WO2008017617A1

WO2008017617A1 - Device and method for locating a target object

Info

Publication number: WO2008017617A1
Application number: PCT/EP2007/057876
Authority: WO
Inventors: Daniel Evers; Sebastian Kunkel; Claus Seisenberger; Leif Wiebking; Thomas Zander
Original assignee: Siemens Aktiengesellschaft
Priority date: 2006-08-09
Filing date: 2007-07-31
Publication date: 2008-02-14
Also published as: DE102006037247A1

Abstract

The invention relates to the method and a device (1) for the radio based location of a target object (2), having a transmitter for creating a transmission signal, a receiver for receiving a response signal, an antennae (3) being connected with the transmitter and the receiver, wherein the antennae (3) transmits the transmission signal of the sender and receives a response signal from the target object (2) to the transmission signal. The invention further comprises a motion sensor (31) for detecting a movement of the device, with a processing unit (30) being connected with the motion senor (31), the transmitter and the receiver, wherein the processing unit (30) transmits a transmission signal and a response signal to the transmission signal from the target object during a movement of the device at at least two different measuring positions (P1, P2), wherein the processing unit (30) detects the distance (r1, r2) each for the two measuring position (P1, P2), wherein the motion sensor (31) detects the spatial distance (3) of the two measuring positions (P1, P2) of the device (1), wherein the processing unit determines a direction from the spatial distance (d) of the two measuring positions (P1, P2) and the two measured distances (r1, r2) wherein the target object lies in relation to the device. Product: locating of labels, logistics, sensors and goods.

Description

description

Device and method for locating a target object

The present invention relates to a device for radio-based location of a target object, in particular an RFID transponder according to claim 1 and a method for radio-based location of a target object according to claim 8.

According to the state of the art, RFID

Transponder systems used to locate RFID transponders. In the field of logistics, material tracking, personal tracking or the like, there is a great need for such systems, which are able to identify and track a local position of goods and / or goods in addition to the identification.

According to the prior art, various approaches are used for the one-dimensional positioning of RFID transponders.

A first possibility is to determine the distance of a transponder to the base station by means of a location system based on field strength measurements. According to another solution locating systems are known which operate according to the SDMA method (space division multiple access). The removal of a transponder is obtained via the alignment of a highly concentrated transmitting / receiving antenna, in which the maximum of the reception level for determining the direction in which the transponder is located in relation to the antenna, is evaluated.

According to a further solution, systems for the one-dimensional distance measurement of a backscatter transponder are in use, which are based on the transit time measurement of a reflected radio signal modulated by the transponder. It is the object of the present invention to provide an apparatus and a method for multi-dimensional location of a target object with only one antenna.

The object of the invention is achieved by the device according to claim 1 and by the method according to claim 8. Further advantageous embodiments of the invention are specified in the dependent claims.

An advantage of the invention is that a multi-dimensional location of a target object with only one antenna is possible. This is achieved by moving the measuring device with the antenna and measuring during movement at at least two different positions. In addition, the spatial distance between the two measurement positions is determined and from this data an at least two-dimensional location of the target object is performed.

In a further embodiment of the invention, a target object storage angle is determined for locating the target object, which defines a direction of the target object with respect to the measuring device.

In a further embodiment, the location of the target object is carried out taking into account a frequency spacing of two frequency maxima in a mixed signal from receive and transmit signal.

In a further embodiment, a (relative) distance of the target object to the measuring device is determined on the basis of phase differences at the points of the frequency maxima of a response signal of the target object.

In a further embodiment, the measuring device in each case performs a distance measurement to the target object at the two measuring positions and determines a target object stacking angle. Due to the different distances and the relative distance between the two measuring positions.

In a further embodiment, the direction of the movement of the measuring device between two positions is detected and taken into account in locating the target object. This allows a more accurate detection of the target object.

In a further embodiment, a theoretical model is used to calculate the measuring position or to calculate the movement of the measuring device. The theoretical model preferably uses measured values of an experimentally performed movement curve of the measuring device.

The invention will be described in more detail by means of exemplary embodiments in conjunction with the figures. Show it:

Figure 1 shows an embodiment of a radio-based system for two-dimensional positioning;

Figure 2a shows a first embodiment of a one-dimensional distance measurement;

FIG. 2b shows a spectrum of the baseband for the first embodiment of a one-dimensional distance measurement;

FIG. 3 shows a second exemplary embodiment of a one-dimensional distance measurement;

Figure 4 is a graphical representation of the spectrum of the baseband according to the second embodiment for one-dimensional distance measurement;

FIG. 5 shows a first exemplary embodiment of a two-dimensional position determination;

FIG. 6 shows the course of the phase difference over the distance range of a wavelength; FIG. 7 shows the system components according to the exemplary embodiment according to FIG. 5;

FIG. 8 shows a further exemplary embodiment for two-dimensional position determination with an extended unambiguity range.

Radio-based systems are technical systems that use transmitters and receivers of electromagnetic waves. These include, for example, radar waves used, for example, in the range of 500 MHz to 100 GHz, or waves used for RFID (Radio Frequency Identification), which are used, for example, in the range of 800 MHz to 2.4 GHz. Transmit signals and response signals are such electromagnetic waves.

It follows a one-dimensional detection of the distance r _z from the base station to the target object, and detecting at least one Zielobjektablagewinkels α _z .

A target deviation angle α _z is an angle in a horizontal x, y plane or a vertical y, z plane at the horizontal plane between a main direction of the y-axis set by a moving direction of the base station , and a projection of the line from the base station to the target object in the horizontal plane or at the vertical plane between the main axis of the base station lying on the y-axis and a projection of the line from the base station to the target object in the vertical plane. By means of a Zielobjektablagewinkels α _z in the horizontal plane, the x and y coordinates are determined. By means of a Zielobjektablagewinkels α _z in the vertical plane, the z-coordinate is determined. The determination is carried out in each case in a simple manner by means of trigonometry. With the radio-based system, it is possible to locate target objects, in particular transponders, which operate on the principle of modulated backscatter, with the aid of a frequency-modulated radio signal emitted by the base station. The one-dimensional distance measurement takes place via a

Runtime measurement of the electromagnetic radio signal from the transmitter via the transponder back to the receiver. The two- or three-dimensional localization is realized with a movement of the measuring device with the single antenna with the aid of a phase evaluation. From the measurement of the phase information acquired at several positions of the signal reflected by the transponder, it is possible to deduce the respective storage angle α _{z of} the transponder. In this case, the measuring positions of the antenna are at a distance dj from one another. For two- or three-dimensional positioning only a corresponding movement of the base station with the antenna is required. By means of the acquired distance values, the exact spatial position of the transponder is determined.

The distance r _{z of} a target object or target reflector located in an observation area of a radar receiver is determined, for example, from a measurement of the signal propagation time t L from the transmitter to the reflector and back to the receiver. As a transmission signal, for example a linearly modulated in its frequency high-frequency signal (FMCW signal, are used frequency modulated continuous wave signal. Based on the distance r _z and a target deviation angle α _z can x- means of trigonometry and y coordinates are calculated.

If the target object storage angle α _{z is} detected in a vertical plane, the elevation or the z coordinate can be determined.

According to one embodiment, in order to distinguish a transponder to be located unambiguously from other interference targets in the detection range of the radar or radio-based system. which applies the principle known as modulated backscatter of the transmit signal. The signal reflected by the transponder is also given a modulation in that the backscatter cross section or the reflection behavior of the transponder antenna is periodically varied with a modulation frequency f _moc .

In accordance with a further refinement, to determine the distance r _z, a frequency spacing ΔF between two maxima in the spectrum of the baseband of a transmitted transmission signal of the antenna superposed with a simultaneously received response signal is determined. Due to the transponder modulation causes the signal components originating from the transponder in the spectrum in a higher frequency band, by (f _mo d) are moved. Above and below the modulation frequency f _moc ι of the transponder, two maxima arise whose mutual frequency difference .DELTA.F is proportional to the distance r _{z of} the transponder from the base station.

To determine the frequency spacing ΔF of the two maxima occurring at the modulation frequency f _m od, a maxima detection algorithm is used. From the determined frequency difference ΔF the distance of the transponder can be calculated according to the following formula:

₌ AF -T -C ₀

4 • B

Here, C _Q denotes the speed of light, T the ramp duration and B the frequency deviation of the FMCW transmission signal.

According to one embodiment, the relative distance r-j_ of

Target object to an antenna determined on the basis of maximum phase differences. A maximum phase difference is the difference of the phase values at the frequency locations at which the abovementioned maxima occur. Lying two

Measurements at slightly different distances before, then is the difference (change) of the maximum phase differences from these two measurements proportional to the change in distance.

According to a further embodiment, distance differences Δr-j_ of adjacent measuring positions to the target object or transponder can each be determined on the basis of a difference of maximum phase differences by means of the different measuring positions of the antenna. Due to the high sensitivity of the phase, the smallest distance differences Δr-j_ can be resolved via a phase evaluation. This property is used to determine an occurring path difference Δr-j_ between antennas and thus the target offset angle α _z .

On the basis of the ratio of distance differences Δr-j_ two adjacent measurement positions of the antenna to their distances dj at least one Zielobjektablagewinkel α _{z can be} determined. The arcussinus of this ratio is equal to the Zielobjektablagewinkel α _z . From the angle α _z and the distance r _z , finally, the x and y position of the target object can be calculated:

Is the distance r _{z of} the base station from the target object substantially greater than mutual distances dj from neighboring ones

Measuring positions to each other, then for a two-dimensional position determination, the distance to the target object is advantageously much larger than the mutual distance of the measuring positions to each other, that is r _z »d- _j . It can thus be approximately assumed that the rays reflected from the target object to the antennas run parallel to one another.

According to a further embodiment, the distance dj of adjacent measuring positions is small. Since a phase difference covers an angular range of φ with a change in distance of Δr = λ / 4, an ambiguity of the maximum Phase difference course. Because of this ambiguity, a clear distance measurement is possible only in the range of 1/4 wavelength, λ is the wavelength of the transmission signal. In order to be able to clearly detect the widest possible angular range, the distance di of the measuring positions must be selected to be correspondingly small, specifically the shorter the shorter the wavelength λ.

According to a further embodiment, the measuring positions are arranged along a horizontal and along a vertical. In this way, a three-dimensional location is possible. On the one hand, the azimuth and, on the other hand, the elevation of a target object can be determined. Together with the measured distance, the x, y and z coordinates can be calculated. In a further embodiment, the base station is moved with the antenna on a circle.

FIG. 1 shows, for example, the construction and the measured variables of a two-dimensional locating system. A base station 1, an antenna 3, a motion sensor 31, a computing unit 30, a target object 2, for example a transponder, are represented. The motion sensor 31 is designed, for example, as an acceleration sensor or magnetic field sensor which is able to determine a movement of the base station 1 both in terms of magnitude and direction. The motion sensor is firmly connected to the base station. In one embodiment, the arithmetic unit 30 can process signals of the motion sensor 31 with the aid of a sensor model and then a value for the distance traveled by the base station 1 and an angle for the

Determine the direction of the distance covered. The arithmetic unit 30 is designed in a further embodiment to use a movement model to determine the amount of movement and / or the direction of movement, i. check and specify the movement curve of the base station.

The distance of the base station 1 to the target object 2 is designated by r _z . The base station provides a device for radio-based locations. Likewise, the target offset angle α _{z is} shown. In the following, a transponder 2 is used as the target object 2. The transponder 2 to be located can work passively, that is to say field-powered without its own power supply. These may also be semi-passive, that is they are provided with their own battery or accumulator. Depending on the movement curve of the antenna 3 with the base station 1 during a measuring process, a one-, two- or three-dimensional locating is possible. In order to determine a phase information, the signal reflected by the transponder 2 can be evaluated sequentially by the base station 1 during the movement of the base station 1 at the individual measuring positions. The evaluation and the calculations are performed by the arithmetic unit 30. The transponder 2 may have an antenna 3a. A first device Ia for distance determination and a device Ib for determining the angle can be integrated in the base station 1.

The following advantages result on the basis of the inventive determination of target objects. It is possible to locate RFID brands. Likewise, a location of passive or semi-passive funkabfragbaren sensors can be done. A two- or three-dimensional locating can be done in a single reading device, since the antenna 3 moves during the measuring process to different measuring positions and this movement is detected. In this way, portable handheld readers are available for locating. When using passive and semi-passive RFID tags, the energy expenditure in the transponder 2 is low since no active, amplifying modulation method is used. Similarly, the data stream of RFID tags can be used for location. In this way, no additional hardware is required at the RFID tag. Likewise, it is advantageous to use standard RFID transponders 2, which operate on the principle of modulated backscattering.

FIG. 2A shows a first exemplary embodiment of a one-dimensional distance measurement. A device and a method for radio-based positioning, in particular of RFID tags rests in particular on the radar technology. A frequency-modulated electromagnetic transmission signal is emitted by the base station 1. The distance of a target object 2 or target reflector located in the observation area of the base station 1 or of the radar receiver is determined from a measurement of the signal transit time t L from the transmitter to the reflector and back to the receiver. As a transmission signal, for example, a linearly modulated in its frequency high-frequency signal (FMCW signal) is used.

From the frequency difference between the currently transmitted and received signal, the signal delay tL and thus the distance of the reflector can be determined. The evaluation of the frequency difference, which is proportional to the distance of the target object 2, takes place in the frequency domain. In the baseband according to FIG. 2B of the spectrum, this results in a signal peak at the frequency which corresponds to the frequency difference. According to FIG. 2A, 4 denotes the transmission signal, 5 the reception signal and 6 the difference frequency signal. The received signal 5 may be referred to as a response signal 5. ΔF denotes the frequency difference, fg the start frequency of the transmission signal 4, T the ramp duration and B the frequency deviation of the FMCW transmission signal 4. The signal propagation time is represented by tL. FIG. 2B shows the signal peak or the maximum at the frequency which corresponds to the frequency difference ΔF.

FIG. 3 shows a base station 1 with the antenna 3, via which a transmission signal 4 is sent to a transponder 2. The transponder 2 has a modulator 7, which is modulated by means of a modulation signal 8. In addition, the

Transponder 2 an antenna 3a. The transponder 2 sends back a received signal or a response signal to the base station 1. Here, the response signal is a modulated reflection signal 9. In order to clearly differentiate a transponder 2 to be located from other interference targets in the detection range of the radio-based system or the radar, a principle known as modulated backscatter is used. From the Transponder 2 reflected signal is in this case a modulation, by means of a modulation signal 8, imprinted by the backscatter cross section or the reflection behavior of the transponder antenna 3a periodically with the modulation onsfrequenz f _m od is varied. The modulation can be active or passive, but an active design, that is an active amplification of the signal in the transponder 2 is not required. The principle of modulated backscattering is extremely energy efficient, making it ideal for use in field-powered RFID transponders 2. As a modulation method, for example, an amplitude or a phase modulation can be used. Other types of modulation can also be used. For multidimensional location determination, transponders 2 based on modulated backscatter are used with particular advantage. The transponder 2 used in this case can be passive. In this case, a modulator 7 is fed from the radio field. It is therefore not a separate source of energy such as a battery or a battery on the transponder 2 required. There is an unreinforced backscatter. Likewise, the use of semi-passive transponders is possible. In this case, a modulator 7 is supplied with an integrated energy source on the transponder 2. There is also an unreinforced backscatter. Another embodiment is active transponder 2. According to this embodiment, an energy source for amplifier and modulator 7 on the transponder 2 is present. That is, the transmission signal 4 transmitted from the base station 1 is sent back intensified, or a response signal 5 is generated and transmitted.

The modulation causes the signal components originating from the transponder 2 to be shifted in the spectrum to a higher frequency band (by f _mo d).

FIG. 4 shows by way of example the spectrum relevant for the distance evaluation. Above and below the modulation frequency f _mo d of the transponder 2, there are two maxima whose mutual frequency spacing ΔF is proportional to the deviation. Distance _{z of} the transponder 2 from the base station 1 is. Signal components originating from non-modulating interference reflectors are at lower frequencies. With the aid of a bandpass, the signal components relevant for the distance determination of the transponder 2 can be filtered out. In this way, it is possible to distinguish between the signal reflected by the transponder 2 and signals originating from other non-modulating reflectors. One possibility for evaluating the distance information is created by means of digital signal processing. First, the spectrum is calculated via a Fourier transform (for example FFT), whereby methods such as weighting of the signal with a window function and zero-padding can be used to optimize the evaluation. In order to determine the frequency spacing ΔF of the two maxima occurring around the modulation frequency f mod, a maxima detection algorithm is used. From the determined frequency difference ΔF the distance of the transponder can be calculated according to the following formula:

₌ AF. T ^■ C ₀

4 • B

The evaluation of the magnitude spectrum gives an amount value for the distance with an accuracy of approximately + 10 cm.

FIG. 5 shows a first exemplary embodiment of a two-dimensional position determination by the movement of the base station 2 with the antenna 3 and a movement sensor 31 on a movement curve with two measurement positions P1, P2. Only two measuring positions are shown, wherein during a measuring process at many measuring positions a measurement of the movement curve of the base station is carried out. During a measurement, many FMCW sweeps can be performed. The motion sensor 31 determines the distance d of the measurement positions.

For a two-dimensional position determination, the reading device with the base station and the antenna is moved on the measuring curve to a first measuring position Pl and then to a second measuring position P2. The first and second measuring positions Pl, P2 have a distance d, which is detected by the motion sensor 31. At the measuring positions P1, P2, a transmission signal is transmitted by the base station and a response signal is obtained.

By a phase analysis method, it is possible to evaluate the propagation time difference of the signals from the transmitter 1 to the transponder 2 and back to the antenna 3 at the two measurement positions Pl, P2 and from α to the target deviation angle _for closing of the transponder. 2 The x and y position of the transponder 2 can thus be determined from the distance value r _z determined above.

If the distance to the target object 2 is much greater than the distance of the measuring positions Pl, P2, that is, r _z »d, one can approximately assume parallel to one another that the reflected from the target object 2 to the two measurement positions rays. This simplification is shown in FIG.

The angle α _z to the target object 2 can be determined from the distance difference Δr] _2 = ^r l ~ ^r 2 of the two beam paths:

From the angle α _z and the distance r _z , finally, the x and y position of the target object can be calculated:

To determine the distance difference Δr] _2, the phase of the signals received at the two measuring positions by the antenna is used.

For the one-dimensional measurement of the distance r _z , only the frequency spacing ΔF of the two maxima detected in the spectrum is used. For the two-dimensional position determination and thus for the determination of the target object placement angle α _z , the phase values at the locations of the two maxima in the spectrum are advantageously evaluated. For this purpose, one determines the phase at the frequency points at which the maxima occur and forms their difference:

/ / Maximum, right s / maximum, left / A \

The determined phase difference Δφ is according to the following formula:

proportional to the distance of the transponder 2 from the base station 1. λ here denotes the wavelength of the transmission signal.

FIG. 6 shows the course of the phase difference Δφ over the distance range of a wavelength λ. The phase difference Δφ passes over an angular range of 2π in the range change of Δr = λ / 4. Because of this ambiguity of the maximum phase difference curve, a clear distance measurement is only possible in the region of a quarter wavelength. However, due to the high sensitivity of the phase slope curve, a very small amount of differences are resolved. This property is used to determine the occurring path difference Δr] _2 between the two measurement positions Pl, P2 of the antenna 3 and thus the target offset angle α _{z of} the transponder 2.

The evaluation of the (maxima-phase differences) phase characteristic in the spectrum delivers an accuracy of ± 0.1 mm. However, this distance can only be stated relatively, since the uniqueness range is only λ / 4 "31 mm (at 2.4 GHz).

FIG. 7 shows a further method which uses a base station 1 with an antenna 3 and a motion sensor 31 at two measuring positions P1, P2. Once again, a target object 2 or transponder 2 is shown which has a modulator 7 modulated by means of a modulation signal 8 and an antenna 3a. With r - \ _ and Σ2 the respective distances of the two measuring positions Pl, P2 of the antenna 3 of the base station 1 to the antenna 3a of the transponder 2 are shown.

D is the distance between the two measuring positions Pl, P2. To determine the target deviation angle α _z , the procedure is now as follows:

First, the phase difference of the detected maxima of each of the antenna 3 of the base station 1 of the measurements at the two measuring positions Pl, P2 is determined:

/ 4 2π

Aφ _{2 = J /}

(6:

where Δφ] _ the phase difference of the detected maxima of

Measurement at the first measurement position Pl and Δφ2 denoting the phase difference of the detected maxima of the measurement at the second measurement position. From the difference between the two maximum phase differences Δφ] _2 = Δφ] _ - Δφ2, the distance difference Δr] _2 can now be determined with high accuracy:

Ar ₁₂ = r _λ - r ₂ = {Aφ _λ - Aφ ₂ ) ■

(7)

In this way, the target storage angle α _z of

Calculate transponders 2 according to the following formula:

a, = arcsin (8)

where d describes the distance between the two measuring positions.

Due to the periodicity of the phase slope curve with 2π, an unambiguous angle measurement is only possible in the range Δφ] _2 = + π. The uniquely detectable angular range α _{z ^ e} j_ _n cl thus results in:

"Z, _eind = ± ^<9>

In order to be able to clearly detect the widest possible angular range, the distance d of the measuring positions P1, P2 must be selected to be correspondingly small, specifically, the smaller the shorter the wavelength λ.

If the uniqueness range of the target delivery angle is too small, the following procedure can be used. The extension of the uniqueness range is possible in the following way. The uniqueness range can advantageously be achieved by means of a measuring method in which measurements are made at many closely spaced positions.

8 shows a measuring method in which the base station 1 determines the phase differences of maxima at the measuring positions P1, P2, P3, as described above. In doing so, the sisstation 1 moves from the first measuring position Pl to the second measuring position P2 and then to the third measuring position P3. At each measuring position, the base station 1 performs a measurement.

The detected phase differences of the maxima satisfy the following equations:

Λ ^2π

^{Ψl =} 17 ^'ri

/ 4

^2π2π

^{Ψl =} 17 ^'r2 / 4

^2π / 4 (10)

If the difference of the maximum phase differences from the first and second measuring position and from the second and a third measuring position is formed:

Aφ ₁₂ = Aq) ₁ - Aφ ₂

Aφ ₂₃ = Aφ ₂ - Aφ ₃

(11)

In this way, the differences between the path lengths measured at the individual measuring positions relative to the transponder 2 can be calculated therefrom:

(12)

where Δr] _2 the difference between the first and the second path length ri, T2 and with Δr23 the difference between the second and third path length T ₂ , r ₃ is designated. From the determined path differences, the target deviation angle determined by two measurement positions results:

Ar ₁₂ sin Qr ₁₂ = - -

Ar, sin α ,, = '12 (13: c where c is the distance between the second measuring position P2 and the third measuring position P3.

Assuming that r _z »d, c, one can assume that sinα] _2 ^{= s} i ^nα 23 ⁼ sinα _z . Now one subtracts the path difference Δr23 from Δr] _2 determined by the second and third measuring positions P2, P3:

Ar ₁₂ - Ar ₂₃ = sin a _z • d - sin a _z • c = sinα _z ^■ (d - c) (14)

In this way, the target deposition angle α _z can be determined _{as a} function of the distance differences Δr] _2 and Δr23 determined by the three measurement positions P1, P2, P3:

sin a = ^{Ari 2 ~ Ar 23} (15) d - c

or with the equations in the form derived for the distance differences

a, (1 6)

represent.

For a clear angle measurement, the restriction to the phase range Δφ] _2 - Δφ23 = ± π results. The maximum detectable uniqueness angle oc "", " _^ = + arcs i ^■ ni ^λ

(d ^" c), (17:

However, it no longer depends on the distance between two measuring positions, but on the difference distance between the two pairs of measuring positions d - c. In this way it is possible to set the angle range for a target location to any value between ± 90 °.

Depending on the selected embodiment, in the moving operation of the base station 1, a plurality of measurements of the distance are made using the transmission signals sent from the base station and the response signals received from the transponder. Due to the large number of measurements, a large number of values are available for the individual distances of the movement curve and the target object placement angles. In this way, due to further processing of the values for the distances and the target deviation angles with greater accuracy, the actual target deposition angles and the actual distance of the target object with respect to the base station can be calculated.

In a further embodiment, the base station is moved in one plane, preferably on a circular movement. During the movement process, a large number of measurements are carried out with the base station. For the individual measurements, a distance and a target deviation angle are determined. In addition, the movement curve is detected by means of the movement sensor 31. From the detected motion curve and the measured distances and measured target deviation angles, a precise distance and a precise aiming angle with respect to a fixed position of the base station, for example the end position of the movement process, is calculated.

In a further embodiment, the measuring device is slowly swiveled in front of the body by an operator, wherein the pivoting process takes one or two seconds from an external ren left to an outer right position of a movement curve lasts. In an FMCW measurement method for determining the distance of the target object with a sweep duration, ie a ramp duration at which the frequency is increased from a start value to a final value, of one millisecond theoretically 1000 measurements per second are possible. Thus, over 1000 measurements are available during this movement process. Thus, 1000 distances and 1000 target drop angles could be calculated to establish an exact position of the target.

A problem with the motion detection with the motion sensor 31 is generated by the signal drift. However, this problem is minimized in the measurement process described, since a defined movement is performed, which regularly provides points for readjustment. At the short times, as mentioned 1 to 2 seconds for a measurement, the drift error is also relatively low.

In a further embodiment, the measuring method can be improved by a targeted three-dimensional movement of the measuring device in the room.

Instead of the described FMCW measuring method, other methods can also be used while maintaining the basic principle of the measuring method. The basic principle is to use a base station with an antenna, to move the base station with the antenna and to perform measurements at several positions and to determine from the multiple measurements a relative spatial position of the target object to the base station.

Claims

claims

A device (1) for radio-based location of a target object (2), in particular an RFID transponder, comprising a transmitter for generating a transmission signal, with a receiver for receiving a response signal, with an antenna (3) connected to the transmitter and to the Receiver, wherein the antenna (3) emits the transmission signal of the transmitter and receives a response signal of a target object (2) to the transmission signal, with a motion sensor (31) for detecting a movement of the device, with a computing unit (30), with the movement sensor (31), the transmitter and the receiver is connected, wherein the arithmetic unit (30) transmits a transmission signal during movement of the device at at least two different measuring positions (Pl, P2) of the device (1) with the antenna (3) and receiving a response signal to the transmission signal from the target object, wherein the arithmetic unit (30) for the two measurement positions (Pl, P2) each have a distance (ri, T ₂ ) of the target object it determines, wherein the motion sensor (3) determines a spatial distance (d) of the two measuring positions (Pl, P2) of the device (1), wherein the arithmetic unit (30) from the distance (d) of the two measuring positions (Pl, P2) and the two measured distances (ri, T ₂₎ determines a direction in which the target object in relation to the device befin- det.

2. Device according to claim 1, characterized in that the arithmetic unit (30) determines a direction over a Zielobjektablagewinkel that describes a direction in at least one spatial dimension in which the target object (2) is based on the device.

3. Apparatus according to claim 1 or 2, characterized in that the arithmetic unit (30) determines the distance of the target object (2) by determining a frequency difference between two frequency maxima in the spectrum of a mixed signal from the transmitted signal and the received response signal.

4. Device according to one of claims 1 to 3, characterized in that the arithmetic unit (30) a distance of the target object to the device based on a

Phase difference between two frequency maxima in the spectrum of a mixed signal from the transmitted transmission signal and the received response signal determined.

5. Device according to one of claims 1 to 4, characterized in that the arithmetic unit (30) at the two measuring positions (Pl, P2) each determined a distance of the target object and taking into account the differences of the distances and the relative distance of the two Measurement positions (Pl, P2) determines a Zielobjektablagewinkel.

6. The device according to claim 5, characterized in that the motion sensor (31) detects the direction of movement of the device (1) between the two positions and the arithmetic unit (30) takes into account the direction of movement in the calculation of the Zielobjektablagewinkels.

7. Device according to one of claims 1 to 6, characterized in that for calculating the relative position, the computing unit (30) takes into account a theoretical model based on a predetermined movement curve of the device (1).

8. A method for radio-based location of a target object, in particular an RFID transponder having a device with the following method steps: Moving the device,

Transmitting a transmission signal and receiving a response signal of the target object to the transmission signal with an antenna at a first and a second measurement position, detecting the distance and the direction between the first and the second measurement position, wherein a distance of the target object is determined for the two positions, wherein, from the spatial distance of the two measuring positions and the two distances, a direction is determined in which the target object is in relation to the device.

9. The method according to claim 8, characterized in that the distance of the target object is determined by determining a frequency spacing between two frequency maxima in the baseband of a spectrum of a mixed signal from the simultaneously received modulated response signal and the superimposed transmitted transmission signal.

10. The method according to any one of claims 8 or 9, characterized in that the distance of the target object to the device is determined based on a phase difference between two frequency maxima in the spectrum of a mixed signal of sent Sendesignal and received response signal.

11. The method according to any one of claims 8 to 10, characterized in that each determines a distance of the target object at the two measuring positions and, taking into account the differences in the distances and the relative distance of the two measuring positions, a Zielobjektablagewinkel is determined with respect to the device, the describes a direction in which the target object is located from the device.

12. The method according to claim 11, characterized in that the direction of movement of the device between the two measurement positions are detected and taken into account in the calculation of the Zielobjektablagewinkels.

13. The method according to any one of claims 8 to 12, characterized in that for calculating the position of the target object, a theoretical model is taken into account, which is based on a predetermined movement curve of the device.