M.P. van der Heijden

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 novel frequency-independent third-order intermodulation distortion cancellation technique for BJT amplifiers

Second-harmonic control is implemented in a balanced common-emitter configuration to facilitate frequency-independent third-order intermodulation distortion cancellation. Moreover, this circuit configuration facilitates a simultaneous match for either power and linearity or noise and linearity. Experiments demonstrated an improvement of over 15 dB in the output third-order intercept point while maintaining freedom in the choice of load and source impedance.

On the design of unilateral dual-loop feedback low-noise amplifiers with simultaneous noise, impedance, and IIP3 match

This work describes the theory and design of a nonenergetic dual-loop feedback low-noise amplifier (LNA) that provides maximum unilateral gain and simultaneous noise and impedance matching conditions. The dual-loop feedback is implemented in the form of transformer current-feedback and inductive series feedback (emitter degeneration). The current-feedback transformer is also used to neutralize the base-collector capacitance (C/sub bc/), by combining it with a properly dimensioned shunt admittance at the collector output. The result is a single-transistor unilateral-gain amplifier with high isolation and good stability, eliminating the need for a cascode stage and thus enableing the use of a lower dc-supply voltage. For the complete LNA, simple design equations are derived for the unilateralization, noise, and impedance matching requirements. Finally, second-harmonic tuning at the source improves the linearity without compromising the simultaneous noise and impedance match. To verify the presented theory, a 900-MHz hybrid Si BJT LNA has been implemented, which achieves 1.3-dB noise figure, 15-dB gain, -55dB isolation, and +10dBm IIP3 using a conventional double poly transistor, consuming I/sub C/=2.5 mA at V/sub CE/=1.5 V.

Theory and design of an ultra-linear square-law approximated LDMOS power amplifier in class-AB operation

This paper describes a power amplifier, employing parallel-connected laterally diffused metal-oxide semiconductor (LDMOS) devices with optimized channel widths and bias offsets to approximate ideal square-law behavior of the overall transconductance in class-AB operation. The proposed method results in a significant linearity improvement over a large dynamic range in comparison to a conventional amplifier in class-A or class-AB operation. Measurements demonstrate an improvement of 20 dB in third-order intermodulation distortion and 10 dB in adjacent channel power ratio for wide-band code-division multiple access at 12-dB output power backoff from the 1-dB gain compression point. Consequently, this amplifier can be operated more toward the compression region with better linearity and drain efficiency compared to a conventional LDMOS power-amplifier design.

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

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.

A 2 GHz high-gain differential InGaP HBT driver amplifier matched for high IP3

A 2GHz single-stage linear InGaP HBT differential driver amplifier is presented operating at I/sub C/ = 30mA and V/sub C/ = 3V. The amplifier utilizes a collector-base capacitance neutralization technique, yielding a maximum stable gain of 30dB at 2GHz. Furthermore, second-harmonic control is implemented in the in- and output terminations yielding a 20dB reduction of third-order intermodulation distortion (IM3). Moreover, the well-defined second-order terminations result in a good symmetry of the lower and upper IM3 side bands.

A calibration procedure for on-wafer differential load-pull measurements

This paper presents a calibration technique for on-wafer diflerential load-pull measurements. The described calibration procedure makes use of a standard GS/SG calibration substrate only. The calibration accuracy achieved is verified through various independent standards measurement.

Ultra-linear distributed class-AB LDMOS RF power amplifier for base stations

This paper describes a distributed amplifier, employing multiple parallel-connected LDMOS devices with optimized overall transconductance for class-AB operation. In comparison to a conventional amplifier under class-A and class-AB conditions the design method results in a significant linearity improvement over a large dynamic range. Measurements demonstrate a linearity improvement of 20 dB in 3/sup rd/-order intermodulation distortion (IM3) and 10 dB in adjacent channel power ratio (ACPR) for a wideband CDMA signal. Consequently, a reduction in the required back-off level has been achieved.

Linearity optimization of a distributed base station amplifier using an automated high-speed measurement protocol

This paper describes a high-speed measurement protocol using a high-order implementation of the complex power series representation (CPSR). The CPSR is used to relate AM-AM and AM-PM conversion (large signal S/sub 21/) to the 3rd-order intermodulation distortion (IM3) of an amplifier up to gain compression. This method requires the use of a network analyzer only and eliminates the need for a spectrum analyzer speeding-up the measurements tremendously. The method has proven to be very powerful in a real-time optimization of bias parameter of a novel linear distributed amplifier for base stations.

A novel frequency independent third-order intermodulation distortion cancellation technique for BJT amplifiers

Second-harmonic control is implemented in a balanced common-emitter configuration to facilitate frequency independent third-order intermodulation distortion (IM3) cancellation. Experiments demonstrated an over 15 dB improvement in the output third-order intercept point (OIP3).Second-harmonic control is implemented in a balanced common-emitter configuration to facilitate frequency independent third-order intermodulation distortion (IM3) cancellation. Experiments demonstrated an over 15 dB improvement in the output third-order intercept point (OIP3).