Northrop Corporation

Wilson Industries, Inc.

Apogee Acoustics, Inc.

Apogee Technology, Inc.

Leo Spiegel

Gary E Walker

Harper E Sharp

Richard M Masters

John R Howatt

Elmer J Frey

James L Kirtley, Jr

Michael S Danielson

David B Meyers

Anthony J Shuman

Mark B Nazar

Andrew A Adrian

An all digital switching amplifier wherein linearization of the power switch is accomplished solely by using three states. A small, fixed width, bi-state compensating carrier waveform is added to the leading or training edges of an oversampled main input pulse producing a compensated composite waveform. This compensating carrier linearizes output from a power switch by effecting common mode cancellation of switch time errors. Output pulse width combinations for the compensating carrier are obtained from a look-up table stored in memory. A correction mechanism is implemented to correct for harmonic distortion that is dependent on the modulation level or index and results from the compensating carrier modulation. The correction mechanism applies the inverse of the modulation induced distortion to the oversampled compensated composite input signal to null distortion products resulting from the modulation scheme used to apply the small carrier to linearize the performance of the tri-state power switch. Digital timing control of the power switch's deadband ensures accuracy of the timing and sequence in which individual switches within the power switch H-bridge are turned off and turned on, so as to preclude a short circuit across the power supply. A high speed clock used in linearizing the power switch provides a timing reference to generate the necessary deadband timing delays and pulse width increments. The output bridge uses enhancement mode MOSFETs.

Digital signal processing for linearization of small input signals to a

A loudspeaker system using ribbon transducer elements wherein the ribbon elements of the high and mid-range transducer units form a plurality of conductive circuits separated by spaces, or cuts, therebetween which have substantially smooth, undulating wave forms. The magnetic circuit return paths thereof are arranged so as to be remote from and out of the transmitting paths of the acoustic signals generated at such units and the surfaces of the magnetic circuit components and a baffle structure associated therewith are shaped to reduce diffraction effects in the acoustic signals therefrom. A woofer ribbon element has a plurality of interconnected conductive circuit regions to form a generally serpentine shaped circuit, which regions are separated by channels, or cuts, each of which has a smooth, undulating wave form.

Acoustical ribbon transducer loudspeaker system

The speaker system consists of a single housing containing a tweeter, mid-range and woofer transducer units. The tweeter unit consists of an elongated, aluminum ribbon positioned vertically and connected to the top and bottom of a rigid elongated frame. The ribbon is located between sets of split magnets which are designed to provide a shaped magnetic field that helps center the ribbon in a direction perpendicular to its length. Additional electromagnetic centering is provided by flat ribbon conductors located on the surfaces of the magnets sets which return the current carried by the ribbon. The mid-range transducer is similar to the tweeter transducer in construction except that the edges of the mid-range ribbon are mechanically attached to the frame by foam strips. In addition, the mid-range ribbon is transversely corrugated at variable slant angles relative to ribbon longitudinal axis. The woofer transducer consists of an elongated, trapezoidal, corrugated aluminum ribbon attached to a non-vibrating frame. In order to provide a single electrical path, the ribbon is divided into a serpentine path by a series of cuts. To prevent undesirable auto effects, the ribbon is tensioned in a transverse direction.

Ribbon speaker system

An inertial borehole survey system is disclosed. The survey system of the present invention includes a probe suitable for insertion into a borehole. The probe includes a plurality of temperature sensitive inertial measuring instruments which are utilized to survey the borehole during the descent or ascent of the probe. Accuracy of these instruments is maintained by enclosing the instruments in a thermal insulating package and by providing a mass of isothermal heat absorbing material which exhibits a phase change at a temperature well above most ambient temperatures. In a preferred embodiment of the present invention, a heat absorbing material is utilized which exhibits a phase change at a temperature of 116.degree. F. The probe also includes a longitudinal air passage which permits ambient temperature air to be utilized to cool the isothermal heat absorbing material by passing air through the length of the probe. Currently the instrument cluster is mounted on a member formed of a single billet of metal to form a thermally conductive, small diameter, stiff structure which permits the inertial measurement instruments to be spaced longitudinally in a cluster in order to minimize the diameter to approximately the largest diameter of any single instrument and yet which permits heat generated by the instruments to be absorbed by the heat absorbing material.

Inertial borehole survey system

A system and method for surveying, with accuracies better than one foot per thousand feet of depth, very deep boreholes having the attendant small diameters, high temperatures and high pressures with very high accuracy. A downhole probe is used having a small diameter, less than about four inches. Three linear type accelerometers and at least two gyros to provide three sensitive axes are fixedly mounted at points spaced along the axis of an elongated, rigid, thermally conductive support member to form an instrument cluster. Signals from these instruments are then processed and transmitted serially over a conductor of a conventional wireline to the surface unit where a surface computer continuously computes and records the current position of the instrument.

A displacement measuring transducer performs a direct conversion of changes in physical position, particularly angular position, into a digital form suitable for input to a digital microprocessor. The transducer is of the inductive type. Two inductance legs are connected at a common input to form a three-terminal bridge device. To sense positional changes, a step voltage is applied to the input and the transient response at the output of each leg is sampled periodically. Digital circuitry compares the responses of each leg to a fixed reference voltage and produces a binary digital count proportional to the motion sensed by the transducer. This transducer provides high resolution and low noise over a wide dynamic range. It also allows temperature compensation and scale factor calibration.

Digitized displacement transducer

A solenoid torquer system with flux rate feed-back. The system includes a torquer coil and an associated core, and a device adapted to drive a current through the coil having an amplitude proportional to the difference between a coil current command signal and the actual current in the coil. A flux rate servo loop includes a sensor coil coupled to the core to provide a signal representative of the flux rate in the core. This flux rate signal is compared with a flux rate command signal having a ternary width-modulated form. The resultant difference signal is used as the current command signal. The system network provides a precise flux level, or force.

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Sharon, MA, United States of America

Leo Spiegel