Microwave Amplifiers Research Articles

Self-assembled monolayer gate doping and their detail deep cryogenic characterization of GaN/Si HEMTs

Wide bandgap GaN/AlGaN/GaN/SOI high-electron-mobility transistors (GaN/Si HEMTs) have recently grabbed interest in the semiconductor field as outstanding contenders for microwave and radio-frequency (RF) power amplification systems with their powerful capacities. Though the negative threshold voltage (Vth) property of GaN limits the practical application as an electronic system for static power consumption consideration, the current study demonstrates a novel method that can adjust Vth higher and without damaging the crystal lattice of the GaN channel materials by self-assembly monolayer doping. Also, the fabricated GaN/AlGaN/GaN/SOI HEMT devices exhibit excellent efficiency with enhancement of mobility and subthreshold slope in cryogenic temperatures using Fluorine-contained monolayer doping. This could unlock additional process options for the development of next-generation GaN/AlGaN/GaN/SOI HEMT with high mobility, catering to the advancements in 6G communication and circuits for low-orbit satellites.

DESIGN AND SIMULATION OF S-BAND MICROWAVE AMPLIFIER FOR SATELLITE COMMUNICATIONS SYSTEM

This paper presents a novel design of S-band monolithic microwave integrated circuit (MMIC) amplifiers based on GaAs MESFET HFET-1102 transistors used in radiofrequency (RF) and microwave communications systems. Based on the Chebyshev gain response, an analytical method is used to design a two-stage lumped microwave amplifier. The matching networks constituted by lumped elements are transformed into T inductive networks, and the resulting amplifier is optimized using RF simulator software. In the following step, the lumped optimized amplifier is transformed into a distributed amplifier and implemented on Rogers TMM3 substrate largely used in microwave circuits. The final MMIC amplifier is stable in the frequency band (2-4 GHz), and excellent performances are obtained in terms of very high gain, reaching a peak of 35 dB, low input (S11) and output reflection (S22) coefficients, and very good output/input isolation (S12). For its RF characteristics, the proposed MMIC amplifier presented in this work is very suitable for space telecommunications in low earth orbit (LEO) satellites onboard receivers.

In-operando microwave scattering-parameter calibrated measurement of a Josephson traveling wave parametric amplifier

Superconducting traveling wave parametric amplifiers (TWPAs) are broadband near-quantum limited microwave amplifiers commonly used for qubit readout and a wide range of other applications in quantum technologies. The performance of these amplifiers depends on achieving impedance matching to minimize reflected signals. Here, we apply a microwave calibration technique to extract the S-parameters of a Josephson junction based TWPA in-operando. This enables reflections occurring at the TWPA and its extended network of components to be quantified, and we find that the in-operation performance can be well described by the off-state measured S-parameters.

Tunable microwave circulator and amplifier in cavity magnonic system

An adjustable unidirectional amplifier is proposed in a hybrid cavity magnonic system. By eliminating the rapidly dissipative auxiliary mode, we obtain the effective Hamiltonian for a typical three-body circulator. Through analyzing the transmission coefficients of the system, we find that the nonreciprocal transmission of photon–magnon as well as the amplification of arbitrary signals can be both realized without requiring in the parity-time symmetry condition. In addition, the amplification factor of our system is highly adjustable. Our theoretical scheme has potential implication in realizing magnonic triodes and magnon-based quantum information processing.

Radiatively cooled quantum microwave amplifiers

Superconducting microwave amplifiers are essential for sensitive signal readout in superconducting quantum processors. Typically based on Josephson junctions, these amplifiers require operation at milli-Kelvin temperatures to achieve quantum-limited performance. Here, we demonstrate a quantum microwave amplifier that employs radiative cooling to operate at elevated temperatures and maintain near quantum-limited added noise. This kinetic-inductance-based parametric amplifier, patterned from a single layer of relatively high-Tc NbN thin film, maintains a high gain and meanwhile enables low added noise of 1.3 quanta when operated at 1.5 K. Remarkably, this represents only a 0.2 quanta increase compared to the performance at a base temperature of 0.1 K. Based on our findings, we also discuss the practicality of such an operating scheme for various quantum applications. By uplifting the parametric amplifiers from the mixing chamber without compromising readout efficiency, this work represents an important step toward more scalable microwave quantum technologies.

Design of high gain MMIC amplifier for LEO satellite communication systems

In this paper, we present a novel design of S-band monolithic microwave integrated circuit (MMIC) amplifier based on GaAs Mesfet HFET-1102 transistor used in radiofrequency (RF) and microwave communications system. Basing on Chebyshev gain response an analytical method is used to design two stages lumped microwave amplifier. The matching networks constituted by lumped elements are transformed to T inductive networks and the resulting amplifier is optimized using RF simulator software. Thelumped optimized amplifier is then transformed to distributed amplifier and implemented on Rogers TMM3 substrate, largely used in microwave circuits. The proposed MMIC distributed amplifier is stable in the frequency band (2–4 GHz) and excellent performances are obtained in terms of very high gain reaching a peak of 34.23 dB, minimum input return loss (S11) of −8.85 dB at f=2.62 GHz, minimum output return loss (S22) of −12.21 dB at f=2.05 GHz and very good output/input isolation (S12) lower than −51.99 dB. For its excellent performances, the proposed MMIC distributed amplifier, is very suitable for use in space telecommunications as in Low Earth Orbit (LEO) satellites onboard receivers where the high gain amplifier is very important to assure the success of the space missions.

Design of a novel split-recessed-gate β-Ga2O3 MOSFET-based maximum-gain microwave amplifier

In this study, a split-recessed-gate Ga2O3 MOSFET has been proposed for high-frequency applications. Extensive simulations have been carried out using TCAD Silvaco to examine the analog characteristics as well as the critical high-frequency metrics of the proposed device. A comparison has been drawn with conventional recessed-gate β-Ga2O3 MOSFET, and it is demonstrated that the proposed device outperforms the conventional device in terms of the high-frequency metrics due to its significantly lower parasitic capacitances and higher intrinsic gain. In addition, it was also demonstrated that the proposed device exhibits a substantial increase of 127.7% in the Johnson’s figure of merit, significantly higher, i.e. 134.7% higher, than Baliga’s high-frequency figure of merit, as well as a 3.25% increase in Baliga’s figure of merit as compared to the conventional device. Furthermore, a two-port network analysis has been carried out for both the devices and it has been shown that the proposed device offers higher gain with a slight trade-off in the reflections at the input/output ports. The scattering parameters have also been extracted and used to perform the stability analysis. It was observed that the proposed device exhibits higher stability for the entire frequency range. Furthermore, a maximum gain amplifier was designed using the proposed device. An impressive gain of 11.04 dB was demonstrated at an ultra-high frequency of 3 GHz.

Nanostructured tungsten trioxide developed from environmentally friendly green process as a promising cathode for excellent field emission

Extensively explored as cathodes for field emission, nanostructured metal oxides play a crucial role in diverse applications such as microwave amplifiers, renewable energy systems, flat panel displays, and micro-electronics. The quest for high current density, low threshold field, and stable field emission persists. In present study, we introduce a green synthesis approach using vegetable oil as a reaction medium to produce hexagonal tungsten trioxide (h-WO3). The structural analysis confirmed the formation of h-WO3 with a nanorod-like morphology. The spin-coated h-WO3 film on a silicon substrate exhibited promising field emission properties, including a field enhancement factor (β) of 1596 and a turn-on field of 4.60 V/μm, comparable to reported values. This research opens avenues for the cost-effective and scalable utilization of h-WO3 as an electron emitter in advanced optical and electrical devices.

On Modeling of Nonlinear Dynamics of an Electron Beam in a Plasma Microwave Amplifier

On Modeling of Nonlinear Dynamics of an Electron Beam in a Plasma Microwave Amplifier

Monolithic Integration of a Microwave Amplifier and a Multisource Energy Harvesting Circuit

Monolithic Integration of a Microwave Amplifier and a Multisource Energy Harvesting Circuit

Low-noise cryogenic microwave amplifier characterization with a calibrated noise source.

Parametric amplifiers have become a workhorse in superconducting quantum computing; however, research and development of these devices has been hampered by inconsistent and, sometimes, misleading noise performance characterization methodologies. The concepts behind noise characterization are deceptively simple, and there are many places where one can make mistakes, either in measurement or in interpretation and analysis. In this article, we cover the basics of noise performance characterization and the special problems it presents in parametric amplifiers with limited power handling capability. We illustrate the issues with three specific examples: a high-electron mobility transistor amplifier, a Josephson traveling-wave parametric amplifier, and a Josephson parametric amplifier. We emphasize the use of a 50-Ω shot noise tunnel junction (SNTJ) as a broadband noise source, demonstrating its utility for cryogenic amplifier amplifications. These practical examples highlight the role of loss as well as the additional parametric amplifier "idler" input mode.

Heat-Assisted Magnetization Switching in Flexible Spin-Orbit Torque Devices.

Heat-assisted magnetic anisotropy engineering has been successfully used in selective magnetic writing and microwave amplification due to a large interfacial thermal resistance between the MgO barrier and the adjacent ferromagnetic layers. However, in spin-orbit torque devices, the writing current does not flow through the tunnel barrier, resulting in a negligible heating effect due to efficient heat dissipation. Here, we report a dramatically reduced switching current density of ∼2.59 MA/cm2 in flexible spin-orbit torque heterostructures, indicating a 98% decrease in writing energy consumption compared with that on a silicon substrate. The reduced driving current density is enabled by the dramatically decreased magnetic anisotropy due to Joule dissipation and the lower thermal conductivity of the flexible substrate. The large magnetic anisotropy could be fully recovered after the impulse, indicating retained high stability. These results pave the way for flexible spintronics with the otherwise incompatible advantages of low power consumption and high stability.

A current-controlled magnonic reservoir for physical reservoir computing

Physical reservoir computers based on principles of magnonics promise energy efficient data processing and a reduction in the size and weight of the neuromorphic computing devices. The present work is a major step toward all-magnonic implementation of the recently proposed concept of a physical reservoir based on the spin wave active ring. The main component of the ring is a spin wave delay line employing a thin film of yttrium iron garnet (YIG) as the spin wave guiding medium. We propose controlling spin wave propagation in the YIG film electronically to enter input data into the reservoir. To this end, we exploit a physical effect of scattering of backward volume spin waves from a highly localized Oersted field of a dc current flowing through a metallic strip sitting on top of the YIG film. We find experimentally that a very small current (on the order of several milliamps) through the strip is able to control the amplitude of auto-oscillations in the ring. The use of the current control of spin wave propagation as a means to enter input data into the reservoir reduces the number of non-magnetic components of the reservoir to just one (a microwave amplifier). In addition, the proposed current-controlled magnonic reservoir demonstrates a record-high short-term memory capacity of 5.53, as our experiments show. Our findings open up an avenue for reduction of energy consumption by magnonic active-ring-based physical reservoirs, their micro-miniaturization, and all-magnonic implementation.

SBS-Based Tunable Microwave Photonic Notch Filter and Amplifier Simultaneously With Enhanced Gain, Bandwidth, and Polarization Control up to 50 GHz

SBS-Based Tunable Microwave Photonic Notch Filter and Amplifier Simultaneously With Enhanced Gain, Bandwidth, and Polarization Control up to 50 GHz

Maser threshold characterization by resonator Q-factor tuning

Whereas the laser is nowadays an ubiquitous technology, applications for its microwave analog, the maser, remain highly specialized, despite the excellent low-noise microwave amplification properties. The widespread application of masers is typically limited by the need of cryogenic temperatures. The recent realization of a continuous-wave room-temperature maser, using NV− centers in diamond, is a first step towards establishing the maser as a potential platform for microwave research and development, yet its design is far from optimal. Here, we design and construct an optimized setup able to characterize the operating space of a maser using NV− centers. We focus on the interplay of two key parameters for emission of microwave photons: the quality factor of the microwave resonator and the degree of spin level-inversion. We characterize the performance of the maser as a function of these two parameters, identifying the parameter space of operation and highlighting the requirements for maximal continuous microwave emission.

Q-band EPR cryoprobe

Following the success of cryogenic EPR signal preamplification at X-band, we present a Q-band EPR cryoprobe compatible with a standard EPR resonator. The probehead is equipped with a cryogenic ultra low-noise microwave amplifier and its protection circuit that are placed close to the sample in the same cryostat. Our cryoprobe maintains the same sample access and tuning which is typical in Q-band EPR, as well as supports high-power pulsed experiments on typical samples. The performance of our setup is benchmarked against that of existing commercial and home-built Q-band spectrometers, using CW EPR and pulsed EPR/ENDOR experiments to reveal a significant sensitivity improvement which reduces the measurement time by a factor of about 40× at 6 K temperature at reduced power levels.

Realization of the unidirectional amplification in a cavity magnonic system

We experimentally demonstrate the nonreciprocal microwave amplification using a cavity magnonic system, consisting of a passive cavity (i.e., the split-ring resonator), an active feedback circuit integrated with an amplifier, and a ferromagnetic spin ensemble (i.e., a yttrium–iron–garnet sphere). Combining the amplification provided by the active circuit and the nonreciprocity supported by the cavity magnonics, we implement a nonreciprocal amplifier with the functions of both unidirectional amplification and reverse isolation. The microwave signal is amplified by 11.5 dB in the forward propagating direction and attenuated in the reverse direction by −34.7 dB, giving an isolation ratio of 46.2 dB. Such a unidirectional amplifier can be readily employed in quantum technologies, where the device can simultaneously amplify the weak signal output by the quantum system and isolate the sensitive quantum system from the backscattered external noise. Also, it is promising to explore more functions and applications using a cavity magnonic system with a real gain.

Методы и особенности измерения теплового сопротивления интегральных СВЧ-усилителей на гетеропереходных биполярных транзисторах

The method of measuring the thermal resistance (TR) of semiconductor devices (SD) according to OST 11 0944-96 and the original modulation method implemented in the hardware and software package developed by the authors are described. In both methods, the SD is heated by pulsed power, and the temperature of its active region (transition) is determined by a change in the temperature–sensitive parameter (TSP) - the voltage at the SD at a low current passed through the SD in the pauses between the pulses of the heating current. The measurement error of the vehicle by the standard method strongly depends on the choice of the duration of the heating current pulses and the delay time when measuring the voltage at the SD after switching off the heating current. In the modulation method, the duration of the heating current pulses is changed according to the harmonic law, and according to the results of measuring the voltage at the SD during the passage of the heating and measuring current, the modulus of the thermal impedance of the SD is determined as the ratio of the first harmonic of the transition temperature to the first harmonic of the heating power. According to the frequency dependence of the thermal impedance module, the components of the vehicle of the object are determined, while the requirements for maintaining the temperature of the device body are significantly reduced and, as a result, the measurement error of the vehicle is reduced. The results of comparative measurements of the TR of integrated microwave amplifiers (amplifying cascades) on InGaP/GaP HBT by the standard and modulation method at different values of the amplitude of the heating current are presented. It is shown that the results of measuring the TR of integrated microwave amplifiers by both methods are in good agreement with each other. It is established that with an increase in the amplitude of the heating current, the TR junction-case of integrated microwave amplifiers decreases, which is due to the alignment of current distribution in the structure of the GBT during heating.

Development of an SIS Mixer-Based Low-Noise Amplifier Amenable to Josephson Oscillator Pumping

We propose a low-noise and low-power-consumption microwave amplifier using superconductor-insulator-superconductor (SIS) mixers as quasi-particle frequency up- and down-converters pumped by a Josephson array oscillator in the millimeter-wave band. A proof-of-concept study of an amplifier with two W-band waveguide mixers using Nb/Al-AlOx/Nb junctions in a cascade connection demonstrated an average gain of 6 dB and a noise temperature of 12 K from nearly DC to 5 GHz. We also designed and fabricated a Josephson array oscillator at 100 GHz, which consisted of 31 overdamped Josephson junctions placed at each half-wavelength in an Nb microstrip line. The estimated output power of the oscillator was 0.2 μW at 100 GHz, which can be increased by increasing the number of the oscillator junctions. These results suggest that the proposed SIS mixer-based amplifier is suitable for on-chip integrated circuits to be implemented in large-scale multipixel SIS receivers and quantum computers.

Frequency-swept dynamic nuclear polarization

Dynamic nuclear polarization (DNP) improves the sensitivity of NMR spectroscopy by the transfer of electron polarization to nuclei via irradiation of electron-nuclear transitions with microwaves at the appropriate frequency. For fields > 5 T and using g ∼ 2 electrons as polarizing agents, this requires the availability of microwave sources operating at >140 GHz. Therefore, microwave sources for DNP have generally been continuous-wave (CW) gyrotrons, and more recently solid state, oscillators operating at a fixed frequency and power. This constraint has limited the DNP mechanisms which can be exploited, and stymied the development of new time domain mechanisms. We report here the incorporation of a microwave source enabling facile modulation of frequency, amplitude, and phase at 9 T (250 GHz microwave frequency), and we have used the source for magic-angle spinning (MAS) NMR experiments. The experiments include investigations of CW DNP mechanisms, the advantage of frequency-chirped irradiation, and a demonstration of an Overhauser enhancement of ∼25 with a recently reported water-soluble BDPA radical, highlighting the potential for affordable and compact microwave sources to achieve significant enhancement in aqueous samples, including biological macromolecules. With the development of suitable microwave amplifiers, it should permit exploration of multiple new avenues involving time domain experiments.