Abstract: Multi-resonant control of a 3 degree-of-freedom (heave-pitch-surge) wave energy converter enables energy capture that can be in the order of three times the energy capture of a heave-only wave energy converter. The invention uses a time domain feedback control strategy that is optimal based on the criteria of complex conjugate control. The multi-resonant control can also be used to shift the harvested energy from one of the coupled modes to another, enabling the elimination of one of the actuators otherwise required in a 3 degree-of-freedom wave energy converter. This feedback control strategy does not require wave prediction; it only requires the measurement of the buoy position and velocity.

Abstract: A generator and method for tuning the generator are disclosed. The method includes setting the frequency of power applied by the generator to a current best frequency and sensing a characteristic of the power applied by the generator. A current best error based upon the characteristic of the power is determined, and the frequency of the power at the current best frequency is maintained for a main-time-period. The frequency of the power is then changed to a probe frequency and maintained at the probe frequency for a probe-time-period, which is less than the main-time-period. The current best frequency is set to the probe frequency if the error at the probe frequency is less than the error at the current best frequency.

Abstract: A passive electro-mechanical device that reduces phase noise in oscillators, thereby improving their frequency precision. The noise reduction device can consist of a pair of coupled nonlinear resonators that are driven parametrically—by modulating their natural frequency in time, through the output signal of a conventional oscillator at a frequency close to the sum of the linear mode frequencies. Above the threshold for parametric response, the coupled resonators can exhibit oscillation at an inherent frequency. The novel possibility for noise elimination is realized by tuning the system to operating points for which this periodic signal is immune to frequency noise in the drive signal, providing a way to clean the phase noise of the driving oscillator.

Abstract: A controller unit includes a PI-controller for harmonic command variables. The transfer function of the PI-controller has a conjugate complex pole at a controller angular frequency ?r in the s-plane or a pole at e±j?rT in the z-plane, wherein T is the sampling time of a discrete input signal of the PI-controller and ?r is larger than 0. The controller angular frequency ?r is chosen equal to the resonance angular frequency ?0 of an oscillator. The controller parameters, are, for example determined by pole/zero compensation. The controller unit allows, for example, a broad band control of harmonic oscillators in rotation rate sensors.

Abstract: MEMS oscillators, which include a silicon-type, in particular piezoresistive resonators, can be used to provide a fixed, stable output frequency. Silicon has a natural temperature dependence of Young's modulus, therefore, as ambient temperature changes and/or the piezoresistive resonator is powered, the resonator temperature changes, and the resonance frequency of the resonator drifts. In order to account for the temperature drift of the piezoresistive resonator, the piezoresistive resonator itself is used as a temperature sensor. The relative resistance change of the piezoresistive resonator depends only on the relative temperature change and material property of the resonator. Therefore, an accurate temperature can be sensed directly on the piezoresistive resonator. The temperature drift information is provided to a frequency adjuster, which corrects the output frequency of the circuit.

Abstract: A servo system is provided for controlling movement of a flexible structure having multiple masses and elements. Each element couples a respective two of the masses and functions as a spring when the flexible structure is subject to a linear or rotational input at or above a frequency at which the respective element exhibits flexure. The servo system includes multiple sensors, where each sensor is disposed relative to a respective one of the masses to sense a respective acceleration. A motor having a torque input may operatively be configured to output one of a linear or rotational force on the first mass based on a torque signal present on the torque input. A servo controller that receives each sensed acceleration from each sensor may generate a compensation feedback signal based on a sum of sensed accelerations. The torque signal may be output to the motor based on the compensation feedback signal.

Abstract: Systems and methods for operating with oscillators configured to produce an oscillating signal having an arbitrary frequency are described. The frequency of the oscillating signal may be shifted to remove its arbitrary nature by application of multiple tuning signals or values to the oscillator. Alternatively, the arbitrary frequency may be accommodated by adjusting operation one or more components of a circuit receiving the oscillating signal.

Abstract: In one embodiment, the present invention includes a method of correcting the frequency of a crystal oscillator. The method includes establishing an operating baseline for the crystal oscillator using a frequency reference, storing information in memory, and adjusting the frequency according to the information. The information corresponds to the operating baseline. Adjusting the frequency occurs in response to a power-on event and the absence of the frequency reference.

Abstract: There is provided an atomic force microscope (AFM) with increase the speed and sensitivity of detection of the resonant frequency shift in a cantilever. An AFM (1) extracts a reference signal and a phase shift signal from a detection signal from a displacement sensor of the cantilever. The reference signal is restrained from a phase change in accordance with the resonant frequency shift. The phase shift signal has a phase shifted in accordance with the resonant frequency shift. The AFM (1) determines the phase difference of the phase shift signal from the reference signal, as the resonant frequency shift. The AFM (1) may detect the phase difference between a plus-minus inversion point on the reference signal and a corresponding plus-minus inversion point on the phase shift signal. The AFM (1) may adjust phase before phase detection. The phase adjustment may move the detection point for the resonant frequency shift defined on the oscillation waveforms to the plus-minus inversion point.

Abstract: A method and apparatus for tuning the operational frequency of an electrical generator coupled to a time-varying load is described. One illustrative embodiment rapidly calculates an error (reflection coefficient magnitude) at the current operational frequency of the electrical generator; adjusts the frequency of the electrical generator by an initial step size so; rapidly calculates a second error; and if the magnitude of the second error is smaller than the magnitude of the first error, then the step size is increased and the frequency is adjusted by the increased step size.

Abstract: An apparatus for generating an oscillating signal including a negative-resistance circuit, a crystal, and a component to modify a series resonance of the crystal to decrease power consumption of the negative-resistance circuit in generating the oscillating signal. The component may include a positive-reactance circuit, one or more inductive elements, or pair of inductive elements coupled to the crystal. The apparatus may further include a frequency-tuning component for adjusting a frequency of the oscillating signal, such as a variable capacitor coupled to the crystal. The negative-resistance circuit may include a digital inverter circuit, an inverting analog amplifier, or a self-regulating circuit.

Abstract: A frequency synthesizer and a method of synthesizing an output signal. In one embodiment, the frequency synthesizer includes: (1) a substrate, (2) a resonator located on the substrate and comprising a micro electromechanical system device and a feedback amplifier coupled thereto, (3) a phase-locked loop located on the substrate and coupled to the resonator, (4) control logic located on the substrate and configured to control the phase-locked loop based on a known resonant frequency of the micro electromechanical system device and (5) a voltage-controlled oscillator located on the substrate and coupled to the phase-locked loop.

Abstract: An electronic component has at least a first diode and a second diode that are capacitance diodes. The characteristic curve of the second diode has a fixed, known relationship to that of the first diode. For example, the first diode and the second diode can have an identical variation ratio, being the quotient of the maximum and minimum adjustable capacitances. These components are suitable for use in television tuners, for example in three-band tuners, where diodes having the same characteristic curve and coming from different components are arranged and connected in each sub-receiving unit. The integration of a plurality of diodes reduces the number of components required, and also the time and cost involved in grouping together diodes with good synchronization properties.

Abstract: A control system for a tuning fork gyroscope uses motor frequency to control motor amplitude. The tuning fork gyroscope has a drive signal input and an output signal from which motor frequency is determined. A phase/frequency detector generates an error signal by comparing the actual oscillation phase of the output signal with the phase of a reference signal from a crystal controlled frequency synthesizer. The error signal is filtered in a feedback loop control to reduce phase detector ripple. The output of the loop controller is then used to determine the appropriate drive signal to drive the error signal to a constant and maintain a predetermined oscillation frequency.

Abstract: An improvement to a phase controlled mechanical oscillator consists of a balancing network which generates a feedback signal from two different input signals with adjustable weights. One of these input signals is directly derived from the oscillator signal, the other is derived from a phase tracking loop. Using the balancing network, adjustments can be made to adapt the feedback to the mechanical properties, in particular to the Q factor, of the oscillator. In a preferred embodiment, all major components are working at an intermediate frequency level, generated by mixing the oscillator frequency with a reference frequency. As a major advantage of this (heterodyne) mixing, the bandwidth of any applied frequency detector can be narrowed, thus increasing the achievable signal-to-noise ratio.

Abstract: Micromachined, thermally insensitive silicon resonators are provided having accuracy equivalent or superior to that of quartz resonators, and are fabricated from a micromechanical, silicon-on-glass process. In one embodiment, such a resonator is realized using a tuning fork gyroscope. Radiation-hard precision voltage references (PVRs) are enabled using the silicon resonators. Thermal sensitivity is reduced relative to that of a silicon-on-silicon process oscillator, providing a thermal sensitivity comparable to that of a quartz oscillator. By employing a micromechanical device based upon a tuning fork gyroscope, resonators are made from either or both of the gyro drive and sense axes. A resonator constructed as an oscillator loop whose resonant frequency is compared to a frequency standard provides a bias voltage as a reference voltage.

Abstract: An arrangement in tuning resonance modules includes a cavity and resonance body, which is steered to resonance position by a motor, which is driven by a voltage as long as there is a phase difference between the input signal to the resonance module and the output signal (called the measuring signal) from the module. The input signal is of high frequency, and it is desired now to transpose the signals down to low frequency for preventing interference with the measuring signal. The arrangement therefore includes a high-frequency oscillator controlled by a voltage and having a frequency range within which lies the frequency of the incoming signal. From the oscillator output signal and the input signal there is formed in a mixing means the difference between the signals, and in a second mixing means there is formed the difference between the oscillator output signal and the measuring signal such as to form hereby two low-frequency signals. These are compared in a phase detector with respect to phase position.

Abstract: A processor-controlled drive motor system for tuning a cavity klystron monitors the output (amplitude-vs-frequency) of the klystron and compares that monitored performance output with an intended amplitude-vs-frequency profile. Differences between the two characteristics are employed by the processor to generate a set of tuning cavity control signals through which respective stepping motors for displacing each cavity tuning slug are driven. The processor iteratively adjusts the cavity tuner control signals in accordance with a prescribed kylstron tuning program until the monitored amplitude response is within a prescribed tolerance of a preestablished characteristic stored in memory.