| 1. |
- Banik, Biddut Kumar, 1978, et al.
(författare)
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Catadioptric Dielectric Lens for Imaging Applications
- 2008
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Ingår i: Proceedings of 33rd International Conference on Infrared, Millimeter, and Terahertz Waves. - 9781424421190 ; , s. 1 - 2
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Konferensbidrag (refereegranskat)abstract
- The design and characterization results of a novel catadioptric dielectric lens are presented. Although being electrically small, the lens provides a focus in the close vicinity which makes it suitable to be used in microwave and terahertz systems. Several lenses of different dielectric materials and dimensions have been fabricated. A simple backscattering measurement method has been implemented in order to determine the focusing property of the lens.
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| 2. |
- Banik, Biddut Kumar, 1978, et al.
(författare)
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Millimeter Wave Characterization of a Catadioptric Lens for Imaging Applications
- 2009
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Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 19:11, s. 680-682
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Tidskriftsartikel (refereegranskat)abstract
- Characterization of a catadioptric dielectric lens-horn configuration for short-range sensing and imaging is presented. The focusing property is investigated both numerically and experimentally at 108 GHz. The lens-horn provides a focal spot of ~ 0.9λ at a distance of ~ 4.5λ. An imaging example employing the lens in a CW imaging setup is presented. A test pattern was imaged and a marked improvement in image resolution was observed. With the aid of the lens, features close to the wavelength are resolved, which are absent or indistinguishable otherwise.
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| 3. |
- Hanning, Johanna, 1981, et al.
(författare)
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A Broadband THz Waveguide-to-suspended Stripline Loop-probe Transition
- 2017
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781509063604 ; , s. 1091-1094
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Konferensbidrag (refereegranskat)abstract
- We present a novel waveguide-to-suspended stripline loop-probe transition operating over the entire WR-1.0 waveguide band. The loop probe is designed for broadband response with simulated RL > 15 dB, and has an integrated DC return path, which can also be extended for biasing. The measured insertion loss for a back-to-back configuration is 1 – 2 dB in almost the entire frequency range of 750 – 1100 GHz.
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| 4. |
- Hanning, Johanna, 1981, et al.
(författare)
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HBV MMIC frequency tripler and quintupler for high power THz applications
- 2011
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Ingår i: Millimetre Wave Days Proceedings,The 6th ESA Workshop on Millimetre-Wave Technology and Applications AND The 4th Global Symposium on Millimeter Waves GSMM2011, May 23rd – May 25th, 2011, MilliLab, Espoo, Finland.
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Konferensbidrag (refereegranskat)abstract
- We present the development status of two different HBV frequency multipliers, with x3 and x5 multiplication for a 282 GHz and 470 GHz output respectively. The multipliers are designed for high power operation and fabricated in an InP monolithic process. Preliminary measurements of the x3 multiplier demonstrate 10 % conversion efficiency at 296 GHz.
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| 5. |
- Shang, Xiaobang, et al.
(författare)
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Interlaboratory investigation of on-wafer S-parameter measurements from 110 GHz to 1.1 THz
- 2023
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Ingår i: 53rd European Microwave Conference. - 9782874870729 ; , s. 624-627
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Konferensbidrag (refereegranskat)abstract
- This paper presents an interlaboratory comparison of on-wafer S-parameter measurements of coplanar waveguide (CPW) devices in the frequency range of 110 GHz to 1.1 THz. The comparison was conducted using bespoke calibration standards and verification devices fabricated from high resistivity Silicon. In this study, nine well-established measurement laboratories were involved, and the measurements were performed at different laboratories using different equipment but the same calibration method, i.e. multiline TRL (mTRL). The results show reasonable consistency across a wide frequency range. Observations on the results are provided, along with discussions of factors that may impact interlaboratory reproducibility at such high frequencies.
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| 6. |
- Sobis, Peter, 1978, et al.
(författare)
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Towards a THz Sideband Separating Subharmonic Schottky Mixer
- 2008
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Ingår i: GigaHertz SympoSium 2008, p. 46.
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Konferensbidrag (refereegranskat)abstract
- GaAs Schottky mixers with state of the art planar submicron diodes are used for THz-detection up to 3 THz today [1]. GaAs Schottky diodes can operate in room temperature which makes them good candidates for space applications and an interesting low cost alternative to low noise cryogenic SIS and HEB technologies. The main advantage of a sideband separation scheme besides that the lower and upper sidebands are indeed separated, is that the IF bandwidth is increased by a factor of two. Moreover, there is no need for image rejection filters on the RF input, which can be bulky and increase the weight and cost of the overall receiver system. Sideband separation mixers have been implemented at THz frequencies before [2], however up to this point they have never been tried with Schottky diodes in a subharmonic mixer configuration. We will present the current status of the development of a novel sideband separating subharmonic reciever topology operating at 340 GHz, see Fig1. The design of a subharmonic mixer and the LO and RF waveguide hybrids will be presented followed by an account of measured results of the individual components.
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| 7. |
- Tang, Aik-Yean, 1980, et al.
(författare)
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Steady-State and Transient Thermal Analysis of High-Power Planar Schottky Diodes
- 2011
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Ingår i: 22nd International Symposium on Space Terahertz Technology.
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Konferensbidrag (refereegranskat)abstract
- Recent progress in power amplifier technology has made it possible to construct W-band sources which are capable of producing powers in the 1-Watt range. These sources are required in order to build multiplier based local oscillator chains in the frequency range of 2-3 THz. However, it becomes imperative that the multipliers, in particular the initial stage multipliers, be able to withstand the large input power without degrading efficiency or burning out.In this work, we present a systematic study of the steady-state as well as transient thermal behavior of doubler and tripler chips in the 200 GHz range that have been developed at JPL. The Ansys Structural Mechanic software tool has been used to simulate thermal performance of the planar Schottky diodes using a finite-element approach. Experimental verification of the simulation tool is achieved by performing infra-red (IR) thermal imaging on a multiplier chip mounted in a half open waveguide block. The simulation tool is used to explore the various parameters (chip topology, novel materials, cryogenic temperatures etc) and it is concluded that a careful thermal design of the first stage multiplier is necessary in order to produce robust LO chains in the 2-3 THz range. The thermal effects on the multiplier performances will also be discussed.
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| 8. |
- Asad, Muhammad, 1986, et al.
(författare)
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Enhanced high-frequency performance of top-gated graphene FETs due to substrate-induced improvements in charge carrier saturation velocity
- 2021
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Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 68:2, s. 899-902
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Tidskriftsartikel (refereegranskat)abstract
- High-frequency performance of top-gated graphene field-effect transistors (GFETs) depends to a large extent on the saturation velocity of the charge car-riers, a velocity limited by inelastic scattering by surface optical phonons from the dielectrics surrounding the chan-nel. In this work, we show that by simply changing the graphene channel surrounding dielectric with a material having higher optical phonon energy, one could improve the transit frequency and maximum frequency of oscillation of GFETs. We fabricated GFETs on conventional SiO2/Si substrates by adding a thin Al2O3 interfacial buffer layer on top of SiO2/Si substrates, a material with about 30% higher optical phonon energy than that of SiO2, and compared performance with that of GFETs fabricated without adding the interfacial layer. From S-parameter measurements, a transit frequency and a maximum frequency of oscillation of 43 GHz and 46 GHz, respectively, were obtained for GFETs on Al2O3 with 0.5 µm gate length. These values are approximately 30% higher than those for state-of-the-art GFETs of the same gate length on SiO2. For relating the improvement of GFET high-frequency performance to improvements in the charge carrier saturation velocity, we used standard methods to extract the charge carrier veloc-ity from the channel transit time. A comparison between two sets of GFETs with and without the interfacial Al2O3 layer showed that the charge carrier saturation velocity had increased to 2·10^7 cm/s from 1.5·10^7 cm/s.
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| 9. |
- Banik, Biddut Kumar, 1978, et al.
(författare)
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Microwave S-parameter Characterization of an Antenna-Coupled Catadioptric Lens
- 2009
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 8, s. 1299-1301
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Tidskriftsartikel (refereegranskat)abstract
- The focusing property of a bow-tie antenna coupled catadioptric lens is studied experimentally using a vector measurement setup. The results show that the lens-antenna provides short-range focusing. Furthermore, the return loss of the lens-antenna was determined numerically and confirmed experimentally from 1 GHz to 10 GHz. The lens-antenna provides 60% bandwidth (VSWR ≤ 2) centered at 6 GHz. Finally, the lens-antenna was employed to detect and locate buried objects and results are presented.
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| 10. |
- Bonmann, Marlene, 1988, et al.
(författare)
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Effect of oxide traps on channel transport characteristics in graphene field effect transistors
- 2017
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Ingår i: Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures. - : American Vacuum Society. - 2166-2754 .- 2166-2746. ; 35:1, s. 01A115-
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Tidskriftsartikel (refereegranskat)abstract
- A semiempirical model describing the influence of interface states on characteristics of gatecapacitance and drain resistance versus gate voltage of top gated graphene field effect transistors ispresented. By fitting our model to measurements of capacitance–voltage characteristics and relatingthe applied gate voltage to the Fermi level position, the interface state density is found. Knowing theinterface state density allows us to fit our model to measured drain resistance–gate voltagecharacteristics. The extracted values of mobility and residual charge carrier concentration arecompared with corresponding results from a commonly accepted model which neglects the effect ofinterface states. The authors show that mobility and residual charge carrier concentration differsignificantly, if interface states are neglected. Furthermore, our approach allows us to investigate indetail how uncertainties in material parameters like the Fermi velocity and contact resistanceinfluence the extracted values of interface state density, mobility, and residual charge carrierconcentration.
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