Dual-band Power Amplifier Research Articles

A Harmonic Termination Technique for Single- and Multi-Band High-Efficiency Class-F MMIC Power Amplifiers

This paper presents a harmonic termination technique for single- and multi-band high-efficiency class-F monolithic microwave integrated circuit (MMIC) power amplifiers (PAs). The harmonic termination network (HTN), realized with the minimum possible number of elements, can be used to terminate an arbitrary number of harmonics in a single-band PA or harmonics of multiple frequencies in a concurrent multi-band PA. The drain and gate bias lines are embedded in the HTNs to obviate the need for RF chokes and reduce the chip area. A single- and a dual-band MMIC PA are designed using the proposed technique and implemented in a 0.25- μm AlGaAs-InGaAs pHEMT technology. The single-band 5.5-GHz PA provides 27.5 dBm of output power with 70% power-added efficiency (PAE). This PAE level is achieved by terminating the first five harmonics at the output as well as the first three harmonics at the input of PA. The dual-band PA, operating at 5 and 12 GHz, delivers the output power of 28.0 and 26.7 dBm with PAE of 58% and 51%, at the two frequency bands, respectively.

RFID 대역에서 동작하는 이중 대역 전력증폭기 설계

본 논문은 910 MHz와 2.45 GHz 대역에서 동작하는 RFID 트랜시버용 전력증폭기를 설계 및 제작하였다. 제안된 이중 대역 전력증폭기는 집중정수 소자로 구현된 910 MHz 대역의 정합 회로와 분포정수 소자로 구현된 2.45 GHz 대역의 정합 회로로 구성되며, 두 대역의 격리를 위하여 910 MHz 대역에 대하여 대역 제거 필터(band rejection filter)로 동작하고, 2.45 GHz 대역에서는 대역 통과 필터(band pass filter)로 동작하는 <TEX>${\lambda}/2$</TEX> 직렬 마이크로스트립 전송 선로로 구성되어 있다. 제작된 이중 대역 전력증폭기는 910 MHz와 2.45 GHz에서 이득이 각각 8 dB와 1.5 dB를 나타냈으며, 입력 전력 10 dBm을 인가하여 얻은 출력 전력은 두 대역 모두 20 dBm을 얻었다. In this paper, we designed more improving a dual-band power amplifier than the transceiver of RFID reader that operates at 910 MHz and 2.45 GHz. A dual-band power amplifier has two circuits. One matching circuit is composed lumped element in the band of 910 MHz. The other matching circuit using distributed element in the high band of 2.45 GHz. So, this dual-band power amplifier works as Band Rejection Filter in the band of 910 MHz but in the high band of 2.45 GHz works as Band Pass Filter. Therefore, this is composed a microstrip transmission line. A power amplifier is showed gains of 8 dB output power at 910 MHz and 1.5 dB output power at 2.45 GHz. If input power is 10 dBm, both of bands output 20 dBm.

Baseband Equivalent Volterra Series for Digital Predistortion of Dual-Band Power Amplifiers

This paper proposes a new dual-band baseband equivalent (BBE) Volterra model devised to predict the behavior of dual-band power amplifiers (PAs) and/or to linearize their response. A series of derivations were applied to the original continuous passband Volterra-series expression to uncover a simple formulation that related the BBE envelopes of the output signals in each band to those at the input in the discrete domain. This yielded an inherently low-complexity dual-band Volterra-series model that does not require the empirical pruning commonly applied to the low-pass equivalent Volterra series. The proposed model was successfully applied to digitally predistort and linearize a dual-band 45-W class-AB GaN PA driven with different dual-band dual-standard test signals. For each band, the model necessitated less than 25 coefficients to reduce the adjacent channel leakage power ratio ACLR by up to 25 dB.

A Concurrent Dual-Band Uneven Doherty Power Amplifier with Frequency-Dependent Input Power Division

A concurrent dual-band uneven GaN Doherty power amplifier (PA) for two wide-spacing frequencies application is proposed in this paper. To avoid an early load modulation-drop caused by the soft turn-on characteristic of the peaking device, an adaptive power division is realized by a frequency-dependent uneven power divider as well as the input matching nonlinearities of the two cells in Doherty PA. Due to the adaptive power division, the proposed dual-band uneven Doherty PA achieves a power-added efficiency of 45% and 41% at the 6 dB backoff from the saturation at 850 MHz and 2330 MHz, respectively, the gain of the proposed Doherty PA is also enhanced to 19 dB and 13 dB in the dual bands. Furthermore, a more accurate two-dimensional joint digital predistortion model (2D-JDPD) is applied to linearize the PA and compensate for the in-phase and quadrature (I/Q) imbalance simultaneously. With this new model, the adjacent channel power ratio (ACPR) is improved to better than -47.1 dBc and -49.4 dBc in the lower and upper bands at an average output power of 31.75 dBm, and a drain efficiency of 26.7% is obtained at the same time.

Genetic-based Design of Harmonic-tuned Dual-band GaN HEMT Power Amplifier

Abstract The design of a harmonic-tuned dual-band GaN HEMT power amplifier (1.28 GHz and 2.14 GHz) is presented. To increase the output power and efficiency, the transistor's load impedance at the fundamental frequency, second and third harmonics have been optimally selected. In order to design the output matching network, a new genetic-based software system for automatic synthesis of passive networks has been used. The measured performances of the dual-band amplifier are as follows: Pout = 37.28 dBm, G = 11 dB, PAE = 42.1% at f1 = 1.28 GHz; Pout = 35.7 dBm, G = 9 dB, PAE = 23.7% at f2 = 2.14 GHz.

1.7/2.6 GHz high‐efficiency concurrent dual‐band power amplifier with dual‐band harmonic wave controlled transformer

A 1.7/2.6 GHz high-efficiency concurrent dual-band power amplifier (DBPA) with a dual-band harmonic wave controlled transformer is demonstrated. The proposed dual-band transformer, which transfers the fundamental and the second harmonic impedances of each frequency, is directly transmission line implemented with the help of an optimisation algorithm. The measurement results show that the proposed DBPA has performances of 70 and 64% power added efficiency with an 11 dB gain and a 41 dBm output power at 1.7 and 2.6 GHz, respectively. Its average drain efficiency is more than 42% and the adjacent channel leakage ratios are lower than -46 dBc at both frequencies with the digital predistortion adjustment for a 5 MHz WCDMA signal input.

Novel Dual-Band Matching Network for Effective Design of Concurrent Dual-Band Power Amplifiers

In this paper, a systematic approach to the synthesis of a novel dual-band matching network is proposed and applied to design a dual-band power amplifier (PA) capable of maintaining high power efficiency at two arbitrary, widely spaced frequencies. The proposed network incorporates two different stages. The first one transforms the targeted complex impedances, at the two operating frequencies, to a real one. The second stage is a dual band filter that ensures the matching of the former real impedance to the termination impedance. An additional transmission line is incorporated between the two stages to adjust the impedances at the second and third harmonics without altering the impedances seen at the fundamental frequencies. The harmonic termination control is very effective in enhancing the efficiency of radio frequency transistors, especially when exploiting the Class J design space. The proposed dual-band matching network synthesis methodology was applied to design a dual band PA using a packaged 45 W Gallium Nitride (GaN) transistor. The PA prototype maintained a peak power efficiency of about 68% at operating frequencies of 800 MHz and 1.9 GHz. In addition, a Volterra based digital pre-distortion technique was successfully applied to linearize the PA response around the two operating frequencies.

Characterization of Concurrent Dual-Band Power Amplifiers Using a Dual Two-Tone Excitation Signal

A method to characterize the memory effects in a nonlinear concurrent dual-band transmitter is presented. It is an extension of the conventional two-tone test for power amplifiers to concurrent dual-band transmitters. The output signal of a concurrent dual-band transmitter is affected not only by intermodulation (IM) products but also by cross-modulation (CM) products. In one frequency band, the transmitter is excited by a two-tone signal which frequency separation is swept. In the second band, the transmitter is concurrently excited by another two-tone signal with slightly wider frequency separation. The frequency difference of the two signals is fixed during the frequency sweep. The two-tone test is made at different power levels. The upper and lower third-order IM and CM products are measured. The asymmetry between the upper and lower third-order IM and CM products are measures of the transmitter's memory effects. The measurement results show that the memory effects are more dominant in the third-order IM products than in the CM products. An error analysis and system calibration was performed and measurement results for two different devices are presented.

Enhanced Analysis and Design Method of Concurrent Dual-Band Power Amplifiers With Intermodulation Impedance Tuning

The behavior of power amplifiers (PAs) driven by concurrent dual-band signals is analyzed theoretically in this paper. According to the analysis, the impedance matching at intermodulation (IM) frequency is very important for PAs working in concurrent mode. Based on the concept of IM impedance tuning, a family of new operation modes can be introduced, including concurrent Class-A, Class-AB, Class-B, and Class-C. The theoretical performance of these modes are derived and the overdrive effects of them are also discussed. A possible structure is proposed to implement the proposed IM impedance tuning, and a concurrent Class-AB dual-band example PA operating at 1.9-2.6-GHz long-term evolution (LTE) bands is demonstrated. Experimental results show good consistence with the theoretical analysis, and the concurrent Class-AB PA prototype exhibits higher than 36.1% power-added efficiency in concurrent mode when driven by 10- and 15-MHz LTE signals in two bands concurrently. To our best knowledge, this is the state-of-the-art efficiency performance of concurrent dual-band PAs, even higher than previously reported dual-band Doherty PAs. Additionally the proposed PA, which is fabricated using a 10-W GaN HEMT, can output more than 34.3-dBm power with a peak-to-average ratio of 7 dB in concurrent mode, showing a remarkable power utilization factor for concurrent dual-band PAs.

Realization of a 30-W highly efficient and linear reconfigurable dual-band power amplifier using the continuous mode approach

This paper presents the design methodology and the realization of a highly linear and power-efficient reconfigurable dual-band amplifier based on the continuous/Class-ABJ approach. The Class-ABJ theory allows presenting different reactive solutions on both fundamental and second harmonic terminations compared with the standard Class-AB mode. Despite the various terminations, a constant optimum output performance in terms of power, gain, and efficiency can still be achieved. The output impedances are then translated into frequency thus allowing the realization of broadbandpower amplifiers(PAs) at high-power level of 30 W. In this work, the Class-ABJ broadband approach will be used for the realization of a reconfigurable dual-band power amplifier operating in the two frequency bands 2.1–2.2 and 2.5–2.6 GHz. Continuous wave (CW) measurements on the realized PA show power and efficiency greater than 17 W and 55% in the two frequency bands with peak values up to 30 W and 63.7%. Indeed, it is shown that such novel modes can be predistorted and therefore the linearity requirement can also be met.

On the Modeling and Linearization of a Concurrent Dual-Band Transmitter Exhibiting Nonlinear Distortion and Hardware Impairments

This paper proposes a novel, complexity-reduced, dual-input, two-box model for the modeling and digital predistortion of a dual-band power amplifier (PA) in the presence of in-phase/quadrature (I/Q) modulator imperfections. The model is composed of two cascaded nonlinear blocks. The first block is implemented as a mildly nonlinear dual-input truncated Volterra filter, which includes second-order cross-terms for the mutual characterization of the dynamic mildly nonlinear memory effects exhibited by the dual-band PA and for the compensation of I/Q imperfections. The second block is implemented as a two-dimensional look-up table for the characterization of the static nonlinearity of the dual-band PA. The proposed model was evaluated through the excitation of the dual-band Doherty PA by two concurrent multi-carrier signals, applied at 880 MHz and 1978 GHz, in the presence of I/Q modulator imperfections. The experimental results showed the accurate performance of the proposed model in suppressing the adjacent channel error power, when compared to other state-of-the-art models, the computational complexity of the proposed model was significantly reduced, which economizes the resources utilized by the model for implementation on a digital signal processing/field-programmable gate array platform.

New Technique for Synthesizing Concurrent Dual-Band Impedance-Matching Filtering Networks and ${\hbox{0.18-}}\mu{\hbox {m}}$ SiGe BiCMOS 25.5/37-GHz Concurrent Dual-Band Power Amplifier

New technique for synthesizing concurrent dual-band impedance-matching filtering networks is presented. The technique enables the design of concurrent dual-band impedance-matching filtering networks that provide not only simultaneous matching of two arbitrary loads to two arbitrary sources at two different frequencies, but also dual-bandpass filtering response capable of suppressing unwanted signals like the harmonics and inter-modulation products in nonlinear circuits, such as power amplifiers (PAs). A new 0.18-μm SiGe BiCMOS concurrent dual-band PA was designed based on the developed dual-band matching filtering technique around 25.5 and 37 GHz, which works in the concurrent dual-band mode (25.5 and 37 GHz), as well as single-band mode (25.5 or 37 GHz). The measured results show that, in the single-band mode, the dual-band PA exhibits gain of 21.4 and 17 dB, maximum output power of 16 and 13 dBm, and maximum power-added efficiency (PAE) of 10.6% and 4.9% at 25.5 and 37 GHz, respectively. In the dual-band mode, the maximum output power is 13 and 9.5 dBm at 25.5 and 37 GHz, respectively, and the total maximum PAE is 7.1%. The designed concurrent dual-band PA has a chip size of 1.3×0.68 mm2 and consumes a dc current of 120 mA from a 3-V supply voltage.

A Time Misalignment Tolerant 2D-Memory Polynomials Predistorter for Concurrent Dual-Band Power Amplifiers

This letter proposes a modified 2-D memory polynomial predistorter for concurrent dual band power amplifiers, which is tolerant to the time misalignment between the two bands. The new model is derived from the prior 2-D DPD model by substituting the interpolation expression into it. For performance validation, the proposed method is applied to a dual-band transmitter. In the presence of 4.87 samples time-misalignment existing between the two input signals, the proposed method achieves normalized mean square error of -40 dB and adjacent channel power ratio improvement of about 15 dB in the dual bands. Further experiment shows the proposed 2-D predistorter outperforms 2D-GMP in terms of complexity and signal quality.

Concurrent dual-band envelope tracking GaN PA design and its 2D shaping function characterization

This paper presents the design of a high-power dual-band power amplifier (PA) for envelope tracking (ET) operation and its characterization in concurrent dual-band ET operation modes. The design approach relies on the specific actual signal probability distribution and the prototype was conceived for the WCDMA 3GPP DL signals. The paper discusses the impact of the ET-shaping function influence on the linearity versus mean efficiency trade-off, for both single and concurrent dual-band cases. The technique was applied to a concurrent 870 and 2140 MHz ET-PA designed around a GaN HEMT device. The ET friendly design method led to performance very close to those observed at each single band. Over a bandwidth of 100 MHz and for PAR = 6.5 dB, the measured results reported a mean DE better than 71 and 54%, with a peak power higher than 55 and 54 dBm, at the two frequency bands, respectively. When evaluated in concurrent dual-band mode with two WDCMA signals at 6.5 dB PAR each, the ET-PA exhibited an estimated average total power of 49.5 dBm with 57.1% average drain efficiency.

Two‐dimensional crest factor reduction for performance improvement of concurrent dual‐band power amplifiers

A two-dimensional crest factor reduction (2D-CFR) is proposed to improve the performance of concurrent dual-band power amplifiers (PAs). Experimental measurements are performed on a 1.9-2.6 GHz concurrent dual-band LTE PA by using the proposed 2D-CFR and conventional 1D-CFR, respectively. Measured results after 2D digital predistortion (2D-DPD) show that the output power with the proposed 2D-CFR is increased by 10%, the efficiency is improved from 28.1 to 30.6% and the error vector magnitude is reduced from 3.46 to 2.67%, indicating a significant performance improvement.

Digital Predistortion for Concurrent Dual-Band Transmitters Using 2-D Modified Memory Polynomials

Cross-band modulation effects in the concurrent dual-band transmitters are quite noticeable for the linearization. This paper proposes a novel two-dimensional modified memory polynomial (2D-MMP) technique to compensate for nonlinear distortion in the concurrent dual-band transmitters. By taking into account the cross-band modulation effects, the 2D-MMP model is developed by properly modifying the envelope terms of the conventional memory polynomial (MP) model. This makes the model complexity of the 2D-MMP model significantly reduced compared to the prior 2D-DPD model in previous work. However, the linearization ability of the 2D-MMP model is still retained. Simulations prove that the 2D-MMP model is quite robust to different PA models. Experimental measurements were carried out for a dual-band class-AB PA exhibiting mild nonlinearity and a highly nonlinear dual-band Doherty PA. The results show that the 2D-MMP model can achieve nearly the same linearization accuracy compared to the 2D-DPD model, with much less coefficients. Less than -52 dBc adjacent channel power ratios (ACPRs) for the dual-band class-AB power amplifiers (PAs) and -50 dBc ACPRs for the dual-band Doherty PA in the dual bands were achieved.

Behavioral modeling for concurrent dual-band power amplifiers using 2D hammerstein/wiener models

Behavioral modeling for the concurrent dual-band power amplifier (PA) is a critical problem in practical applications. The nonlinear distortion in the concurrent dual-band PA is quite different from that in the conventional single-band PA. This article analyzes the nonlinearities in the concurrent dual-band PA and reveals that both input signals in the dual bands are important for the behavioral modeling. The 2D Hammerstein model and 2D Wiener model are proposed for the first time for the concurrent dual-band PA. They are extended versions of conventional Hammerstein and Wiener structures used in the single-band PA by including the cross-band intermodulation in the static nonlinearity block. The proposed 2D models require much less coefficients than the original work of the 2D-DPD model. Experiments were carried out for an 880 MHz/1960 MHz concurrent dual-band Doherty PA to demonstrate the effectiveness of the proposed models. The results clearly show that less than −40 dB normalized mean square errors (NMSEs) are obtained in the dual bands in the behavioral modeling. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 646–654, 2013.

Nonlinear characterization of concurrent dual-band RF power amplifiers

In this paper, the synchronous concurrent dual-band RF signal is used to drive the RF Power Amplifier (PA). The nonlinear characterization of a concurrent dual-band RF PA is discussed while two band signals in the dual-band are modulated by CDMA2000 and WCDMA signals. When the two band signals in the dual-band of the PA are modulated with the same signals, it is found that the nonlinearity of the PA can be expressed by any of the two corresponding baseband data. On the other hand, when the two band signals in the dual-band of the PA are modulated with two different signals, the PA nonlinearity cannot be characterized by any of the two corresponding baseband data. In this case, its nonlinearity has to be denoted by a composite signals consisting of the two baseband signals. Consequently, the requirements for the speed of the A/D converter can be largely reduced. The experimental results with CDMA2000 and WCDMA signals demonstrate the speed of the A/D converter required is only 30 M Sample Per Second (SaPS), but it will be at least 70 M SaPS for the conventional method.

Subsampling Feedback Loop Applicable to Concurrent Dual-Band Linearization Architecture

This paper demonstrates an energy-efficient and low-complexity subsampling receiver adopted in the feedback loop of the dual-band power amplifier (PA) linearization architecture. The challenges and issues on finding the valid subsampling frequencies in nonlinear system are discussed, and a systematic approach for finding valid subsampling frequencies is presented. The subsampling-based receiver is applied as a proper solution for the feedback loop of the dual-band linearization architecture. It is shown that the subsampling feedback loop reduces the complexity and the cost of the dual-band linearization architecture. The simulation and measurement results show the proper functionality of the presented technique and demonstrate a good linearization performance. The measurement results show that when using this method, more than 15-dB improvement in normalized mean squared error and more than 17-dB improvement in adjacent channel power ratio are achieved for a wideband class-AB PA, compared with the unlinearized method.

Hybrid envelope tracking for efficiency enhancement in concurrent dual-band PAs

A hybrid envelope tracking scheme is proposed for concurrent dual-band power amplifiers (PAs). Ideal power supply sweeping measurement shows this scheme can improve the efficiency of dual-band PAs effectively. The feasibility of this scheme is validated using baseband and analog co-simulation with real large signal circuit models. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:662–664, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26667