GaN HEMT Doherty Power Amplifier Research Articles

Small-Cell 기지국 시스템을 위한 2.6 GHz GaN-HEMT Doherty 전력증폭기 집적회로 설계

This paper presents a 2.6 GHz Doherty power amplifier IC to enhance the back-off efficiency. In order to apply to small-cell base stations, the Doherty power amplifier was fabricated using GaN-HEMT process for high power density. In addition, the implemented Doherty power amplifier was mounted on a QFN package. The implemented GaN-HEMT Doherty power amplifier was measured using LTE downlink signal with 10 MHz bandwidth and 6.5 dB PAPR for verification. A power gain of 15.8 dB, a drain efficiency of 43.0 %, and an ACLR of -30.0 dBc were obtained at an average output power level of 33.9 dBm.

Design of a Concurrent Dual-Band 1.8–2.4-GHz GaN-HEMT Doherty Power Amplifier

In this paper, the design, implementation, and experimental results of a high-efficiency dual-band GaN-HEMT Doherty power amplifier (DPA) are presented. An extensive discussion about the design of the passive structures is presented showing different possible topologies of the dual-band DPA. One of the proposed topologies is used to design a dual-band DPA in hybrid technology for the frequency bands 1.8 and 2.4 GHz with the second efficiency peak at 6-dB output power back-off (OBO). For a continuous-wave output power of 20 W, the measured power-added efficiency (PAE) is 64% and 54% at 1.8 and 2.4 GHz, respectively. At -dB OBO, the resulting measured PAEs were 60% and 44% in the two frequency bands. Linearized concurrent modulated measurement using 10-MHz LTE signal with 7-dB peak-to-average-ratio (PAR) at 1.8 GHz and 10-MHz WiMAX signal with 8.5-dB PAR at 2.4 GHz shows an average PAE of 34%, at an adjacent channel leakage ratio of -48 dBc and -46 dBc at 1.8 and 2.4 GHz, respectively.

A High-Efficiency Low-Distortion GaN HEMT Doherty Power Amplifier With a Series-Connected Load

A distortion reduction method for a newly developed GaN HEMT Doherty amplifier (DA) with a series-connected load operating at 1.8 GHz is presented. Differing from conventional DAs with shunt-connected loads, the newly developed DA with a series-connected load has high input impedance, resulting in low-loss impedance matching and high-efficiency power combining. A distortion cancellation mechanism and its condition are derived, where odd-order nonlinear factors of transistors are considered, so as to retain inherent distortion cancellation between a peaking amplifier and a carrier amplifier. The validity of the design method is demonstrated using the developed 1.8-GHz GaN HEMT DA with a series-connected load. The third-order intermodulation distortion of the DA is improved by more than 15 dB at output powers from 5 to 20 dBm, compared to the case giving priority to power efficiency. The developed amplifier delivers a power-added efficiency (PAE) of 31% at an output power of 24 dBm, corresponding to 10-dB input backoff from a saturated output power of 31 dBm with a PAE of 58%. The proposed distortion reduction method can also be applied to shunt-connected-load-type amplifiers of other devices.

A wideband digital predistortion for highly linear and efficient GaN HEMT Doherty power amplifier

AbstractIn this article, we propose the wideband digital predistortion (WDPD) for a highly linear and efficient GaN HEMT Doherty power amplifier (DPA). The WDPD is composed of the memory less DPD and the memory system, which compensates for the memory effects to achieve a highly linear wideband performance. The 11th‐memoryless polynomial characterizes the behavioral model of the DPA. The AM/AM and AM/PM lookup tables and the coefficients of the memory system are determined by the Recursive Least Square algorithm. For a 2‐FA WCDMA signal with 10 MHz carrier spacing at 2.14 GHz, the adjacent channel leakage ratio at ±10 MHz offset are improved over −50 dBc without the efficiency degradation at an output power of 36 dBm. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 484–487, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24951

Optimum design of highly linear and efficient GaN HEMT Doherty amplifier considering the soft turn‐on effects

AbstractIn this article, we propose the optimum design of a highly linear and efficient Doherty power amplifier (DPA) considering the soft turn‐on effects of the GaN HEMT. To compensate for the soft turn‐on characteristic and obtain an extended high‐efficiency range, the DPA is designed with unequal drain biases. For experimental validations, the carrier and peaking cells are designed and implemented with the drain bias of 23 V and 33 V, respectively, using 25‐W GaN HEMTs at 2.6 GHz and then tested using a continuous wave and a one‐carrier WCDMA signal. The measured results show the superior performance for the proposed GaN HEMT DPA. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 956–959, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24210

Unequal-Cells-Based GaN HEMT Doherty Amplifier With an Extended Efficiency Range

This letter reports an extended GaN HEMT Doherty power amplifier (DPA). For high efficiency over a wide output power range, the DPA is designed using two cells with unequal saturation power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> ). A cell with lower P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> is used as the carrier cell. For experimental validations, the carrier and peaking cells are designed and implemented with 25 W GaN HEMTs at wide-band code division multiple access (WCDMA) of 2.14 GHz, and then show the P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> of 41.3 dBm and 43.6 dBm, respectively. For the proposed DPA, the single-tone results show the power-added efficiency (PAE) of 50% at an output power of 37.3 dBm (9 dB back-off power from P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> ). For a one-carrier WCDMA signal, the PAE of 47.9% with an adjacent channel leakage ratio of -35.8 dBc is obtained at 37.3 dBm, which is 7.9% improvement compared to the conventional DPA. The PAE of 40% is maintained over an 11.4 dB back-off power.