| 1. |
- Meyer, E., et al.
(författare)
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The state of the art in beyond 5G distributed massive multiple-input multiple-output communication system solutions
- 2022
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Ingår i: Open Research Europe. - : F1000 Research Ltd. - 2732-5121. ; 2
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Forskningsöversikt (refereegranskat)abstract
- Beyond fifth generation (5G) communication systems aim towards data rates in the tera bits per second range, with improved and flexible coverage options, introducing many new technological challenges in the fields of network architecture, signal pro- cessing, and radio frequency front-ends. One option is to move towards cell-free, or distributed massive Multiple-Input Multiple-Output (MIMO) network architectures and highly integrated front-end solutions. This paper presents an outlook on be- yond 5G distributed massive MIMO communication systems, the signal processing, characterisation and simulation challenges, and an overview of the state of the art in millimetre wave antennas and electronics.
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| 2. |
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| 3. |
- ÖZEN, MUSTAFA, 1984, et al.
(författare)
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Wideband and efficient watt-level SiGe BiCMOS switching mode power amplifier using continuous class-E modes theory
- 2014
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Ingår i: Digest of Papers - IEEE Radio Frequency Integrated Circuits Symposium. - 1529-2517. - 9781479938629 ; , s. 243-246
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Konferensbidrag (refereegranskat)abstract
- In this paper, a generic, wide-band switch mode power amplifier (SMPA) design approach is developed based on the continuous class-E modes theory. A watt level, 1.3-2.2 GHz SiGe BiCMOS class-E SMPA is realized for experimental verification. The prototype provides collector efficiencies higher than 70% and output power levels higher than 29 dBm across 1.3-2.2 GHz band, fully confirming the validity of the proposed design approach.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Fager, Hanna, et al.
(författare)
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Growth and Properties of Amorphous Hf1−x−yAlxSiyN (0≤x≤0.2; 0≤y≤0.2) and a-Hf0.6Al0.2Si0.2N/nc-HfN Multilayers by DC Reactive Magnetron Sputtering from a Single Hf0.60Al0.20Si0.20 Target
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Amorphous (a) and nanocrystalline (nc) Hf1−x−yAlxSiyN and multilayer a-Hf0.6Al0.2Si0.2N/nc-HfN films are grown on Si(001) at temperatures Ts = 100-450 ◦C using ultrahigh vacuum magnetically-unbalanced reactive magnetron sputtering from a single Hf0.60Al0.20Si0.20 target in a 5%-N2/Ar atmosphere at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf1−x−yAlxSiyN is controlled during growth by independently varying the ion energy (Ei) and the ion-to-metal flux ratio (Ji/JMe) incident at the film surface. With Ji/JMe = 8, the composition and nanostructure of the films ranges from x-ray amorphous with 1-x-y = 0.60 at Ei = 15 eV, to an amorphous matrix with encapsulated nanocrystals with 1-x-y = 0.66-0.84 at Ei = 25-35 eV, to nanocrystalline with 1-x-y = 0.96-1.00 at Ei = 45-65 eV. Varying Ji/JMe with Ei = 13 eV yields amorphous alloy films at Ts = 100 ◦C. a-Hf0.6Al0.6Si0.6N/nc-HfN multilayers with periods Λ = 2-20 nm exhibit enhanced fracture toughness compared to polycrystalline VN, TiN, and Ti0.5Al0.5N reference samples; multilayer hardness values increase monotonically from 20 GPa with Λ = 20 nm to 27 GPa with Λ = 2 nm.
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| 8. |
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| 9. |
- Wieckowski, A., et al.
(författare)
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Efficiency optimization for phase controlled multi-source microwave oven
- 2014
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Ingår i: International Journal of Applied Electromagnetics and Mechanics. - : IOS Press. - 1383-5416 .- 1875-8800. ; 44:2, s. 235-241
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Tidskriftsartikel (refereegranskat)abstract
- A solid-state microwave generators system is considered as an alternative to the magnetron, in order to inject electromagnetic energy into the cavity of a microwave oven for domestic use. Over current devices, the use of solid state technology allows one to control the frequency and phase of the electromagnetic field generated. Considering a simplified cavity with 2 solid state sources, the influence of the electrical parameters on maximum efficiency obtainable in the process of microwave heating is investigated. By varying the frequency, different values of optimal phases and different values of maximum efficiency are detected. Moreover, the procedure is repeated with varying the position of one source port and the influence of geometry on the system performance is evaluated. Our results demonstrate that the ability to control the electrical quantities of a microwave heating process makes it possible to obtain better results in terms of energy efficiency over the current poorly controllable systems.
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| 10. |
- ÖZEN, MUSTAFA, 1984, et al.
(författare)
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A Generalized Combiner Synthesis Technique for Class-E Outphasing Transmitters
- 2017
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Ingår i: IEEE Transactions on Circuits and Systems I: Regular Papers. - : Institute of Electrical and Electronics Engineers (IEEE). - 1549-8328 .- 1558-0806. ; 64:5, s. 1126-1139
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a generic combiner design technique is developed for class-E outphasing transmitters. The design procedure starts with calculation of the combiner network parameters that guarantee high efficiency switch mode operation of the PAs in each branch. Recently developed continuous class-E modes theory is then utilized to create an additional degree of freedom for calculation of the combiner network parameters. This additional degree of freedom along with duty cycle control provides an important possibility for achieving high average efficiency over a large bandwidth. A CMOS-GaN outphasing transmitter prototype is realized for experimental verification. The prototype provides drain efficiencies higher than 60% at 6 dB back-off across 750-1050 MHz band. Further, the peak output power remains nearly flat versus frequency, where the variation across the band is +/- 0.18 dB around 44 dBm.
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| 11. |
- ÖZEN, MUSTAFA, 1984, et al.
(författare)
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High efficiency RF pulse width modulation with tunable load network class-E PA
- 2011
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Ingår i: 2011 IEEE 12th Annual Wireless and Microwave Technology Conference, WAMICON 2011. - 9781612840819
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Konferensbidrag (refereegranskat)abstract
- In this paper, a 10 W peak power 2 GHz highly efficient RF pulse width modulation (RF-PWM) based transmitter is presented. RF-PWM signals are generated with a dedicated 65 nm CMOS modulator and subsequently amplified with a GaN Class-E power amplifier (PA). The modulator use extended drain MOS (EDMOS) high voltage transistors to provide the required voltage swing to drive the GaN used as a switch. The imaginary load impedance of the Class-E is electronically tunable and is implemented with in-house high breakdown voltage SiC varactors. The tunable imaginary load impedance enables optimization of the Class-E versus the duty cycle (pulse width). The peak efficiency is therefore preserved over a wide range of output power levels. The measured drain efficiency of the Class-E output stage is above 70% over a 6.5 dB output power dynamic range. The overall transmitter efficiency is above 60% for the same dynamic range.
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| 12. |
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| 13. |
- Chagtmi, Nadia, et al.
(författare)
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Augmented Hammerstein model for the calibration of six-port based dual band wireless receivers
- 2019
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Ingår i: International Journal of RF and Microwave Computer-Aided Engineering. - : Hindawi Limited. - 1096-4290 .- 1099-047X. ; 29:2
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Tidskriftsartikel (refereegranskat)abstract
- Two architectures of concurrent dual-band six-port-based receiver (SPR), which are modeled and calibrated using the augmented Hammerstein model (AHM) are proposed for the first time in this article. The receivers are based on six-port junctions with one or two local oscillators (LO). The proposed single step calibration algorithms achieve the recovery of the two in-phase (I1 and I2) and quadrature (Q1 and Q2) components of an RF signal with two frequency components (RF1 and RF2). Experimental validations have been performed to verify the performance of the proposed concurrent dual-band receivers and to test the efficiency of the AHM based calibration algorithms. As a performance metric, the Error Vector Magnitude (EVM) has been measured to compare the transmitted and recovered baseband signals and to evaluate the performance and efficiency of the proposed calibration algorithms for the two receiver topologies. The IQ data has been recovered with EVMs no higher than 2% for the two LOs based receiver excited with a QAM modulated dual-band RF signal. The single LO based receiver has been tested with a dual-band LTE signal and the recovered IQ data exhibited EVMs no higher than 4%.
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| 14. |
- Costa, Tatiana, et al.
(författare)
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CHARACTERIZATION OF A LITHIUM FORMATE EPR-DOSIMETRY SYSTEM FOR PROTON RADIATION THERAPY
- 2019
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Ingår i: Radiation Protection Dosimetry. - : OXFORD UNIV PRESS. - 0144-8420 .- 1742-3406. ; 186:1, s. 83-87
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Tidskriftsartikel (refereegranskat)abstract
- The specific aim for the characterization of the lithium formate dosimetry system is to determine response and stability in a proton beam. The long-term goal for this investigation is an audit system for proton therapy like the end-to-end dose determinations performed for radiotherapy with photons. For a 150-MeV proton beam, the dose response was found to be linear in the dose interval 0-8.8 Gy. The accuracy of dose reconstruction was controlled in a blind test, in which the dose of 6.63 Gy was measured in samples irradiated with a real dose of 6.70 Gy. The stability was determined by irradiations of sets of four dosimeters every week during 1 month and analyzed at the same day thereafter. The fitting of the fading curve was done with a second-order polynomial resulting in a 6.6% lower value compared to the reference after 31 d.
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| 15. |
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| 16. |
- Fager, Christian, 1974, et al.
(författare)
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A comprehensive analysis of IMD behavior in RF CMOS power amplifiers
- 2004
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Ingår i: IEEE Journal of Solid-State Circuits. - 0018-9200. ; 39:1, s. 24-34
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a comprehensive analysis of nonlinear intermodulation distortion (IMD) behavior in RF CMOS power amplifiers (PAs). Separate analyses are presented for small- and large-signal operation regimes. Especially, a new, simple, large-signal behavioral IMD analysis method is presented that allows the mechanisms dominant for IMD generation to be identified and their individual contributions to be studied.By combining these analyses, typical IMD versus input powercharacteristics of MOSFET PAs can be predicted and understood for different classes of operation.Various measurements made on a 950-MHz RF CMOS PA areused to demonstrate typical behavior and validate the proposed theory. Prediction of IMD using a standard CMOS transistor model is also evaluated and is shown to give good agreement with the measurements.
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| 17. |
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| 18. |
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| 19. |
- Fager Ferrari, Marcus, et al.
(författare)
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Evaluation of the Sialidase Inhibitor Oseltamivir in GNE-associated Thrombocytopenia
- 2021
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Ingår i: Research and practice in thrombosis and haemostasis. - 2475-0379. ; 5:S2, s. 644-645
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Konferensbidrag (refereegranskat)abstract
- Background: GNE encodes UDP-N-acetyl-glucosamine-2-epimerase/N-acetylmannosamine kinase, the rate limiting enzyme of sialic acid biosynthesis. Biallelic variants in GNE have recently been associated with severe isolated macrothrombocytopenia, attributed to an increased clearance of desialylated platelets. Interestingly, treatment with the sialidase inhibitor oseltamivir has been reported to increase platelet counts in conditions such as immune thrombocytopenia (ITP) and influenza. We present a case of a 17-year-old boy (the proband) with severe congenital macrothrombocytopenia (platelet counts < 10 x 109/L). Whole genome sequencing revealed two previously undescribed compound heterozygous variants in GNE (c.416_426del, p.Ile139Argfs*4 and c.1352G>A, p.Arg451Gln). The proband was otherwise healthy, with no signs of GNE myopathy. Aims: To investigate the consequences of the identified variants in GNE and evaluate the effect of oseltamivir in GNE-associated thrombocytopenia. Methods: Sialylation of platelets, granulocytes, lymphocytes and monocytes was determined by flow cytometry in the proband and healthy controls (n = 5), using Sambucus nigra lectin (SNA) and Maackia amurensis lectin II (MAL II). Platelet sialylation was reassessed in the proband following treatment with oseltamivir (75 mg twice daily, off-label use). Informed consent was obtained from all participants. The study was approved by the regional ethical committee. Results: Sialylation of platelets and leukocytes was markedly decreased in the proband compared with the healthy controls, consistent with a deleterious effect of the compound heterozygous variants in GNE (Figure 1). Platelet sialylation was persistently decreased after 18 days of treatment with oseltamivir, and no clinically significant elevation of the platelet counts could be observed (Figure 1, Figure 2).
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| 20. |
- Fager, Hanna, et al.
(författare)
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Growth of Hard Amorphous Ti-Al-Si-N Thin Films by Cathodic Arc Evaporation
- 2013
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 235:25, s. 376-385
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Tidskriftsartikel (refereegranskat)abstract
- Ti(1−x−y)AlxSiyNz (0.02≤x≤0.46, 0.02≤y≤0.28, and 1.08≤z≤1.29) thin films were grown on cemented carbide substrates in an industrial scale cathodic arc evaporation system using Ti-Al-Si compound cathodes in a N2 atmosphere. The microstructure of the as-deposited films changes from nanocrystalline to amorphous by addition of Al and Si to TiN. Upon incorporation of 12 at% Si and 18 at% Al, the films assume an x-ray amorphous state. Post-deposition anneals show that the films are thermally stable up to 900 ◦C. The films exhibit age hardening up to 1000 ◦C with an increase in hardness from 21.9 GPa for as-deposited films to 31.6 GPa at 1000 ◦C. At 1100 ◦C severe out-diffusion of Co and W from the substrate occur, and the films recrystallize into c-TiN and w-AlN.
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| 21. |
- Fager, Hanna, et al.
(författare)
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Hf-Al-Si-N multilayers deposited by reactive magnetron sputtering from a single Hf0.6Al0.2Si0.2 target using high-flux, low-energy modulated substrate bias : film growth and properties
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Hf1−x−yAlxSiyN (0≤x≤0.14, 0≤y≤0.13) single layers and multilayer films are grown on Si(001) at a substrate temperature Ts=250 °C using ultrahigh vacuum magnetically-unbalanced reactive magnetron sputtering from a single Hf0.6Al0.2Si0.2 target in a 5%-N2/Ar atmosphere at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf1−x−yAlxSiyN is controlled during growth by varying the ion energy (Ei) of the ions incident at the film surface, keeping the ion-to-metal flux ratio (Ji/JMe) constant at 8. By sequentially switching Ei between 10 and 40 eV, Hf0.77Al0.10Si0.13N/Hf0.78Al0.14Si0.08N multilayers with bilayer periods Λ = 2-20 nm are grown, in which the Si2p bonding state changes from predominantly Si-Si bonds for films grown at Ei = 10 eV, to mainly Si-N bonds at Ei = 40 eV. Multilayer hardness values increase monotonically from 20 GPa with Λ = 20 nm to 27 GPa with Λ = 2 nm, while multilayer fracture toughness increases with increasing Λ. Multilayers with Λ = 10 nm have the optimized property combination of being bothrelatively hard, H∼24 GPa, and fracture tough.
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| 22. |
- Fager, Hanna, et al.
(författare)
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Novel hard, tough HfAlSiN multilayers, defined by alternating Si bond structure, deposited using modulated high-flux, low-energy ion irradiation of the growing film
- 2015
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 33:5, s. 05E103-1-05E103-9
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Tidskriftsartikel (refereegranskat)abstract
- Hf1-x-yAlxSiyN (0 less than= x less than= 0.14, 0 less than= y less than= 0.12) single layer and multilayer films are grown on Si(001) at 250 degrees C using ultrahigh vacuum magnetically unbalanced reactive magnetron sputtering from a single Hf0.6Al0.2Si0.2 target in mixed 5%-N-2/Ar atmospheres at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf1-x-yAlxSiyN films are controlled by varying the energy Ei of the ions incident at the film growth surface while maintaining the ion-to-metal flux ratio constant at eight. Switching E-i between 10 and 40 eV allows the growth of Hf0.78Al0.10Si0.12N/Hf0.78Al0.14Si0.08N multilayers with similar layer compositions, but in which the Si bonding state changes from predominantly Si-Si/Si-Hf for films grown with E-i = 10 eV, to primarily Si-N with E-i = 40 eV. Multilayer hardness values, which vary inversely with bilayer period Lambda, range from 20 GPa with Lambda = 20 nm to 27 GPa with Lambda = 2 nm, while fracture toughness increases directly with Lambda. Multilayers with Lambda = 10nm combine relatively high hardness, H similar to 24GPa, with good fracture toughness. (C) 2015 American Vacuum Society.
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| 23. |
- Fager, Hanna, et al.
(författare)
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Thermal stability and mechanical properties of amorphous arc evaporated Ti-B-Si-N and Ti-B-Si-Al-N coatings grown by cathodic arc evaporation from TiB2, Ti33Al67, and Ti85Si15 cathodes
- 2014
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 32:6, s. 061508-
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Tidskriftsartikel (refereegranskat)abstract
- Ti-B-Al-N, Ti-B-Si-N, and Ti-B-Si-Al-N coatings were grown on cemented carbide substrates in an industrial scale cathodic arc evaporation system using Ti33Al67, Ti85Si15, and TiB2 cathodes in a reactiveN2 atmosphere. The microstructure of the as-deposited coatings changes from nanocrystalline to amorphous with addition of (B+Si+Al), or high amounts of (B+Si) to TiN. In the as-deposited state, the 4 μm-thick amorphous coatings are dense and homogenous, besides slight compositional modulation with Ti-rich layers induced by rotation of the substrate holder fixture during deposition, and have unusually few macroparticles. Annealing at temperatures ranging from 700 °C to 1100 °C results in that the coatings crystallize by clustering of TiN grains. The hardness of as-deposited amorphous coatings is 17-18 GPa, and increases to 21 GPa following annealing at 800 °C. At annealing temperatures of 1000 °C and above the hardness decreases due to inter-diffusion of Co from the substrate to the coating.
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| 24. |
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| 25. |
- Gleich, Stephan, et al.
(författare)
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Modifying the nanostructure and the mechanical properties of Mo2BC hard coatings : Influence of substrate temperature during magnetron sputtering
- 2018
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Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 142, s. 203-211
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Tidskriftsartikel (refereegranskat)abstract
- A reduction in synthesis temperature is favorable for hard coatings, which are designed for industrial applications, as manufacturing costs can be saved and technologically relevant substrate materials are often temperature-sensitive. In this study, we analyzed Mo2BC hard coatings deposited by direct current magnetron sputtering at different substrate temperatures, ranging from 380 degrees C to 630 degrees C. Transmission electron microscopy investigations revealed that a dense structure of columnar grains, which formed at a substrate temperature of 630 degrees C, continuously diminishes with decreasing substrate temperature. It almost vanishes in the coating deposited at 380 degrees C, which shows nanocrystals of similar to 1 nm in diameter embedded in an amorphous matrix. Moreover, Argon from the deposition process is incorporated in the film and its amount increases with decreasing substrate temperature. Nanoindentation experiments provided evidence that hardness and Young's modulus are modified by the nanostructure of the analyzed Mo2BC coatings. A substrate temperature rise from 380 degrees C to 630 degrees C resulted in an increase in hardness (21 GPa to 28 GPa) and Young's modulus (259 GPa to 462 GPa). We conclude that the substrate temperature determines the nanostructure and the associated changes in bond strength and stiffness and thus, influences hardness and Young's modulus of the coatings.
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| 26. |
- Lampu, Vesa, et al.
(författare)
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Multilevel Outphasing With Over-the-Air Combining in Large Antenna Arrays
- 2023
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 71:12, s. 7347-7362
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Tidskriftsartikel (refereegranskat)abstract
- This article investigates the feasibility of combinerless multilevel outphasing transmitter as a potential architecture for large millimeter-wave (mmWave) phased arrays. We consider two distinct ways of distributing the component signals to the antennas and develop a model for the received signal at each radiated spatial direction from a phased array. Based on the received signal model, we derive expressions for the signal-to-distortion ratio as well as total power experienced at each spatial direction. Furthermore, antenna branch mismatches, overload distortion and quantization are considered, and an analytical model for the signal-to-distortion ratio at the intended receiver is derived. We additionally establish a model for comparing the achievable energy efficiency to those of the relevant reference methods. Extensive numerical experiments are carried out to verify the analytical works, and to assess the commonly used metrics of error vector magnitude (EVM) and total radiated power adjacent channel leakage ratio (TRP-ACLR). It is shown that the combinerless architecture is a valid option for mmWave phased arrays, demonstrating favorable EVM results and TRP-ACLR beyond the 28 dBc limit imposed by the 3GPP, even in the presence of the considered distortions. The conducted energy efficiency assessment shows that efficiency of the reference methods can be exceeded with sufficient amount of outphasing levels. The considered architecture is thus an interesting alternative for addressing the linearity vs. energy-efficiency challenge in mmWave phased-array systems.
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| 27. |
- Malmqvist, Robert, et al.
(författare)
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A W-Band Single-Chip Receiver in a 60 nm GaN-on-Silicon Foundry Process
- 2021
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Ingår i: EuMIC 2021 - 2021 16th European Microwave Integrated Circuits Conference. ; , s. 51-54
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Konferensbidrag (refereegranskat)abstract
- This paper presents a compact W-band heterodyne receiver MMIC realised in a 60 nm GaN-on-Si foundry process. The single-chip receiver consists of an LNA with a measured NF of 4.4-5.5 dB at 90-95 GHz and a resistive down-conversion mixer with a frequency doubler for the multiplication of the LO signal. The measured receiver conversion gain is 0-7.4 dB/0-6.4 dB at 75-91 GHz when the LO/2 power is 20.5 dBm (IF=5 GHz/2 GHz). The measured receiver 1 dB compression point is found to occur at an input power level of -12 dBm and -9 dBm at 80 GHz and 91 GHz, respectively (IF=2GHz). To the best of our knowledge, this single-chip receiver achieves the smallest size (4 mm2), widest RF and IF bandwidths and highest linearity among reported GaN single-chip receivers in this frequency range. The receiver noise figure can be reduced by using an alternative GaN-on-Si LNA design with a measured average NF of 3.6-4.0 dB at 75-95 GHz and a measured maximum input 1 dB compression point of -3 dBm at 95 GHz.
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| 28. |
- Malmqvist, Robert, et al.
(författare)
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E/W-Band CPW-based Amplifier MMICs Fabricated in a 60 nm GaN-on-Silicon Foundry Process
- 2021
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Ingår i: EuMIC 2020 - 2020 15th European Microwave Integrated Circuits Conference. ; , s. 137-140
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Konferensbidrag (refereegranskat)abstract
- This paper presents an experimental evaluation of two co-planar waveguide (CPW) based E/W-band amplifier MMICs realised in a 60 nm GaN-on-Si foundry process. A one-stage amplifier and a two-stage amplifier realised in this process have a measured maximum gain of 8 dB and 16 dB at 73-74 GHz, respectively. The two amplifiers have a measured gain of 3 dB and 7 dB at 93 GHz when the drain voltage (Vd) is 10 V and the drain current (Id) is 15 mA per stage. The two-stage amplifier has a measured noise figure (NF) of 2.7-3.8 dB and 2.9-4.1 dB at 90-95 GHz when the Id is 10 mA and Vd is 5 V and 10 V, respectively. The measured NF of this amplifier is equal to 4-6 dB at 92-95 GHz when an Id of 10-20 mA is used in each stage with same drain bias.
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| 29. |
- Pamoin-Gonzalez, M, 1900, et al.
(författare)
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Outphasing combiner synthesis from transistor load pull data
- 2015
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Ingår i: 2015 IEEE MTT-S International Microwave Symposium, IMS 2015. - 9781479982752
-
Konferensbidrag (refereegranskat)abstract
- A novel load-pull based outphasing combiner synthesis approach is developed. The design technique is based on the derivation of combiner network parameters in terms of the optimal load impedances at the peak power level and a pre-defined back-off level. The combiner is then synthesized using transmission lines or lumped element networks. The design technique is verified in a 30 W GaN HEMT outphasing transmitter demonstrator. The prototype presents a power-added efficiency of 50% at 2.1 GHz with 9 dB peak-to-average power ratio (PAPR) 20 MHz LTE signals. The related measured adjacent channel leakage ratio is -51 dBc using a low complexity digital pre-distortion linearization algorithm.
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| 30. |
- Prasad, Ankur, et al.
(författare)
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Symmetrical large-signal modeling of microwave switch FETs
- 2014
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Ingår i: IEEE transactions on microwave theory and techniques. - 0018-9480 .- 1557-9670. ; 62:8, s. 1590-1598
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new symmetrical field-effect transistor (FET) model suitable for microwave switches. The model takes advantage of the inherent symmetry of typical switch devices, justifying a new small-signal model where all intrinsic model parameters can be mirrored between the positive and negative drain-source bias regions. This small-signal model is utilized in a new and simplified approach to large-signal modeling of these type of devices. It is shown that the proposed large-signal model only needs a single charge expression to model all intrinsic capacitances. For validation of the proposed model, small-signal measurements from 100 MHz to 50 GHz and large-signal measurements at 600 MHz and 16 GHz, are carried out on a GaAs pHEMT. Good agreement between the model and the measurements is observed under both small- and large-signal conditions with particularly accurate prediction of higher harmonic content. The reduced measurement requirements and complexity of the symmetrical model demonstrates its advantages. Further, supporting operation in the negative drain-source voltage region, the model is robust and applicable to a variety of circuits, e.g., switches, resistive mixers, oscillators, etc.
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| 31. |
- Prasad, Ankur, 1987, et al.
(författare)
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Symmetrical modeling of GaN HEMTS
- 2014
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Ingår i: Technical Digest - IEEE Compound Semiconductor Integrated Circuit Symposium, CSIC. - 1550-8781. - 9781479936229
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Konferensbidrag (refereegranskat)abstract
- This paper presents a symmetrical small signal model for GaN HEMTs valid for both positive and negative Vds. The model takes advantage of the intrinsic symmetry of the devices typically used for switches. The parameters of the model are extracted using a new symmetrical optimization based extraction method, optimizing simultaneously for both positive and negative drain-source bias points. This ensures a symmetrical small signal model with lower modeling error. The small signal model can be further used to simplify the development of a large-signal model. The small signal model is validated with measured S- parameters of a commercial GaN HEMT.
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| 32. |
- Rasilainen, Kimmo, 1987, et al.
(författare)
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Thermal analysis of GaN/SiC-on-Si assemblies: Effect of bump pitch and thickness of SiC Layer
- 2020
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Ingår i: 2020 26th International Workshop on Thermal Investigations of ICs and Systems, THERMINIC 2020 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- The ever-increasing requirements for high device performance and compact size drive the communications industry to lookfor new materials, technologies, and integration concepts. This simulation-based study investigates the thermal properties of a compact, heterogeneously integrated gallium nitride on silicon carbide (GaN-on-SiC) and silicon (Si) assembly. Thermal simulations and parametric studies are used to determine how the heat spreading and temperature levels in the lateral and vertical directions are affected by the thickness of the SiC layer and the distribution of the thermal interconnects. Results show that a SiC layer thinned down to 100 μm shows more pronounced differences in its thermal characteristics compared to thicker ones, especially in terms of its backside heating. Aspects related to practical implementations are also considered.
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| 33. |
- Rasilainen, Kimmo, 1987, et al.
(författare)
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Thermal characteristics of vertically-integrated GaN/SiC-on-Si assemblies: A comparative study
- 2019
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. ; 2019-May, s. 1405-1412
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Konferensbidrag (refereegranskat)abstract
- This work investigates the thermal characteristics of a vertically-stacked, heterogeneously-integrated assembly intended for millimetre-wave communications systems. The assembly combines materials that enable the generation of high output power as well as high degree of integration for improved performance, and vertical integration of the different materials enables a compact footprint. Suitability of thermal solutions based on metal pillars, solder balls, and ball grid arrays (BGA) is investigated. Both ideal, fully-populated arrays of interconnects and partially-filled ones more suitable for practical implementations are considered using theoretical calculations and numerical thermal simulations. With the assumptions used, simulation results show that arrays of Cu pillars and large solder bumps with a pitch of 150 μm provide good thermal performance also with a simplified grid and reduced number of interconnects. In the current geometry, the most important locations for the pillars and bumps are near the heat sources, and the use of a rim of interconnects around the assembly perimeter can reduce the temperature by several degrees - even when the majority of the other interconnects is focused beneath the heat sources.
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| 34. |
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| 35. |
- Skärberg, F., et al.
(författare)
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Convolutional neural networks for segmentation of FIB-SEM nanotomography data from porous polymer films for controlled drug release
- 2021
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Ingår i: Journal of Microscopy. - : John Wiley and Sons Inc. - 0022-2720 .- 1365-2818. ; 283:1, s. 51-63
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Tidskriftsartikel (refereegranskat)abstract
- Phase-separated polymer films are commonly used as coatings around pharmaceutical oral dosage forms (tablets or pellets) to facilitate controlled drug release. A typical choice is to use ethyl cellulose and hydroxypropyl cellulose (EC/HPC) polymer blends. When an EC/HPC film is in contact with water, the leaching out of the water-soluble HPC phase produces an EC film with a porous network through which the drug is transported. The drug release can be tailored by controlling the structure of this porous network. Imaging and characterization of such EC porous films facilitates understanding of how to control and tailor film formation and ultimately drug release. Combined focused ion beam and scanning electron microscope (FIB-SEM) tomography is a well-established technique for high-resolution imaging, and suitable for this application. However, for segmenting image data, in this case to correctly identify the porous network, FIB-SEM is a challenging technique to work with. In this work, we implement convolutional neural networks for segmentation of FIB-SEM image data. The data are acquired from three EC porous films where the HPC phases have been leached out. The three data sets have varying porosities in a range of interest for controlled drug release applications. We demonstrate very good agreement with manual segmentations. In particular, we demonstrate an improvement in comparison to previous work on the same data sets that utilized a random forest classifier trained on Gaussian scale-space features. Finally, we facilitate further development of FIB-SEM segmentation methods by making the data and software used open access.
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| 36. |
- Wang, Hua, et al.
(författare)
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Millimeter-Wave Power Amplifier Integrated Circuits for High Dynamic Range Signals
- 2021
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Ingår i: IEEE Journal of Microwaves. - 2692-8388. ; 1:1, s. 299-316
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Tidskriftsartikel (refereegranskat)abstract
- The next-generation 5G and beyond-5G wireless systems have stimulated a substantial growth in research, development, and deployment of mm-Wave electronic systems and antenna arrays at various scales. It is also envisioned that large dynamic range modulation signals with high spectral efficiency will be ubiquitously employed in future communication and sensing systems. As the interface between the antennas and transceiver electronics, power amplifiers (PAs) typically govern the output power, energy efficiency, and reliability of the entire wireless systems. However, the wide use of high dynamic range signals at mm-Wave carrier frequencies substantially complicates the design of PAs and demands an ultimate balance of energy efficiency and linearity as well as other PA performances. In this review paper, we will first introduce the system-level requirements and design challenges on mm-Waves PAs due to high dynamic range signals. We will review advanced active load modulation architectures for mm-Wave PAs and power devices. We will then introduce recent advances in mm-Wave PA technologies and innovations with several design examples. Special design considerations on mm-Wave PAs for phased array MIMOs and high mm-Wave frequencies will be outlined. We will also share our vision on future technology trends and innovation opportunities.
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| 37. |
- ÖZEN, MUSTAFA, 1984, et al.
(författare)
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High-Efficiency RF Pulsewidth Modulation of Class-E Power Amplifiers
- 2011
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 59:11, s. 2931-2942
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A new switch-mode power-amplifier (SMPA) topology particularly suitable for energy efficient amplification of RF pulsewidth modulation (RF-PWM) signals is derived. It is analytically shown that high efficiency can be maintained over a wide power dynamic range if the imaginary part of the Class-E load impedance is varied along with the duty cycle (pulsewidth). Using the theory developed, an explicit design procedure is presented that allows practical realization of the proposed topology from the circuit and component specifications. Following the design procedure, and using in-house (Chalmers University, Goteborg, Sweden) SiC varactor diodes to implement the tunable imaginary load impedance, a 2-GHz 10-W peak output power GaN HEMT circuit demonstrator is realized. RF-PWM input signals for characterization of the prototype power amplifier (PA) is generated with a dedicated 65-nm CMOS modulator. The measurements show that a drain efficiency > 70% can be obtained over an 6.5-dB dynamic range, which verifies the theory presented and demonstrates the feasibility of the proposed PA topology.
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