| 1. |
- Abbasi, Morteza, 1982, et al.
(författare)
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Single-Chip 220-GHz Active Heterodyne Receiver and Transmitter MMICs With On-Chip Integrated Antenna
- 2011
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 59:2, s. 466-478
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the design and characterization of single-chip 220-GHz heterodyne receiver (RX) and transmitter (TX) monolithic microwave integrated circuits (MMICs) with integrated antennas fabricated in 0.1-mu m GaAs metamorphic high electron-mobility transistor technology. The MMIC receiver consists of a modified square-slot antenna, a three-stage low-noise amplifier, and a sub-harmonically pumped resistive mixer with on-chip local oscillator frequency multiplication chain. The transmitter chip is the dual of the receiver chip by inverting the direction of the RF amplifier. The chips are mounted on 5-mm silicon lenses in order to interface the antenna to the free space and are packaged into two separate modules. The double-sideband noise figure (NF) and conversion gain of the receiver module are measured with the Y-factor method. The total noise temperature of 1310 +/- 100K(corresponding to an NF of 7.4 dB), including the losses in the lens and antenna, is measured at 220 GHz with a respective conversion gain of 3.5 dB. The radiated continuous-wave power from the transmitter module is measured to be up to -6 dBm from 212 to 226 GHz. The transmitter and receiver are linked in a quasi-optical setup and the IF to IF response is measured to be flat up to 10 GHz. This is verified to be usable for transmission of a 12.5-Gb/s data stream between the transmit and receive modules over a 0.5-m wireless link. The modules operate with a 1.3-V supply and each consume 110-mW dc power. The presented 220-GHz integrated circuits and modules can be used in a variety of applications, including passive and active imaging, as well as high-speed data communications. To the best of our knowledge, these MMICs are the highest frequency single-chip low-noise heterodyne receiver and transmitter pair reported to date.
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| 2. |
- Afsar Doost, Sepideh, 1983, et al.
(författare)
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Digital Predistortion Using a Vector Switched Model
- 2012
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:4, s. 1166-1174
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Tidskriftsartikel (refereegranskat)abstract
- Abstract—A switched behavioral model considering memory effects with special focus on ”difficult” amplifier architectures is proposed in this paper. The proposed model is shown to be very simple and linearly identifiable. A digital predistorter based on the proposed model is implemented for a 100–W, 2.6 GHz Doherty power amplifier that has been considered difficult in other reports, and it is shown that the proposed model can succesfully linearize the amplifier. In particular, the proposed model and the digital predistorter is shown to outperform other state-of-the-art models and digital predistorers in terms of computational complexity for a given desired accuracy.
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| 3. |
- Aksimsek, Sinan, et al.
(författare)
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TEM wave scattering by a step discontinuity on the outer wall of a coaxial waveguide
- 2013
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Ingår i: IEEE transactions on microwave theory and techniques. - : IEEE Press. - 0018-9480 .- 1557-9670. ; 61:8, s. 2783-2791
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the propagation of TEM waves along a coaxial waveguide with a step discontinuity on its outer wall is investigated rigorously by applying the direct Fourier transform and reducing the problem into the solution of a modified Wiener–Hopf equation. The solution for the field terms are determined in terms of an infinite number of unknown coefficients, which satisfy an infinite set of linear algebraic equations. These equations are solved numerically and the effect of area ratio is presented graphically at the end of the analysis. The same problem is also analyzed by applying the mode-matching technique and the results of the two approaches are compared. It is observed numerically that the Wiener–Hopf technique provides a better convergence than the mode-matching technique.
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| 4. |
- Amin, S., et al.
(författare)
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Behavioral Modeling and Linearization of Crosstalk and Memory Effects in RF MIMO Transmitters
- 2014
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 62:4, s. 810-823
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes three novel models for behavioral modeling and digital pre-distortion (DPD) of nonlinear 2 x 2 multiple-input multiple-output (MIMO) transmitters in the presence of crosstalk. The proposed models are extensions of the single-input single-output generalized memory polynomial model. Three types of crosstalk effects were studied and characterized as linear, nonlinear, and nonlinear & linear crosstalk. A comparative study was performed with previously published models for the linearization of crosstalk in a nonlinear 2 x 2 MIMO transmitter. The experiments indicate that, depending on the type of crosstalk, the selection of the correct model in the transmitter is necessary for behavioral modeling and sufficient DPD performance. The effects of coherent and partially noncoherent signal generation on the performance of DPD were also studied. For crosstalk levels of 30 dB, the difference in the normalized mean square error and adjacent channel power ratio was found to be 3-4 dB between coherent and partially noncoherent signal generation.
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| 5. |
- Amin, Shoaib, et al.
(författare)
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Behavioral modeling and linearization of crosstalk and memory effects in RF MIMO transmitters
- 2014
-
Ingår i: IEEE transactions on microwave theory and techniques. - 0018-9480 .- 1557-9670. ; 62:4, s. 810-823
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes three novel models for behavioral modeling and digital pre-distortion (DPD) of nonlinear 2 x 2 multiple-input multiple-output (MIMO) transmitters in the presence of crosstalk. The proposed models are extensions of the single-input single-output generalized memory polynomial model. Three types of crosstalk effects were studied and characterized as linear, nonlinear, and nonlinear & linear crosstalk. A comparative study was performed with previously published models for the linearization of crosstalk in a nonlinear 2 x 2 MIMO transmitter. The experiments indicate that, depending on the type of crosstalk, the selection of the correct model in the transmitter is necessary for behavioral modeling and sufficient DPD performance. The effects of coherent and partially noncoherent signal generation on the performance of DPD were also studied. For crosstalk levels of 30 dB, the difference in the normalized mean square error and adjacent channel power ratio was found to be 3-4 dB between coherent and partially noncoherent signal generation.
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| 6. |
- Andersson, Christer, 1982, et al.
(författare)
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A 1-3-GHz Digitally Controlled Dual-RF Input Power-Amplifier Design Based on a Doherty-Outphasing Continuum Analysis
- 2013
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 61:10, s. 3743-3752
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a linear multi-harmonic analysis method to evaluate the performance of digitally controlled dual RF-input power amplifiers (PAs). The method enables, due to its low computational cost, optimization of PA efficiency and bandwidth in a complex design space involving two independent inputs. Under the idealized assumption of short-circuited higher harmonics, the analysis is used to prove the existence of a Doherty-outphasing continuum, featuring high average efficiency over 100% fractional bandwidth. With this result as a foundation, a combiner incorporating microwave transistor parasitics is analyzed without assuming short-circuited higher harmonics, showing that high average efficiencies are also achievable under more realistic conditions. A PA is straightforwardly designed from these calculation results using two 15-W GaN HEMTs. The simulated layout-ready (large-signal transistor model) PA average drain efficiency exceeds 50% over 1.1-3.7 GHz for a 6.7-dB peak-to-average power-ratio WCDMA signal. The measured PA has a maximum output power of 44 +/- 0.9 dBm and a 6-dB output power back-off (OPBO) power-added efficiency (PAE) of 45% over 1-3 GHz. After applying digital pre-distortion, excellent linearity is demonstrated when transmitting the WCDMA signal, resulting in an adjacent channel leakage power ratio lower than -57 dBc with corresponding average PAE of 50% and 40% at 1.2 and 2.3 GHz, respectively. This is, to the authors' knowledge, the most wideband OPBO efficiency enhanced PA reported to date, proving the effectiveness of employing linear multi-harmonic analysis in dual-input PA design.
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| 7. |
- Andersson, Christer, 1982, et al.
(författare)
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Nonlinear Characterization of Varactors for Tunable Networks by Active Source-Pull and Load-Pull
- 2011
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 59:7, s. 1753-1760
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Tidskriftsartikel (refereegranskat)abstract
- Varactors are key components in the realization of tunable networks, for instance, in high-efficiency power-amplifier architectures. This paper presents a method to measure the varactor quality factor (Q-factor) in the presence of nonlinear distortion. The importance of correctly choosing the loading condition at the second harmonic is illustrated by multiharmonic active source- and load-pull measurements. Furthermore, the method also allows for accurate extraction of the bias-dependent series resistance without the need of area consuming resonant structures. The proposed method is applied to characterize a silicon-carbide (SiC) Schottky diode varactor at 3 GHz. The measured results reemphasize that varactors are not linear tunable, but inherently nonlinear components that require proper consideration of the higher order harmonics.
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| 8. |
- Andersson, Christer, 1982, et al.
(författare)
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Theory and Design of Class-J Power Amplifiers With Dynamic Load Modulation
- 2012
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 3778-3786
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Tidskriftsartikel (refereegranskat)abstract
- A theory for class-J microwave amplifier operation as a function of drive level and fundamental load impedance is derived. Calculations show that, under appropriate operating conditions, it is sufficient to modulate the transistor load reactance to enable high-efficiency operation (>70%) over a large output power dynamic range (>10 dB) with high transistor power utilization. Such dynamic load modulation (DLM) networks are an ideal application of continuously tunable varactor technologies. Multiharmonic load–pull measurements are performed on a GaN HEMT and experimentally verify the theory of operation. A demonstrator amplifier using an SiC varactor technology is then designed and characterized by static measurements. The amplifier has a peak power of 38 dBm at 2.08 GHz and maintains efficiencies above 45% over 8 dB of power dynamic range. An analysis of the load network losses is performed to show the potential of the class-J DLM transmitter concept.
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| 9. |
- ANDERSSON, MICHAEL, 1988, et al.
(författare)
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Resistive Graphene FET Subharmonic Mixers: Noise and Linearity Assessment
- 2012
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 4035-4042
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Anttila, Lauri, et al.
(författare)
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Joint Mitigation of Power Amplifier and I/Q Modulator Impairments in Broadband Direct-Conversion Transmitters
- 2010
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Ingår i: IEEE transactions on microwave theory and techniques. - 0018-9480 .- 1557-9670. ; 58:4, s. 730-739
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a novel digital predistorter structure for joint mitigation of frequency-dependent power amplifier (PA) and in-phase and quadrature (I/Q) modulator impairments in direct-conversion radio transmitters. The predistorter is based on an extended parallel Hammerstein structure, yielding a predistorter that is fully linear in the parameters. In the parameter estimation stage, the indirect learning architecture is utilized. The proposed technique is the first technique in the literature to consider the joint estimation and mitigation of frequency-dependent PAand I/Q modulator impairments. Extensive simulation and measurement analysis is carried out to verify the operation and efficacy of the proposed predistortion structure. It is shown that the adjacent channel power ratio is increased by more than 20 dB in all experiments when using the proposed method, and that the performance of the reference techniques is clearly exceeded.
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