GB2149992A - Radar device - Google Patents
Radar device Download PDFInfo
- Publication number
- GB2149992A GB2149992A GB08426545A GB8426545A GB2149992A GB 2149992 A GB2149992 A GB 2149992A GB 08426545 A GB08426545 A GB 08426545A GB 8426545 A GB8426545 A GB 8426545A GB 2149992 A GB2149992 A GB 2149992A
- Authority
- GB
- United Kingdom
- Prior art keywords
- pulse
- pulses
- controller
- frequency
- mixer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
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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
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
- G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
- G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
-
- 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
-
- 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
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/0209—Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
-
- 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
- G01S13/885—Radar or analogous systems specially adapted for specific applications for ground probing
Landscapes
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
A geophysical radar system comprising a transmitter, a receiver and a display unit, all controlled and synchronized by a controller, the system producing long, high powered, coherent pulses each with a large swept bandwidth with a high frequency which is at least five times the low frequency, the pulses being sent by the transmitter into a medium and used by the transmitter to generate a digital reference signal, and the long reflected pulses being detected by the receiver and used to generate a digital reflected pulse signal which the controller cross-correlates over a series of times with the reference signal to produce a recording of the medium, the system having high resolution, considerable detection range, and the ability to operate in real time.
Description
SPECIFICATION
Radar device
Field of the Invention
This invention relates to a geophysical radar system for determining the general character of various extended media such as earth, water, or snow and ice, and for detecting specific targets therein.
Background of the Invention
Geophysical radar systems are well known in the art, and they are generally used for mapping various strata as well as for locating underground objects such as utility lines, pipelines, tunnels, or certain mineral deposits.
The most common of these prior art systems are short pulse systems. The usual short pulse system generates a series of pulses of very short duration, each of which contains a fairly broad spectrum of high frequencies. The pulses are directed into the extended medium to be examined, and portions of the pulses are reflected from any electrial discontinuity (e.g., boundary layers, pipelines). The short pulse systems have good resolution because reflections from different, closely-spaced discontinuities do not overlap as they return to the detection part of the system, and thus they can easily be distinguished from each other.
Similarly, a reflection from a nearby discontinuity will not overlap with the transmitted pulse itself, and it too can easily be detected.
The principal drawback of a short pulse system is that its effective detection range is limited. This is because in order to generate the short duration pulses, very rapid transistor switches must be used. Such transistors cannot handle a great deal of voltage, and the voltage amplitude of each pulse is low, which in turn limits the overall power carried by each pulse (the power being a function of the "area" of the pulse--its small voltage amplitude times its very short duration). Since the extended media through which the pulses travel tend to absorb energy, the low power, short pulses dissipate before they can reach and return from distant discontinuities.
The other type of geophysical radar system used in the prior art involves long pulse or continuous wave transmission, and this sytem is often called a synthetic pulse system. The synthetic pulse has much more power than the short duration pulse and can reach and reflect from distant discontinuities. However, because of the relatively long transmission time for the synthetic pulses, the system's resolution is poor as reflections from two or more closely-spaced discontinuities tend to mix together as part of a single reflection, and nearby discontinuities cannot be detected because their reflections will mix with the pulse still being transmitted. Furthermore, some of these synthetic pulse systems not only require complex equipment, but also require an inordinate amount of time to make measurements.
Summary of the Invention
We have discovered a geophysical radar system which has both good resolution and range and operates in real time. The system generates a series of long, high-powered coherent pulses, all with a very wide frequency bandwidth. The pulses are transmitted into an extended medium, and a number of reflected pulses, each of which may actually contain information from multiple interfaces and targets at different ranges (including those nearby), are detected, converted to a single digital signal and cross-correlated with a reference signal to reproduce the various interface or target information, thereby providing not only an extended detection range but also superior resolution.At the same time, since the transmitted pulses are all coherent, starting and ending at the same frequency and phase, information about the nature of various detected targets (e.g., metal as opposed to non-metal pipes) can also be determined, as some types of discontinuities cause different phase and amplitude changes in the reflected signals.
In the preferred embodiment, the system generally comprises a transmitter, a receiver and a display unit, all synchronously controlled by a controller. The transmitter generates coherent RF pulses at a pre-selected interval, each pulse having a coded frequency sweep such that the highest frequency is at least five times the lowest. The transmitter sends the resulting long pulses into the medium and also sends a single digital replica of a long pulse to the controller as a crosscorrelation reference signal. The receiver detects the reflected portions of the pulses and converts a number of them into a digital signal, which the controller then cross-correlates with the reference signal from the transmitter. The multiple target or interface information from the reflected pulses is then sent to the display unit for real-time display.
Description of the Preferred Embodiment
We turn to the structure and operation of the preferred embodiment, after first briefly describing the drawings.
Drawings
Figure 1 is a block diagram of a geophysical radar system of this invention;
Figure 2 is a block diagram of the frequency generator of the transmitter circuit of this invention;
Figure 3 is a block diagram of the controller circuit of this invention; and
Figure 4 is a block diagram of the display circuit of this invention.
Sturcture
Referring to Figure 1, the radar system of this invention is shown at 10. The system generally comprises a transmitter 30, a receiver 80, a display unit 1 00, and a controller 20, the latter synchronizing the operation of the other three elements.
As shown in Figure 1, the transmitter 30 includes a ramp generator 32, the input of which is connected to the controller 20 by start signal line 34. The output of the ramp generator 32 is connected by line 35 to a frequency generator 36. As shown in more detail in Figure 2, frequency generator 36 has a microwave voltage controlled oscillator 38 which receives the output signal on line 35 from ramp generator 32 as well as an idle frequency control signal on line 40 from the controller 20. The output of oscillator 38 is fed to a microwave mixer 92, which also receives from another oscillator 49 a fixed output signal having a frequency of 4.5 GHz.
The oscillators 38 and 44 may be Model No.
V82T-3 from Magnum Microwave Corp. of
Sunnyvale, California. The mixer 42 may be
Model No. M044M from the same company.
The output of the mixer 42 for the frequency generator is fed to an amplifier 46, the output of which is connected to a power divider 48. One output of the power divider 48 is connected to a prescaler 50, which in turn is connected back to the controller 20 by clock line 52. The other output from the power divider is on line 54, and it is the working output of the frequency generator 36-. Amplifier 46 and power divider 48 are
Model Nos. AM131 and DS-1 09, respectively, from the Adams-Russell Co. of Waltham, Massachusetts.
Referring back to Figure 1, the working output of the frequency generator 36 on line 54 is connected to an RF switch 56, which is also connected to the controller 20 by start signal line 34. The RF switch may be two cascaded switches, Model No. SS-92 of the
Vani-L Company, Inc. of Denver, Colorado.
The output of RF switch 56 is connected to power divider 58, which is of the same type as power divider 48 of the frequency generator 36. One output of power divider 58 is fed to a linear power amplifier 60. The linear power amplifier 60 is connected to a shielded broadband antenna 62 configured for transmission of pulses into the particular medium to be investigated. The other output of power divider 58 is connected to a mixer circuit 64.
Mixer circuit 64 also receives a strobe input signal on line 66 from pulse generator 68.
Pulse generator 68 and an A to D converter 70 both are connected by line 72 to the controller 20, and an output line 74 from the mixer circuit 64 is connected to the converter 70. A reference signal output line 76 from the converter 70 is connected back to the controller 20.
As shown in Figure 1, receiver 80 has a shielded broadband antenna 82, which is similar to the transmitter antenna 62, for detecting pulses or portions of pulses reflected from discontinuities in the medium to be examined.
The receive antenna 82 is connected to RF amplifier 84, which is similar to the amplifier of the transmitter 30, and it is actually a series of three cascaded amplifiers having an overall gain of 40 to 60 dB. In the preferred embodiment, the gain control of two of the amplifiers is connected to gain controller 86, which is also connected to and activated by the start signal line 34 from the controller 20.
The output of the RF amplifier 84 is connected to a directional coupler 88, which is
Model No. CH-134 from the Adams-Russell
Co. The two outputs of the directional coupler 88 are connected back to the gain controller 86 and to a mixer circuit 90, respectively.
The output of the mixer circuit 90 is fed to an A to D converter 92, the output of which is connected to the controller 20 by line 96. The
A to D converter is also connected to line 72 from the contronler 20, which line 72 is also connected to a pulse generator 94. The pulse generator 94 provides a strobe to the mixer circuit 90. The A to D converter 92, the pulse generator 94 and the mixer circuit 90 are of the same type as those of the transmitter circuit 30.
The controller 20 is best shown in Figure 3.
Controller 20 has a digital timing control circuit 104, which receives the input line 96 from the receiver circuit 80 and the input lines 52 and 76 from the transmitter circuit 30. In addition, timing control circuit 104 is the source of the controller output lines 34, 40 and 72. Timing control circuit 104 receives a clock on line 11 2 from processor controller 108. Processor controller 108 contains a 5.185 MHz master clock and a high speed multiplier/accumulator 111, which may be a Model No. ADSP-1010 from Analog
Devices. Line 11 2 is also connected to memory 106, an input memory 107 of which is connected to timing control circuit 104 by lines 109 and an output memory 11 3 of which is connected to the multiplier/accumulator 111 by lines 115.
Display controller 110 is connected by lines 114, 116 to process controller 108 and the multiplier/accumulator 111. respectively. Line t14 is also connected to the timing control circuit 104. Output line 116 along with line 11 8 from the multiplier/accumulator 111 comprise the output of the controller 20 to the visual display 100. Basic programmable array logic is used instead of a microprocessor for increased speed and because of the nature of the timing cycles.
As shown in Figure 4, display TOO has an analog processor 122 which receives the output lines 116 and 118 from the controller 20.
The output of analog processor 1 22 is connected to a graphic display 124, which in turn is connected by line 1 20 back to the display controller 110 of controller 20. Control switches 126, 1 28 are connected to the analog processor 122, while switches 130, 1 32 are connected by lines 134, 1 36 to the display controller 110.
Operation
To start a recording sequence, the graphic display 1 24 of the display 100 sends a zero pulse or start-of-scan signal on line 1 20 to the display controller 11 0. This start-of-scan signal corresponds to the position of a recording stylus for the graphic display 1 24 which is something like a chart recorder. In the preferred embodiment, the proper start-of-scan signal means that the stylus is ready to begin a new scan across the chart.
When the display controller 110 receives the proper start-of-scan signal from the display 100, the display controller 110 sends a "start" signal on line 114 to the timing controller circuit 104 and the processor controller 108. The timing controller 104 also receives a clock signal on line 11 2 from the process controller 108, and in the preferred embodiment, the clock frequency is 61 KHz, which is obtained by dividing down an internal 5.185 MHz frequency master clock of the processor controller. Different clock freguencies can be used. It is this 61 KHz clock signal that becomes the repetition rate for producing the transmitted pulses to be ser.t to the medium.
With the proper start signal from the display controller 110, the timing controller 104 simultaneously strobes both the transmitter 30 and the receiver 80 with a control signal on line 34, which means that the transmitter and receiver are in synchronous operation.
This control signal repeates at a 61 KHz rate.
For each individual strobing or control signal, the operation of the transmitter 30 is as follows. With reference to Figure 1, the control signal is received by the ramp generator 32, and the ramp generator sends out an increasing rampshaped signal on line 35. This ramp signal starts the frequency sweep of the frequency generator 36 and controls the rate of change of the Sweep. Further, the timing of the control signal on line 34 starting the ramp signal is such that the frequency generator 36 starts and stops changing frequencies at the same frequency and the same phase each time.
With reference to Figure 2, the ramp signal is actually fed to the microwave oscillator 38, which starts it sweeping from 4.45 GHz to 4
GHz in one microsecond. When the ramp signal is received, the swept frequency output goes to the microwave mixer 42, which also receives a 4.5 GHz signal from Oscillator 44.
The resulting output from the mixer 42 consists primarily of a swept frequency signal decreasing from 500 MHz to 50 MHz. This frequency sweep, where the higher frequency is ten times the lower, is preferable in order to obtain an ultra-wideband pulse. The sweep, however, need not be as great as that of the preferred embodiment. Instead the higher frequency could be at least five times the lower one. This sweep from the high frequency to the low should be made in a smooth continuous manner, although the sweep need not be linear. This gives the signal a certain coding.
Also it is possible to sweep from a low frequency to a higher one. The resulting swept signal is amplified by amplifier 46 and fed to the power divider 48, which sends it to the prescaler 50 and to line 54, which is actually the swept frequency output of the frequency generator.
This swept frequency output from the frequency generator 36 is sent to the RF switch 56, which is also strobed by the same control signal on line 34 which starts the ramp generator 32. The purpose of switch 56, which allows for up to 80 dB of isolation, is to remove an idle signal which accompanies the actual swept frequency signal from the frequency generator 36. The idle frequency of 500 MHz appears because of the idle frequency control signal on line 40 from the controller 20 to the oscillator 38 of frequency generator in order to maintain the frequency generator 36 at the proper frequency at all times, even when no ramp signal is received.
(Although it comes from the timing controller 104, this 500 MHz idle signal is actually a function of the digital clock signal of 1.85
MHz on line 54 from the prescaler 50 of the frequency generator 36.) The 500 MHz idle signal thus accompanies the swept frequency signal from the frequency generator 36 until it is removed by the RF switch 56, leaving the swept frequency output pulse which goes to the power divider.
The swept frequency pulse goes through the power divider to the linear amplifier 60 and to the transmit antenna 62. In the preferred embodiment, this long, broadbanded pulse has about 1000 times the measured power of the transmitted pulse of a short pulse system, and the antenna directs this pulse into the medium. The transmitted pulses are each about 1000 nanoseconds in duration.
In addition to generating the pulses for transmission into the medium, the transmitter 30 also generates a reference signal which is a replica of those pulses, and this reference signal is used by the controller to recover the return signal information by cross-correlation techniques. This reference signal is generated by sending the basic swept frequency pulses from the power divider 58 to the mixer 64 of the transmitter. The mixer also receives a very narrow sampling pulse on line 66 from the pulse generator 68 which is strobed at the same time (and at the same 61 KHz rate as the ramp generator 32) by a sample control pulse on line 72 from the controller 20. In the preferred embodiment. this sample and hold operation converts 2000 transmit pulses down to a single replica of a transmit pulse with a frequency sweep from 6000 Hz to 600
Hz.This frequency reduction is made to allow the RF signal to be converted to a digital one.
This replica pulse is sent to the A to D converter 70, where is is converted to a digital signal. The A to D converter 70 is strobed at the same time as the pulse generator 68. The resulting reference signal is fed back on line 76 to the controller 20 where it is stored in the input portion 107 of memory 106.
Continuing with the operation of the circuit 10, we turn now to the receiver 80. The reflected pulses are detected by the receive antenna 82 and sent to the RF amplifier 84.
In the preferred embodiment, the gains of at least two stages of the amplifier 84 are controlled automatically by the gain controller 86, which is activated by the same 61 KHz control signal on line 34 which triggers the ramp generator 32 and the RF switch 56 of the transmitter 30. This means that any gain change occurs only during the period when the transmit pulse is being generated and transmitted into the medium.
The 2000 amplified receive pulses are then converted into a single digital one. The amplified receive pulses are first sent from the amplifier 84 through the coupler 88 to the combination of the mixer 90, the pulse generator 94, and the A to D converter 92 of the receiver 80. This combination processes the pulses exactly as the basic swept frequency transmit pulses were processed by the transmitter 30 to make the reference signal.
The mixer 90 converts the reflected pulses down to a single swept range of 6000 Hz to 600 Hz, which is then converted into a digital signal by the A to D converter 92 and sent back to the controller on line 96. This combination is strobed by the same signal on line 72 that triggers the corresponding parts of the transmitter 30. As with the reference signal, the corresponding digital receive signal is sent to the input half 107 of the memory 106.
This process repeats (at the 61 KHz rate) until the memory 107 is full of reflected pulses and their corresponding reference signals. The memory 107 fills in about 98.6 milliseconds, and when full, the stored signals are sent to the multiplier/ accumulator 111 for compression and cross-correlation.
Cross-correlation is really a comparison (by multiplication and addition) of each digital replica reference pulse with its corresponding digital replica reflected pulse over a range of delay times. A given digital refeiected pulse and its reference signal are multiplied together for a given position of the stylus of the graphic display. The position of the stylus is a function of an offset signal on line 116, which offset signal has values of between 0 and 2000 in the preferred embodiment (although this number could be changed), each depending upon stylus location on the chart. The decoding or cross-correlation for a given offset signal results in a single digital pixel being calculated (in about 200 microseconds). The pixel represents reflected information from a single transmit pulse at a specific depth of the medium.Thus, even though a single reflected pulse is long and contains overlapping information, the information can be extracted in this pulse compression manner.
After conversion to analog, the pixel is sent on line 11 8 to the display 100 where it makes up a portion of the scan of the stylus.
The offset signal is then incremented, and a new pixel is calculated while the past pixel is being displayed. Generally, up to 2000 pixels are contained in a single scan (although this can be varied), and when the scan is complete. the process is repeated (with a moved antenna) With a moving antenna a continuous profile of subsurface conditions is presented. Also, the phase and amplitude of the portion of the reflection from a target can be specifically examined to determine the nature of the target.
Referring to Figure 4, the pixels are amplified before actual display by the analog processor 1 22. The amount of amplification is a direct function of increasing range into the medium in order to compensate for attenuation. The amount of this variable gain is determined by the operator through switch 1 28. Processor 1 22 also can average several scans together (the number of which averaged depends upon the setting of switch 126) to enhance the recording by increasing the signal-to-noise ratio.
The operator also selects the amount of time for each scan (100 milliseconds to 1 second) by switch 1 30 to one display controller 110, and the maximum range time for processing and displaying reflections (50 to 2000 nanoseconds) by switch 1 32. The scan itself can also be set to include fewer pixels.
Other variations will be apparent to those skilled in the art,
What is claimed is:
Claims (9)
1. A geographical radar system comprising:
a transmitter means for periodically generating a series of long, high powered, transmit pulses, each having a broad bandwidth,
antenna means for directing each transmit pulse into a medium to be examined,
a receiving means for detecting the reflected portion of each transmit pulse from the medium, and producing a reflected pulse therefrom, and
a controller having means which cross-correlates, for a variety of times representative of ranges into the medium, each reflected pulse from said receiver with a reference signal, thereby compressing the pulses and producing for each time a discrete information bit for display on a visual display means.
2. The system of claim 1 wherein said transmitter means includes a frequency generator, said frequency generator producing each transmit pulse by sweeping from a high frequency to a low frequency in a coded sequence, which high frequency is at least five times the low frequency.
3. The system of claim 1 wherein said transmitter means includes a reference pulse circuit, said circuit receiving a number of the transmit pulses and converting them to a single digital replica of a transmit pulse, which replica pulse is sent to said controller as the reference signal.
4. The system of claim 3 wherein said transmitter means and said reference pulse circuit are both triggered by control signals from said controller.
5. The system of claim 3 wherein said reference pulse circuit includes a mixer which receives the transmit pulses, which are of RF frequency range, a pulse generator which strobes said mixer. with narrow pulses so as to produce a single pulse with a reduced frequency range at an output of said mixer, and an A to D converter which converts the reduced frequency output of said mixer to a single digital pulse, the digital pulse being the reference signal.
6. The system of claim 1 wherein said controller periodically sends a trigger signal to said frequency generator to produce the transmit pulses, the trigger signal being timed so that the transmit pulses are coherent, beginning and ending at the same frequency and phase.
7. The system of claim 1 wherein said receiving means comprises a reflected pulse circuit, said circuit including a mixer which receives the actual reflected pulses, a pulse generator which strobes said mixer with narrow pulses so as to produce a single pulse with a reduced frequency range at an output of said mixer, and an A to D converter which converts the reduced frequency output of said mixer into a single digital pulse, the digital pulse being the reflected pulse for cross-correlation.
8. The system of claim 1 wherein said transmitter means has a reference pulse circuit and said receiving means has a reflected pulse circuit, both said circuits being selectively activated by the same signal from said controller.
9. The system of claim 1 wherein said controller comprises a multiplier/accumulator which cross-correlates the reference signal with the corresponding reflected signals for different positions corresponding to depth of the medium.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US54335183A | 1983-10-19 | 1983-10-19 |
Publications (2)
Publication Number | Publication Date |
---|---|
GB8426545D0 GB8426545D0 (en) | 1984-11-28 |
GB2149992A true GB2149992A (en) | 1985-06-19 |
Family
ID=24167639
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08426545A Withdrawn GB2149992A (en) | 1983-10-19 | 1984-10-19 | Radar device |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2149992A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2000022455A1 (en) * | 1998-10-12 | 2000-04-20 | Marconi Electronic Systems Limited | System for detection of objects in the ground |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20180092134A (en) * | 2017-02-08 | 2018-08-17 | 주식회사 만도 | A radar having a structure capable of suppressing low-frequency noise |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2030414A (en) * | 1978-07-31 | 1980-04-02 | Prakla Seismos Gmbh | Method for monitoring subsurfaces in coal seams |
GB2111792A (en) * | 1981-12-09 | 1983-07-06 | Xadar Corp | Synthetic pulse radar system and method |
-
1984
- 1984-10-19 GB GB08426545A patent/GB2149992A/en not_active Withdrawn
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2030414A (en) * | 1978-07-31 | 1980-04-02 | Prakla Seismos Gmbh | Method for monitoring subsurfaces in coal seams |
GB2111792A (en) * | 1981-12-09 | 1983-07-06 | Xadar Corp | Synthetic pulse radar system and method |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2000022455A1 (en) * | 1998-10-12 | 2000-04-20 | Marconi Electronic Systems Limited | System for detection of objects in the ground |
Also Published As
Publication number | Publication date |
---|---|
GB8426545D0 (en) | 1984-11-28 |
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WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |