Abstract:
In a circuit for use with a micromachined device having a movable mass (18) that forms an inner electrode (34) of a differential capacitor (40), oppositely phased square waves (52, 54) are applied to two outer electrodes (36, 38) of the differential capacitor. A reset voltage is applied to the inner electrode synchronously with the square waves to stabilize and control the potential on the inner electrode. The signal on the inner electrode is demodulated by sampling during a first half of the square wave and a second half of the square wave between applications of the reset pulse (57) to obtain a voltage that does not contain noise due to the reset switch (64).
Abstract:
A micromachined device has first (32), second (34), and third (36) electrodes forming a differential capacitor (30), and first and second drivers (40, 42) for providing clocked signals (44, 46) to the first and second electrodes (32, 34). The drivers (40, 42) each have supply leads (50, 52, 54, 56) coupled to first and second reference voltage supplies via fixed first and second resistors (R1, R3, R4, R6), and also coupled together with variable resistors (R2, R5) for trimming an offset so that electrostatic forces are balanced.
Abstract:
A micromachined device is provided that establishes select dimensional relationships between micromachined structures to achieve correlation in dimensional variation among these structures. Such dimensional relationships are achieved through consistent spacing between desired operating structures and by adding new structures (i.e., dimensional control structures) which provide additional consistent spacing at desired locations within the micromachined device.
Abstract:
A micromachined device (48) is packaged to reduce stiction. In one embodiment, a level of moisture is introduced in the package (60) to create a very thin film over surfaces of the device (48). The device (48) can also be packaged with a vapor deposition of an organic material (108) after a wafer of devices has been separated into individual dies and the individual dies are placed in open containers (112). In another embodiment, a micromachined device is positioned in an open package (120) and a liquid (126) or solid organic material is disposed within the package so that when the device is sealed, the organic material vaporizes and coats portions of the die to reduce stiction.
Abstract:
A micromachined magnetometer is built from a rotatable micromachined structure (10) on which is deposited a ferromagnetic material (54) magnetized along an axis parallel to the substrate (12). A structure rotatable about the Z-axis can be used to detect external magnetic fields along the X-axis or the Y-axis, depending on the orientation of the magnetic moment of the ferromagnetic material. A structure rotatable about the X-axis or the Y-axis can be used to detect external magnetic fields along the Z-axis. By combining two or three of these structures, a dual-axis or three-axis magnetometer is obtained.
Abstract:
A digital filtering system (10) is fed by input signal and produces an output signal from either a relatively low bandwidth filter or a relatively wide bandwidth filter selectively in accordance with the time rate of change in the input signal. The output signal is produced by the relatively low bandwidth filter (26) when the input signal is slowly varying and the output signal is produced by the relatively wide bandwidth filter (28) when the input signal changes rapidly, after which the output is produced from the relatively low bandwidth filter when the input signal reverts to its more slowly varying characteristics.
Abstract:
A dynamic phase selector phase locked loop circuit (20) includes: an A/D converter (24) for receiving an input signal (22) to be sampled; a phase detection circuit (26) for determining the phase error between the input signal (22) and a clock signal; a clock circuit (30), responsive to the phase detection circuit (26), for providing the clock signal to the A/D converter for timing the sampling of the input signal (22); the clock circuit (30) including a delay circuit having a number of delay taps; and a phase selector circuit (42), responsive to the phase detection circuit (26) for initially gating (43) the clock signals to the A/D converter from the clock circuit (30), and enabling one of the delay taps to dynamically adjust the phase of the clock signal and reduce the initial phase error.
Abstract:
A charge transfer device which includes a reference charge generator that generates a reference charge signal in response to receiving a control signal, first and second charge signal channels arranged to receive portions of the reference charge signal, and a charge distributor which distributes the reference charge signal between the first and second charge signal channels in accordance with a ratio determined by a differential input signal. The reference charge generator includes a source diffusion and a pair of gates each having respective potential wells electrically coupled to one another. The pair of gates generate the reference charge signal by extracting a charge packet from the source diffusion in response to having the control signal applied thereto, the charge packet being divided between the wells. The potential wells each include high conductivity regions defined by selected diffusions. The charge distributor includes a pair of barrier gates which are driven with the differential input signal. In exemplary embodiments of the invention, the charge transfer device is configured as a charge domain sample-and-hold circuit, a discrete-time amplifier circuit, a comparator circuit for discrete-time inputs and a magnetic field sensor circuit.
Abstract:
A computed tomography imaging method that includes receiving an analog beam intensity signal from a computed tomography scanner and converting it into a series of digital representations at successive points in time. An indication that a portion of the scanner has reached a certain position relative to the beam is received asynchronously with respect to these points in time, and the value of at least one of the digital representations is adjusted in response to the indication to obtain a corrected digital representation of the analog signal. A computed tomography imaging method that includes sigma-delta modulating an analog beam intensity signal to obtain a modulated version of the signal, and decimating it according to a rectangular time domain response with rounded rising and falling ends, which can be axially symmetrical. The method can also include another step of decimating that lasts a different amount of time, and/or another step of decimating that overlaps the step of decimating. A method of analog-to-digital conversion that can be used in computed tomography imaging, including actively deriving a first voltage from an analog current signal, dividing the first voltage into a second voltage, and converting the second voltage into a digital output.
Abstract:
A switched-capacitor circuit that includes a first signal path disposed between a first input node and a first output node, and a second signal path disposed between a second input node and a second output node. The first and second switches can be alternately disposed within the first and second signal paths. An amplifier responsive to the switches can be provided, and its offset can be cancelled. The outputs of the amplifiers can be maintained, and this can involve buffering.