Quick response perimeter intrusion detection sensor

• US 6,208,248 B1
• Filed: 01/28/1999
• Issued: 03/27/2001
• Est. Priority Date: 01/28/1999
• Status: Expired due to Fees

• Current Assignee: ANRO Engineering Incorporated
• Original Assignee: ANRO Engineering Incorporated
• Inventors: Ross, Gerald F.
• Primary Examiner(s): SWANN III, GLEN R
• Application Number:
  US09/239,352
• Time in Patent Office: 789 Days
• Field of Search: 340/554, 340/552, 342/28, 342/21, 342/160, 342/159
• US Class Current: 340/552
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/18 wherein range gates are used
• CPC Class Codes: G01S 13/886 for alarm systems alarms with electrical actuation G08B13/22
• CPC Class Codes: G01S 7/2922 by using a controlled threshold

Abstract

An Ultra Wideband (UWB) short-range radar system is used for the detection of targets in clutter. Examples of targets on the ground include human walkers, crawlers and runners, and vehicles. The UWB sensor can also be used to detect small approaching boats in different levels of sea clutter or airborne targets like hang gliders. One of the primary differences between this device and other UWB radar sensors is the manner in which the bias on the threshold detector is set as well as the logic circuitry used to find targets in clutter while maintaining a low false alarm rate. The processing is designed to detect targets in varying degrees of clutter automatically. There may be no front panel controls other than an ON-OFF switch. The system is lightweight, low-cost, and can be easily installed in minutes.

Claims

1. An Ultra Wideband (UWB) short range covert sensor for detection of an intruder in a cluttered environment, comprising:

a transmitting dipole element cut to be half wave resonant at a predetermined frequency and fed by a wideband balun to produce a radiated signal which is noise-like in appearance to search said cluttered environment looking for said intruder;

a UWB Marx generator for generating a baseband pulse to excite said wideband balun;

a system clock to set the pulse repetition frequency (PRF) of said sensor to a lowest value to detect a fastest expected target traveling radially towards said sensor, said system clock including a random number generator for randomizing pulses being sent to said generator, said system clock further generating a pulse train sequence and a clock pulse sequence;

a range gate controller responsive to said pulse train sequence and said clock pulse sequence for generating a sequential range gate signal of a predetermined duration;

a receiving dipole element for receiving a reflected signal from said cluttered environment and generating a plurality of signals indicating an amount of noise and clutter;

a register for storing bits representative of said plurality of signals and generating an output signal if there is an increase or decrease in said bits by more than a predetermined amount;

a signal processor responsive to said output signal and said range gate signal to generate an alarm signal indicating the presence of said intruder;

an alarm which is activated by receiving said alarm signal and may be reset either manually or remotely.

2. The sensor of claim 1 wherein a one-shot multivibrator triggers said Marx generator to produce said baseband pulse of typically up to a 1400 volt baseband pulse.

3. The sensor of claim 2 wherein said system clock includes:

a 40 MHz oscillator for generating said pulse train sequence;

said random generator for generating a series of random pulse sequences;

a divider for receiving said pulse train sequence and said random signals to generate a 1.22 kHz signal which jitters said PRF by typically 90% thereby resulting in said radiated signal being noise-like in appearance.

4. The sensor of claim 3 wherein said range gate controller includes:

a network for receiving said clock signal and generating a sequence of S pulses;

an astable multivibrator for receiving said sequence of S pulses and producing alternately high and low signals typically every 100 milliseconds;

an OR network for receiving said alternately high and low signals thereby producing a 100 millisecond duration train of pulses offset from a next series of pulses by a time corresponding to 150 feet of space;

a multivibrator network for receiving said 100 millisecond duration train of pulses and said pulse train sequence for generating said sequential range gate signal corresponding to an A range distance and an A′

range distance, each having said predetermined duration of typically 105 milliseconds.

5. The sensor of claim 4 wherein said receiving dipole element includes;

a bandpass circuit for filtering said reflected signal from incidental radiation;

a variable preamplifier having a maximum gain of 40 dB for receiving and amplifying said filtered signals and having the capability for accepting targets in high sea clutter caused by high seas;

a modified tunnel diode CFAR threshold detector which is self biased on noise and clutter to receive said amplified filtered signals to generate said plurality of signals;

a one shot responsive to said sequential range gate signal for generating a timing pulse;

a range gate responsive to said clock pulse sequence and said timing pulse to generate a timing gate signal;

said threshold detector being responsive to said timing gate signal for timing said radiated signal to said reflected signal.

6. The sensor of claim 5 wherein said register generates said output signal if there is an increase or decrease of, typically, eight bits indicating said intruder.

7. The sensor of claim 6 wherein said signal processor includes:

a high bit and a low bit threshold detector for receiving said output signal;

an OR gate coupled to said high and said low bit threshold detector for generating a trigger pulse;

a range generator selection network is responsive to said trigger pulse for shifting said range gate to position B if said range gate was at positions A or A′

, and shifting said range gate to position C and generating said alarm signal if said range gate was at position B.

8. A method of using an Ultra-Wideband (UWB) short range sensor for a detection of an intruder in a cluttered environment, including the steps of:

A. Setting a range gate of said sensor of a predetermined width to scan a cluttered area at a distance A from said sensor for a predetermined time interval,

B. Switching said range gate to scan said cluttered area at a distance A′

from said sensor for if no intruder is detected where said distance A is greater than said distance A′

,

C. Alternately switching said range gate between said distance A and said distance A′

after said predetermined time interval,

D. Detecting a potential intruder at said distance A or said distance A′

,

E. Reducing said range gate to a distance B wherein said distance B is less by a predetermined distance from said distance A if said intruder was detected at said distance A, and said distance B is less by said predetermined distance from said distance A′

if said intruder was detected at said distance A′

,

F. Detecting said intruder at said distance B within a prescribed time period,

G. Reducing said range gate to a distance C wherein said distance C is less by said predetermined distance from said distance B,

H. Detecting said intruder at said distance C within said prescribed time period,

I. Triggering an alarm,

J. Returning to step A if no intruder is detected at said range set at said distance B or said distance C within said prescribed time period.

9. The method of claim 8 wherein,

said predetermined width of said range gate is typically about 12 feet, said range gate at said distance A is typically set at 300 feet to detect a walker or a runner in said cluttered environment, and said range at said distance A′ is typically set at 150 feet to detect a crawler in said cluttered environment.

10. The method of claim 9 wherein,

said distance B is typically about 12 feet less than said distance A and said distance A′

and said distance C is typically about 12 feet less than said distance B, and said prescribed time period is typically 45 seconds.

11. An Ultra-Wideband (UWB) short-range covert sensor for a detection of an intruder in a cluttered environment, comprising:

a network for sending a sequence of noise-like range gate signals to said cluttered environment;

a receiver for receiving a first sequence of reflected signals from said cluttered environment from a first band at a first predetermined distance from said sensor for detecting said intruder who is upright, and alternatively from a second band at a second predetermined distance from said sensor for detecting said intruder who is crawling, said second band being closer to said sensor than said first band;

a processor for analyzing said first sequence of reflected signals and generating a first detection signal having a first value if said intruder is detected within said first or said second band;

said receiver being responsive to said first detection signal having said first value for receiving a second sequence of reflected signals from a third band, said third band being closer to said sensor than the corresponding said first or said second band;

said processor further analyzing said second sequence of reflected signals and generating a second detection signal having a first value if said intruder is detected within said third band;

said receiver being further responsive to said second detection signal in said first state for receiving a third sequence of reflected signals from a fourth band, said fourth band being closer to said sensor from said third band;

said processor further analyzing said third sequence of reflected signals and generating an alarm signal if said intruder is detected within said fourth band;

said receiver receiving said first sequence of reflected signals if said processor generates said first or said second detection signals having a second value indicating a false detection of said intruder.

12. The sensor of claim 11 wherein said first band, said second band, said third band and said fourth band each have a width of 12 feet with said first predetermined distance being typically 300 feet and said second predetermined distance being typically 150 feet, said third band abutting said first or said second band, and said fourth band, similarly abutting the corresponding said third band.

13. An Ultra-Wideband (UWB) short-range covert sensor for a detection of a glider approaching said sensor comprising:

a network for sending a sequence of noise-like range gate signals to an area in which said glider will approach;

a receiver for receiving a first sequence of reflected signals from said first band at a predetermined distance from said sensor for detecting said glider;

a processor for analyzing said first sequence of reflected signals and generating a first detection signal having a first value if said glider is detected within said first band;

said receiver being responsive to said first detection signal having said first value for receiving a second sequence of reflected signals from a second band, said second band being closer to said sensor than said first band;

said processor further analyzing said second sequence of reflected signals and generating a second detection signal having a first value if said intruder is detected within said second band;

said receiver being further responsive to said second detection signal having said first value for receiving a third sequence of reflected signals from a third band, said third band being closer to said sensor than the corresponding said first or said second band;

said processor further analyzing said third sequence of reflected signals and generating an alarm signal if said intruder is detected within said third band.

14. The sensor of claim 13 wherein said said first band, said second band, said third band each have a width of typically 50 feet with said predetermined distance being typically 500 feet with said second band abutting said first band and said third band abutting said second band, said third band being closest to said sensor.