High-linearity Power Amplifier Research Articles

Predistorter for Nonlinear Distortion Mitigation in GFDM Systems

Next-generation wireless systems use the non-orthogonal modulation technique known as generalized frequency division multiplexing (GFDM). The nonlinearity of the high-power amplifier (HPA) greatly affects the performance of the wireless system. Without phase distortion and only amplitude distortion in the GFDM system using HPA Model Rapp. The effects of nonlinear distortion that occur involve distortion of the amplitude, signal constellation distribution, and spectral distribution. There are two contributions to this paper. First, the impact of HPA Model Rapp's nonlinear distortion on the GFDM system in the AWGN (additive white Gaussian noise) and Rayleigh channels was investigated. The simplicity of this model is the reason it was picked and has an AM/AM (amplitude modulation/amplitude modulation) curve. Second, the linearization of HPA with the use of a predistorter method in GFDM systems has been proposed. The nonlinear distortion impact of HPA can be mitigated by this predistorter. This technique is implemented in the transmitter section. The system performance investigated is determined by a bit error rate (BER) analysis, a constellation diagram, and a spectrum analysis. HPA generates a 55 dB rise in out-of-band (OOB) in the signal spectrum. The HPA effect was successfully compensated for by a 55 dB decrease in the OOB value of the predistorter system.

High Linear and Temperature Insensitive GaAs Power Amplifier Operating at 3.3–3.6 GHz Using a Multi-Feedback Branch Bias Circuit

This letter describes a design of a 3.3–3.6-GHz GaAs heterojunction bipolar transistor (HBT) power amplifier (PA) with high linearity and temperature insensitivity for the fifth-generation (5G) of new radios (NRs). By involving a multi-feedback branches bias circuit, the voltage at the feedback node of the bias circuit can achieve dynamic self-tuning to stabilize the base voltage as the amplifier’s input power grows and stabilize the bias current as the temperature increases as well. A three-stage common source structure PA in the form of a monolithic microwave integrated circuit (MMIC) is designed using a multi-feedback branch bias circuit with a 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">$1.5\times1.2$ </tex-math></inline-formula> mm. Measured with continuous wave (CW) signals, the output 1-dB compression point at 3.3–3.6 GHz is 34 dBm. The linearity of the PA is also evaluated using a 5G-NR 100-MHz 64-quadratic-amplitude modulated (QAM)-orthogonal frequency division multiplexing (OFDM) signal with a 7-dB peak-to-average-power ratio (PAPR). The proposed PA achieves an adjacent channel power ratio (ACPR) less than −49.5 dBc at an average power of 28 dBm with a power-added efficiency (PAE) of 20% without the use of digital pre-distortion (DPD). In the temperature range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 40\,\,^{\circ }\text{C}$ </tex-math></inline-formula> to 120 °C, the variance of bias current, small signal gain, PAE, output power at 1-dB compression point (OP1dB), and ACPR is relatively minor. This design is ideally suited for 5G communication systems due to its high linearity and temperature insensitivity.

A 5–6-GHz CMOS Beamforming Transceiver Front-End for Fiber-to-the-Room All-Optical Wi-Fi Solution

This letter presents a 5–6-GHz CMOS beamforming transceiver front-end with high linearity and low power consumption for fiber-to-the-room (FTTR) all-optical Wi-Fi solution, which can greatly reduce the transmission power and eliminate signal mutual interference among access points compared with traditional architecture, by aggregating beams of multichannel. The transmitter (TX) employs a high-linearity power amplifier, a variable-gain amplifier, a 5-bit passive attenuator (ATT), and a 4-bit passive phase shifter (PS). The receiver (RX) is composed of a single-to-differential variable gain low-noise amplifier (LNA), frequency-tuning buffers, a 5-bit ATT, and a 4-bit PS. Implemented in a 55-nm CMOS technology, the measured output power 1dB compression point (OP1dB) of TX is better than 12.1 dBm. The error vector magnitudes (EVMs) of the TX at 0-dBm output power with 80-MHz 256-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal are better than −36.3 dB, and the EVMs of the RX at −40 dBm input power are better than −37.8 dB. The noise figure is 4.3 dB in high-gain mode.

Simulation Analysis of Low PAPR FFT-based OFDM Through Nakagami Channel

In response to the inefficiency of power amplifier in conventional Orthogonal Frequency Division Multiplexing (OFDM) system, a low Peak-to-Average Power Ratio (PAPR) scenario can be obtained by implementing several PAPR reduction techniques. Partial Transmit Sequence (PTS) is a well-known instance to provide zero distortion for the system, while clipping is one of the simplest methods but it is sacrificing the error rate performance. In this work, Authors focused on analyzing the implementation of PTS and Palm Date Leaf clipping technique on OFDM system with 16-, 64-, 256-, and 1024-QAM under various Nakagami channel. In addition, the High-Power Amplifier (HPA) was also considered by using Solid State Power Amplifier (SSPA) model. It was found that linear HPA serves as the lower boundary for non-linear HPA, and system under high saturation level performs similarly. In physical properties, high saturation level is equivalent to higher power consumption in amplifier. Thus, optimal level was obtained by considering taking the one with moderate BER performance. After the system’s PAPR was reduced, the optimum saturation level of HPA was found to be 5 dB, 8 dB, 9 dB, and 11 dB for each Quadrature Amplitude Modulation (QAM) under Nakagami channel with m value of 1.5. However, this value was found to be ample for lower m value such as 1 or 0.7. In this case, the system required lower saturation level on the HPA for Nakagami channel with lower m value.

Green and Highly Efficient MIMO Transceiver System for 5G Heterogenous Networks

The paper presents the general requirements and an exemplary design of the RF front-end system that in today&#x2019;s handset is a key consumer of power. The design is required to minimize the carbon footprint in mobile handsets devices, whilst facilitating cooperation, and providing the energy-efficient operation of multi-standards for 5G communications. It provides the basis of hardware solutions for RF front-end integration challenges and offers design features covering energy efficiency for power amplifiers (PAs), Internet of Things (IoT) controlled tunable filters and compact highly isolated multiple-input and multiple-output (MIMO) antennas. An optimum design requires synergetic collaboration between academic institutions and industry in order to satisfy the key requirements of sub-6 GHz energy-efficient 5G transceivers, incorporating energy efficiency, good linearity and the potential for low-cost manufacturing. A highly integrated RF transceiver was designed and implemented to transmit and receive a picture using compact MIMO antennas integrated with efficient tunable filters and high linearity PAs. The proposed system has achieved a bit error rate (BER) of less than 10&#x2013;10 at a data rate of 600 Mb/s with a wireless communication distance of more than 1 meter and power dissipation of 18&#x2013;20 mW using hybrid beamforming technology and 64-QAM modulation.

HPA Linearization for Next Generation Broadcasting Systems With Fast Convergence-Digital Predistortion

The Last decade saw significant growth in the digital terrestrial television (DTT) subscribers. The High peak-to-average power ratio (PAPR) of the transmitted signal is implied by the large fluctuations in its amplitude, which is a serious issue in the contemporary and next generation DTT broadcasting systems. These large fluctuations prevent feeding the high power amplifier (HPA) at an operating point near its non-linear (NL) saturation region, thereby lowering its power efficiency. For a better future, energy-efficient green communications is the need of hour. This paper focuses on digital predistortion (DPD), which is among the widely used techniques for HPA linearization in order to minimize the NL effects. DPD technique requires a feedback signal. This paper proposes a novel adding signal-based digital predistortion, where the output of the HPA is gradually linearized by adding a signal at the input in an iterative manner. By Taylor series approximation, the DPD problem can be posed as a convex one. We prove that a tighter upper bound exists for the convergence factor and instead of directly solving the convex problem, we pick a convergence factor value within its bounds that offers a good trade-off between convergence speed and residual error value. The simulation results show that the proposed technique can quickly linearize the HPA with good convergence.

A Nonlinear MIMO-OFDM Based Full-Duplex Cooperative D2D Communications System

Multiple input multiple output (MIMO) based orthogonal frequency division multiplexing (OFDM) has widely been used in a wireless communications system for its robustness to frequency-selective channels and better spectral efficiency. The introduction of full-duplex (FD) and device-to-device (D2D) communications, which are potential candidates of fifth-generation (5G) and beyond, further improve the spectral efficiency of MIMO-OFDM based systems. This paper proposes a novel MIMO-OFDM based FD Cooperative-D2D (C-D2D) communications system wherein a cellular user (CU) acts as an FD relay to facilitate seamless communications between D2D transmitter and receiver. The complete analytical framework is presented to analyze the end-to-end performance of the proposed system. Specifically, the closed-form expression for symbol error rate (SER) of the proposed system is derived in the presence of multipath Rayleigh fading channel and residual self-interference (RSI) due to the FD mode. Further, the performance of the system is analyzed in the presence of a nonlinear high power amplifier (HPA) which introduces the nonlinear distortion. Finally, simulation results are presented to verify the derived expressions. The results show that there is higher SER in the presence of nonlinear HPA due to nonlinear distortion, which can be reduced by increasing input back off (IBO). The presence of RSI also increases the SER at CU, which is further reduced by employing self-interference cancellation (SIC) techniques. A complete end-to-end analytical framework is designed to compare the performance of the proposed system with the conventional system with linear HPA and no RSI.

Non-coherent massive MIMO-OFDM for communications in high mobility scenarios

Under scenarios of high mobility, the traditional coherent demodulation schemes (CDS) have a limited performance, due to the fact that reference signals cannot effectively track the variations of the channel with an affordable overhead. As an alternative solution, non coherent demodulation schemes (NCDS) based on differential modulation have been proposed. Even in the absence of reference signals, they are capable of outperforming the CDS with a reduced complexity. The literature on NCDS laid the theoretical foundations for simplified channel and signal models, often single carrier and spatially uncorrelated flat fading channels. In this work, the most recent results assuming orthogonal frequency division multiplexing (OFDM) signaling and realistic channel models are explained, and the impact of some hardware impairments such as the phase noise (PN) and the non linear high power amplifier (HPA) are also considered. Moreover, new potential research lines are also highlighted.

A Design of High Power Beidou L-Band Power Amplifier

According to the optimization problem of power amplifier output power, linearity and other performance indicators, this paper proposes an improved three-level cascade overall design framework, designed by the load traction method, source traction method and power back-off method for the driver stage and final stage power. The amplifier better improves the output power and linearity of the system and the high-gain pre-stage power amplifier is designed by the small-signal S-parameter method. After the performance analysis, simulation design, physical production and testing of the cascaded power amplifier, the output power of the system is 15W. This paper implements high power, high gain, high linearity power amplifier design, and applies this result to BeiDou Navigation Satellite System (BDS).

Design of CMOS Power Amplifier for LTE MTC System Transmitter

An high linearity power amplifier based on TSMC 65nm LP CMOS process was designed, which can meet the application requirements of LTE MTC communication standards in 1.8 8∼1.92GHz band, and the average efficiency was improved. As the core module of the system, the power amplifier employs a two-stage linear amplifier structure, and implemented with the technique of lossy networks and matching compensation, meets the requirements of indicators in wide-band range. According to the post-simulation results, in the working frequency band of 1.88∼1.92GHz, the proposed PA achieves maximum output power of more than 26dBm, power gain is over 20dB.The OP1dB is more than 24dBm,and the power added efficiency (PAE) at OP1dB is over 25%.The simulated S11 is under -10dB and achieved good input matching feature.

Constant envelope OFDM RadCom fusion system

A joint radar and wireless communication (RadCom) fusion system is an important trend for future intelligent transportation, such as the Internet of Vehicles (IOV). However, traditional joint orthogonal frequency division multiplexing (OFDM)-based RadCom fusion system suffers from the problem of high peak-to-average power ratio (PAPR) of transmission signals, leading to nonlinear distortion in high power amplifiers (HPAs). To solve this problem, a new constant envelope OFDM RadCom approach is proposed in this paper. Taking phase modulation into consideration, the constant envelope OFDM RadCom system obtains 0 dB PAPR value, which results in linear high power amplifier being feasible. In the receiver side, both communication transmission and target detection are guaranteed by a phase demodulator and frequency-domain signal processing algorithm, respectively. Simulation results demonstrate that the constant envelope OFDM RadCom system is a feasible solution for future IOV with the capability of target detection and wireless communication simultaneously.

Power Allocation for Energy Efficient Multiple Antenna Systems with Joint Total and Per-Antenna Power Constraints

An energy efficiency (EE) maximization problem with multiple transmit antennas (multiple-input-single-output or distributed antennas setups) is considered in this paper. Besides the constraint on the total transmit power, per-antenna transmit power constraints, and a total weighted power constraint are jointly considered. Moreover, a quality-of-service constraint is also considered. Both linear and nonlinear high power amplifier (HPA) cases are studied. Because the original problem for the linear HPA case is a fractional convex problem, Dinkelbach’s algorithm is implemented to reformulate the problem. By investigating the Karush-Kuhn-Tucker conditions, the mathematical properties of the globally optimal solution are studied and proved, which provides a deeper understanding of the structure of power allocation among antennas. These properties also lead to a reduction of the complexity of the algorithms proposed to find the global optimum. For the nonlinear HPA cases, the reformulated problem after successive convex approximation is shown to be exactly in the same form as that of the previous problem with linear HPA with different weights of power consumption at each antenna. On the basis of numerical results comparing our EE maximization algorithms against different benchmarks, the efficiency and the superiority of our algorithms can be concluded.

A Novel High Linear CMOS Fully Integrated PA for the Design of Zigbee Transmitters

This paper describes a 863–870-MHz transmitter for wireless sensor applications. The fully integrated designed circuit is based on AMS 0.35-μm CMOS standard technology. The transmitter presented is composed by four stages: quadrature voltage-controlled ring oscillator (QVCO) controlled by a voltage (VCTRL), two passive switch mixers, two combiners (a substractor and an adder), and a novel high linear power amplifier (PA). Combiners and the PA has the distinction of being based on CMOS inverter circuit. The post-layout simulation of the fully differential transmitter, at the desired oscillation frequency and under a supply voltage of 3.3 V, shows that proposed circuits satisfy specifications desired especially the output power level and PA linearity.

Simulation study of linear power amplifier for underwater imaging sonar applications

High frequency acoustics are preferred for underwater imaging sonar applications due to its attractive characteristics such as high spatial resolution and wide bandwidth. But it suffers severe range limitation imposed by attenuation that increases approximately as frequency-squared. Hence high frequency signals with sufficient power is required to get the desired range and resolution. For underwater imaging system usually power amplifier is an integral part of wet end system. This paper discuss the simulation study of high frequency linear power amplifier for under water imaging sonar applications.

A Linear GaN High Power Amplifier MMIC for &lt;roman&gt;Ka&lt;/roman&gt;-Band Satellite Communications

A linear high power amplifier (HPA) monolithic microwave integrated circuit (MMIC) is designed with 0.15 μm gallium nitride (GaN) high electron mobility transistor (HEMT) technology on silicon carbide (SiC) substrate. To keep the linear characteristics of the power stage, 2:4:8 staging ratio of 8 × 50 μm unit transistor is adapted for the 3-stage HPA MMIC. The MMIC delivers P3 dB of 39.5 dBm with a PAE of 35% at 21.5 GHz. Linear output power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ) meeting IMD3 of -25 dBc is 37.3 dBm with an associated PAE of 29.5%. The MMIC dimensions are 3.4 mm × 2.5 mm, generating an output power density of 1049 mW/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Linearization of High Power Amplifier Using Modified Artificial Bee Colony and Particle Swarm Optimization Algorithm

A linearization method for power amplifiers is proposed to cancel out distortion induced during amplification. Wiener model is chosen for power amplifier modelling. The linearization is achieved by the Modified Artificial Bee Colony (ABC) and Particle Swarm Optimization (PSO) algorithm. The Modified ABC and PSO algorithm reduces the complexity in linearization. Experimental results obtained for the proposed method shows that a better linearization of the amplifier characteristics can be obtained using the proposed method.

Realization of High Efficient Linear Power Amplifier with Harmonic Tuning

Realization of High Efficient Linear Power Amplifier with Harmonic Tuning

2.4 GHz CMOS self‐biased power amplifier with embedded diode lineariser

A high-linearity CMOS power amplifier (PA) operating at 2.4 GHz with an integrated diode lineariser is presented. A diode-connected N-type MOS transistor is used to increase the V gs of the power transistor as input power increases for linearity improvement. The CMOS PA fabricated in 180 nm CMOS technology achieved 32 dB small signal gain, 30.2 dBm P sat, 28.2 dBm P 1 dB, and a 31.1% peak power added efficiency. By adopting the proposed diode lineariser, the output 1 dB is improved from 24.9 to 28.2 dBm.

A WCDMA/WLAN Digital Polar Transmitter With Low-Noise ADPLL, Wideband PM/AM Modulator, and Linearized PA

This paper presents a single-chip digital-intensive polar transmitter for WCDMA and WLAN integrating a low-phase-noise all-digital phase-locked loop (ADPLL), a digitally-controlled wideband phase/amplitude modulator, and a calibration-free high-linearity power amplifier. From the ADPLL, the 1.7–2.5 GHz LO signal is generated together with a ${\div} $ 1.5 frequency divider to eliminate DCO pulling. The phase noise of the ADPLL is optimized by using a linearized stochastic TDC with 3 ps resolution and a Class-C quadrature DCO (QDCO) with embedded quadrature phase shifter and quantization-noise filter. A 2-segment $\Sigma \Delta$ switching phase modulator enhances the PM bandwidth up to 200 MHz, and a digital polar amplifier employs AM-replica linearization to eliminate AM pre-distortion. The TX achieves a ${-}$ 1 dB output compression point of 22.8 dBm with an overall system efficiency of 27.6% and measures EVM of 4% for a 20 MHz 64-QAM signal at an output power of 13.8 dBm.

PAR Reduction in SU/MU-MIMO OFDM Systems Using OPF Precoding Over the Nonlinearity of SSPA

Orthogonal frequency division multiplexing (OFDM) system suffers from a high peak-to-average (power) ratio (PAR) which leads to power inefficiency in radio frequency section and large performance degradation of system due to the nonlinearity of high power amplifiers (HPA). In this paper, a new downlink transmission scheme is designed based on orthogonal periodic function (OPF) precoding to achieve low PAR and investigated for single user and multi-user multiple-input multiple-output wireless systems. It is shown (through mathematical analysis and computer simulations) that the proposed transmission scheme can provide a significant PAR reduction using decorrelation, phase-rotation and orthogonality properties of OPF precoding, while it does not change power spectral levels or error performances due to the unitary property when compared with the normal OFDM systems with linear HPA. The OPF precoding outperforms existing precoding schemes when nonlinear solid state power amplifier (SSPA) is considered with several practical values of input back-off (IBO). Computer simulations show that the OPF precoding can achieve 3.1 and 4 dB PAR gain, while 2.2 and 1 dB SNR gain for IEEE 802.11a and DVB-T systems respectively. Moreover, OPF precoding leads to a total degradation improvement from 0.13 to 1.53 dB for 16 QAM, considering an SSPA with IBO = 8---4 dB respectively. OPF precoding does not increase computational complexity when compared with the existing precoding methods. It is shown that the performance of the proposed precoding is independent of modulation schemes and can work for any number of subcarriers.