space Science Department
Chalmers University of Technology
Gothenburg, Sweden



Welcome to GARD OSO Web-pages on APEX Project

About the APEX Project

APEX, the Atacama Pathfinder Experiment, is collaboration between Max Planck Institut für Radioastronomie (MPIfR) at 50%, Onsala Space Observatory (OSO) at 23%, and the European Southern Observatory (ESO) at 27% to construct and operate a modified ALMA prototype antenna as a single dish on the high altitude site of Llano Chajnantor. The telescope was supplied by VERTEX Antennentechnik in Duisburg, Germany.

Observing with APEX will allow us to study warm and cold dust in starforming regions both in our own Milky Way and in distant galaxies in the young universe. High frequency spectral lines enable the exploration of the structure and chemistry of planetary atmospheres, dying stars, molecular clouds as well as inner regions of starburst galaxies. We will address issues from the vast scales of the structure of the Universe down to the physics and chemistry of comets.

APEX Telescope

Visit official web-page for the Atacama Pathfinder Experiment Telescope:


 Llano de Chajnantor
 50 Km east of San Pedro de Atacama,
 Northem Chile


Latitude : 23º00'20.8" South

Longitude :67º45'33.0" West

Altitude : 5105 m


12 m


125 000 kg

Main reflector

264 aluminum panels average panel surface r.m.s. 5 micron



Surface accuracy (r.m.s.)

17 micron

Pointing accuracy (r.m.s.)

2" rms over sky


Vertex Antennentechnik



Beam width (FWHM)

7.8" * (800 / f [GHz])

Receiver cabins

2 Nasmyth (A,B) + 1 Cassegrain (C)

Swedish Heterodyne Facility Instrument (SHeFI)

The Swedish single-pixel heterodyne facility receiver (SHeFI) is part of OSO contribution to Atacama Pathfinder Experiment, APEX, and is placed in the telescope Nasmyth cabin A (left, from behind view). The receiver replaces the receiver APEX 2A and is built based on integrated design concept where no plugged modules or cartridges are used.  Instead, the receiver provides tight integration of all components, which saves space and reduces the mass.  For example, 6-channel SHeFI occupies about 20% of ALMA 10 ‑ channel receiver volume and is about 20% in mass of ALMA FE.  Integrated design allows to share many components, e.g., the second stage IF amplifier is common for Band 1, Band 2 and Band 3, those bands using SIS junction based mixers, while Band T2 with HEB mixer has separate IF chain due to the difference in the SIS and HEB mixer IF bands.  All receiver channels are connected to the antenna via optical switch, a mirror in the centre of the SHeFI top cover rotated by step motor.  The channel switch mechanically coupled to the shatter inside the SHeFI dewar that opens corresponding pare of windows, one for the input signal and another for LO, for the selected channel/band.  All LO are mounted on the top panel of the SHeFI support bracket and quasi-optically coupled to the corresponding mixer.  Detailed technical description of the design and optics could be found following the link below.

The receivers placed in the Nasmyth cabin A are coupled to the antenna via relay optics providing possibility to operate either SHeFI  or one of the two different PI-type instruments. The relay optics to Cabin A covers 211 – 1500 GHz frequency band.  Out of 6 positions in the SHeFI receiver, GARD OSO is responsible to populate four: APEX Band 1, Band 2, Band 3 and Band T2.  The table below summarises the specification for SHeFI.





Tnoise 80%/any freq.


211 ‑ 275 GHz

SSB (2SB), wg, SIS

4 – 8 GHz

77 K / 126 K


275 – 370 GHz

SSB (2SB), wg, SIS

4 – 8 GHz

133 K / 198 K


385 – 500 GHz

SSB (2SB), wg, SIS

4 – 8 GHz

181 K / 270 K


1.250 – 1.390 THz

DSB Balanced, wg, HEB

2 – 4 GHz

Goal 1200 K

All LO sources have been purchased from VDI Inc., and use direct multiplication scheme.  Originally delivered hardware has been re-engineered by GARD to comply with environmental requirements and optical and mechanical interfaces.

SHeFI technical description

The receiver technical and design details can be found here.  Please note that all performance data is as preliminary measured prior to the pre-shipment review (Dec. 2007).  Actual performance at the site is described in the SHeFI scientific commissioning report (see below). Additional details could be found in the selected references below.  Almost for all the receivers the tuning was done to improve stability and sideband rejection at the expense of slight compromising on the noise temperature.

The control system hardware details can be found here.  The control system software details can be found here.

Installation and Commissioning:

GARD provided complete installation of the SHeFI during spring campaign 2008. You can see the installation on slide-show: big size file (800x600) and small size file (640x480).  Short movie of the APEX in move.  Scientific commissioning of the SHeFI was done later during 2008.  APEX Band T2 commissioning is still not completed (March 2009) due to strict requirements on weather; APEX T2 commissioning uses exclusively ESO and Sweden observation time.

Science commissioning report should be published at a later time, when it will be made available for outside APEX Project.  Please note that, for SHeFI receiver noise temperature calibration, a facility cold load is used.  The facility cold load is designed and provided by MPIfR to cover all frequency range for current and future instruments installed in the Nasmyth Cabin A.  As such, it uses a design of frequency independent dewar window with a Teflon plate at the Brewster angle as the window sealing.  We have no data how this quite thick window affects the effective temperature of the cold load over the frequency band of SHeFI but envisage a possibility for the RF loss in the Teflon increasing with frequency, especially towards THz frequencies.  This should lead to higher measured noise temperatures than actual.

SHeFI References (selected with most recent results on receiver channel performance)




1.  Vassilev, Vessen, Henke, Doug, Lapkin, Igor, Nyström, Olle, Monje, Raquel, Pavolotsky, Alexey, Belitsky, Victor, "Design and Characterization of a 211-275 GHz Sideband Separating Mixer for the APEX Telescope", IEEE Microwave and Wireless Components Letters, pp.55-60, Vol. 18, Number 1, January 2008.
2.  V. Vassilev, D. Meledin, I. Lapkin, V. Belitsky, O. Nyström, D. Henke, A. Pavolotsky, R. Monje, C. Risacher, M. Olberg, M. Strandberg, E. Sundin, M. Fredrixon, S.-E. Ferm, V. Desmaris, D. Dochev, M. Pantaleev, P. Bergman, and H. Olofsson, ”Swedish heterodyne facility instrument for the APEX telescope”, Astronomy and Astrophysics, A&A 490, pp. 1157‑1163, 2008.


3.  C. Risacher, R. Monje, V. Vassilev, A. Pavolotsky, V. Belitsky, ” A sideband separation SIS mixer for 275-370 GHz for the APEX telescope”,  Proceedings of SPIE Conference on Astronomical Telescopes and Instrumentation, 24 - 31 May 2006, Orlando,  Florida  USA. C. Risacher, V. Belitsky, V. Vassilev, I. Lapkin, A. Pavolotsky, ”A 275-370 GHz SIS receiver with Novel Probe Structure”, Int. Journal Infrared and Millimeter Waves, v. 26, No. 6, pp. 867 – 880, 2005.
4.  C. Risacher, V. Vassilev, R. Monje, I. Lapkin, V. Belitsky, A. Pavolotsky, M. Pantaleev, P. Bergman, S.-E. Ferm, E. Sundin, M. Svensson, M. Fredrixon, D. Meledin, L.-G. Gunnarsson, M. Hagström, L.-Å. Johansson, M. Olberg, R. Booth, H. Olofsson and L.-Å. Nyman, “A 0.8 mm heterodyne facility receiver for the APEX telescope”, Astronomy and Astrophysics, 454 No. 2, p. L17 (2006).
5.  R. Monje, V. Belitsky, V. Vassilev, “A Novel Design of Broadband Waveguide Directional Couplers and 3-dB Hybrids”, Microwave Symposium Digest, IEEE IMTT-S, San Francisco, California USA, 11-16 June 2006.
6.  C. Risacher, R. Monje, V. Vassilev, A. Pavolotsky, V. Belitsky, ” A sideband separation SIS mixer for 275-370 GHz for the APEX telescope”,  Proceedings of SPIE Conference on Astronomical Telescopes and Instrumentation, 24 - 31 May 2006, Orlando,  Florida  USA.


7.  R. Monje, V. Belitsky, V. Vassilev, A. Pavolotsky, ”SIS Mixer for 385-500 GHz with On-Chip LO injection”, Proceedings of the 18th International Symposium on Space Terahertz Technology, pp. 44-49, Pasadena, USA, March 21 ‑ 23, 2007.
8.  R. Monje, V. Belitsky, V. Vassilev, A. Pavolotsky, I. Lapkin, V. Desmaris, D. Meledin, D. Henke, D. Dochev, “A 0.5 THz Sideband Separation SIS Mixer for APEX Telescope”, to be published in the Proceedings of the 19th International Symposium on Space Terahertz Technology, Groningen, April 28-30, 2008.


9.  A. Pavolotsky, D. Meledin, C. Risacher, M. Pantaleev, V. Belitsky, “Micromachining  approach in fabricating of THz waveguide components“, Microelectronics Journal, v. 36, pp.636-686, 2005
10.  V. Desmaris, D. Meledin, A. Pavolotsky, R. Monje, and V. Belitsky, “All-metal micromachining for the fabrication of sub-millimetre and THz waveguide components and circuits,” J. Micromech. Microeng., vol. 18, 2008, Art. ID 095004 (6 pp).
11.  Denis Meledin, Alexey Pavolotsky, Vincent Desmaris, Igor Lapkin, Christophe Risacher, Victor,
Perez, Douglas Henke, Olle Nystrom, Erik Sundin, Dimitar Dochev, Miroslav Pantaleev, Magnus Strandberg, Boris Voronov, Gregory Goltsman, and Victor Belitsky, “A 1.3 THz Balanced Waveguide HEB Mixer for the APEX Telescope”, IEEE Trans.on Microwave Theory and Technique, MTT, pp. 89 – 97, vol. 57, n. 1, 2009.


12.  O. Nyström, M. Pantaleev, V. Vassilev, I. Lapkin, V. Belitsky, "A Vector Beam Measurement System for 211-275 GHz", Proc. EuCAP 2006, ISBN/ISSN: 92-9092, 6-10 November 2006, Nice, FRANCE.

13.  Victor Belitsky, Igor Lapkin, Vessen Vassilev, Raquel Monje, Alexey Pavolotsky, Denis Meledin, Douglas Henke, Olle Nyström, Vincent Desmaris, Christophe Risacher, Magnus Svensson, Michael Olberg, Erik Sundin, Mathias Fredrixon, Dimitar Dochev, Sven-Erik Ferm and Hans Olofsson, “Facility Heterodyne Receiver for the Atacama Pathfinder Experiment Telescope”, Proceedings of joint 32nd International Conference on Infrared Millimeter Waves and 15th International Conference on Terahertz Electronics, September 3 - 7, 2007, City Hall, Cardiff, Wales, UK, pp. 326 – 328.
14.  Olle Nyström, Igor Lapkin, Vincent Desmaris, Dimitar Dochev, Sven-Erik Ferm, Mathias Fredrixon, Douglas Henke, Denis Meledin, Raquel Monje, Magnus Strandberg, Erik Sundin, Vessen Vassilev, and V. Belitsky, ”Optics Design and Verification for the APEX Swedish Heterodyne Facility Instrument (SHeFI)”, To be submitted to Int. Journal Infrared and Millimeter Waves, March 2009.



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