Electricity: measuring and testing – Of geophysical surface or subsurface in situ – With radiant energy or nonconductive-type transmitter
Patent
1988-12-29
1991-02-26
Hille, Rolf
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
With radiant energy or nonconductive-type transmitter
324344, 324345, 343703, 343867, 455278, 455298, H01Q 2300, G01V 308
Patent
active
049964844
ABSTRACT:
The present invention is used to cancel a narrow band noise of know frequency, such as 60 Hz noise generated by powerlines, in electromagnetic receiving equipment. A cancelling antenna is wrapped around the sensing antenna of the electromagnetic receiver equipment. The cancelling antenna is provided with an alternating current signal of the same frequency as the ambient powerline noise. The cancelling antenna produces an electromagnetic field that is 180 degrees out of phase and of equal amplitude to the ambient powerline noise, as measured by the sensing antenna. The alternating current is produced by a noise antenna, a phase-locked loop and an amplifier. The noise antenna receives the ambient powerline noise, the phase-locked loop locks onto and tracks the frequency of the noise, and the amplifier provides the necessary amplification.
REFERENCES:
patent: 3731752 (1973-05-01), Schad
patent: 4027264 (1977-05-01), Gutleber
patent: 4247821 (1981-01-01), Buselli
patent: 4314378 (1982-02-01), Fowler et al.
patent: 4475214 (1984-10-01), Gutleber
patent: 4542532 (1985-09-01), McQuilkin
patent: 4837514 (1989-06-01), Spies
patent: 4837522 (1989-06-01), Fleury et al.
Qian & Qian, "Automatic Power-Line Interference Canceller for Geophysical Instruments", Australian Soc. Explor. Geophys. Bull., vol. 16, Nos. 2-3, pp. 266-268, Jun.-Sep. 1985.
Atlantic Richfield Company
Brown Peter Toby
Hille Rolf
Mantooth Geoffrey A.
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