Lower bound on the eigenvalues of the characteristic equation for an arbitrary multilayered gyromagnetic structure with perpendicular magnetization (original) (raw)
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Phase noise in cryogenic microwave HEMT and MESFET oscillators
IEEE Transactions on Microwave Theory and Techniques, 1993
This paper addresses the influence of cooling on the phase noise of HEMT and MESFET oscillators. The initial measurements of the device dc characteristics and low frequency noise (0.1 kHz-100 kHz) under cooling give indications on the suitability of a given device for use in low phase noise cooled oscillators. Cooled pseudomorphic AlGaAs/GaInAs/GaAs HEMT's (PHEMT's) turn out to be particularly well-suited as they are free of collapse and They are free of g-r noise in the frequency range of interest. We report on 4 GHz oscillators operated at 110 K and featuring a phase noise below-100 dBc/Hz at 10 kHz from the carrier in spite of a very modest loaded Q (160). It is suggested that high temperature superconductor resonators could greatly enhance the spectral purity of PHEMT's oscillators.
Microwave noise characterization of GaAs MESFET's: determination of extrinsic noise parameters
IEEE Transactions on Microwave Theory and Techniques, 1988
The noise equivalent circuit model for a GaAs MESFET proposed previously [I] is supplemented with a model for device parasitics, in order to calculate the noise parameters of a mounted GaAs MESFET. The calculated parameters are in good agreement with measured noise parameters from 2 to 18 GHz. The model is thus established as a valid representation of the noise properties of the device. The utility of the model lies in the fact that, compared with the measured and tabulated noise parameters, its elements are easier to obtain, and it serves as a simpler, more compact description of the noise characteristics of the MESFET.
Low-frequency noise in AlGaAs/InGaAs/GaAs Hall micromagnetometers
Noise and Information in Nanoelectronics, Sensors, and Standards, 2003
We report on studies aimed at understanding and improving the intrinsic noise of high-performance sensors using a 2D electron gas channel confined by a quantum well in the pseudomorphic AlGaAs/InGaAs/GaAs heterostructure. MIS gated and ungated Hall sensors shaped as a Greek cross with dimensions ranging from 100 µm down to submicrometer range have been investigated. At room temperature the predominant low frequency Hall voltage noise originates from the ensemble of trapping/detrapping events occurring within the continuum of GaAs surface states. Its power spectral density can be deduced from independent measurements of the interface trap density-of-states by applying Shockley-Read-Hall dynamics and the Fluctuation-Dissipation Theorem. In fact, theoretical spectra calculated without any adjustable fitting parameter coincide closely with the experimentally measured ones. At cryogenic temperature this interface traps noise freezes out, thus revealing a much weaker intrinsic background noise with 1/f spectrum. For small sensors the intrinsic 1/f noise converts into one or a few lorentzians due to the action of individual random telegraph signals (RTS). For Hall crosses with an intersection of 4×4µm 2 , we find statistically less than 1 fluctuator per each decade of time constant at 77 K. Due to the random distribution of the elementary fluctuators, some of these small Hall crosses may show less low-frequency noise than much larger 60×60µm 2 sensors.
Noise temperature ofn+nn+GaAs structures
Physical Review B, 1996
The noise temperature of GaAs n ϩ nn ϩ two-terminal structures of micrometer and submicrometer lengths is theoretically analyzed as a function of frequency and applied voltage. Calculations are performed at a kinetic level, and are based on a mixed Monte Carlo hydrodynamic scheme. Different operation modes of the structure are considered, namely, when operating as a nonlinear resistor ͑passive device͒ as well as when operating as a Gunn amplifier or generator ͑active device͒. Under generating conditions the noise temperature at low frequency is found to go to infinity for voltages above the threshold value for the Gunn effect, as expected in bulk material. Under amplifying conditions the noise temperature at low frequency is found to remain finite even at applied voltages well above the threshold value for the Gunn effect. At high frequencies the noise-temperature spectrum shows structures associated with transit-time effects, carrier energy, and plasma-time effects. In particular, we calculate the noise figure of merit covering both amplifying and passive conditions. Very good agreement is found between theory and available experiments. ͓S0163-1829͑96͒01634-7͔
Amplitude and Phase Noise of Magnons
arXiv: Applied Physics, 2019
The low-frequency amplitude and phase noise spectra of magnetization waves, i.e. magnons, was measured in the yttrium iron garnet (YIG) waveguides. This type of noise, which originates from the fluctuations of the physical properties of the YIG crystals, has to be taken into account in the design of YIG-based RF generators and magnonic devices for data processing, sensing and imaging applications. It was found that the amplitude noise level of magnons depends strongly on the power level, increasing sharply at the on-set of nonlinear dissipation. The noise spectra of both the amplitude and phase noise have the Lorentzian shape with the characteristic frequencies below 100 Hz.
Low-frequency noise in GaAs MESFETs related to backgating effects
IEE Proceedings G Circuits, Devices and Systems, 1991
The influence of the backgating effect on low-frequency noise in GaAs MESFETs grown by molecular beam epitaxy is investigated. The low-frequency noise is of the llf type superimposed on generation-recombination noise. We show that the backgating effect, although it reduces the current, increases current fluctuations and, hence, noise. Furthermore, it is shown that the incorporation of a low-temperature grown GaAs buffer, by MBE, significantly reduces the sensitivity of the noise level of the device to backgate bias.
A new general procedure to extract the noise parameters of microwave gaAs mesfets
European Transactions on Telecommunications, 1991
In this paper a generalized procedure to extract the noise parameters of GaAs MES-FETs is presented. The average quadratic error between the measured values of optimum noise figure and the calculated ones is minimized in ofder to obtain the optimum admittance value at the amplifier input. The hypothesis of device unilaterality is assumed. A comparison between the proposed method and the previous ones has been carried out. A consequent more simplified analytical approach to evaluate the optimum noise source impedance of a GaAs MESFET amplifier allows the proposed procedure to be easly implemented in the most popular CAD tools.
Origin of microwave noise from an n-channel metal–oxide–semiconductor field effect transistor
Journal of Applied Physics, 2002
The physics of noise is a complex subject. It is often difficult to clearly identify the physical origin of the observed noise. Electronic noise at microwave frequencies is technologically very important and has been extensively studied. While it is well known that many physical phenomena give rise to output current fluctuations ͑i.e., noise͒ in a metal-oxide-semiconductor field effect transistor ͑MOSFET͒, few physical phenomena have a time constant that can contribute in the microwave range. Current physical models of MOSFET microwave noise are all based on thermal agitation of electrons ͑thermal noise͒. However, what is the correct temperature ͑lattice or electron͒ to use in the noise calculation is an ongoing debate in the literature. All the modeling efforts have been using noise measured from pristine devices as a test for validity. In this work, we studied the n-MOSFET microwave noise as a function of electrical stress induced degradation. Our experiments thus introduced a new dimension in the noise behavior study. The results of our experiments cannot be explained by any of the current existing models. All existing models discounted flicker noise as being too small at microwave frequency. Our experimental results compel us to reexamine the validity of this common assumption. While we are not quite able to prove conclusively, our evidences are clearly leaning toward defect-induced fluctuation ͑flicker noise͒ as the origin of microwave noise in a n-MOSFET
2021
Recent progress in MEMS resonant-fin-transistors (RFT) allows very high-Q active mode resonators, promising crystal-less monolithic clock generation for mmWave systems. However, there is a strong need for design of mmWave oscillators that utilize the high-Q of active-mode RFT (AM-RFT) optimally, while handling unique challenges such as resonator’s low electromechanical transduction. In this brief, we develop a theory and through design and post-layout simulations in 14-nm Global Foundry process, we show the first active oscillator with AM-RFT at 30 GHz, which improves the fundamental limits of phase noise and figure-of-merit as compared to the oscillators with conventional LC resonators. For AM-RFT with Q-factor of 10K, post layout simulation results show that the proposed oscillator exhibits phase noise <-140 dBc/Hz and figure-of-merit >228 dBc/Hz at 1 MHz offset for 30 GHz center frequency, which are >25 dB better than the existing monolithic LC oscillators. Keywords—Osci...