JP2716401B2 - Video radar penetrating concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to radar, and more particularly to an image radar for producing radar images of objects located behind opaque structures such as concrete and stucco barriers.

[0002]

2. Description of the Related Art Surveillance of areas restricted from view is of great help to police and military personnel. Police officers need to identify and locate people inside structures such as concrete and plaster. While impulse radar was required to be used in this application, there were a number of problems, such as interference from televisions and other communications transmitters.

An image radar according to the present invention has been developed by the applicant of the present invention and is described in US patent application Ser. No. 08 / 028,451 (March 9, 1993) filed by the present applicant.
) Is an improvement on the idea used in the 3D video radar. Three-dimensional video radar systems use ultra-wideband linear FM millimeter wave radar technology to provide high resolution target information. Three-dimensional imaging radar continuously monitors long-term remote areas and records all surveillance activities completely in video. Three-dimensional video radar uses a dual band radar operating at 56 GHz and 14 GHz. Three-dimensional imaging radar has been shown to penetrate materials such as gypsum (wall) boards, wood, and some types of bricks. However, three-dimensional imaging radar cannot be seen through concrete or stucco structures or barriers. The reason is that concrete material causes excessive loss of the actual image of the object on the other side of the barrier.

In particular, in an attempt to solve the problem of concrete penetration, laboratory tests were carried out using a radar developed by the applicant of the present invention operating in the frequency range from 500 MHz to 2 GHz. . Both linear frequency modulated continuous wave (FMCW) radar and impulse radar were tested. These low-frequency (ultra-wideband) radars have proven that acceptable decibels (db) of a few decibels (db) also occur with conventional reinforced block walls, concrete prefabricated reinforced walls and California stucco materials. These tests have also demonstrated that a distance resolution of about 6 inches can be achieved with portable equipment.

[0005] It is believed that the reduced attenuation at lower frequencies is related to the size of the "aggregate" in concrete with respect to the wavelength of the radar energy. Typical dimensions of concrete gravel are 1/4 at a frequency of 56 GHz.
Greater than the wavelength (0.050 inch). At 1 GHz, the quarter wavelength is 3 inches, and the effect of concrete on waves is significantly less.

[0006] One important limitation at these low frequencies is the size of the antenna beam. A radar operating at 56 GHz can achieve a 0.6 ° pencil beam (two directions) producing a beam of 2 inches dimensions at a distance of 16 feet. The 56 GHz radar antenna is a parabolic dish reflector with a diameter of one foot. 1
The 4 GHz radar uses the same dish antenna and
It has a beam width of 1.5 ° in the direction. 0.6 at 1 GHz
To achieve a beam of °, an antenna with a diameter of 56 feet is required. Since this is not practical at all, different techniques must be used to achieve acceptable angular resolution for radars operating at low frequencies.

[0007]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image radar system for projecting targets located behind opaque structures such as concrete and stucco barriers. It is a further object of the present invention to provide an image radar system for providing a three-dimensional image of a target located behind an opaque structure.

[0008]

SUMMARY OF THE INVENTION The present invention is a concrete penetration imaging radar system for generating a radar image of a target located behind an opaque structure such as a concrete and stucco barrier. The imaging radar system of the present invention provides radar signals that penetrate concrete or plaster walls and the like, and provides images of targets behind them.

The present invention is a video radar system for generating an image of a target located behind an opaque structure.
An antenna comprising a low power frequency modulated continuous wave radar transmitter tunable to a frequency in the range of 600 MHz to 1.3 GHz, a transmitting antenna coupled to the radar transmitter, and three or more receiving antennas. An array, a radar receiver coupled to each receive antenna of the antenna array, a computer processor coupled to the radar receiver, a radar display coupled to the computer processor, an antenna array, a radar transmitter, and a radar receiver. And a power supply coupled to and powering the computer processor, wherein adjacent antennas of the antenna array are spaced apart from each other in a range of 3 to 12 feet from each other; A processor arrives at each receiving antenna for a radar return signal obtained from the target. Configured to process radar return signals using time difference processing to determine a target angle in front of the antenna array from arrival time differences of radar return signals from targets at individual antennas in the antenna array. It is characterized by. As described above, in the present invention, the arrival time difference (TD) in which the radar reflected signal from the target arrives at each receiving antenna using a plurality of receiving antennas.
Processing the radar return signal using OA) processing to determine the angle of the target direction using a physically small and portable antenna, thereby detecting the position of the target with high angular resolution. This is what made it possible.
For example, a normal type radar using a frequency of 56 GHz as described above cannot obtain a good angular resolution, but the radar apparatus of the present invention obtains an angular resolution of 5 ° to 10 ° depending on the antenna interval. be able to.

One embodiment of the imaging radar system of the present invention is shown reduced to perform penetration of reinforced concrete or equivalent thick soil of one foot or more. Video radar systems are lightweight, portable, and robust. The video radar system provides target range and azimuth information. The two video radars are used simultaneously to provide both horizontal and vertical scan information and produce a three-dimensional image display. The radar system of the present invention is not affected by communication interference and provides more information about target identification than conventional video radar.

Laboratory tests of a 1 GHz imaging radar system have shown that the location of a radar system walking 2 to 60 feet opposite a 6 inch reinforced concrete wall and a regular California style stucco wall. Human detection and position determination were performed. Experiments were performed with the radar system placed directly adjacent to the wall and 30 feet away from the wall. In the experiments, experimental prototype hardware was used that operated at an average power of only 5 milliwatts using a 12 dB gain antenna. High power transmitters
It can be used to increase the distance of a video radar system to hundreds of feet or more.

The present invention provides the ability to maintain detection, identification, tracking and monitoring of threat weapon systems and personnel and equipment. The invention finds use in police surveillance, drug crackdown, detection of underground mines, and automotive applications. The radar system provides a target high-resolution image located behind an opaque structure. Radar systems operate in any field of view and operate over a wide range of environments.

The types of sensors used in the radar system of the present invention include a temperature sensor, an acoustic (soner) sensor, and an R sensor.
Includes F-sensors, laser sensors, and other photoelectric sensors, which are generally portable by humans.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS The various features and advantages of the present invention will be readily understood with reference to the following detailed description, taken in conjunction with the accompanying drawings. In the drawings, reference numerals indicate elements having the same structure. FIG. 1 is a schematic diagram illustrating an operation scenario of an image radar system 10 according to the principles of the present invention, that is, a concrete penetration image radar system 10. The image radar system 10 is arranged, for example, on a motor vehicle 11, which is formed, for example, in the form of a folding extension ladder 20 and comprises an antenna array 12 fixed to the top of the motor vehicle 11. A radar signal 13 (indicated by the dashed beam) is emitted from the antenna 12 and penetrates a structure 14 or barrier 14 such as, for example, a concrete wall 14 or a plaster wall 14. The radar signal 13 reflects from a moving target 15, a person 15, or a target 15 located behind a barrier 14. An image of a moving target 15 or person 15 behind the barrier 14 is generated by the radar system 10 and displayed on a radar display 18.

FIGS. 2 and 3 show detailed block diagrams of the video radar system 10, which detail the antenna array, the transmitter, and its signal processor, respectively.
FIG. 2 shows a detailed system block diagram of the video radar system 10, the particularly detailed antenna array 12, and its transmitter 17. The video radar system 10 is, for example, wood,
A motion detection concrete penetrating radar system 10 configured to detect a motion target 15 obscured by a structure 14 or barrier 14 made of conventional structural materials such as plaster and concrete. As shown in FIG. 2, the video radar system 10 is low power,
An ultra-wideband linear frequency modulated continuous wave radar including a frequency tunable continuous wave (CW) transmitter 17, an antenna array 12, a radar receiver 38, a computer processor 19, a power supply 21, and a radar display 18. 16 are provided. As shown in FIG. 1, the antenna array 12 includes an antenna array 12 of a multi-element side-view CW array. The antenna array 12 is described in more detail below with respect to FIGS. The antenna array 12 includes a transmitting antenna 31 and three receiving antennas 32-1, 32-2, and 32-3. Transmit antenna 31 is coupled to transmitter 17 by a power splitter 33 and a power amplifier. Each receiving antenna 32-1, 32-2, 32-3 has a separate receiver 38-1, 38-2, 38-3, each including a preamplifier 35 and a mixer 36.
To a multiplexer 37 having three ports. The output of multiplexer 37 is coupled to computer processor 19.

The low power, frequency tunable continuous wave (CW) transmitter 17 includes a counter 51 coupled to the computer processor 19 and configured to receive a sweep start pulse therefrom. . Counter 51 is coupled to a clock 58 which controls its counting.
The counter 51 is controlled by a voltage controlled oscillator by an error corrector 53.
It has an output coupled to a digital to analog converter 52 coupled to 54. The digital-analog converter 52 is
It is configured to supply a linear sweep signal to the error corrector 53. Power splitter 56 is coupled to voltage controlled oscillator 54 and provides a signal to a slope error detector 57 whose output is coupled to a second input to error corrector 53;
Power splitter 56 is coupled to a low power amplifier 55 that provides the output of transmitter 17. The video radar system 10
It is configured to operate at any frequency from 600 MHz to 1.3 GHz.

The transmitter 17 of the video radar system 10 supplies an ultra-wideband linear frequency modulated continuous wave radar 16. FIG.
FIG. 3 is a graph illustrating a linear frequency modulated continuous wave (CW) radar signal used by the transmitter 17. Linear frequency modulated continuous wave radar 16 has a number of advantages over conventional impulse radar when used on an image target 15 through an opaque structure 14, such as a concrete wall.

The transmitter 17 has a bandwidth of about 60 MHz in the 700 MHz band.
It has an operating frequency range from 0 MHz to 1.3 GHz. This band produces a distance resolution of about 7 inches. The transmitter 17 is controlled by a command from the signal processor 43. The basic output power level of video radar system 10 is 10 milliwatts for short range operation. A high power amplifier 34 is provided to increase the radar power level (17 db) when needed for long range operation.

As shown in FIG. 2, computer processor 19 includes a distance filter and amplifier 41 having an input coupled to the output of multiplexer 37, and an analog-to-analog
It includes a digital (A / D) converter 42, a computer 49, and a digital signal processor 43. One output of computer 49 is coupled to radar display 18 and another
The two outputs are coupled to a transmitter 17.

FIG. 3 is a block diagram of the video radar system 10 showing details of the computer processor 19. Digital signal processor 43 is coupled to the output of analog-to-digital converter 42, which receives the input signal obtained from multiplexer 37. The output of the analog-to-digital converter 42 is coupled to a fast Fourier transform (FFT) processor 44, which provides a fast Fourier transform (FFT) processor 44.
Provides an output signal filtered by a coherent integration filter 45, which is coupled to a detector 46. The post detector integrator 47
It generates a Doppler acoustic output signal and also provides a signal that is provided to a threshold comparator. The output of threshold comparator 48 is coupled to a computer 49, such as an IBM 486 personal computer. Computer 49
Is coupled to a display 18 for displaying radar images generated by the system 10. Software 50 executes on a computer 49 and processes radar signals to generate a radar image.

Video radar system 10 has a 700 MHz bandwidth that produces a 7 inch range resolution.
The output power level of the transmitter 17 required to ensure detection of the person 15 at distances greater than 100 feet is approximately 10
Milliwatts. The actual distance will depend on several factors, including the moisture content of the concrete, the aspect angle, and other targets located at the monitored area. Operational experience has shown that these environmental characteristics sometimes limit the operation of the system. The high power transmitter 17 is used to increase the range performance of the video radar system 10, with a corresponding increase in primary power and weight.

An ultra-wideband, low frequency radar signal that penetrates concrete or such a structure 14 indicates that a target angle determination is to be made. Small, low frequency antennas have a wide beam width and low gain. To achieve the desired 5 ° angular resolution, a multi-element side-view array antenna 12 has been developed for use in the imaging radar system 10. The multi-element side-view array antenna 12 is shown in FIGS. FIG.
5a shows a plan view of the antenna 12, FIG. 5b shows a side view of the antenna 12 of FIG. 5a in a partially folded state, and FIG. 5c shows a side view of the antenna 12 in FIG. 3 shows an end view of the antenna 12 of FIG.

In a particular example, array antenna 12 includes
Depending on the requirements of the system 10, it comprises three to five broadband antenna elements 31,32. One antenna element
The transmission antenna 31 is used for transmitting a radar signal. Remaining antenna elements 32-1,32-2,32-3
Is used to receive the received radar return signal reflected from the target 15 behind the barrier 14. The transmitting and receiving antenna elements 31 and 32 are 3 to 1
Separated from each other by a distance of two feet, they provide the spatial difference required to make a time difference of arrival (TDOA) measurement of the reflected energy. Receiving antenna element 32-1,32-2,32-3
Is adapted to resolve the azimuth ambiguity typically encountered when only two receiving antenna elements are used. The spacer 61 and the antenna elements 31, 32-1, 32-2, 32-3 are
Secured together by a fiberglass support structure 62. The fiberglass support structure 62 electrically insulates and supports each element of the antenna 12.

Each of the four antenna elements 31, 32-1, 32-2, 32-3 is typically a square having a side of 14 inches. Each of the four antenna elements 31, 32 is approximately 1/4
It has a thickness of inches. Four antenna elements 31, 32
Are connected at their ends to form an array 12 such as an extended ladder 20 of about 8 feet long by 15 inches wide.
To form Each antenna element 31, 32 and spacer 61 of the array 12 is folded at its ends, so that the entire array 12 fits within a 14 "x 28" x 6 "suitcase.

The particular configuration of antenna 12 is very dependent on what it is used for. One configuration designed for use by police and the like is shown in FIGS.
The radar system 10 installed in the form of a folding ladder 20 like a normal ladder, as shown in
Having. The transmitting and receiving antenna elements 31, 32 are substantially identical to each other. The antenna elements 31 and 32 are
The collapsible extension ladder is an exponentially tapered radiator that makes up the crosspiece of the ladder 20. They are spaced along a linear support structure 62 having the form of a collapsible extension ladder 20. Antenna element 31, 32-1,32-
2,32-3 are wideband "exponentially tapered" arrays designed to operate optimally at ultra-wideband and low frequencies. Transmitter 17, receiver 38, and power supply 21 are extended ladders.
The twenty support structures 62 are respectively arranged along the longitudinal direction. Ladder 20 is installed on surveillance vehicle 11, and FIG.
The ladder rails with fiberglass supports 62 are folded by folding joints 63, as shown in FIG.

The signal processor 43 has three receiving antennas.
Three signal processor channels (computer 49) for processing the amplified signals from each of 32-1, 32-2, and 32-3.
And software 50 running on a computer memory). The high-speed analog-to-digital converter 42 substantially includes each of the antenna elements 32-1, 3
Convert radar reflection data from 2-2 and 32-3. The digitized data is converted by a fast Fourier transform (FFT) processor 44 into 6 inch distance bins. Digital signal correlation is performed in computer 49 to perform scan-on-receive-only processing and target detection. The azimuth and distance to the projected target are converted to a planar position display (PPI) using a display 18 of a normal personal computer provided in a portable laptop personal computer or the like, for example. Signal processor
Computer 49, including 43 and indicator 18, is located a few hundred feet from antenna array 12.

The digital signal processor 43 is the central part of the radar system 10. All software 50 for controlling the system 10 and processing radar signals is contained within the computer 49. Because the system 10 is driven by software, it is easily changed to a display and processes radar signals obtained from the radar 16. Since the video radar system 10 provides a two-dimensional display of distance and direction, the display 18 is very simple. This makes operation of the radar 16 easier.

To provide a three-dimensional radar image display, two video radar systems 10 are used, one with horizontal resolution and one with vertical resolution, and the output is an integrated single. It is displayed on one display 18. The antennas 12 of each of the two radar systems 10 are arranged orthogonal to one another to provide horizontal and vertical resolution.

Digital signal processor 43 and display 18
Is provided, for example, by an IBM type 486 laptop computer. The resolution of the display 18 is 320
× 200 pixel grid. The data is displayed on the display 18 as an inverted figure. Goal 15 Moving
And / or the fixed target 15 is viewed on a display 18.
Replaying the time history and eliminating clutter facilitates tracking of moving targets 15. A selected portion of the display 18 zooms to enlarge the displayed image, as is done in conventional graphics software. The information of the selected target is stored on a computer disk (not shown) or a hard copy printed on a printer (not shown) for distribution. This was done in the usual way using a computer operating system.

The operation of the video radar system 10 will be described below. A method of combined antenna beamforming, known as "time difference of arrival" (TDOA) processing, is used in system 10 according to the present invention. Using this type of processing method, the radar signal is transmitted from the signal transmitting antenna 31. At least two separate receiving antennas 32-1, 32-2
And receivers 38-1, 38-2 are located within the field of view of the system 10.
Used to receive the energy reflected from 15. The angle of the target 15 with respect to the receiving antennas 32-1 and 32-2 is
It is inferred from the arrival time difference between the separated receiving antennas 32-1 and 32-2.

If the target 15 is directly in front of the receiving antennas 32-1, 32-2, the time it takes for the reflected energy to reach both receiving antennas 32 is exactly the same. If the target 15 is on one side or the other with respect to the center, the energy reaches the other antenna 32-1 before reaching the one antenna 32-2. This difference in time is directly related to the angular offset to the target 15. The distance between the receiving antennas 32-1 and 32-2 and the ability of the computer processor 19 to resolve the TDOA determine the ultimate angular resolution of the system 10. FIG. 6 shows the arrival time difference between signals received by the two receiving antennas 32-1 and 32-2. In FIG. 6, the receiving antenna 32
The relationship between -1,32-2 and the signal arrival angle of the radar reflected signal is shown.

The distance (S) is the distance between the centers of the receiving antennas 32-1 and 32-2. The velocity (C) of the radar wave is
0.984e9 feet / sec. The time difference is related to the angle offset (B) as follows.

TDOA = S / c · sin (B) The magnitude of S is expressed in feet, where c is about 1 foot per nanosecond and the difference in arrival distances (RDO)
A) is equal to TDOA, and TDOA is expressed as:

TDOA = S · sin (B) ns = RDOA (feet) (approximate) In order to process a large number of targets, each receiver has sufficient range resolution to reflect all reflective surfaces in the field of view. You have to “separate”. In UHF radar, the range resolution is about 0.5 feet. If one of the antennas is spaced 10 feet from another along a line perpendicular to the line of reception, the angular resolution (B) is:

B = sin ^-1 (0.5 / 10) = 2.9 ° (approximate) This shows two small targets at a distance of at least one foot and an angle of at least 2.9 °. It can be separated on the vessel.

Hereinafter, TDOA angle scanning in reception will be described. In FIG. 7, receiver distance cells for the first and second antennas 32-1, 32-2 are shown, where the same target (T1) 15 is a different distance cell for TDOA. It is shown that there is. The signal received from the first receiving antenna 32-1 is processed in the first receiver 38-1. Targets 15 are detected and their amplitude values are placed in distance bins. At the same time, the same processing is achieved at the second receiver 38-2 of the second antenna 32-2. If only a single target 15 is present, the angle to the target 15 will be the difference in the number of range cells between the first and second antennas 32-1, 32-2 as shown in FIG. Determined by counting. This difference is TDOA. In this example, the distance cells are 6 inches apart,
If the two receiving antennas 32-1 and 32-2 are four feet apart, the true azimuth (B) for target 15 corresponding to a one foot difference in distance is:

B = sin ⁻¹ ( ^１ ／) = 14.5 ° This indicates that the target 15 appears closer to the second receiving antenna 32-2 than to the first receiving antenna 32-1. I have. If the target 15 is in the distance cell 8 of the first receiving antenna 32-1, the angle is + 29 °. If the target 15 from the second receiving antenna 32-1 is located in the distance cell 5 (different cell by one) instead of the distance cell 4 by TDOA, the target 15
Is 7.2 °. There is uncertainty about where the target 15 is actually in the antenna beam, which is normal for any directional antenna. T
Using the DOA process, the ambiguity of the location of target 15 is related to the size of the distance cell, which is ± 3.6 ° for an angle of 14.5 °.

The distance between each distance cell is determined by the receiving antenna 32
The line perpendicular to the -1,32-2 plane correlates to a specific azimuth line. As shown in the example above, the difference of ± 1 range cells represents the target 15 on the azimuth line offset ± 7.2 ° with respect to the line perpendicular to the antennas 32-1 and 32-2. I have. Target 15, a ± 2 distance cell, is on the ± 14.5 ° line. The angular spacing is proportional to ± 30 ° scan, ±
Spreads rapidly over 60 °. Table I below shows the relationship between the distance resolution for each distance cell and the distance between the antennas 32 corresponding thereto. The difference in arrival distance in feet and the spacing of the antennas relative thereto gives the scanning angle of the antenna in (±) degrees. It also provides a "scan-on-receive" system according to the invention described below.
Shows a beam pointing angle of 10. Table I shows the linear, one-way angle effect. The two-way effect is more complicated,
Software 50 by the appropriate programming of those skilled in the art
Is easily compensated for.

Table I Distance cell difference 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 (feet) Antenna separation (feet) 1 30.0 90.0------2 14.5 30.0 48.6 90.0----39.6 19.5 30.0 41.8 56.4 90.0--4 7.2 14.5 22.0 30.0 38.7 48.6 61.0 90.0 5 5.7 11.5 17.5 23.6 30.0 36.9 44.4 53.1 6 4.8 9.6 14.5 19.5 24.6 30.0 35.7 41.8 7 4.1 8.2 12.4 16.6 20.9 25.4 30.0 34.8 8 3.6 7.2 10.8 14.5 18.2 22.0 25.9 30.0 9 3.2 6.4 9.6 12.8 16.1 19.5 22.9 26.4 10 2.9 5.7 8.6 11.5 14.5 17.5 20.5 23.6 Below, the time-shift angle scan is described with reference to FIG.
To detect a target 15 directly in front of the radar system 10, each distance cell from the first receiver 38-1 is stored in the second receiver 38-2 stored in the second memory 72. Are multiplied by the corresponding distance cell and stored in the first memory 71. The output is that the target 15 to be reflected has two receiving antennas 32-
Only occurs if it is directly perpendicular to the front of 1,32-2.
This is true at near vertical angles, where the RDOA of target 15 is less than 6 inches. RD
When OA increases, the target in the second receiver 38-2
15 are in different distance cells (ie 4 to 6).

Referring to FIG. 8, the distance cells at the second receiver 38-2 are shifted in time and then multiplied (X) in software by the distance cells from the first receiver 38-1. The angle offset depends directly on the time offset between the memories 71 and 72 of the two distance cells. In FIG. 8, the distance cell of the second receiver 38-2 is:
Shifted to two distance cells in time. This shift is due to the distance cell being 6 inches and the antenna spacing being 4 inches.
If feet, 14. for all goals 15.
It is proportional to the scan angle shift of 5 °.

This process of shifting the second memory 72 to one distance cell and evaluating the target 15 at the corresponding angle is performed for each set of distance cells until the number of distance cells is equal to the discrete distance of the antenna. Will continue. Thereafter, the process is repeated, shifting the second set of distance cells in the negative time direction to evaluate all targets 15 on the opposite side of the antenna array 12 centerline. The true distance to target 15 is determined by the total distance shift, as shown by the output 73 resulting from the multiplication (distance cell differences differ by １ ／).

Using the data in Table I, the antennas 32-1,3
The two-four-foot spacing between 2-2 and the 0.5-foot distance cell spacing shall be 8 ± 90 ° on each side with respect to the center
Direction scan line. It is also shown that as the distance between the antennas 32-1 and 32-2 increases, the number of scan lines that can be used increases. There is a compromise between antenna spacing and the number (or resolution) of scan lines on the display 18 for it.

This simple TDOA approach works well for a single target 15, but only two receive antennas 32
One or more targets 15 within the antenna beamwidth of -1,32-2 will cause ambiguity. With two targets 15, there are four possible solutions for the position of the target 15. In order to solve this problem, three receiving antennas 32-
1,32-2,32-3 are required. Reducing the degree of angular resolution and ambiguity is achieved for each receiving antenna 32-1, 32-2, 32
It is a function of the interval between -3. This interval correction is made by the system 10 according to the invention so that the system operates optimally. As an additional mode of processing, only athletic target data is used by the correlation process in computer 49 to provide an enhanced target display.

In operation, referring again to FIGS. 3 and 4, the voltage controlled oscillator (VCO) 54 operates from 600 MHz to 1 MHz.
Operates in high resolution mode at 300 MHz. This VCO
54 is arranged at the same position as the low power amplifier 55. A coaxial cable is used to interconnect the low power amplifier 55 and the antenna array 12. The power splitter 33 and the power amplifier 34 are installed directly on the transmitting antenna 31. Power splitter 33 provides three additional outputs that provide a local oscillator signal to each of three receiver mixers 36.
One low noise preamplifier 35 and mixer 36 are connected to each receiver.
Included within 38.

The output of each mixer 36 is a three-port multiplexer 37 that switches between receivers 38 in a continuous linear FM sweep of radar 16 (it is located at one of the receiver antennas 32). Supplied to The multiplexed output is filtered and amplified before being provided to the analog-to-digital converter 42.

FIG. 9 shows three receiving antennas 32-1, 32-2, and 32.
-3 indicates the arrival time difference of the received signal.
More than two antennas 32 are used to resolve ambiguity. The processing of the angle of the received arrival data is performed as described above, but the antennas 32-1, 32-2, and 32-2, 32-
3 and 32-1, 32-3.
Processing of the radar signal reduces ambiguity and provides for detection of extended targets, such as long walls.

A new and improved imaging radar system has been described herein for generating a radar image of a target located behind an opaque barrier, such as concrete or plaster. It should be understood that the above-described embodiments are some of many specific embodiments that represent applications of the principles of the present invention. Obviously, many alternative arrangements can be readily implemented by those skilled in the art without departing from the scope of the invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an operation scenario using a video radar system according to the principles of the present invention.

FIG. 2 is a detailed block diagram of the video radar system of the present invention showing the antenna array and the transmitter in detail.

FIG. 3 is a detailed block diagram of the video radar system of the present invention showing the signal processor in detail.

FIG. 4 is a graph showing a linear frequency modulated continuous wave (CW) radar signal used in the video radar system of FIGS.

5 is a plan view of an antenna used in the video radar system of FIG. 1, a side view of the antenna in a partially folded state, and an end view of the antenna.

FIG. 6 is an explanatory diagram of an arrival time difference between signals received by two receiving antennas.

FIG. 7 is an explanatory diagram of a shift of a distance cell of the receiver.

FIG. 8 is an explanatory diagram of angle scanning based on an arrival time difference.

FIG. 9 is an explanatory diagram of an arrival time difference between signals received by three receiving antennas.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-220481 (JP, A) JP-A-2-129577 (JP, A) JP-A-7-50610 (JP, A) JP-A-3-320 58504 (JP, A)

Claims (12)

(57) [Claims] 1. A video radar system for producing an image of a target located behind an opaque structure , tunable to a frequency in the range of 600 MHz to 1.3 GHz.
A low power frequency modulated continuous wave radar transmitter, a transmitting antenna coupled to the radar transmitter , and three or more
An antenna array and a reception antenna of the above, the radar receiver coupled to the receiving antennas of the antenna array, and a computer processor coupled to the radar receiver, radar display coupled to the computer processor vessel and said antenna array, said radar transmitter, the radar receiver, and coupled to the computer processor,
Them; and a power supply for supplying power, each antenna adjacent the antenna array distance between each other
At a distance of 3 to 12 feet apart
Is location, the computer processor is obtained from the target rate
Arrival time difference processing of the reflected signal arriving at each receiving antenna
Process the radar reflected signal using the antenna array
The angle of the target in front of b in the antenna array
Arrival of radar return signals from targets at individual antennas
It is configured to be determined from the arrival time difference
Imaging radar system that. 2. The antenna array according to claim 1, wherein said antenna array is a folding type .
2. The radar system according to claim 1, wherein the radar system is formed in the shape of a gouge. 3. The antenna array transmits and receives on one surface.
2. The radar system according to claim 1, comprising a plurality of antennas serving as surfaces . 4. The receiver according to claim 1, wherein the receiver comprises a plurality of independent receivers each coupled to an individual receiving antenna, wherein each independent receiver includes a preamplifier and a mixer. Radar system. 5. The radar system according to claim 1, further comprising a multiplexer having three ports coupled between each mixer and the computer processor. 6. A transmitter coupled to the computer processor for receiving a sweep start pulse therefrom; a clock coupled to the counter for controlling its counting; and a clock coupled to the counter for providing a linear sweep output signal. A digital to analog converter, an error corrector coupled to the digital to analog converter, a voltage controlled oscillator coupled to the error corrector, a power splitter coupled to the voltage controlled oscillator, and coupled to the error corrector The radar system of claim 1, comprising: a slope error detector configured; and a low power amplifier coupled to a power splitter providing a transmitter output. 7. A computer processor, comprising: a distance filter and an amplifier coupled to the multiplexer; an analog to digital converter coupled to the distance filter and amplifier; a computer coupled to the analog to digital converter; The radar system according to claim 1, further comprising a digital signal processor. 8. The computer processor according to claim 1, wherein the computer processor is a digital processor.
Comprising a signal processor, the digital signal processor, coherent integration filter and the fast Fourier transform processor for supplying a filtered output signal, filtering the output signal supplied therefrom is coupled to the fast Fourier transform processor A detector coupled to the coherent integration filter; a post-detector integrator coupled to the detector to generate a micro-Doppler acoustic output signal; a detector coupled to the post-detector integrator and the computer. 2. The radar system according to claim 1, comprising a threshold comparator and software for causing a computer to process the radar signal and generate a radar image. 9. The apparatus according to claim 1, further comprising: a plurality of spacers separating each antenna; a plurality of spacers; and a support structure coupled to the plurality of antennas to electrically insulate and support them. 2. The radar system according to 1. 10. The radar system according to claim 1, wherein each antenna in the antenna array is square. 11. The radar system according to claim 9, wherein the antenna array further comprises a plurality of joints that allow the array to be folded. 12. The radar system according to claim 9, wherein the transmitter, the receiver, and the power supply are arranged along a longitudinal direction of the support structure.