Class 324/328 - Of the beat frequency type

Subclass of Class 324 - Electricity: measuring and testing
Definition: Subject matter having means for mixing the search head signal
No. of patents: 21
Last issue date: 10/28/2008

Number	Title	Issue Date
7443359	Locating technique and apparatus using an approximated dipole signal Location determination is performed using a transmitter including an elongated generally planar loop antenna defining an elongation axis. The elongation axis is positioned along at least a portion of a path. A magnetic field is then generated which approximates a di...	10/28/2008
7397366	Method and apparatus for locating a person who has been buried alive A search apparatus and related method facilitate the final stage of a search for a buried person carrying a transmitter. When the searcher is in the close vicinity of the buried transmitter, the search enters a point-localization phase where the apparatus displays a...	07/08/2008
7356421	Precise location of buried metallic pipes and cables in the presence of signal distortion A new approach for locating an underground line described herein remains accurate in the face of bleedover by including both amplitude and phase from at least two magnetic field strength sensors in the measurement set. A numerical optimization step is introduced to ...	04/08/2008
7304480	Radio mode selectivity block for a detector for detecting a buried current carrying conductor A radio mode selectivity block 41 for a detector 1 for detecting a buried current carrying conductor comprises a plurality of beat frequency oscillators 53 to center the bandwidth of detection of the detector 1 on target very low frequenc...	12/04/2007
7285957	Method and apparatus to generate a circular polarized RF field independent of subject asymmetry An RF coil assembly is presented that incorporates balun networks to eliminate standing waves from cables used to apply a voltage to multiple drive ports of the coil. Each drive port is driven by an applied voltage that is shifted 90 degrees in the tangential direct...	10/23/2007
7088104	MRI tunable antenna and system A strip array antenna including a number of conductors (14) that are connected to ground or virtual ground though at least one reactive component (150). The apparent electrical length of conductors (140) is tuned so that it equals an integer mul...	08/08/2006
7062414	Method and apparatus for digital detection of electromagnetic signal strength and signal direction in metallic pipes and cables A new digital architecture for metallic pipe and cable locators, providing accurate estimation of the fundamental locate parameters, electromagnetic signal strength and signal direction, and utilizing a nested Digital Phase-Locked Loop (DPLL) structure is disclosed....	06/13/2006
7061236	Metal detector A metal detector has a circular excitation coil (10) through which foodstuffs to be tested (65) pass, on a conveyor belt (40). The excitation coil (10) is excited by a stable oscillator (50) and the lines of flux generated by the e...	06/13/2006
7031839	Multi-frequency focusing for MWD resistivity tools An induction logging tool is used on a MWD bottom hole assembly. Due to the finite, nonzero, conductivity of the mandrel, conventional multi frequency focusing (MFF) does not work. A correction is made to the induction logging data to give measurements simulating a ...	04/18/2006
6980003	Open half volume quadrature transverse electromagnetic coil for high field magnetic resonance imaging A half-volume quadrature TEM coil high field (>3 T) imaging applications. This novel coil produces a sufficiently large homogeneous B1 field region for the use as a volume coil. It provides superior transmission efficiency, resulting in significantly lowe...	12/27/2005
6772134	Control means for a horizontal boring tool Control apparatus for a horizontal boring tool is described which drives a boring lance via boring rods. The tool includes an input interface for receiving actual values of controlled variables of the horizontal boring tool, and an output unit for issuing control si...	08/03/2004
5994897	Frequency optimizing metal detector A metal detector (10) which uses a metallic test sphere (5) to pass with the product through the detector head (2) at periodic intervals. The frequency generator (21) which generates the signal sent to the oscillator coil (11) is capable of operating on n...	11/30/1999
5696490	FM (VHF) infrared wireless digital metal detector A FM (VHF) infrared wireless digital metal detector is disclosed having a sealed aluminum radiation shield and dielectric case, with a infrared phototransistor detector and krypton bulb arranged to relay detection data to meter within a clustered instrume...	12/09/1997
5247257	Electronic metal detector return signal phase changer A device is disclosed for use with heterodyne metal detectors to eliminate the indication of the detected presence of certain specific metals to the operator. A specially tuned circuit rotated adjacent the detector interacts with the circuitry of the dete...	09/21/1993
4975646	Detector system for recognizing a magnetic material An assembly formed by an electronic circuit in which a microprocessor is included that emits a signal from which additional signals are generated by a frequency synthesizer. These signals are applied to coils which form the emitting antenna, after being f...	12/04/1990
4641094	Magnetometer circuit for measuring the period of beat frequency maxima A conventional magnetometer produces an output signal (10) which comprises a series of pulses (12, 14, 16). Each of these pulses has a beat frequency maximum. These pulses are input to a comparator (50) which makes a comparison to a threshold voltage V	02/03/1987
4536719	Inductive pressure sensor using two oscillators An inductive pressure sensor is proposed which has at least one coil embodying a frequency-determining part of an oscillator and disposed at a distance from a diaphragm which is deflectable in accordance with pressure. When pressure is exerted on the diap...	08/20/1985
4459561	Phase-lock loop controlled object detector oscillator A vehicle detector installation includes a loop oscillator the loop of which is laid in the roadway and which is locked in operation to a voltage controlled oscillator (VCO). Vehicle detection is effected by a phase detector monitoring the phase differenc...	07/10/1984
4321539	Digital BFO metal detecting device with improved sensitivity at near-zero beat frequencies An improved metal detecting device of the beat frequency oscillator type is provided which incorporates a method for determining the side of the zero beat frequency at which a search oscillator is operating. The device includes a search coil conveniently ...	03/23/1982
4255710	Plural search frequency directional metal detector apparatus having enhanced sensitivity A directional concealed object locator, say metal detector, employing a beat frequency oscillator and at least two search oscillators. The search oscillators each include a loop antenna which in part serves to determine the search frequency signal rate of...	03/10/1981
4196391	Metal locator with stereotonic indication of translateral position A metal locator apparatus the preferred practice of which includes two electromagnetic field radiating inducers, which serve to act upon a metal object deposited in a covert medium from distinctly separate positions, including two separate search oscillat...	04/01/1980

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Class 324/328 - Of the beat frequency type