Drive Power Levels Research Articles

Non-Linear Frequency Noise Modulation in a Resonant MEMS Accelerometer

Resonant MEMS accelerometers offer the potential for very high resolution and wide bandwidth measurements over a large input dynamic range. The read-out is implemented by constructing an oscillator with the resonator as the primary frequency determining element. The noise of this oscillator front-end typically determines the resolution of the device, and the noise floor is set by the modulation of operative noise processes by the system dynamics. The resonator element is typically operated in the linear regime to prevent the detrimental impact of resonator non-linearities on noise conversion limiting frequency stability. However, by operating at higher drive power levels it is possible to also increase the signal-to-noise ratio for sufficiently large input frequencies. This paper shows that improved device performance over a wide bandwidth is possible by employing appropriate amplitude and phase feedback schemes to optimally bias the resonator thus enabling both short-term and long-term measurements with an electrically tunable resolution.

Nonlinear excitation of a rotational mode in a piezoelectrically excited square-extensional mode resonator

We present an experimental study of the nonlinear behavior of a square-extensional (SE) mode microelectromechanical resonator, actuated with a piezoelectric AlN thin film. The acoustic vibration fields of the device are characterized using laser probing. A nonlinear vibration behavior of the SE mode is observed above a drive power level of −10 dBm such that the vibration amplitude of the SE mode saturates and a rotational in-plane vibration mode is excited at a significantly lower frequency (0.725 MHz) than the SE mode (16.670 MHz). Interestingly, the measured ∼10 nm saturation amplitude of the SE mode is more than a decade below the amplitude value at which mechanical or electromechanical nonlinearities are estimated to become significant.

An High Performance Ka-band MMIC Fourth Harmonic Image Rejection Diode Mixer

An high performance Ka-band MMIC fourth harmonic image rejection diode mixer is designed using commercial United Monolithic Semiconductors (UMS) process in this paper. Details of design approach and outcome of simulations are presented. The results show that this mixer has a conversion loss less than 15.2 dB and image rejection ratio (IRR) more than 20 dB in the 34–38 GHz with a wide band IF range up to 3 GHz, for a local oscillating (LO) drive power level of 13 dBm.

Analysis and Simulation of the Effects of Distributed Nonlinearities in Microwave Superconducting Devices

This paper presents a comprehensive study of microwave nonlinearities in superconductors, with an emphasis on intermodulation distortion and third-harmonic generation. It contains the analysis of various resonant and nonresonant test devices and its validation using numerical simulations based on harmonic balance (HB). The HB simulations made on test devices show that the closed-form equations for intermodulation and third-harmonic generation are only valid at low power levels. The paper also contains examples of application of HB to illustrate that this technique is useful to simulate superconductive devices other than simple test devices, and that the validity of the simulations is not restricted to low drive power levels. Most of the analyses and simulations of this paper are based on electrical parameters that describe the nonlinearities in the superconducting material. These parameters are compatible with many existing models of microwave nonlinearities in superconductors. We discuss the particulars on how to relate these electrical parameters with one of the existing models that postulates that the nonlinear effects are due to a dependence of the penetration depth on the current density in the superconductor.

Degradation in lead zirconate titanate piezoelectric ceramics by high power resonant driving

Lead zirconate titanate (PZT) piezoelectric ceramics were driven in a resonant mode at various power levels. The stability of the PZT piezoelectric ceramics is found to depend greatly on the driving power level. At low driving power, the ceramics are very stable and the properties remain unchanged after continuous vibration for long periods of time. When the driving power is relatively high, however, an obvious temperature rise is observed in the ceramics during vibration and serious degradation occurs to the properties of the ceramics after some periods of continuous vibration. As the properties of the degraded ceramics are restored after an ageing process, it is proposed that high power resonant driving causes a de-ageing effect on PZT piezoelectric ceramics, which leads to degradation. The heat generated in PZT ceramics by driving with relatively high power is proved to play a vital role in the de-ageing effect.

0-1 GHz waveguide 10.6 mu m GaAs electrooptic modulator

A GaAs electrooptic modulator for use in 10.6- mu m laser frequency shifting applications is described. High-beam-quality output signals with a frequency tunability of 0.1-1.0 GHz were demonstrated. Thick epitaxial GaAs-AlGaAs waveguide structures were successfully fabricated into single-mode channel waveguides with excellent optical and electrooptic properties. A lumped-element modulator, with electrical and electrooptic characteristics in good agreement with theory, was operated at RF drive power levels up to the reverse breakdown voltage limit. The insertion loss of the modulator was quite high, due to absorption losses in the epitaxial material.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Operation and theory of a driven single-mode electron cyclotron maser.

A study is made of the operation of the electron cyclotron resonance maser (ECRM), when subjected to an external rf signal. The signal is introduced both via direct injection through a coupling hole in the oscillator and by modulating the electron beam in separate cavities, upstream of the oscillator. Experiments using both one and two ``prebunching'' cavities are reported. It is experimentally found that the gyromonotron, a specific embodiment of the ECRM, can be phase locked by premodulating the electron beam at drive power levels more than two orders of magnitude below that predicted by Adler's widely applicable theory for single-cavity oscillators. A perturbation theory is used to predict the phase-locking frequency band for a gyromonotron with any number of prebunching cavities. The predictions of this theory agree with the experimental results for two- and three-cavity phase locking. An investigation is made into the general amplitude and frequency response of the ECRM to an applied external signal. Experimentally, three distinct regions of qualitatively different ECRM behavior are noted: soft excitation, which is free, self-excited oscillation; hard excitation, where the oscillation requires an external impulse for startup; and amplifier, in which the output power level and frequency are linearly related to the drive in the small-signal regime.

A Device Characterization and Circuit Design Procedure for Realizing High-Power Millimeter-Wave IMPATT-Diode Amplifiers

A measurement and characterization technique is presented which allows design and realization of IMPATT amplifiers operating at maximum generation efficiency. Diodes mounted in a stable reduced-height waveguide circuit are characterized by their complex reciprocal scattering coefficient as a function of frequency, dc bias, and RF drive power level. In particular, terminal conditions which correspond to a maximum power exchange between the active one-port network and the source are identified and then used to design and realize controlled-gain maximum generation-efficiency amplifiers. Simple equalization networks are shown to provide a wide range of available amplifier gains between limits set by stability requirements. As an example, the technique is effectively used with silicon diodes at K/sub a/-band (33-40 GHz) to realize a 7-dB gain 250-mW power amplifier with 5-GHz bandwidth.

Efficient octave-bandwidth microwave light modulators

The use of wide-bandwidth interdigital microwave circuits to provide electrooptic modulation of light is discussed. Two models employing lithium niobate crystals of different aspect ratios have been constructed and tested. Both have nominal bandwidth from 1.0 to 2.0 GHz but actually give somewhat greater modulation bandwidth. Single-pass modulation tests made using 6328-Å light at RF drive power level of 5 watts show that 30 percent modulation depth over a 1.5-GHz frequency band is obtained for one model while approximately 50 percent modulation depth over a 1.1-GHz band is obtained for the other. These results show excellent agreement with analytical predictions. Measurement techniques are also discussed.

Frequency-pulling process in frequency-selective circuit

Frequency displacement of a reflex klystron oscillator, purposely placed in a frequency-selective circuit in a frequency-pulling process, is not monotonically proportional to the driving-power level. Final frequency separation between the oscillator and the driver, which precedes abrupt phase locking, exceeds initial separation.