SwePub - sökning: WFRF:(ÖZEN MUSTAFA 1984)

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1.	ÖZEN, MUSTAFA, 1984, et al. (författare) Linearization Study of a Highly Efficient CMOS-GaN RF Pulse Width Modulation Based Transmitter 2012 Ingår i: European Microwave Conference. - : IEEE. ; , s. 136-139 Konferensbidrag (refereegranskat)abstract This paper studies linearity of a 2 GHz, 10 Watt peak output power RF pulse width modulation (RF-PWM) based transmitter. The transmitter incorporates a tunable load network class-E PA as the final output stage. The tunable load network enables dynamic optimization of the class-E along with the duty cycle resulting in high efficiency over a wide range of output power levels. A digital predistiortion based linearization scheme is proposed to enhance the linearity of the transmitter. After linearization, the transmitter exhibits an adjacent channel power ratio (ACPR) of -45 dBc with a 3.84 MHz, 6.7 dB peak-to-average power ratio (PAPR) W-CDMA signal. The average drain efficiency of the GaN HEMT output stage is 67% and the total transmitter efficiency is 54%.
2.	Andersson, Christer, 1982, et al. (författare) A packaged 86 W GaN transmitter with SiC varactor-based dynamic load modulation 2013 Ingår i: 43rd European Microwave Conference, EuMC 2013 - Held as Part of the 16th European Microwave Week, EuMW 2013, Nuremberg, Germany, 7-10 October 2013. - 9782874870316 ; , s. 283-286 Konferensbidrag (refereegranskat)abstract Output power scaling based on class-J dynamic load modulation (DLM) theory is used to design an unprecedentedly high power microwave transmitter with varactor-based DLM functionality. Matching networks are realized on high dielectric constant substrates in order to reduce the form factor. The fully matched DLM PA incorporates a 24-mm GaN HEMT powerbar and a stack of four SiC varactors, all fit into a CuW package (40 mm × 20 mm). Peak output power is reconfigurable by changing the drain voltage, while retaining the DLMeffect. Under pulsed conditions at 40 V the PA delivers a peak power of 86 W at 2.14 GHz. Efficiency enhancement by DLM is 10-15 percentage-units at 6 dB output power back-off (OPBO). Employing digital predistortion (DPD) with a vector switched generalized memory polynomial (VS-GMP) the ACLR is -46 dBc at an average output power of 17 W and a drain efficiency of 34%. These results prove the potential for high output power levels in varactor-based DLM transmitters.
3.	Asbeck, Peter M., et al. (författare) Power Amplifiers for mm-Wave 5G Applications: Technology Comparisons and CMOS-SOI Demonstration Circuits 2019 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 67:7, s. 3099-3109 Tidskriftsartikel (refereegranskat)abstract A review is presented of key power amplifier (PA) performance requirements for millimeter-wave 5G systems, along with a comparison of the potential of different semiconductor technologies for meeting those requirements. Output power, efficiency, and linearity considerations are highlighted, and related to semiconductor material characteristics. Prototype 5G PAs based on silicon technologies are then reviewed, with primary emphasis on CMOS-SOI. Stacked FET PAs based on nMOS and pMOS for 28-GHz operation are presented, along with outphasing and Doherty amplifiers. Peak power-added efficiency (PAE) up to 46% is demonstrated for a two-stack pMOS amplifier with saturation power (Psat) above 19 dBm. PAE at 6 dB backoff above 27% is shown for an nMOS Doherty PA with 22-dBm Psat. Operation with 64QAM OFDM modulation signals at 800-MHz bandwidth is reported, with up to 13-dBm output power and more than 17% PAE, without the use of digital predistortion. Future challenges for PA development are discussed.
4.	Chani Cahuana, Jessica, 1988, et al. (författare) Digital Predistortion Parameter Identification for RF Power Amplifiers Using Real-Valued Output Data 2017 Ingår i: IEEE Transactions on Circuits and Systems II: Express Briefs. - 1549-7747 .- 1558-3791. ; 64:10, s. 1227-1231 Tidskriftsartikel (refereegranskat)abstract This brief presents a novel digital predistortion (DPD) parameter identification technique that requires only the acquisition of either the in-phase (I) or the quadrature (Q) component of the power amplifier (PA) output signal. To this end, an approach that allows us to estimate the parameters of a model using only one of the IQ components of the model output is presented. Based on experimental results, it is shown that the proposed real-valued measurements based technique can offer similar linearization capabilities as its complex-valued counterparts. The experimental results also indicate that the proposed technique can be used in combination with other techniques that focus on reducing the speed of analog-to-digital converters (ADCs)
5.	Fager, Christian, 1974, et al. (författare) Design of linear and efficient power amplifiers by generalization of the Doherty theory 2017 Ingår i: Proceedings of the 2017 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications. - 9781509034574 ; , s. 29-32 Konferensbidrag (refereegranskat)abstract The Doherty power amplifier (PA) is now established as one the most widely adopted architectures for enhancement of energy efficiency in wireless communication transmitters. More than 80 years after its invention, most of today's implementations still rely on the original circuit topology. This paper describes a new Doherty solution continuum that is revealed when the original λ/4 combiner is replaced by a generic, analytically derived, lossless combiner network. As a result, novel Doherty PA solutions that in practice are both more efficient and more linear are enabled. A variety of practical design examples are included to illustrate how the presented techniques can enable enhanced performance in both traditional and emerging mm-wave 5G wireless communication transmitter applications.
6.	Hallberg, William, 1988, et al. (författare) A class-J power amplifier with varactor-based dynamic load modulation across a large bandwidth 2015 Ingår i: 2015 IEEE MTT-S International Microwave Symposium, IMS 2015. - 9781479982752 Konferensbidrag (refereegranskat)abstract A novel class-J operated power amplifier (PA) utilizing varactor-based dynamic load modulation is presented. It is theoretically shown that the proposed PA can maintain high average efficiency across more than 35% RF bandwidth by means of a purely reactive load modulation after the transistor output capacitance. The theory is experimentally verified by a 15 W GaN HEMT PA operating from 1.80 to 2.20 GHz, using SiC varactors as dynamically tunable load elements. In the band, the PA presents a power added efficiency (PAE) higher than 39% at 6 dB output power back-off. For a 3.84 MHz W-CDMA signal with 6.7 dB peak to average power ratio, an average PAE higher than 39% and an adjacent channel leakage ratio below -45.8 dBc are obtained across the entire band after linearization.
7.	Hallberg, William, 1988, et al. (författare) A Doherty Power Amplifier Design Method for Improved Efficiency and Linearity 2016 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 64:12, s. 4491-4504 Tidskriftsartikel (refereegranskat)abstract A novel Doherty power amplifier (PA) design method enabling high efficiency and high linearity simultaneously is proposed. The output combiner network is treated as a black box, and its parameters, together with the input phase delay, are solved based on given transistor characteristics and design requirements. This opens for new PA solutions with nonconventional Doherty behavior. The increased design space enables new tradeoffs in Doherty PA designs, including solutions with both high efficiency and high linearity simultaneously. A method utilizing the new design space is developed. For verification, a 20-W 2.14-GHz symmetrical gallium nitride high electron mobility transistors Doherty PA is fabricated and measured. The PA obtains an average power added efficiency of 40% and an adjacent power leakage ratio of -41 dBc without any linearization for an 8.6-dB peak to average power ratio 10-MHz-long term evolution signal, at an average output power of 35.5 dBm.
8.	Hallberg, William, 1988, et al. (författare) Characterization of linear power amplifiers for LTE applications 2018 Ingår i: PAWR 2018 - Proceedings 2018 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications. - 9781538612897 ; 2018-January, s. 32-34 Konferensbidrag (refereegranskat)abstract This paper compares the performance of and analyzes the linearity metrics with different signals for two linear PAs: A single-ended class-AB PA and a linear Doherty PA (DPA). Both PAs utilize the 6 W GaN HEMT CGH40006P at a design frequency of 3 GHz for the class-AB PA and 3.5 GHz for the DPA. Different linearity metrics are studied for a 5-MHz spaced two-tone signal and a 5-MHz Long Term Evolution signal. The DPA has a power added efficiency of 40% whereas the class-AB PA shows 27% given a-40 dBc linearity constraint on the closest adjacent channel (ACPRi). The class-AB PA, however, exhibits better linearity in terms of ACPR2. It is additionally shown that the trends of the linearity metrics for the different signals differ for the two architectures.
9.	Hallberg, William, 1988, et al. (författare) Current scaled Doherty amplifier for high efficiency and high linearity 2016 Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781509006984 ; 2016-August, s. Art. no. 7540185- Konferensbidrag (refereegranskat)abstract In this paper, a novel Doherty power amplifier (PA) design method that enables high efficiency and high linearity simultaneously is developed. The output combiner network parameters are solved to satisfy boundary conditions required for high efficiency, and linear gain and phase responses. The proposed method is experimentally verified by a 2.14 GHz prototype PA, fabricated using two identical 15 W GaN HEMT devices. For a 8.6 dB peak to average power ratio 10 MHz LTE signal, the PA presents an average power added efficiency of 40%, and an adjacent power leakage ratio of -41 dBc without any linearization.
10.	Lai, Szhau, 1985, et al. (författare) Low Phase Noise GaN HEMT Oscillators With Excellent Figures of Merit 2014 Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 24:6, s. 412-414 Tidskriftsartikel (refereegranskat)abstract This letter presents guidelines for the design of low phase noise oscillators in GaN high electron mobility transistor (HEMT) technology. The design starts from bias-dependent low-frequency (LF) noise measurements. Oscillator topology and bias point are then chosen for operation in regions where LF noise is low. The best LF noise properties are obtained for low drain voltage and current. Thus, the low phase noise can be achieved at low dc power which also means that power normalized phase noise figure of merit (FOM) will be good.
11.	Mashad Nemati, Hossein, 1980, et al. (författare) Varactor-Based Dynamic Load Modulation of RF PAs 2011 Ingår i: European Microwave Conference, Manchester, Workshop "RF PA Efficiency Enhancement Techniques". Konferensbidrag (övrigt vetenskapligt/konstnärligt)
12.	Pamoin-Gonzalez, M, 1900, et al. (författare) Outphasing combiner synthesis from transistor load pull data 2015 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.
13.	Pengelly, R., et al. (författare) Doherty's Legacy 2016 Ingår i: IEEE Microwave Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 1527-3342 .- 1557-9581. ; 17:2, s. 41-58 Forskningsöversikt (refereegranskat)abstract William H. Doherty was an American electrical engineer, best known for his invention of the Doherty amplifier. Born in Cambridge, Massachusetts, in 1907, Doherty attended Harvard University, where he received his bachelor's degree in communication engineering (1927) and his master's degree in engineering (1928). He then joined the American Telegraph and Telephone Company Long Lines Department in Boston. He remained there for a few months before joining the National Bureau of Standards, where he researched radio phenomena. Doherty joined Bell Telephone Laboratories (now Bell Labs) in 1929 and, while there, worked on the development of high power radio transmitters that were used for transoceanic radio telephones and broadcasting.
14.	Rostomyan, Narek, et al. (författare) 28 GHz Doherty Power Amplifier in CMOS SOI With 28% Back-Off PAE 2018 Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 28:5, s. 446-448 Tidskriftsartikel (refereegranskat)abstract A single-stage, symmetric Doherty power amplifier (PA) in 45 nm CMOS silicon on insulator at 28 GHz is presented. The PA achieves a saturated output power of 22.4 dBm, a peak power added efficiency (PAE) of 40%, and a 6 dB backoff PAE of 28%. High efficiency is attained due to low combiner losses of 0.5 dB, obtained using a recently developed combiner synthesis technique. A compact modeling approach for parasitic-extracted PA transistors is presented, which considerably reduced simulation time. The PA is based on two-stack power devices and occupies overall chip area of only 0.63 mm(2), including pads.
15.	Sanchez Perez, Cesar, 1981, et al. (författare) Optimized Design of a Dual-Band Power Amplifier With SiC Varactor-Based Dynamic Load Modulation 2015 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 63:8, s. 2579-2588 Tidskriftsartikel (refereegranskat)abstract A new methodology for the design of single/multi-band power amplifiers (PAs) with dynamic load modulation (DLM) is presented. First, the topology for the output matching network (OMN) including the control varactor is selected. A comprehensive optimization of the OMN parameters is then developed by which varactor and transistor losses are considered to ensure maximum efficiency enhancement at each frequency. To verify the method, a dual-band PA with DLM is realized. Drain efficiencies of 75% and 60% at 685 MHz and 1.84 GHz, respectively, are measured at peak output power. At 10-dB output power back-off efficiencies of 43.5% and 49.5%, respectively, are obtained. Linearized modulated measurements with a 6.5-dB peak-to-average power ratio WCDMA signal show average drain efficiencies of 56% and 54% at 685 MHz and 1.84 GHz, respectively, at an adjacent channel leakage ratio of -49 and -47.5 dBc, respectively. The proposed method shows the effectiveness of applying an optimization process for the design of single-or multi-band DLM PAs. The results demonstrate that near-optimum performance may be obtained in terms of efficiency enhancement for a given transistor and varactor-based OMN, thus making DLM competitive against other load modulation techniques.
16.	ÖZEN, MUSTAFA, 1984, et al. (författare) A Generalized Combiner Synthesis Technique for Class-E Outphasing Transmitters 2017 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 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.
17.	ÖZEN, MUSTAFA, 1984 (författare) Advanced Transmitter Architectures Based on Switch Mode Power Amplifiers 2014 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Nowadays the main driving parameters for the research in radio transmitters in wireless infrastructure are energy efficiency, frequency agility, and integration.This thesis presents new solutions at the device waveform-, circuit-, and transmitter level which exploit the inherent high efficiency potential of switch-mode power amplifiers (SMPAs) for realization of energy efficient, wide-band, highly integrated transmitters for wireless communication applications.In the first part of the thesis, a continuum of novel high efficiency class-E power amplifier modes are derived, significantly extending the known SMPA design space. In contrast to conventional SMPA modes, the new continuum allows some variation for the switch impedances, providing important possibilities on wide-band SMPA designs. This is experimentally verified in a 1 W SiGe BiCMOS SMPA design having a drain efficiency of above 70% over a 1.3-2.2 GHz bandwidth.In the second part a novel combiner synthesis technique is developed that enables realization of wide-band highly efficient outphasing transmitters. The technique is based on the calculation of the combiner network parameters from the boundary conditions required for highly efficient switch-mode operation of the transistors in each branch. The approach is validated in a CMOS-GaN outphasing transmitter design providing a peak output power of 44 dBm and a 7.5 dB output power back-off efficiency exceeding 52% over a 750-1050 MHz bandwidth. It is further shown that the same theoretical approach can also be used for design of Doherty PA combiner networks. A 28 W 3.5 GHz Doherty PA is designed and manufactured for experimental verification providing a record-high power added efficiency of 51% at an adjacent channel leakage ratio (ACLR) of -50 dBc with carrier-aggregated 100 MHz LTE test signals.In the third part a new SMPA topology particularly suitable for amplification of RF pulse-width modulation (RF-PWM) signals is presented. In classical pulse width modulated SMPAs the varying pulse width leads to switching losses and hence efficiency degradation. We present an electronically tunable load output network that alleviates this problem.A 10 W 2 GHz CMOS-GaN RF-PWM transmitter demonstrator is constructed and characterized to demonstrate the feasibility of the proposed technique. ACLR after digital pre-distortion linearization is -45 dBc at a drain efficiency of 67% with W-CDMA communication signals.The solutions presented in this thesis will facilitate realizations of frequency agile, energy efficient and highly integrated/digitalized radio transmitters for future wireless communication systems.
18.	ÖZEN, MUSTAFA, 1984 (författare) Class-E Power Amplifiers for Pulsed Transmitters 2012 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Nowadays the main driving parameters for the radio transmitter research are: energy efficiency, frequency re-configurability and integration. Pulsed transmitter architectures have attracted large interest in the recent years due to their potential to meet these demands. In pulsed transmitters, a highly efficient switch mode power amplifier (SMPA) is used in conjunction with a pulse modulator to achieve high efficiency linear amplification. Digital implementation of the modulator enables wide bandwidth for the signal generation path and improves the level integration. The bandwidth in a pulsed transmitter is however typically limited by the load matching network of the SMPA. This thesis presents two main contributions in the field of pulsed transmitter architectures.In the first part focus is given to bandwidth improvement of class-E switch mode PAs. A continuum of novel closed-form class-E modes is derived extending the traditional class-E design space. The extended design space provides important possibilities for wide band design of the class-E load networks and for further efficiency optimization of class-E PAs. A wide band design methodology is thus developed based on the analytical design equations.In the second part, focus is given to efficiency improvement of RF pulse width modulation (RF-PWM) based transmitters. A new SMPA topology particularly suitable for energy efficient amplification of 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 pulse width. Using in-house (Chalmers University) SiC varactor diodes to implement the tunable load impedance, a 2 GHz 10 W peak output power CMOS-GaN HEMT RF-PWM transmitter demonstrator is realized. The static measurements show that a drain efficiency >70% can be obtained over a 6.5 dB dynamic range. A digital pre-distortion based linearization scheme is proposed to enhance the linearity of the transmitter. An adjacent power ratio of -45 dBc and average drain efficiency of 67% is achieved using a realistic W-CDMA communication signal. These results clearly demonstrate the feasibility of the proposed pulsed transmitter topology for high efficiency linear amplification.
19.	ÖZEN, MUSTAFA, 1984, et al. (författare) Combiner synthesis for active load-modulationbased power amplifiers 2019 Ingår i: Radio Frequency and Microwave Power Amplifiers: Efficiency and Linearity Enhancement Techniques. ; , s. 225-253 Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract This chapter discusses the fundamental operation of Doherty and outphasing Pas. Rather than using the original combiner topologies as a starting point, our focus will be on the desired transistor operation. Based on the active loadmodulation conditions that the Doherty and outphasing Pas dictate, we will therefore instead derive the combiners that present the desired behavior. The original solutions will thus appear as special cases when ideal operation is assumed. For any other case, new solutions will appear. We will show how this approach can give both new insights, extended design spaces and improved performance. In the first part of this chapter, we will establish a theoretical framework for Doherty and outphasing combiner synthesis from the conditions that guarantee efficient operation. This will thereafter be applied and practically demonstrated, first in a Doherty design context and then in an outphasing design context. The chapter will be concluded with a brief summary and suggestions for future work.
20.	ÖZEN, MUSTAFA, 1984, et al. (författare) Continuous Class-E Power Amplifier Modes 2012 Ingår i: IEEE Transactions on Circuits and Systems II: Express Briefs. - 1549-7747 .- 1558-3791. ; 59:11, s. 731-735 Tidskriftsartikel (refereegranskat)abstract In this brief, a continuum of novel closed-form solutions is derived for class-E power amplifiers (PAs). It is analytically proven that the class-E zero voltage/zero voltage derivative switching conditions can be satisfied for an arbitrarily selected reactive second harmonic switch impedance (Z 2 S ). The higher order harmonic currents are terminated capacitively. The conventional class-E, class- E/F 2 , and class-EF 2 modes are thus subsets of the continuum. The arbitrary selection of Z 2 S enables robust waveform engineering for performance optimization in specific applications. Furthermore, the theoretical derivation provides important possibilities for wideband class-E PA synthesis. © 2004-2012 IEEE.
21.	ÖZEN, MUSTAFA, 1984, et al. (författare) Efficient Millimeter Wave Doherty PA Design Based on a Low-Loss Combiner Synthesis Technique 2017 Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 27:12, s. 1143-1145 Tidskriftsartikel (refereegranskat)abstract We report on a record-efficient 30-GHz 21-dBm differential Doherty PA designed in a 130-nm SiGe process. The output network is designed using a recently developed combiner synthesis technique. This technique enables impedance inversion and parasitic compensation to be integrated in one compact network. As a result, the combiner loss is reduced with 0.3-0.5 dB compared with a conventional Doherty combiner. The measured collector and power-added efficiencies at 6-dB back-off level are 30% and 24.3%, respectively, which further validates the advantages of the design technique.
22.	ÖZEN, MUSTAFA, 1984, et al. (författare) High efficiency RF pulse width modulation with tunable load network class-E PA 2011 Ingår i: 2011 IEEE 12th Annual Wireless and Microwave Technology Conference, WAMICON 2011. - 9781612840819 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.
23.	ÖZEN, MUSTAFA, 1984, et al. (författare) High-Efficiency RF Pulsewidth Modulation of Class-E Power Amplifiers 2011 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 59:11, s. 2931-2942 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.
24.	ÖZEN, MUSTAFA, 1984, et al. (författare) Symmetrical doherty amplifier with high efficiency over large output power dynamic range 2014 Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781479938698 Konferensbidrag (refereegranskat)abstract For the conventional Doherty power amplifiers, asymmetrical cells are used to achieve high efficiency over large (> 6 dB) output power dynamic ranges, i.e. larger class-C cell. In this paper, it will be theoretically proven that high efficiency over large dynamic ranges also can be achieved using symmetrical devices, while still maintaining full voltage and current swing of both transistor cells. Using a smaller class-C cell compared to the asymmetrical Doherty has the advantages of higher gain and power added efficiency (PAE). The proposed symmetrical Doherty concept is experimentally verified by a 3.5 GHz 28 Watt circuit demonstrator fabricated using identical GaN HEMT devices. An average power added efficiency of 52% and adjacent power leakage ratio of -52 dB is obtained with 9 dB peak-to-average power-ratio 20 MHz LTE test signals.
25.	ÖZEN, MUSTAFA, 1984, et al. (författare) Symmetrical Doherty Power Amplifier With Extended Efficiency Range 2016 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 64:4, s. 1273-1284 Tidskriftsartikel (refereegranskat)abstract A symmetrical Doherty power amplifier (PA) with an extended efficiency range is proposed. This paper proves the existence of a class of symmetrical Doherty PAs having efficiency peaks for back-off levels larger than 6 dB. A design technique is developed that maintains the full voltage and current swings of both the main and auxiliary transistors. The concept is experimentally verified in a 1.95-GHz 25-W circuit demonstrator fabricated using identical GaN HEMT devices. An average power-added efficiency of 50% and adjacent power leakage ratio of -49 dBc is obtained with 9-dB peak-to-average power-ratio 20-MHz long-term evolution test signals.
26.	ÖZEN, MUSTAFA, 1984, et al. (författare) Wideband and efficient watt-level SiGe BiCMOS switching mode power amplifier using continuous class-E modes theory 2014 Ingår i: Digest of Papers - IEEE Radio Frequency Integrated Circuits Symposium. - 1529-2517. - 9781479938629 ; , s. 243-246 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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