WO2000075892A2 - Signal processsing for object detection system - Google Patents
Signal processsing for object detection system Download PDFInfo
- Publication number
- WO2000075892A2 WO2000075892A2 PCT/US2000/014509 US0014509W WO0075892A2 WO 2000075892 A2 WO2000075892 A2 WO 2000075892A2 US 0014509 W US0014509 W US 0014509W WO 0075892 A2 WO0075892 A2 WO 0075892A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- radiation
- target
- polarized
- reflected
- person
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/887—Radar or analogous systems specially adapted for specific applications for detection of concealed objects, e.g. contraband or weapons
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/024—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using polarisation effects
- G01S7/025—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using polarisation effects involving the transmission of linearly polarised waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
- G01S7/411—Identification of targets based on measurements of radar reflectivity
- G01S7/412—Identification of targets based on measurements of radar reflectivity based on a comparison between measured values and known or stored values
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/12—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with electromagnetic waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/288—Coherent receivers
- G01S7/2883—Coherent receivers using FFT processing
Definitions
- Chadwick is a U.S. citizen, and resides at 424 Sand Hill Circle, Menlo Park, California
- Mr. Thomas C. Weakley is a U.S. citizen, and resides at 201 Belgatos Road, Los
- the present invention is a system for remotely detecting the presence of an object. More particularly, one preferred embodiment of the invention supplies methods and apparatus for sensing concealed weapons to create a "Safe ZoneTM " The invention also includes novel signal processing methods and apparatus for providing high reliability object detection.
- the present invention comprises methods and apparatus for detecting the presence of an object at a distance.
- One embodiment of the invention may be used to locate a concealed firearm carried by a person.
- the invention may be used to help keep weapons out of any secure area or "Safe ZoneTM," such as a school, bank, airport, embassy, prison, courtroom, office building, retail store or residence.
- Safe ZoneTM is a Trade and Service Mark owned by the Assignee of the present Patent Application, The MacAleese Companies, doing business as Safe ZoneTM Systems, Incorporated.
- One embodiment of the invention utilizes low-power, horizontally polarized radio waves to illuminate a target, such as a person who may be entering a doorway.
- Radio waves reflected from the target are gathered by a receive antenna and then processed by a detector circuit.
- the presence of the concealed weapon is determined by solving an algorithm which utilizes measured differences in the amplitudes of waveforms that represent different polarized energy levels reflected back from the target, and which also utilizes stored values which represent the expected response of a person who is not carrying a weapon, as well as the response of a person carrying a weapon.
- Novel signal processing techniques are then utilized to improve the reliability of the detection method.
- radiation reflected from the target is sensed and converted to a signal which is processed using Fast Fourier Transforms.
- this method separates a first signal which is generated by radiation reflected from the target, that is generally well-behaved, from a second signal, which is generated by radiation reflected from a human body, that is generally chaotic.
- One embodiment of the present invention offers the additional benefits of being compact, lightweight, long-range, portable and battery-operated.
- the invention may be incorporated into automatic door-opening equipment.
- the invention may be used to locate inexpensive tags attached to merchandise as an inventory control and anti-shoplifting system.
- Figure 1A illustrates a simple wave
- Figure IB illustrates a simple wave that is vertically polarized.
- Figure 1C illustrates a simple wave that is horizontally polarized.
- Figure 2 offers pictorial views of test setups for one embodiment of the present invention.
- Figure 3 provides a schematic block diagram of one embodiment of a transmission and detection circuit.
- Figure 4 portrays persons carrying guns in different locations relative to the body.
- Figure 5 is a viewgraph which explains the unit of radiation measurement, dBsm.
- Figure 6 is a chart which provides information concerning the radar cross section of a handgun.
- Figure 7A is a graph showing the radar cross section of a handgun for a particular range of frequencies, plotting reflected energy in dBsm versus frequency.
- Figure 7B is a graph showing the radar cross section of a human body for a particular range of frequencies, plotting reflected energy in dBsm versus frequency.
- Figures 8 and 9 are graphs which supply information concerning the reflectivity of the human body when illuminated with radio waves in the 2.59 to 3.95 GHz and 7.0 to 10.66 frequency bands.
- Figure 10 furnishes a pictorial description of the present invention.
- the two graphs at the right of the drawing show that an object such as a handgun may be detected by comparing the time domain difference in amplitudes of two sets of waveforms which correspond to reflected radio waves having different polarizations.
- the two waveforms represent the vertically and horizontally polarized radio waves reflected back to the detector.
- the maximum amplitudes of the waveforms are spread relatively far apart.
- the difference between the maximum amplitudes of the waveforms is substantially decreased.
- Figure 11 is a viewgraph that offers test data regarding the detection of a handgun in accordance with the present invention using the 9.5 to 10.6 GHz frequency bands.
- the transmit signal is vertically polarized.
- Figure 12 supplies actual test data concerning the detection of a handgun at the 2.9 to 3.25 GHz frequency band.
- the transmit signal is horizontally polarized.
- Figures 13 and 14 are actual test equipment plots of two pairs of time domain waveforms generated during a handgun detection experiment.
- the person was not carrying a gun, and the maximum values of the two curves are far apart.
- Figure 14 the same person was carrying a handgun, and the distance between the high points of the two curves appears much closer together, correctly indicating the presence of a gun.
- Figures 15, 16, 17 and 18 exhibit laboratory test data for experiments conducted at two different frequency bands.
- the transmitted signal is a horizontally polarized signal.
- the received signal is both horizontally and vertically polarized.
- Figures 19 and 20 provide power versus azimuth angle plots for two 8 by 8 antenna arrays using two different frequency bands.
- Figures 21 and 22 supply operational parameters for the present invention for two different frequency bands.
- Figures 23 and 24 portray a triangular waveform that may be employed in an alternative embodiment of the invention to generate the required frequency domain waveform for detecting an object in the 2.9 to 3.25 and 9.55 to 10.66 GHz frequency bands.
- Figure 25 is a plot of phase versus frequency for a .357 caliber pistol, and a sample of the return from a moving human body.
- Figure 26 reveals a reduction in the return from the body because of its uncorrelated nature.
- Figure 27 depicts the return from the .357 weapon. Its phase is correlated and its magnitude is unchanged.
- Figures 28 and 29 supply schematic block diagrams of circuitry that is used in a preferred embodiment of the invention to measure phase of the returned cross-pole signal.
- Figure 30 is a general illustration of the phase and amplitude response used for the Complex FFTs that are employed in a preferred embodiment of the invention.
- Figure 31 offers an operational system flow diagram
- Figure 32 offers a flowchart which explains how a preferred embodiment of the invention is calibrated.
- the shape of a simple radio signal can be depicted as a repeated up and down movement or vibration, as shown in Figure 1A. This up and down motion of the wave takes place in three dimensions.
- the simple wave (W) propagates. A wave which is polarized parallel to the plane of propagation is called a horizontally polarized wave. A wave which is polarized pe ⁇ endicular to the plane of propagation is called a vertically polarized wave. The height or intensity of the wave W is called the amplitude (A) of the wave.
- Figure IB exhibits a wave which is vertically polarized
- Figure 1C reveals a wave which is horizontally polarized.
- Vertical and horizontal polarizations are said to be orthogonal forms of polarization.
- Other terms that may be used to describe the relationship between waves that are vertically and horizontally polarized are perpendicular, opposite, cross-polarized, or main and complementary.
- polarization is applicable to all forms of transverse electromagnetic waves, whether they are radio waves at microwave frequenices, or light waves such as those emitted by a flashlight.
- FIG. 2 depicts laboratory apparatus that may be used to practice one embodiment of the invention.
- a low-power radio transmitter coupled to a transmit antenna (T x ) is used to illuminate a target inside an anechoic chamber.
- a receive antenna (R x ) collects energy reflected back from the target within the chamber.
- a single dual polarized antenna may be used in some embodiments of the present invention.
- a conventional metal .357 caliber pistol is employed.
- the term "target" refers to a physical item toward which illuminating radiation is pointed. The target is usually a person.
- the term "object” refers to a physical item that is carried on, worn or somehow physically attached, coupled or associated with a target.
- the object that is detected is a concealed weapon.
- the power levels radiated by the present invention are much lower than conventional radar systems or than those generated by x-ray or other imaging systems that are currently employed to detect objects at the entry of an ai ⁇ ort or a courtroom.
- some of the preferred embodiments of the invention operate in the GHz frequency bands.
- Different radio frequencies offer different benefits and disadvantages for the object detection provided by the present invention.
- operating frequencies of radio devices are regulated by the Federal Communications Commission.
- Each country across the globe has similar regulatory bodies which allocate and administer the use of the radio spectrum.
- the description of some embodiments of the invention include specific references to particular frequency ranges, the system may be beneficially implemented using a wide variety of electromagnetic radiation bands.
- FIG. 3 presents a schematic block diagram 10 of circuitry that may be used to implement one embodiment of the invention.
- a transmitter 12 is coupled to a modulator 14, a filter 16, and a transmitter amplifier 18. This amplifier 18 is connected to an antenna 24 through a first transmit/receive switch 20 and a pre-selector 22.
- the transmit/receive switch 20 is also connected to a range gate control 21.
- a processor 26 is used to control transmitter 12.
- the output of a local oscillator ramp generator with start/stop/slope programming 28 is connected to modulator 14 and to a local oscillator/voltage control oscillator 30.
- the output of the local oscillator 30 is fed to a mixer 32.
- An output of transmit/receive switch 20 is also fed to mixer 32 through a filter 36 and a receive low-noise amplifier 34.
- An output from the processor 26 is conveyed to an automatic gain control programming digital to analog converter 38.
- An output from the D/A converter 38 controls an intermediate frequency gain control amplifier 44, which also receives an input from a mixer 32 through range gate switch 40 and band pass filter 42.
- An output from the LF GC amplifier then passes through detector 46, video amplifier 48, a gated sample and hold stretcher 50, an output amplifier 52 and an analog-to-digital converter 54 before being fed back to processor 26.
- Figure 3 includes a section labeled "Block A" which includes circuit elements 30, 32, 34, 36, 40, 42, 44, 46, 48, 50, 52 and 54.
- This block is duplicated in the circuit, but is shown as a second rectangle drawn in dashed line at the bottom of the figure. This lower rectangle is labeled with the legend "This is a repeat of Block A" and with the reference character 58.
- the left side of this repeated Block A 58 is shown connected to the AGC gain programming D/A converter 38, the local oscillator 28, and to processor 26.
- the right side of this repeated Block A 58 is shown connected to the range gate control 21, and to a second transmit/receive switch 56.
- Figure 4 is a pictorial rendition of two persons carrying handguns.
- a person On the left side of the figure, a person is shown with a gun held in place either in front or in back of a belt.
- a gun On the right side of the figure, another person is shown with a gun carried in a bag or pouch situated on the hip at the person's side.
- Different methods which are described below, are employed to detect objects or weapons that are concealed in various places on the body.
- Figure 5 is a chart which explains a unit of measurement, "dBsm,” that is used to quantify reflected radiation.
- the dBsm is based on a unit of measurement called the decibel, named after Alexander Graham Bell, and is abbreviated "dB.”
- Decibels are used to compare two levels of radiated or reflected power. As an example, if a person listening to a radio is very close to the antenna tower of a radio station, the power level would be very high. If the same person were many miles away from the same antenna tower, the strength of the received radio waves would be much lower because of the increased distance. Decibels could be used to quantify this ratio of power levels as a single number.
- decibels are a logarithmic form of measurement, which is highly useful since they are used to compare very large differences in numbers. Since radiated power levels can vary over such large ranges, a logarithmic scale is used instead of a more common linear scale. Decibels are calculated as follows:
- dB 10 log P x /P Y (1 ) where Px is a first power level, and Py is a second power level.
- dBsm is a measure of the size of the target expressed in decibels and compared to one (1) square meter. Mathematically, dBsm is expressed as:
- A is the area of the target in meters and G is the gain of the target on reflection. This expression assumes that the area is flat relative to the wavelength of operation, and that the area is uniformly illuminated by radio waves. If the side of a square area is "a" in meters, then the area becomes “a 2 " in square meters.
- G or gain
- Figure 6 supplies information concerning a term of measurement called "radar cross section.”
- radar cross section When radio waves are generated and then directed toward an object, some portion of those transmitted waves pass through the object, another portion of those waves are absorbed by the target, and a third portion of the transmitted waves are reflected back toward the transmitter. The larger the portion of reflected waves, the greater the radar cross section of an object. An object that has a relatively large radar cross section is therefore relatively easier to detect, compared to an object that has a smaller radar cross section.
- the magnitude of the measured radar cross section of an object depends largely on its reflectivity, and on the spatial orientation of the object. For example, suppose a radar station on the shoreline is looking for ships at sea nearby.
- the detection is more easily accomplished when the handgun is oriented in a way that presents a relatively larger radar cross section to the detector.
- a gun that is tucked behind a person's belt buckle so that the side of the gun is flat against the waist presents a larger radar cross section than a weapon holstered on the hip with the gun barrel pointing toward the ground and the grip pointing forward or back.
- the data in Figure 6 is the radar cross section of a metal .357 caliber handgun illuminated by electromagnetic radio waves in several frequency bands. These data were established to calibrate the detector equipment and to provide reference measurements.
- Figure 7A provides data regarding the radar cross section (RCS) of a .357 caliber pistol for transmitted radiation spanning the 2650 to 3000 MHz frequency range. The curve shows that for a gun oriented in the broadside position, meaning that the longest dimension of the gun extends sideways in the plane of the transmitted radio wave, the radar cross section (RCS) measured in dBsm varies from about -8 dBsm to -1 1 dBsm over this frequency range.
- Figure 7B represents a body return in the same frequency band as Figure 7A.
- the average radar cross section across the band is -3 dBsm or approximately 8 dB stronger than the average gun return of -11 dB.
- Figures 8 and 9 provide measurements of the reflection of radio waves of a person in the test chamber.
- Figure 8 contains empirical data that indicates that when a person is illuminated with radiation, about 63% of the radio wave energy is reflected back from the body between 2.59 to 3.95 GHz.
- Figure 9 shows that about 32% is reflected back between 7.0 to 10.66 GHz. This information was gathered using radio waves transmitted at the 2.59 to 3.95 and the 7.0 to 10.66 GHz bands.
- Figure 10 exhibits the fundamental mode of operation of one embodiment of the present invention.
- Persons entering a protected space or "Safe ZoneTM” are illuminated with radio waves which are horizontally polarized. A portion of these radio waves are absorbed, while some are reflected back toward the transmitter.
- the transmitter illuminates a person without a gun
- the two similar curves in the upper graph in Figure 10 result. These two curves represent the amplitude of the horizontally polarized energy reflected back to the detector (the upper curve), and the amplitude of the vertically polarized energy reflected to the detector (the lower curve) in the time domain.
- the gap, labeled "Delta A,” between the maximum amplitudes of these two curves is relatively wide compared to the gap between the maximum amplitudes of the two curves in the graph in the lower right portion of Figure 10.
- the lower graph shown in Figure 10 contains two curves produced when a person is carrying a handgun that is sensed by the detector in the time domain.
- the gap between the curves labeled "Delta B,” is substantially narrower than the gap in the upper graph.
- the two curves represent the energy level of horizontally polarized radio waves reflected from the person (the upper curve), and the energy level of vertically polarized radio waves reflected back from the person (the lower curve) in the time domain.
- the component of vertically polarized energy which is reflected back from the object increases.
- the present invention relies on the physical phenomenon of reflection in which an incident beam of horizontal polarization will be partially reflected back as vertical polarization.
- the percentage of energy converted to vertical polarization depends on the shape of the weapon in the plane normal to the direction of incidence. If the weapon has a cross sectional shape which has both vertical and horizontal components, then a vertically polarized component will be realized even though the object is irradiated by horizontal polarization.
- the invention is capable of being implemented using a standard set of stored values that represent the signals which are reflected from persons who are not carrying concealed weapons. This data, which may be measured and compiled using a number of persons, would furnish the information represented in the upper graph shown in Figure 10.
- the detector is capable of adapting to its environment by progressively and continuously learning about the reflected signals that are produced by many persons entering the "Safe ZoneTM" who are not carrying weapons. £ - Laboratory Data
- Figure 11 is a viewgraph that offers test data regarding the detection of a handgun in accordance with the present invention using the 9.5 to 10.6 GHz frequency bands. However, this data is taken with a vertically polarized transmitter, which is not the preferred embodiment.
- This chart shows the received difference between a person carrying a gun and a person without a gun for horizontal polarization only. Data were taken for front, side and back views. Five of the six cases showed positive indication of a gun.
- the body cross section reduces by approximately 6 dB and the now vertically polarized cross polarization reduces a like amount.
- the cross polarization of a gun stays constant. This means that the 1.4 dB difference can now become 7 4 dB, on the average, and even the 3 dB variation in body response is not sufficient to overcome this improvement.
- the preferred embodiment is to transmit horizontal polarization, and to receive both horizontal and vertical polarization.
- Figure 12 supplies actual test data concerning the detection of a handgun at the 2.9 to 3.25 GHz frequency band.
- the incident polarization was horizontal.
- the margin or detection column shows a failure for a particular subject, Rokki, when the gun is viewed from the front.
- the criterion for failure is a margin below 0 dB.
- Figures 13 and 14 are measured time domain test equipment plots of two pairs of waveforms generated during a handgun detection experiment.
- Figures 15, 16 and 17 represent a summary of all measured front, side and back cases, respectively, in the 2.9 to 3.25 GHz band.
- the results from a history of eleven targets are summarized for both the main (horizontal) polarization, and the cross (vertical) polarization. The data are presented for both cases in which a gun is present and in which a gun is absent.
- Figure 15 contains four values of particular interest:
- the present invention uses averages for the main-cross no-gun case, and the cross no-gun case to make the determination whether or not a gun is present. This tends to eliminate the body variance effect which was discussed just previously.
- the following two rules are utilized in a preferred embodiment of the invention to determine the presence of a weapon and to indicate false alarms.
- Figure 16 represents the case where the gun is located on the side of the body, and the side of the body is viewed. This case shows 100% detection of the gun and there is no false alarm rate.
- Figure 17 represents the case where the gun is located on the back of the body, and back of the body is viewed. This figure shows one failure out of 12 but has no false alarm rate.
- Figure 18 shows the results when the system was operated in the 9.5 to 10.6 GHz frequency band.
- Figures 19 and 20 provide relative power versus azimuth angle plots for two 8 by 8 antenna arrays using two different frequency bands.
- Figures 21 and 22 supply operational parameters for the present invention for two different frequency bands and two different size antennas.
- Figures 23 and 24 portray triangular waveforms that may be employed in an alternative embodiment of the invention to generate the required frequency domain waveform for detecting an object in the 2.9 to 3.25 and 9.55 to 10.66 GHz frequency bands.
- one embodiment of the present invention may be used to detect objects by illuminating a target with horizontal polarization, and then receiving both main and cross polarization of said object.
- One of the most difficult issues in the gun detection scheme proposed by these teachings is the variance of the human body. All data shown to date used amplitude input only to convert from the measured frequency domain to the displayed time domain plots. It was reasoned that such variances would result in significant phase deviations across the measurement band for the human body but not for the gun. In a measured instance, using both amplitude and phase information, this proved to reduce the cross polarized signal without a gun by 11.5 dB.
- Such a margin improvement would not only insure that gun detection cases are more easily determined, it would also provide margin for spurious items such as keys, eye glasses, cell phones, etc. This occurs because one can now force Tests B and C to not only be positive but also greater than 6 dB while keeping the remaining margin for Rule A.
- a Complex Fast Fourier Transform can accommodate both amplitude and phase data.
- a Complex Fast Fourier Transform (FFT) Algorithm is employed to improve the sensitivity of detecting objects.
- FFT Fast Fourier Transform
- a Fast Fourier Transform is a mathematical expression that is used to convert information about frequency to information about time.
- Figure 1 A is a graph which plots the intensity or amplitude A of a wave W along the vertical axis Y for an interval of time, which is measured along the horizontal axis X.
- Each wavelength has 360° of phase or 2 ⁇ radians. If one wave is delayed relative to another, a phase difference occurs. For example, if a second wave begins were the first wave is at +A, the second wave is now -90° relative to the first wave.
- the Fast Fourier Transforms which are utilized in a preferred embodiment of the invention are the tools which enable this conversion from the frequency domain to the time domain.
- Complex Fast Fourier Transforms, which are also used to implement a preferred embodiment of the invention, extend the capability of the detection apparatus to account for more complicated information about the radio waves that concern both the "phase" and amplitude of the transmitted and reflected waves.
- Measuring the phase of the polarized waves reflected from a person who may be carrying a concealed weapon is important because the polarized waves reflected from a concealed weapon and the polarized waves reflected from a human body behave quite differently.
- the reflections from a concealed weapon while not constant, vary within a relatively confined range.
- the reflections from a human body are chaotic.
- a preferred embodiment of the invention exploits this generalized phenomena by using signal processing methods to distinguish the relatively well-behaved signals from a concealed weapon from the generally unpredictable signals from a human body.
- the parent Patent Application entitled Object Detection System discloses novel methods and apparatus for detecting concealed weapons.
- the inventions described in the previous Application utilize a time domain method in which the difference between the co- polarized and cross-polarized returns from a target area is used to determine if a weapon is present.
- This earlier method assumes the returns from the target area are of equal phase, and are correlated in time. In reality, they are not.
- the advantage of the Complex FFT approach is that it inco ⁇ orates the phase information into the transformation.
- the result of the uncorrelated data is a reduction in the return from the human body, increasing system sensitivity and the ability of the invention to detect concealed weapons.
- Figure 25 is a plot of phase versus frequency for a .357 caliber pistol, and a sample of the return from a moving human body.
- the cross-pole return comprises signals from a human body and a weapon.
- the Complex FFT approach utilizes the phase information from the cross-pole return in the transform to the time domain. The result is a reduction in the return from the body because of its uncorrelated nature. This effect is seen in Figure 26.
- the return from the .357 weapon correlates, and remains unchanged, as seen in Figure 27. The result is that less cross-pole signal is returned from the human body, improving the ability to detect weapons.
- the present invention inco ⁇ orates the apparatus depicted in Figures 28 or 29 to measure phase of the returned cross-pole signal.
- the phase measurement is performed at the RF signal frequency and at the IF signal frequency in Figure 29.
- a phase discriminator is used to measure the phase of the returned cross-pole signal.
- the waveforms in Figure 30 can be defined as follows:
- a f Amplitude Response of the Cross-pole Return in the frequency domain
- f Frequency in Gigahertz
- the frequency band of interest is broken into segments or bins.
- the number of bins "N” can be practical value, from zero to a number approaching infinity.
- Af ⁇ i(f) is not germane to this illustration, and will be dropped from the expression
- the new expression can be defined as follows
- ⁇ o Reference phase value at center frequency (radians);
- Ao Amplitude Response at the Center Frequency.
- One embodiment of the present invention offers the additional benefits of being lightweight, portable and battery-operated.
- One version of the system may be constructed as a hand-carried unit that could be used by law enforcement officers during traffic stops to determine if the occupant of an automobile is armed.
- the invention may also be inco ⁇ orated into automatic door-opening equipment.
- the invention is not limited to finding weapons.
- the invention may locate distinctly shaped merchandise, or inexpensive tags attached to merchandise as an inventory control and anti-shoplifting system.
Abstract
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP00964880A EP1203359A4 (en) | 1999-05-25 | 2000-05-25 | Signal processsing for object detection system |
IL14673400A IL146734A0 (en) | 1999-05-25 | 2000-05-25 | Signal processing for object detection system |
CA002375435A CA2375435C (en) | 1999-05-25 | 2000-05-25 | Signal processsing for object detection system |
AU75699/00A AU7569900A (en) | 1999-05-25 | 2000-05-25 | Signal processsing for object detection system |
IL146734A IL146734A (en) | 1999-05-25 | 2001-11-25 | Signal processing for object detection system |
IL171814A IL171814A (en) | 1999-05-25 | 2005-11-07 | Object detection method employing polarized radiation |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/318,196 | 1999-05-25 | ||
US09/318,196 US6342696B1 (en) | 1999-05-25 | 1999-05-25 | Object detection method and apparatus employing polarized radiation |
US09/346,857 US6243036B1 (en) | 1999-05-25 | 1999-07-02 | Signal processing for object detection system |
US09/346,857 | 1999-07-02 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2000075892A2 true WO2000075892A2 (en) | 2000-12-14 |
WO2000075892A3 WO2000075892A3 (en) | 2001-03-01 |
Family
ID=26981356
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2000/014509 WO2000075892A2 (en) | 1999-05-25 | 2000-05-25 | Signal processsing for object detection system |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1203359A4 (en) |
AU (1) | AU7569900A (en) |
CA (1) | CA2375435C (en) |
IL (1) | IL146734A0 (en) |
WO (1) | WO2000075892A2 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1709461A2 (en) * | 2003-11-25 | 2006-10-11 | The MacAleese Companies, Inc. D.b.a. Safe Zone Systems | Object detection method and apparatus |
WO2014120289A1 (en) * | 2012-10-10 | 2014-08-07 | Raytheon Company | Detection of concealed object on a body using radio frequency signatures on frequencies and polarizations |
US9182481B2 (en) | 2008-03-18 | 2015-11-10 | Radio Physics Solutions Ltd. | Remote detection and measurement of objects |
US9335407B2 (en) | 2009-09-17 | 2016-05-10 | Radio Physics Solutions Ltd | Detection of objects |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5334981A (en) * | 1992-04-09 | 1994-08-02 | Hughes Missile Systems Company | Airborne metal detecting radar |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA1338522C (en) * | 1988-12-19 | 1996-08-13 | Naresh C. Deo | Millimeter-wave imaging system, particularly for contraband detection |
FR2747790B1 (en) * | 1994-08-30 | 1998-09-11 | Le Centre Thomson D Applic Rad | RADAR FOR DETECTING IMMOBILIZED TARGETS |
US6359582B1 (en) * | 1996-09-18 | 2002-03-19 | The Macaleese Companies, Inc. | Concealed weapons detection system |
WO1999001781A1 (en) * | 1997-07-02 | 1999-01-14 | Ekko Dane Production A/S | Radar plant and measurement technique for determination of the orientation and the depth of buried objects |
-
2000
- 2000-05-25 CA CA002375435A patent/CA2375435C/en not_active Expired - Fee Related
- 2000-05-25 AU AU75699/00A patent/AU7569900A/en not_active Abandoned
- 2000-05-25 IL IL14673400A patent/IL146734A0/en active IP Right Grant
- 2000-05-25 WO PCT/US2000/014509 patent/WO2000075892A2/en active Application Filing
- 2000-05-25 EP EP00964880A patent/EP1203359A4/en not_active Withdrawn
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5334981A (en) * | 1992-04-09 | 1994-08-02 | Hughes Missile Systems Company | Airborne metal detecting radar |
Non-Patent Citations (1)
Title |
---|
See also references of EP1203359A2 * |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1709461A2 (en) * | 2003-11-25 | 2006-10-11 | The MacAleese Companies, Inc. D.b.a. Safe Zone Systems | Object detection method and apparatus |
EP1709461A4 (en) * | 2003-11-25 | 2011-03-16 | Macaleese Companies Inc D B A Safe Zone Systems | Object detection method and apparatus |
US9182481B2 (en) | 2008-03-18 | 2015-11-10 | Radio Physics Solutions Ltd. | Remote detection and measurement of objects |
US9746552B2 (en) | 2008-03-18 | 2017-08-29 | Radio Physics Solutions Ltd. | Remote detection and measurement of objects |
US10466351B2 (en) | 2008-03-18 | 2019-11-05 | Radio Physics Solutions Ltd. | Remote detection and measurement of objects |
US11422252B2 (en) | 2008-03-18 | 2022-08-23 | Radio Physics Solutions Ltd. | Remote detection and measurement of objects |
US9335407B2 (en) | 2009-09-17 | 2016-05-10 | Radio Physics Solutions Ltd | Detection of objects |
US10067226B2 (en) | 2009-09-17 | 2018-09-04 | Radio Physics Solutions, Ltd. | Detection of objects |
WO2014120289A1 (en) * | 2012-10-10 | 2014-08-07 | Raytheon Company | Detection of concealed object on a body using radio frequency signatures on frequencies and polarizations |
US9857462B2 (en) | 2012-10-10 | 2018-01-02 | Raytheon Company | Detection of concealed object on a body using radio frequency signatures on frequencies and polarizations |
US9903948B2 (en) | 2012-10-10 | 2018-02-27 | Raytheon Company | Radar detection of a concealed object on a body |
Also Published As
Publication number | Publication date |
---|---|
WO2000075892A3 (en) | 2001-03-01 |
IL146734A0 (en) | 2002-07-25 |
EP1203359A4 (en) | 2009-11-25 |
CA2375435A1 (en) | 2000-12-14 |
CA2375435C (en) | 2008-12-23 |
EP1203359A2 (en) | 2002-05-08 |
AU7569900A (en) | 2000-12-28 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6243036B1 (en) | Signal processing for object detection system | |
US6856271B1 (en) | Signal processing for object detection system | |
US7167123B2 (en) | Object detection method and apparatus | |
US7450052B2 (en) | Object detection method and apparatus | |
AU2009201597A1 (en) | Object detection method and apparatus | |
US20080284636A1 (en) | Object detection method and apparatus | |
US7492303B1 (en) | Methods and apparatus for detecting threats using radar | |
KR100483897B1 (en) | Concealed weapons detection system | |
IL187322A (en) | Object detection method | |
US9645233B2 (en) | Cavity length determination apparatus | |
US10890656B2 (en) | Weapons detection system using ultra-wide band radar | |
CA2375435C (en) | Signal processsing for object detection system | |
Hausner | Radar-based concealed threat detector | |
MXPA99002585A (en) | Concealed weapons detection system |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AK | Designated states |
Kind code of ref document: A2 Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY CA CH CN CR CU CZ DE DK DM EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT TZ UA UG US UZ VN YU ZA ZW |
|
AL | Designated countries for regional patents |
Kind code of ref document: A2 Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
DFPE | Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101) | ||
AK | Designated states |
Kind code of ref document: A3 Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY CA CH CN CR CU CZ DE DK DM EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT TZ UA UG US UZ VN YU ZA ZW |
|
AL | Designated countries for regional patents |
Kind code of ref document: A3 Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG |
|
ENP | Entry into the national phase |
Ref document number: 2375435 Country of ref document: CA Ref country code: CA Ref document number: 2375435 Kind code of ref document: A Format of ref document f/p: F |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2000964880 Country of ref document: EP |
|
REG | Reference to national code |
Ref country code: DE Ref legal event code: 8642 |
|
WWP | Wipo information: published in national office |
Ref document number: 2000964880 Country of ref document: EP |
|
NENP | Non-entry into the national phase |
Ref country code: JP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 171814 Country of ref document: IL |