GB2137449A - Target detection systems - Google Patents
Target detection systems Download PDFInfo
- Publication number
- GB2137449A GB2137449A GB08312960A GB8312960A GB2137449A GB 2137449 A GB2137449 A GB 2137449A GB 08312960 A GB08312960 A GB 08312960A GB 8312960 A GB8312960 A GB 8312960A GB 2137449 A GB2137449 A GB 2137449A
- Authority
- GB
- United Kingdom
- Prior art keywords
- frequency
- signal
- proximity detector
- filter
- detector according
- 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- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T7/00—Brake-action initiating means
- B60T7/12—Brake-action initiating means for automatic initiation; for initiation not subject to will of driver or passenger
- B60T7/22—Brake-action initiating means for automatic initiation; for initiation not subject to will of driver or passenger initiated by contact of vehicle, e.g. bumper, with an external object, e.g. another vehicle, or by means of contactless obstacle detectors mounted on the vehicle
-
- 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
- G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
- G01S13/345—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal using triangular modulation
-
- 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
- G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
- G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
-
- 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
- G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
- G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
- G01S2013/9317—Driving backwards
-
- 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
- G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
- G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
- G01S2013/9327—Sensor installation details
- G01S2013/93272—Sensor installation details in the back of the vehicles
Landscapes
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Signal Processing (AREA)
- Electromagnetism (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
A proximity detector is attached to the rear of a vehicle to provide an indication when the vehicle is about to reverse into an obstruction or over the edge of a precipice. An RF signal from an oscillator 6 is transmitted via an antenna 9 and received after reflection from a target by the same antenna element. The received signal is mixed at 10 with a sample of the transmitted signal to provide a beat frequency, the frequency of which is proportional to the delay between transmission of the signal from the oscillator 6 and reception at the mixer 10. The value of the beat frequency expected from targets within a region under surveillance is raised by using a delay line 8 which of course increases the delay between transmission and reception. The beat frequency is in this way raised above unwanted lower frequencies which arise from imperfections of the oscillator 6 which cause its amplitude to vary with frequency. Thus the output of a bandpass filter 12, designed to pass beat frequencies arising from targets within the region of interest, is unpolluted by the unwanted frequency and can be used e.g. by comparison with a threshold 14 to give with a great degree of reliability an indication of whether a target is present. <IMAGE>
Description
SPECIFICATION
Target detection systems
This invention relates to a proximity detector and is particularly applicable to a detector for use on a vehicle to indicate when there is an obstruction in the path of movement of the vehicle or when there is a discontinuity of the surface over which the vehicle is travelling.
The invention provides a proximity detector comprising an oscillatorforgenerating a radio frequency signal of cyclically varying frequency, the oscillator being such that the amplitude of its output varies with variations in frequency; means for radiating a signal to a region under inspection; a mixerfor mixing the signal after reflection from a target with a sample of the signal before transmission to produce an output signal having a wanted frequency component related to the time taken for the signal to travel along a path to and from any targets in said region and other unwanted components derived from the said amplitude variations, the unwanted components having frequencies equal to the frequency of the said cyclic variations and harmonics thereof; a delay device for increasing the length of the said path so that the wanted components are higher in frequency than the fundamental frequency of the cyclic variations; a filter for passing the wanted frequency components and rejecting the fundamental frequency; and means for using the output of the filter to give an indication of a target in the said region.
The delay device prevents the output of the filter being polluted by an unwanted frequency component arising from the amplitude variations of oscillator. Thus, the major component of the filter output can be considered to be indicative of a target in the region under inspection. By testing whether the output amplitude of the filter exceeds a particular threshold the presence of a target can thus be detected. In addition to eliminating the effects of the fundamental frequency of the amplitude variations of the oscillator it is possible, by selecting an appropriately large delay to eliminate the effects of first and subsequent harmonics. It is considered best to eliminate in this fashion the first five harmonics since the sixth and subsequent harmonics contain relatively little energy.
Instead of using a delay device to provide the necessary delay, this can be provided by offsetting the radiating element of the device inboard of the vehicle so that some delay is introduced during the passage of the radiated energy from the detector to the leading edge of the vehicle during transmission and vice versa during reception.Thus, in accordance with a second aspect of the invention there is provided a proximity detector mounted on a vehicle comprising an oscillator for generating a radio frequency signal of cyclically varying frequency, the oscillator being such that the amplitude of its output varies with variations in frequency; means for radiating the signal to a region under inspection the closest range of which is adjacent an extremity of the vehicle; a mixer for mixing the signal after reflection from a target with a sample of the signal before transmission to produce an output signal having a wanted frequency component related to the time taken for the signal to travel along the path to and from any targets in said region and other unwanted components derived from the said amplitude variations the unwanted components having frequencies equal to the frequency of the said cyclic variations and harmonics thereof; the detector being constructed and arranged so that the wanted components are higher in frequency than the fundamental frequency of the cyclic variations; a filter for passing the wanted frequency component and rejecting the fundamental frequency; and means for using the output of the filter to give an indication of a target in the said region.
One way in which the invention may be performed will now be described with reference to the accompanying drawings in which:
Figure lisa schematic representation of the rear of a vehicle to which a proximity detector constructed in accordance with the invention is fitted;
Figure 2 is a schematic block diagram of the detector illustrated in Figure 1;
Figure 3 illustrates the variations in frequency with time of the transmitted and received signals;
Figure 4 illustrates the variation with frequency of the output of the transmitting oscillator shown in
Figure 2;
Figure 5 shows the variations with time of the frequency of the output of a mixer shown in Figure 2;
Figure 6 shows the frequency spectrum of the output of the same mixer; and
Figure 7 is a schematic block diagram of another detector constructed in accordance with the invention.
Referring to Figure 1 there is shown a vehicle 1 which in this particular example is a large earth moving machine. The rear edge of this vehicle is indicated at 2 and the proximity detector is shown at 3 mounted inboard of the rear edge 2. The purpose of the proximity detector is to provide a signal indicating when there is an obstruction 4 anywhere within a region 5 immediately behind the vehicle. In this particular example the region 5 extends 12 feet behind the vehicle as measured from the rear edge 2 although of course it is not essential for the closest part of this region to be exactly in the line with the edge 2.
The detector is shown in more detail in Figure 2, and comprises a Gunn oscillator 6 which generates an RF signal shown in Figure 3. This varies in frequency over a range of about 100 MHz with this frequency range being chosen because oscillators capable of frequency variation over such a range are relatively inexpensive. The period of the cyclic variation is chosen in this particular example to be 400 microseconds but this is not critical. The signal from the oscillator 6 travels along a path which includes a circulator 7 and a delay line 8. The delay line 8 comprises, in this example, a coil of co-axial cable. Alternative possibilities would be a wave guide, a microstripline or any other known delay device for use at microwave frequencies.The de layed signal is transmitted in the form of microwaves from a transmitting element 9 in the form of a horn antenna having a gain pattern approximately as shown by the broken lines on Figure 1.
Signals received after reflection from a target 4 somewhere in the region 5 under surveillance pass again through the delay line 8 and via the circulator 7 to a balanced mixer 10. The mixer 10 mixes the received signal with a sample of the transmitted signal obtained from a coupling device 11 atthe output of the oscillator 6. The beat frequency FD at the output of the mixer 10 is shown on Figure 5 and is proportional to the time delay between transmission and reception except during isolated periods during which the frequencies of the transmitted and received wave forms are changing in opposite directions.
The relatively inexpensive oscillator 6 has an undesired characteristic in that the amplitude of its output varies with frequency e.g. as shown on Figure 4. Because of this the transmitted and received signals contain an unwanted frequency component of 2.5 kHz (which is equivalent to the 400 microsecond period of the wave form of Figure 3): and harmonics of this 2.5 kHz component. Thus the frequency spectrum at the output of the mixer 10is as shown on Figure 6 where the frequency FD derived from the target is shown and in addition the fundamental unwanted frequency of 2.5 kHz and its 1st, 2nd, 3rd, 4th, 5th and 6th harmonics.However, because of the delay to the signal caused by the delay line 8 and the six foot inboard offset of the device 3 from the edge 2, the frequency FD arising from a target anywhere within the region 5 will lie somewhere within the frequency bracket B shown on Figure 6 which does nsot include either the fundamental unwanted frequency of 2.5 kHz or the 1 st, 2nd, 3rd and 4th harmonics of it. The remaining harmonics are relatively insignificant. The output of the mixer 10, after amplification at 17 is passed through a filter 12 which rejects all frequency components not falling within the brackets B of
Figure 6 and therefore not arising from targets within the region 5. Because the frequency brackets
B does not include most of the unwanted frequencies it can reasonably be assumed that most of the energy at the output of the filter is due to a target such as shown at 4.The output of the filter 12 is detected at 13 and its amplitude compared with a threshold value at 14 which operates a relay 15 when threshold is exceeded.
If it were not for the delay introduced at 8 the frequency bracket B passed by the filter 12 would have to be at a much lower frequency band and would include a number of significant harmonics of the 2.5. kHz frequency. This would mean that the threshold associated with the comparator 14 would have to be raised to such an extent that the reliability of detection would be considerably reduced.
It will be appreciated that many variations to the illustrated embodiment of the invention are possible. For example the transmitted waveform of Figure 3 could be replaced by a saw-tooth waveform, a sinusoidal waveform or indeed any other repeated frequency variation. Also the delay line 8 need not necessarily be in the position indicated. It could be
positioned between the coupler 11 and the circulator 7 or between the circulator 7 and the mixer 10 though the illustrated position is preferred since, in this position, it is effective both on the transmitted and on the received signal so reducing the required length of the delay line. In another variation the delay line 8 could be omitted if the inboard offset between the detector and the extremity of the vehicle were increased by an equivalent amount.
Contrarywise this offset would not be necessary if the delay period of the delay line were suitably increased.
In another variation of the illustrated device the region under surveillance could include a portion of the ground over which the vehicle 1 is moving. A received signal would then be obtained in all normal circumstances unless the vehicle were about to reverse over the edge of a precipice. There are various ways in which the output of the relay 15 can be used, for example it could simply operate a warning device to inform the driver of the situation behind the vehicle. Alternatively it could automatically apply the brakes.
The detector shown in Figure 7 is similar two that of
Figure 2 and components of Figure 7 equivalent to those of Figure 2 are denoted by identical reference numerals appended with a prime. In this embodiment ofthe invention the circulator7 is no longer used as a means of routing transmitted and received energythrough a common horn. Instead, an additional horn 16 is used to provide a separate receive path to the mixer 10'. The delay line 8' can be placed between the coupler 11' and the horn 9' as illustrated or can be placed in the position 17 between the additional horn 16 and the mixer 10'.
Whilst the invention has been particularly described with reference to a land vehicle such as might be used in civil engineering projects it could also be applicable to any land vehicle, indeed any vehicle for use on land, on or in the water or in air.
Claims (18)
1. A proximity detector comprising an oscillator for generating a radio frequency signal of cyclically varying frequency the oscillator being such that the amplitude of its output varies with variations in frequency; means for radiating the signal to a region under inspection; a mixer for mixing the signal after reflection from a target with a sample of the signal before transmission to produce an output signal having a wanted frequency component related to the time taken for the signal to travel along a path to and from any targets in the said region and other unwanted components derived from the said amplitude variations the unwanted components having frequencies equal to the frequency of the said cyclic variations and harmonics thereof; a delay device for increasing the length of the said path so that the wanted components are higher in frequency than the fundamental frequency of the cyclic variations; a filter for passing the wanted frequency components and rejecting the fundamental frequency; and means for using the output of the filter to give an indication of a target in the said region.
2. A proximity detector according to claim 1 in which the filter also rejects the 1st harmonic.
3. A proximity detector according to claim 2 in which the filter also rejects the 2nd harmonic.
4. A proximity detector according to claim 3 in which the filter also rejects the 3rd harmonic.
5. A proximity detector according to claim 4 in which the filter also rejects the 4th harmonic.
6. A proximity detector according to claim 5 in which the filter also rejects the 5th harmonic.
7. A proximity detector according to any preceding claim in which the delay device is arranged to delay the signal on transmission and on reception.
8. A proximity detector according to any preceding claim in which the delay device is a co-axial cable, stripline or waveguide.
9. A proximity detector according to any preceding claim mounted on a vehicle in which the closest range of the region under investigation is adjacent an extremity of the vehicle.
10. A proximity detector mounted on a vehicle comprising an oscillatorforgenerating a radio frequency signal of cyclically varying frequency the oscillator being such that the amplitude of its output varies with variations in frequency; means for radiating the signal to a region under inspection the closest range of which is adjacent an extremity of the vehicle; a mixer for mixing the signal after reflection from a target with a sample of the signal before transmission to produce an output signal having a wanted frequency component related to the time taken for the signal to travel along a path to and from any targets in the said region and other unwanted components derived from the said amplitude variations the unwanted components having frequencies equal to the frequency of the said cyclic variation and harmonics thereof; the detector being constructed and arranged so that the wanted components are higher in frequency than the fundamental frequency of the cyclic variations; a filter for passing the wanted frequency components and rejecting the fundamental frequeny; and means for using the output of the filter to give an indication of a target in the said region.
11. A proximity detector according to claim 10 in which the filter also rejects the 1st harmonic.
12. A proximity detector according to claim 11 in which the filter also rejects the 2nd harmonic.
13. A proximity detector according to claim 12 in which the filter also rejects the 3rd harmonic.
14. A proximity detector according to claim 3 in which the filter also rejects the 4th harmonic.
15. A proximity detector according to claim 14 in which the filter also rejects the 5th harmonic.
16. A proximity detector according to any of claims 10 to 15 including a radiating element offset from the said extremity of the vehicle so as to increase the time period between transmission and reception of the signal.
17. A proximity detector according to any of claims 10 to 16 including a delay element so as to delay the signal before transmission from a radiating element and/or after reception by a radiating element.
18. A proximity detector substantially as described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08312960A GB2137449A (en) | 1983-03-18 | 1983-05-11 | Target detection systems |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB838307655A GB8307655D0 (en) | 1983-03-18 | 1983-03-18 | Target detection systems |
| GB08312960A GB2137449A (en) | 1983-03-18 | 1983-05-11 | Target detection systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2137449A true GB2137449A (en) | 1984-10-03 |
Family
ID=26285571
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08312960A Withdrawn GB2137449A (en) | 1983-03-18 | 1983-05-11 | Target detection systems |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2137449A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2215158A (en) * | 1988-02-04 | 1989-09-13 | Peter Anthony Lennon | Vehicle obstacle detector |
| EP0348036A2 (en) * | 1988-06-20 | 1989-12-27 | Hughes Aircraft Company | Narrow bandwith frequency modulated radar apparatus for obstacle detection |
| EP0707220A3 (en) * | 1994-10-13 | 1996-12-04 | Honda Motor Co Ltd | Radar module and radar system |
| DE19850749C1 (en) * | 1998-11-04 | 2000-03-30 | Eckart Hiss | Inductive proximity sensor for detecting metal objects; has signal from detector coil and generator coil input to mixer |
-
1983
- 1983-05-11 GB GB08312960A patent/GB2137449A/en not_active Withdrawn
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2215158A (en) * | 1988-02-04 | 1989-09-13 | Peter Anthony Lennon | Vehicle obstacle detector |
| GB2215158B (en) * | 1988-02-04 | 1992-09-09 | Peter Anthony Lennon | Method of detecting obstacles from a moving vehicle |
| EP0348036A2 (en) * | 1988-06-20 | 1989-12-27 | Hughes Aircraft Company | Narrow bandwith frequency modulated radar apparatus for obstacle detection |
| EP0348036A3 (en) * | 1988-06-20 | 1991-03-27 | Hughes Aircraft Company | Narrow bandwith frequency modulated radar apparatus for obstacle detection |
| EP0707220A3 (en) * | 1994-10-13 | 1996-12-04 | Honda Motor Co Ltd | Radar module and radar system |
| US5657024A (en) * | 1994-10-13 | 1997-08-12 | Honda Giken Kogyo Kabushiki Kaisha | Radar module and radar system |
| DE19850749C1 (en) * | 1998-11-04 | 2000-03-30 | Eckart Hiss | Inductive proximity sensor for detecting metal objects; has signal from detector coil and generator coil input to mixer |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |