Development of single-stage and Doherty GaN-based hybrid RF power amplifiers for quasi-constant envelope and high PAPR wireless standards (original) (raw)
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A Method for Designing Broadband Doherty Power Amplifiers
Progress In Electromagnetics Research, 2014
In this contribution, a design approach for the realization of broadband Doherty Power Amplifiers (DPAs) is proposed and demonstrated. The methodology is based on the exploitation of the wideband response of 2-sections branch-line couplers both as input splitter and output combiner of the DPA. These couplers are designed through a CAD optimization process which is specifically oriented to the development of DPAs. The method is also applied to realize a GaN based hybrid prototype that shows more than 36% of fractional bandwidth around 2 GHz frequency range, validated through single carriers and modulated signals (3gpp and WiMax). In single carrier mode an efficiency higher than 41% (> 50% in saturation, with a peak of 72%) is obtained in 6 dB of output power dynamic range in the entire operating band. Experimental results with 5 MHz 3gpp and WiMax signals shown an average efficiency of 50% and 45% when 37 dBm and 34 dBm of average output power are reached, respectively.
Design scheme for broadband Doherty power amplifier using broadband load combiner
International Journal of RF and Microwave Computer-Aided Engineering, 2015
This article proposes a design strategy for broadband Doherty power amplifier (PA) using broadband load combiner. The bandwidth of the Doherty PA based on the proposed combiner using packaged transistor is about 2.5 times the bandwidth of conventional Doherty PA using a quarter-wave transformer. An easy to implement analytical design methodology has been presented for the proposed load-combiner while describing the bandwidth enhancement strategy. The design methodology is validated with the design of a broadband Doherty PA based on CREE 10 W packaged GaN high electron mobility transistor devices using the proposed load combiner. Measurement results show more than 45% drain efficiency at 6 dB output power back-off (OPBO) over 400 MHz frequency range, centred around 1.95 GHz. The peak drain efficiency at saturation is better than 60% over this band of operation. At 6 dB OPBO, the maximum improvement of 18.5% in drain efficiency is achieved as compared to the balanced mode PA. Measurement with single carrier wideband code division multiple access modulated signal shows the average drain efficiency of more than 44% at 36.6 dBm average output power at center frequency of operation. The adjacent channel power ratio is better than 245 dBc after applying digital predistortion. The circuit is realized with microstrip technology, which can be easily fabricated using conventional printed circuit processes. V
This paper presents the progress of monolithic technology for microwave application, focusing on gallium nitride technology advances in the realization of integrated power amplifiers. Three design examples, developed for microwave backhaul radios, are shown. The first design is a 7 GHz Doherty developed with a research foundry, while the second and the third are a 7 GHz Doherty and a 7-15 GHz dual-band combined power amplifiers, both based on a commercial foundry process. The employed architectures, the main design steps and the pros and cons of using gallium nitride technology are highlighted. The measured performance demonstrates the potentialities of the employed technology, and the progress in the accuracy, reliability and performance of the process.
Design strategy of a 2.8–3.6 GHz 20W GaN Doherty power amplifier
2020
This paper presents the design of a 20W GaN Doherty Power Amplifier working in the range 2.8 GHz–3.6 GHz. The design strategy adopted for the design of the Doherty output combiner is discussed, which consists in embedding the device parasitics into the latter, implemented as a multi-stage quarter-wavelength transformer, in order to achieve wideband behaviour. The saturated output power ranges from 42dBm to 44 dBm, with a corresponding drain efficiency in excess of 47%. The efficiency at 6 dB of output back-off is higher than 42% over the whole frequency band, and the small-signal gain is higher than 10 dB. Due to the discrepancies of the measured scattering parameters compared to the simulated ones, which could not be corrected with post-tuning, a redesign of the prototype is ongoing.
A Compact Output Power Combiner for Broadband Doherty Power Amplifiers
Electronics
A novel compact output power combiner for broadband Doherty Power Amplifiers is proposed in this paper. The proposed output power combiner avoids the use of quarter-wave impedance transformers as they are sizable and work over narrow bandwidths. Instead, the proposed combiner utilizes a distributed Brune Section to implement a compact broadband impedance inverter. The final area of the proposed output combiner is λ2/48. When compared to the conventional broadband Doherty structure, which has an approximate area of λ2/16, this structure offers an approximate size reduction of 67%. The proposed combiner is verified by using it in the design of a broadband Doherty power amplifier with an operating bandwidth of 1.7 GHz to 3.4 GHz. The saturated output power varies from 39.2 to 40.4 dBm with a peak power drain efficiency ranging from 58% to 66%. The drain efficiency at 6 dB Output Power Back-Off (OPBO) varies from 37.4% to 45% over an octave.
A Novel Configuration of a Microstrip Microwave Wideband Power Amplifier for Wireless Application
TELKOMNIKA Telecommunication Computing Electronics and Control, 2018
RF/microwave power amplifier (PA) is one of the components that has a large effect on the overall performance of communication system especially in transmitter system and their design is decided by the parameters of transistor selected. This letter presents a new concept of a wide-band microwave amplifier using scattering parameters that is often used in the radio frequency communication systemas an application of the active integrated antenna[1-2]. This power amplifier operates from 1.75 GHz to 2.15GHz frequency and it is based on AT-41410 NPN transistor that has a high transition frequency of 10GHz. The proposed Single Stage PA is designed by microstrip technology and simulated with Advanced Design System (ADS) software. The simulation results indicate good performances; the small power gain (S21) is changed between 11.8 and 10dB. For the input reflection coefficient (S11) is varied between-11 and-22.5dB. Regarding the output reflection coefficient (S22) is varied between-13.1 and-18.7dB over the wide frequency band of 1.75-2.15GHz and stability without oscillating over a wide range of frequencies.
A new design procedure for wide band Doherty power amplifiers
AEU - International Journal of Electronics and Communications, 2018
A generalized design procedure for Doherty power amplifier (DPA) with arbitrary output back-off power level (OBO) is proposed in this study. This method which covers many of previously reported configurations is employed to derive analytical formulas for a specific output combiner which is capable for absorbing parasitic elements of the main and auxiliary transistors. Combiner parameters can be adjusted to control operational frequency bandwidth at back-off and saturation. By considering parasitic elements in the design procedure, the needs for additional offset lines and CAD optimization are eliminated and efficiency does not degrade significantly at back-off. According to the proposed design methodology, a wide band DPA is designed, simulated and implemented with commercial packaged GaN transistor. Drain efficiency (DE) between 50 and 77% at 6 dB OBO and 57.5-80.4% at saturation in the frequency band of 1.05-2.35 (GHz) (76.4% fractional bandwidth) are achieved corresponding to the maximum output power and gain within 43-45.3 dBm and 11-13.3 dB, respectively. Gain fluctuation is lower than 0.6 dB for frequencies higher than 1.4 GHz. Combination of high efficiency, excellent power utilization factor and flat gain through an analytical design strategy introduces this method as a promising way to design wide band DPAs.
A Novel Two-Stage Broadband Doherty Power Amplifier for Wireless Applications
IEEE Microwave and Wireless Components Letters, 2018
Broadband and highly efficient amplifiers are of great interest in modern wireless communication systems. In this paper, we present a novel two-stage broadband Doherty power amplifier (DPA), which is able to maintain high efficiency at saturated output power and at backoff output power levels over a wide bandwidth. The amplifier uses a novel and simple approach to achieve bandwidth enhancement and at the same time uses a driver amplifier. We employ Klopfenstein taper to deliver wide bandwidth. The measurement results show that the proposed broadband two-stage DPA is able to deliver 31%-35% drain efficiency at 6-dB output power backoff while at the saturation it achieves 40%-55% drain efficiency over the designed bandwidth of 1.5 to 2.6 GHz. The amplifier can deliver above 35-dBm output power with substantial gain of around 20 dB. The proposed DPA is a promising candidate for wideband and high gain requirements in modern wireless systems.
Toward a More Generalized Doherty Power Amplifier Design for Broadband Operation
IEEE Transactions on Microwave Theory and Techniques, 2016
The conventional Doherty power amplifier (DPA) theory is limited to single carrier operations, leading to a nongeneric structure. This paper presents a new analysis that generalizes the conventional DPA theory for increased efficiency and bandwidth. We demonstrate that by introducing a theoretical parameter ߙ at the output combiner we can redefine the relationships among the output combiner elements for a greater level of design flexibility than it was possible in the conventional DPA. We also show that previously published works in this area can be considered as special cases of the proposed general theory. As a demonstrator, a specific design, named Reduced-ࢻ Doherty power amplifier, realized using GaN HEMTs is provided to illustrate the robustness of the approach. This design proves effective for further improving the performance of the previously published 2.14/2.655 GHz dual-band parallel DPA. A maximum drain efficiency of 84% and 67% at an average of 43-dBm peak and 6-dB back-off power levels, respectively, were measured with continuous wave signals. To quantify the linearity performance, the proposed DPA was tested using wideband CDMA and longterm evolution (LTE) signals where the adjacent channel leakage ratio was recorded at-25 dBc with an average output power of 38.7 and 36.5 dBm at 2.14 and 2.655 GHz, respectively.