| 1. |
- Lapkin, Igor, 1963, et al.
(author)
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Optics Design and Verification for the APEX Swedish Heterodyne Facility Instrument (SHeFI)
- 2008
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In: In Proceedings of The 19th International Symposium on Space Terahertz Technology, Groningen, 28-30 April, 2008, ed. W. Wild, Space Research Organization of the Netherlands (SRON). ; Part I, s. 351-357
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Conference paper (peer-reviewed)abstract
- We present the design and verification of the receiver optics for the Single-Pixel HeterodyneFacility Instrument (SHFI) of the APEX telescope [1]. The SHFI is designed to cover thefrequency band 211 – 1390 GHz in 6 receiver channels. Four of the receiver channels have beendesigned, installed and characterized: 211-275 GHz (Band 1); 275-370 GHz (Band 2); 385-500 GHz (Band 3); 1250-1390 GHz (Band T2). The first three bands employ 2SB SIS mixertechnology and Band T2 employs HEB mixers in a waveguide balanced mixer configuration.The entire optics design was driven by the receiver position in the telescope Nasmyth cabin“A” (Fig.1) and the aperture limit of Ø150 mm, introduced by the elevation encoder inside theNasmyth tube A. This layout and the telescope geometry (~ 6 m distance from the focal plane tothe Cabin A) lead us to choose a single-pixel configuration and required using intermediateoptics with long focal distances. The common optics path, coupling the receivers to theCassegrain sub-reflector, consists of the three offset ellipsoidal mirrors, M3, M6, M8s, and threeflat mirrors, F4, F5, and F7s. The combination M3 and M6 via flat F4, F5, creates a Gaussiantelescope, providing frequency-independent re-imaging of the antenna focal plane from theCassegrain cabin into the Nasmyth cabin A. Switching between channels is achieved by theprecision rotating of the active mirror M8s. The mirror M8s in combination with each channelactive mirror M10 provides re-imaging of the secondary onto the feed horn aperture of theselected channel. Such a configuration provides frequency independent illumination of thesecondary with the edge taper -12dB. The angular position of the flat mirrors F9 is adjustable andgives additional possibility of fine-tuning of the beam alignment from the common optics toevery receiver channels.Verification of the optical designthrough measurements is essential inorder to align the beams from thecryostat windows to the commonoptics to minimize loss in thequasioptical guiding system. In orderto verify the design of the cold optics(corrugated horn + M10) in terms ofGaussian beam parameters, a newwideband vector field measurementsystem was developed [2]. Vectorfield measurements were performedfor band 1, 2, and 3, and scalarmeasurements were employed for theTHz band.
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| 2. |
- Vassilev, Vessen, 1969, et al.
(author)
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A Swedish heterodyne facility instrument for the APEX telescope
- 2008
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 490:3, s. 1157-1163
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Journal article (peer-reviewed)abstract
- In March 2008, the APEX facility instrument was installed on the telescope at the site of Lliano Chajnantor in northern Chile. The main objective of the paper is to introduce the new instrument to the radio astronomical community. It describes the hardware configuration and presents some initial results from the on-sky commissioning.The heterodyne instrument covers frequencies between 211 GHz and 1390 GHz divided into four bands. The first threebands are sideband-separating mixers operating in a single sideband mode and based on superconductor-insulator-superconductor (SIS) tunnel junctions. The fourth band is a hot-electron bolometer, waveguide balanced mixer. All bands are integrated in a closedcycle temperature-stabilized cryostat and are cooled to 4 K.We present results from noise temperature, sideband separation ratios, beam, and stability measurements performed on the telescope as a part of the receiver technical commissioning. Examples of broad extragalactic lines are also included.
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| 3. |
- Meledin, Denis, 1974, et al.
(author)
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APEX Band T2: A 1.25 – 1.39 THz Waveguide Balanced HEB Receiver
- 2008
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In: Proceedings of The 19th International Symposium on Space Terahertz Technology, Groningen, 28-30 April, 2008, ed. W. Wild, Space Research Organization of the Netherlands (SRON). ; part I, s. 162-166
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Conference paper (peer-reviewed)abstract
- A waveguide 1.25 - 1.39 THz Hot Electron Bolometer (HEB) balanced receiver was successfully developed, characterized and installed at the Atacama Pathfinder EXperiment (APEX) telescope. The receiver employs a quadrature balanced scheme using a waveguide 90-degree 3 dB RF hybrid, HEB mixers and a 180-degree IF hybrid. The HEB mixers are based on ultrathin NbN film deposited on crystalline quartz with a MgO buffer layer. Integrated into the multi-channel APEX facility receiver (SHeFI), the results presented here demonstrate exceptional performance; a receiver noise temperature of 1000 K measured at the telescope at the center of the receiver IF band 2-4 GHz, and at an LO frequency of 1294 GHz. Stability of the receiver is in line with the SIS mixer bands of the SHeFI, and gives a spectroscopic Allan time of more than 200 s at 1382 GHz with a noise bandwidth of 1 MHz.
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| 4. |
- Nyström, Olle, 1979, et al.
(author)
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Low-Noise Cryogenic Amplifier built using Hybrid MMIC-like / TRL Technique
- 2008
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In: GigaHertz Symposium, March 5-6, 2008, Göteborg.
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Conference paper (other academic/artistic)abstract
- HEMT cryogenic low-noise amplifiers are an important part of instrumentation: the amplifiersuse as a front-end for different measurements and as IF amplifiers in heterodyne receivers.During last few years the low-noise limit has reached as low level as approximately 0.5 K/GHzfor GaAs [1] and 0.25 K/GHz for InP HEMT [2]. However, besides electrical performanceimprovement there were not many improvements on mass and dimension side of suchamplifiers as they were built based on standard TRL technology with discrete active andpassive components. Mass and dimensions are also very important for real applications. Whenultimate low-noise performance is placed in focus, pure MMIC technology seems to looseagainst design using discrete components. With this in view, pioneered work by E. F. Lauria,et. al. [3] have successfully demonstrated a design employing MMIC approach while usingdiscrete components and based on a microstrip on Cuflon with lumped bias network.Encouraged by this work, we propose a compact design of a 4-8 GHz cryogenic low noiseamplifier using a combination of standard TRL and lumped element technology to achieveboth ultimate noise performance over the specified band and a very compact size. In ourdesign, the size reduction of the amplifier is realized by selecting an alumina substrate with ahigh dielectric constant, (εr = 9.9), but also by taking advantage of the lumped networks in thematching and bias circuitries. Avoiding quarter wave transformers and instead use a lumpedelement design approach opens up for the possibilities to reach greater bandwidths andsimultaneously obtain a more compact design. In order to make optimum design, we haveperformed extensive simulations. Each amplifier stage has been simulated in Agilent EMDS,3D electromagnetic field simulation package, including the single layer capacitors, and thenimplemented in the ADS circuit simulations as an S-parameter file. Over the 4-8 GHz band, thesimulations predict noise temperature, Taverage 35 dB. The transistors selected for the design are commercial InP HEMT (HRL) chosendue to their excellent noise performance [2], but also for the very low power consumption,which is of great importance at cryogenic temperatures. All the components used in the RFsignalpath and in the bias circuits are mounted with conductive epoxy. Apart from the RFsignalpath, all components are interconnected via bond-wires. Fine tuning is done by adjustingthe length and loop heights of the bond-wires. At the conference we plan to report results ofmeasurement and characterization of the prototype amplifier.REFERENCES:[1] C Risacher, et. al., “Low Noise and Low Power Consumption Cryogenic Amplifiers forOnsala and Apex Telescopes”, Proceedings of Gaas 2004, October 2004, Amsterdam.[2] N. Wadefalk, et. al., “Cryogenic Wide-Band Ultra-Low Noise IF Amplifier Operating atUltra-Low DC-Power”, IEEE Transactions on Microwave Theory and Techniques, vol. MTT-51, no. 6 June 2003.[3] E. F. Lauria, et. al., “A 200-300 GHz SIS Mixer-Preamplifier with 8 GHz IF Bandwidth”,2001 IEEE International Microwave Symposium, Phoenix, AZ, May 2001.
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| 5. |
- Vassilev, Vessen, 1969, et al.
(author)
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Design and Characterization of a 211-275 GHz Sideband Separating Mixer for the APEX Telescope
- 2008
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In: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 18:1, s. 58 - 60
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Journal article (peer-reviewed)abstract
- We present the final results of the development and characterization of the sideband separating superconductor-insulator-superconductor (SIS) mixer for the APEX telescope band 1 (211-275 GHz).The sideband separation is achieved by using a quadrature scheme where the RF and a local oscillator (LO) power are applied to two identical double sideband SIS mixers. All mixer components, including the LO and RF distribution circuitry, are integrated into a single mixer block. To achieve a compact design we developed a superconducting Lange coupler, based on Nb thin film, which is used as an IF hybrid. Typical single sideband noise temperature of 100˚K and sideband rejection ratio of about 12 dB and are measured.
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| 6. |
- Gradinarsky, Lubomir, 1970, et al.
(author)
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A method for detection of powder materials in metallic hollow structures using microwaves
- 2008
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In: Measurement: Journal of the International Measurement Confederation. - : Elsevier BV. - 0263-2241. ; 41:6, s. 637-646
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Journal article (peer-reviewed)abstract
- This paper presents a method for detection of the presence of small amounts of solids (powders, granules, etc.) inside metallic structures such as process vessels and containers. The method is based on propagation of microwave electromagnetic (EM) energy inside the structures and analysing the complex reflection coefficient Gamma represented by the scattering parameter S-11. 3D EM simulations were used to predict the behaviour of S for structures of rectangular, circular, and conical shapes, contaminated with materials with weak dielectric properties. The suggested method sensitivity and the effects of the material size and its distribution were assessed and results presented of comparisons of simulations and measurements. This paper demonstrates the ability to detect very low levels of contamination, e.g. of the order of 0.01-0.03 parts of a reference vessel's volume of one (e.g. length = 1 cm, width = 0.5 cm, and height = 2 cm) for materials with weak dielectric properties. This sensitivity is even better in terms of volume ratio (contamination/vessel's volume) for structures with bigger volumes and contaminants with stronger dielectric properties e.g. wet powders. The method is fully scalable for vessels with different sizes. Therefore industrial application of the method to physical processing of pharmaceutics, food, agriculture and others is envisioned. (C) 2007 Elsevier Ltd. All rights reserved.
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| 7. |
- Nyström, Olle, 1979
(author)
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THz Vector Beam Measurement System for APEX Instrument SHeFI and Microwave Cryogenic Low Noise Amplifier Design
- 2008
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Licentiate thesis (other academic/artistic)abstract
- This licentiate thesis describes results of the author’s work on development of THz vector beam measurement system and microwave cryogenic low-noise amplifier.The first part, and the main focus, of the thesis covers the vector beam measurement system for frequency range 210-500 GHz developed to characterize/verify the cold opticsof the APEX instrument SHeFI. The measurement system, based on a novel design employing combination of a single frequency source, comb-generator, and direct multiplication signal sources, is described in detail. The system configuration allows very narrow detection bandwidth giving the advantage of high dynamic range. With minor rearrangements, the same setup is used to characterize the three first receiving bands of SHeFI, covering the frequency range 211-500 GHz.In the first part of the thesis, the results from the measurements are presented and complemented with an extensive error analysis of the measurement setup. Additionally, we present results of the scalar beam characterization at 1334 GHz. One chapter of thethesis is also dedicated to describe the installation procedure at the telescope, where results from the first telescope pointing tests are presented. The second part of the thesis deals with the development of a three stage low-noise cryogenic amplifier based on InP-High Electron Mobility Transistors HEMTs for the frequency range 4-8 GHz. The design employs a combination of standard TRL, based onalumina substrate, and lumped element technology to achieve both ultimate noise performance over the specified band and a very compact size. Simulation results are presented together with the first preliminary measurement results (employing GaAs HEMTs).
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