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Sobis P.J.,Chalmers University of Technology | Wadefalk N.,Chalmers University of Technology | Emrich A.,Omnisys Instruments AB | Stake J.,Chalmers University of Technology
IEEE Microwave and Wireless Components Letters | Year: 2012

A 340 GHz subharmonic Schottky diode mixer and a multioctave (3-16 GHz) custom low noise amplifier (LNA) have been integrated to form a compact receiver front-end module, exhibiting ultra low noise with an exceptional flat response and broadband instantaneous frequency coverage. At room temperature, a receiver noise temperature of 870 K is measured at an LO drive of 1.2 mW at 170 GHz. The total dc power consumption of the LNA is below 120 mW. Measurements are in good agreement with simulations taking the mixer and LNA mismatch interaction into account. © 2012 IEEE. Source


Zhao H.,Chalmers University of Technology | Tang A.-Y.,Chalmers University of Technology | Sobis P.,Omnisys Instruments AB | Sobis P.,Chalmers University of Technology | And 6 more authors.
IEEE Microwave and Wireless Components Letters | Year: 2011

We demonstrate S-parameter characterization of membrane circuits in the WR-03 frequency band (220325 GHz) utilizing thru-reflect-line (TRL) -calibration technique. The TRL calibration kit design features 3 μm thick GaAs membrane circuits packaged in E-plane split waveguide blocks with the reference planes inside the membrane circuit structure. A 300 GHz membrane ring resonator filter circuit has been characterized by applying the proposed calibration kit, showing good agreement with simulations. © 2010 IEEE. Source


Karlsson R.,Albanova University Center | Sandqvist A.,Albanova University Center | Hjalmarson A.,Chalmers University of Technology | Winnberg A.,Chalmers University of Technology | And 3 more authors.
Astronomy and Astrophysics | Year: 2013

Aims. The Sagittarius A complex in the Galactic centre comprises an ensemble of molecular clouds of different species with a variety of geometrical and kinematic properties. This work aims to study molecular abundances, morphology, and kinematics by comparing hydroxyl, water, carbon monoxide, ammonia, and atomic carbon and some of their isotopologues, in the +50 km s -1 cloud, the circumnuclear disk (CND), the +20 km s-1 cloud, the expanding molecular ring and the line-of-sight spiral arm features, including the Local/Sgr arm, the-30 km s-1 arm, and the 3-kpc arm. Methods. We observed the +50 km s-1 cloud, the CND and the +20 km s-1 cloud, and other selected positions at the Galactic centre with the VLA, and the Odin satellite. The VLA was used to map the 1665 and 1667 MHz OH lambda doublet main lines of the (2Π3/2) state, and the Odin satellite was used to map the 557 GHz H2O (1 10-101) line as well as to observe the 548 GHz H 2 18O (110-101) line, the 572 GHz NH3 (10-00) line, the 576 GHz CO J = 5-4 line and the 492 GHz Ci (3P1-3P0) line. Furthermore, the SEST was used to map a region of the Sgr A complex in the 220 GHz C18O J = 2-1 line. Results. Strong OH absorption, H2O emission and absorption lines were seen at all observed positions, and the H2 18O line was detected in absorption towards the +50 km s-1 cloud, the CND, the +20 km s-1cloud, the expanding molecular ring, and the 3-kpc arm. Strong CO J = 5-4, C18O J = 2-1, and neutral carbon C i emissions were seen towards the +50 and +20 km s -1 clouds. NH3 was only detected in weak absorption originating in the line-of-sight spiral arm features. The abundances of OH and H2O in the +50 and +20 km s-1 clouds reflect the different physical environments in the clouds, where shocks and star formation prevail in the +50 km s-1 cloud and giving rise to a higher rate of H 2O production there than in the +20 km s-1 cloud. In the CND, cloud collisions and shocks are frequent, and the CND is also subject to intense UV-radiation emanating from the supermassive black hole and the central star cluster. The CND is rich in H2O and OH, and these abundances are considerably higher than in the +50 and +20 km s-1 clouds. We compare our estimated abundances of OH, H2O, and NH3 with similar and differing results for some other sources available in the literature. As compared to the quiescent cloud values of a few × 10 -9, or lower, the H2O abundance is markedly enhanced in the front sides of the Sgr A molecular cloud cores, (2-7) × 10 -8, as observed in absorption, and highest in the CND. A similar abundance enhancement is seen in OH. The likely explanation is PDR chemistry including grain surface reactions, and perhaps also the influence of shocks. In the redward high-velocity line wings of the +50 and +20 km s-1 clouds and the CND, the H2O abundances are estimated to be (1-6) × 10-6 or higher, i.e., similar to the water abundances in outflows of the Orion KL and DR21 molecular clouds, which are said to be caused by the combined action of shock desorption from icy grain mantles and high-temperature, gas-phase shock chemistry. © 2013 ESO. Source


Stenarson J.,Chalmers University of Technology | Stenarson J.,SP Technical Research Institute of Sweden | Do T.N.T.,Chalmers University of Technology | Zhao H.,Chalmers University of Technology | And 5 more authors.
IEEE Transactions on Terahertz Science and Technology | Year: 2013

We present a sensitivity analysis on TRL calibrated S-parameter measurements of membrane circuits in the WR-03 waveguide band (220-325 GHz). The impact of waveguide and membrane circuit misalignment, as well as waveguide dimension mismatch is investigated. The analysis is performed for the thru-reflect-line (TRL) calibration applied to E-plane split waveguide blocks carrying membrane circuits. The analysis shows a large influence of the waveguide width tolerance on transmission and reflection phase after the TRL calibration. For a 20 mm long rectangular waveguide with a ±5μm width tolerance a phase uncertainty as large as ±45° for reflection and ±30° for transmission measurements is observed. © 2011-2012 IEEE. Source


Svedin J.,Swedish Defence Research Agency | Pellikka T.,Omnisys Instruments AB | Huss L.-G.,Swedish Defence Research Agency
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2011

A direct transition from microstrip line to rectangular waveguide compatible with millimeter-wave MMICs is presented. The transition is based on an aperture fed microstrip patch antenna radiating into the waveguide. The microstrip feed line and slot is patterned on the MMIC part and a novel approach using LTCC is presented for realization of the patch antenna and an extension of the waveguide using via walls. By this approach several transitions can be realized simultaneously and freely placed on one or more MMICs. The loss typically encountered going to a separate waveguide probe substrate is thus avoided. The design and simulation results for an LTCC-based transition at W-band is described and measurements on a test transition at G-band is reported. © 2011 Engineers Australia. Source

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