DE102013213509A1 - Method for measuring angular direction of object e.g. car, involves receiving second echo from object, and computing angular direction of object based on measurements of echoes - Google Patents

Abstract

The method involves transmitting a signal such as electromagnetic signal or acoustical signal. A first echo of the signal is received from the object (213). The first echo is returned towards the object. A second echo is received from the object. An angular direction of the object is computed based on measurements of the first echo and the second echo. The first echo is actively or passively repeated. The measurement of first echo or of the second echo is provided with time measurement or a frequency measurement. An independent claim is included for an apparatus for measuring angular direction of object.

Description

BACKGROUND

The angular resolution of a conventional remote detection echo system depends on the linear extent of the echo transmitting / receiving aperture. A transmitting / receiving one-point element (having a linear extent which is small compared to the transmitted wavelength) is substantially undirected and does not provide resolution of the angular direction of the target.

The use of multiple send / receive one-point elements spatially arranged in an array provides angular resolution.

SUMMARY

Embodiments of the present invention provide for the use of secondary circular reflections of the transmitted sensor signal from a target. In embodiments of the invention, temporal information from secondary echoes at the destination is interpreted as additional spatial information relative to the destination. Certain embodiments of the invention provide spatial information (such as angular displacement of the target) that would otherwise not be readily available. Other embodiments of the invention provide increased spatial resolution of the target. A particular embodiment for use with a real sensor array, for. For example, a virtual sensor array that has a resolution that is equivalent to the real double size array is provided.

Secondary reflections, sometimes referred to as "ghost" reflections, are well known and commonly found when a portion of the signal reflected by the target is subject to additional reflection from an undesired object, such as an object near the return path of the signal. A special case occurs when a portion of the return signal is reflected at the transceiver, returned to the destination, and re-reflected back to the transceiver. That is, a portion of the emitted signal makes a double round trip, experiencing three reflections instead of one in the process. In this case, the ghost signal seems to be at twice the distance. The target appears to be moving at twice the speed as indicated by the primary reflected signal for the target object.

Embodiments of the invention are applicable to remote sensing electromagnetic echo systems (such as radar) and to remote sensing acoustic echo systems (such as active sonar and lidar). Embodiments of the present invention are illustrated herein in the non-limiting case of motor vehicle radar, but other embodiments are also devised in other fields including, but not limited to, appropriate modes of detecting the radar spectrum and the electromagnetic spectrum, laser sensors, and optical sensors in both the visible and the visible modes as well as in the invisible parts of the spectrum; and appropriate modes for sonic, sonar and ultrasound.

Thus, in accordance with an embodiment of the present invention, there is provided a method of measuring an angular direction of an object and a method of separating narrowly spaced objects, the method comprising: transmitting a signal; Receiving a first echo of the signal from the object; Redirecting the first echo back to the object; Receiving a second echo from the object; and calculating an angular direction of the object using common measurements of the first echo and the second echo.

In addition, in accordance with another embodiment of the present invention, there is provided a method of measuring an angular direction of an object, the apparatus comprising: a signal transmitting element operable to transmit a signal towards the object proximate to the device; a signal receiving element operable to receive a first echo of the signal from the object; a signal transmission repeater operable to return the first echo toward the object such that the signal receiver receives a second echo from the object; and a processor operable to calculate an angular direction of the object based on measurements of the first echo and the second echo.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed subject matter may best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which:

1 illustrates a prior art automotive radar radiation pattern conceptually.

2A to 2D Azimuth angle direction measurements by signal transmission and reception using a reflector in accordance with an embodiment of the invention conceptually represent.

3 a simplified geometry for the in 2A to 2D represents illustrated examples.

4 Time measurements for the in 2A to 2D represents illustrated examples.

5A Figure 3 illustrates conceptually a sensor array having a retransmission element displaced orthogonally from the array in accordance with an embodiment of the invention.

5B FIG. 3 conceptually illustrates a portion of the sensor assembly having a retransmission element inserted within the assembly in accordance with another embodiment of the invention. FIG.

6 Figure 5 is a flow chart of a method for angular direction measurements in accordance with an embodiment of the invention.

7 Figure 3 is a block diagram of an apparatus for angular direction measurements in accordance with an embodiment of the invention.

For simplicity and clarity of illustration, the elements shown in the figures are not necessarily to scale, and the dimensions of some elements may be exaggerated relative to other elements. In addition, reference numerals may be repeated between the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION

1 Conceptually illustrates a vehicle radar radiation pattern 101 of the prior art, that of a vehicle radar system 103 goes out and a scanned area of an object 105 in front of the vehicle 103 provides. The broad lobe shape of the radar radiation pattern 101 is such that the angular direction of the object 105 can not be accurately determined by the radar system to a reasonable angular accuracy. In addition, two targets, if shown within the small angle, can not be distinguished or resolved so that the radar radiation pattern 101 limits the angular resolution of the motor vehicle radar. The best way for the vehicle radar system is to remove the object 105 and the rough place of the object 105 as in front of the vehicle 103 in contrast, as behind or to the side of the vehicle 103 Detect located.

The 2A to 2D conceptually illustrate angular direction measurements for an object 213 by signal transmission and reception from an angular sense sensor system 201 that is a transmitting element 203 , a receiving element 205 and a signal transmission repeating device 207 in accordance with an embodiment of the invention. The sensors of the angular direction sensor system 201 can z. Radar, sonar or lidar receivers or transceivers. Each sensor measures the transit time of a signal sent by a transmitter or transceiver of the device and received by the sensor.

In a related embodiment of the invention, the signal transmission repeating device is 207 a passive reflector such as a triple mirror. In another related embodiment, the signal transmitting device is 207 an active repeater. Any such reflector, such repeater, or any other such device capable of returning an incident signal is referred to herein as a retransmission device. Any return of an incident signal, such as reflecting, interim amplifying, or transmitting a signal that has entered the retransmission device, is otherwise referred to interchangeably herein as retransmission or return of the signal.

In 2A is through the transmitting element 203 at a time t ₀ 209 a signal 211 sent out in the way that the signal 211 an object 213 can reach. The time t ₀ 209 is directly measurable and is the angular sense sensor system 201 known.

In 2 B becomes an echo 217 the signal 211 at a time t ₁ 215 from the object 213 reflected in the way that an echo 217 a receiving element 205 and a signal transmission repeating device 207 can reach. At a time t ₂ 219 comes the echo 217 at the receiving element 205 at. The time t ₂ 219 is directly measurable and is the angular sense sensor system 201 known.

In 2C comes the echo 217 the signal 211 at a time t ₃ 223 at the retransmission device 207 and sends the retransmission device 207 also at time t ₃ 223 a retransmission 221 of the echo 217 in the way that the retransmission 221 the object 213 can reach.

In 2D becomes an echo 227 the retransmission 221 at a time t ₄ 225 in the way of the object 213 reflects that echo 227 the receiving element 205 can reach. At a time t ₅ 229 comes the echo 227 at the receiving element 205 at. The time t ₅ 229 is directly measurable and is the angular sense sensor system 201 known.

3 provides a simplified geometry for the in 2A to 2D In this simplified geometry are the transmitting element 203 and the receiving element 205 shown at the same point, at a vertex 306 a triangle 301 , are. In some embodiments of the invention, the transmitting element 203 and the receiving element 205 combined into a single device (eg to a transceiver). The object 213 is located at the top corner of the triangle 301 and the retransmission device 207 is located at a corner point 308 of the triangle 301 , A baseline 303 of the triangle 301 has a length equal to the predetermined fixed physical distance between the transmitting element 203 / the receiving element 205 and the retransmission device 207 corresponds, this distance is designated as h. In various embodiments of the invention, the retransmission device is 207 by a given distance, such as h, from the transmitting element 203 / from the receiving element 205 moved spatially. In other embodiments of the invention, the receiving element 205 a spatial extent that is greater than the displacement distance h (ie, it contains an array of individual receivers that are spatially separated from each other). If the receiving element 205 Contains N elements with an element distance d, z. B. its aperture d · N> h. Thus, an angular direction sensor system needs 201 with the retransmission device 207 generally not larger in aperture than a prior art device lacking a retransmission device. Thus, embodiments of the present invention may be used to increase the angular resolution of a direction detection system without increasing the aperture of the system.

An angular direction α 309 represents the azimuth angle direction of the object 213 in relation to the transmitting element 203 / the receiving element 205 ie the angular direction of a page 305 of the triangle 301 , In another embodiment of the invention, a calculated angular direction corresponds to the angular direction of one side 307 of the triangle 301 , In certain other embodiments of the invention, which perform Doppler shift measurements to a speed of the object 213 in relation to the angular sense sensor system 201 to calculate is an angular direction of the object 213 an angular component of a velocity vector v → 311 of the object 213 ,

4 illustrates a timetable 401 for the in 2A to 2D illustrated examples. On a timeline 405 are the times that are directly measurable and the angular sense sensor system 201 are known, ie the time t ₀ 209 , the time t ₂ 219 and the time t ₅ 229 , shown. An amplitude axis 403 conceptually illustrates the amplitudes of the respective signals. The signal 211 that at time t ₀ 209 ( 2A ) is transmitted as an amplitude 407 shown. The echo 217 that at time t ₂ 219 Will be received ( 2 B ), has a smaller amplitude 409 on. The echo 227 that at a time t ₅ 229 Will be received ( 2D ), has an even smaller amplitude 411 on.

A time interval 413 between the time t ₀ 209 and the time t ₂ 219 (t ₂ -t ₀ ) corresponds to the length of time in which the signal 211 to the object 213 running ( 2A ) and then the echo 217 returns ( 2 B ). In the simplified geometry off 4 this is the length of the page 305 times two, referred to as 2d ₁ . In embodiments of the invention that use electromagnetic signals (such as radar or lidar systems), the time-distance relationship is then considered (t ₂ -t ₀ ) = 2d₁ / c expressed, where c is the speed of light. In other embodiments that use sound signals (such as sonar systems), a similar relationship applies wherein the speed of light is replaced by the speed of sound.

If through the transmitting element 203 that's the corner 306 of the triangle 301 corresponds to a retransmission 211 would run, the time interval (t ₅ - t ₂ ) would be a second round of the page 305 of the triangle 301 correspond and would be like in 4 through a time 417 on the timeline 405 is shown equal to the time interval (t ₂ - t ₀ ). As in 2C is shown, the retransmission is 221 however, by the retransmission device 207 executed, whose position from the transmitting element 203 to the corner 308 of the triangle 301 is spatially relocated. Thus, the time t is ₅ 229 because of the spatial displacement of the retransmission device 207 from the transmitting element 203 generally by a time increment / decrement .DELTA.t 418 temporally relocated so that he has a time (t ₅ - t ₂ ) 416 is. In fact, t is ₅ 229 the time for one round of the page 305 of the triangle 301 plus one round of the page 307 of the triangle 301 , That is it is (t ₅ - t ₂ ) = 2 (d₁ + d₂) / c Thus, the sides of the triangle 301 , if t ₀ = 0 is set without loss of generality:
page 303 - h (from direct physical measurement);
page 305 - d ₁ = ct₂ / 2 and
page 307 - d ₂ = ct₅ / 2 -d ₁ = c / 2 (t ₅ -t ₂ ) ,

Thus, assuming the time measurements of t ₂ and t _{5 are} the three sides of the triangle 301 known and can the triangle 301 (such as with the cosine set) to solve the angular direction α 309 to obtain. In other embodiments of the invention, the angular direction is measured relative to other points. For example, will the angular direction in one embodiment from the midpoint of the baseline 303 of the triangle 301 measured. A transformation of the angular direction α 309 in an angular direction relative to another desired reference point is easily performed using standard techniques.

The above description and equations relate to timing measurements that include pulse signals. In the following, embodiments of the invention are shown and discussed that use phase difference measurements.

In 4 are the time duration (t ₂ - t ₀ ) 417 and the time increment / decrement Δt 418 to emphasize the point that in certain applications (such as in a motor vehicle radar) both d ₁ and d ₂ are generally much larger than h such that d ₂ ≈ d ₁ and thus the increment / decrement Δt 418 is generally small. Thus, it can be expected that the echo 227 during a time interval 419 at the receiving element 205 arrives. Accordingly, a signal processor may use a rectangular filter at the time interval 419 isolate when t _{5 is} measured to detect the echo 227 especially when the retransmission device 207 a passive reflector is weaker than the echo 217 can be.

5A schematically illustrates a sensor arrangement 501 representing a retransmission element 503 in accordance with an embodiment of the invention. The sensor arrangement 501 contains sensors 501 . 501b . 501c . 501d . 501e . 501f and 501g which are arranged horizontally, so that the sensor arrangement 501 can determine an azimuth angle direction of a target object by known phased array antenna techniques. In 5A is the retransmission element 503 in one embodiment, as orthogonal to the sensor array 501 shown shifted. The discussed below 5B shows a retransmission element that is collinear with the sensor assembly, such as between a pair of adjacent sensors.

In accordance with an embodiment of the present invention, the retransmission element 503 a retroreflector (eg an angle reflector). In accordance with another embodiment of the invention, the retransmission element includes 503 an active repeater. An active repeater involves a higher hardware cost than a passive reflector, but produces a stronger retransmission signal, resulting in a stronger received echo.

In various embodiments of the invention, the transmitted sensor signal is a pulse. In additional embodiments, the transmitted signal is a continuous wave. In further embodiments, the frequency of the transmitted signal is swept, resulting in a "chirp". Other embodiments of the invention have other waveforms. Thus, embodiments of the invention, depending on the transmitted waveform, process the received signals with techniques including time selection, frequency selection, or both time and frequency selection.

5B conceptually illustrates an embodiment of the invention that uses differential phase measurements. A section of the arrangement 505 contains sensors 505a . 505b and 501c which are arranged horizontally, so that the sensor arrangement 505 can determine an azimuth angle direction of a target object by known phased array antenna techniques. The sensor 505a is the element k-1 of the arrangement 505 , the sensor 505b is the element k of the arrangement 505 and the sensor 505c is the element k + 1 of the arrangement 505 , The elements of the arrangement 505 have a constant linear distance called Δx 519 on. Inside the arrangement 505 is a retransmission element 507 inserted, which is at a distance 521 from the element k (sensor 505b ) is located. The distance 521 is designated as Δy. The goal 513 is located in a distance called R 517 in an angular displacement designated as angle θ 515 , The distance R 517 is compared to the dimensions of the arrangement 505 big, so the angle θ 515 and the distance R 517 over all sensor elements of the arrangement 505 are essentially constant. It is a wavefront phase delay 523 for the element k (sensor 505b ) for a wavelength λ.

The phase delay φ _{1k of} the first echo at the sensor k 505b is through φ _1k = 2π / λ (2R + kΔxsinθ) given.

The phase delay φ _{2k of} the second echo at the sensor k 505b is through φ _2k = 2π / λ (4R + (kΔx + 2Δy) sinθ) given.

6 FIG. 10 is a flowchart of a method for angular direction measurements in accordance with one embodiment of the invention. FIG. In one step 601 becomes a signal 603 in the direction of an object 605 Posted. In one step 607 becomes an echo 609 from the object 605 receive and become readings of the echo 609 taken and in a reading memory 621 saved. In one step 611 becomes a signal 613 which is a retransmission of the received echo 609 is, in the direction of the object 605 repetition sent. In one step 615 becomes an echo 617 from the object 605 receive and become readings of the echo 617 taken and in a reading memory 621 saved. In one step 619 become readings of the echo 609 and the echo 617 for calculating an angular direction 623 used.

Various embodiments of the invention use similar methods to those in FIG 6 illustrated method with settings as needed in accordance with the embodiments. For example, in one embodiment of the invention, the retransmission of the signal occurs 613 through a passive reflector; in another embodiment, the retransmission of the signal 613 through an active repeater. In one embodiment of the invention, the angular direction 623 an azimuth angle; in another embodiment, the angular direction 623 an elevation angle. In one embodiment of the invention, measurements of the echo are 609 and the echo 617 Time measurements; in another embodiment, measurements of the echo 609 and the echo 617 Frequency measurements. In one embodiment of the invention, the angular direction 623 that of a location vector of the object 605 ; in another embodiment, the angular direction 623 that of a velocity vector of the object 605 ,

7 is a block diagram of a device 700 for angular direction measurements in accordance with an embodiment of the invention. A signal transmission element 701 is through a processor 707 controlled by an input from a signal receiving element 703 receives. In this embodiment, the signal transmission repeat element is 705 regardless of the processor 707 but part of the device 700 , In another embodiment of the invention, the signal transmission repeating element is 705 an active repeater, the power from the device 700 receives. In certain embodiments, the device includes 700 a clock 709 , In other embodiments, the device includes 700 a frequency selector 711 , In still other embodiments, the device includes 700 a signal processing co-processor 713 , The result of calculations by the processor 707 is an angular direction 715 ,

Claims (10)

A method of measuring an angular direction of an object, the method comprising: Sending an electromagnetic or an acoustic signal; Receiving a first echo of the signal from the object; Returning the first echo toward the object; Receiving a second echo from the object; and Calculating an angular direction of the object based on the measurements of the first echo and the second echo. The method of claim 1, wherein returning the first echo comprises actively repeating the first echo or passively reflecting the first echo. The method of claim 1, wherein a measurement of the first echo or the second echo includes a time measurement or a frequency measurement. The method of claim 1, wherein the angular direction of the object comprises an angular direction of a position vector of the object or an angular direction of a velocity vector of the object. The method of claim 1, wherein a component of the angular direction of the object comprises an azimuth angle component or an elevation angle component. Apparatus for measuring an angular direction of an object, the apparatus comprising: a signal transmitting element operable to transmit an electromagnetic or acoustic signal towards the object in the vicinity of the device; a signal receiving element operable to receive a first echo of the signal from the object; a signal transmission repeater operable to return the first echo toward the object such that the signal receiver receives a second echo from the object; and a processor operable to calculate an angular direction of the object based on the measurements of the first echo and the second echo. The device of claim 6, wherein the signal retransmission element comprises an active signal repeater or a passive signal reflector. The apparatus of claim 7, wherein a measurement of the first echo or the second echo includes time measurements or frequency measurements. Apparatus according to claim 7, wherein the angular direction of the object is an angular direction of a Position vector of the object or an angular direction of a velocity vector of the object comprises. The apparatus of claim 7, wherein a component of the angular direction of the object comprises an azimuth angle component or an elevation angle component.

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