High Efficiency RF Power Amplifier Research Articles

Комбинирование синтетических методов высокоэффективного высокочастотного усиления

To amplify modern high crest factor telecommunication radio signals with high efficiency, switching operation modes of transistors and synthetic amplification methods are used. The most common of these are the Kahn method (EER – envelope elimination and restoration) and the outphasing method. However, application of these methods has a number of technological (in terms of element base capabilities) limitations on the bandwidth and dynamic range of amplified signal. To expand high-efficiency RF power amplifiers field of application, the possibilities of combination several different synthetic amplification techniques are being considered. Expressions are obtained for the theoretically achievable efficiency when combining the outphasing method with a bridge power combiner and pulse-step modulation of supply voltage. The dependence of average efficiency on the number of supply voltage levels is determined. RF amplified signal bandwidth and its dynamic range determine the minimum required pulse width of the PWM modulator for the EER amplifier. Variants of these characteristics dependence on the number of supply voltage levels are discussed with combined use of PWM and pulse-step modulation of the supply voltage. Directions for further research are formulated.

A Dual-Band Dual-Output Power Amplifier for Carrier Aggregation

This paper demonstrates a high-efficiency dual-band RF power amplifier (PA) for sub-6 GHz 5G carrier aggregation. The dual-band PA is tested with modulated signals generated by a new algorithm designed to provide realistic waveforms for carrier aggregation scenarios, allowing flexible complex (IQ) modulated sequences with arbitrary peak-to-average power ratio (PAPR), bandwidth, and band distribution. A single-stage PA is designed with a packaged 6-W transistor and a diplexer-like output matching network that separates the two bands into two outputs. It achieves an output power of 36.7 and 37.1 dBm and a power-added efficiency (PAE) of 40.4% and 39.9% at 3.5 and 5.5 GHz, respectively. Under concurrent, dual-band drive with 10-MHz, 6-dB PAPR signals and with digital predistortion applied to varying frequency notch bandwidths, an average PAE of 25.6%, a normalized mean square error of 2.4%/1.0%, and an adjacent channel power ratio of −46.8/−48 dBc in the two bands (3.5/5.5 GHz) is measured.

A High Efficiency RF Power Amplifier Using Linearity-Enhanced Method in 40nm Standard CMOS Process

A two-stage RF CMOS power amplifier with high linearity for WLAN is presented in this paper.The proposed PA consists of a programmable gain amplifier and a high power stage which is composed of a main amplifier with class AB bias and an auxiliary amplifier with class C bias. To improve the linearity ,an integrated diode linearition circuit provides a compensation mechanism for the input capacitance variation of the active devices,improving the linearity from the gain compressing. Moreover ,based on the un-even bias scheme,the power stage can improve linearity and reduce current consumption in the low power region. In order to demonstrate the feasibility of the technique,two types of PAs have been designed.The improved PA at 3.3V supply voltage,has a 37dB of power gain, 1.1 dBm increase of P,8.3% increase of PAE@Pand dB increase of ACPR for 802.11g WLAN,respectively,as compared with the traditional PA.

A New Topology of Load Network for Class F RF Power Amplifiers

High efficiency RF power amplifiers are increasingly needed in modern mobile communication systems to reduce the battery size and power supply consumption. Class-F RF power amplifiers offer improved efficiency over the conventional class-B power amplifiers by properly controlling the harmonic components of the voltage and current signals at the output terminals of the RF device while driving it to operate as an ON/OFF switch. To do this task, a suitable load network is to be synthesized in order to present the proper harmonic impedances at the output of the RF power transistor. In this paper, a new load network for class F power amplifiers has been introduced and derived analytically. The proposed network consists of a parallel short circuited λ/8 stub, parallel open circuited λ/8 stub, and a T-section lumped-elementtransformer. The benefits of this topology include simplicity of design, controllable bandwidth, and harmonic tuning and impedance transformation at the same time. To confirm the approach of analysis, a 10 W class-F UHF power amplifier circuit has been designed and simulated using a typical Gallium Nitride high electron mobility RF transistor (GaN HEMT) to operate at 500 MHz with the aid of the Advanced Design System (ADS)computer package. The simulated results haveindicated that the circuit gives adc-to-RF efficiency of more than 84 % and a power gain of 11 dB at 500 MHz with an operating bandwidth from 440 to 540 MHz.

Guest Editorial Special Section on the 2016 International Conference on Compound Semiconductor Manufacturing Technology (CS MANTECH)

As guest editors for the special section on the 2016 International Conference on Compound Semiconductor Manufacturing Technology (CS MANTECH), we are pleased to present the readership of IEEE Transactions on Semiconductor Manufacturing with a selection of papers developed from presentations made at this year’s conference. While semiconductor wafer volume is dominated by technologies based on silicon, compound semiconductor devices and integrated circuits are important for a range of applications and markets. Compound semiconductors have traditionally found use in technological areas demanding maximum performance, often for high speed or high frequency applications. Examples include high-speed wired, fiber, and point-to-point communications infrastructure, defense-related sensing and communications, and high-efficiency RF power amplifiers in consumer mobile wireless applications. However, recent trends have been eroding these traditional distinctions, with emerging applications such as power control and commercial wireless infrastructure being increasingly addressed using GaN and related materials, while ultra-low-power analog–and even future CMOS nodes for logic–embracing narrow-band gap III-V materials.

Design considerations on wideband envelope termination for high efficiency RF power amplifiers

Design approach of wideband envelope termination (ET) for high efficiency RF power amplifiers (PAs) is discussed, considering power loss subject to design constraints including envelope bandwidth, inductor quality factor, and transistor output impedance. Analysis shows that the optimum ET topology depends on the design constraints. For LTE-advanced transmission with 80 MHz channel bandwidth, a novel wideband ET is designed using an AC-terminated third-order LC filter (LCF-ET), providing 3 dB envelope impedance bandwidth of 150 MHz. Measured results demonstrate 1.75 dB envelope power loss and −39.2 dB normalised root-mean-square error with the LTE envelope signals. For the LTE signal with 10.3 dB peak-to-average power ratio, the average power efficiency of an ideal Class-A RF PA with the LCF-ET prototype is calculated as 33.4% from the measured 1.75 dB envelope power loss, which exceeds 4.7% and 24.0% average power efficiency of conventional Class-A and Class-B PAs without ET.

A Fully Integrated High Efficiency RF Power Amplifier for WLAN Application in 40 nm Standard CMOS Process

This paper proposes a CMOS linear power amplifier (PA) design scheme for IEEE 802.11g (WLAN) application. The proposed PA consists of a programmable gain amplifier and a high power stage which is composed of a main amplifier with class AB bias and an auxiliary amplifier with class C bias. Based on the un-even bias scheme, the power stage can improve linearity and reduce current consumption in the low power region. It is fabricated with a TSMC 40 nm standard RF CMOS process. The measurements show that the designed PA reaches a 1 dB gain compression output power of 24.6 dBm and a peak drain efficiency of 38% with a 3.3 V power supply at 2.4 GHz operating frequency range. When the PA was tested with an IEEE 802.11g OFDM signal of 20 MHz channel bandwidth, the obtained -25 dB EVM compliant output power and drain efficiency are 18.5 dBm and 14%, respectively.

A Highly Efficient and Linear Class AB Power Amplifier for RFID Application

Power amplifiers (PAs) are usually the largest consumer of power in the transmitter . Therefore , designing a high efficiency RF power amplifier might be the best solution to cope with the problem of battery lifetime limitations in portable RFID code reader . I n this paper, the designed circuit in Agilent ADS software is implemented using 0.18 μm RFCMOS technology at 3.3 v supply voltage . The measured results indicate that power added efficiency,out put power and power gain of the proposed class AB power amplifier at frequency of 2.4GHz are 35% , 30 dBm and 28dBm.

A scalable GaN HEMT large-signal model for high-efficiency RF power amplifier design

This paper presents a large-signal empirical model for GaN HEMT devices using an improved Angelov drain current formulation with self-heating effect and a modified non-linear capacitance model. The established model for small gate-width GaN HEMTs is validated by on-wafer load-pull measurements up to 14 GHz. Moreover, a scalable large-signal model is presented by adding scalable parameters to drain-source current and non-linear capacitance equations. The scalable model of a 1.25 mm GaN HEMT has been employed to design a class-AB power amplifier for validation purposes. The results show that good agreement has been achieved between the simulated and measured results with 37.2 dBm saturation output power (Psat) and 58% maximum power-added-efficiency at 3 GHz.

High-Power Wideband $L$-Band Suboptimum Class-E Power Amplifier

This paper presents a high-power high-efficiency wideband suboptimum Class-E RF power amplifier based on a packaged high-power GaN HEMT. It uses a simple double-reactance compensation and impedance transformation load network that includes device intrinsic capacitance, package parasitics, low-loss microstrip transmission lines, and lumped components. This load network makes the GaN HEMT operate in suboptimum Class-E from 900 to 1500 MHz (50% fractional bandwidth at 1200 MHz). The amplifier can operate both in continuous wave and pulsed modes over its full bandwidth without tuning. It delivers up to 180-W output power with up to 85% drain efficiency and PAE=81%. To the best of the authors' knowledge, the amplifier proposed in this work outperforms commercial grade amplifiers that operate in the same frequency band with similar output power levels. Direct applications for this amplifier include mobile satellite communications transmitters, envelope elimination and restoration digital audio broadcasting transmitters, and power stages for primary and secondary RADAR transmitters.

Time-reversal duality of high-efficiency RF power amplifiers

The similarity between RF power amplifiers and rectifiers is discussed. It is shown that the same high-efficiency harmonically-terminated power amplifier can be operated in a dual rectifier mode. Nonlinear simulations with a GaN HEMT transistor model show the time-reversal intrinsic voltage and current waveform relationship between a class-F amplifier and rectifier. Measurements on a class-F-1 amplifier and rectifier at 2.14 GHz demonstrate over 80% efficiency in both cases.

Editorial

The four papers that are part of this special topic cover high-efficiency supply-modulated RF power amplifiers.

1-W high linear broadband RF power amplifier with Certesian feedback for TETRA modulation [Application Notes

Designing a high-linearity, high-efficiency RF power amplifier with wide bandwidth design is a real challenge. This article explores a technique to achieve 30 dBm output power with an adjacent channel power ratio (ACPR) of more than -65 dBc for frequency range of 800-900 MHz. A three-stage gallium arsenide heterojunction bipolar transistor (GaAs HBT) RF power amplifier with Cartesian feedback in closed-loop form is the main architecture of the design. An adaptive bias technique was used in the RF power amplifier design to achieve high linearity while preserving good efficiency.

High Efficiency RF Power Amplifier Designed With Harmonic Real-Time Active Load-Pull

In this work, a high efficiency p-HEMT radio frequency power amplifier (PA) is designed using a new multiharmonic real-time active load-pull using the large signal network analyzer. This technique synthesizes a large set of instantaneous load mismatches to quickly find the optimal harmonic impedances, so as to achieve high PA efficiency in a shortened design cycle. At 2 GHz a demo power amplifier implemented with a p-HEMT demonstrated a power added efficiency (PAE) of 68.5% for 18.0 dBm output power, while achieving a maximum PAE of 75% below the 1 dB compression point for 18.6 dBm output power.

Geometry Effect on SiGe Heterojunction Bipolar Transistor Unit Cell for 1 W High-Efficiency RF Power Amplifier Applications

The effect of geometry on the RF power performance of silicon–germanium heterojunction bipolar transistor (SiGe HBT) unit cells is investigated using various emitter finger spacing (S). Two unit cells, namely, HBT-1 and HBT-2 with the same emitter area of 8×0.6×10 µm3 but with different S values are thoroughly discussed. The S values of HBT-1 and an HBT-2 are 2 and 5 µm, respectively. The obtained measurements, including DC characteristics and small- and large-signal performance characteristics of high-breakdown SiGe HBT unit cells, are presented. The HBT-1 in class-AB operations at 2.4 GHz achieves an output 1 dB compression point (OP1dB) of 16.0 dBm, a maximum output power of 17.4 dBm, and a peak-power added efficiency (PAE) of 59.1%. Under the same testing conditions, HBT-2 achieves an OP1dB of 19.6 dBm, a maximum output power of 20.6 dBm, and a PAE of 64.5%. HBT-2 yields significant improvements in all power performance parameters compared with HBT-1, such as 3.6 dB in an OP1dB, a maximum output power of 3.2 dB, a PAE of 5.4%, and an improvement in the power performance figure of merit (FOM) of approximately 50%, which is attributed to the fact that HBT-2 has a lower thermal effect than HBT-1. The thermal effect affects both DC and output power characteristics. A 1 W power device fabricated by combining eight HBT-2 unit cells achieves a power gain of 14.5 dB and a maximum PAE (PAEmax) of 75% in a class-AB operation at 2.4 GHz. The power density is calculated to be up to 2.6 mW/µm2. These results demonstrate that SiGe HBT technology has great potential for high-power amplifier applications.

A 3.3 V Power Feedback Chip for Linearization of RF Power Amplifiers

The power feedback technique is a simple and low cost linearization scheme suitable for consumer products such as hand sets. This paper presents a custom chip for linearization of RF power amplifiers using power feedback. The chip, implemented in a standard double-metal double-poly 0.6 μm CMOS process, operates with 3.3 V supply voltage and consumes 62 mW. When it was used to linearize a commercially available high efficiency RF power amplifier at 850 MHz, experimental results showed that out-of-band power at 30 kHz offset was reduced some 10 dB for a π/4-shifted DQPSK modulated North American digital cellular (NADC) signal. For the same level of adjacent channel interference (ACI), the efficiency was increased from 35% to 48%.

The class BD high-efficiency RF power amplifier

Class B and class D operation of the same RF power amplifier circuit is not normally possible because of constraints imposed by the tuned output circuit and DC power input circuit. The use of square-wave drive in a current switching class D RF amplifier circuit allows the amplifier to move gradually from current source to current switch operation. This amplifier, called class BD, has a linear transfer characteristic (drive envelope to output envelope) and an efficiency 1.23 times that of a class B RF amplifier with the same peak output. The addition of a resistive AC current path to ground in the DC power input circuit of the class BD RF amplifier allows operation with sinewave driving waveforms. While this lowers the efficiency at the peak output, it can raise it at lower outputs, making possible a factor of 1.57 improvement in efficiency in the amplification of signals with large peak-to-average ratios. The class BD RF amplifier may therefore be used as a broad-band replacement for a Doherty-type amplifier.