| 1. |
- Hammar, Arvid, 1986, et al.
(författare)
-
Low noise 874 GHz receivers for the international submillimetre airborne radiometer (ISMAR)
- 2018
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 89:5
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Tidskriftsartikel (refereegranskat)abstract
- We report on the development of two 874 GHz receiver channels with orthogonal polarizations for the international submillimetre airborne radiometer. A spline horn antenna and dielectric lens, a Schottky diode mixer circuit, and an intermediate frequency (IF) low noise amplifier circuit were integrated in the same metallic split block housing. This resulted in a receiver mean double sideband (DSB) noise temperature of 3300 K (minimum 2770 K, maximum 3400 K), achieved at an operation temperature of 40 C and across a 10 GHz wide IF band. A minimum DSB noise temperature of 2260 K at 20 C was measured without the lens. Three different dielectric lens materials were tested and compared with respect to the radiation pattern and noise temperature. All three lenses were compliant in terms of radiation pattern, but one of the materials leads to a reduction in a noise temperature of approximately 200 K compared to the others. The loss in this lens was estimated to be 0.42 dB. The local oscillator chains have a power consumption of 24W and consist of custom-designed Schottky diode quadruplers (5% power efficiency in operation, 8%-9% peak), commercial heterostructure barrier varactor (HBV) triplers, and power amplifiers that are pumped by using a common dielectric resonator oscillator at 36.43 GHz. Measurements of the radiation pattern showed a symmetric main beam lobe with full width half maximum <5 and side lobe levels below 20 dB. The return loss of a prototype of the spline horn and lens was measured using a network analyzer and frequency extenders to be 750-1100 GHz. Time-domain analysis of the reflection coefficients shows that the reflections are below 25 dB and are dominated by the external waveguide interface.
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| 2. |
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| 3. |
- Sobis, Peter, 1978, et al.
(författare)
-
SWI 1200/600 GHz highly integrated receiver front-ends
- 2015
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Ingår i: 36th ESA Antenna Workshop on Antennas and RF Systems for Space Science, ESA/ESTEC ,Noordwijk, The Netherlands; 6-9 Oct. 2015. ; session S3.1.2
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Konferensbidrag (refereegranskat)
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| 4. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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Investigation of MgB2 HEB mixer gain bandwidth
- 2011
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Ingår i: International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz), 2011. - 2162-2027. - 9781457705083 ; , s. 1 - 2
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Konferensbidrag (refereegranskat)abstract
- THz mixers based on superconducting MgB2 bolometers were fabricated by photolithography and Ar-ion beam milling on sapphire substrates. The mixer gain bandwidth of 3.4 GHz, 2.3 GHz and 1.3 GHz were measured for 10, 15 and 30 nm films respectively.
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| 5. |
- Cherednichenko, Serguei, 1970, et al.
(författare)
-
A room temperature bolometer for terahertz coherent and incoherent detection
- 2011
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 1:2, s. 395 - 402
-
Tidskriftsartikel (refereegranskat)abstract
- We present a novel room temperature bolometer with nanosecond response that can be used both for coherent and incoherent detection through the entire terahertz frequency range. A responsivity of up to 15 V/W, and a noise equivalent power (NEP) = 450 pW/Hz0.5 were measured at modulation frequencies from 0.5 kHz to 100 kHz. A conversion gain of -28 dB was demonstrated at an intermediate frequency of 20 MHz with a Local Oscillator power of 0.74 mW. Possible improvements of the bolometer characteristics are discussed.
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| 6. |
- Cherednichenko, Serguei, 1970, et al.
(författare)
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Wideband THz detectors based on YBCO thin films at 77K and at room temperature
- 2011
-
Ingår i: 6th ESA Workshop on Millimetre-Wave Technology and Applications.
-
Konferensbidrag (refereegranskat)abstract
- We present results of experimental investigation of THz direct detectors based on ultrathin YBCO films. The detectors are integrated with a spiral planar antenna. In the frequency band of 0.1-1.6THz the optical responsivity is from 170V/W for 77K. It increases to 400 V/W for operation temperature about 76K. The responsivity was constant up to 100kHz. Using mixing technique, the measured time constant is 0.5-2ns. Currently, at 77K, the NEP is 20pW/Hz0.5. At room temperature, the NEP is about 250pW/Hz0.5. For the same devices as coherent detector, the mixer gain was -21dB at 77K (and -28dB) at room temperature for an LO power of 0.4mW. With the present devices a mixer gain of up to -23dB is possible at 300K for an LO power of 1.5mW. Using smaller devices, similar gain can be achieved for a much smaller LO power.
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| 7. |
- Giono, G., et al.
(författare)
-
Characterisation of the analogue read-out chain for the CCDs onboard the mesospheric airglow/aerosol tomography and spectroscopy (MATS)
- 2018
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781510619494 ; 10698
-
Konferensbidrag (refereegranskat)abstract
- The MATS satellite aims at observing airglow and noctilucent clouds in the mesosphere. The main instrument consists of a six channels limb imager in the near-ultraviolet and near-infrared. A high signal-to-noise ratio is required for detecting these mesospheric phenomena: 100 and 500 for ultraviolet and infrared, respectively. This is achieved by an optical design minimizing stray-light, but also with a dedicated design of the read-out analogue chain for the CCD on each channel. The requirements and expected light level on the imaging channels are brie y discussed before focusing on the CCD read-out analogue chain, for which the design and performances are presented.
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| 8. |
- Gumbel, Jörg, et al.
(författare)
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The MATS satellite mission - gravity wave studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy
- 2020
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Ingår i: Atmospheric Chemistry And Physics. - : COPERNICUS GESELLSCHAFT MBH. - 1680-7316 .- 1680-7324. ; 20:1, s. 431-455
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Tidskriftsartikel (refereegranskat)abstract
- Global three-dimensional data are a key to understanding gravity waves in the mesosphere and lower thermosphere. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that addresses this need. It applies space-borne limb imaging in combination with tomographic and spectroscopic analysis to obtain gravity wave data on relevant spatial scales. Primary measurement targets are O-2 atmospheric band dayglow and nightglow in the near infrared, and sunlight scattered from noctilucent clouds in the ultraviolet. While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric temperature, composition, and cloud properties. Based on these dynamical tracers, MATS will produce a climatology on wave spectra during a 2-year mission. Major scientific objectives include a characterization of gravity waves and their interaction with larger-scale waves and mean flow in the mesosphere and lower thermosphere, as well as their relationship to dynamical conditions in the lower and upper atmosphere. MATS is currently being prepared to be ready for a launch in 2020. This paper provides an overview of scientific goals, measurement concepts, instruments, and analysis ideas.
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| 9. |
- Hammar, Arvid, 1986, et al.
(författare)
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A 340 GHz High Gaussicity Smooth Spline Horn Antenna for the STEAMR Instrument
- 2014
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Ingår i: IEEE Antennas and Propagation Society, AP-S International Symposium (Digest). - 1522-3965. - 9781479935383 ; , s. 649-650
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Konferensbidrag (refereegranskat)abstract
- We present the design, fabrication and measure-ments of a smooth walled spline feed horn antenna for the satellite borne climate research instrument STEAMR operating at 340GHz. A method has been developed which, for a certain desired beam waist, can be used to optimize the horn profile for high Gaussicity and ultra-low sidelobes. The simulated performance of the horn achieves a beam waist of 1.9 mm over the band 323-357 GHz with Gaussian coupling efficiency exceeding 98%. The peak cross-polar sidelobes are below -28 dB over the required frequency band. For cost effective manufacturing with high repeatability, the smooth wall spline profile is drilled in out from a metal block using a custom made broach. To validate the design and fabrication, planar measurements of the phase and amplitude have been performed and from measured E-field vital horn parameters have been extracted.
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| 10. |
- Hammar, Arvid, 1986, et al.
(författare)
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A 600 GHz Orthomode Transducer based on a Waveguide Integrated Wire Grid Polarizer
- 2012
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Ingår i: TWENTY-THIRD INTERNATIONAL SYMPOSIUM ON SPACE TERAHERTZ TECHNOLOGY (ISSTT2012).
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Konferensbidrag (refereegranskat)abstract
- Abstract — We present a new type of orthomode transducer (OMT), involving the integration of a quasi-optical component, namely a wire grid polarizer (WGP), with an E-plane probe transition, in a waveguide topology. The goal has been to create a lightweight and compact device for waveguide integration, capable of covering all frequency channels to be used by the FIRE instrument¤.The design consists of a metallic split block, in which a quadratic waveguide supporting the two fundamental modes of propagation (TE10 and TE01), is formed using regular CNC milling. Just as its quasi-optical counterpart, i.e. a free standing WGP, a waveguide integrated WGP insert is used to separate the two orthogonal TE modes, which are either reflected or transmitted (depending on polarization). A planar E-plane waveguide probe transition realized on a GaAs membrane is used inside a square waveguide to extract the reflected mode without affecting the transmitted mode. For a first proof of concept the OMT has been designed for the possibility of full characterization and therefore the transmitted mode is guided through a stepped impedance transformer to a standard rectangular waveguide interface, while a second E-plane probe transition to a rectangular waveguide, is used for the reflected mode. Simulations carried out using Ansoft HFSS show that the OMT design can be made relatively broadband (currently about ~14% with a return loss better than 15 dBs) and with cross-polarizations better than 30 dB. The probe and WGP can be manufactured using high precision photolithography or E-beam lithography making it scalable to both lower and higher frequency bands. Assembling an OMT of this type involves mounting of small membrane structures (
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| 11. |
- Hammar, Arvid, 1986
(författare)
-
Optical Analysis and Characterisation of the Climate Research Instrument STEAMR
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A growing interest for making high resolution observations in the upper troposphere and lower stratosphere has motivated the development of the multi-beam satellite-borne instrument Stratosphere-Troposphere Exchange And climate Monitor Radiometer (STEAMR). The measurements made by STEAMR will be used to monitor trace-gases and link the occurence of these to the Earth's climate by accurate modeling of the atmosphere. To interpret the measured data require a firm understanding of the coupling between the radiation emitted from the atmosphere to the signal being received by the instrument's optical system. Thus, precise knowledge of the instrument's optical performance while in orbit is crucial. This thesis is dedicated to the study of optical analysis and measurements of the highly advanced optical system of the STEAMR instrument. A mechanical tolerance analysis of the complete optical system consisting of two polarisation separated focal plane arrays, a four reflector anastigmatic relay optics chain and an off-axis Ritchey-Chretien telescope was performed. Using Monte-Carlo simulations in combination with ray-tracing and physical optics/physical theory of diffraction, it could be concluded that the overall reflector alignment accuracy from manufacturing should be better than 100 µm. Surface distortion analyses of the 1.6 m × 0.8 m primary reflector highlighted the need for an optical system with high stability in orbit (
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| 12. |
- Hammar, Arvid, 1986, et al.
(författare)
-
Optical designs for a multi-beam 340 and 625/640 GHz Spaceborne climate research instrument
- 2015
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Ingår i: 26th International Symposium on Space Terahertz Technology, ISSTT 2015.
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Konferensbidrag (refereegranskat)abstract
- We report on an ongoing study where different optical configurations for a multi-beam limb-viewing (four to eight receiver channels at 340 and two channels at 625 GHz) space-borne instrument for climate research are presented and compared. The optical configurations are analyzed in terms of optical performance (gain, side lobe levels, beam efficiency etc.), weight and size of the overall instrument envelope. Using ideal fundamental Gaussian beam modes and numerical tools relying on ray-tracing and physical optics methods, the different configurations are designed and evaluated. Preliminary results indicate that a 1.3 m × 0.65 m primary reflector can be used in a configuration that includes a relay optics system having two to four elements. In addition to the limb-viewing instrument, there will be an additional instrument operating at 640 GHz for observing clouds in nadir mode.
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| 13. |
- Hammar, Arvid, 1986, et al.
(författare)
-
Optical Tolerance Analysis for the STEAMR Instrument
- 2013
-
Ingår i: TWENTY-FOURTH INTERNATIONAL SYMPOSIUM ON SPACE TERAHERTZ TECHNOLOGY (ISSTT2013).
-
Konferensbidrag (refereegranskat)abstract
- The optics of the STEAMR instrument is a complex system involving off-axis mirrors designed to achieve precise imaging of the 14 receiver channel beams from the far field to the corresponding feed horns. An initial optical design was generated by Swedish Space Corporation, which laid the framework for the subsequent IAP design that further developed the optical system to meet the mission performance requirements. Omnisys Instruments is now the prime contractor for the complete STEAMR instrument.Although simulations of the optics presently show good results, little is known about the sensitivity to mechanical errors, i.e. surface deviations and misalignments of the reflectors. This work encompasses a tolerance analysis for the complete optics chain consisting of a 28 reflector focal plane array (FPA) and 6 reflector relay optics. With six degrees of freedom for each reflector, the scale of the required mechanical tolerancing analysis is significant. The goal of this work is therefore to identify critical locations within the optics architecture that have the largest influence on performance.Being a multi-beam instrument, the optics requirements for STEAMR can be divided into two parts: pointing and beam quality. Pointing errors were analysed using the commercial software package ZEMAX, which offers built-in routines for performing Monte-Carlo simulations specifically for tolerancing problems. Beam quality, i.e. sidelobe levels, beam efficiency and polarization plane, were analysed using physical optics routines in GRASP. Simulations in both programs have been carried out using single element perturbation and Monte-Carlo simulations on the complete optics chain.In the first iteration of the analysis, all reflector surfaces were assumed to be perfect. In later analyses, surface errors were also added. Special attention was given to the 1.6 m x 0.8 m carbon fiber main reflector, which is the most sensitive in terms of errors in shape. By running the optical analysis in parallel and in close cooperation with the mechanical design, it has been possible to assume realistic errors for the different parts of the optics. Measurements of the feed horns done by IAP show excellent agreement with simulations, where sidelobe levels around -40 dB was predicted. Therefore, the beams of all feeds have been modelled as perfect Gaussians.
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| 14. |
- Hammar, Arvid, 1986, et al.
(författare)
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Optical Tolerance Analysis of the Multi-Beam Limb Viewing Instrument STEAMR
- 2014
-
Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 4:6, s. 714-721
-
Tidskriftsartikel (refereegranskat)abstract
- We report on an optical tolerance analysis of the submillimeter atmospheric multi-beam limb sounder STEAMR. Physical optics and ray-tracing methods were used to quantify and separate errors in beam pointing and distortion due to reflector misalignment and primary reflector surface deforma-tions. Simulations were performed concurrently with the man-ufacturing of a multi-beam demonstrator of the relay optical system which shapes and images the beams to their corresponding receiver feed horns. Results from Monte-Carlo simulations show that the inserts used for reflector mounting should be positioned with an overall accuracy better than 100 µm (~1/10 wavelength). Analyses of primary reflector surface deformations show that a deviation of magnitude 100 µm can be tolerable before deployment, whereas the corresponding variations should be less than 30 µm during operation. The most sensitive optical elements in terms of misalignments are found near the focal plane. This localized sensitivity is attributed to the off-axis nature of the beams at this location. Post-assembly mechanical measurements of the reflectors in the demonstrator show that alignment better than 50 µm could be obtained.
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| 15. |
- Hammar, Arvid, 1986
(författare)
-
Optics for Earth Observation Instruments
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The optical system is an essential part of every remote sensing instrument used for detecting electromagnetic waves. Careful design, fabrication and characterization is therefore crucial, especially for satellite-borne missions where the possibility of post-launch repairs is highly limited. This thesis presents contributions to a new type of reflector optics and horn antennas for three instruments for Earth observation, which operate at wavelengths between the UV and millimeter-wave regions: Mesospheric Airglow/Aerosol Tomography Spectroscopy (MATS), International Submillimetre Airborne Radiometer (ISMAR) and Stratosphere-Troposphere Exchange And climate Monitor Radiometer (STEAMR). A free-form three-mirror off-axis telescope was developed for the limb instrument on board the MATS satellite. The f/7.3 (D = 35 mm) design achieved diffraction-limited performance (at 270-772 nm) over a wide field (5.67° × 0.91°) by applying a new design method that corrects for linear astigmatism. Single point diamond turning was used to fabricate the free-form mirrors, which resulted in a telescope with a modulation transfer function of 0.45 at 20 lp/mm. Simulations and measurements were used to assess stray light rejection of the limb instrument. Measurements of a breadboard front baffle with a new type of extremely black coating showed a point source transmittance down to 10-6, which was in excellent agreement with simulations. Detailed modeling predicted a stray light rejection of 10-10-10-4 in the most critical region below the nominal field of view. Two 874 GHz Schottky mixer receivers with integrated low noise amplifiers, spline horns and low-loss dielectric lenses were developed for ISMAR, which exhibited record-low receiver noise temperatures of 2260-2770 K. Radiation patterns were measured between 868.7-880.0 GHz in a setup capable of resolving side lobes down to 25-30 dB below the main peak. The main beam full-width-half-maximum was in good agreement with simulations and well below the required 5°. Spline horn antennas at frequencies 120-340 GHz were also developed. An efficient optimization algorithm based on mode matching in circular waveguides was used for all designs, which exhibited Gaussicity values of 98% over bandwidths up to 19%. Far field radiation patterns were measured using a setup for spherical and planar scanning geometries. A mechanical tolerance analysis was performed for the optical system of STEAMR, which consists of two polarization-separated focal plane arrays, a four-reflector anastigmatic relay optics chain and an off-axis Ritchey-Chretien telescope. Using Monte-Carlo simulations based on ray-tracing and physical optics, an overall reflector alignment accuracy requirement of 100 μm was obtained. Surface distortion analyses of the 1.6 m × 0.8 m primary reflector highlighted the need for an optical system with small mechanical variations in orbit (<30 μm). A relay optics demonstrator showed that alignment accuracies down to 50 μm could be obtained. In conclusion, the methods for design, manufacturing and characterization presented in this thesis can be used to develop new instruments for Earth observation and related fields.
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| 16. |
- Hammar, Arvid, 1986, et al.
(författare)
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Stray light suppression of a compact off-axis telescope for a satellite-borne instrument for atmospheric research
- 2018
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 10815
-
Konferensbidrag (refereegranskat)abstract
- In this study, simulations and measurements were used to investigate stray light properties of the three-mirror off-axis telescope of a new satellite for atmospheric research called Mesospheric Airglow/Aerosol Tomography Spectroscopy (MATS). A 700 mm breadboard baffle for stray light rejection has been designed and tested. Good performance was achieved by coating the baffle’s inside with Vantablack S-VIS R , which has a hemispherical reflectance of 0.2-0.6% across the instrument’s detection band (270-776 nm). A point source transmittance (PST) down to 10−6 was measured for the full-size baffle breadboard. This is in excellent agreement with simulations performed in OpticStudio/LightTools, where scattering was modeled using empirical BRDF data. From the breadboard results, a simulation model of a flight-representative prototype model of the entire instrument was set up in OpticStudio. Strong signals just outside the field of view constitute the biggest challenge, where a PST in the order of 10-6 − 10-4 is required. Simulations suggest that the PST of the prototype limb instrument will be lower than this. Adding to these simulations, an instrument model was developed, which will be utilized by the end-users to remove unwanted features in the data stemming from the instrument itself. Besides stray light, the model also takes into account the most relevant aspects of the instrument, such as image resolution (from measured/simulated point spread functions), image sensor characteristics as well as temperature and wavelength dependencies.
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| 17. |
- Hammar, Arvid, 1986, et al.
(författare)
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Terahertz Direct Detection in YBa2Cu3O7 Microbolometers
- 2011
-
Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 1:2, s. 390 - 394
-
Tidskriftsartikel (refereegranskat)abstract
- A high sensitivity broadband terahertz direct detector based on YBa2Cu3O7 high-Tc superconductor microbolometers is presented. At 77 K, the responsivity of the spiral antenna-integrated microbolometers (1.5 um x 1.5 um) is 190 V/W, referenced to the input of the silicon substrate lens, across the frequency range of 330 GHz–1.63 THz in a single device. The response time is approximately 300 ps. Using a room temperature readout, we measure an optical noise equivalent power (NEP) of 20 pW/Hz^0.5 (readout noise limited) for modulation frequencies ranging from 500 Hz to 100 kHz.
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| 18. |
- Hammar, Arvid, 1986, et al.
(författare)
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Terahertz response of YBCO HEB homodyne detectors
- 2011
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Ingår i: 22nd International Symposium on Space Terahertz Technology 2011, ISSTT 2011; Tucson, AZ; United States; 25 April 2011 through 28 April 2011. ; , s. 81-
-
Konferensbidrag (refereegranskat)abstract
- We report on the direct response of hot electron bolometers (HEB) used as homodyne detectors. These bolometers were tested at frequencies 0.1-1.6 THz and for a range of temperatures around 77 K. A logarithmic spiral antenna on a silicon lens was used, providing a broad frequency coverage (well above 1 THz). The measured responsivity ranged from 100 to 500 V/W depending on temperature and RF signal frequency, with RF signal power referenced at the input of the silicon lens. Corrections were made for losses in the cryostat window and polarization losses between the signal and antenna. The response time was about 3 ns. With the room temperature readout we estimate the noise equivalent power to be about 1 nW/Hz1/2. The bolometer bridges have nominal dimensions 1 μm x 2 μm x 50 nm and are fabricated on sapphire substrates using UV photolithography. A gas laser was used as source for 1.6 and 0.7 THz RF signals, backward wave oscillators at 0.5 THz and Gunn diodes at 0.1 THz. The obtained results show that YBCO bolometers have good prospects for various applications in the terahertz range as fast direct detectors as well as broadband mixers.
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| 19. |
- Hammar, Arvid, 1986, et al.
(författare)
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THz smooth-walled spline horn antennas: Design, manufacturing and measurements
- 2016
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Ingår i: 2016 IEEE Antennas and Propagation Society International Symposium, APSURSI 2016, Fajardo, Puerto Rico, 26 June - 1 July 2016. - 1947-1491. - 9781509028863 ; , s. 1341-1342
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Konferensbidrag (refereegranskat)abstract
- We describe a versatile and cost-efficient method for producing smooth-walled spline horn antennas for applications in THz radiometry. Specifically, the development of four different horns for radiometer receiver applications at frequencies 120, 183, 340 and 874 GHz is presented. General methods for efficient optimization of the spline profiles have been developed which enable the horn designs to be tailored to each application. All four designs display high Gaussicity (typically ∼98%). Manufacturing methods based on numerical milling in splitblocks, lathing and drilling have been tested and compared. Milled splitblock horns with integrated receiver circuits (Shottky mixers in this case) allow for lower losses in the receiver system at the expense of higher cross-polarization levels. The radiation pattern of three designs at 183, 340 and 874 GHz have been measured using planar and rotational scanners.
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| 20. |
- Hammar, Arvid, 1986, et al.
(författare)
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Wide-field off-axis telescope for the Mesospheric Airglow/Aerosol Tomography Spectroscopy satellite
- 2019
-
Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 58:6, s. 1393-1397
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Tidskriftsartikel (refereegranskat)abstract
- We present the development of a compact ?/7.3 (?=35 mm) three-mirror reflective telescope for the atmospheric-research microsatellite Mesospheric Airglow/Aerosol Tomography Spectroscopy (MATS). The telescope design was driven by the end users’ need for a reflective wide-field (5.67°×0.91°) optic with high stray light rejection and six detection channels with separate image sensors, operating at wavelengths 270–772 nm. For the first time, a design method for wide-field off-axis telescopes—in which linear astigmatism is eliminated—was applied and tested in practice. Single-point diamond turning was used to produce two sets of 37–110 mm large free-form aluminum mirrors with surface figure errors and roughness values of 34–62 nm (RMS)/193–497 nm (PV) and 2.8–3.5 nm (RMS), respectively. A method that combines precise machining and geometry measurements (using a coordinate measuring machine) was employed to fabricate an aluminum structure to accurately position the mirrors without the need for manual alignment. The telescope was tested with a network of plate beamsplitters and filters, which define the spectral selection for the six detection channels. Imaging performance measurements were carried out using a reflective off-axis collimator, which projects imaging targets at infinite focus. A modulation transfer function (MTF) value of 0.45 at 20 lp/mm was measured at ∼760 nm (diffraction limit: 0.85) using a slanted edge target. By modeling the measured mirror surfaces in optical design software, a reoptimization of the mirror positions could be performed and an improved MTF of ∼0.75 at 20 lp/mm was predicted. The results demonstrate design- and building methods that can be utilized to make off-axis telescopes for a vast range of applications.
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| 21. |
- Hammar, Arvid, 1986, et al.
(författare)
-
YBCO HEB THz mixers
- 2011
-
Ingår i: 22nd International Symposium on Space Terahertz Technology 2011, ISSTT 2011; Tucson, AZ; United States; 25 April 2011 through 28 April 2011. ; , s. 82-
-
Konferensbidrag (refereegranskat)abstract
- We report on an experimental investigation of high-Tc superconducting hot electron bolometer (HEB) mixers of YBCO. These mixers were tested at 100 and 530 GHz LO for a range of temperatures around 77 K. The conversion gain of -32 dB was measured at an LO power of about 1 mW (530 GHz) and 0.3 GHz IF. The mixers were integrated with a logarithmic spiral antenna on a silicon lens, providing a broad frequency coverage (well above 1 THz). To measure the incident RF signal power we used the homodyne responsivity (see abstract "Terahertz response of YBCO HEB homodyne detectors") which is referenced to the input of the silicon lens where the bolometers were glued. Corrections were made for losses in the cryostat window and polarization losses between the signal and antenna. We made the measurements at different temperatures and different LO power levels which were measured using a quasi optical detector at room temperature. The 3 dB gain bandwidth was measured to be about 0.2 GHz. The bolometer bridges have nominal dimensions 1 μm x 2 μm x 50 nm and are fabricated on sapphire substrates using UV photolithography. Backward wave oscillators sources were used at 530 GHz and Gunn diodes at 100 GHz.
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| 22. |
- Karandikar, Yogesh, 1982, et al.
(författare)
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A 874 GHz Mixer Block Integrated Spline Horn and Lens Antenna for the ISMAR Instrument
- 2015
-
Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we present the design of a 874 GHz mixer block-integrated antenna for the ISMAR Instrument. The spline horn antenna with a dielectric lens (Teflon) is used to fulfill the requirement of an on-axis Directivity exceeding 32 dBi. The well designed spline horn offers very high Gaussian Coupling, exceeding 97%. This property of spline horn further helps to achieve very rotationally symmetric beam even after the lens with very low cross-polarization (
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| 23. |
- Park, Woojin, et al.
(författare)
-
Flight model characterization of the wide-field off-axis telescope for the MATS satellite
- 2020
-
Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 59:17, s. 5335-5342
-
Tidskriftsartikel (refereegranskat)abstract
- We present optical characterization, calibration, and performance tests of the Mesospheric Airglow/Aerosol Tomography Spectroscopy (MATS) satellite, which for the first time, to the best of our knowledge, for a satellite, applies a linear-astigmatism-free confocal off-axis reflective optical design. Mechanical tolerances of the telescope were investigated using Monte Carlo methods and single-element perturbations. The sensitivity analysis results indicate that tilt errors of the tertiary mirror and a surface RMS error of the secondary mirror mainly degrade optical performance. From the Monte Carlo simulation, the tolerance limits were calculated to ±0.5 mm, ±1 mm, and ±0.15◦ for decenter, despace, and tilt, respectively. We performed characterization measurements and optical tests with the flight model of the satellite. Multi-channel relative pointing, total optical system throughput, and distortion of each channel were characterized for end-users. Optical performance was evaluated by measuring the modulation transfer function (MTF) and point spread function (PSF). The final MTF performance was 0.25 MTF at 20 lp/mm for the ultraviolet channel (304.5 nm), and 0.25-0.54 MTF at 10 lp/mm for infrared channels. The salient fact of the PSF measurement of this system is that there is no noticeable linear astigmatism detected over a wide field of view (5.67◦ × 0.91◦). All things considered, the design method showed great advantages in wide field of view observations with satellite-level optical performance.
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| 24. |
- Sobis, Peter, 1978, et al.
(författare)
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4.7 THz GaAs Schottky diode receiver components
- 2019
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Ingår i: ISSTT 2019 - 30th International Symposium on Space Terahertz Technology, Proceedings Book. ; , s. 133-
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Konferensbidrag (refereegranskat)
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| 25. |
- Sobis, Peter, 1978, et al.
(författare)
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Membrane Integrated Asymmetric Dual E-plane Probe Ortho Mode Transducer at 424 GHz
- 2018
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Ingår i: ISSTT 2018 - 29th IEEE International Symposium on Space Terahertz Technology, Proceedings Book. ; , s. 186-186
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Konferensbidrag (refereegranskat)abstract
- We present a practical low loss GaAs membrane integrated ortho mode transducer (OMT) at 424 GHz composed of two orthogonal open ended E-plane probes in a circular waveguide. The proposed structure is suitable for building compact dual polarisation receivers in the lower THz range (~100 GHz – 1 THz) and is readily integrated directly to the first receiver element, in this case a subharmonic GaAs Schottky diode mixer, without any additional penalty in terms of loss or manufacturability. A 3-port OMT split block aluminium module, with rectangular WR-2.2 waveguide interfaces for the separated V/H polarisations and 375 μm diameter circular waveguide for the common V/H port has been designed and fabricated. The simulated nominal response of the membrane OMT reaches X-pol levels below 20 dB over 10% bandwidth with a worst case insertion loss of 0.3 dB. The simulated inter probe leakage (isolation) and circular waveguide reflected X-pol levels where around 20 dB. For the particular OMT test additional E-plane probe transitions were integrated on-chip to be able to couple the separated V/H polarisations to the rectangular waveguide test ports. Measurements on two circular waveguide interconnected back to back OMT modules using VDI WM-570 (WR-2.2) VNAX frequency extenders, show X-pol and isolation levels below 10 dB and return loss levels below 15 dB including effects of standing waves. Translated to a single OMT transition this corresponds to a X-pol and isolation of about 15 dB. The loss of a single OMT probe transition including the membrane circuit and circular waveguide loss was estimated to about 0.2 dB. The results look promising and the next step will be to test the integrated OMT concept in a 424.7 GHz dual polarization receiver currently being pre-developed by Omnisys Instruments AB for the ISMAR instrument.
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| 26. |
- Sobis, Peter, 1978, et al.
(författare)
-
Ultra Low Noise 600/1200 GHz and 874 GHz GaAs Schottky Receivers for SWI and ISMAR
- 2016
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Ingår i: Twenty-seventh International Symposium on Space Terahertz Technology (ISSTT).
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Konferensbidrag (refereegranskat)abstract
- Omnisys Instruments is responsible for the 600/1200 GHz broadband front-end receivers and back-end spectrometer hardware for the Submillimeter Wave Instrument (SWI) part of the Jupiter Icy moons Explorer (JUICE) mission, and for the development of the dual-polarization 874 GHz spectrometer channels for the airborne icecloud imager instrument ISMAR. We will present our development of these highly integrated heterodyne receivers which are based on membrane integrated GaAs Schottky diode mixer and multiplier circuit technology, and InP HEMT MMIC LNA technology from Chalmers University of Technology. Preliminary results at room temperature on the 1200 GHz breadboard prototypes show on a typical DSB receiver noise below 3000 K in the 1030 GHz-1220 GHz frequency range with only 1-3 mW of LO power. For the 874 GHz receiver flight modules a record low double sideband noise of 2500 K was obtained with only 2.3 mW of LO pump power. Both the 1200 GHz and 874 GHz subharmonically pumped Schottky mixer designs have been based on the broadband SWI 600 GHz channel mixer design, which had a repeatable receiver noise performance below 1200K with less than 2 mW of pump power at room temperature. All together these results are setting new standards for critical receiver hardware operating at room temperature used in instrumentation for atmospheric research and remote sensing applications.
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