Jinseong Jeong

Wideband Envelope Tracking Power Amplifiers With Reduced Bandwidth Power Supply Waveforms and Adaptive Digital Predistortion Techniques

This paper presents a new technique to reduce the bandwidth of the dynamic power supply waveform used in wideband envelope tracking power amplifiers (PAs). When the envelope tracking technique is applied to broadband signals such as WCDMA and 3GPP LTE, the wide bandwidth of the envelope signal makes it difficult to implement the dynamic supply modulator efficiently and accurately. We show here a technique to reduce the bandwidth of the power supply waveform, thereby allowing better efficiency for the supply modulator; and a linearization method for correcting the nonlinearity caused by the bandwidth reduction. The feasibility of this technique is demonstrated for a single carrier WCDMA signal with a 7.6-dB peak-to-average power ratio using a GaAs high-voltage HBT PA. The bandwidth of the power supply waveform is reduced from 20 to 4 MHz. After linearization, the reduced bandwidth envelope tracking PA exhibits an average output power of 28 W, an average gain of 12 dB and an overall power-added efficiency of 49%. The measured normalized rms error is as low as 0.67% with an adjacent channel leakage ratio of -53.9 and -54.2 dBc at offset frequencies of 5 and 10 MHz, respectively.

High Efficiency Envelope Tracking LDMOS Power Amplifier for W-CDMA

A high performance W-CDMA base station power amplifier is presented, which uses an envelope tracking bias system along with an advanced 0.4mum gate length LDMOS transistor, to achieve high efficiency. High linearity is also achieved by employing digital predistortion. For a target WCDMA envelope with a peak-to-average power ratio of 7.6 dB, the measured overall power-added efficiency (PAE) is as high as 40.4 %. Within this system, the RF power amplifier has an average drain efficiency of approximately 64%, and the envelope amplifier has about 60% efficiency. After the memoryless digital predistortion the normalized power RMS error is 3.3%, at an average output power of 27 W and gain of 14.9 dB. After memory mitigation the normalized power RMS error drops to below 1.0%. The efficiency ranks among the highest reported for a single stage LDMOS W-CDMA base station amplifier

Modeling and Design of RF Amplifiers for Envelope Tracking WCDMA Base-Station Applications

Wideband code division multiple access (WCDMA) base-station RF amplifiers using a variety of device technologies including GaN field-effect transistors (FETs), Si LDMOS, and GaAs high-voltage heterojunction bipolar transistors (HVHBTs) are modeled, optimized, and compared for use in wideband envelope tracking (ET) system. A quasi-static approach is employed to effectively model the supply-modulated RF amplifiers, and thus facilitate the design optimization process. A new design methodology for ET RF amplifiers is introduced including identification of optimum fundamental and harmonic terminations. The fundamental and harmonic impedances have been successfully optimized for various RF devices and good agreement has been achieved between the simulation and measurement results. Among the modeled and measured ET RF amplifiers, a GaAs HVHBT exhibits the best overall efficiency of 60% with an average output power of 33 W and a gain of 10 dB for a WCDMA signal with 3.84-MHz bandwidth and 7.7-dB peak-to-average power ratio, while meeting all linearity requirements of the WCDMA standard. Desirable device characteristics for optimum ET operation are also discussed.

Wideband envelope tracking power amplifier with reduced bandwidth power supply waveform

This paper presents a new technique to reduce the bandwidth of the dynamic power supply waveform for use in wideband envelope tracking power amplifiers (PAs). When the envelope tracking technique is applied to the broadband signals such as WiMAX and LTE, the wide bandwidth of the envelope signal makes it difficult to implement the dynamic power supply efficiently and accurately. We show here for the first time a technique to reduce the bandwidth of the dynamic power supply voltage, thereby allowing better efficiency for the dynamic power supply; and a linearization method for correcting the nonlinearity caused by the bandwidth reduction. The feasibility of this technique is demonstrated for a single carrier WCDMA signal with 7.8-dB PAPR using a GaAs HVHBT PA. The bandwidth of the power supply signal is reduced from 20 MHz to 5 MHz. After linearization, the reduced bandwidth envelope tracking PA exhibits an average output power of 25 W, an average gain of 13 dB and an overall power-added efficiency of 50%. The measured normalized RMS error is as low as 3.98% with an adjacent channel leakage ratio of −41 dBc and −48 dBc at offset frequencies of 5 MHz and 10 MHz, respectively.

High Efficiency WCDMA Envelope Tracking Base-Station Amplifier Implemented with GaAs HVHBTs

A record high-performance GaAs high-voltage HBT (HVHBT)-based WCDMA base-station power amplifier is presented, which uses an envelope tracking bias system to achieve high efficiency and linearity. A wideband envelope amplifier provides dynamic collector supply biasing to the RF stage. A digital pre-distortion technique is employed to satisfy the linearity specifications of WCDMA. The measured overall power-added efficiency reached 58% with a normalized root-mean-square (RMS) error of 2.9% and an adjacent channel leakage ratio (ACLR) of -49 dBc at 5-MHz offset at an average output power of 42 W and a gain of 10.3 dB for a single carrier WCDMA signal with 6.6-dB peak-to-average power ratio. A memory mitigation algorithm further improves the linearity, resulting in an ACLR of -70 dBc and a normalized RMS error of 0.3%. Measurements were made to quantify separately the efficiency contributions of the HVHBT-based RF stage, and of the envelope amplifier. The measurements show that the RF stage operates at collector efficiency above 85% over most of the instantaneous power range of the WCDMA signal. This remarkably high efficiency is the result of low ldquoon-resistancerdquo and low (and nearly voltage independent) output capacitance of the HVHBT.

Inactivation of Pseudomonas aeruginosa biofilm by dense phase carbon dioxide

Dense phase carbon dioxide (DPCD) is one of the most promising techniques available to control microorganisms as a non-thermal disinfection method. However, no study on the efficiency of biofilm disinfection using DPCD has been reported. The efficiency of DPCD in inactivating Pseudomonas aeruginosa biofilm, which is known to have high antimicrobial resistance, was thus investigated. P. aeruginosa biofilm, which was not immersed in water but was completely wet, was found to be more effectively inactivated by DPCD treatment, achieving a 6-log reduction within 7 min. The inactivation efficiency increased modestly with increasing pressure and temperature. This study also reports that the water-unimmersed condition is one of the most important operating parameters in achieving efficient biofilm control by DPCD treatment. In addition, observations by confocal laser scanning microscopy revealed that DPCD treatment not only inactivated biofilm cells on the glass coupons but also caused detachment of the biofilm following weakening of its structure as a result of the DPCD treatment; this is an added benefit of DPCD treatment.

Envelope tracking power amplifiers with reduced peak-to-average power ratio RF input signals

This paper presents a new technique to reduce the peak-to-average power ratio (PAPR) of the RF input signals used in envelope tracking (ET) power amplifiers without degrading the linearity and efficiency performance of the RF stages. Due to heavy gain compression, ET amplifiers can suffer from inefficient driver stages. The reduced PAPR RF input signal improves the efficiency of the driver amplifier thereby potentially improving the overall efficiency of the ET amplifier. This technique is demonstrated for a single carrier WCDMA signal using a dynamic supply modulator and a RF stage based on a GaAs HVHBT. The measurement shows that a power added efficiency (PAE) of 74% can be maintained for the RF stage while the PAPR of the RF input signal is reduced from 7.6 dB to 5.2 dB. The overall PAE accounting for the supply modulator is greater than 50% with an average output power of greater than 26 W and an adjacent channel leakage ratio of less than −45 and −53 dBc at 5- and 10-MHz frequency offsets, respectively.

High efficiency wideband envelope tracking power amplifier with direct current sensing for LTE applications

A high efficiency wideband envelope tracking power amplifier for LTE applications is presented. The CMOS envelope amplifier with direct current sensing has a measured average efficiency of 78% with a 5 MHz LTE signal. The envelope tracking power amplifier including a GaAs HBT RF stage has overall power added efficiency (PAE) above 46% with an average LTE output power of 27.6 dBm and a gain of 26.5 dB.