A C-Band Broadband Asymmetric Doherty Power Amplifier Using Phase Compensation and Low Q Technology

This paper investigates the frequency response of load modulation networks for asymmetric Doherty power amplifiers (ADPA) with an output back-off power level larger than 6 dB and a power ratio of peak to main amplifier (N − 1) larger than 1. The influence of the main path impedance transformer (IT) on the Doherty impedances at main and peak path as well as on the ADPA's efficiency is analyzed. Scaling of the main IT's characteristic impedance via ξ indicates a maximum broadband matching for an input voltage Vin of ξ · Vin,max. By weighting the frequency- and ξ-dependent efficiency curves using a probability density function (PDF), an optimum is obtained for ξ = 1/N. To verify the theory, three ADPAs with different ξ-scaled ITs are designed, measured, and compared. For the design at 3.6 GHz, a gallium nitride (GaN) transistor is used. By means of the intrinsic node matching technique, matching at the current source plane is obtained. In laboratory measurements, the ADPA with ξ = 1/N achieves a power-added efficiency (PAE) of 63% at 42 dBm output power and a PDF-weighted average PAE of 38.8% within 400 MHz bandwidth for 8 dB peak-to-average power ratio. Comparison with similar state-of-the-art ADPAs in GaN technology shows highest PAE and operation power gain GP for center frequencies larger than 3.0 GHz.

In this article, a novel high‐efficient Doherty power amplifier (DPA) is designed for linearity improvement from 2.1 to 2.4 GHz. The proposed DPA employs a pair of anti‐coupled lines loaded with a stepped impedance resonator to replace the λ/4 transmission line in the conventional DPA for harmonic suppression, phase compensation, and impedance transformation. The DPA is simulated, fabricated, and measured. As the measured results show, in the 2.1‐2.4 GHz band, the saturated output power is between 43.2 and 44.5 dBm with the saturated gain level between 10.2 and 11.5 dB. The saturated drain efficiency (DE) is between 60% and 70% with DE at 6 dB output power back‐off between 38% and 50%. Compared with the conventional DPA, the third‐order intermodulation distortion is reduced by 20 dB. The efficiency and gain have also been improved. The proposed DPA is feasible and applicable in modern wireless communication systems.

This letter reports a high-efficiency gallium nitride (GaN) high-electron mobility transistor (HEMT) Doherty power amplifier (DPA) based on the class-E topology for wideband code-division multiple-access (WCDMA) applications. The class-E topology is employed as the carrier and peaking cells of the Doherty configuration. For validations, the proposed DPA is designed and implemented with 25-W GaN HEMTs at 2.14 GHz. For the proposed DPA, the power-added efficiency (PAE) and drain efficiency of 56.1% and 61.2% are achieved at 40 dBm (6-dB backoff power from Psat) for a continuous wave. For a 1-carrier WCDMA signal, the PAE of 44.8% is obtained with an adjacent channel leakage ratio (ACLR) of -31 dBc at 37 dBm, which is an 8.9% improvement over the conventional DPA with an ACLR of -36.4 dBc.

To achieve better performance, this paper proposes a Doherty power amplifier (DPA) design method based on 3-port theory on the basis of traditional asymmetric DPA. In this design method, the asymmetric DPA output matching network is regarded as a whole, and the 3-port output combinational network analysis method is adopted to design it, so as to maximize the efficiency at output power back-off (OPBO). To verify the design method, a 3.4-3.6 GHz asymmetric DPA using 10 and 30W GaN HEMT is designed. Measurement results show that the efficiencies at saturation power and 12 dB OPBO are higher than 68% and 50% respectively over the entire frequency range.

In this paper, we present a high efficiency Doherty power amplifier (PA) employing dynamic power dividing network which automatically adjusts the input power division ratio in accordance with the level of input power to enhance efficiency. Doherty PA circuit parameters of each amplifier are determined by basic performance analysis according to the datasheet. Simulated circuits through Advanced Design System (ADS) exhibit an improvement of 4% at a 6 dB backoff point from its saturated output power (PSAT) than that of a conventional Doherty PA. Implemented Doherty PA using two Freescale MRF6S27015N laterally diffused metal oxide semiconductor (LDMOS) field-effect transistors (FETs) achieves excellent drain efficiency of 46.5% at a 6 dB backoff point from PSAT, which is 2% higher than conventional Doherty PA.

ABSTRACTIn this article, we present a simplified Doherty power amplifier (DPA) architecture for the easy implementation of dual‐band operation. The proposed DPA structure eliminates the 35 Ω quarter wavelength impedance inverters used in the conventional DPAs by matching the output impedances of the carrier and peak amplifiers of the DPA to other values (e.g., 100 Ω). The electrical lengths of the offset line and the phase compensation line are carefully chosen to enhance the Doherty effect (high efficiency at back‐off power level) at two assigned frequency bands. Broadband matching networks are also designed to increase the operation bandwidths at the two designed bands. To prove the design concept, a dual‐band DPA is designed and measured. In the first frequency band (550–650 MHz), the designed DPA provides 60.6–76.3% drain efficiency (DE) at full output power, 46–54.9% DE at 6 dB of output power back‐off (OBO); in the second frequency band (950–1050 MHz), the designed DPA provides 51.4–61.2% DE at full output power, 35–38% DE at 6 dB of OBO. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:953–956, 2015

: A key component of microwave telecommunication systems is the power amplifier (PA). The design parameters of a communication system, such as link performance, power budget, and thermal design are typically driven by the power amplifier's linearity, output power, and efficiency. These design parameters of PA are the key to ensuring an efficient system because the PA is the most power-consuming circuit in the communication system. In an effort to have students involved in this research area, the International Microwave Symposium (IMS) sponsored by IEEE Microwave Theory and Technique Society (MTT-S) has introduced a High Efficiency Power Amplifier Design Competition. In this report, we present a 2.8-GHz, 5-W, highly efficient PA based on a wide bandgap gallium nitride (GaN) high electron mobility transistor (HEMT) device (CGH 40010f from CREE). The PA design was presented at the 2010 IMS Student Design Competition and achieved the competition goal of output power greater than 5 W with a measured power added efficiency (PAE) of 61% at 2.8 GHz.

Much attention has been paid to making 5G developments more energy efficient, especially in view of the need for using high data rates with more complex modulation schemes within a limited bandwidth. The concept of the Doherty power amplifier for improving amplifier efficiency is explained in addition to a case study of a 70 W asymmetrical Doherty power Amplifier using two GaN HEMTs transistors with peak power ratings of 45 W and 25 W. The rationale for this choice of power ratio is discussed. The designed circuit works in the 3.4 GHz frequency band with 200 MHz bandwidth. Rogers RO4350B substrate with dielectric constant er = 4.66 and thickness 0.035 mm is used. The performance analysis of the Doherty power amplifier is simulated using AWR MWO software. The simulated results showed that 54–64% drain efficiency has been achieved at 8 dB back-off within the specified bandwidth with an average gain of 10.7 dB.

This paper presents a compact transformer-based linear and efficient power amplifier (PA) in 0.13-μm SiGe:C BiCMOS for 5G applications. To reduce the form factor, an ultra-compact neutralized cascode PA core is proposed, which achieves a state-of-the-art power density. To obtain a gain flatness at 5G NR band n257 (26.50-29.50GHz), transformer-based input and output matching networks are designed. The PA demonstrates a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$S_{21}$</tex> 3-dB bandwidth <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(BW_{-3\text{dB}})$</tex> of 10.5GHz from 23.5 to 34GHz. At 28GHz/29GHz, the saturated output power ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$P_{\text{sat}}$</tex> ) are 22.7/22.4dBm with power-added efficiency (PAE) of 38.1/39.8%. The PA also supports 64- and 256-QAM modulated signal tests without digital pre-distortion (DPD). Over 26-30GHz, for 4.8Gb/s 64-QAM signals with peak-to-average power ratio (PAPR) 8.3dB at −25dB EVM, this PA continuously achieves >16dBm average power ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$P_{\text{avg}}$</tex> ) with >11% PAE.

An asymmetric Doherty Power Amplifier (ADPA) is introduced using a new output combining circuit for easy of implementation with a large matching tolerance. The proposed APDA has been implemented using GaN HEMT devices at 2.6 GHz for WiMAX signal with 5MHz bandwidth and 8.3 dB peak to average power ratio. This ADPA delivers a saturated output power of 51.7 dBm and a drain efficiency of 60.4% at an average output power of 43.6 dBm. After linearization using digital feedback predistortion technique, the ADPA satisfies the linearity specification with -51.98 dBc of adjacent channel leakage ratio at 10MHz offset. To the best of our knowledge, the drain efficiency of 60.4% is the highest efficiency at 2.6GHz frequency for a WiMAX signal with 8.3dB PAPR.

In order to meet the requirements of high efficiency and broadband for the wireless communication system, a high efficiency and broadband gallium nitride power amplifier (PA) is designed and verified. Using the step-matching structure, its bandwidth has been improved. Furthermore, its input matching network is constructed by connecting several microband lines serially to reduce the matching Q value. Meanwhile, the harmonic control network is designed as the output matching network, which is built by a quarter-wave (λ/4) line open circuit and short circuit microwave lines in parallel. Thus, its drain efficiency (DE)can be improved. This design is simulated and tested at 2.2–3 GHz with the gallium nitride (GaN) process. After measuring, it attains an output power (Pout) of 39.5–41.5 dBm, Gain of 10.5–12.5 dB, DE of 65.1%–78.3% with power added efficiency (PAE) of 64.8%–76.2%.

This paper presents a Doherty power amplifier (DPA) controlled by the optimized bi-level supply modulator to improve an overall efficiency. By utilizing the supply modulation method determined by the probability density function (PDF) of an interest signal, an estimated average efficiency can be improved as much as 8.5 % compared with that of conventional DPA. For the verification the proposed DPA using commercial 120 W GaN devices has been devised. The experimental results show that the proposed DPA delivers a drain efficiency (DE) of 53.8 % and power added efficiency (PAE) of 50 %, with a gain of 11.8 dB at an average output power of 34.7 W for a 2.65 GHz 10 MHz 3G LTE signal with a 9 dB peak-to-average power ratio (PAPR). The measure result reveals that the DE of proposed DPA is 6 % higher than that of conventional one.

This paper presents a new class of power amplifier (PA) - Class-iF- <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> - resolving the highly nonlinear double inflection characteristics in the conventional Class-F- <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> PA. It is illustrated that, by properly terminating the second harmonic source impedance Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2S</inf> from conventional short-circuit to open-circuit, the double inflection nonlinear gain profile can be mitigated in the proposed Class-iF- <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> PA, wherein the same saturation output power is achieved with less gain compression without drain efficiency trade-off. The idea was validated with source/load-pull and a broadband prototype operating from 2.0 to 2.6 GHz was designed using a commercial 10-W Gallium Nitride (GaN) transistor. Under continuous wave (CW) signal test, the proposed Class-iF- <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> PA can achieve 40.1-40.8-dBm output power, 71.2%-77.3% drain efficiency (DE) and 67.4%-74.1 % power added efficiency (PAE) at 3-dB gain compression level over 2.0-2.6 GHz.

In this paper, a 3.2–3.6 GHz two-stage Doherty power amplifier (PA) module is proposed for fifth-generation (5G) massive multiple-input multiple-output (MIMO) base stations. A detailed design method and procedure for a compact and low-loss combiner suitable for the Doherty PA module are introduced. Based on the proposed combiner, a Doherty PA module is implemented using gallium nitride (GaN) transistors and surface-mounted devices (SMDs) with a packaged size of 8 × 8 mm2. The proposed two-stage Doherty PA module achieves a 3 dB small-signal bandwidth of 3.1–3.9 GHz and a peak gain of 31.7 dB. From 3.2 to 3.6 GHz, the saturated output power is 40.4–41.1 dBm. Moreover, the measured saturated drain efficiency (DE) and 8 dB power back-off (PBO) DE reach 51–56.6% and 45.5–48.6%, respectively.

This letter presents an approach to maximize the output power and efficiency of a Doherty power amplifier (PA). The conventional carrier PA having match, used in a symmetric Doherty PA, does not deliver the saturated high efficiency at the 6 dB back-off power but at the 5.5 dB back-off power due to the knee voltage effect. To solve the problem, the gate biases of the carrier and peaking PAs are adapted. The gate bias voltage of the carrier PA is optimized for a higher peak output power, delivering a 3 dB larger peak power at match. That of the peaking PA is also optimized to have the same peak power of the carrier PA. A Doherty PA with the concept is designed using a 45 W gallium nitride (GaN) high electron mobility transistors (HEMT) for the carrier and peaking cells at 1.94 GHz. The measured average output power, drain/power-added efficiencies and gain are 44.35 dBm, 60.5/57.2%, and 12.75 dB for a 10 MHz long term evolution (LTE) signal with a 6.5 dB peak-to-average power ratio (PAPR).