FR2509476A1 - COMBINED MULTI-RADAR DEVICE, IN PARTICULAR FOR AVOIDING MARITIME COLLISIONS - Google Patents

Abstract

THE INVENTION RELATES TO A COMBINED MULTIPLE RADAR DEVICE. THIS DEVICE INCLUDES AT LEAST TWO RADAR DEVICES 31, 41 CONNECTED TO SEPARATE ANTENNAS 32, 42, TARGET EXTRACTORS 33, 43 THAT CONVERT RADAR OUTPUT SIGNALS INTO DIGITAL FORM, DEVICE 51 FOR CONVERTING DIGITAL SIGNALS INTO A SYSTEM COMMON COORDINATES AND A CORRELATION DEVICE 52 DELIVERING A COMMON OUTPUT SIGNAL. THE INVENTION APPLIES IN PARTICULAR TO MARINE ANTI-COLLISION DEVICES.

Description

The present invention relates to a device with multiple radars combined,

especially in order to avoid

maritime collisions.

  Radar devices may have various limitations, including beam masking by physical obstructions, degraded operation under adverse weather conditions, and poor resolution, particularly in the case of low frequency radars. Problems and limitations posed by radars become even more important when

  radar signals are used for anti-

  collision and therefore, the invention will be described

  mainly with regard to this application although

  it is not particularly limited.

  Anti-collision devices for automatically signaling a possible collision between boats

  for example, are already known and an extreme

  satisfactory is described in the United States patent.

  United States No. 3,660,847 The general problem of alarm and collision avoidance systems, their purpose and advantages are described in United States Patent Application No. 680,685, filed April 27

1976 in the name of the Applicant.

  One of the problems measured by an on-board radar, is used with an anti-collision system is the hiding of the radar search areas by obstructions on the ship, for example chimneys, cranes, etc. Many ships ship superstructures that obstruct radar signals so that one or more sectors of

  the horizon Font "hidden" on the radar antenna

  dummy points or areas where no information is available.

  target can not be obtained, thus introducing

  undesirable uncertainty for the whole of the

  Another problem is the poor performance of

  of a high-frequency radar, that is to say, bad

  small-area radar is less affected by precipitation, but its short-range resolution is not as good As for the common practice of maritime radars, the term "high-frequency" means an operating wavelength of about 3 cm and the term "low frequency" refers to an operating wavelength of about cm. The conditions imposed on modern radars for large vessels may include the equipment of an auxiliary radar, but the signals emitted by the main radar and the auxiliary radar are not compatible and are not combined with each other. In theory, a combination

  analogue signals emitted by two separate radars to

  analogous delays but only with great complexity of the equipment, so that this combination was in fact excluded in

practical applications.

  In general, the invention therefore relates to a device for combining information from two or more radars that can operate at different frequencies and whose antennas can be

physically separated.

  The invention solves the problem of masking radar signals by using signals from spaced antennas connected to separate radar devices whose outputs are converted to digital form for

  their interchangeable use, thus ensuring

  looks on the entire horizon for visualization and / or signaling of a possible collision between a ship, for example carrying the device, and other objects.

  The invention is directed to the solution of a

  practical problem appearing particularly in ships

  equipped with alarm and / or anti-collision devices

  including, but not limited to, radar equipment It is often necessary for superstructure elements on a ship to be placed in positions that intercept radar signals in part of its scan, thus blocking the effective search of the radar. The invention eliminates this problem by using two or more radars that emit and receive with physically separate antennas and placed so as to sweep without obstruction all the

  blind regions of another or other radars.

  will be described below in the case of two

  but it is understood that additional apparatuses

  may be incorporated in the same way,

  according to the needs of a particular application.

  Echo signals or target signals from separate radars are converted into a digital form identifying target boundaries and this information can be interrogated to determine the center of the target in distance and azimuth, or they can be used directly. target signals shaped

  are converted into a common system of coordination

  data for the "addition" of the specific alignment data.

  antenna separation, antenna speeds, angle of rotation and delays in

  circuits of separated radars so that these informa-

  The features can be correlated, used interchangeably, and compared to establish target coincidences. The correlated target digital information can be used alone or

  in combination to control an anti-collision device

  comprising an automatic alarm device and which may also include a tracking and display device.

  The invention offers the possibility of comparing

  nically separate radar targets that could not otherwise be comparable to better

  verify the existence of real targets.

  the detection of a target by a device can not

  treated as a likely target but the detection

  the same target by two devices can be

  as a verified target Alternatively, the correlation

  The driver can adjustably determine the level of target signals required for target identification by one or two corrector inputs and apply them to the correlation operation. In addition, the radars can operate at very different frequencies to obtain the desired signal. combined advantage of a large

  resolution in all atmospheric conditions.

  Other features and advantages of the invention

  will be better understood by reading the description that

  will follow several examples of embodiment and with reference to the accompanying drawings in which:

  FIG. 1 is a schematic side view of a ship.

  tank to which the invention can be applied with advantage

  FIG. 2 is a diagrammatic plan view of the ship of FIG. 1 illustrating the effect of obstructions in the cham D of a radar apparatus on this ship, FIG. 3 is a schematic perspective view of another ship. showing a radar obstruction current, FIG. 4 is a plan view illustrating the areas which are masked for the radar of the vessel of FIG. 3, FIG. 5 is a simplified diagram of an anti-colision device , and

  FIG. 6 is a diagram of a combination device

  multiple radars according to the invention with

  visualization and / or anti-collision

  The invention can receive a wide variety of applications

  cations but it is particularly advantageous in the case of a maritime radar and the embodiment

  illustrated and described below corresponds to this application

  It should first be noted that an alarm device

  and / or anti-collision is intended to cooperate or to incor-

  porer a current radar device with an antenna by

  which radar signals are emitted and

  cho from targets are received These echo signals

  or target are used in an anti-collision device

  polishing report possible collisions and provide information to avoid them and it is therefore absolutely necessary that the radar device accurately detects and locates objects accurately

in the scan field.

  Although the invention can receive many applications, it will be described hereinafter mainly with regard to the combination of signals from

  two or more separate radar antennas physically-

  its use for the output of an anti-collision device, but with the indication of other

applications.

  Many ships sailing at sea have physical obstructions that disrupt the spread

  and receiving the radar signals Figure 1 shows

  diagrammatically a tanker 11 with

  a mast 12 above the bridge and carrying a tower antenna

  This radar antenna is normally mounted at a high point of the superstructures of the ship but it should be noted that different superstructures or elements may also protrude vertically.

  on the deck of the ship, Dar example a set of con-

  contents 14 stacked on the deck of the ship.

  At least some objects that protrude may

  very well to be in the trajectory of the radar beam when scanning a 3600 arc.

  blocked in some areas of the horizontal scan.

  FIG. P "schematically shows the masking of the radar signals that may occur for example by the containers 14 loaded on the deck of the ship II.

  appears that the shaded area 16 is masked for the year

  13 of the radar by parts of the cargo 14.

  Although fringe effects of radar propagation may reduce the actual size of this area, it should be noted that there is a forward view of the ship

  an area which is not monitored by the radar, to

  Targets in this ship may not be detected The presence of these blind spots or masked areas in the horizontal scan of the radar introduces uncertainties, such as tracking losses or target exchanges in the information provided to the device. anti-collision or alarm, which is undesirable in terms of protection against

a possible collision.

  FIG. 3 illustrates another current physical obstruction for the radar of a merchant ship, in the form of a massive crane structure. A radar antenna 13 placed for example on a mast above the ship's gangway would be masked. for parts of the horizon by this structure, and Figure 4 shows

  shaded areas 18a and 18b behind green parts

  of the crane 18 which are hidden for the beam

  radar from the antenna 13 In these areas, a

  such as a small vessel may not be detected

  by the radar beam emitted by the antenna 13.

  The invention provides a solution to this problem by incorporating one or more additional radars

  on the ship 11 for example The radar antenna

  The antenna is physically spaced from the antenna 13 and is arranged so that its scanning is not obstructed in part or all of the zones.

  masked or blind in scanning the device con-

  13 For example, another antennas

  may not be mounted near the bow of the ship Il so as to sweep the zone 16 without its obstruction with its radar beam and thus give information as to the presence of targets in this zone. It is obvious that the field or the sweep of the antenna 19 may be obstructed towards the stern of the ship but these areas

  are covered without obstruction by the beam of the

  With this arrangement according to the invention,

  It is possible to scan over 3600 the entire

  zon unobstructed by means of a radar beam produced by one or other of the connected devices

at antennas 13 and 19.

  Individual radar devices connected to the

  For example, signals 13 and 19 produce individually coherent and extremely useful information about the range and location of targets, but signals from these separate devices are not compatible.

  or are not linked so as to allow their combination

  normal use or their use in combination

  vention allows you to combine signals from two

  or more radar devices, thereby facilitating the

  problems of radar and other masking.

  FIG. 5 represents in simplified form a dis-

  anti-collision device with a single device

  The radar apparatus 21 emits a narrow beam of high-frequency electromagnetic radiation through an antenna 22 which rotates to scan the horizon, and this antenna 22 receives radar signals reflected by objects in the form of echo or radio signals. signals from

  The output of the radar which in the present case de-

  delivers image, trigger and azimuth signals

  is applied by the apparatus 22 to electronic circuits

  in this case a target extractor 23 in which various functions can be fulfilled

  routinely, for example, the verification of di-

  and the existence of a real target It should be noted that different conditions can produce

  false target indications, such as referrals

  xions due to atmospheric conditions In all circumstances, a parasitic signal dd at sea is produced by the reflection of certain radar signals on the sea surface, producing a noise level

  or similar, which may be high enough to

  physical objects, including targets to be considered

  Thus, the target extractor separates the information

  target identification of spurious signals,

  for example by counting the number of reflective pulses

  among a predetermined number of pulses transmitted to distinguish between random reflections and target reflections In addition, the circuit may count I number of scans in which a particular target is identified and compare that number with a predetermined number as another check of

  existence of a target There are many ways of verifying

  a target are known, including the detection "m" among "n" and at least a large number of them are applicable according to the invention Also the amplitude

  reflected pulses can be compared with a

  predetermined caliber of amplitude in the form of another

  to verify the existence of a target.

  The extractor 23, additionally and mainly, converts the data coming from the radar apparatus into

  This may for example be

  four binary words identifying the azimuth and distance limits of the detected targets This conversion is normally performed in an anti-collision device of the type described, connected to the output of the

  According to the invention, this data in numerical form

  They can then be processed by a center finder 24 who determines the distance and location of the center of the target and information about that target, because the target's boundaries or center are

  typically provided to an anti-collision calculator 26

  which may include a tracking device to produce different information such as the nearest point or the approach time of that point.

  In addition, the anti-collision device includes an alarm

  me 27 and one or more display devices 28 visually indicating the protected areas established by the device and the position of the targets in these

  zones, in analogue form and also in digital form.

  only if desired At least part of the visualization can be done on the screen of the device

  radar, as shown in dashed lines in FIG.

  The device according to the invention may incorporate an anti-collision device such as that illustrated in FIG. 5 and described briefly above. FIG. 6

  shows two radar devices 31 and 41, connected

  antennas 32 and 42, which can be separated

  physically and located, as indicated above,

  Each of the radar apparatus 31 and 41 provides data on the bearing, distance, and extent of the objects producing reflected signals. Your radar output data from the aircraft 31 and 41, as defined above, are applied separately to target extractors

  33 and 42, in which the data are conver-

  in digital or binary form and the target information can be checked as indicated

  above, each of the extractors of

  33 and 43 can attack center researchers 34 and 44 in which a digital signal is produced indicating

  the center of information or target data pro-

  from separate radar devices It should be noted that lie; the target data, ie the range and bearing limits can be used directly in the rest of the device, without locating the centers, but the elaborate devices normally perform

  the identification of the target centers.

  The device according to the invention comprises a unit 51 of alignment data containing information

  to convert digital data from

  radar in data associated with a system

  this may include information

  to convert data from a radar device

  in the coordinate system of the other, or to

  to turn the data of both devices into a separate and convenient coordinate system The term coordinate system is considered here as a reference by

  ratio at which the distance and the deposit are measured

  res, so that a correction is made for the physical separation of the antennas and it should be noted

  different delays in separate radar apparatus

  result in an apparent shift in coordination systems

  This can be better understood by considering an example of a target A situated at a relative bearing of O or 360, that is to say at the front of the ship 11 of Figure 2 With the antennas 32 and 42 of the figure 4 located at points 13 and 19 of Figure 2, it appears that the two radar devices 31 and 41 identify the target at the deposit

  0 but each device identifies it at a different distance

  rent, this difference being the distance between points 13 and 19 on the ship.

  data from radar equipment must be

  information about the position of the

  32, the alignment data unit 51 adds a constant to the distance given by the apparatus 41, this constant being equal to the distance between the

points 13 and 19 on the ship.

  Moreover, a target located at point B of FIG. 2 on a median of the segment between the points 13 and 1 causes the production by each of the apparatuses 31 and 41 of signals of equal distances, but with different deposits. These azimuth signals can by

  example represent 150 for the apparatus 31 and a

  30 of the apparatus 41 Of course, these indi-

  depend not only on the deposit but also

  Because of the physical separation of the antennas, therefore, the alignment data unit 51 contains a large number of constants related to the distance and the location of the target data.

  from the apparatus 31 and for example when

  The alignment data unit 41 also contains correction data for the different delays in the circuits of the radar apparatuses, which are added to the target data from the radar 41 to compensate the latter for the phvsic separation of the antennas.

  31 and 41 in order to fully convert the data

  output in a common coordinate system.

  output data from the radar apparatus 31 are therefore

  to the alignment data unit 51 in which the appropriate conversion constants are selected.

  on the basis of these data and are applied to a combination of

  neur 46 connected to the output of the center finder 44 associated with the radar 41 In these conditions, the data of the radar 41 are modified to correct the offset

  between antennas 32 and 42 and the differences between

time.

  In cases where it is necessary to modify the data from each of the radar apparatuses to correct the offset of the antennas relative to a central point such as the center of the ship 11, the data from the radar apparatus 41 is also applied. individually

  51 of alignment data so that its output pre-

  a correction or a modification of data of each of the devices, this output being applied not only to the combiner 46 but also to a combiner

  36 connected to the center finder 34 of the apparatus.

radar 31.

  As shown in Figure 6, the outputs of the combinations

  36 and 46 are applied to a correlator 52 in which the data of the two apparatuses are compared to determine, for example, whether the two apparatuses have identified or not the target object. In certain operating conditions, the invention may be used to

  produce an output signal from the correlator 52 at the coincidence

  identification or identification of a target by both

  or the identification of a target by either of these devices The separate target signals applied to the correlator 52 by the radar apparatus 31

  and 41 are fully compatible and therefore,

  These operations may be carried out by the corre-

  The correlator determines whether or not targets of the separate devices are simultaneously within predetermined narrow range and bearing boundaries thereby constituting the same.

  target, or if the only output of the correlator can identify

  proud two targets The correlator can also compare

  target quality information, such as

  study of the pulses indicated by the digital signals by each device or both at a predetermined level

to identify or not a target.

  I Target information from the correlator

  52 can be applied to an anti-collision calculator

  54 may include a tracking device in the form of a collision avoidance system in which information concerning the distance, bearing, velocity and trajectory of the targets appearing in the operating plane of the device has applied the range. operating the device are applied

  to a display screen 56 It should be noted, of course, that

  Anti-collision and signaling devices often offer the possibility of establishing regions or guard zones of a distance that can be determined by azimuth depth and width for the automatic generation of signals. In addition, the limits of these zones can be visualized with the indication of the position of the targets, with a view to their use.

  easy Dar operators or others.

  The device according to the invention offers a whole range of possibilities from the simple elimination of points or blind zones in the balancing of the radar

  until the verification of the targets, of different

  Thus, the output of the correlator 2 can give

  the identification of the distance and the deposit of a

  or more than one target detected by a wireless device

  dar or the other, and it may also provide information

  whether or not the target was identified by the two devices As noted above,

  this information is used in the anti-computer

  collision, either in its simplest form, ie for target identification, or in a more complex form to indicate if a target is identified

  by one or both devices.

  anti-collision devices produce a visual cue around each pursued target, and the correlator output

  can also identify the dimensions of the targets to

  cilitate the establishment of this benchmark and to give

very informative to the operator.

  It should also be noted that at least some functions according to the invention can be fulfilled in full or

  partly by a calculator, and an anti-computer

  collision can be used for this purpose when the

  positive according to the invention attacks such a device

including this calculator.

  The multiple radar device combined according to the

  vention produces output signals, as mentioned above, that can be used for different purposes

  Thus, these signals can be converted into analog signals.

  appropriate logic for controlling a

* dar current for example Figure 6 shows a converts

  57 which receives output signals from the correlator

  52 and converts them into appropriate form for

  The display screen 58 The initial radar signals

  do not have to be recreated entirely, the conversion

  above being made in analogue form,

  in direct digital form which is not normally suitable for controlling most devices

  This visualization of the

  The output signal of the device according to the invention can be very advantageous in certain cases, such as on board a

  large ship, when separate radar

  res and antennas are planned for example in Jes

opposite sides of the bridge.

  The invention allows the combination of output signals

  from separate radar equipment, and the posi-

  spacecraft antennas has been mentioned above.

  Many other examples can be

  exist and it should be noted particularly the case

  o The balancing is carried out by two devices functioning

  one high frequency and the other low frequency. The antennas of the two devices can be mounted on the same masti

  that there is practically no physical separation, but the differences in rotation speed of the antennas, their orientation and the delays in the circuits of the apparatuses make that the same target is localized at different times by the separate apparatuses. effect of different coordinate systems, which equates to a physical separation

antennas.

  The invention also applies with advantage to the

  combination of radar output signals in the circum-

  mentioned above, even if there is no physical separation

  between the antennas The advantages of the good resolution of a high frequency radar and the long range in all the atmospheric conditions of the radar

  low frequency can thus be obtained by means of

  vention This combination of a high frequency radar

  and a low-frequency radar can also be used

lised with spaced antennas.

  It should be noted that the simplified diagram of Figure 6 does not attempt to show all electrical connections or electronic components that can be used in a set, the boxes to be considered

  like functional boxes rather than circuits.

  Current electronic circuits can be used for the individual functions according to the invention and it is easy to design circuits to fulfill the functions of the separate blocks, according to the invention.

  example shown above, the radar devices function-

  one at a relatively high frequency and the other

  At a relatively low frequency, it should be noted that this is not necessary. However, there are some advantages to using different frequencies.

  for aircraft, since a low frequency radar

  quence offers a relatively poor resolution but a superior operation in the rain and with distant targets On the other hand, the high frequency radar offers a good resolution but its operation is

  degraded in bad weather conditions.

  The invention can therefore be applied not only to solving the problem of obstructions to the propagation and reception of radar signals at the antennas, but also to solving the problems posed by the

weather conditions.

  The elements and operation of anti-collision and ajarme devices in general have only been described briefly above because they are well known. However, the overall function should be emphasized.

  and the purpose of these devices which are designed to

  automatically activate audio-visual alarms when a target radar or object is

  risk of collision in order to force the operation

  to take positive action, either to stop the alarm or possibly to change the

  course or the speed of the ship to avoid the pass J i-

  The above-mentioned patent application further describes the aims, objectives and advantages of an anti-collision device and the weapon.

  such a device can also be used.

  for other purposes, for example control at

  ships with widely spaced radar antennas

  but attacking a central visualization screen,

  drilling platforms with separate radar antennas

  The invention thus relates to a device which is relatively simple, although very advantageous, which can be used

  for example to significantly improve the

anti-collision devices.

  Lien understood, various modifications may be made by those skilled in the art to the device described and illustrated by way of non-limiting example without

depart from the scope of the invention.

RIEVINDICATIONS

  1 combined radarsmultiple device for receiving output signals from at least two devices

  radar (31,41), characterized in that it comprises

  target tractors (33,43) receiving said signals

  radar output and which separately convert

  target formations of said radar output signals into digital signals, a device (51) which receives and

  converts said discrete digital signals into

  converted digital signals reported to a common coordinate system, and a correlation device (52)

  for correlating said digital signals

converted into a single output.

  2 Device according to claim 1, characterized in that it further comprises a device (57) connected

  correlation device (52) and for converting

  firing said output signal into analog signals and

  apply to a radar display device (58).

  3 Device according to claim 1, characterized in that said correlation device (52) compares

  the target signals converted into digital form

  from separate radar apparatuses (31,41) to produce a single target identification signal for signals representing target positions within limits.

  narrow and predetermined distance and deposit.

  4 Device according to claim 1, characterized in that it comprises at least two radar devices (31,

  41), one of which operates at a high frequency and the other

it works at low frequency.

  Device according to claim 1, characterized in that said radar output signals come from radar apparatus (31, 41) having radar antennas

(32,42) physically separated.

  Device according to claim 1, characterized

  in that it further comprises a device (54) for

  collision connected to receive the output signal of said correlation device (52) to signal a

  possible collision with targets identified by the-

said device.

  Device according to claim 1, characterized in that said correlation device (52) processes target information signals converted into form.

  of each of said radar apparatus for

  to produce an output signal only for certain

  predetermined formations from a radar output

o 10 or both.

  8 Device according to claim 1, characterized in that it also provides quality information

  target to said correlation device (52) for

  derive said single output signal from a quali-

  predetermined and adjustable target tee of one or more

  Separate radar output target pairing.

  9 anti-collision device, characterized in that it comprises at least two radar devices (31,41) separately connected to antennas (32,42) remote from each other, each located to scan all the blind spots on the other, a device (33,43) connected to each of said radar apparatus and for converting

  the radar output signals in digital form, a

  correlation system (52) of radar output signals in digital form, containing distance information

  and deposit, so as to produce a single identifi-

  target cation for target centers within a small predetermined distance from each other for processing as a single target and a device for applying said information

  of distance and deposit in numerical form to a

  anti-collision cultivator (54) and a visual display device

tion (56).

  Device according to claim 9, characterized in that it comprises devices (33,43) producing signals identifying each target, that this target

  whether or not de-iced by more than one radar device.

  11 device according to claim 9, characterized in that said radar antennas (32,42) are mounted in height on a ship, one in the vicinity of the bow and the other in the vicinity of the stern of the ship. Device according to claim 9, characterized

  in that it also comprises a device for comparing

  capturing target data of the digitally generated radar output signals from each of said radar apparatus, and including a target data signal compensation device (51) with respect to the possible physical separation of the antennas (32,42) and

  time differences as well as a correlation

  tion (52) which compares the compensated signals for

  identify the coincidence and non-coincidence of targets

  detected by separate radar devices.