Adjacent Channel Leakage Power Ratio Research Articles

A 60-W Multicarrier WCDMA Power Amplifier Using an RF Predistorter

In this brief, we present a 60-W power amplifier that is linearized using an RF predistorter for multicarrier wideband code-division multiple-access (WCDMA) applications. The proposed RF predistorter is fully composed of RF or analog circuits, and it has a moderate memory effect compensation capability using a delayed third-order intermodulation (IM3) component path. It also includes the IM5 generation circuits and a compact IM3 generator that is capable of autocanceling for the fundamental component. The proposed RF predistorter was implemented and applied to a 60-W high-power WCDMA amplifier. For a four-carrier downlink WCDMA signal, the RF predistorter improved the adjacent channel leakage power ratio at a 5-MHz offset by 6.19 dB at an average output power of 48 dBm. The total efficiency of the system is as high as 13.6% at the same output power level. At an output power level of 60 W, the linearized power amplifier complies with the linearity specification of the WCDMA system.

Digital Baseband Predistortion Based Linearized Broadband Inverse Class-E Power Amplifier

A newly introduced inverse class-E power amplifier (PA) was designed, simulated, fabricated, and characterized. The PA operated at 2.26 GHz and delivered 20.4-dBm output power with peak drain efficiency (DE) of 65% and power gain of 12 dB. Broadband performance was achieved across a 300-MHz bandwidth with DE of better than 50% and 1-dB output-power flatness. The concept of enhanced injection predistortion with a capability to selectively suppress unwanted sub-frequency components and hence suitable for memory effects minimization is described coupled with a new technique that facilitates an accurate measurement of the phase of the third-order intermodulation (IM3) products. A robust iterative computational algorithm proposed in this paper dispenses with the need for manual tuning of amplitude and phase of the IM3 injected signals as commonly employed in the previous publications. The constructed inverse class-E PA was subjected to a nonconstant envelope 16 quadrature amplitude modulation signal and was linearized using combined lookup table (LUT) and enhanced injection technique from which superior properties from each technique can be simultaneously adopted. The proposed method resulted in 0.7% measured error vector magnitude (in rms) and 34-dB adjacent channel leakage power ratio improvement, which was 10 dB better than that achieved using the LUT predistortion alone.

A Novel Filter Construction Utilizing HTS Reaction-Type Filter to Improve Adjacent Channel Leakage Power Ratio of Mobile Communication Systems

We propose a new band selective stop filter construction to decrease the out of band intermodulation distortion (IMD) noise generated in the transmitting power amplifier. Suppression of IMD noise directly improves the adjacent channel leakage power ratio (ACLR). A high-temperature superconducting (HTS) device with extremely high-Q performance with very small hybrid IC pattern would make it possible to implement the proposed filter construction as a practical device. To confirm the effectiveness of the HTS reaction-type filter (HTS-RTF) in improving ACLR, investigations based on both experiments and numerical analyses are carried out. The structure of a 5-GHz split open-ring resonator is investigated ; its targets include high-unload Q-factor, low current densities, and low radiation. A designed 5-GHz HTS-RTF with 4 MHz suppression bandwidth and more than 40 dB MHz -1 sharp skirt is fabricated and experimentally investigated. The measured ACLR values are improved by a maximum of 12.8 dB and are constant up to the passband signal power of 40 dBm. In addition, to examine the power efficiency improvement offered by noise suppression of the HTS-RTF, numerical analyses based on measured results of gallium nitride HEMT power amplifier characteristics are conducted. The analyzed results shows the drain efficiency of the amplifier can be improved to 44.2% of the amplifier with the filter from the 15.7% of the without filter.

Hybrid predistortion to compensate third- and fifth-order intermodulation of a 2 GHz power amplifier using cuber predistortion and second harmonics injection

A new circuit construction technique that actively utilises second harmonics injection (HI) to realise fifth-order predistortion (PD) for power amplifiers (PAs) with memoryless AM/AM and AM/PM conversions is proposed. Applying a combination of the proposed technique and cuber predistortion (CPD) to third-order distortion yields the simultaneous compensation of both third- and fifth-order intermodulation distortion (IM3 and IM5); capabilities are not possible with the conventional third-order PD approach. Since the proposed method can be implemented as a simple analogue circuit, it betters compactness and lowers cost. In order to derive the PA bias condition at which second HI works most effectively, a complex power series nonlinear model that allows both amplitude and phase nonlinearities to be dealt with simultaneously is used. To confirm the author's compensation theory, a 2'GHz band PA and a hybrid lineariser that employs second HI and CPD are fabricated and experiments are performed. About a 20'dB simultaneous reduction in IM3 and IM5 is achieved with the two-tone test. A W-CDMA one-carrier test is also conducted to verify the improvement in adjacent channel leakage power ratio compared with CPD only.

Thermal Gain Variation Compensation Technique Using Thermistor on HPA Module for W-CDMA System

The thermal gain variation of a high-power amplifier (HPA) module for a wide-band code division multiple access (W-CDMA) system application was reduced to within ±1dB by applying a thermistor to compensate the gain variation. Two techniques for gain variation compensation with respect to temperature were investigated: base bias control according to temperature, and use of a thermistor in a matching network. Experimental comparison of two techniques indicated that the thermistor-based technique was more effective in reducing the gain variation without affecting linearity. A fabricated two-stage HPA module with a thermistor in its input matching network achieved a small gain variation within ±1dB and ±5MHz offset adjacent channel leakage power ratio (first ACLR) below -36dBc over the temperature range from -10 to +85°C, where the first ACLR was measured under a load-mismatched condition with a voltage standing wave ratio (VSWR) of 1.4 : 1.

A 5 GHz high-temperature superconducting reaction-type transmitting filter based uponsplit open-ring resonators

A new kind of high-temperature superconducting (HTS) transmitting filter based on areaction-type resonator is presented. The purpose of an HTS reaction-type filter(HTS-RTF) is to eliminate the intermodulation distortion noise generated by microwavepower amplifiers such as those employed in mobile base stations. An HTS-RTFenables both higher power handling capability and sharper cutoff characteristicscompared to existing planar-type HTS transmitting filters, since a reaction-typeresonator does not resonate with high power fundamental signals. To achieve steepskirt characteristics and high power handling capability simultaneously, a 5 GHzthree-pole HTS-RTF using a split open-ring resonator is designed. This splitopen-ring resonator offers low maximum current densities and a high-unloadedQ factor with low radiation. The designed prototype filter has Chebyshev characteristics with a centrefrequency of 4.95 GHz and a bandwidth of 1.5 MHz. The HTS-RTF is fabricated using a double-sidedYBa2C3O7−δ thin film deposited on a 0.5 mm thick MgO substrate. The measured filter shows aninsertion loss of less than 0.1 dB and a third intermodulation distortion value of−56.7 dBc for a 40 dBm passband signal. In addition, adjacent channel leakage power ratio(ACLR) measurements using an actual wideband CDMA signal confirm an ACLRimprovement of about 10 dB for a four-carrier signal with power up to 40 dBm.

RF Reconfigurable Predistorter for Power Amplifiers

This paper presents data on a reconfigurable predistorter for compensating the nonlinearity of a power amplifier in a system supporting both multimode and multiband operations. For compensation, the magnitude and phase response of a predistorter should be easy to tune to match that of a nonlinear amplifier that is used in various standards. That is to say, the predistorter should show decreasing magnitude followed by increasing magnitude, and the phase must initially lag and then lead, or lead and then lag, as a function of the increasing power input. In doing so, the power turning point, gain & phase deviation, and phase lead & lag should easily be controlled by the proposed reconfigurable predistorter using a bias control and impedance transformer. These characteristics are provided by the nonlinearity of the FET and the movement of the bias point caused by negative current generation. This proposed predistorter can be adopted for a system that uses Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA) 800MHz, and CDMA 1800MHz. For example, by adopting this reconfigurable predistorter in a CDMA 1800MHz, as much as 14 dB improvements in Adjacent Channel leakage Power Ratio (ACPR) at the 4 dB back off power level, can be achieved for the CDMA 1800MHz signal.

An HPSK/OFDM 64-QAM Dual-Mode Doherty Power Amplifier Module for Mobile Terminals

This paper presents a miniaturized dual-mode Doherty PA module applicable for an HPSK signal and an OFDM 64-QAM signal. Dual-mode operation with identical hardware is realized by introducing a bias switching technique, which changes bias conditions of amplifiers according to transmission signals, and employing dual-mode matching circuits, which are designed based on the results of load-pull measurements using an HPSK signal and an OFDM 64-QAM signal. The Doherty PA module consists of a Doherty stage and a gain stage. Two GaAs-HBTs for a Doherty stage and one GaAs-HBT for a gain stage are integrated onto a 1 mm-square single GaAs-MMIC. In the HPSK mode, maximum output power of 26.7 dBm, power added efficiency (PAE) of 41%, and power gain of 27 dB are obtained in the condition that adjacent channel leakage power ratio (ACLR) is under -38 dBc. In the OFDM 64-QAM mode, maximum output power of 21.0dBm, PAE of 27%, and power gain of 28 dB are obtained under EVM < 3.0%. This is the first multi-mode Doherty PA module suitable for multi peak to average power ratio (PAPR) signals.

Analysis and Design of a Dynamic Predistorter for WCDMA Handset Power Amplifiers

This paper presents a dynamic predistorter (PD), which linearizes the dynamic AM-AM and AM-PM of a wideband code division multiple access handset power amplifier (PA). The dynamic PD allows an adjacent channel leakage power ratio (ACPR) improvement of 15.7 dB, which is superior to conventional PDs that linearize static AM-AM and AM-PM. The dynamic PD was designed using an HBT generating nonlinearity, a short circuit at the baseband (les4 MHz), and a load circuit for the HBT at the RF fundamental band (ap1.95 GHz). Volterra-series analysis was performed to understand the mechanism of the dynamic PD. The analysis revealed that the short circuit at the baseband enabled the dynamic PD generating third-order intermodulation distortion (IMD3) with opposite phase to the fundamental tone (i.e., antiphase IMD3). The antiphase IMD3 allows dynamic gain compression, which linearizes the dynamic gain expansion of a PA with low quiescent current. The analysis also revealed that the IMD3 amplitude of the dynamic PD can be adjusted by load impedance at the RF fundamental band, which enables the gradient of dynamic AM-AM and AM-PM to be optimized to linearize the PA. The fabricated two-stage InGaP/GaAs HBT PA module with the dynamic PD exhibited an ACPR of -40 dBc and a power-added efficiency of 50% at an average output power of 26.8 dBm with a quiescent current of 20 mA

A low voltage W-CDMA polar transmitter with digital envelope path gain compensation

This letter presents a polar transmitter using a dual-phase pulsewidth-modulated buck converter with a 50-MHz effective switching frequency. Using a wideband code division multiple access voice signal, the overall system can achieve 52.8% drain efficiency (49.8% power added efficiency) at 24-dBm output power at 836.5MHz with a 3.5-V supply voltage, while passing both adjacent channel leakage power ratio (ACLR1) and alternate channel leakage power (ACLR2) specifications. A digital finite impulse response filter is included in the envelope path to compensate for gain roll-off at higher baseband frequencies. This envelope path compensation allows greater linear bandwidth to be achieved at lower switching frequencies, thus boosting efficiency, and improving ACLR by as much as 8dB. The polar transmitter is characterized over a supply voltage of 2.5-4.5V, making it well suited for battery powered, handheld applications

High Power GaN-HEMT for Wireless Base Station Applications

Highly reliable GaN high electron mobility transistors (HEMTs) are demonstrated for 3G-wireless base station applications. A state-of-the-art 250-W AlGaN/GaN-HEMTs push-pull transmitter amplifier operated at a drain bias voltage of 50 V is addressed with high efficiency under W-CDMA signals. The amplifier, combined with a digital pre-distortion (DPD) system, also achieved an adjacent channel leakage power ratio (ACLR) of less than -50 dBc for 4-carrier W-CDMA signals. Memory effect and temperature characteristics are also discussed. A stable operation including gate leakage current under RF stress testing for 1000 h is demonstrated at a drain bias voltage of 60 V. AlGaN/GaN HEMTs on an n-type doped 3-inch SiC substrate is introduced towards low cost manufacturing for the first time.

Low ACPR Characteristics for WCDMA Applications of SiGe:C HBT Devices with Small Emitter Capacitance

We present C-doped SiGe (SiGe:C) heterojunction bipolar transistor (HBT) devices that exhibit highly efficient and linear power characteristics comparable to those of GaAs HBTs under wide-band code-division multiple-access (WCDMA) modulation. Our devices have a novel resistor inserted in their base bias current pass, which is designed to short-circuits DC components of the base current and conducts only envelope frequency signals. The impurity concentration at their emitter-base junctions is reduced by the effect of C doping suppressing B diffusion, and the emitter capacitance is decreased to half that of conventional SiGe HBTs as the result. The combination of these two modifications has significantly reduced the adjacent channel power leakage ratio (ACPR), and the idle current, without degrading power-added-efficiency (PAE). An optimized device with a total emitter area of 3390 μm 2 exhibited 48% PAE and 27.4-dBm output power with an ACPR of less than -40 dBc at an idle current of 20 mA under WCDMA modulation at 1.95 GHz and 3.4-V bias voltage.

Simple, low-cost, subsystem fabrication

We have successfully developed a simple and low-cost 1.9-GHz, 25-W power amplifier by using only one prematched 50-mm PHEMT with external matching circuits on a FR-4 PCB. As the output stage integrated with other driver stages and dc control circuits, a completed four-stage power-amplifier subsystem is also demonstrated. When operating at 38.5-dBm output power with /spl pi//4-DQPSK signal, the proposed power amplifier subsystem shows low distortion, with better than 75-dBc ACPR (adjacent-channel leakage power ratio) at 600 kHz and 79-dBc ACPR at 900 kHz offset from the center frequency, and is suitable for PHS 500-mW base-station applications.

Highly Reliable 250 W GaN High Electron Mobility Transistor Power Amplifier

A state-of-the-art highly reliable 250 W AlGaN/GaN high electron mobility transistor (HEMT) push-pull transmitter amplifier operated at a drain bias voltage of 50 V is described. The amplifier, combined with a digital predistortion (DPD) system, also achieved an adjacent channel leakage power ratio (ACLR) of less than -50 dBc for 4-carrier wideband code division multiple access (W-CDMA) signals with a drain supply voltage of 50 V. I also demonstrate its stable operation under RF stress testing for 1000 h at a drain bias voltage of 60 V. Stable gate-leakage current for high-temperature operation was verified. Device fabrications on 4 inch sapphire and 3 inch semi-insulating (S.I.) SiC substrates were also addressed. These performances clarify that an AlGaN/GaN HEMTs amplifier is suitable for 3G W-CDMA systems.

InGaP/GaAs HBT power amplifier with CMRC structure

AbstractAn InGaP/GaAs heterojunction bipolar transistor (HBT) power amplifier is developed for WCDMA user equipment, specifically, band‐1‐power class‐2 application. The HBT power amplifier demonstrates maximum output power Pout of 29.4 dBm and power‐added efficiency (PAE) of 48% at a frequency of 1.95 GHz. When operated according to the WCDMA standard, it achieves Pout of 27 dBm and PAE of 32.4%. The adjacent channel leakage power ratio (ACLR) is −33 dBc. A compact microstrip resonant cell (CMRC) circuit is implemented on the HBT amplifier in order to further improve the PAE, ACLR, and IM3 performances. This results in improvements of 8 dB and 6% for the ACLR and PAE, respectively. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 84–88, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20908

Analysis and design of a high-efficiency multistage Doherty power amplifier for wireless communications

A comprehensive analysis of a multistage Doherty amplifier, which can be used to achieve higher efficiency at a lower output power level compared to the classical Doherty amplifier, is presented. Generalized design equations that explain the operation of a three-stage Doherty amplifier, which can be easily extended to an N-stage Doherty amplifier, are derived. In addition, the optimum device periphery, which minimizes AM-AM distortion for perfect Doherty amplifier operation, is analyzed. For the first time, a multistage Doherty power amplifier that meets wide-band code-division multiple-access (WCDMA) requirements is demonstrated. The designed power amplifier exhibits a power-added efficiency (PAE) of 42% at 6-dB output power backoff and 27% at 12-dB output power backoff. These PAEs are more than 2/spl times/ and 7/spl times/ better, respectively, than that of a single-stage linear power amplifier at the same output power backoff levels. The power amplifier is capable of delivering up to 33 dBm of output power, and has a maximum adjacent channel power leakage ratio of -35 and -47 dBc at 5- and 10-MHz offset, respectively. To the best of the authors' knowledge, these represent the best reported results of a Doherty amplifier for WCDMA application in the 1.95-GHz band to date.

A highly efficient Doherty feedforward linear power amplifier for W-CDMA base-station applications

This paper presents a RF high-power Doherty amplifier for improving the efficiency of a 30-W feedforward linear amplifier used in wide-band code-division multiple-access (W-CDMA) base-station applications. A high-power Doherty amplifier using a single push-pull LDMOS field-effect transistor is proposed as the main amplifier of a feedforward linear amplifier. The peaking amplifier's compensation line and gate bias effects are analyzed at the 6-dB backoff point. From the experimental results of a forward-link one-carrier W-CDMA, a 2.2% power-added efficiency improvement at an adjacent channel leakage power ratio linearity of -60 dBc is achieved in comparison to a conventional feedforward class-AB amplifier.

An InGaP-GaAs HBT MMIC smart power amplifier for W-CDMA mobile handsets

We demonstrate a new linearized monolithic microwave integrated circuit smart power amplifier of extraordinary high power-added efficiency (PAE), especially at the most probable transmission power of wide-band code-division multiple-access handsets. A PAE of 21% at 16 dBm of output power, which is the maximum bound of the most probable transmission power in IS-95 systems, was obtained, as well as 40% at 28 dBm, the required maximum output power, with a single-chip MMIC power amplifier. The power amplifier has been devised with two InGaP-GaAs heterojunction bipolar transistor amplifying chains parallel connected, each chain being optimized for a different P/sub 1dB/ (1-dB compression point) value: one for 16 dBm for the low-power mode, targeting the most probable transmission power, and the other for 28 dBm for the high-power mode. The high-power mode operation shows 40% of PAE and -30 dBc of adjacent channel leakage power ratio (ACLR) at the maximum output power of 28 dBm. The low-power mode operation exhibits -34 dBc of ACLR at 16 dBm with 14 mA of a quiescent current. This amplifier improves power usage efficiency and, consequently, the battery lifetime of the handset by a factor of three.

Prediction of nonlinear distortion in HTS filters for CDMA communication systems

HTS materials are known to produce intermodulation and other nonlinear effects, and this may restrict their use in wireless communication systems. While significant efforts are being done to measure and characterize nonlinear properties of HTS materials, there are very few works that relate these properties to system parameters. In this work we attempt to bridge this gap by using harmonic balance algorithms to analyze the nonlinear performance of superconducting filters subject to the WCDMA signals specified by 3GPP for the UMTS wireless system. This is a first step to predict compliance with system parameters like adjacent channel leakage power ratio (ACLR) or error vector magnitude (EVM).

Linearised HBT MMIC power amplifier with partially RF coupled active bias circuit for W-CDMA portable terminals applications

A highly linear MMIC power amplifier for wideband code-division multiple-access (W-CDMA) portable terminals has been devised and implemented with a new integrated on-chip lineariser. The proposed lineariser, consisting of an InGaP/GaAs heterojunction bipolar transistor (HBT) active bias circuit partially coupled to RF input power together with a feedback capacitor, effectively improves gain compression with little insertion power loss and no additional die area. The optimised lineariser improves maximum output power (P1 dB) by 2 dB and adjacent channel leakage power ratio (ACLR) by 4 dB, and the implemented HBT MMIC power amplifier exhibits a P1 dB of 30 dBm, a power gain of 30 dB, a power added efficiency of 42% at the maximum output power under an operation voltage of 3.4 V, and an ACLR of -34 dBc at 27 dBm of output power.