Dual-band Doherty Power Amplifier Research Articles

Design of a Dual-Band Load-Modulated Sequential Amplifier with Extended Back-off

This letter presents a dual-band load-modulated sequential amplifier (LMSA). The proposed amplifier changed the attenuator terminated at the isolation port of the four-port combiner of the traditional sequential power amplifier (SPA) architecture into a reactance modulation network (RMN) for load modulation. The impedance can be maintained pure resistance by designing RMN, thus realizing high efficiency and a good portion of the output power in the multiple bands. Compared to the dual-band Doherty power amplifier with a complex dual-band load modulation network (LMN), the proposed LMSA has advantages as maintaining high output power back-off (OBO) efficiency, wide bandwidth and simple construction. A 10-watt dual-band LMSA is simulated and measured in 1.7-1.9 GHz and 2.4-2.6 GHz with saturated efficiencies 61.2-69.9% and 54.4-70.8%, respectively. The corresponding 9 dB OBO efficiency is 46.5-57.1% and 46.4-54.4%, respectively.

Dual-Band Dual-Output Four-Way Doherty Power Amplifier for Unsynchronized Time-Division Duplexing

This article proposes a dual-input dual-output dual-band four-way Doherty power amplifier (DPA) architecture, capable of linearized operation at one frequency band without being disturbed by arbitrary load switching at the other frequency band. The proposed technique is demonstrated through the design, implementation, and measurement of a prototype circuit operating at 1.85-and 2.65-GHz bands with 70-MHz bandwidth for each band. The prototype dual-band DPA (DB-DPA) achieves a peak output power of 49.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 0.2 dBm for the 1.85-GHz band and 49.3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 0.5 dBm for the 2.65-GHz band. Furthermore, the measured drain efficiency at 9-dB power back-off (PBO) is 59%–64% and 60%–65% for the 1.85-and 2.65-GHz bands, respectively. Concurrent dual-band performance, dynamic power sharing capability, and utility of the proposed DB-DPA in unsynchronized time-division duplexing (TDD) applications are demonstrated by using 20-MHz new radio (NR) signals with 9-dB peak-to-average power ratio (PAPR). For an average output power of 39 dBm per band, the concurrent dual-band measurement yields 49% average drain efficiency and better than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 48-dBc adjacent channel leakage ratio (ACLR).

Dual-Band Dual-Output Doherty Power Amplifier for Unsynchronized Time-Division Duplexing

Conventional multiband power amplifiers (PAs), when working in time-division duplex (TDD), require the transmit–receive intervals of all bands to be synchronized. This is an undesirable constraint in modern radio base stations. This article proposes a dual-output dual-band Doherty PA (DB-DPA) that enables the loading of one band to be switched on-and-off without impacting the other band in normal transmission. A thorough analysis of the proposed dual-output DB-DPA architecture is presented, and a dual-output DB-DPA prototype operating at 1.4 and 2.6GHz has been designed as a proof of concept. The large-signal measurements of the prototype DB-DPA indicate Doherty behavior at both frequencies with over 56% saturation efficiency and 45% efficiency at 6-dB power back-off (PBO). Furthermore, single-band and concurrent dual-band linearized modulated measurements, using 10-MHz new radio (NR) signals with 6-dB peak-to-average power ratio (PAPR), demonstrate the linearizability of the proposed DB-DPA and its usefulness for unsynchronized TDD applications.

High-Efficiency Dual-Band Filtering Doherty Power Amplifier Based on Multi-Function Circuit

This article presents a high-efficiency dual-band filtering Doherty power amplifier (DPA) using multi-function circuits for simplifying the structure. A dual-band filtering power combiner also plays the role of real-to-real impedance matching, in which one resonator is shared by both the power combing and filtering circuits. Thus, only one extra resonator is needed for the power combiner to provide second-order dual-band filtering responses, which contributes to high efficiency of the DPA. Transmission zeros are generated between the two passbands, realizing a sharp roll-off rate and greatly enhancing the isolation between the two passbands. Meanwhile, an impedance control network is designed to simultaneously suppress the harmonics and transform the optimized complex impedance desired by the transistor to a real one. In this way, the output matching network and extra filter in conventional design are realized by the filtering power combiner and impedance control network in the proposed design, resulting in a simpler structure. A dual-band DPA operating at 2.14 and 2.6 GHz is implemented with the measured peak efficiencies of 64.4&#x0025; and 69&#x0025; at the output power of 43.25 and 43.3 dBm, respectively. The 6-dB back-off efficiencies are 50&#x0025; and 57&#x0025; at the two passbands. Under 20-MHz long term evolution (LTE) modulated signals with a peak-to-average power ratio (PAPR) of 7.5 dB, the DPA after digital predistortion (DPD) is measured with an adjacent channel leakage ratio (ACLR) of better than &#x2212;45.2 dBc and the efficiencies of 51.6&#x0025; and 54.3&#x0025; at interested bands. The peak efficiency under the excitation of the concurrent modulated signal is 48.6&#x0025;.

A concurrent 2.6/3.5GHz dual-band Doherty power amplifier with matching network based on composite right/left-handed unit cell

A concurrent 2.6/3.5GHz dual-band Doherty power amplifier with matching network based on composite right/left-handed unit cell

A Fully Integrated 3.5-/4.9-GHz Dual-Band GaN MMIC Doherty Power Amplifier Based on Multi-Resonant Circuits

In this article, a fully integrated dual-band gallium nitride (GaN) Doherty power amplifier (DPA) based on multi-resonant circuits (MRCs) is presented. A lumped T-type network in combination with the output capacitances of the main and auxiliary transistors is able to realize the quarter-wavelength transformer (QWT) in DPA, and its component values are totally decided by the operating frequency, given a certain characteristic impedance. MRCs are proposed to exhibit the required component values at two different frequencies. By replacing each component in the T-type network with an MRC, a dual-band QWT can be achieved. An integrated dual-band DPA is implemented in a commercial 0.25- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> GaN-HEMT process to validate the proposed method. The fabricated DPA shows a saturated output power of 43.8–44.7/44.4–44.8 dBm, a 6-dB back-off drain efficiency (DE) of 41%–46%/41.5%–47%, and a saturated DE of 49%–52%/56%–59% in 3.35–3.6/4.8–5.2 GHz, with a compact size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.8\times3.5$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Applying a 100-MHz OFDM signal with a 7.8-dB peak-to-average power ratio (PAPR), an average efficiency of 37%/40% and an average power of 37/37 dBm are measured at 3.5/5.0 GHz, and the adjacent channel power ratio (ACPR) is better than −49 dBc after digital predistortion (DPD). To the best of our knowledge, the proposed DPA is the first demonstration of fully integrated dual-band GaN DPAs.

A Novel 3-Way Dual-Band Doherty Power Amplifier for Enhanced Concurrent Operation

This article presents the architecture and design methodology for a new type of dual-band Doherty power amplifier (DB-DPA), referred to as 3-Way DB-DPA, which consists of a main amplifier for each band and an auxiliary amplifier handling both bands. The 3-Way DB-DPA improves the average drain efficiency in concurrent dual-band operation compared to the traditional 2-Way DB-DPA, by avoiding early clipping in the main amplifiers, while benefiting from load—pulling from the auxiliary power amplifier (PA). This improvement is verified in theory and simulation at the current-source reference planes and in measurement with a fabricated 1.5- and 2-GHz dual-band PA. A statistical analysis using 2-D continuous-wave (CW) signals with long-term evolution (LTE) probability distribution functions (PDFs) is performed and demonstrated an improvement in the concurrent average efficiency by 15 percentage points compared to the conventional 2-Way DB-DPA. In nonconcurrent operation, the measured CW drain efficiency in the lower band (1.5 GHz) is 82.8% at peak and 66.6% at 9.6-dB backoff, and the measured CW drain efficiency in the upper band (2.0 GHz) is 70.0% at peak and 48.4% at 9.4-dB backoff. The CW concurrent-balanced drain efficiency reaches 66.2/52.0% in the 3-Way DB-DPA at 3-/6-dB backoff. In single-band operation at 1.5/2.0 GHz, the average power and average drain efficiency after linearization by digital predistortion (DPD) are 35.1/37.4 dBm and 65.0/53.7%, respectively, for an LTE signal with 10-MHz bandwidth and 6.1-dB peak-to-average power ratio (PAPR). In concurrent operation, the 3-Way DB-DPA is driven by two 10-MHz LTE uncorrelated signals at 1.5 GHz with 6.86-dB PAPR and at 2.0 GHz with 6.26-dB PAPR, and the average total power and average concurrent drain efficiency after DPD are 37.5 dBm and 54.24%, respectively.

Dual-band doherty power amplifier with improved reactance compensation

In brief, a dual-band doherty power amplifier employing reactance compensation with gallium nitride high-electron-mobility transistor technology is discussed. This design is developed for long-term evolution (LTE) frequency operation, particularly for the application of two-way radio to improve the efficiency at the back-off point from saturation output power for selected dual frequencies in the LTE bandwidth. Measurements show that the prototype board has enhanced performance at the desired frequencies, namely a saturation output power of 40.5 dBm, and 6 dB back-off efficiencies of 43% and 47%, which exhibit a gain of approximately 10 dB at 0.8 GHz and 2.1 GHz, respectively.

Linearity improvement of a dual-band Doherty power amplifier using E-CRLH transmission line

A dual-band Doherty power amplifier (DB-DPA) using the extended composite right and left handed transmission lines (E-CRLH TL) is proposed. In this structure the λ/4 transmission lines are replaced with open-ended E-CRLH TL. The power amplifier exhibits dual-band property at f1=2.5GHz, f2=3.4GHz input frequencies and suppresses the second harmonics (2f1, 2f2) at the amplifier output. The simulation studies show that the second harmonic and second order intermodulation (IM2) of the proposed DB-DPA are improved compare to the conventional DPA. This improvement is obtained because of the quad band property of E-CRLH transmission lines. Then, the proposed DB-DPA is examined using various multi tones signals. The better ACPR and efficiency are achieved compare to the conventional Doherty power amplifiers. The measurement results confirm the accuracy of the simulation results.

Novel Dual-Band Equal-Cell Doherty Amplifier Design With Extended Power Back-Off Range

In this article, for the first time, a new and generalized design methodology for dual-band Doherty power amplifier (DPA) is presented. Owing to the adoption of equal-cell architecture and extended power output back-off (OBO > 6 dB) operation, the conventional dual-band impedance-transformer approach cannot be applied. Because of this, a novel output combiner is proposed for the provision of load modulation at two widely spaced frequency bands. For verification, a 9-dB-OBO DPA with 1.4- and 3.5-GHz operating frequencies is designed and fabricated. Simulation and measurement results indicate excellent Doherty efficiency behavior with back-off (9 dB) efficiency of over 55% and saturation efficiency of over 68% at both frequencies. Under 9-dB-peak-to-average power ratio (PAPR) WCDMA signal excitation, average efficiency of 52.1% and 51.3% is achieved at 1.4 and 3.5 GHz, respectively.

A Compact Ka/Q Dual-Band GaAs MMIC Doherty Power Amplifier With Simplified Offset Lines for 5G Applications

In this paper, a Ka/Q dual-band Doherty power amplifier (DPA) with simplified offset lines is implemented in a 0.1-μm gallium arsenide (GaAs) process. It is found that the dual-band transmission lines (TLs) employed in the sub-6-GHz dual-band DPA are not suitable to be used as the offset lines in millimeter-wave (mm-wave) dual-band DPAs due to their large sizes and insert losses. An in-depth analysis reveals that the phase requirement of the offset lines can be relaxed, and the DPA exhibits a reasonable performance in a certain phase-shift range. A novel design method is proposed to realize offset lines using simple TLs, which can satisfy the phase-shift ranges in dual bands by choosing a proper electrical length. To enhance the gain of the DPA, a reversed uneven power splitter is adopted to deliver more power to the main power amplifier (PA). The fabricated DPA achieves an output power of 25.4/25.2 dBm, a peak power-added efficiency (PAE) of 33%/25%, and a 6-dB back-off PAE of 22%/17% at 29/46 GHz, respectively, with a compact size of 2.2 1.4 mm2. Applying a 20-MHZ 64-quadraticamplitude modulation (QAM) signal with a 7.7-dB peak-toaverage power ratio (PAPR), the measured average output power, PAE, and error vector magnitude (EVM) at 29/46 GHz are 18.4/19 dBm, 17%/15%, and 1.5%/1.1% after linearization, respectively. To the best of our knowledge, the proposed DPA is the first demonstration of mm-wave dual-band DPAs that do not require any additional switching or reconfiguration.

Design of Concurrent Dual-Band Continuous Class-J Mode Doherty Power Amplifier With Precise Impedance Terminations

In this letter, a novel methodology for designing concurrent dual-band continuous class-J mode Doherty power amplifier (DPA) with precise impedance terminations is presented. First, the required impedance condition of the carrier amplifier which operates in continuous class-J mode at the back-off region is analyzed in detail. Based on the proposed theory, the fundamental impedance is realized by taking advantage of the noninfinity output impedance of the peaking stage, then the second harmonic impedance is realized with a harmonic tuning postmatching network. A 1.8-/2.6-GHz dual-band DPA employing commercial GaN devices is designed and implemented to validate the proposed method. The fabricated DPA can achieve 68.5% and 75% drain efficiencies (DEs) for saturated power level at 1.8 and 2.6 GHz, respectively. For the 6-dB back-off region, the measured DEs are 64% and 63% at the two designed frequencies.

A Novel Dual-Band Concurrent Asymmetric Doherty Power Amplifier for Wireless Communications

In this paper, a different dual-band asymmetric Doherty power amplifier (ADPA) with a novel dual-band bandpass filter (DBBPF) with quad-section stepped impedance resonators (SIRs) is presented. This specific DBBPF rejects the annoying frequencies of the second and third harmonics in the dual-band and contributes considerably to performance improvement of ADPA. This structure is confirmed with the design, simulation, implementation and testing of a 10 W GaN-based ADPA for global system for mobile communications (GSM) and worldwide interoperability for microwave access (WiMAX) applications at 1.84 and 3.5[Formula: see text]GHz, respectively. In the measurement results, the ADPA defines a drain efficiency (DE) of 63.7% with an output power of 35[Formula: see text]dBm and power gain is 14.2[Formula: see text]dB, and a DE of 47.5% with an output power of 34.5[Formula: see text]dBm and power gain is 10.4[Formula: see text]dB at the 9[Formula: see text]dB output power back-off (OBO) from the saturated output power in the two frequency bands. Linearity effects, applying 10[Formula: see text]MHz 16 QAM signal and a 5[Formula: see text]MHz WiMAX signal, display an adjacent channel leakage ratio of [Formula: see text] and [Formula: see text][Formula: see text]dBc with the average output power of 36.8/36[Formula: see text]dBm at 1.84/3.5[Formula: see text]GHz, respectively.

A Digitally Assisted Dual-Input Dual-Band Doherty Power Amplifier With Enhanced Efficiency and Linearity

This brief presents a dual-input dual-band Doherty power amplifier (DPA) that operates at 850 and 2100 MHz. The presented DPA utilizes a compact input matching network and composite right-left handed phase offset line. This DPA delivers a peak output power of around 44.5 dBm with an efficiency enhancement region upto 9–10 dB output power back off at both the operating frequencies. Further, the phase offset angles between main and auxiliary power amplifiers are controlled digitally at both the operating frequencies in order to improve the efficiency and linearity throughout the back-off region. As compared to the conventional phase offset of 90°, the optimum offset angle of 120° at 850 MHz provides an improvement of 13% in drain efficiency and 8.5 dB in C/IMD3. Similarly, an improvement of 4 dB in C/IMD3 is achieved by digitally setting a phase offset of 80° at 2100 MHz.

A postmatching concurrent dual-band Doherty power amplifier with enhanced bandwidth

In this article, a postmatching concurrent dual-band (C-DB) Doherty power amplifier (DPA) is proposed to enhance the bandwidth in each frequency band. The relationship between the phases of carrier and peaking impedance inverting networks (IINs) and the bandwidth of the C-DB DPA is analyzed for the first time. By designing the carrier and peaking IINs with appropriate minimum phase delays, the bandwidth of C-DB DPA can be enhanced and balanced in both frequency bands. Based on postmatching technique, load impedance at the combining point is optimized by comparing the DPA's bandwidth at back-off and saturation. A high-efficiency C-DB DPA working at 2.0-2.4 and 3.2-3.6 GHz (400 MHz bandwidth each) is designed and fabricated based on commercial gallium nitride HEMTs to validate the proposed technique. Measurement results show that the DPA has a 6 dB back-off efficiency of 54%-57% and a saturated efficiency of 70%-71% at 2.0-2.4 GHz. At 3.2-3.6 GHz, the efficiency of 52%-55% at 6 dB back-off and 65%-71% at saturation can be obtained. Modulated signals are also employed to excite the DPA at the two bands. The DPA can achieve an average efficiency of more than 47% at 7 dB back-off with excellent linearity by utilizing digital predistortion.

Concurrent dual-band Doherty power amplifier using a novel dual-band bandpass filter for wireless technologies

This paper proposes a novel design methodology for dual-band Doherty power amplifier (DPA) with a novel dual-band bandpass filter and quad-section stepped impedance resonators. This design rejects ...

Systematic Crest Factor Reduction and Efficiency Enhancement of Dual-Band Power Amplifier Based Transmitters

A systematic design methodology including novel crest factor reduction (CFR) and power amplifier (PA) efficiency enhancement techniques for concurrent dual-band transmitters is proposed to improve performance under concurrent modulated stimulus, in terms of both efficiency and output power. Conventional energy efficient PAs are typically implemented separately in analog circuit or digital signal domains. However, the proposed method combines a digital domain 2-D power distribution reshaping (2-D-PDR) method to adaptively reshape the signals’ distribution to fit the target PA’s characterization and an analog domain inter-modulation tuning design to enhance the PA’s output capability. Based on the proposed method, an example of concurrent dual-band Doherty PA (DPA) working at 1.9–2.6 GHz LTE bands was designed using two 10-Watt GaN HEMTs. A 2-D-PDR procedure was developed for the designed DPA. The fabricated DPA was measured in concurrent mode under the stimulus of a pair of 10 MHz LTE signals. According to the measured results, the proposed DPA achieved a drain efficiency of 46.6% at an output power of 6.2 W while maintaining a good adjacent channel power ratio and error vector magnitude. To the best of the authors’ acknowledge, this is the state-of-the-art performance for concurrent dual-band PAs. Additionally, measurements are performed on three varied type of PAs using the proposed 2-D-PDR. According to the measured results, about 0.3~0.8 dB power improvement and 1.5%~3% efficiency improvement can be achieved using the proposed 2-D-PDR compared with the conventional 2-D-CFR, proving the feasibility of the proposed technique.

Co‐design of two‐way doherty power amplifier and filter for concurrent dual‐band application

ABSTRACTIn this letter, an architecture is presented to solve problems of classical concurrent dual‐band Doherty power amplifiers (DPAs) and its design procedure is given. It is a codesign of two single‐band DPAs and four filters. Two of filters at the output port are used for impedance transformation, harmonic components suppressing and signal isolating, while the another two split concurrent dual‐band signals at the input port. In this way, intermodulation components of the two bands can be effectively suppressed and each band can achieve a good performance as single‐band one's. This design concept is demonstrated through implementing of a practical dual‐band DPA operating at 1.8 and 2.5 GHz. Measurement results show that efficiencies are 65.0 and 56.3% at the 6 dB output power back‐off for concurrent application. The intermodulation components and harmonic components are lower than −40 dB except second harmonic component at 1.8 GHz (−32 dB). © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:530–533, 2017

Reconfigurable and Concurrent Dual-Band Doherty Power Amplifier for Multiband and Multistandard Applications

This paper proposes a design scheme of concurrent dual-band Doherty power amplifier (DPA) which can be reconfigured to two different pairs of concurrent dual bands for multiband and carrier aggregation applications. In addition to the reconfiguration of frequencies of operation, the output power back-off (OPBO) region for efficiency enhancement can also be reconfigured in this DPA. As a proof of concept, a reconfigurable and concurrent dual-band DPA is designed to operate at 1500 and 2140 MHz in the first concurrent dual band, whereas on reconfiguration it will operate concurrently at 1850 and 2350 MHz. While operating in the first concurrent dual band, the DPA has an enhanced efficiency region up to 6-dB OPBO level and, after reconfiguration to the second concurrent dual band, this region extend up to 9-dB OPBO level. The proposed DPA is tested using continuous wave (CW) signals in single mode as well as in concurrent mode. Measurement results using CW signals in single mode reveal a drain efficiency of 52%-56% at 6-dB OPBO in the first concurrent dual band. Similarly, in the second concurrent dual band, a drain efficiency of 43%-48% is achieved at around 9-dB OPBO. The peak drain efficiency at saturation is better than 60% in all the four operating bands. The measured aggregated drain efficiencies are 49% and 44% in the first and second concurrent dual bands for 6 and 9 dB OPBO level, respectively. The measured carrier to the third-order intermodulation distortion is better than 17 dBc for all of the operating bands.

Preparing Linearity and Efficiency for 5G: Digital Predistortion for Dual-Band Doherty Power Amplifiers with Mixed-Mode Carrier Aggregation

As new wireless communication standards seek to meet the myriad demands of today's end users, the traditional RF transmitter chain is faced with an evolving set of challenges. To maximize information throughput, signal bandwidths are continuously growing. In fourth-generation longterm evolution-advanced (also called LTE-A), for example, to meet the stated goals of 1-Gb/s downlink and 500-Mb/s uplink speeds, the carrier aggregation (CA) technique was introduced, expanding the maximum transmit bandwidth up to 100 MHz [1]. With mobile traffic expected to increase by a factor of 1,000 over the next decade, future fifth-generation (5G) systems will continue to place new demands on the transmit chain [2].