Mun-Woo Lee

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.

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.

Design of Highly Efficient Three-Stage Inverted Doherty Power Amplifier

This letter reports the highly efficient three-stage inverted Doherty power amplifier (IDPA) using 30 W and 50 W Si LDMOSFETs. The characteristic impedances of the output combiner are derived to achieve high efficiency at a large back-off power (BOP). The output matching networks and offset lines of the carrier and peaking cells are used to modulate the load impedance. The transmission line in the input path of the carrier cell is inserted to adjust the delay among the carrier and peaking cells. The drain efficiency (DE) of 40.3% with a gain of 9 dB is achieved at output power of 42 dBm (8.5 dB BOP) and the DE above 40% is maintained in wide output range for a 2.14 GHz continuous wave signal. For a one-carrier WCDMA signal at an output power of 40 dBm (10.5 dB BOP), the DE of 35% with the gain of 9.2 dB is achieved.

A Highly Efficient Three-Stage Doherty Power Amplifier with Flat Gain for WCDMA Applications

A three-stage Doherty power amplifier (DPA) with a flat gain is represented. The driving amplifier at an input of peaking cells is used to achieve high efficiency and flat gain to control the input power level of peaking cells. For the experimental validation, the proposed DPA is implemented using a GaN HEMT and Si LDMOSFETs. For a continuous wave signal, power-added efficiencies of 34.0% and 39.3% are obtained at 8.5-dB back-off power (BOP) and 4.0-dB BOP from the saturation output power, respectively. The measured one-carrier wideband code division multiple access results show high efficiency and flat gain characteristics above 10 dB over the entire output power range.

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.

A High-Efficiency GaN-Based Power Amplifier Employing Inverse Class-E Topology

A high efficiency, GaN based power amplifier (PA) employing the inverse class-E topology is reported. The parasitic inductance and large output capacitance of the packaged active device are used as the series inductance and compensated by a shunt inductor, respectively. The composite right/left-handed transmission line is used as a harmonic control network. For the experimental validation, an inverse class-E PA is designed using a GaN HEMT and tested with a continuous wave at 1 GHz. From the measured results, the drain efficiency and power-added efficiency (PAE) of 79.7% and 78.8% with a gain of 19.03 dB is achieved at an output power of 41.03 dBm. Also, the inverse class-E PA can deliver the output power and PAE of over 40.8 dBm and 65% through the bandwidth of 100 MHz.

Highly linear and efficient asymmetrical Doherty power amplifiers with adaptively bias-controlled predistortion drivers

A highly linear and efficient asymmetrical Doherty power amplifier (ADPA) with adaptively bias-controlled predistortion drivers (PDDs) is represented for 2.14-GHz wide-band code division multiple access (WCDMA) repeater systems. The ADPA shows the extended efficiency range by using unequal saturation powers of the main carrier and peaking cells. The driving carrier and peaking cells are used as the PDDs with the adaptive gate bias control to improve the linearity of the ADPA. To verify the proposed method, two 2-W GaN HEMTs and two 20-W GaN HEMTs are used as the driving and main cells, respectively. For a one-carrier WCDMA signal, the ADPA with PDDs produces an adjacent channel leakage ratio (ACLR) of −51.5 dBc with a total drain efficiency of 27.9% and a total gain of 28.7 dB by adaptively controlling the gate biases of PDDs. For the asymmetrical class-F DPA with PDDs, an ACLR of −38.2 dBc is achieved the total drain efficiency of 37.2 % and a total gain of 26.5 dB.

A Wideband Analog Predistortion Power Amplifier With Multi-Branch Nonlinear Path for Memory-Effect Compensation

A wideband, multi-branch analog predistorter (MBAPD) is reported to compensate for memory effects as well as memoryless nonlinearity of the power amplifier (PA) for repeater systems with wideband modulated signals. For verification, the MBAPD with three-branch nonlinear path is implemented with a 30 W class-AB PA and tested using a two-carrier wideband code division multiple access (WCDMA) signal with 15 MHz tone spacing at 2.14 GHz. From the measured results at an average output power of 33 dBm, the proposed MBAPD shows the adjacent channel leakage ratios (ACLRs) at plusmn15 MHz offset of -60.4 dBc and -60.2 dBc, which are an improvement of over 25 dB and 12 dB, compared to the PAs without APD and with conventional APD, respectively.