Broadband Power Research Articles

A 4.5–8.5 GHz GaAs power amplifier with high in-band flatness

This paper presents a 4.5–8.5 GHz three-stage power amplifier(PA) fabricated in a 0.5 μm GaAs process. The PA adopts gain compensation technology with gain flatness and power transmission in the broadband. Furthermore, the size of the pHEMT is optimized to strike a balance among linearity, power-added efficiency (PAE) and the area. The measurement results show that the proposed PA has a gain flatness of 22.6 ± 0.8 dB with good input and output VSWR, the output saturation power is of 25 dBm and the corresponding power added efficiency is greater than 32% over the whole operating frequency band. This proposed PA has better broadband gain flatness and power characteristics compared to the conventional cascaded PA. The chip size of the PA is 2.475 mm × 0.9 mm, including all DC and RF pads.

Dispersion study of a broadband terahertz focusing reflecting metasurface for 6G wireless communication

In 6G wireless communications, functional terahertz reflecting metasurfaces are expected to play increasingly important roles such as beamforming and beamsteering. However, their performance optimization as a function of multiple competing design parameters remains a significant challenge. This paper demonstrates a multi-dimensionally optimized design of a functional and efficient focusing metasurface reflector in the burgeoning D-band (0.11-0.17 THz). In addition to achieving 20% fractional bandwidth (0.135-0.165 THz), this design is polarization-maintaining, diffraction limited, simple in design, and exhibits 64.1% broadband power efficiency (1.9 dB insertion loss). We perform a unique study of the magnitude of temporal (group-delay) dispersion introduced by this design to the broadband signal at the focus. Despite being formed by an array of highly dispersive resonators, the metasurface exhibits very low dispersion, which avoids pulse reshaping and its consequent limitations on achievable data rate. The low dispersion characteristic of the metasurface is a consequence of its optimized design. The design and performance of the focusing reflector are presented followed by a dispersion analysis revealing that only 2.83% temporal broadening of the pulse is observed at the focus.

Attention mechanism based bidirectional LSTM model for broadband power amplifier linearization

AbstractIn this letter, a novel digital predistortion (DPD) model for broadband power amplifier (PA) linearization is proposed, namely Attention Mechanism based Bidirectional Long Short‐term Memory Network (AM‐BiLSTM) model. In order to verify the linearization performance of the AM‐BiLSTM model in digital predistortion process, a 100 MHz bandwidth 5G new radio (5G NR) signal is employed to test a sub‐6G PA operating at 2.6‐GHz. The experimental results show that the adjacent channel power ratio (ACPR) of the PA with AM‐BiLSTM model can be improved by 24 dB which is 6 dB and 3 dB better than the generalized memory polynomial (GMP) model and the Chebyshev polynomials LSTM (CP‐LSTM) model in ref [1], repspectively. Therefore, the proposed AM‐BiLSTM model is very effective for the DPD linearization of broadband PAs.

A Ku-Band Broadband Stacked FET Power Amplifier Using 0.15 μm GaAs pHEMT.

To meet the application requirements of broadband radar systems for broadband power amplifiers, a Ku-band broadband power amplifier (PA) microwave monolithic integrated circuit (MMIC) based on a 0.15 µm gallium arsenide (GaAs) high-electron-mobility transistor (HEMT) technology is proposed in this paper. In this design, the advantages of the stacked FET structure in the broadband PA design are illustrated by theoretical derivation. The proposed PA uses a two-stage amplifier structure and a two-way power synthesis structure to achieve high-power gain and high-power design, respectively. The fabricated power amplifier was tested under continuous wave conditions, and the test results showed a peak power of 30.8 dBm at 16 GHz. At 15 to 17.5 GHz, the output power was above 30 dBm with a PAE of more than 32%. The fractional bandwidth of the 3 dB output power was 30%. The chip area was 3.3 × 1.2 mm2 and included input and output test pads.

Broadband PA design using Bayesian algorithms with different covariance functions

AbstractThis article examines the effects of Bayesian optimization (BO) with different covariance functions on the optimization of a radio frequency power amplifier (RFPA). An initial PA is designed based on a Chebyshev low‐pass topology using a 10 W Gallium Nitride (GaN) transistor. The objective function is established in a novel manner. The performance of the initially designed PA was optimized by using various BO algorithms, including two different acquisition functions and five different covariance functions. Both simulation and measurement results indicate that the kernel squared exponential (KSE) and Matérn32 covariance functions provide the best option for optimizing PA by BO. A broadband power amplifier (PA) operating at a frequency range from 2.5 GHz to 3.5 GHz has been developed with an output power (Pout) greater than 40.8 dBm and a power‐added efficiency (PAE) greater than 65%.

High-efficiency broadband power amplifier with split-ring resonator second harmonic output matching network

AbstractIn this paper, a realization method for high-efficiency broadband power amplifier (PA) based on split-ring resonator (SRR) second harmonic output matching network (SHOMN) is presented. The SRR is composed of double rectangular rings, and it can flexibly match the second harmonic components to the high-efficiency impedance region in the Smith chart in a wide frequency band. Besides, the impedance transformation characteristic of SRR is derived, and the optimal output impedance is converted from the transistor drain to the output of SHOMN for accurate fundamental matching. For validation, a PA operating in 1.2–3.0 GHz is designed and fabricated for a 10-W GaN transistor. The measurement results show that the maximum efficiency can reach 78.3%; meanwhile, the average saturated output power is 41.0 dBm.

Systems-level analysis of local field potentials reveals differential effects of lysergic acid diethylamide and ketamine on neuronal activity and functional connectivity.

Psychedelic substances have in recent years attracted considerable interest as potential treatments for several psychiatric conditions, including depression, anxiety, and addiction. Imaging studies in humans point to a number of possible mechanisms underlying the acute effects of psychedelics, including changes in neuronal firing rates and excitability as well as alterations in functional connectivity between various brain nodes. In addition, animal studies using invasive recordings, have suggested synchronous high-frequency oscillations involving several brain regions as another key feature of the psychedelic brain state. To better understand how the imaging data might be related to high-resolution electrophysiological measurements, we have here analyzed the aperiodic part of the local field potential (LFP) in rodents treated with a classic psychedelic (LSD) or a dissociative anesthetic (ketamine). In addition, functional connectivity, as quantified by mutual information measures in the LFP time series, has been assessed with in and between different structures. Our data suggest that the altered brain states of LSD and ketamine are caused by different underlying mechanisms, where LFP power shifts indicate increased neuronal activity but reduced connectivity following ketamine, while LSD also leads to reduced connectivity but without an accompanying change in LFP broadband power.

Cryogenic sensor enabling broad-band and traceable power measurements

Recently, great progress has been made in the field of ultrasensitive microwave detectors, reaching even the threshold for utilization in circuit quantum electrodynamics. However, cryogenic sensors lack the compatibility with broad-band metrologically traceable power absorption measurements at ultralow powers, which restricts their range of applications. Here, we demonstrate such measurements using an ultralow-noise nanobolometer, which we extend by an additional direct-current (dc) heater input. The tracing of the absorbed power relies on comparing the response of the bolometer between radio frequency and dc-heating powers traced to the Josephson voltage and quantum Hall resistance. To illustrate this technique, we demonstrate two different methods of dc-substitution to calibrate the power that is delivered to the base temperature stage of a dilution refrigerator using our in situ power sensor. As an example, we demonstrate the ability to accurately measure the attenuation of a coaxial input line between the frequencies of 50MHz and 7GHz with an uncertainty down to 0.1 dB at a typical input power of -114 dBm.

Long Pulse and High Duty Operation of a W-Band Gyrotron Traveling Wave Tube

In this letter, we reported a gyrotron traveling wave tube (gyro-TWT) featured broadband and high power at the University Electronic Science and Technology of China (UESTC), which had achieved a long pulse width up to 2 ms and a maximum duty cycle of up to 40%. Two typical operation states, i.e. high voltage/current (60.5 kV/9.0 A) and low voltage/current (46 kV/2.6~2.9 A), are respectively hot tested for high pulse and average power. With a duty cycle of 40%, the measured maximum average power is up to 20.1 kW.

Spin-Momentum Locking and Ultrafast Spin-Charge Conversion in Ultrathin Epitaxial Bi1 - x Sbx Topological Insulator.

The helicity of three-dimensional (3D) topological insulator surface states has drawn significant attention in spintronics owing to spin-momentum locking where the carriers' spin is oriented perpendicular to their momentum. This property can provide an efficient method to convert charge currents into spin currents, and vice-versa, through the Rashba-Edelstein effect. However, experimental signatures of these surface states to the spin-charge conversion are extremely difficult to disentangle from bulk state contributions. Here, spin- and angle-resolved photo-emission spectroscopy, and time-resolved THz emission spectroscopy are combined to categorically demonstrate that spin-charge conversion arises mainly from the surface state in Bi1 - x Sbx ultrathin films, down to few nanometers where confinement effects emerge. This large conversion efficiency is correlated, typically at the level of the bulk spin Hall effect from heavy metals, to the complex Fermi surface obtained from theoretical calculations of the inverse Rashba-Edelstein response. Both surface state robustness and sizeable conversion efficiency in epitaxial Bi1 - x Sbx thin films bring new perspectives for ultra-low power magnetic random-access memories and broadband THzgeneration.

Enhanced acoustic black hole energy harvesters with multipiezoelectric array designs

This study theoretically and numerically proposes vibroacoustic energy harvesting concepts based on acoustic black holes (ABHs) and piezoelectric materials. Various ABH configurations in planar structures have been explored and investigated from the perspective of flexural wave localization and energy confinement. Different piezoelectric energy transducers, attached to the center region of ABHs with loading circuits are designed. Energy harvester with arrayed two ABHs shows higher energy production density than a harvester with single ABH under the same driving conditions. The energy harvester with the combination of the arrayed ABHs and the multipiezoelectric arrays shows high output electrical power density and broadband features.

Design and Analysis of Broadband Power Delivery Network Noise Absorber for Parallel-Plate Mode Suppression

In this article, a broadband power delivery network (PDN) noise absorber with its 90%-absorption band from 4 to 7.5 GHz is proposed to suppress parallel-plate modes. Due to the ever-increasing switching speed of integrated circuits (ICs) nowadays, a few millimeters separating a chip and the conventional reflective filters may induce significant power noises and cause serious radio frequency interference (RFI) and electromagnetic interference (EMI) problems. In this scenario, PDN noise absorbers can prevent power noises from both reflecting and transmitting, thus avoiding cavity resonances, providing a clean and stable power supply, and achieving almost zero radiation. Four cases were compared to verify all these advantages of the PDN noise absorbers. For conducted noises around 6 GHz, the self-impedance peak is suppressed by 86.9% at the noise source end and the insertion loss is almost the same level at the transmitted end when compared with the case of two rings of the reflective filters. Furthermore, almost 100% of the radiative noises are cleared away by the proposed PDN noise absorbers.

Channel estimation for OFDM-based indoor broadband power line communication systems

State-of-the-art indoor broadband power line communications (PLC) systems use orthogonal frequency division multiplexing (OFDM) signals with constellations up to 10 bits/symbol, which makes channel estimation a key aspect. This paper focuses on the initial channel estimation used in the payload, which might be further adapted by means of a decision-directed strategy. This initial estimate has to be computed on a per-frame basis and can be accomplished from the preamble, the header symbol (assuming that it has been correctly decoded) or from a combination of both. This work proposes simple channel estimation techniques for this problem and derives their most appropriate parameters. They are compared with the linear minimum mean squared-error (LMMSE) estimator and others commonly used in wireless scenarios by considering both their performance and computational complexity. The factors limiting the performance of the estimators based on the preamble and the header symbols are analyzed and the implications of the differences between PLC and wireless channels, such as the absence of fading, in the design of estimation techniques that require knowledge of the channel statistics are discussed. A performance analysis of the considered techniques is accomplished in a set of 171 measured indoor PLC channels. Obtained results indicate that estimators from the header perform better than those based on the preamble symbols and we provide a computationally simple estimator that gives nearly optimum performance by combining estimates from both the preamble and the header symbols.

Design of a broadband power amplifier based on high‐efficiency impedance space

SummaryWe propose a broadband high‐efficiency power amplifier (PA) with output power between 42.6 and 44.7 dBm, drain efficiency (DE) over 62%, and power additional efficiency (PAE) over 52% in the 2.3–3.5GHz frequency band. This PA effectively combines the high‐efficiency characteristics of class‐F PAs with the advantages of controlling the second harmonic for obtaining high efficiency at large bandwidth. The Dual Band Harmonic Control and Matching Network (DBHCN) realizes the conversion from 50 Ω to high‐efficiency impedance space (HEIS) while controlling the high‐order harmonics in different frequency bands. The proposed PA can be used for the fifth‐generation mobile communication technology (5G) base stations and broadband radars.

Compact, broadband, and low-loss power splitters using MZI based on Bézier bends.

We experimentally demonstrate wavelength-independent couplers (WICs) based on an asymmetric Mach-Zehnder interferometer (MZI) on a monolithic silicon-photonics platform in a commercial, 300-mm, CMOS foundry. We compare the performance of splitters based on MZIs consisting of circular and 3rd order (cubic) Bézier bends. A semi-analytical model is constructed in order to accurately calculate each device's response based on their specific geometry. The model is successfully tested via 3D-FDTD simulations and experimental characterization. The obtained experimental results demonstrate uniform performance across different wafer sites for various target splitting ratios. We also confirm the superior performance of the Bézier bend-based structure, compared to the circular bend-based structure both in terms of insertion loss (0.14 dB), and performance consistency throughout different wafer dies. The maximum deviation of the optimal device's splitting ratio is 0.6%, over a wavelength span of 100 nm. Moreover, the devices have a compact footprint of 36.3 × 3.8 μ m 2.

Neural adaptation and fractional dynamics as a window to underlying neural excitability.

The relationship between macroscale electrophysiological recordings and the dynamics of underlying neural activity remains unclear. We have previously shown that low frequency EEG activity (<1 Hz) is decreased at the seizure onset zone (SOZ), while higher frequency activity (1-50 Hz) is increased. These changes result in power spectral densities (PSDs) with flattened slopes near the SOZ, which are assumed to be areas of increased excitability. We wanted to understand possible mechanisms underlying PSD changes in brain regions of increased excitability. We hypothesized that these observations are consistent with changes in adaptation within the neural circuit. We developed a theoretical framework and tested the effect of adaptation mechanisms, such as spike frequency adaptation and synaptic depression, on excitability and PSDs using filter-based neural mass models and conductance-based models. We compared the contribution of single timescale adaptation and multiple timescale adaptation. We found that adaptation with multiple timescales alters the PSDs. Multiple timescales of adaptation can approximate fractional dynamics, a form of calculus related to power laws, history dependence, and non-integer order derivatives. Coupled with input changes, these dynamics changed circuit responses in unexpected ways. Increased input without synaptic depression increases broadband power. However, increased input with synaptic depression may decrease power. The effects of adaptation were most pronounced for low frequency activity (< 1Hz). Increased input combined with a loss of adaptation yielded reduced low frequency activity and increased higher frequency activity, consistent with clinical EEG observations from SOZs. Spike frequency adaptation and synaptic depression, two forms of multiple timescale adaptation, affect low frequency EEG and the slope of PSDs. These neural mechanisms may underlie changes in EEG activity near the SOZ and relate to neural hyperexcitability. Neural adaptation may be evident in macroscale electrophysiological recordings and provide a window to understanding neural circuit excitability.

Low-loss, broadband MMI coupler based on thin film lithium niobate platform

A low-loss broadband power splitter based on X-cut lithium niobate is proposed by utilizing the multimode interference coupler with a shallow-etched slot, wedge-shaped structure and SiO2 cladding. The multimode waveguide with a shallow-etch slot could reduce the sensitivity of multi-mode region on the wavelength and reach to high-quality imaging requirements. Results show that there is an excess loss around 0.01 dB at the operation wavelength of 1550 nm, a broad operation bandwidth of ∼ 1314 nm and large tolerance in the shallow-etching. Additionally, our proposed device has been compared with the published and conventional multimode interference coupler for presenting good low-loss and broad bandwidth.

1 × 5 broadband photonic crystal power splitter designed by the Powell algorithm.

We propose a novel, to the best of our knowledge, 1×5 broadband power splitter based on the photonic crystal. The Powell algorithm is used to reverse-design the proposed broadband power splitter. The results show that the transmittance of each output port of the broadband photonic crystal power splitter can be adjusted by changing the radii and offsets of the dielectric rods at the junction area of each waveguide. According to the target splitting ratio, the reverse design of the structural parameters using the Powell algorithm significantly improves the optimization efficiency and splitting performance of the broadband power splitter. The designed power splitters have a wide working bandwidth of 1525-1565 nm, a flexible and designable power splitting ratio, excellent splitting performance, and a compact size, which have great application prospects in all-optical communication networks, high-density photon integration, and other fields.

A 211-to-263-GHz Dual-LC-Tank-Based Broadband Power Amplifier With 14.7-dBm P SAT and 16.4-dB Peak Gain in 130-nm SiGe BiCMOS

This article presents a broadband sub-terahertz (THz) power amplifier (PA) with a low-loss four-way power combiner. The proposed power combiner consists of an improved zero-degree combiner (ZDC) and a three-conductor Marchand balun simultaneously achieving broadband matching and power combining. The proposed three-conductor Marchand balun adopts a dual- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LC$ </tex-math></inline-formula> tank technique by merging two resonators, and it can be equivalent to a transformer-based multi-resonating network. The power distribution is realized by one input power splitter generating two pairs of differential signals and two parallel 1-to-2 active power splitters. This hybrid distribution driving network further enhances efficiency and power gain. Based on these improvements, a high-output-power sub-THz PA with superior efficiency has been fabricated in the 130-nm SiGe bipolar complementary metal oxide silicon field effect transistor (BiCMOS) technology. The three-stage PA achieves a peak power gain of 16.4 dB, 3-dB small-signal gain bandwidth of 52 GHz from 211 to 263 GHz, a measured maximum saturated output power of 14.7 dBm at 224 GHz, and a peak power-added efficiency (PAE) of 3.13% at 220 GHz. The folded input splitter and extremely compact power combining methodology lead to a core area of 770 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}\,\,\times \,\,280\,\,\mu \text{m}$ </tex-math></inline-formula> .

Design and Research of Channel Circuit Based on Broadband Power Line Carrier

In order to effectively improve the anti-attenuation, anti-noise and anti-impedance change capabilities of the low-voltage narrowband power line carrier communication unit, reduce the carrier signal coupling attenuation, and highly fidelity signal power encoded and modulated by the carrier chip, an improved high-speed power line carrier communication transceiver circuit is designed. Using 303.13kHz~357.81kHz as sub-carrier signal frequency can effectively avoid the random noise generated by high-power power electronic equipment and household appliances below 35kHz. At the same time, to prevent the frequency crosstalk of power line carrier products with 270kHz and 421kHz as the center frequency, the Y-coupling capacitor and sixth order Butterworth band-pass filter circuit are used to design the signal receiving and transmitting circuit of the communication unit to isolate unwanted signals. The experimental simulation of the designed circuit is carried out on the circuit simulation software Multisim 12. The results show that the designed power line carrier communication transceiver circuit can effectively control the signal coupling attenuation within 4dB, and the filtering of unwanted signals can also reach 41.7dB, which has good application value.