Yong-Sub Lee

A High-Efficiency Class-E GaN HEMT Power Amplifier for WCDMA Applications

This letter reports a high efficiency class-E power amplifier using a GaN high electron mobility transistor (HEMT), which is designed at WCDMA band of 2.14 GHz. To improve output power and efficiency by suppressing harmonic powers, an output network using transmission lines is used. For a single tone, the proposed output network suppresses all harmonic power levels below -60 dBc for the whole output power range. The peak power-added efficiency (PAE) of 70% with a power gain of 13 dB is achieved at an output power of 43 d Bin. The broadband performance with a power gain over 12 dB and PAE over 60% is maintained through 200 MHz.

High-Efficiency Class-F GaN HEMT Amplifier With Simple Parasitic-Compensation Circuit

This letter presents a highly efficient class-F power amplifier (PA) using a GaN high electron mobility transistor, which is designed at WCDMA band of 2.14 GHz. The simple and effective compensation circuit consisting of a series capacitor and a shunt inductor is used to compensate for the internal parasitic components of the packaged transistor. Also, the composite right/left-handed transmission lines are used as the harmonic tuner of the class-F PA. From the measured results for a continuous wave, the drain efficiency and power-added efficiency of 75.4% and 70.9% with a gain of 12.2 dB are achieved at an output power of 40.2 dBm.

Unequal-Cells-Based GaN HEMT Doherty Amplifier With an Extended Efficiency Range

This letter reports an extended GaN HEMT Doherty power amplifier (DPA). For high efficiency over a wide output power range, the DPA is designed using two cells with unequal saturation power (Psat). A cell with lower Psat is used as the carrier cell. For experimental validations, the carrier and peaking cells are designed and implemented with 25 W GaN HEMTs at wide-band code division multiple access (WCDMA) of 2.14 GHz, and then show the Psat of 41.3 dBm and 43.6 dBm, respectively. For the proposed DPA, the single-tone results show the power-added efficiency (PAE) of 50% at an output power of 37.3 dBm (9 dB back-off power from Psat). For a one-carrier WCDMA signal, the PAE of 47.9% with an adjacent channel leakage ratio of -35.8 dBc is obtained at 37.3 dBm, which is 7.9% improvement compared to the conventional DPA. The PAE of 40% is maintained over an 11.4 dB back-off power.

Highly Linear Predistortion Power Amplifiers With Phase-Controlled Error Generator

A simple predistortion technique to cancel the fifth-order intermodulation (IM5) as well as third-order intermodulation (IM3) components using a third-order predistorter (PD) is represented. The IM3 and IM5 components are cancelled out simultaneously by their same magnitude and phase difference in the PD and power amplifier (PA). Moreover, this phase difference is controlled by using the phase-controlled error generator in the PD. For experimental verification, a third-order PD has been implemented and tested in a 30-W class-AB PA at the wide-band code division multiple access (WCDMA) band of 2.11-2.17GHz. Two-tone test results show that significant cancellation of the IM3 and IM5 components can be obtained. For a four-carrier WCDMA application, significant adjacent channel leakage ratio improvement is achieved over a wide range of output power levels

An adaptive predistortion RF power amplifier with a spectrum monitor for multicarrier WCDMA applications

This paper presents an adaptive predistortion RF power amplifier for repeater systems with a spectrum monitor. For adaptive control of cancellation, we implement a spectrum monitor that improves the adjacent channel leakage ratio (ACLR) characteristics of the power amplifier by analyzing the output spectrums of RF power amplifiers directly and simultaneously. For experimental validation, we also implement a class-AB RF power amplifier that adopts a predistortion linearizer with the spectrum monitor and measure the characteristics for the wide-band code division multiple access (WCDMA) band. With an optimum gate bias voltage of the power amplifier, ACLRs of 22 and 20.5 dB are improved for the cases of one- and four-carrier WCDMA applications, respectively. The predistortion power amplifier with the spectrum monitor delivers a Pout of 37.5 dBm with an ACLR of -45 dBc for four-carrier WCDMA applications. Furthermore, excellent ACLR characteristics are consistently maintained with the minimization algorithm by adaptively controlling the vector modulator in the predistorter under various environments that include varying input power levels, temperatures, and operating frequencies

A New Wideband Distributed Doherty Amplifier for WCDMA Repeater Applications

A new wideband distributed Doherty amplifier (WDDA) for wideband code division multiple access (WCDMA) repeater applications is reported. The distributed structure provides wideband performance while not needing an N-way splitter and combiner. The two-stage Doherty amplifiers achieve high gain and high efficiency. Also, the linearity of the WDDA is improved by the post-distortion using gate bias optimization of the Doherty amplifiers. For verification, the proposed WDDA is implemented using GaN HEMTs and tested with a one-carrier WCDMA signal at 2.14 GHz. From the measured results at an average output power of 36 dBm (10 dB back-off power), the WDDA shows an adjacent channel leakage ratio (ACLR) of - 45 dBc at plusmn 5 MHz offset with a total gain over 24 dB and a total power-added efficiency over 15% over a 160 MHz bandwidth.

Applications of GaN HEMTs and SiC MESFETs in High Efficiency Class-E Power Amplifier Design for WCDMA Applications

This paper presents high efficiency class-E power amplifiers using wide-bandgap devices such as GaN HEMT and SiC MESFET, which are designed at WCDMA band of 2.14 GHz. The output network using transmission lines is implemented to suppress harmonics and minimize losses. Measured results of the class-E power amplifier using wide-bandgap devices for a single tone have been compared to that of the class-E Si LDMOS power amplifier. For GaN HEMT and SiC MESFET cases, the power-added efficiency (PAE) of 70% with a gain of 13.0 dB and 72.3% with a gain of 10.3 dB are achieved at an output power of 43.0 dBm and 40.3 dBm, respectively, through significant reduction of harmonic power levels.

A novel phase measurement technique for IM3 components in RF power amplifiers

This paper presents a novel measurement technique to measure the phases of intermodulation (IM) components of RF power amplifiers (PAs) with low-cost. This method can measure the phase distortions of the third-order IM components, as well as the fundamental signals generated in the PAs themselves by directly comparing the respective IM components before and after the PAs. A 45-W RF PA with an LDMOSFET in the wide-band code-division multiple-access band is implemented, and the relative changes of the IM phases of the PA are presented under various tone spacings, output power levels, and gate bias voltages. This system is very convenient for evaluating the memory effects of the PAs, and is helpful for the design of predistortion PAs and for the model extraction of PAs

Highly Efficient Doherty Amplifier Based on Class-E Topology for WCDMA Applications

This letter reports a high-efficiency gallium nitride (GaN) high-electron mobility transistor (HEMT) Doherty power amplifier (DPA) based on the class-E topology for wideband code-division multiple-access (WCDMA) applications. The class-E topology is employed as the carrier and peaking cells of the Doherty configuration. For validations, the proposed DPA is designed and implemented with 25-W GaN HEMTs at 2.14 GHz. For the proposed DPA, the power-added efficiency (PAE) and drain efficiency of 56.1% and 61.2% are achieved at 40 dBm (6-dB backoff power from Psat) for a continuous wave. For a 1-carrier WCDMA signal, the PAE of 44.8% is obtained with an adjacent channel leakage ratio (ACLR) of -31 dBc at 37 dBm, which is an 8.9% improvement over the conventional DPA with an ACLR of -36.4 dBc.

Highly Linear Power Tracking Doherty Amplifierfor WCDMA Repeater Applications

This letter presents a highly linear power tracking Doherty power amplifier (DPA) for wide-band code division multiple access (WCDMA) repeater system. To achieve maximum linearity without extra linearization circuits, the drain bias voltages of the carrier and peaking amplifiers as well as the gate bias voltage of the peaking amplifier are adaptively controlled using the power tracking method according to average power level of the input signal. For experimental verification, a two-way DPA has been implemented at the WCDMA band of 2.11~2.17 GHz and tested using one-tone, two-tone, and four-carrier WCDMA signals. Two-tone and WCDMA test results show the notable cancellation of the IM3 and IM5 components and the significant improvement in adjacent channel leakage ratio over a wide range of output power levels.