Chaoyi Huang

A Post-Matching Doherty Power Amplifier Employing Low-Order Impedance Inverters for Broadband Applications

This paper presents a modified Doherty configuration with extended bandwidth. The narrow band feature of the conventional Doherty amplifier is discussed in the view of the broadband matching. To extend the bandwidth, the post-matching architecture is employed in the proposed design. Meanwhile, broadband low-order impedance inverters are adopted to replace the quarter-wavelength transmission lines. Low-pass filter topologies are used to realize both the post matching network and the impedance inverters. A modified Doherty Power amplifier was designed and fabricated based on commercial GaN HEMT devices to validate the broadband characteristics of this configuration. The 6-dB backoff efficiencies of 47%-57% are obtained from 1.7 to 2.6 GHz (41.9% fractional bandwidth) and the measured maximum output power ranges from 44.9 to 46.3 dBm in the designed band. In particular, more than 40% efficiencies are measured at 10-dB backoff throughout the operation band.

Design of Broadband Linear and Efficient Power Amplifier for Long-Term Evolution Applications

In this letter, a broadband linear and efficient power amplifier for base-stations in long-term evolution (LTE) applications is designed, fabricated, and experimentally verified, employing Crees CGH40010F GaN HEMT. A novel method of baseband, fundamental and harmonic impedances control is used to provide high linearity and efficiency across a broad bandwidth. When producing a two-tone carrier-to-intermodulation ratio (C/I) of 30 dBc, the circuit has demonstrated a two-tone power added efficiency (PAE) between 45%-60% across the frequency range from 1.6 to 2.6 GHz while delivering 36.0-38.5 dBm average output power. For a single-carrier 20 MHz LTE signal with a peak-to-average ratio (PAR) of 6.5 dB, a measured high PAE of 40%-55% can be achieved at an average output power of 35.3-37.5 dBm with an adjacent channel leakage ratio (ACLR) of about -30 dBc from 1.6 to 2.6 GHz.

Design of a Post-Matching Asymmetric Doherty Power Amplifier for Broadband Applications

In this letter, the design of a broadband asymmetric Doherty power amplifier (ADPA) with an 800 MHz (41% fractional) bandwidth is presented. The post-matching structure and low-order impedance transformation networks (ITN) are employed to achieve the broadband performance. Meanwhile, different drain biases on the main and peaking devices are used to run the asymmetric operation. The proposed ADPA shows high-efficiency performance at 8-9 dB output power back-off (OBO) throughout the whole 800 MHz band. The ADPA has been designed and implemented using commercial GaN HEMTs to validate the OBO and broadband characteristics. Maximum output power ranges from 43.7 to 45.2 dBm, 50.4%-56.2% efficiencies at 8-9 dB OBO are measured from 1.55 to 2.35 GHz.

A Novel Design of Concurrent Dual-Band High Efficiency Power Amplifiers With Harmonic Control Circuits

A methodology for designing concurrent dual-band high efficiency power amplifiers (PAs) is presented in this letter. Load-pull simulations based on active device model are performed in two different bands to find the optimal required impedance conditions. A novel matching network with up to third order harmonic control is proposed to realize the high-efficiency mode matching in the two designed bands. A 1.9/2.6 GHz GaN PA is then designed to verify this method. The realized dual-band PA delivers above 10 W output power with more than 74% drain efficiency in the both operation bands.

Tri-band matching technique based on characteristic impedance transformers for concurrent tri-band power amplifiers design

This paper introduces a novel matching network synthesis method that matches arbitrary impedance at three independed frequencies to 50 Ohm. By converting impedance matching to admittance matching, the matching work can be divided into two steps. Modified T-type topology for triple band admittance matching is discussed based on ABCD-parameters, and the formulas of matching networks are analytically derived. Finally, the proposed synthesis approach is validated with the design and simulation of a tri-band matching network at 900, 1900 and 2400 MHz.

A Semianalytical Matching Approach for Power Amplifier With Extended Chebyshev Function and Real Frequency Technique

In this paper, an extended Chebyshev function is proposed to adapt the matching condition of the power amplifier (PA) by introducing a new factor. A set of impedance functions can be directly calculated along with the variation of a new variable, and the first element extracted from the functions is distributed in a wide range. In addition, the impedance function whose first element is the closest to the output capacitance of the transistor can be easily read out and selected as the original matching network. The fundamental impedance of the selected function will be reached a good matching state, and the impedances out of band will be on the edge of Smith chart. To achieve better performances, the real frequency technique is applied to adjust the harmonic impedances preventing it from falling into the low-efficiency region. Two PAs with a relative bandwidth of 34% and 75% are implemented to validate the proposed approach.

A 80W high gain and broadband Doherty power amplifier for 4/5G wireless communication systems

This paper presents a 80W high gain and broadband Doherty power amplifier (DPA) with symmetrical devices, employing Wolfspeeds CGHV27030S GaN HEMT. A novel architecture is used to eliminate the complex interaction of varying second harmonic impedances caused by active load modulation and provide high efficiency at output back-off (OBO) region and saturation point. Under a 10% duty cycle pulse excitation from 3.35-3.50 GHz, experimental results show the proposed DPA delivers 49.1-49.5 dBm output power with a drain efficiency (DE) of 50.2%-55.1% at 8 dB OBO and achieves a gain of 14.6-14.9 dB at an output power of 41 dBm. When extend the bandwidth to 3.3-3.6 GHz, the DPA can attain a measured DE higher than 40.9% at an OBO of 8 dB with a saturated power of 48.5-49.5 dBm. For a 2-carrier 40-MHz long-term evolution (LTE) signal with a peak-to-average power ratio (PAPR) of 8 dB, the adjacent channel leakage ratio (ACLR) is -30 dBc at 41 dBm average output power at 3.45 GHz.

Design of Broadband Modified Class-J Doherty Power Amplifier With Specific Second Harmonic Terminations

This paper presents a symmetrical Doherty power amplifier (DPA) based on class-J mode for efficiency enhancement in a broad bandwidth. With a second harmonic suppression integrated into the output matching network of carrier power amplifier (PA) and peaking PA, respectively, the complex interaction of varying second harmonic impedances caused by dynamic load modulation can be eliminated and the second harmonic impedance remains the same reactance at both the output back-off (OBO) region and the saturated power. To meet the requirement of second harmonic termination, the DPA works in conventional class-J mode at the saturated power and a modified class-J continuum is proposed to expand the impedance design space at 8 dB OBO with good efficiency performance. A gallium nitride DPA is designed and fabricated to validate the method over a frequency band of 3.3–3.75 GHz. Under a 10%-duty-cycle pulse excitation, experimental results show the DPA delivers 48-48.8 dBm output power with a drain efficiency (DE) of 58%–71%. At 8 dB OBO, a measured DE of 44%–55% is achieved with a gain of 11.8–13.5 dB. When driven by a 2-carrier 40-MHz long-term evolution signal with a peak-to-average power ratio of 8 dB, the DPA exhibits an adjacent channel leakage ratio of −30 dBc at an average output power of 40.7 dBm at 3.45 GHz.

Novel design of highly-efficient concurrent dual-band GaN Doherty power amplifier using direct-matching impedance transformers

A novel methodology for designing concurrent dual-band Doherty power amplifier (DPA) is presented in this paper. The required impedance conditions of the carrier amplifier to achieve high-efficiency performance at back-off region are discussed from a new perspective. A novel combine network with direct-matching impedance transformers is then presented to support the load modulation conditions for concurrent dual-band operations. A 1.8-2.6 GHz dual-band Doherty amplifier employing commercial GaN devices is then designed and implemented to validate the proposed method. The fabricated power amplifier (PA) achieves 72% and 60% efficiency for saturation operation at 1.8 and 2.6 GHz, respectively. For the 6 dB back-off region, the measured efficiencies are 63% and 51% in the two designed bands.

A two-stage 0.9–2 GHz GaN power amplifier using commensurate transmission line

An semi-analytic method is proposed to reduce the complexity of two-stage matching network (MN). It is also improved by adding a variable in the power supply branch for cutting down the size of MN. The first stage operates in a deep class AB mode, which would contribute to reshape the voltage form at gate of the second stage. In this way, the two-stage power amplifier without isolator could also achieve a good gain and efficiency performance. The experimental results show that the large signal gain is 31.3-35.5 dB with output power of 39.2-41.9 dBm in the band of 0.9-2 GHz and corresponding drain efficiency is 37.4-62%. And linearity performance is also evaluated via stimulus of 5 MHz WCDMA and 20 MHz LTE signals.