Continuous Class-F Power Amplifier Research Articles

Highly efficient broadband continuous Class-F power amplifier with a novel harmonic matching network

In this letter, we propose a methodology for designing high efficiency broadband harmonic-controlled power amplifiers (PAs) with a novel harmonic matching network. This network consists of three second-harmonic open circuit microwave lines and three third-harmonic short circuit microwave lines, each corresponding to different wavelengths for different frequencies. It can improve the efficiency and bandwidth of PAs by controlling harmonic match impedance. Through the proposed network, we design and fabricate a highly efficient broadband continuous Class-F PA using a CGH40010F GaN HEMT device. The measurement results show that the drain efficiency of 71.4% to 82.4% (the average efficiency of 76.9%) and output power of 40.4dBm to 42.6dBm are achieved at 1.3GHz-2.5GHz, respectively.

Design of Continuous Class-F Mode Power Amplifier with High Gain Flatness

In this letter, a novel RF power amplifier (PA) with high gain flatness and high efficiency operating in continuous Class-F mode is introduced. Since most continuous Class-F PAs can’t meet the requirement of high gain flatness, a new structure which can achieve high gain flatness is presented. A 1.7-2.5GHz PA is designed, which uses CGH40010F GaN device. Simulation results show that the drain efficiency (DE) of the continuous Class-F PA is between 69% and 79%, output power is more than 41dBm across the whole bandwidth. Gain is between 11dB and 11.8dB, and gain flatness is 0.8dB.

Design of Wideband Continuous Class-F Power Amplifier Using Low Pass Matching Technique and Harmonic Tuning Network

Many countries have allocated new frequency bands for fifth generation (5G) communication systems. In this paper, a wideband continuous class-F (CCF) radio frequency power amplifier (RFPA) is presented for the new 5G frequency band, from 3.3 GHz to 4.3 GHz using a 10 W Cree CGH40100F device. A unique wideband RFPA design approach for the output matching network (OMN) is also presented by applying a harmonic tuning network (HTN) for the harmonics and a low pass matching technique (LPMT) for the fundamental frequency. The RFPA is fabricated, and promising measurement results show a drain efficiency of 55.9% to 65.3% is achieved at an output power of 40 dBm (± 0.3 dBm) over a frequency range of 3.3 GHz to 4.3 GHz. A two-tone signal with a 10 MHz spacing was also applied to investigate the linearity of the RFPA.

High‐efficiency hybrid continuous mode power amplifier with input and output harmonic engineering

This paper intensely studies the impact of the input nonlinearity caused by the transistor's feedback on the hybrid continuous class-F power amplifier. The research extends the influence of input harmonics on class-F power amplifiers to a more general form. Through waveform engineering, the impact of feedback is analyzed. By analyzing the change in cutoff angle caused by input nonlinearity, the change of the drain voltage and current waveforms of the hybrid continuous class-F power amplifier can be obtained. The new drain voltage and current waveforms obtained from the analysis redefine the design space of source impedance and load impedance for the hybrid continuous class-F power amplifier. By designing the corresponding input and output matching network, the second harmonic is suppressed, and finally, the hybrid continuous class-F power amplifier achieves a high-efficiency state. The research reveals that input harmonics also play an essential role in the design process of power amplifiers. A comparative experiment is designed to verify the theory. Simultaneously, a 1.6–2.8 GHz broadband hybrid continuous class-F power amplifier is designed using this theory, with a saturation efficiency of more than 61.2% and a saturation power of more than 40.4 dBm.

A novel design methodology for extended continuous class-F power amplifiers in wireless applications

A novel design methodology for extended continuous class-F power amplifiers in wireless applications

A high-efficiency continuous class-F power amplifier design using simplified real frequency technique

The fourth-generation (4G) wireless communication has been deployed in many countries. However, there are still some problems such as spectrum crisis due to the increase of wireless mobile devices and servicing. Therefore, the fifth-generation (5G) communication system will be employed at some different spectrum other than 4G frequency band. The radio frequency power amplifier (RFPA) is the key component of the 5G system. In this paper, a broadband continuous class-F (CCF) RFPA is designed for the 5G frequency band from 3.3-4.3 GHz. The input and output matching network are designed using the simplified real frequency technique (SRFT). Using a 10W GaN CGH40010F Cree device, the efficiency of the RFPA achieved greater than 70.7% for the whole frequency band with a maximum of 81.5%. The output power and the gain are more than 40 dBm and 10 dB respectively

Input-Harmonic-Controlled Broadband Continuous Class-F Power Amplifiers for Sub-6-GHz 5G Applications

A comprehensive analysis is presented for investigating the effects of input nonlinearity on performance and broadband design of continuous-mode class-F power amplifiers (PAs). New time-domain waveforms are derived considering input and output harmonic terminations for continuous-mode class-F operation. The derived design equations show that the typical fundamental load design space of a continuous class-F PA must be reengineered in the presence of second-harmonic input nonlinearity to new design space in order to achieve optimum class-F PA performance versus varying second-harmonic load impedance. For the practical validation, the impacts of input nonlinearity on the performance of continuous-mode class-F PAs are first confirmed with pulsed vector load–pull (VLP) measurements on a low-power GaN 2-mm device. Second, a broadband high-power GaN 24-mm part is designed following the proposed theory with in-package input second-harmonic terminations targeting 1.75–2.3-GHz frequency band for the sub-6 GHz 5G high-power applications. Efficiency higher than 65% with peak power more than 53.2 dBm was maintained over the target frequency band, with excellent flatness. Third, a Doherty PA is implemented based on the designed GaN 24-mm part to evaluate the broadband performance with modulated stimuli. Using a multicarrier signal having an instantaneous bandwidth of 395 MHz, the average drain efficiency of the Doherty PA at 8-dB output back-off is higher than 44%, and the linearized adjacent channel power ratio (ACPR) is better than −52 dBc.

Continuous Class-F Power Amplifier Using Quasi-Elliptic Low-Pass Filtering Matching Network

This brief proposes a design approach for a high-efficiency continuous class-F power amplifier (PA) using quasi-elliptic low-pass filtering matching network (QELMN). In comparison with Chebyshev and modified elliptic matching networks, QELMN is composed of the quasi-elliptic low-pass filter (QEL) and optimized transmission lines (TL). QEL is a harmonic controller and matching circuit with low insertion loss, and its passband can be adjusted for each desired amplifier according to the operating band. Sharp roll-off and wide stopband of QEL controls harmonics, and low insertion loss of QEL improves delivered power from transistor to the load. The input impedance of QELMN is optimized with the goals of the stability and high power-added efficiency. The proposed approach is adopted to implement a continuous class-F PA using an LDMOS device under a class-AB bias condition. Experimental results verify a wide bandwidth from 0.3 to 1 GHz, with measured drain efficiency of 62-81%, the output power of 37-40.3 dBm and power gain of 12-15.3 dB.

Software-Defined Radio Transceiver Design Using FPGA-Based System-on-Chip Embedded Platform With Adaptive Digital Predistortion

In this paper, a software-defined radio (SDR) based transceiver system is designed and implemented on the system-on-chip (SoC) platform, which consists of a high-speed Arm embedded processor and a reconfigurable field-programmable gate array (FPGA). In the proposed SDR transceiver, the real-time baseband signal generation and adaptive digital predistortion (ADPD) units are implemented on the SoC platform. Memory polynomial model based ADPD solution is implemented to linearize the radio frequency (RF) power amplifiers (PAs). The implementation of the ADPD on a reconfigurable FPGA platform makes the system flexible and cost-effective. The PA characterization, in terms of model extraction and coefficient calculation, is done in real-time. These calculated coefficients are updated in the transmission path to precondition the transmitted signal before it is applied to the PA. The proposed ADPD is applied at the baseband level. Therefore, it can be used for different classes of PA operating at different RF carrier frequencies. A long-term evolution (LTE) signal with 20 MHz bandwidth and 11 dB peak to average power ratio (PAPR) is used for simulation and measurement purposes. The LTE signal is amplified using a GaN-based harmonically tuned continuous Class-F PA in measurement. The performance of the implemented ADPD scheme is analyzed in terms of NMSE, ACPR and EVM.

Broadband High-Efficiency Power Amplifier With Quasi-Elliptic Low-Pass Response

This paper presents a broadband high-efficiency harmonic-tuned power amplifier (PA) with quasi-elliptic low-pass responses. A combination of continuous Class-F <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and extended continuous Class-F PA modes is employed to significantly expand the design space. A quasi-elliptic low-pass matching network is proposed, which can realize a broadband impedance matching in the predefined optimal impedance region desired by the combination of PA modes. Furthermore, two transmission zeros are generated near the passband, exhibiting high skirt selectivity and providing rapid impedance transition from the passband to the stopband. A wide stopband covering up to the third harmonic is achieved which shows good harmonic suppression. Design procedures of the proposed broadband PA are presented. To verify the proposed methodology, the broadband PA is fabricated and measured. The implemented PA achieves a bandwidth of 145.2% from 0.5 to 3.15 GHz. Over this frequency range, the drain efficiency is measured as 58–74.9% with the output power of greater than 39.03 dBm and a large signal gain ranging from 8.43 to 15.67 dB. A wide stopband is realized from 3.4 to 10 GHz, showing excellent quasi-elliptic low-pass responses. The measured adjacent leakage ratios (ACLRs) using a 20-MHz LTE signal with digital pre-distortion are below −45.06 dBc.

A concurrent dual-band continuous Class-F power amplifier with intermodulation impedance tuning: Analysis and design technique

In this paper, first the behaviour of dual-band continuous class-F (Class-CF) power amplifiers under concurrent input drive at both bands are studied. Then, a novel structure including second and third harmonic control networks as well as intermodulation tuning network intended for higher concurrent-mode efficiency is proposed accompanied by a detailed design methodology. The study has revealed that the performance of concurrent Class-CF dual-band power amplifiers (DB-PAs) under overdrive condition strongly depends on the design space factor. The impact of the device nonlinear output capacitance on the concurrent mode efficiency is also evaluated. To authenticate the validity of the proposed methodology, a Class-CF concurrent dual-band PA operating at 1.842 and 2.655 GHz bands is implemented. Experimental results exhibit output powers of 41.7 and 40.5 dBm and efficiencies of 75% and 72% at the lower and upper bands, respectively, while 62% concurrent-mode efficiency is obtained.

A 25–35 GHz Neutralized Continuous Class-F CMOS Power Amplifier for 5G Mobile Communications Achieving 26% Modulation PAE at 1.5 Gb/s and 46.4% Peak PAE

This paper presents a high-efficiency neutralized continuous class-F (CCF) CMOS power amplifier (PA) design technique for millimeter-wave (mmW) 5G mobile communications. A parasitic-aware tuned-load with a high-order harmonic-resonance network is proposed to shape the current and voltage waveforms for the CCF PA. At mmW frequencies, the gate-drain capacitance ( $C_{\mathrm {gd}}$ ) creates adverse capacitive loading on harmonic-tuned output load networks. As a result, a CCF PA suffers from compromised power efficiency. To address this, we integrate a transformer with a tunable coupling coefficient between gate-drain of the power-device. This proposed technique allows accurate neutralization of $C_{\mathrm {gd}}$ , reducing detrimental loading effect on harmonic-tuned load while enhancing power efficiency and stability. We fabricated a CCF PA in 65-nm CMOS technology achieving >40% power-added efficiency (PAE) over 33.3% fractional bandwidth (25–35 GHz) and 46.4% peak PAE at 29 GHz. The measured peak saturated output power ( $P_{o,\mathrm {sat}}$ ) is 14.8 dBm at 30 GHz. The PA is tested with 64-quadrature-amplitude-modulated signal at a data rate of 1.5 Gb/s. Under this test setup, the PA achieves modulated PAE of 26%/24%/21.4% and average output power ( $P_{o,\mathrm {avg}}$ ) of 9.2/8.8/8.6 dBm at 28, 32, and 34 GHz, respectively, while maintaining better than −25 dB of error vector magnitude and −27 dBc of adjacent channel leakage ratio. To the authors’ knowledge, this design presents one of the highest reported PAEs among mmW CMOS PAs.

Design of Highly Linear Broadband Continuous Mode GaN MMIC Power Amplifiers for 5G

In this paper, we present a design approach for broadband harmonic-tuned monolithic microwave integrated circuit (MMIC) power amplifiers (PAs). Two harmonic matching networks are proposed for the realization of continuous class-B and class-F modes in an integrated PA. A design procedure is developed for integrated PAs using these matching networks to achieve high linearity, broadband operation, and compact chip area, in the presence of parasitic components and the physical limitations of the MMIC process. Two proof-of-concept fully integrated PAs are implemented in a 0.25-μm GaN-on-SiC process. Output power of 34.2-36.4 dBm with 40% to 49% power-added efficiency (PAE) is achieved in 4.2-7.0 GHz (51.6% fractional bandwidth), from the continuous class-B PA with only 1.5-mm 2 chip area. Furthermore, the continuous class-F PA achieves 36.2 dBm output power and 52% PAE at 5.0 GHz. The PAs are also characterized using QAM signals with wide bandwidth, in order to evaluate their performance for 5G wireless applications. For a 64-QAM signal with 100-MHz bandwidth and 8 dB peak-to-average power ratio (PAPR), the continuous class-B PA achieves 29.3 dBm average output power, 28% average PAE, and -25 dB (5.5%) error vector magnitude (EVM). The continuous class-F PA, tested using a 200 MHz 256 QAM signal with 8.5 dB PAPR, provides an average output power of 28.5 dBm, average PAE of 27%, and -28 dB (4%) EVM, without any pre-distortion.

Design of Ultrawideband High-Efficiency Extended Continuous Class-F Power Amplifier

Total bandwidth of existing wireless communication technologies covers a wide frequency range of over one octave. But most existing power amplifier configurations cannot meet this requirement while at the same time maintaining a high efficiency. Therefore, a new structure that can achieve multioctave bandwidth is proposed in this paper together with the design methodology. The difficulty in realizing a bandwidth larger than one octave lies in the overlapping of fundamental and harmonic frequencies. Regarding this problem, the continuous class-F mode is extended to allow a resistive second harmonic impedance, rather than the pure reactive one. With the relaxed design requirements and overlapping design space of fundamental and second harmonic frequencies, harmonic tuning and fundamental frequency matching networks can be designed separately. More importantly, broadband matching for fundamental frequencies can be implemented simply by considering only three fundamental frequency points using the multiple frequencies matching method. To verify the validity of the proposed methodology, a multioctave power amplifier was designed, fabricated, and measured. Measured results verify a wide bandwidth of 128.5% from 0.5 to 2.3 GHz. Over this frequency range, drain efficiency was larger than 60% with output power greater than 39.2 dBm and large signal gain larger than 11.7 dB.

Design of High Efficiency Broadband Continuous Class-F Power Amplifier Using Real Frequency Technique With Finite Transmission Zero

In this paper, a new methodology using a distributed ladder structure with finite transmission zero at finite frequencies is proposed for designing a broadband high-efficiency continuous Class-F (CCF) power amplifier (PA). The approach of realizing finite transmission zeros in Richard domain using Real Frequency Technique is first presented. By applying the proposed approach, the characteristics of the driving point impedance (DPI) of the proposed structure can be deduced and obtained in theory. Furthermore, the synthesis methods in Richard domain are extended to synthesize the DPI of the proposed structure. Four types of distributed elements are investigated to synthesize the DPI of the proposed structure. This proposed structure can improve the performance of the CCF PA when the bandwidth approaches an octave as the finite transmission zero can be used to control the second harmonic impedance of the lower frequency which is near the upper frequency of the operation band. To verify the validity of the proposed method, a broadband high-efficiency CCF PA working from 1.15 to 2.2 GHz is designed. Experimental results show that the fabricated PA achieves 11.3–13.7 dB power gain and 40.5–43.2 dBm output power in the operation band. And the PA has also achieved a high-efficiency characteristic of 70%–83% drain efficiency (DE) over the whole operation bandwidth.

A Precise Harmonic Control Technique for High Efficiency Concurrent Dual-Band Continuous Class-F Power Amplifier

In this paper, a design approach for a high-efficiency concurrent dual-band power amplifier (PA) with precise harmonic control up to third order is proposed. With the precise harmonic control approach, the high-efficiency performance of the PA can be improved at two arbitrary wide interval frequencies. Based on the inherent impedance matching flexibility of the continuous Class-F (CCF) operating mode, the design spaces of fundamental and harmonic impedances of the PA are largely expanded. The optimal impedances of a CCF PA mode at the internal current-generator (I-gen) plane and package plane are investigated, respectively, and a novel dual-band matching network topology is designed to simultaneously present required load impedances at the fundamental and harmonic impedances of both operation frequencies. First, a harmonic control network is designed to control the harmonic impedances precisely for CCF operation. Then, the fundamental impedances are synthesized using the real frequency technique. To verify the validity of proposed methodology, a dual-band CCF PA operating at 2.6 and 3.5 GHz is designed, fabricated, and measured. The measurement results show that the peak drain efficiency is 76.7% with an output power 42.4 dBm at the lower band and 72.8% with an output power 41.1 dBm at the upper band.

Investigating Continuous Class-F Power Amplifier Using Nonlinear Embedding Model

This letter investigates the design space for feasible load impedances of broadband continuous class-F power amplifier (PA) using the nonlinear embedding transfer function. This can overcome the limitation of anticlockwise trajectory of second-harmonic impedance on Smith chart. The approach starts with the design at intrinsic plane based on generic representation of drain voltage and current waveforms. Nonlinear embedding transfer network is then used to project intrinsic loads to the package plane. The proposed design strategy is verified with the implementation of a 15-W GaN HEMT-based PA operating over the frequency range of 1.5 to 2.5 GHz with drain efficiency between 60%–75%. This corresponds to the fractional bandwidth of 50%.

A 0.4–2.3 GHz broadband power amplifier extended continuous class-F design technology

A 0.4–2.3 GHz broadband power amplifier (PA) extended continuous class-F design technology is proposed in this paper. Traditional continuous class-F PA performs in high-efficiency only in one octave bandwidth. With the increasing development of wireless communication, the PA is in demand to cover the mainstream communication standards’ working frequencies from 0.4 GHz to 2.2 GHz. In order to achieve this objective, the bandwidths of class-F and continuous class-F PA are analysed and discussed by Fourier series. Also, two criteria, which could reduce the continuous class-F PA’s implementation complexity, are presented and explained to investigate the overlapping area of the transistor’s current and voltage waveforms. The proposed PA design technology is based on the continuous class-F design method and divides the bandwidth into two parts: the first part covers the bandwidth from 1.3 GHz to 2.3 GHz, where the impedances are designed by the continuous class-F method; the other part covers the bandwidth from 0.4 GHz to 1.3 GHz, where the impedance to guarantee PA to be in high-efficiency over this bandwidth is selected and controlled. The improved particle swarm optimisation is employed for realising the multi-impedances of output and input network. A PA based on a commercial 10 W GaN high electron mobility transistor is designed and fabricated to verify the proposed design method. The simulation and measurement results show that the proposed PA could deliver 40–76% power added efficiency and more than 11 dB power gain with more than 40 dBm output power over the bandwidth from 0.4–2.3 GHz.

Resistive Second-Harmonic Impedance Continuous Class-F Power Amplifier With Over One Octave Bandwidth for Cognitive Radios

A novel methodology for designing highly-efficient broadband harmonic-tuned power amplifiers (PAs) with more than one octave bandwidth is presented in this paper. Continuous class-F power amplifiers with resistive second-harmonic impedance is for the first time analyzed and employed in a multi-sub-band mode to enhance the bandwidth of a conventional continuous class-F PA. The load-pull method is employed at both fundamental and harmonic frequencies, and the simplified real frequency technique algorithm is used to design and synthesize the PA matching networks. Experimental results show that the fabricated PA operates from 525 to 1325 MHz, with drain efficiency over 70% and output higher than 39 dBm. Digital predistortion is applied to the PA and the adjacent channel power ratio is improved to more than -40 dBc.

A Simplified Broadband Design Methodology for Linearized High-Efficiency Continuous Class-F Power Amplifiers

This paper describes the design approach employed for achieving approximated continuous Class-F power amplifier (PA) modes over wide bandwidths. The importance of the nonlinear device capacitance for wave-shaping the continuous Class-F voltage and current waveforms is highlighted, thus reducing the device sensitivity to second and third harmonic impedance terminations. By identifying the high-efficiency regions on the reactance plane for harmonic band placement, the design can be reduced to a fundamental matching problem. The distributed simplified real frequency technique synthesis algorithm can then be utilized to achieve wideband operation. Using a 10-W Cree GaN HEMT device, greater than 70% efficiency has been measured over a 51% bandwidth from 1.45 to 2.45 GHz, with output powers of 11-16.8 W. The nonlinear PA was then linearized using digital predistortion with 20-MHz long-term evolution and 40-MHz eight-carrier W-CDMA excitation signals, to attain adjacent channel power ratios below -53 and -49 dBc, respectively. To the best of the authors' knowledge, the measured results represent the best performance obtained from a broadband switch-mode PA, and the best linearized switch-mode performance using 20- and 40-MHz modulated signals.