Passive intrusion detection system

Claim 3

An intrusion detection system as recited in claim 1: wherein said RF transmission cable means terminates at a second end remote from said RF generating means in a corresponding termination impedance; and wherein said monitoring means includes reflectometry means for determining the location of source of a reflection of the RF energy.

Claim 4

An intrusion detection system as recited in claim 2: wherein said RF generating means produces periodic RF pulses for energizing said RF transmission cable means; and wherein said reflectometry means comprises means for determining the position of each reflection by time-domain reflectometry.

Claim 5

An intrusion detection system as recited in claim 2: wherein said RF generating means produces a variable RF frequency signal in an iterative fashion; and wherein said reflectometry means includes means for determining the position of each reflection by frequency-domain reflectometry.

Claim 6

An intrusion detection system as recited in claim 2 wherein said monitoring means additionally comprises time display means connected to said reflectometry means for displaying representations of the reflected RF energy over an expanded time interval.

Claim 7

An intrusion detection system as recited in claim 2 wherein the area comprises earth at the perimeter and said RF transmission cable means comprises a compressible RF transmission cable buried at the perimeter whereby weight applied to the surface of the earth at the perimeter deforms said transmission cable thereby to alter the impedance at a corresponding location.

Claim 8

An intrusion detection system as recited in claim 2 additionally comprising discrete sensor means for monitoring a condition, said sensor means having the characteristic impedance and being attached to the second end of the RF transmission cable means and said monitoring means additionally includes means for monitoring signals from said sensor means.

Claim 9

An intrusion detection system as recited in claim 2 additionally comprising means for altering the characteristic impedance of said RF transmission cable means in response to an external event.

Claim 10

An intrusion detection system as recited in claim 2 additionally comprising RF energy control means for controlling the characteristics of the RF energy applied to said RF transmission cable means.

Claim 11

An intrusion detection system as recited in claim 1 wherein said RF transmission cable means includes a first RF transmission cable, at least one additional RF transmission cable and connector means for connecting each additional RF transmission cable in parallel with at least a portion of the first RF transmission cable without changing the characteristic impedance.

Claim 12

An intrusion detection system as recited in claim 1 wherein said RF transmission cable means comprises a single RF transmission cable with portions thereof being positioned in a serpentine pattern whereby at least one portion lies physically essentially parallel to another portion.

Claim 13

An intrusion detection system as recited in claim 11 having at least one additional RF transmission cable and connector means for connecting each additional RF transmission cable in parallel with at least a portion of the single RF transmission cable without changing the characteristic impedance.

Claim 14

An intrusion detection system for detecting any intrusion past a perimeter of an area, said system comprising: an RF transmission cable having a conductor structure consisting of first and second conductors arranged symmetrically about a central axis and having a dielective material that spaces said first and second conductors thereby to form a cable with a characteristic impedance throughout its length that, at any point, can change in response to a change in the spacing of the conductors, said RF transmission cable being buried at the perimeter at a depth that enables the spacing change to occur in response to weight applied proximate the buried cable and having first and second ends; an RF energy source for directing RF energy into the first end of the transmission cable whereby a portion of the electrical energy in a pulse is reflected from any point in said RF transmission cable that has an impedance that differs from the characteristic impedance; and a reflectometer connected to the first end of the RF transmission cable for producing an indication that an intrusion has occurred and the location of that intrusion in response to reflected energy.

Claim 15

An intrusion detection system for detecting any intrusion past a perimeter of an area, said system comprising: an RF transmission cable having a conductor structure consisting of first and second conductors arranged symmetrically about a central axis and having a dielective material that spaces said first and second conductors thereby to form a cable with a characteristic impedance throughout its length that, at any point, can change in response to a change in the spacing of the conductors, said RF transmission cable being buried at the perimeter at a depth that enables the spacing change to occur in response to weight applied proximate the buried cable and having first and second ends; an RF energy source for directing RF energy into the first end of the transmission cable whereby a portion of the electrical energy in a pulse is reflected from any point in said RF transmission cable that has an impedance that differs from the characteristic impedance; and a reflectometer connected to the first end of the RF transmission cable for producing an indication that an intrusion has occurred and the location of that intrusion in response to reflected energy.

Claim 16

An intrusion detection system as recited in claim 13 wherein portions of said RF transmission cable extend in a serpentine fashion such that portions of the cable lie along essentially parallel paths.

Claim 17

An intrusion detection system as recited in claim 13 wherein said reflectometer uses time-domain reflectometry for determining the position of any intrusion along the cable.

Claim 18

An intrusion detection system as recited in claim 13 wherein said reflectometer uses frequency-domain reflectometry for determining the position of any intrusion along the cable.

Claim 19

An intrusion detection system as recited in claim 13 additionally comprising: discrete sensor means for monitoring a condition, said sensor means having the characteristic impedance and being attached to the second end of the RF transmission cable; and means for monitoring signals from said sensor means.

Claim 20

An intrusion detection system as recited in claim 13 wherein said transmission cable comprises coaxial cable.

Claim 21

An intrusion detection system as recited in claim 13 additionally comprising time display means connected to said reflectometer for displaying representations of the reflected energy over a time interval.

Claim 22

An intrusion detection system as recited in claim 13 additionally comprising means for altering the characteristic impedance of said RF transmission cable in response to an external event.

Claim 23

An intrusion detector system as recited in claim 13 additionally comprising an RF energy control unit for varying the characteristics of said RF energy source during the operation of said intrusion detection system.

Claim 24

An intrusion detection system as recited in claim 13 wherein said RF transmission cable extends around the area and includes at least one additional RF transmission cable connected electrically in parallel thereto.