WO2006018355A1 - Method for measuring a distance in a wireless carrier frequency communication system, and carrier frequency communication system for carrying out said method - Google Patents

Method for measuring a distance in a wireless carrier frequency communication system, and carrier frequency communication system for carrying out said method Download PDF

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Publication number
WO2006018355A1
WO2006018355A1 PCT/EP2005/053298 EP2005053298W WO2006018355A1 WO 2006018355 A1 WO2006018355 A1 WO 2006018355A1 EP 2005053298 W EP2005053298 W EP 2005053298W WO 2006018355 A1 WO2006018355 A1 WO 2006018355A1
Authority
WO
WIPO (PCT)
Prior art keywords
transmitting
receiving unit
signal
analysis
distance
Prior art date
Application number
PCT/EP2005/053298
Other languages
German (de)
French (fr)
Inventor
Thomas Klement
Original Assignee
Siemens Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to DE200410038836 priority Critical patent/DE102004038836A1/en
Priority to DE102004038836.9 priority
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO2006018355A1 publication Critical patent/WO2006018355A1/en

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/82Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
    • G01S13/84Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted for distance determination by phase measurement
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60RVEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R25/00Fittings or systems for preventing or indicating unauthorised use or theft of vehicles
    • B60R25/20Means to switch the anti-theft system on or off
    • B60R25/24Means to switch the anti-theft system on or off using electronic identifiers containing a code not memorised by the user
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40Means for monitoring or calibrating
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00Individual registration on entry or exit
    • G07C9/00174Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys
    • G07C9/00182Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated with unidirectional data transmission between data carrier and locks
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00Individual registration on entry or exit
    • G07C9/00174Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys
    • G07C2009/00753Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys
    • G07C2009/00769Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys with data transmission performed by wireless means
    • G07C2009/00793Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys with data transmission performed by wireless means by Hertzian waves
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C2209/00Indexing scheme relating to groups G07C9/00 - G07C9/38
    • G07C2209/60Indexing scheme relating to groups G07C9/00174 - G07C9/00944
    • G07C2209/63Comprising locating means for detecting the position of the data carrier, i.e. within the vehicle or within a certain distance from the vehicle

Abstract

Disclosed is a wireless carrier frequency communication system, especially an access authorization control system for a motor vehicle, in which the distance between two transceiver units is determined by evaluating phase data of transmitted signals. According to the invention, a reliability factor is determined to assess the correctness of the result of the distance determination process. Said reliability factor is determined by directly or indirectly detecting the curve of the phase and/or the sum of the system transmission function across substantially the entire channel width.

Description

description

Method for distance measurement in a wireless carrier frequency communication system and carrier frequency communication system for carrying out the method

The invention relates to a method for measuring the distance between a first and a second transmitting and receiving unit of a wireless carrier frequency communication system, in particular an access authorization control system for a motor vehicle. Furthermore, the invention relates to an access authorization control system, which is designed for carrying out the method.

Known conditional access control systems usually consist of a stationary transmitter and receiver unit arranged in the vehicle and of at least one key, i. a mobile transmitting and receiving unit. By wireless data transmission between the two transmitting and receiving units, the access authorization of the person in possession of the key can be checked. In these radio-based conditional access control systems, it is important to determine the distance between the mobile and stationary transceiver units. Because only in this way can be prevented, for example, that no actions are triggered in the vehicle if the owner of the key is still too far away from the vehicle. It is also necessary to prevent an unauthorized person who has gained knowledge of the signals from gaining access to the vehicle, even though the location from which the signals are sent is far away from the vehicle.

One way to determine the distance between the two transmitting and receiving units is that the located in the vehicle transmitting and receiving unit emits a signal having a certain carrier frequency, which is received by the mobile transmitting and receiving unit when the transmission signal has a sufficient signal strength at the receiving location. The mobile transmitting and receiving unit can detect the signal and synchronize a local oscillator to the carrier frequency of the received signal. The mobile transmitting and receiving unit can then send a response signal to the stationary transmitting and receiving unit, wherein the response signal at the location of the mobile transmitting and receiving unit is in phase with the signal received at this receiving location, of the fixed transmitting and receiving Receiving unit emit¬ was animal. The response signal is in turn received by the stationary transmitting and receiving unit, wherein the stationary transmitting and receiving unit can determine the distance from the phase relationship between the transmission signal and the response signal.

Instead of synchronizing a local oscillator, it is sufficient to provide a stable-running oscillator in each of the transmitting and receiving units, and to divert the actual frequency of the transmission signal or response signal from it. In the same way, the phase shift between the received signal and a signal of the same frequency derived from the local oscillator can then be determined in each of the two transmitting and receiving units. In. In connection with the response signal, this phase shift can then be transmitted in the form of corresponding data from the mobile transmitting and receiving unit to the stationary transmitting and receiving unit. This can then determine from the data transmitted to it as well as from its own determined phase shift between the received response signal and derived from the frequency of the local oscillator signal of the same frequency, the entire phase shift between the transmit and response signal and calculate the distance therefrom. In this way of determining the distance between the two transmitting and receiving units, of course, any phase distortion of the transmission path affects the accuracy of the distance determination. An extreme case of such a phase distortion arises in particular when multiple reception occurs, ie for example when the respective signal is transmitted directly on the way between the two transmitting and receiving units and when there are simultaneous reflected signal components. Such reflections can arise on reflective surfaces, such as other vehicles, house walls and the like. Of course, the transmission of corresponding signals from further transmitting and receiving units also has a phase-distorting effect in the same way.

The invention is therefore based on the object of providing a method for measuring the distance between a first and a second transmitting and receiving unit of a wireless carrier-frequency communication system, in particular an access authorization control system for a motor vehicle, in which Measuring errors caused by phase distortion of the transmission path can be detected and therefore the measurement result can be assessed in terms of its correctness. Furthermore, the object of the invention is to provide a wireless carrier frequency communication system in which this method is integrated.

The invention solves this problem with the features of patent claims 1 and 7, respectively.

The invention is based on the finding that extreme distortions, such as those caused by the occurrence of multipath reception, can be detected by generating a predetermined analysis transmission signal from one of the two transmitting and receiving units in an analysis mode whose spectral width substantially equal to the carrier frequency communication system assigned channel width and that the respective other sen¬ de- and receiving unit in the analysis mode from the received from it, with the analysis transmission signal corresponding analysis received signal a reliability factor for the evaluation of the correctness of the result for determining the distance determined. In principle, an attempt is made in this case to draw conclusions about the system transmission function of the transmission path from the analysis received signal and the knowledge about the transmitted analysis transmission signal.

According to the preferred embodiment of the method, at least one value for the distance between the first and second values can be determined when a predefined threshold value for the reliability factor is exceeded or undershot or when a predefined value range for the reliability factor is exceeded or exceeded and the second transmitting and receiving unit are rejected as invalid. In response to this discarding, it is then possible, for example, to wait a predetermined time and then to carry out the method for determining the reliability factor again. A renewed distance determination can, for example, also be carried out only if a 'valid' reliability factor could be determined in the analysis mode. Of course, the distance determination can also be carried out simultaneously with the determination of the reliability factor.

According to one embodiment of the invention, in the analysis mode, the frequency dependence of the phase or the group delay and / or the frequency dependence of the signal strength of the received analysis signal can be determined substantially over the entire bandwidth of the channel. Of course, the group delay can be determined by differentiating the frequenzabhängi¬ gene phase.

Does the frequency-dependent course of the phase over the Kanal¬ bandwidth large deviations from a linear course, given a completely undistorted transmission path, it can be assumed that a distance measurement by exploiting phase information can not be carried out with sufficient accuracy.

Since the group delay can be determined by differentiating the Phasen¬ course, the difference between the maximum and the minimum group delay within the channel bandwidth can serve as a measure of the distortion including the occurrence of multiple reception). In the same way, the frequency dependence of the signal strength of the received signal can be evaluated. In the simplest case, a constant signal strength of the respectively transmitted signal can be assumed, so that any distortion which influences the amount of the system function of the transmission path on

Receive signal is visible. Since it can usually be assumed that extreme distortion of the amount of the system function also causes a corresponding phase distortion, it can be assumed that a distance measurement by the evaluation can be assumed even in the case of impermissibly large distortions of the amount of the system function of the transmission path phase information is not possible with sufficient accuracy. In this case, for example, the difference between the maximum and the minimum signal strength of the respective received signal can be determined and used as a reliability factor.

According to a further embodiment of the method according to the invention, a preferably sinusoidally frequency-modulated analysis transmission signal having a carrier frequency preferably corresponding to the channel center may be used, wherein the modulation deviation is preferably substantially equal to half the channel bandwidth. In this case, only the signal strength of the received signal, for example, by simple amplitude demodulation has to be observed. If there is an inadmissibly large fluctuation in the signal strength and thus with the amplitude-demodulated signal, then it is possible for a unduly great distortion of the amount of the system function or the transmission path and thus also (see above) are usually assumed to be accompanied by an inadmissibly excessive phase distortion. If the course of the amount of system transfer function within the channel bandwidth has a local minimum or maximum, the result is an amplitude-demodulated signal which oscillates at twice the frequency as the modulation signal for the frequency-modulated analysis transmission signal. From the phase position of the amplitude demodulated signal and the modulation signal can then be determined whether it is a local minimum or maximum.

In this embodiment of the method, therefore, the temporal fluctuation of the signal strength of the analysis received signal, i. the fluctuation of the amplitudendemodulierten signal to determine a reliability factor are evaluated, preferably the difference between the maximum and the minimum signal strength and the difference between the maximum and minimum value of the amplitude demodulated Sig¬ nals is used as a reliability factor.

Further embodiments of the invention will become apparent from the dependent claims.

The invention will be explained in more detail with reference to exemplary embodiments illustrated in the drawing. In the drawing show

1 is a schematic representation of a wireless carrier frequency communication system in the form of an access authorization control system for a motor vehicle;

Fig. 2 are schematic diagrams of a frequency-dependent

Phase curve (Fig. 2a) and a frequenzabhängi¬ gene course de group delay (Fig. 2b) of a multipath-distorted transmission channels;

Fig. 3 is a schematic representation of the amount of a distorted by multipath reception frequency-dependent

Course of the system transfer function of Über¬ tragungskanals;

4 shows a schematic representation of the components of a carrier frequency essential for the invention.

Communication system according to the invention and

Fig. 5 is a schematic representation of the essential for the invention components of a second embodiment of a carrier frequency communication system according to the invention.

1 schematically shows a carrier frequency communication system 1, which comprises a transmitting and receiving unit 5, which is stationarily arranged in a motor vehicle 3, and a mobile transmitting and receiving unit 7. The wireless carrier frequency communication system 1 can be embodied as an access authorization control system for the motor vehicle. Each of the transmitting and receiving units 5, 7 has a transmitting and receiving antenna 9 and 11, respectively.

The carrier frequency communication system 1 can be designed in a manner known per se such that it is capable of determining the distance of the mobile transmitting and receiving unit 7 from the stationary transmitting and receiving unit 5 arranged in the motor vehicle. The data or signal transmission between the transmitting and receiving units 5, 7 can take place, for example, by the transmission of frequency- or phase-modulated signals between the transmitting and receiving antennas 9 and 11, respectively. The determination of the distance between the two transmitting and receiving units 5, 7 can take place by evaluating the phase shift between the signal transmitted by a transmitting and receiving unit and the receiving signal returned by the respective other transmitting and receiving unit. A detailed explanation of the determination of the distance from this phase information can be dispensed with, since these are methods known per se.

Of significance for the present invention, however, is that in the wireless transmission of signals between the two transmitting and receiving units 5, 7 reflections can occur, which lead to a multipath reception at the location of the respectively receiving receiving and receiving unit. In FIG. 1, this is shown schematically in the form of the two signal paths I and II. The signal path I represents the direct transmission path between the two transmitting and receiving antennas 9, 11. The signal path II shows, by way of example, the reflection of the signal transmitted by the transmitting and receiving antenna 9 at a reflecting object 13, the reflected signal component then passing along the further course signal path II to the transmitting and receiving antenna 9 of the stationary transmitting and Empfangsein¬ unit 5 in the motor vehicle passes. At the location of the transmitting and receiving antenna 9, this results in a superimposition of the signals which on the one hand extend along the signal path 1 and on the other hand along the signal path 2 to the transmitting and receiving antenna 9. Depending on the phase shift and different Damping of the signals results in correspondingly more or less pronounced constructional or destructive interferences.

The superimposition of the individual partial signals in the case of a multipath reception at the location of the respective receiving antenna can therefore lead to such large phase distortions that a distance measurement by evaluation of phase information no longer provides a reliable result. FIG. 2 a shows schematically the course of the phase of the transmission function of the transmission path between the two transmitting and receiving units 5, 7. In the case of an ideal, undistorted system transfer function, the phase progression would be strictly linear. The curvature of the assumed practical phase curve shown in FIG. 2a indicates a considerable distortion, which may be caused in particular by multipath reception, ie by signal reflections.

2 b shows the frequency-dependent profile of the group delay time τ g , which is defined as the derivative of the phase Φ according to the frequency (more precisely: according to the angular frequency ω = 2πf). The band width Δf of the transmission channel provided for the carrier frequency communication system 1 lies exactly in the range of the greatest distortions of the frequency-dependent system transmission function in the exemplary embodiment assumed in FIG.

According to the invention, it is now possible to derive from the course of the phase Φ and / or the group delay τ g over essentially the entire bandwidth Δf of the transmission channel a reliability factor for evaluating the correctness of the result for the distance determination. The more the phase progression in FIG. 2 a is curved, ie, for example, the more multipath reception is pronounced, the higher is the probability that the result of the distance determination. is not sufficiently accurate, ie deviates by more than a vorgege¬ benen amount of the actual measurement result.

According to a first procedure, the minimum and the maximum value of the group delay τ g within the bandwidth Δf of the transmission channel can be determined as a measure of the curvature of the phase curve, ie as a measure of the phase distortion. The larger the magnitude of the difference of these two values, the greater the phase distortion. Thus, the amount difference between the maximum and minimum len value of the group delay τ g within the Kanalbandbrei¬ te .DELTA.f be used as a reliability factor for assessing the Korrekt¬ unit of the result for the distance determination. For example, the result for the distance determination may be rejected as inadmissible, because in all probability too inaccurate, if the reliability factor determined in the above manner is greater than a predefined threshold value.

Of course, the reliability factor can also be determined in another way by determining the deviation of this progression from an ideal linear course of an undistorted transmission channel according to a suitable method from the course of the phase Φ (f) and a correspondingly determined value as Reliability factor is used.

According to a first embodiment of a carrier-frequency communication system 1 according to the invention, which is shown schematically in FIG. 4, a reliability factor is determined by, for example, the mobile transmitting and receiving unit 7 generating an analysis transmission signal S a having a spectral width which essentially corresponds to the band width Δf of the transmission channel. This transmit signal may be a sinusoidal carrier signal whose frequency is varied in the form of a ramp from the left lower limit frequency of the transmission channel to the upper right limit frequency of the transmission channel. As shown in FIG. 2 a or in FIG. 2 b , a discrete change in the frequency of this analysis transmission signal S a can also take place (frequencies f x -fg in FIG. 2). For reasons of simplicity, it should be ensured that the phase of each analysis transmission signal S 3 at a specific frequency with respect to a local reference signal of the mobile transmitting and receiving unit 7 has a constant phase relationship, ie a constant phase difference - points. However, it is also possible for each frequency of the analysis transmission signal S a to measure the phase relationship with respect to the local and temporally stable reference signal and to evaluate it. tion of the phase shift, the stationary transmitting and receiving unit 5 are transmitted. The stationary transmitting and receiving unit 5 in Fig. 4 receives the analysis transmission signal S a at each frequency uhd determines the phase relationship of the received analysis received signal E a at the location of the transmitting and receiving antenna 9 relative to the temporally sufficiently stable phase of a local reference signal Transmitting and receiving unit 5.

Is on the side of the analyzer transmission signal S de- 3 sending Sen¬ and receiving unit 7, no analysis transmission signal S 3 er¬ testifies, the signal of the transmitting and receiving unit 7 has with respect to a time phase stable Referenz¬ a constant Pha¬ senbeziehung (For all frequencies within the channel bandwidth .DELTA.f) and, as explained above, accordingly for each frequency of an analysis transmission signal S a respective phase value is transmitted to the transmitting and receiving unit 5, this can be from the locally detectable phase relationships (relative to a reference frequency) and the respective transmitted phase information in each case determine the phase of the analysis received signal E a with respect to a constant reference phase value. Thus, in this way in the transmitting and receiving unit 5, the course of the phase of the system transfer function according to FIG. 2a can be determined to a constant value over the entire channel bandwidth .DELTA.f of interest.

Thus, in the manner described above, the distortion of the phase within the transmission channel, for example by the determination of a value which reflects the curvature of the frequency-dependent phase in the entire transmission channel, can be determined.

As described above, for example, the continuous or discrete course of the group delay on the Phasenver¬ run determined by (numerical) differentiation and from this a reliability factor can be calculated. As shown in FIG. 4, the transmitting and receiving unit 5 can comprise, in addition to the transmitting and receiving antenna 9, a noise-like amplifier 15, which amplifies the received signal E a fed thereto by the antenna 9 and a band filter 17 connected downstream supplies. The bandpass filter 17 may have a bandpass characteristic whose lower and upper cutoff frequencies define the channel bandwidth of the transmission channel. The band filter 17 is followed by a mixer 19, which mixes the signal supplied by the band filter 17 with a mixing signal supplied by a local oscillator unit 21. The mixed signal comprises a component which includes the phase between the received signal E a and the mixed signal of the local oscillator unit 21. This signal is fed to a controller unit 23, which evaluates the signal supplied to it and carries out all necessary calculations for determining the reliability factor. For this purpose, the controller unit 23 can of course include suitable software.

To determine the reliability factor, it can first be agreed between the two transmitting and receiving units 5, 7 that both units are put into an analysis mode in which the reliability factor is determined. In this analysis mode, the transmitting and receiving unit 7 can generate an analysis transmission signal, which in each case oscillates sinusoidally with a specific frequency Fi for a specific period of time. Of course, it is also possible additionally to modulate the signal S a in order to transmit information between the transmitting and receiving units 7 and 5 at the same time. The transmitting and receiving unit 5 can have knowledge of the time span for which the analysis transmission signal S a in each case has a specific carrier frequency Fi. The local oscillator unit 21 of the transmitting and receiving unit 5 can generate a mixed signal with the respective frequency F 1 at the same time intervals. In this way it is possible to set the frequency-dependent one Course of the system transfer function to scan within the Kanal¬ bandwidth. Of course, the analysis transmission signal S a can also be generated such that in each case a continuous time-dependent change of the frequency takes place. In this case, the local oscillator unit 21 of the transmitter and receiver unit generates the mixed signal accordingly.

Of importance for this method according to the invention, however, is that the spectral width of the analysis transmission signal S 3 is at least as great as the bandwidth Δf of the transmission channel. For the purposes of the present invention, the term of the spectral width of the analysis transmission signal S a is understood to include a time-varying spectrum of the analysis transmission signal. The spectral width of the analysis transmission signal S a is determined by neglecting the time dependence in a time-variant spectrum of the analysis transmission signal, ie by superimposing all temporal snapshots of the time-variant transmission spectrum.

Another possibility for determining a reliability factor is explained below with reference to FIGS. 3 and 5.

3 shows a frequency-dependent profile of the amount of the system transfer function S (f) within the bandwidth Δf of the transmission channel assigned to the carrier frequency communication system 1. For example, as a result of multipath reception, destructive indifference leads to a minimum of the system transmission function S (f) within the transmission channel. If, in such a case, an analysis transmission signal S a is used, which has a carrier frequency which lies in the middle of the channel bandwidth Δf, and the carrier frequency is frequency-modulated with a modulation signal FM, then such an analysis transmission signal is produced S a , which is emitted from the transmitting and receiving antenna 11 of the transmitting and receiving unit 7, at the place of Transmitting and receiving antenna 9 of the transmitting and receiving unit 5, an analysis received signal E a / in addition to the Frequenzmodula¬ tion has an amplitude modulation, as shown schematically in Fig. 3.

The amplitude-modulated signal component can be amplitude-demodulated in the transmitting and receiving unit 5, wherein the amplitude-demodulated signal AM fluctuates with a temporal frequency which, in the case illustrated in FIG. 3, is twice as large as the frequency of the modulation signal FM for generation the frequency-modulated analysis transmission signal

sa-

It can thus be seen from FIG. 3 that such a distortion of the amount of the system transfer function S (f) leads to an FM-AM conversion. An ideal, distortion-free transmission channel, in which the system transmission function is frequency-independent in its amount, would have no FM-AM conversion.

Assuming, in principle, that if such a large distortion of the amount of the system transfer function occurs, a large phase distortion also exists, then it can be assumed that an increasing phase distortion is accompanied by increasing AM-FM conversion. Thus, according to the invention, even with a correspondingly large FM-AM conversion, an incorrect determination of the distance can be concluded by an evaluation of phase information.

Thus, according to the invention, to determine the reliability factor, a frequency-modulated analysis transmission signal can be generated whose spectrum substantially covers the entire channel width. If this analysis transmission signal S a is generated without the presence of an amplitude modulation, then, upon occurrence of an FM-AM conversion at the reception location, a corresponding distortion of the amount of the system transmission function S (f) of the transmission channel are closed. For this purpose, the transmitting and receiving unit 5, as shown in FIG. 5, substantially the same components beinhal¬ th, as well as the transmitting and receiving unit 5 of FIG. 4. In the case of the transmitting and receiving unit of FIG however, at least one amplitude demodulator unit (AM demodulator unit) 25 is connected between the output of the mixer 19 and the controller unit 23.

In the case of the transmitting and receiving unit 5 according to FIG. 5, the local oscillator unit 21 generates a mixing frequency which is suitable for producing a simple further intermediate frequency to be processed at the output of the mixer 19 in the usual way. This receive signal, which is mixed down to the intermediate frequency, is fed to the amplitude demodulator unit 25, which generates the amplitude-demodulated signal at its output and supplies it to the controller unit 23.

The total stroke of the amplitude-demodulated signal AM can be evaluated by the controller unit 23, for example by determining the difference between the maximum values and the minimum values. This difference can also serve as a reliability factor. The greater this reliability factor, the greater the distortion of the amount of the system transfer function S (f) and thus, as a rule, also the phase distortion of the transmission channel.

As shown in FIG. 5, the output signal of the mixer 19 mixed down to the intermediate frequency can also be supplied to a frequency demodulator unit 27. This frequency demodulator unit 27 determines the component FM of the frequency modulation from the intermediate frequency signal.

This signal is then in turn supplied to the controller unit 23 and can be evaluated by this. Of course, the amplitude demodulator unit 25 and the frequency demodulator unit 27 can also be used outside the analysis mode for signal transmission. In the same way, the Frequenzdemodulatoreinheit 27 can also be used to determine phase relationships and thus to determine the distance between the transmitting and receiving units 5, 7.

In the analysis mode, the controller unit 23 may also relate the amplitude demodulated signals and the frequency demodulated signals to each other. If the control unit 23 detects, for example, as shown in FIG. 3, that the temporal frequency of the amplitude-demodulated signal is twice as long as the time-frequency of the frequency-demodulated signal, it can be assumed that within the Bandwidth .DELTA.f of Übertragungs¬ channel is a maximum or minimum of the amount of System¬ transfer function S (f) is located. By evaluating the phase relationship between these two signals, further conclusions can be drawn on the course of the amount of the system transfer function S (f).

Of course, the course of the amount of the system transfer function S (f) can also be determined directly by using an analysis transmission signal which is changed continuously or stepwise in its carrier frequency and at the location of the transmitting transmission and transmission Empfangsan¬ antenna has a constant signal strength. The receiving transmitting and receiving unit can then determine the signal strength at the location of the receiving transmitting and receiving antenna. The course of the amount of the system transfer function S (f) which can be determined in this way can then be evaluated with regard to its curvature or the occurrence of maxima and minima, wherein in particular the occurrence of maxima and minima are typical for the presence of multipath reception , For example, a differentiation of the frequency-dependent course of the amount of the system transfer function S (f) can also be used in this case. and the maximum and minimum values of the differentiated curve within the channel bandwidth Δf are determined. This value can be used as a reliability factor.

The invention thus makes it possible to detect impermissibly large distortions of the system transmission function of the wireless transmission path and to determine a reliability factor for evaluating the correctness of the result for a distance determination which is carried out using phase information of a transmitted signal.

Claims

claims
A method for measuring the distance between a first and a second transmitting and receiving unit of a wireless carrier-frequency communication system, in particular an access authorization control system for a motor vehicle,
a) in which the distance between the first (5) and second (7) transmitting and receiving unit by the first (5) or the second (7) transmitting and receiving unit by the evaluation of the phase information is determined, which in between the first (5) and second (7) transmitting and receiving unit transmitted signals or dependent thereon internal signals is included,
b) wherein in an analysis mode by the first (5) or the second (7) transmitting and receiving unit, a predetermined analysis transmission signal (Sa) is generated whose spectral width substantially equal to the channel bandwidth associated with the carrier frequency communication system ([Delta] f) is and
c) wherein in the analysis mode by means of the respective other transmitting and receiving unit (5, 7) from the received from her, with the analysis transmission signal analysis received signal (Ea) a reliability factor for assessing the correctness of the result for the distance determination is determined.
2. The method according to claim 1, characterized in that when exceeding or falling below a predetermined threshold value for the reliability factor or when exceeding or exceeding a predetermined value range for the reliability factor at least in a timely manner with the determination of the reliability factor certain values for the distance between the first (5 < Lambda]>) and second (7 "<1>) transmitting and receiving unit are rejected as invalid.
3. The method according to any one of the preceding claims, characterized in that substantially over the entire bandwidth of the channel ([delta] f) at discrete frequency points (fi to fg) or continuously the frequency dependence of the phase ([Phi]) or the group delay ( [tau] g) and / or the frequency dependence of the signal strength of the analysis received signal (Ea) is determined.
4. The method according to claim 3, characterized in that within the channel width ([Delta] f), the difference between the maximum and the minimum group delay ([tau] g) and / or the difference between the maximum and the minimum
Signal strength determined and used as a reliability factor.
5. The method according to any one of claims 1 and 2, characterized in that a preferably sinusoidally frequency-modulated analysis transmission signal (Sa) is preferably used with a center of the carrier corresponding carrier frequency, wherein the modulation stroke preferably substantially equal to half the channel bandwidth ([Delta] f ).
6. The method according to claim 5, characterized in that the temporal fluctuation of the signal strength of the analysis received signal (Ea) is evaluated for determining a reliability factor, wherein preferably the difference between the maximum and the minimum signal strength is used as a reliability factor.
Wireless carrier frequency communication system, in particular access control authorization system for a motor vehicle,
a) having a first (5) and a second (7) transmitting and receiving unit, which are designed so that, in addition to the transmission of data, the determination of the distance from each other,
b) wherein the first (5) and second (7) transmitting and receiving unit, the distance by the evaluation of
Determine phase information contained in signals transmitted between them or internal signals dependent thereon,
c) wherein the first (5) or the second (7) transmitting and
Receiving unit in an analysis mode generates a predetermined analysis transmission signal (Sa) whose spectral width is substantially equal to the channel bandwidth associated with the carrier frequency communication system ([Delta] f), and
d) wherein the respective other transmitting and receiving unit (5, 7) in the analysis mode from the received from it, with the analysis transmission signal analysis received signal (Ea) determines a reliability factor for assessing the correctness of the result for the distance determination. 8. carrier frequency communication system according to claim 7, characterized in that first (5) and the second (7) transmitting and receiving unit are designed so that they perform the method steps according to claims 2 to 6.
9. access control authorization system for a motor vehicle according to claim 7, characterized in that the analysis received signal (Ea) evaluating and preferably also determines the distance between the (5) first and second (7) transmitting and receiving unit transmitting and receiving unit (5, 7) fixed mounting in a motor vehicle (3) is formed.
PCT/EP2005/053298 2004-08-10 2005-07-11 Method for measuring a distance in a wireless carrier frequency communication system, and carrier frequency communication system for carrying out said method WO2006018355A1 (en)

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