M. Pelk

Adaptive Multi-Band Multi-Mode Power Amplifier Using Integrated Varactor-Based Tunable Matching Networks

This paper presents a multi-band multi-mode class-AB power amplifier, which utilizes continuously tunable input and output matching networks integrated in a low-loss silicon-on-glass technology. The tunable matching networks make use of very high Q varactor diodes (Q>100 @ 2 GHz) in a low distortion anti-series configuration to achieve the desired source and load impedance tunability. A QUBIC4G (SiGe, ft=50 GHz) high voltage breakdown transistor (VCBO=14 V, VCEO>3.6 V) is used as active device. The realized adaptive amplifier provides 13 dB gain, 27-28 dBm output power at the 900, 1800, 1900 and 2100 MHz bands. For the communication bands above 1 GHz optimum load adaptation is facilitated resulting in efficiencies between 30%-55% over a 10 dB output power control range. The total chip area (including matching networks) of the amplifier is 8 mm2

A High-Efficiency 100-W GaN Three-Way Doherty Amplifier for Base-Station Applications

A three-way Doherty 100-W GaN base-station power amplifier at 2.14 GHz is presented. Simple, but accurate design equations for the output power combiner of the amplifier are introduced. Mixed-signal techniques are utilized for uncompromised control of the amplifier stages to optimize efficiency, as well as linearity. The combination of the above techniques resulted in an unprecedented high efficiency over a 12-dB power backoff range, facilitating a record high power-added efficiency for a wideband code division multiple access test signal with high crest factor, while meeting all the spectral requirements for Universal Mobile Telecommunications System base stations.

A 90-W Peak Power GaN Outphasing Amplifier With Optimum Input Signal Conditioning

A 90-W peak-power 2.14-GHz improved GaN outphasing amplifier with 50.5% average efficiency for wideband code division multiple access (W-CDMA) signals is presented. Independent control of the branch amplifiers by two in-phase/quadrature modulators enables optimum outphasing and input power leveling, yielding significant improvements in gain, efficiency, and linearity. In deep-power backoff operation, the outphasing angle of the branch amplifiers is kept constant below a certain power level. This results in class-B operation for the very low output power levels, yielding less reactive loading of the output stages, and therefore, improved efficiency in power backoff operation compared to the classical outphasing amplifiers. Based on these principles, the optimum design parameters and input signal conditioning are discussed. The resulting theoretical maximum achievable average efficiency for W-CDMA signals is presented. Experimental results support the foregoing theory and show high efficiency over a large bandwidth, while meeting the linearity specifications using low-cost low-complexity memoryless pre-distortion. These properties make this amplifier concept an interesting candidate for future multiband base-station implementations.

A Mixed-Signal Approach Towards Linear and Efficient

A mixed-signal approach for the design and testing of high-performance N-way Doherty amplifiers is introduced. In support of this, an analysis of N-way power-combining networks is presented-in particular, their optimum design-by examining the relationship between the drive conditions of the active devices and input power. This analysis makes no prior assumption on the network topology and facilitates free-to-choose levels for the high-efficiency power back-off points. By comparing the results of this analysis with prior work, it is shown that very specific drive conditions apply to traditional three-way Doherty amplifier implementations to obtain simultaneously high-efficiency and high-linearity operation. To support these conclusions, a 15-W three-way Doherty amplifier was constructed using Philips GEN4 LDMOS devices featuring three separate inputs to independently drive the main and peaking devices. By testing this three-way amplifier with a custom-built measurement setup, capable of providing multiple digitally controlled coherent RF input signals with high spectral purity, a unique flexible amplifier concept is created resulting in a record-high efficiency for LDMOS-based Doherty amplifiers over a 12-dB back-off power range

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A new wideband open-loop active harmonic load-pull measurement approach is presented. The proposed method is based on wideband data-acquisition and wideband signal-injection of the incident and device generated power waves at the frequencies of interest. The system provides full, user defined, in-band control of the source and load reflection coefficients presented to the device-under-test at baseband, fundamental and harmonic frequencies. The system capability to completely eliminate electrical delay allows to mimic realistic matching networks using their measured or simulated frequency response. This feature enables active devices to be evaluated for their actual in-circuit behavior, even on wafer. Moreover the proposed setup provides the unique feature of handling realistic wideband communication signals like multicarrier wideband code division multiple access (W-CDMA), making the setup perfectly suited for studying device performance in terms of efficiency, linearity and memory effects.

-Way Doherty Amplifiers

In this paper, we present an active harmonic load-pull system especially developed for the on-wafer linearity characterization/optimization of active devices with wideband modulated signals using the out-of-band linearization technique. Our setup provides independent control of the impedances at the baseband, fundamental, and second-harmonic frequencies presented to the input and output of the device under test. Furthermore, to enable realistic test conditions with wideband-modulated signals, the electrical delays in the load-pull system are kept as small as possible by implementing a novel loop architecture with in-phase quadrature modulators. We have achieved a phase variation of the reflection coefficient of only 5deg/MHz for both the fundamental and second-harmonic frequencies. We demonstrate the high potential of the system for the on-wafer evaluation of new technology generations by applying out-of-band linearization to heterojunction bipolar transistor (HBT) and laterally diffused metal-oxide-semiconductor (LDMOS) devices. For the HBT, we outline a game plan to obtain the optimum efficiency-linearity tradeoff. Finally, a record-high efficiency-linearity tradeoff was achieved (without digital predistortion) for an inverse class-AB operated Philips Gen 6 LDMOS device, yielding 44% efficiency at an adjacent channel power level of -45 dBc at 2.14 GHz for an IS-95 signal

Active Harmonic Load–Pull With Realistic Wideband Communications Signals

An optimization procedure based on load-pull measurements to obtain both highly-linear and highly-efficient class-AB operation is presented. This procedure can be applied without any foregoing device characterization; therefore it is an excellent method to compare the linearity performance of different bipolar technologies. The presented approach provides the optimum out-of-band terminations and quiescent current yielding IM3 improvement of more than 15 dBc at 3 dB back-off compared to traditional design techniques. Optimum power-added efficiency is achieved at the same time.

Active Harmonic Load–Pull for On-Wafer Out-of-Band Device Linearity Optimization

We present a technology for the manufacturing of silicon-filled integrated waveguides enabling the realization of low-loss high-performance millimeter-wave passive components and high gain array antennas, thus facilitating the realization of highly integrated millimeter-wave systems. The proposed technology employs deep reactive-ion-etching (DRIE) techniques with aluminum metallization steps to integrate rectangular waveguides with high geometrical accuracy and continuous metallic side walls. Measurement results of integrated rectangular waveguides are reported exhibiting losses of 0.15 dB/ λg at 105 GHz. Moreover, ultra-wideband coplanar to waveguide transitions with 0.6 dB insertion loss at 105 GHz and return loss better than 15 dB from 80 to 110 GHz are described and characterized. The design, integration and measured performance of a frequency scanning slotted-waveguide array antenna is reported, achieving a measured beam steering capability of 82 ° within a band of 23 GHz and a half-power beam-width (HPBW) of 8.5 ° at 96 GHz. Finally, to showcase the capability of this technology to facilitate low-cost mm-wave system level integration, a frequency modulated continuous wave (FMCW) transmit-receive IC for imaging radar applications is flip-chip mounted directly on the integrated array and experimentally characterized.

Experimental procedure to optimize out-of-band terminations for highly linear and power efficient bipolar class-AB RF amplifiers

Absnacf This paper introduces a direct and accurate method for controlling and measuring the on-wafer device terminations at the base-hand / envelope frequency, using an extension of a conventional network analyzer setup. The base-hand impedance can he adjusted manually as well as electronically and is able to (over)compensate the losses in the measurement setup. This facilitates on-wafer base-hand terminations ranging from negative tu high Ohmic values. The proposed measurement techniques are particularly useful when characterizing active devices for their linearity.

Silicon-Filled Rectangular Waveguides and Frequency Scanning Antennas for mm-Wave Integrated Systems

Design trade-offs are presented for varactor-based variable phase-shifters in terms of size, tuning range, bandwidth/phase linearity and large-signal performance. Based on this study, a compact, low-loss (0.6dB/90deg @ 1.0 GHz), wideband and extremely linear varactor-based phase shifter is presented.