| 1. |
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| 2. |
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| 3. |
- Svedin, Jan, et al.
(author)
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An experimental 210 GHz radar system for 3D stand-off detection
- 2010
-
In: 35th International Conference on Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010. - 9781424466559
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Conference paper (peer-reviewed)abstract
- A 210 GHz radar system for studies of personscanning at stand-off distances is presented. The radar uses amechanically scanned RX front-end based on an antennaintegratedMMIC. The TX part is based on an HBV quintupler.Image data formation is made using the FMCW and SARprinciples.
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| 4. |
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| 5. |
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| 6. |
- Tavakoli Dastjerdi, Mohammad Hadi, 1984, et al.
(author)
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InGaAs/InAlAs/AlAs Heterostructure Barrier Varactors on Silicon Substrate
- 2011
-
In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 32:2, s. 140-142
-
Journal article (peer-reviewed)abstract
- We present the results of a study on epitaxial transferof InP-based heterostructure barrier varactor (HBV) materials onto a silicon substrate employing the low-temperature plasma activated bonding technique. The test diodes fabricated on the bonded samples exhibit symmetric electrical characteristics, over the temperature range of 25 ˚C–165 ˚C, and show no degradation compared to previously reported InP-based diodes. Moreover, the onset temperature for debonding, the effective barrier height extracted from the measured data, and the maximum voltage of the HBVs for a current density of 100 A/cm2 were extracted to be 260 ˚C, 0.56 eV, and 10.5 V, respectively.
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| 7. |
- Tavakoli Dastjerdi, Mohammad Hadi, 1984, et al.
(author)
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Transfer of InP-based HBV epitaxy onto borosilicate glass substrate by anodic bonding
- 2010
-
In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 46:14, s. 1013-1014
-
Journal article (peer-reviewed)abstract
- We present a new fabrication process for epitaxial transfer of InP-based heterostructure barrier varactor diodes, as high frequency varactor multipliers, onto low-dielectric borosilicate glass substrate, employing anodic bonding. The fabricated diodes on the new host substrate display symmetric electrical characteristics with only minor differences compared to those of the reference devices on the original InP substrate.
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| 8. |
- Wiberg, Andreas, 1978, et al.
(author)
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Characterization of uni-traveling carrier photodiodes for high-linearity and high-SNR applications
- 2010
-
In: Microwave and Optical Technology Letters. - : Wiley. - 1098-2760 .- 0895-2477. ; 52:6, s. 1460-1460
-
Journal article (peer-reviewed)abstract
- A typical uni-traveling carrier photodiode (UTC-PD) and a commercial PIN-PD are compared in the context of the analog performance at 10 GHz in a realistic noise environment.The behavior of the carrier-to-noise ratio (CNR), the linearity, represented by the third-order output intercept point (OIP3), and the spurious free dynamic range are studied as a function of photocurrent. We have found that the increment of the CNR is only minor because of excess noise of the amplifier, as an optical amplifier is used to reach high optical power. However, the OIP3 of the UTC-PD is substantially higher and increases with photocurrent, in contrast to the PIN-PD. Thus, even though the responsivity is lower, it is beneficial to use a UTC-PD to have superior dynamic range.
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| 9. |
- Amirmazlaghani, Mina, 1984, et al.
(author)
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Graphene-Si Schottky IR Detector
- 2013
-
In: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 49:7, s. 589-594
-
Journal article (peer-reviewed)abstract
- This paper reports on photodetection properties of graphene-Si schottky junction by measuring current-voltage characteristics under 1.55µm excitation laser. The measurements have been done on a junction fabricated by depositing mechanically exfoliated natural graphite on top of the pre-patterned silicon substrate. The electrical Schottky barrier height is estimated to be (0.44-0.47) eV with a minimum responsivity of 2.8mA/W corresponding to an internal quantum efficiency of 10% which is almost an order of magnitude larger than regular Schottky junctions. A possible explanation for the large quantum efficiency related to the 2-D nature of graphene is discussed. Large quantum efficiency, room temperature IR detection, ease of fabrication along with compatibility with Si devices can open a doorway for novel graphene-based photodetectors.
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| 10. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
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10 dB small-signal graphene FET amplifier
- 2012
-
In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 48:14, s. 861-863
-
Journal article (peer-reviewed)abstract
- Reported is the realisation of a graphene FET microwave amplifier operating at 1 GHz, exhibiting a small-signal power gain of 10 dB and a noise figure of 6.4 dB. The amplifier utilises a matching inductor on the gate yielding a return loss of 20 dB. The design is optimised for maximum gain and the optimum noise figure is extracted by noise modelling and predicted to be close to 1 dB for the intrinsic graphene FET at this frequency. The presented results complement existing graphene FET applications and are promising for future graphene microwave circuits.
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| 11. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
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Comparison of carrier scattering mechanisms in chemical vapor deposited graphene on fused silica and strontium titanite substrates
- 2014
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In: Graphene Week 2014.
-
Conference paper (peer-reviewed)abstract
- Graphene is explored for numerous applications for both electronics and photonics. These range from high frequency and low noise field effect transistors to conductive and highly transparent LED electrodes. To exploit the full potential of graphene, the remarkable intrinsic carrier transport properties and tunable, potentially low sheet resistance must be efficiently utilized. However, graphene carrier mobility is currently strongly degraded by extrinsic factors arising mainly from the dielectric environment, i.e. substrate and gate oxide. A proposed route to enhance transport is the use of a high-κ substrate to screen charged impurities at the graphene-substrate interface. In this paper, mobility and carrier concentration in CVD grown graphene films on fused silica (FS, κ=3.9) and strontium titanite (STO, κ=300) substrates are extracted from microwave measurements and compared to Hall data. To model the mobilities scattering by charged impurities (CI), substrate polar phonons (SPP) and resonant centers (RS) are included. Resonant scatterers dominates on strontium titanite and together with charged impurities on fused silica. While resonant scatterers are likely reduced by moving from wet to dry graphene transfer methods, the nominal mobility improvement by screening of charged impurities on high- κ strontium titanite would be masked at room temperature by increased surface phonon scattering.
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| 12. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
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Extraction of carrier transport properties in graphene from microwave measurements
- 2014
-
In: European Microwave Conference (EuMC), 2014 44th. ; , s. 359 - 362
-
Conference paper (peer-reviewed)abstract
- Carrier transport parameters of graphene grown by chemical vapor deposition (CVD) and graphene-metal contacts are extracted from microwave measurements in the frequency range 0.1–20 GHz using Corbino disks. It is shown that the charged impurities are effectively screened by the high permittivity of the SrTiO3 substrate. In the case of fused silica substrate the charged impurities are not completely screened and the mobility is limited either by the charged impurities or/and resonant scatterers depending on their relative concentration.
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| 13. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
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Microwave characterization of Ti/Au-graphene contacts
- 2013
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:17, s. 173111-
-
Journal article (peer-reviewed)abstract
- In this paper, we report on a microwave characterization of the interface between Ti/Au contacts and chemical vapor deposition graphene using structures of Corbino geometry, with primary focus on extracting and modeling the capacitance associated with the contact region. It is found that with the current contact resistivity, ρc∼10^−6 Ωcm2, the contact capacitance, on the order Cc∼1 μF/cm2, has a negligible effect on microwave transmission through the contact below ∼100 GHz. Finally, a parallel plate capacitance model for the contact is presented.
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| 14. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
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Noise Figure Characterization of a Subharmonic Graphene FET Mixer
- 2012
-
In: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781467310871
-
Conference paper (peer-reviewed)abstract
- We report on the first room temperature noise figure measurement of a graphene FET subharmonic resistive mixer in the interval fRF = 2-5 GHz. Due to an 8 nm thin Al2O3 gate dielectric it can operate with a conversion loss in the range 20-22 dB at only 0 dBm of local oscillator power. The measurement yields a noise figure close to the conversion loss, thus determining the noise to be thermal in origin, which is promising for cryogenic applications. The general route to lower noise figure is an improvement of the conversion loss.
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| 15. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Resistive Graphene FET Subharmonic Mixers: Noise and Linearity Assessment
- 2012
-
In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 4035-4042
-
Journal article (peer-reviewed)abstract
- We report on the first complete RF characterization of graphene field-effect transistor subharmonic resistive mixers in the frequency interval 2–5 GHz. The analysis includes conversion loss (CL), noise figure (NF), and intermodulation distortion. Due to an 8-nm thin Al2O3 gate dielectric, the devices operate at only 0 dBm of local oscillator (LO) power with an optimum measured CL in the range of 20–22 dB. The NF closely mimics the CL, thus determining the noise to be essentially thermal in origin, which is promising for cryogenic applications. The highest input third-order intercept point is measured to be 4.9 dBm at an LO power of 2 dBm.
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| 16. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
-
Towards Graphene Electrodes for High Performance Acoustic Resonators
- 2013
-
In: WOCSDICE. ; , s. 99-100
-
Conference paper (peer-reviewed)abstract
- The tunable FBAR is a promising building block for versatile microwave systems. Utilizing graphene electrodes promises higher tunability and frequency. Increased parasitic resistance may hamper the Q-factor of the resonator. This paper reports the initiated study of graphene and contacts at DC and microwave frequencies for optimization of these parameters leading to graphene FBARs.
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| 17. |
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| 18. |
- Barrientos, C. Z., et al.
(author)
-
Vertically illuminated TW-UTC photodiodes for terahertz generation
- 2010
-
In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 405-408
-
Conference paper (peer-reviewed)abstract
- More efficient continuous-wave photonic nearinfrared mixers as terahertz sources are investigated with the motivation to develop a universal photonic local oscillator for astronomical submillimeter/terahertz receiver systems. For this, our group has developed new concepts for vertically illuminated traveling-wave (TW) photomixers. The new device called TWUni- Travelling Carrier photodiodes (TW-UTC PD) was simulated, modeled and shall be optical/terahertz tested at the Electrical Engineering Department of the University of Chile, whereas device fabrication is performed at the MC2 cleanroom facility at Chalmers University of technology. We are reporting on first progresses in this direction.
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| 19. |
- Barrientos Z, C. M., et al.
(author)
-
Vertically illuminated TW-UTC photodiodes for terahertz generation
- 2012
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819491534 ; 8452
-
Conference paper (peer-reviewed)abstract
- More efficient and powerful continuous-wave photonic mixers as terahertz sources are motivated by the need of more versatile local oscillators for submillimeter/terahertz receiver systems. Uni-Travelling Carrier (UTC) photodiodes are very prospective candidates for reaching this objective, but so far only have been reported as lumped-elements or as edge-illuminated optical-waveguide travelling-wave (TW) devices. To overcome the associated power limitations of those implementations, we are developing a novel implementation of the UTC photodiodes which combines a traveling-wave photomixer with vertical velocity-matched illumination in a distributed structure. In this implementation called velocity-matched travelling-wave uni-travelling carrier photodiode, it is possible to obtain in-situ velocity matching of the beat-fringes of the two angled laser beams with the submm/THz-wave on the stripline. In this way, minimum frequency roll-off is achieved by tuning the angle between the two laser beams. A first design of these TW-UTC PDs from our Terahertz Photonics Laboratory at University of Chile has been micro-fabricated at the MC2 cleanroom facility at Chalmers Technical University.
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| 20. |
- Barrientos Z, C. M., et al.
(author)
-
Vertically illuminated TW-UTC photodiodes for terahertz generation
- 2010
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819482310 ; 7741
-
Conference paper (peer-reviewed)abstract
- More efficient continuous-wave photonic nearinfrared mixers as terahertz sources are investigated with the motivation to develop a universal photonic local oscillator for astronomical submillimeter/terahertz receiver systems. For this, we develop new concepts for vertically illuminated traveling-wave (TW) photomixers, TW Uni-Travelling Carrier (UTC) photodiodes. Device simulation/modeling and optical/terahertz testing is being done in the new terahertz photonics laboratory at the Electrical Engineering Department of the University of Chile, whereas device fabrication is performed at the MC2 cleanroom facility at Chalmers Technical University. We report on first progress in this direction.
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| 21. |
- Bevilacqua, Stella, 1981, et al.
(author)
-
Fast room temperature THz microbolometers
- 2012
-
In: 23rd International Symposium on Space Terahertz Technology.
-
Conference paper (peer-reviewed)abstract
- We will present experimental and theoretical investigation of room temperature high speed THz detectors based on thin YBa2Cu3O7 films. These films have TCR of 0.35%/K, and can sustain large bias current densities. With a resistivity of 100-200 µOhm×cm for a film thickness of 50nm, it is very straightforward to impedance match such bolometers with planar antennas. The responsivity is a function of the bolometer planar dimensions and the films thickness. The currently achieved responsivity is 30 V/W and Johnson noise limited NEP is 70pW/Hz^0.5. The bolometer bandwidth is limited by the antenna bandwidth and spans from microwaves to over a few THz. Experimenatl investigation is done from 100GHz to 2.5THz. The measured response time is 2ns. We will also present results of the bolometer performance as their dimensions reduce to sub-µm.
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| 22. |
- Bevilacqua, Stella, 1981, et al.
(author)
-
Investigation of MgB2 HEB mixer gain bandwidth
- 2011
-
In: International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz), 2011. - 2162-2027. - 9781457705083 ; , s. 1 - 2
-
Conference paper (peer-reviewed)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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| 23. |
- Bevilacqua, Stella, 1981, et al.
(author)
-
Low noise MgB2 terahertz hot-electron bolometer mixers
- 2012
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:3
-
Journal article (peer-reviewed)abstract
- We report on low noise terahertz bolometric mixers made of MgB2 superconducting thin films. For a 10-nm-thick MgB2 film, the lowest mixer noise temperature was 600 K at 600 GHz. For 30 to 10-nm-thick films, the mixer gain bandwidth is an inverse function of the film thickness, reaching 3.4 GHz for the 10-nm film. As the critical temperature of the film decreases, the gain bandwidth also decreases, indicating the importance of high quality thin films for large gain bandwidth mixers. The results indicate the prospect of achieving a mixer gain bandwidth as large as 10-8 GHz for 3 to 5-nm-thick MgB2 films.
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| 24. |
- Bevilacqua, Stella, 1981, et al.
(author)
-
MgB2 Hot Electron Bolometers for THz radio astronomy
- 2012
-
In: 23rd International Symposium on Space Terahertz Technology.
-
Conference paper (peer-reviewed)abstract
- We discuss Hot Electron Bolometer (HEB) THz mixers made of superconducting Magnesium Diboride (MgB2) films. The films of 30 nm, 15 nm and 10 nm thick were deposited on sapphire substrates. The MgB2 HEBs were patterned as a bridge at the feed point of a spiral antenna. The performance of the devices was investigated with respect to the gain bandwidth (GBW) and the noise temperature. The GBW was measured via mixing two signal sources (BWOs at 600 GHz). For the given films thicknesses, the GBW was measured to be 1.3 GHz, 2.3 GHz and 3.4 GHz, which is larger than for the NbN HEB mixers made of the same films thicknesses. Using the Y-factor technique a noise temperature of 800 K at 600 GHz local oscillator (LO) frequency was measured for mixers made of 10 nm MgB2 film. Besides the films thickness, the gain and the noise bandwidths are functions of the films critical temperature, Tc. For 10nm films, with Tc=15K, a noise bandwidth on the order of 8GHz was measured. From these measurements and from the material parameters a GBWof 8 GHz (noise bandwidth >10GHz) is expected for 3-5 nm MgB2 films.
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| 25. |
- Bevilacqua, Stella, 1981, et al.
(author)
-
Study of IF bandwidth of MgB2 phonon-cooled hot-electron bolometer mixers
- 2013
-
In: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 3:4, s. 409-415
-
Journal article (peer-reviewed)abstract
- A noise bandwidth (NBW) of 6-7 GHz was obtained for Hot-Electron Bolometer (HEB) mixers made of 10 nm MgB2 films. A systematic investigation of the (IF) gain bandwidth as a function of the MgB2 film thickness (30 nm, 15 nm and 10 nm) is also presented. The gain bandwidth (GBW) of 3.4 GHz was measured for a 10 nm film, corresponding to a mixer time constant of 47 ps. For 10 nm films a reduction of the GBW was observed with the reduction of the critical temperature (Tc). Experimental data were analyzed using the two-temperature model. From the theoretical analysis, the electron-phonon time (τe-ph), the phonon escape time (τesc) and the electron and phonon specific heats (ce, cph) were extrapolated giving the first model for HEB mixers of MgB2 films.
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| 26. |
- Bevilacqua, Stella, 1981, et al.
(author)
-
Submicrometer MgB2 hot electron bolometer mixers
- 2013
-
In: The 24th International Symposium on Space Terahertz Technology.
-
Conference paper (peer-reviewed)abstract
- Phonon-cooled hot electron bolometer mixers based on MgB2 film are promising candidates for THz radio astronomy at frequency above 1 THz. The short electron-phonon interaction time and the high critical temperature of the MgB2 (39 K in the bulk), compared to other intermetallic compounds, make it suitable for applications where wide IF bandwidth and low noise are needed. The currently achieved gain and noise bandwidths are 3.4 GHz and 7 GHz for HEBs fabricated in 10 nm MgB2 films. The noise temperature of 800 K was measured at 600 GHz local oscillator (LO) frequency using the Y-factor technique.MgB2 has been demonstrated to be sensitive to the oxygen as well as water, therefore it makes the fabrication of sub-µm HEBs very challenging. HEBs were fabricated using electron beam lithography in 10 nm MgB2 films with a bolometer area in the range of 0.09 and 0.25 µm2. We report the performance of the devices respect to the noise temperature at LO frequency up to 2.5 THz. Using the isothermal technique the LO power requirement was estimated respect to the bolometer area. Based on the material parameters obtained from the experiments, the two temperature model simulations showed a gain bandwidth as large as 8-10 GHz for thin MgB2 films.
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| 27. |
- Bryllert, Tomas, 1974, et al.
(author)
-
A 175 GHz HBV Frequency Quintupler With 60 mW Output Power
- 2012
-
In: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 22:2, s. 76-78
-
Journal article (peer-reviewed)abstract
- In this letter, we present a fixed tuned 175 GHz frequency quintupler with 60 mW output power. The peak efficiency is 6.3% and the 3 dB bandwidth is 8 GHz. The multiplier is based on a single Heterostructure Barrier Varactor (HBV) diode that is flip-chip soldered into a microtsrip matching circuit. All the matching is done “on-chip” and there is no need for dc bias. The multiplier block is very compact (25 x 9 x 8 mm^3).
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| 28. |
- Bryllert, Tomas, 1974, et al.
(author)
-
A broadband heterostructure barrier varactor tripler source
- 2010
-
In: 2010 IEEE MTT-S International Microwave Symposium (MTT). - 0149-645X. - 9781424460571 ; , s. 344-347
-
Conference paper (peer-reviewed)abstract
- We present the first demonstration of a broadband Heterostructure Barrier Varactor tripler, designed to cover a major part of the WR-8 waveguide band. The source comprises a waveguide housing, a six-barrier InP-HBV diode flip-chip mounted on an AlN microstrip filter circuit. The conversion loss 3-dB bandwidth was measured to 17 % at a center frequency of 112 GHz. The maximum output power was more than 15 mW for an input power of 300 mW. There are no mechanical tuners or DC-bias, which simplifies assembly and allows for ultra-compact design.
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| 29. |
- Bryllert, Tomas, 1974, et al.
(author)
-
A monolithic 280 GHz HBV frequency tripler
- 2010
-
In: IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide. - 9781424466573
-
Conference paper (peer-reviewed)abstract
- We present the design and measurements of a Heterostructure Barrier Varactor based frequency tripler for 280 GHz. The tripler is fabricated as a monolithic circuit on an InP substrate, including the input and output waveguide probes. Several circuit versions for input power levels between 100 mW and 1W have been designed. © 2010 IEEE.
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| 30. |
- Bryllert, Tomas, 1974, et al.
(author)
-
Integrated 200–240-GHz FMCW Radar Transceiver Module
- 2013
-
In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 61:10, s. 3808-3815
-
Journal article (peer-reviewed)abstract
- We present a 220-GHz homodyne transceiver module intended for frequency modulated continuous wave radar applications. The RF transceiver circuits are fabricated on 3 µm-thick GaAs membranes, and consist of a Schottky diode based transmitter frequency doubler that simultaneously operates as a sub-harmonic downconverting mixer. Two circuits are used in a balanced configuration to improve the noise performance. The output power is >3 dBm over a 40-GHz bandwidth (BW) centered at 220 GHz, and the receiver function is characterized by a typical mixer conversion loss of 16 dB. We present radar images at 4-m target distance with up to 60-dB dynamic range using a 30-µs chirp time, and near-BW-limited range resolution. The module is intended for applications in high-resolution real-time 3-D radar imaging, and the unit is therefore designed so that it can be assembled into 1-D or 2-D arrays.
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| 31. |
- Cherednichenko, Serguei, 1970, et al.
(author)
-
A room temperature bolometer for terahertz coherent and incoherent detection
- 2011
-
In: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 1:2, s. 395 - 402
-
Journal article (peer-reviewed)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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| 32. |
- Cherednichenko, Serguei, 1970, et al.
(author)
-
Wideband THz detectors based on YBCO thin films at 77K and at room temperature
- 2011
-
In: 6th ESA Workshop on Millimetre-Wave Technology and Applications.
-
Conference paper (peer-reviewed)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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| 33. |
- Dahlbäck, Robin, 1985, et al.
(author)
-
A 340 GHz CW non-linear imaging system
- 2010
-
In: Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010. - 9781424466559
-
Conference paper (peer-reviewed)abstract
- A CW sub-millimetre wave imaging system is presented. The system operates around 340GHz with a 6.5% relative bandwidth and uses a non-linear imaging algorithm.
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| 34. |
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| 35. |
- Dahlbäck, Robin, 1985, et al.
(author)
-
A System for THz Imaging of Low-Contrast Targets Using the Born Approximation
- 2012
-
In: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 2:3, s. 361-370
-
Journal article (peer-reviewed)abstract
- A THz imaging system, operating at 346 GHz and tailored for implementation of an imaging algorithm based on the Born approximation, is presented. The imaging algorithm provides focusing by compensating for the antenna footprint. This allows for using a more simple antenna system without optical focusing. Several aspects of implementing an imaging algorithm based on the Born approximation in THz imaging are discussed and key system properties are highlighted. The performance of the imaging algorithm is verified by imaging two simple dielectric targets. The results indicate that this approach provides a qualitative indication of the distribution of contrast in the samples complex permittivity and is a potential complement to existing imaging techniques.
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| 36. |
- Dahlbäck, Robin, 1985, et al.
(author)
-
A Waveguide Embedded 250 GHz Frequency-Tripler 2D Array
- 2014
-
In: Micro-and Millimetre Wave Technology and Techniques Workshop 2014, 25-27 November 2014.
-
Conference paper (peer-reviewed)abstract
- This work reports on a 248 GHz HBV (Heterostructure Barrier Varactors)-varactor quasi-optical multiplier array with a maximum output power of 18 mW and a corresponding conversion efficiency of 2 %. The module utilizes a mechanically compact and simple shim system, combining the large array power handling capability with the convenience of waveguide interfaced circuits. At the same time this approach offers excellent power and frequency scalability. The multiplier is based on a 12 by 6 element, 72 in total, planar 2D HBV varactor array. The diodes are fabricated on a three barrier InGaAs/InAlAs material system on InP as carrier substrate. Easch diode consist of two 20um^2 serially connected mesas, yielding a total of six barrier per diode. The HBV diodes are coupled to a uniform dipole array through which the power is coupled in and out. One HBV diode and the corresponding dipole make up a square unit cell with a side of 211 um. The chip measures 2,54 x 1,27 mm^2, fitting inside a standard WR10 waveguide. The complete module consists of three parts, the 2D HBV array, a combined output filter and output matching slab and an input matching slab. A rhombic aperture frequency selective surface is used as the uutput bandpass filter and the quartz filter substrate also serves as a matching slab for the output tone. On the input a piece of InP substrate is used to match the incoming pump signal to the diodes. The components are mounted inside two WR-10 waveguide shims, providing an easy assembly and a modular system. The current version of the multiplier module produces 18 mW at 248 GHz but a significant increase in output power and efficiency is expected with a new output matching network and more pump power. Recent measurement results will be presented together with a detailed discussion regarding the design, pointing out advantages and challenges compared to more traditional approaches to frequency multiplier design in the frequency range. Future improvements and challenges will also be covered.
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| 37. |
- Dahlbäck, Robin, 1985, et al.
(author)
-
A waveguide embedded 250 GHz quasi-optical frequency-tripler array
- 2014
-
In: 44th European Microwave Conference, EuMC 2014 - Held as Part of the 17th European Microwave Week, EuMW 2014; Fiera di RomaRome; Italy; 6 October 2014 through 9 October 2014. - 9782874870354 ; , s. 802-805
-
Conference paper (peer-reviewed)abstract
- A waveguide embedded 250 GHz HBV-varactor quasi-optical multiplier array is presented. The module utilizes a mechanically compact and simple shim system, combining the large array power handling capability with the convenience of waveguide interfaced circuits. At the same time this approach offers excellent power and frequency scalability. The current tripler prototype produces a non saturated output power of 8 mW at 248 GHz during initial measurements at medium pump power.
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| 38. |
- Dahlbäck, Robin, 1985, et al.
(author)
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Development of a waveguide integrated sub-millimetre wave spatially power combined HBV multiplier
- 2011
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In: 6th ESA Workshop on Millimetre-Wave Technology and Applications and 4th Global Symposium on Millimeter Waves.
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Conference paper (peer-reviewed)abstract
- The development of a sub-millimetre wave, spatially power combined, quasi optical HBV multiplier is presented. Emphasis is placed on key concepts of spatial power combining of frequency multipliers, as well as design challenges. The current state of the design as well as the final goal is further discussed.
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| 39. |
- Drakinskiy, Vladimir, 1977, et al.
(author)
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Development of planar schottky diodes
- 2011
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In: 22nd International Symposium on Space Terahertz Technology 2011, ISSTT 2011; Tucson, AZ; United States; 25 April 2011 through 28 April 2011. ; , s. 64-
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Conference paper (peer-reviewed)abstract
- We present the development of an air-bridged planar Schottky diode process at Chalmers University of Technology for use in submillimeter wave mixer and multiplier circuits. As a first step evaluation has been targeted for heterodyne receivers (atmosphere sounders) operation at 340 GHz. The aim is to develop a reliable and repeatable discrete Schottky diode process, with good electrical and mechanical characteristics, which also can be scaled to smaller anodes and extended to integrated diode circuits for THz frequencies. Air-bridged Schottky structures were demonstrated in the late 1980's as a reliable, high quality alternative to whisker contacted diodes. This approach gives a mechanically stable structure and still low parasitic capacitances. The Chalmers diode process is based on electron beam lithography, with a beam spot less than 5 nm, which allows for precise anode and airdridge formation. Hence, this process module can also be utilized for submicron size anodes and. terahertz monolithic integrated circuits (TMICs). Several batches with different shapes of anodes have been fabricated and evaluated with respect to DC/RF-performance. Repeatability of the diode's characteristics indicates good control of the diode fabrication process. We will present the main fabrication route, optimization and repeatability of the diodes as well as RF results from mixer and multiplier measurements up to 340 GHz.
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| 40. |
- Drakinskiy, Vladimir, 1977, et al.
(author)
-
Development of planar THz Schottky diodes
- 2011
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In: 6th ESA Workshop on Millimetre-Wave Technology and Applications.
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Conference paper (peer-reviewed)abstract
- We present the technological development of the air bridge planar Schottky diode process at Chalmers University of Technology for the use as submillimeter wave mixer and multiplier. Our first evaluation is targeted for the heterodyne receivers (i.e. atmosphere sounders) operation at 340 GHz. The aim is to develop a reliable and repeatable Schottky diode process, with good electrical and mechanical characteristics. In addition, the scalability of the diode geometry for diode integration in THz circuits is also taken into account in this development.
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| 41. |
- Drakinskiy, Vladimir, 1977, et al.
(author)
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Terahertz GaAs Schottky diode mixer and multiplier MIC’s based on e-beam technology
- 2013
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In: Conference Proceedings - International Conference on Indium Phosphide and Related Materials. - 1092-8669. - 9781467361316
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Conference paper (peer-reviewed)abstract
- We present the progress of the technological development of a full e-beam based monolithically integrated Schottky diode process applicable for sub-millimetre wave multipliers and mixers. Evaluation of the process has been done in a number of demonstrators showing state-of-the-art performance, including various multiplier circuits up to 200 GHz with a measured flange efficiency of above 35%, as well as heterodyne receiver front-end modules operating at 340 GHz and 557 GHz with a measured receiver DSB noise temperature of below 700 K and 1300 K respectively.
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| 42. |
- Fhager, Andreas, 1976, et al.
(author)
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Clinical Diagnostics and Treatment with Electromagnetic Fields
- 2010
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In: 4th European Conference on Antennas and Propagation, EuCAP 2010; Barcelona; Spain; 12 April 2010 through 16 April 2010. - 9788476534724 ; , s. C15P2-1
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Conference paper (peer-reviewed)abstract
- There is a need for novel diagnostic and treatment systems to overcome the limitations with todays modalities. Microwave and THz based system has the potential to become both sensitive and specific in several applications. In this paper we discuss several applications that are currently being developed at the Chalmers University of Technology.
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| 43. |
- Fhager, Andreas, 1976, et al.
(author)
-
Progress in clinical diagnostics and treatment with electromagnetic fields
- 2011
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In: Proceedings of the 5th European Conference on Antennas and Propagation, EUCAP 2011. Rome, 11-15 April 2011. - 9788882020743 ; , s. 1936-1937
-
Conference paper (peer-reviewed)abstract
- There is a need for novel diagnostic and treatment systems to overcome the limitations with todays modalities. Microwave and THz based system has the potential to become both sensitive and specific in several applications. In this paper we discuss several applications that are currently being developed at the Chalmers University of Technology.
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| 44. |
- Habibpour, Omid, 1979, et al.
(author)
-
A 30-GHz Integrated Subharmonic Mixer based on a Multichannel Graphene FET
- 2013
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In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 61:2, s. 841-847
-
Journal article (peer-reviewed)abstract
- A 30 GHz integrated subharmonic mixer based on a single graphene field effect transistor (G-FET) has been designed, fabricated and characterized. The mixer is realized in microstrip technology on a 250 um high resistivity silicon substrate. In order to enhance the current on-off ratio, the G-FET utilizes a channel consisting of an array of bow-tie structured graphene, yielding a current on-off ratio of 7. A conversion loss (CL) of 19 ± 1 dB over the frequency range of 24 to 31 GHz is obtained with an LO to RF isolation better than 20 dB at an LO power of 10 dBm. The overall minimum CL is 18 dB at 27 GHz. The mixer has a 3 GHz ±1-dB IF bandwidth, which is achieved with a fixed LO signal of 15 GHz. The mixer linearity is characterized and the highest third order intercept point is measured to be 12.8 dBm.
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| 45. |
- Habibpour, Omid, 1979, et al.
(author)
-
A Large Signal Graphene FET Model
- 2012
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In: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 59:4, s. 968-975
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Journal article (peer-reviewed)abstract
- We propose a semiempirical graphene field effect transistor (G-FET) model for analysis and design of G-FET based circuits. The model describes the current-voltage characteristic for a G-FET over a wide range of operating conditions. The gate bias dependence of the output power spectrum is studied and compared with simulated values. A good agreement between the simulated and the experimental power spectrum up to the 3rd harmonic is demonstrated which confirms the model validity. Moreover, S-parameter measurements essentially coincide with the results obtained from the simulation. The model contains a small set of fitting parameters which can straightforwardly be extracted from S-parameters and DC measurements. The developed extraction method gives a more accurate estimation of the drain and source contact resistances compared to other approaches. As a design example, we use a harmonic-balance load-pull approach to extract optimum embedding impedances for a subharmonic G-FET mixer.
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| 46. |
- Habibpour, Omid, 1979, et al.
(author)
-
A subharmonic graphene FET mixer
- 2012
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In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 33:1, s. 71-73
-
Journal article (peer-reviewed)abstract
- We demonstrate a subharmonic resistive graphene FET (G-FET) mixer utilizing the symmetrical channel resistance vs. gate voltage characteristic. A down-conversion loss of 24 dB is obtained with fRF=2 GHz, fLO=1.01 GHz and fIF=20 MHz in a 50 Ω impedance system. Unlike the conventional subharmonic resistive FET mixers, this type of mixer operates with only one transistor and does not need any balun at the LO port which makes it more compact.
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| 47. |
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| 48. |
- Habibpour, Omid, 1979, et al.
(author)
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Mobility Improvement and Microwave Characterization of a Graphene Field Effect Transistor With Silicon Nitride Gate Dielectrics
- 2011
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In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 32:7, s. 871-873
-
Journal article (peer-reviewed)abstract
- We report on the influence of a silicon nitride gate dielectric in graphene-based field-effect transistors (FETs). The silicon nitride is formed by a plasma enhanced chemical vapor deposition method. The process is based on a low density plasma at a high pressure (1 torr), which results in a low degradation of the graphene lattice during the top-gate formation process. Microwave measurements of the graphene FET show a cutoff frequency of 8.8 GHz for a gate length of 1.3 μm. A carrier mobility of 3800 cm2/V · s at room temperature was extracted from the dc characteristic.
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| 49. |
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| 50. |
- Hammar, Arvid, 1986, et al.
(author)
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A 340 GHz High Gaussicity Smooth Spline Horn Antenna for the STEAMR Instrument
- 2014
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In: IEEE Antennas and Propagation Society, AP-S International Symposium (Digest). - 1522-3965. - 9781479935383 ; , s. 649-650
-
Conference paper (peer-reviewed)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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