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"Power amplifiers"
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Broadband and Efficient Envelope Amplifier for Envelope Elimination and Restoration/Envelope Tracking Higher-Efficiency Power Amplifiers
Increasing the efficiency of transmitters, as the largest consumers of energy, is relevant for any wireless communication devices. For higher efficiency, a number of methods are used, including envelope tracking and envelope elimination and restoration. Increasing the bandwidth of used frequencies requires expanding envelope modulators bandwidth up to 250–500 MHz or more. The possibility of using amplifiers with input signal quantization (AISQ), as an alternative to the most common hybrid envelope tracking modulators, is considered. An approach has been developed for optimizing AISQ characteristics according to the criterion of minimum loss when amplifying modern telecommunication signals with Rayleigh envelope distribution. The optimal quantization levels are determined and the energy characteristics of AISQ are calculated. AISQ loss power is shown to decrease by 1.66 times with two-level quantization, by 2.4 times with three-level quantization, and by a factor of 3.0–3.7 for four–five quantization levels compared to a class B amplifier. With these parameters, AISQ becomes competitive with respect to hybrid envelope tracking modulators but does not have electromagnetic interference from the pulse width modulation (PWM) path.
Journal Article
A Compact 55–66 GHz Single‐Chip FMCW Transceiver Featuring 12‐dBm Psat and >11‐GHz Tuning Range in 65‐nm SOI CMOS
This paper presents a fully‐integrated frequency‐modulated continuous‐wave (FMCW) transceiver chip operating from 55–66 GHz, fabricated in a 65 nm silicon‐on‐insulator (SOI) CMOS process. The chip incorporates a wide‐tuning‐range voltage‐controlled oscillator (VCO) with four digitally selectable states, a driver amplifier, a power amplifier (PA), a low‐noise amplifier and passive mixers, providing a compact solution for high‐resolution millimetre‐wave radar and short‐range communication systems. An innovative hybrid digital‐analogue VCO tuning architecture, combined with co‐optimized transmit/receive front‐end design, enables robust noise and linearity performance within a small core area. Measurement results demonstrate a transmitter saturated output power of 12 dBm and an output return loss better than 8 dB across the band. The receiver achieves 10 dB of gain, a 9.8 dB noise figure and an input 1 dB compression point of −18 dBm. The integrated VCO exhibits a phase noise better than −87.71 dBc/Hz at 1 MHz offset.This paper presents a fully‐integrated FMCW transceiver chip operating from 55–66 GHz, fabricated in a 65 nm SOI CMOS process. The chip incorporates a wide‐tuning‐range VCO with four digitally selectable states, a driver amplifier, a PA, a low‐noise amplifier and passive mixers, providing a compact solution for high‐resolution millimetre‐wave radar and short‐range communication systems. An innovative hybrid digital‐analogue VCO tuning architecture, combined with co‐optimized transmit/receive front‐end design, enables robust noise and linearity performance within a small core area. Measurement results demonstrate a transmitter saturated output power of 12 dBm and an output return loss better than 8 dB across the band. The receiver achieves 10 dB of gain, a 9.8 dB noise figure and an input 1 dB compression point of −18 dBm. The integrated VCO exhibits a phase noise better than −87.71 dBc/Hz at 1 MHz offset.
Journal Article
X‐band quasi class‐F HPA MMIC using DynaFET GaN HEMT modelling
This paper proposes an X‐band quasi Class‐F high power amplifier (HPA) monolithic microwave integrated circuit (MMIC) using DynaFET gallium nitride (GaN) high electron mobility transistor (HEMT) modelling. To enhance efficiency, a novel quasi Class‐F output matching circuit is proposed. DynaFET modelling for GaN HEMT is utilized for accurate HPA MMIC design. The proposed quasi Class‐F HPA MMIC, fabricated using ETRI's 0.15 µm GaN process, achieves an output power of 43.5∼44.5 dBm with a power‐added efficiency of 36∼40.7% within the 9.1∼10.3 GHz frequency bandwidth. This paper introduces a novel X‐band quasi Class‐F high power amplifier (HPA) monolithic microwave integrated circuit (MMIC) using DynaFET gallium nitride (GaN) high electron mobility transistor (HEMT) modelling. A novel quasi Class‐F output matching circuit is proposed to improve efficiency, with DynaFET modelling for GaN HEMT employed for HPA MMIC design. The proposed quasi Class‐F HPA MMIC, fabricated using ETRI's 0.15 µm GaN process, achieves an output power of 43.5∼44.5 dBm with a power‐added efficiency of 36∼40.7% within the 9.1∼10.3 GHz frequency bandwidth.
Journal Article
A Low-Computational-Complexity Digital Predistortion Model for Wideband Power Amplifier
This paper proposes a Composition Piecewise Memory Polynomial (CPMP) digital predistortion model based on a Vector Switched (VS) behavioral model to address the challenges of severe nonlinearity and strong memory effects in wideband power amplifiers (PAs). To tackle this issue, two thresholds are calculated and used to segment the envelope values of the input signal according to the nonlinear distortion characteristics of the PA. In this approach, a Generalized Memory Polynomial (GMP) model is employed for the lower segment, a Memory Polynomial (MP) model is employed for the middle segment, and a higher-order GMP model is employed for the upper segment. By sharing the fundamental MP among the proposed segmented models and leveraging a design methodology that configures different cross terms, memory depths, and polynomial orders for each segment, this model achieves superior linearization performance while simultaneously reducing the computational complexity associated with model extraction. The experimental results demonstrate that the adjacent channel power ratio (ACPR) of the predistorted PA output signal using the proposed model improves from −36 dBc to −54 dBc, matching the performance of the GMP model. Furthermore, this performance is 0.5 dBc better than the Piecewise Dynamic Deviation Reduction (PDDR) and Decomposed Vector Rotation (DVR) models. Notably, the complexity of the proposed parameter extraction process is 28.8% of the DVR model, 21.79% of the GMP model, and 12.83% of the PDDR model.
Journal Article
Automatic Optimization of Input Split and Bias Voltage in Digitally Controlled Dual-Input Doherty RF PAs
Digitally controlled Dual-Input Doherty Power Amplifiers (DIDPAs) are becoming increasingly popular due to the flexible input signal splitting between the main and auxiliary stages. Nevertheless, the presence of many degrees of freedom, e.g., input amplitude split and phase displacement as well as biasing for multiple stages, often involves inefficient trial-and-error procedures to reach a suitable PA performance. This article presents automated parameter setting based on coordinate descent or Bayesian optimizations, demonstrating an improvement in the performance in terms of RF output power and power-added efficiency (PAE) in the presence of broadband-modulated signals, yet maintaining suitable linear behavior for, e.g., communications applications.
Journal Article
High-power mid-infrared femtosecond master oscillator power amplifier Er:ZBLAN fiber laser system
High-power femtosecond mid-infrared (MIR) lasers are of vast importance to both fundamental research and applications. We report a high-power femtosecond master oscillator power amplifier laser system consisting of a single-mode Er:ZBLAN fiber mode-locked oscillator and pre-amplifier followed by a large-mode-area Er:ZBLAN fiber main amplifier. The main amplifier is actively cooled and bidirectionally pumped at 976 nm, generating a slope efficiency of 26.9%. Pulses of 8.12 W, 148 fs at 2.8 μm with a repetition rate of 69.65 MHz are achieved. To the best of our knowledge, this is the highest average power ever achieved from a femtosecond MIR laser source. Such a compact ultrafast laser system is promising for a wide range of applications, such as medical surgery and material processing.
Journal Article
2W HBT Power Amplifier Module with Dual Second Harmonic Suppression Technique
This paper presents a high-power heterojunction bipolar transistor (HBT) power amplifier (PA) module designed for GSM/EDGE applications. The proposed HBT PA employs a differential output stage that delivers high output power at a low supply voltage. A transformer-based output matching network is employed to combine the differential output signals. Through the selection of an appropriate capacitor value at the transformer’s center tap, linearity is enhanced across a wide bandwidth without requiring additional second harmonic termination. When assembled with a low-pass filter and an antenna switch, the PA module achieves an output power of 36 dBm and a power-added efficiency (PAE) exceeding 40% in GSM mode. In EDGE mode, it delivers an output power of 28.5 dBm with a PAE exceeding 20%. Additionally, the designed PA module achieves an adjacent channel power ratio of −60 dBc at a 400 kHz offset with an output power of 28.5 dBm.
Journal Article
Theoretical Comparison of Different Envelope Elimination and Restoration Transmitter PWM Modulator Configurations to Expand the Possible Antenna Mismatch
The main characteristics of high-efficiency switching-mode solid-state power amplifiers with envelope elimination and restoration (EER) methods depend on all their elements. In this article, we study the influence of the types and parameters of the envelope path low-pass filters (LPFs) on the EER transmitter out-of-band emissions. This article presents for the first time an analysis of EER transmitter operation where the output impedance of the PWM modulator is not equal to zero, as usual (with a one-sided loaded LPF), but is matched with the low-pass filter and the load (with a double-sided loaded LPF). Theoretical comparisons of EER transmitters’ out-of-band emissions were carried out with four envelope path LPF configurations (one-sided and double-sided loaded LPFs with a smooth and sharp transition, respectively), for both the nominal load (broadband antenna) and resonant antennas with a limited bandwidth. The analysis showed that for the case of transmitter operation on a resonant antenna with a limited bandwidth, the preferable option was the use of a sixth-order double-sided loaded LPF with a smooth transition. The use of the proposed modulator configuration allowed the transmitter to operate on an antenna with VSWR = 1.07 at the edges of the transmitted signal band with a minimum LPF bandwidth equal to 5.8 bands of the amplified signal. This could significantly expand its application capabilities and allow one to reduce the PWM clock frequency and increase efficiency.
Journal Article
Design of Broadband Doherty Power Amplifier Based on Misaligned Current Phase
A broadband Doherty power amplifier (DPA) always experiences an efficiency degradation between two efficiency peaks, especially at two side bands. In this study, the efficiency degradation was demonstrated to be caused caused by the in-phase power combining at the saturation power level. To solve this problem, current misalignment was introduced into the broadband DPA design. The carrier and peaking PA have different current phases when performing the power combination at the saturation power level. In this work, it was also demonstrated that the efficiency in the high-power region of a DPA can be improved by elaborately using misaligned current phases. A detailed analysis and the design procedure of a broadband DPA are presented in this paper. And a 1.5–2.45 GHz broadband DPA was implemented and measured. The fabricated DPA achieves a saturation output power of 42.7–44.9 dBm, a saturation drain efficiency (DE) of 62.7–74.1% and a gain of 10.2–13.9 dB over 1.5–2.45 GHz. Moreover, the fabricated DPA also achieves a 6 dB back-off DE of more than 49.1% in the frequency band of interest.
Journal Article