Apparatus for the remote detection of conducting bodies utilizing electromagnetic waveforms exhibiting abrupt discontinuities

Claim 2

Apparatus for the remote detection of conducting bodies, comprising: a. a pulse generator for generating a sequence of pulses; b. transmitter means for radiating a primary electromagnetic waveform exhibiting abrupt discontinuities at times determined by said sequence of pulses; c. inductive receiving means for discerning secondary signals induced by said primary waveforms and reradiated by a conducting body together with any transient components of said secondary signals occurring after said abrupt discontinuities in the primary waveform; d. amplification means for amplifying the discerned signals; e. electronic gating means operable intermittently to sample said secondary transient components following said abrupt discontinuities in the primary waveform; f. means responsive to said sequence of pulses for intermittently operating said gating means for gating said secondary transient components whereby to derive a repetitive waveform characteristic of a sequence of said secondary transient components; g. further amplification means connected to said gating means for amplifying said repetitive waveform; h. a signal averager connected to receive the repetitive waveform, the signal averager providing a plurality of channels with outputs representing the average values of sequential portions of the repetitive waveform; and i. recording means connected to said channels for recording said outputs.

Claim 3

Apparatus according to claim 1, in which the signal averager has an analogue memory comprising a plurality of memory elements each consisting of a capacitor and a field effect transistor, and means for scanning the memory elements sequentially by sequentially and cyclically triggering the field effect transistors.

Claim 4

Apparatus for the remote detection of conducting bodies, comprising: a. a pulse generator for generating a sequence of pulses; b. transmitter means for radiating a primary electromagnetic waveform exhibiting abrupt discontinuities at times determined by said sequence of pulses; c. inductive receiving means for discerning secondary signals induced by said primary waveforms and reradiated by a conducting body together with any transient components of said secondary signals occurring after said abrupt discontinuities in the primary waveform; d. amplification means for amplifying the discerned signals; e. a differential amplifier having a pair of opposite polarity input terminals and an output terminal; f. electronic gating means operable intermittently to sample said secondary transient components following said abrupt discontinuities in the primary waveform, said gating means consisting of first and second gating circuits connected between said amplification means and a respective one of said opposite polarity input terminals; g. means responsive to said sequence of pulses for intermittently operating said first and second gating circuits alternately whereby each gating circuit gates secondary transient components of a respective polarity; h. said differential amplifier deriving a repetitive waveform of uniform polarity characteristic of a sequence of said secondary transient components; i. a signal averager connected to receive the repetitive waveform, the signal averager providing a plurality of channels with outputs representing the average values of sequential portions of the repetitive waveform; and j. recording means connected to said channels for recording said outputs.

Claim 5

Apparatus for the remote detection of conducting bodies, comprising: a. a pulse generator for generating a sequence of pulses; b. transmitter means for radiating a primary electromagnetic waveform exhibiting abrupt discontinuities at times determined by said sequence of pulses; c. inductive receiving means for discerning secondary signals induced by said primary waveforms and reradiated by a conducting body together with any transient components of said secondary signals occurring after said abrupt discontinuities in the primary waveform; d. amplification means for amplifying the discerned signals; e. a differential amplifier having a pair of opposite polarity input terminals and an output terminal; f. electronic gating means operable intermittently to sample said secondary transient components following said abrupt discontinuities in the primary waveform, said gating means consisting of first and second gating circuits connected between said amplification means and a respective one of said opposite polarity input terminals; g. means responsive to said sequence of pulses for intermittently operating said first and second gating circuits alternately whereby each gating circuit gates secondary transient components of a respective polarity; h. said differential amplifier deriving a repetitive waveform of uniform polarity characteristic of a sequence of said secondary transient components; i. a signal averager connected to receive the repetitive waveform, the signal averager providing a plurality of channels with outputs representing the average values of sequential portions of the repetitive waveform; and j. recording means connected to said channels for recording said outputs.

Claim 6

Apparatus according to claim 3, including low pass filter means interposed between the signal averager and the recording means for filtering out ripple derived from the repetitive waveform.

Claim 7

Apparatus according to claim 4, wherein each of said gating circuits comprises a normally non-conducting, series-connected, N-type field effect transistor and a normally conducting, shunt-connected, P-type field effect transistor, each transistor having a gate connected to receive trigger pulses from said operating means for reversing the respective states of the transistors in accordance with the presence of such pulses.