Homodyne impulse radar hidden object locator

Claim 2

An electromagnetic detector for locating an object behind a separator, comprising: a signal generator for generating a sequence of pulses having a predetermined frequency; a step generator connected to said signal generator for producing a sequence of transmit pulses; a homodyne oscillator connected to said step generator for modulating said sequence of transmit pulses at a homodyne modulation frequency; a transmit antenna connected to said step generator for transmitting said modulated sequence of transmit pulses in the direction of the separator; a receive antenna for receiving reflected pulses from the object; an averaging sample and hold (S/H) circuit connected to the receive antenna for sampling a plurality of reflected pulses to produce an average reflected signal; a gating switch connected between the receive antenna and the S/H circuit and to the signal generator so that only reflected pulses from a selected range are sampled by the S/H circuit: a DC bias rejection filter connected to the output of the S/H circuit for significantly reducing near wall proximity effect on said receive antenna; a demodulator connected to the output of the DC bias rejection filter and to the homodyne oscillator to remove the homodyne modulation frequency from the reflected signal.

Claim 3

The detector according to claim 1, wherein said DC bias rejection filter comprises an AC coupled amplifier which filters out DC bias level shifts in said receive antenna.

Claim 4

The detector according to claim 2, wherein said demodulator comprises a rectifier circuit connected to said homodyne oscillator and to said AC coupled amplifier, for synchronously rectifying the reflected pulses to remove the homodyne modulation frequency.

Claim 5

The detector according to claim 3, wherein said homodyne oscillator modulates said sequence of transmit pulses with a continuous wave (CW) signal.

Claim 6

The detector according to claim 4, wherein said AC coupled amplifier operates with a passband centered on said CW signal.

Claim 7

The detector according to claim 5, wherein said homodyne oscillator operates at several kHz: wherein said signal generator is a pulse repetition frequency (PRF) generator which operates in the range of 1 MHz to several MHz.

Claim 8

The detector according to claim 1, further comprising a DC coupled amplifier connected to the demodulator for amplifying the demodulated output of the S/H circuit.

Claim 9

The detector according to claim 7, further including a display connected to the amplifier.

Claim 10

The detector according to claim 8, wherein said display comprises a plurality of visual indicators that are sequentially energized in proportion to the voltage applied thereon; and wherein said applied voltage is linearly related to the magnitude of the reflected pulses.

Claim 11

The detector according to claim 1, further comprising an adjustable delay connected between the signal generator and gating switch for setting a predetermined detection range (range gating) from said transmit antenna.

Claim 12

The detector according to claim 10 further comprising a second step generator between the adjustable delay and gating switch.

Claim 13

An electromagnetic detector for locating a cavity within a separator, comprising: a signal generator for generating a sequence of pulses having a predetermined shape and frequency; a step generator connected to said signal generator for producing a sequence of transmit pulses: a homodyne oscillator connected to said step generator for modulating said sequence of transmit pulses at a homodyne modulation frequency; a transmit antenna connected to said step generator for transmitting said modulated sequence of transmit pulses through said separator; a receive antenna for receiving reflected pulses from the cavity; an averaging sample and hold (S/H) circuit connected to the receive antenna for sampling a plurality of reflected pulses to produce an average reflected signal; a gating switch connected between the receive antenna and the S/H circuit; and to the signal generator so that only reflected pulses from a selected range are sampled by the S/H circuit: a DC bias rejection filter for significantly reducing near wall proximity effect on said receive antenna; said filter comprising an AC coupled amplifier connected to the output of the S/H circuit for filtering out DC bias level shifts in said receive antenna; and a rectifier circuit connected to said homodyne oscillator and to said AC coupled amplifier, for synchronously rectifying said reflected pulses to remove the homodyne modulation frequency.

Claim 14

An electromagnetic detector for locating a cavity within a separator, comprising: a signal generator for generating a sequence of pulses having a predetermined shape and frequency; a step generator connected to said signal generator for producing a sequence of transmit pulses: a homodyne oscillator connected to said step generator for modulating said sequence of transmit pulses at a homodyne modulation frequency; a transmit antenna connected to said step generator for transmitting said modulated sequence of transmit pulses through said separator; a receive antenna for receiving reflected pulses from the cavity; an averaging sample and hold (S/H) circuit connected to the receive antenna for sampling a plurality of reflected pulses to produce an average reflected signal; a gating switch connected between the receive antenna and the S/H circuit; and to the signal generator so that only reflected pulses from a selected range are sampled by the S/H circuit: a DC bias rejection filter for significantly reducing near wall proximity effect on said receive antenna; said filter comprising an AC coupled amplifier connected to the output of the S/H circuit for filtering out DC bias level shifts in said receive antenna; and a rectifier circuit connected to said homodyne oscillator and to said AC coupled amplifier, for synchronously rectifying said reflected pulses to remove the homodyne modulation frequency.

Claim 15

The detector according to claim 12, further including a display connected to the output of the rectifier circuit and which comprises a plurality of indicators that are sequentially energized in proportion to the voltage applied thereon; and wherein said applied voltage is linearly related to the magnitude of said reflected pulses.

Claim 16

The detector according to claim 13, further comprising an adjustable delay connected between the signal generator and gating switch for setting a predetermined detection range (range gating) from said transmit antenna.

Claim 17

The detector according to claim 12, wherein said homodyne oscillator generates a homodyne signal which includes an arbitrary sequence of pulses having a mean frequency on the order of several kHz and a zero average.

Claim 18

An automated tool arrangement for use relative to an object behind a separator comprising in combination: two or more generally identical detectors, mounted on a tool housing; said detectors being distally separated from each other; and each of said detectors comprising: a signal generator for generating a sequence of pulses having a predetermined shape and frequency; a step generator connected to said signal generator for producing a sequence of transmit pulses: a homodyne oscillator connected to said step generator for modulating said sequence of transmit pulses at a homodyne modulation frequency; a transmit antenna connected to said step generator for transmitting said modulated sequence of transmit pulses through said separator; a receive antenna for receiving reflected pulses from the object; an averaging sample and hold (S/H) circuit connected to the receive antenna for sampling a plurality of reflected pulses to produce an average reflected signal: a gating switch connected between the receive antenna and the S/H circuit and to the signal generator so that only reflected pulses from a selected range are sampled by the S/H circuit; a DC bias rejection filter connected to the output of the S/H circuit for significantly reducing near wall proximity effect on said receive antenna; a demodulator connected to the output of the DC bias rejection filter and to the homodyne oscillator to remove the homodyne modulation frequency from the reflected signal.

Claim 19

An automated tool arrangement for use relative to an object behind a separator comprising in combination: two or more generally identical detectors, mounted on a tool housing; said detectors being distally separated from each other; and each of said detectors comprising: a signal generator for generating a sequence of pulses having a predetermined shape and frequency; a step generator connected to said signal generator for producing a sequence of transmit pulses: a homodyne oscillator connected to said step generator for modulating said sequence of transmit pulses at a homodyne modulation frequency; a transmit antenna connected to said step generator for transmitting said modulated sequence of transmit pulses through said separator; a receive antenna for receiving reflected pulses from the object; an averaging sample and hold (S/H) circuit connected to the receive antenna for sampling a plurality of reflected pulses to produce an average reflected signal: a gating switch connected between the receive antenna and the S/H circuit and to the signal generator so that only reflected pulses from a selected range are sampled by the S/H circuit; a DC bias rejection filter connected to the output of the S/H circuit for significantly reducing near wall proximity effect on said receive antenna; a demodulator connected to the output of the DC bias rejection filter and to the homodyne oscillator to remove the homodyne modulation frequency from the reflected signal.

Claim 20

The automated tool arrangement according to claim 16, wherein said detectors are substantially symmetrically positioned relative to the object.

Claim 21

The automated tool arrangement according to claim 17, further including a tool which is activated as said detectors approach a desired position relative to an object.

Claim 22

The automated tool arrangement according to claim 18, wherein the tool is a nail gun.

Claim 23

An automated tool arrangement comprising in combination: a transmitter unit; two separate receiver units disposed generally equidistally on either side of said transmitter unit; said transmitter unit and receiver units being mounted on a tool; said transmitter unit comprising: a PRF generator for producing a sequence of pulses; a transmit pulse step generator connected to the PRF generator for generating a sequence of transmit pulses; a homodyne oscillator connected to the transmit pulse step generator to modulate the sequence of transmit pulses; a transmit antenna connected to the transmit pulse step generator for transmitting said modulated sequence of transmit pulses; an adjustable delay connected to the PRF generator to produce a delayed sequence of pulses; a gate pulse step generator connected to the adjustable delay; a pulse differentiator connected to the gate pulse step generator to produce a sequence of gate pulses; each receiver unit comprising: a receive antenna for receiving reflected pulses from an object; a sample and hold (S/H) circuit connected to the receive antenna for sampling a plurality of reflected pulses to produce an averaged detected signal; an AC coupled amplifier connected to the output of the S/H circuit to subtract DC bias level shifts caused by near wall proximity effects on the receive antenna; a synchronous rectifier connected to the output of the AC coupled amplifier and to the homodyne oscillator for demodulating the averaged detected signal: a DC coupled amplifier connected to the output of the rectifier for producing an amplified demodulated detected signal; a display connected to the DC coupled amplifier for displaying changes in the amplified demodulated detected signal; wherein said transmit unit transmits a common gate pulse to both receiver units.

Claim 24

An automated tool arrangement comprising in combination: a transmitter unit; two separate receiver units disposed generally equidistally on either side of said transmitter unit; said transmitter unit and receiver units being mounted on a tool; said transmitter unit comprising: a PRF generator for producing a sequence of pulses; a transmit pulse step generator connected to the PRF generator for generating a sequence of transmit pulses; a homodyne oscillator connected to the transmit pulse step generator to modulate the sequence of transmit pulses; a transmit antenna connected to the transmit pulse step generator for transmitting said modulated sequence of transmit pulses; an adjustable delay connected to the PRF generator to produce a delayed sequence of pulses; a gate pulse step generator connected to the adjustable delay; a pulse differentiator connected to the gate pulse step generator to produce a sequence of gate pulses; each receiver unit comprising: a receive antenna for receiving reflected pulses from an object; a sample and hold (S/H) circuit connected to the receive antenna for sampling a plurality of reflected pulses to produce an averaged detected signal; an AC coupled amplifier connected to the output of the S/H circuit to subtract DC bias level shifts caused by near wall proximity effects on the receive antenna; a synchronous rectifier connected to the output of the AC coupled amplifier and to the homodyne oscillator for demodulating the averaged detected signal: a DC coupled amplifier connected to the output of the rectifier for producing an amplified demodulated detected signal; a display connected to the DC coupled amplifier for displaying changes in the amplified demodulated detected signal; wherein said transmit unit transmits a common gate pulse to both receiver units.

Claim 25

The automated tool arrangement according to claim 20, wherein said tool is activated as said transmit and receiver units approach a desired position relative to an object.