METHOD FOR DETERMINING A DISTANCE BETWEEN TWO OBJECTS WITH THE INVOLVEMENT OF A THIRD OBJECT

Description

[0001] The invention relates to a method for determining a distance between two objects with the assistance of a third object.

[0002] From EP 2710398 B1 it is known to passively determine the location in an anchor network by listening to the communication of the anchors, by determining several distances and from this determining the location or the distance to one or more anchors.

[0003] From US patent 2020 / 118372 A1, it is known to use a passive sniffer in a vehicle to determine the distance to a key after communication has been initiated by an active node in the vehicle. The most suitable antennas are selected from a large number of available antennas based on RSSI values. Differently polarized antennas are used, and round-trip times or phase shifts are measured for each frequency at which a round trip is performed, or the differences between them are determined. For this purpose, the change in phase over one round trip at a first frequency is compared with the change in phase over a second round trip at a second frequency, taking into account the change from the first to the second frequency. Phase-coherent switching between the frequencies is not performed, and the phase difference during switching is also unknown.

[0004] Summary: The invention is defined by the following claims

[0005] Detailed description: The object of the present invention is to determine the distance between at least two, in particular at least three, objects, wherein a first of the objects emits several signals with different frequencies, in particular sequentially, in particular frequency hopping, wherein at least a third object also emits signals, in particular frequency hopping, and the second of the objects receives the signals of the first and the at least one third object and the distance between the first and the second objects is determined therefrom, without requiring an indirect determination, for example via the distance between the first and the third object, wherein in particular the second and third objects are time-synchronized and / or in particular are arranged in a fixed relative spatial orientation.

[0006] The first object can be, in particular, an authorization device such as a key fob or mobile phone. The second and third objects are, in particular, part of an arrangement to which access is sought and / or granted by means of the authorization device. This arrangement can be, for example, a building, a motor vehicle or barrier, a vending machine, or a computer.

[0007] This is solved, among other things, by a method for determining the distance between two objects, in particular directly, wherein a first of the objects sends at least one first-object signal, in particular several first-object signals, with different first-object frequencies, and wherein the at least one second object receives the first-object signals of the first object and, based on this, the distance between the first and the at least one second object is determined, wherein the at least one second and at least one third object are clock- and / or time-synchronized, wherein the at least one second object does not send any signals except for time synchronization and / or the at least one second object does not send any signals used for distance determination and / or is passive apart from time synchronization, wherein in particular the at least one second object does not send any radio signals, characterized in that the at least one third object sends at least one third-object signal.This third-party object signal can be used and / or suitable for distance determination, for example based on phase-based ranging (PBR) and / or time-of-flight (ToF) measurements, and / or solely for coordinating timing or transmitting information for process control, such as for its initialization. In any case, some form of radio communication takes place between the first object and at least one third-party object.

[0008] Particularly preferred is the calculation and / or improvement of time synchronization between the first and second and / or between the second and at least one third and / or first and at least one third object based on at least one first and / or third signal.

[0009] It is advantageous for the first and / or third object signals to each include at least one frequency hopping. This increases the accuracy of the method.

[0010] Frequency hopping refers specifically to the sequential transmission on different frequencies. Bidirectional frequency hopping occurs when two objects, particularly one after the other, perform frequency hopping.

[0011] In particular, the frequencies, especially those of frequency hopping, lie within a range of 25 to 100 MHz, and in particular, they completely exceed such a range. In particular, the frequencies, especially those of frequency hopping, lie within the range of 2 to 6 GHz. In particular, there is a spacing of 0.1 to 17 MHz, and in particular of 0.5 to 10 MHz, between adjacent but not necessarily consecutive frequencies, especially those of frequency hopping.

[0012] In a first embodiment, the third object can switch between at least two third-object frequencies in a phase-coherent manner and / or switch in such a way that the phase difference at the first and / or second object is known and / or the phase difference is made known to the first and / or second object.

[0013] In a second embodiment, which can also be combined with the first, the first object can switch in phase coherence between at least two of the first-object frequencies of the at least one first-object signal and / or switch in such a way that the phase difference is known at the second and / or third object and / or the phase difference is made known to the second and / or third object.

[0014] The phase difference or jump during the change between frequencies may be known, for example, because it is predetermined or can be derived from other known quantities, such as the duration of a preceding radiation at a frequency, especially immediately.

[0015] The phase difference typically arises during switching between two frequencies for technical reasons, but it can also be avoided. Switching between two frequencies can be performed with a brief interruption or without an interruption. At the moment of an uninterrupted switch, the phase jumps; during a switch with an interruption, the phase of the signals, imagining their continuation into the interruption, jumps before and after the switch. At the switch point without an interruption, or at an imaginary switch point within the interruption—particularly in the middle of the interruption and / or at the end of the signal before the interruption or at the beginning of the signal after the interruption—a defined phase jump occurs. This is the phase difference.

[0016] Preferably, the at least one third object switches between the at least two third object frequencies, in particular for receiving the first object signals, wherein these third object frequencies are then in particular identical or at least similar to the respective first object frequencies, and / or for transmitting at least one, in particular several, of its own third object signal(s).

[0017] In this process, at least one second object receives the first and third object signals from the first and at least one third object, and the distance between the first and at least one second object is determined from or based on this.

[0018] Preferably, at least one distance is determined between the first and every second object.

[0019] In particular, signals transmitted by the second object are not used for distance determination and / or the procedure is conducted in such a way that they play no relevant role in this purpose and / or they do not improve the accuracy or only improve it insignificantly, in particular by less than 10% of the accuracy, in particular by less than 2% of the accuracy, i.e., for an accuracy of 1 m / 100 m, for example by less than 10 cm / 100 m, in particular by less than 2 cm / 100 m, i.e., not to an accuracy better than 90 cm / 100 m or not to an accuracy better than 98 cm / 100 m. In particular, signals transmitted by the second object are used exclusively for time synchronization. Although time synchronization or the synchronization of the clock generators is strongly preferred, this can also be achieved by means other than signals from the objects.If it is (also) caused by signals from the second object, these signals are used indirectly, by using knowledge of the times in the objects or their drift or their synchronicity for distance determination, but preferably not the signals themselves, in particular not their propagation times and not their phase angles, even if these may have been used for time synchronization.

[0020] If one imagines the procedure as follows: time synchronization is achieved, among other things, with a first set of signals from the second object, and a second set of signals from the first and at least one third object are sent. In particular, the procedure is conducted in such a way that the accuracy of the distance determination using signals from the first set, the second set, and the synchronized clocks is not more than 10%, and in particular not more than 2%, better than the accuracy of the distance determination based solely on the second set and the synchronized clocks.

[0021] It is advantageous for at least one third-object signal to have different third-object frequencies and / or to switch between them.

[0022] The signals, in particular primary and secondary object signals, are primarily radio signals.

[0023] In particular, the distance is determined based on frequencies and phases (phase-based ranging), especially amplitudes, of the first and third object signals received at at least one second object, as well as the time differences between the first and third and between the third and second object, and especially information about the emitted first and / or third object signals, such as the times of emission of certain features, for example frequency changes and / or their times of emission of the first and / or third object signals.

[0024] Optionally, information provided by at least one third object, in particular phase correction information, can be used via the at least one received first object signal and / or information provided by the first object, in particular phase correction information, via the at least one third object signal.

[0025] In particular, the at least one primary and / or at least one secondary object signal has at least one feature per frequency and / or per signal.

[0026] Signal features include, in particular, changes in the signal, such as changes in amplitude, polarization, the radiating antenna (switching between antennas), frequency, and / or phase. For example, such a feature could represent the beginning or end of the radiation of a frequency. However, aggregated groups of features can also be used, which in some situations increases the robustness of the method. For instance, superimposed packets or sync words can be used as groups of features.

[0027] The problem is also solved by a system comprising at least one first, one second, in particular a plurality greater than one, in particular greater than two, second objects, and at least one third object, wherein the first object is configured to emit first-object signals of different frequencies, and preferably the at least one third object is configured to emit third-object signals of different frequencies, and all objects are configured to receive signals, wherein the at least one second and the third object are configured to perform clock and / or time synchronization, and wherein the system comprises at least one control system configured to carry out the methods according to the invention, characterized in that the third object is configured to switch between at least two third-object frequencies in a phase-coherent manner and / or to switch in such a way thatthat the phase difference at the first and / or second object is known and / or the phase difference is communicated to the first and / or second object and / or that the first object is configured to switch in phase coherence between at least two of the first-object frequencies of the at least one first-object signal and / or to switch in such a way that the phase difference at the second and / or third object is known and / or the phase difference is communicated to the second and / or third object.

[0028] The system is also solved by an access system comprising at least one access restriction device, wherein the access restriction device is configured to grant and / or deny access, in particular by means of an access restriction means, further comprising at least one first, one second, in particular a plurality greater than one, in particular greater than two, second objects, and at least one third object, wherein the first object is configured to emit first-object signals of different frequencies, and in particular the third object is configured to emit third-object signals of different frequencies, and all objects are configured to receive signals, wherein the at least one second and the third object are configured to perform clock and / or time synchronization, and wherein the third object is configured to communicate between at least two third-object frequencies, in particular the third-object signals.and / or wherein the first object is configured to switch between at least two first-object frequencies of the first-object signals, and wherein the system comprises at least one controller configured to carry out the methods according to the invention by determining at least one distance between at least one second object and the first object, wherein the access restriction device is configured not to deny access and / or to grant access if the at least one determined distance between the at least one second object and the first object does not exceed a predetermined distance and / or lies within a predetermined distance range and / or the determined position of the first object is within a first and / or outside a second predetermined range, and / or to deny access and / or not to grant access if the at least one, in particular all,a certain distance(s) between the at least one second object and the first object exceeds the predetermined distance and / or lies outside the predetermined distance range and / or the certain position of the first object is outside a first and / or within a second predetermined range, characterized in that the third object is configured to switch between at least two third-object frequencies in phase coherence and / or to switch in such a way that the phase difference at the first and / or second object is known and / or the phase difference is made known to the first and / or second object and / or that the first object is configured to switch between at least two of the first-object frequencies of the at least one first-object signal in phase coherence and / or to switch in such a way,that the phase difference at the second and / or third object is known and / or the phase difference is made known to the second and / or third object.

[0029] Phase-coherent switching or switching between two frequencies means, in particular, that the phase after the switch is known relative to the phase before the switch. This is the case if the change in phase during switching is zero or a known value. If the switch is performed in such a way that the phase difference is known, then the difference in phase before and after the switch is known. This value can also be known in advance because it can be derived from known quantities, for example, from the duration of the preceding radiation at a given frequency, especially if it was immediately present.

[0030] This is the case, for example, when a defined phase angle is always set during switching and the duration of the emissions since the last switching is measured or known.

[0031] The knowledge of the phase shift during frequency changes is particularly advantageous for enabling simple measurements and calculations, for example, to correct for measured changes in phase shift. When the phase shift is zero, this knowledge is also used, specifically by directly applying the measured change in phase shift to calculate a distance; it is essentially only corrected for zero.

[0032] Direct distance determination significantly improves accuracy and / or speed compared to the method from EP 2710398 B1.

[0033] While it is known to synchronize timers in two objects via both wired and wireless connections—for example, the NTP protocol exists—synchronization is also possible within a Bluetooth connection. In this method, each object has a free-running 28-bit clock with a frequency of 3.2 kHz, and each object determines its offset relative to a central clock and corrects it regularly. This achieves synchronization with an accuracy of approximately 125 ns. Improved time synchronization methods are also known, for example, from DE112014004426T5 or "Synchronization in Wireless Sensor Networks Using Bluetooth," Casas et al., Third International Workshop on Intelligent Solutions in Embedded Systems, 2005, ISBN: 3-902463-03-1.This can be used, for example, to save energy by keeping one object ready to receive only during specific time slots known to the other object, allowing it to transmit at corresponding times. Synchronization of the clocks is still possible, at least in the case of relatively strong interference on one side of the radio channel, although known distance measurements become impossible, very inaccurate, or extremely time-consuming under such interference. However, the accuracy of time synchronization differs from synchronization to a clock signal at the receiver. Here, there is no synchronization of two clocks on two objects; rather, the receiving object is adjusted to be synchronized with the incoming signal. The signal propagation time is irrelevant in this case, as it does not depend on when the signal was sent or how long it took to transmit.

[0034] It is particularly advantageous if at least a second and a third object are synchronized to 10 ns or better, especially in the range between 10 ns and 100 ps, ​​in terms of time and / or clock cycle. This increases the accuracy of the process.

[0035] It is particularly advantageous to time- and / or clock-synchronize at least one second and the first and / or the first and at least one third object, especially to 10 ns or better, particularly in the range between 10 ns and 100 ps. This increases the accuracy of the method.

[0036] The difference in drift between the timekeepers of the first and at least one second object, or between at least one second and at least one third object, can also be determined and used for correction. Numerous methods for this are known from the prior art.

[0037] Advantageously, for each first and third object signal received by a second object, a value proportional to its amplitude and a phase value are determined, and in particular, a complex number is derived from each of these values, which is used to determine the distance between the first and second objects. Specifically, a matrix, in particular an autocorrelation matrix, is formed from a plurality of the complex numbers of the first and / or third object signals, and the distance is determined using this matrix and, for example, comparison with, distance calculation to, and / or projection onto transmission and / or reception characteristics. In particular, at least one complex matrix, in particular an autocorrelation matrix, is formed for first object signals received by a second object, and / or at least one matrix, in particular an autocorrelation matrix, is formed for third object signals received by a second object.The distance calculation is advantageously carried out by determining the eigenvalues ​​or eigenvectors of at least one matrix and / or by Fourier transformation of the complex values.

[0038] The phase value is determined, in particular, alternatively, by calculating a change in the phase shift normalized to a frequency difference for a multitude of signal pairs with adjacent frequencies. This involves approximately calculating the derivative of the phase shift at one of the frequencies of the pair and using the values ​​obtained to determine the phase of the complex number at the respective frequency (the value corresponding to the amplitude), especially by approximate integration over the frequency. Integration does not necessarily have to begin at f = 0 Hz; instead, an offset common to all complex numbers can and preferably is used, in particular the lowest frequency of the selected signals. Specifically, the phase value is determined from the signal propagation delay or signal rounding time.

[0039] In particular, the normalized phase shift change (dphase shift (f1,f2)) is obtained using the formula: dPhasenverschiebung f 1 , f 2 = a * RTT f 3 * dFrequenz f 1 , f 2 or dPhasenverschiebung f 1 , f 2 = b * STT f 3 * dFrequenz f 1 , f 2 where dFrequency(f1,f2) is the difference between the frequencies f1 and f2, RTT(f3) is twice the signal propagation time or the signal round-trip time (pulse propagation time, ToF) between the first and second object, or STT is the single signal propagation time (pulse propagation time, ToF) at one or more frequencies f3, similar to f1 and / or f2 and / or vice versa, and where a or b is a constant, in particular a equals Pi and b is two Pi.

[0040] Phase shift is a phase shift in the transmission of a signal at a given frequency from one object to another and back, which occurs due to the distance. It can be approximately equated to twice the phase shift that occurs in the transmission of a signal at a given frequency from one object to another due to the distance.

[0041] Frequencies are considered to be similar, in particular, if they differ from each other by less than 17 MHz, in particular less than 10 MHz, in particular less than 2 MHz, and / or by less than 5%, in particular less than 2%, of the lower frequency.

[0042] The complex value Z for a frequency is then obtained in particular by means of: Betrag Z f = b * Amplitude f + offset

[0043] Argument(Z(f)) = Sum(dPhaseshift(f(n + 1),fn)) over fn from f0 to f(n + 1) = f.

[0044] The changes in phase shift are summed, from the lowest frequency up to the frequency in question for which the complex number is to be determined. The lowest frequency is approximately the same, and in particular identical, for all complex numbers. Furthermore, the phase shift changes are always summed for successive frequency pairs where the higher frequency is approximately equal to, and in particular identical with, the lower frequency of the next pair. with f = f n + 1 f0 is approximately the same for all complex numbers of a vector and / or a matrix, in particular equal to .

[0045] Here, b and offset are constants, and b is specifically equal to 1 and offset is specifically equal to 0. Amplitude(f) is the received amplitude measured at frequency f, or an average of several amplitudes measured at frequency f and / or frequencies similar to f. Alternatively, power can also be used.

[0046] In particular, a matrix, specifically an autocorrelation matrix, is formed from a plurality of complex numbers. This is done by creating a vector of complex numbers, writing the complex numbers into the columns or rows of the vector, and then constructing its autocorrelation matrix. Using this matrix, for example, by known methods such as MUSIC, CAPON, comparison with, distance calculation to, and / or projection onto transmission and / or reception characteristics, the distance is determined. Advantageously, the distance calculation is performed by determining the eigenvalues ​​or eigenvectors of the at least one matrix and / or by Fourier transforming the complex values.

[0047] Such procedures are particularly advantageous in the case of multipath signal propagation in order to achieve a reliable determination.

[0048] In certain configurations, it can be advantageous to arrange at least one second and the third object in a fixed relative spatial position and orientation, for example, when distance measurement is carried out for access control purposes. This simplifies the calculation and increases reliability.

[0049] Advantageously, data is transmitted using the first object and / or third object signals, in particular user data, especially data that is not required for the method according to the invention.

[0050] Advantageously, the objects are parts of a data transmission system, in particular a Bluetooth, WLAN, or mobile communication data transmission system. Preferably, the primary object and / or secondary object signals are signals of the data transmission system and / or a data transmission standard, for example, a mobile communication standard, WLAN, or Bluetooth, which are used for data transmission in accordance with the data transmission standard.

[0051] Advantageously, the first object and / or third object signals are transmitted via multiple antenna paths, in particular with multiple antennas, especially sequentially, at the sending object and / or received with multiple antennas at the receiving object.

[0052] Preferably, the first object is an authorization device, such as a key fob or mobile phone. Advantageously, the second and third objects are part of an arrangement to which access is sought and / or granted by means of the authorization device, wherein the arrangement is in particular a building, a motor vehicle or barrier, a vending machine and / or a computer.

[0053] It is preferred that the third object receives the signals from the first object and provides information about these signals, which is then used to calculate the distance, and / or that the first object receives the signals from the third object and provides information about these signals, which is then used to calculate the distance. This is particularly advantageous if the time of transmission and / or the phase at the time of transmission would otherwise be unknown within the system.

[0054] A particular advantage is that at least one second object is passive and / or does not itself transmit any signals or signals used for distance calculation, and / or does not itself transmit any signals or signals used for distance calculation within the procedure. This allows the procedure duration to be shortened and the security measure based on the distance determination between the first and at least one second object to be concealed and thus made more secure.

[0055] Preferably, the method is designed such that at least one of the transmitting objects (first and / or at least one third object) switches between signals in phase coherence, in particular without a phase shift or with a known phase shift, and / or the phase shift is measured locally and taken into account and / or corrected in the distance determination, and / or at least one of the objects determines at least one phase correction piece of information from signals of one of the other objects, which is used in the distance calculation.In particular, wherein the first object switches in phase coherence between at least two of the first-object frequencies of the first-object signals, and / or the third object switches in phase coherence between at least two of the third-object frequencies of the third-object signals, and / or the third object determines at least one phase correction piece of information from the first-object signals, and / or the first object determines at least one phase correction piece of information from the third-object signals, and wherein the at least one phase correction piece of information is used in the distance calculation. Such a design, in which further information about the phase relationship at the transmitting object is available, allows the method to be made more accurate, more robust, and the calculation simpler.

[0056] In particular, the first, second, and / or third objects also switch to phase-coherent reception. As a workaround, they measure the phase shift during the frequency change, and this phase shift is corrected during the calculation.

[0057] Advantageously, not only the sending object but also the received one is switched in phase coherently; in particular, a PLL is switched in phase coherently in each object.

[0058] A particular advantage is that the timing and / or schedule of the transmissions of the third-object and / or first-object signals is predetermined, and / or is / are known to the second object, and / or is / are taken into account in the distance calculation. This allows for a more precise determination and simpler calculation.

[0059] In a preferred embodiment, the method includes the synchronization of times and / or clock cycles in at least one second and third object, particularly wirelessly or via cable. Preferably, at least one time and / or clock synchronization and / or correction between the at least one second and third object is performed before, after, and / or during the execution of the method. However, the synchronization may also be present or achieved by other methods. In particular, the differences in times and / or clock cycles between at least one second and third object are known and / or synchronized. This increases the accuracy of the method. Preferably, a drift of the clocks of the at least one second and / or third object, or a difference in the drift of the clocks of the at least one second and third object, is also determined and taken into account when determining the distance. This further increases the accuracy of the method.In a preferred embodiment, the method includes the synchronization of times and / or clock cycles between the second and first objects, particularly wirelessly. Preferably, at least one time and / or clock synchronization and / or correction between the first and third objects is performed before, after, and / or during the execution of the method. However, synchronization can also be achieved naturally or by other methods. In particular, the differences in times and / or clock cycles between the second and third objects are known and / or synchronized; the alignment can also be performed via cable. This increases the accuracy of the method. Preferably, a drift of the clocks of the first and / or third object, or a difference in the drift of the clocks of the second and third object, is also determined and taken into account when determining the distance. This further increases the accuracy of the method.Methods for synchronization and / or for determining time and / or clock differences and / or drift are extensively known from the prior art.

[0060] Time differences and / or drift can also be determined indirectly using a triangular relationship: For example, if the time difference and / or drift between X and Y as well as between Y and Z is known, the time difference and / or drift between X and Z can be calculated from this.

[0061] Preferably, the second and / or at least one third object determines its time and its time drift relative to the first object.

[0062] In a preferred embodiment, the method includes the synchronization of the times and / or clocks in the first and third objects, particularly wirelessly. Preferably, at least one time and / or clock synchronization and / or correction between the first and third objects is performed before, after, and / or during the execution of the method. This increases the accuracy of the method, as it allows drift to be determined and taken into account. Preferably, a drift of the clocks of the first and / or third object, or a difference in the drift of the clocks of the first and third object, is also determined and considered in the distance calculation. This further increases the accuracy of the method.

[0063] A particular advantage is that the distance between the first and at least one second object is determined without having to determine the distance between the first and third objects, and / or the distance between the first and at least one second object is determined independently of the distance between the first and third objects. This increases the speed and accuracy of the method.

[0064] The method is particularly advantageous when performed with a plurality, especially a common plurality greater than one, especially greater than two, especially greater than four, of two objects and common first and especially common second and third objects, wherein the calculated distances, especially between the first and each plurality of second objects, are preferably used to map and / or determine the position of the first object. By using several second and / or third objects, especially those arranged at a distance from one another, the reliability and accuracy can be increased, and localization, for example by means of triangulation, is possible.

[0065] The process is preferably carried out multiple times, whereby the at least one second and at least one third object can also exchange their roles, but the first object is common to all executions and / or constant. Thus, for example, from a plurality of objects, a changing portion of the plurality can always be second objects and another portion third objects.

[0066] Preferably, the majority of the two objects have a fixed position and / or orientation relative to each other, which is known and / or determined by radio direction finding. This allows, for example, simple triangulation to locate the first object.

[0067] Advantageously, the method is carried out using a system and / or access system according to the invention. Advantageously, the system or access system is configured to implement one or more advantageous embodiments of the method and, in particular, includes a correspondingly configured control system.

[0068] It is advantageous that the signal bandwidth never exceeds 50 MHz, and in particular 25 MHz. This saves energy, avoids interference with other processes, and allows the use of simpler components compared to broadband methods.

[0069] Advantageously, the signals are transmitted via multiple antenna paths, in particular with multiple antennas, especially sequentially, at the sending object and / or received with multiple antennas at the receiving object.

[0070] Preferably, the first and / or third object transmits the signals on several frequencies sequentially and / or consecutively, in particular immediately consecutively and / or the first and third object transmit alternately consecutively.

[0071] The distance is calculated, for example, as follows: The phases / amplitudes measured at the second object relative to the first object, depending on the carrier frequency, are corrected for the expected / calculated error resulting from the known time difference between the objects and the time drift of the two system clocks of the objects. These values ​​can then be evaluated, for example, using an FFT. Alternatively, vectors can be constructed (e.g., for different antenna paths) from which an autocorrelation matrix (AKM) can be generated. High-resolution methods, such as MUSIC or CAPON, can then be used to search for distances within this AKM.

[0072] Assuming phase-coherent frequency switching for the first and third objects, the following procedure can be used; otherwise, the calculation becomes somewhat more complicated: In particular, after determining the exact time differences and time drift between the third and first object and between the second and third object, the sufficiently accurate time difference between the first and second object can be calculated at any time for a limited period (e.g., 100 ms).

[0073] The IQ values ​​or phases / amplitudes of the second object are determined at at least 2 (up to n) frequencies (FO to Fn) of a signal from the first object.

[0074] In particular, the IQ values ​​or phases / amplitudes of the second object are determined on at least 2 (up to n) frequencies (FO' to Fn') of a signal from at least one third object.

[0075] If, for example, the switching times between frequencies FO to Fn' and / or FO to Fn and / or their temporal relationship are known, then, based on time synchronization with at least the third object, the switching times between the frequencies in FO' to Fn' can be determined by an object, for example, the first or second object. If the times of reception of the switching are then measured, propagation delays, in particular pulse propagation delay (ToF), can be directly determined from this.

[0076] By switching with or without a known phase shift, the frequency shift caused by the frequency change can also be measured directly. This applies to the signals from the first object as well as from at least one third object, which are received by the second object, and also partially by the first or third object. This alone allows the second object to determine the distance to both the first and the at least one third object, for example, by means of... Entfernung = dPhasenverschiebung f 1 , f 2 / 2 Pi / dFrequenz f 1 , f 2 * c with c equal to the speed of light and dphaseshift (f1,f2) equal to the measured change in phase shift at the receiver due to the frequency change from f1 to f2, corrected for the phase jump at the transmitter when switching from f1 to f2 and dfrequency(f1,f2) equal to the difference between the frequencies f1 and f2

[0077] The change in phase shift is primarily caused by the change in frequency, even at approximately the same distance. The phase shift is thus determined by the distance. The change in phase shift caused by the frequency change is due to the fact that, at approximately the same distance in both measurements, a different number of wave trains fit into the distance, resulting in different phase shifts between frequencies. This change in phase shift due to frequency is the phase shift caused by the frequency change. This leads to problems during measurement, as the phase measurement is always dependent on a reference, and a phase jump, often undefined, can occur when switching to transmit the different frequencies.Therefore, for transmitting, and especially for receiving, switching is preferably phase-coherent, i.e., with a phase shift of zero. However, it is also sufficient to determine or know the phase shift. Then, the phase shift caused by the frequency change can be determined by correcting the measured phase shift for the phase shift during the transmitter switchover and the phase shift during the receiver switchover to measure the measured phase shift.

[0078] If the switching times of the first and at least one third object exhibit a derivable, recognizable, communicated, and / or predetermined temporal relationship, which is preferred, further information can be obtained to improve the measurement. For example, if the switching times between frequencies of the at least one third object are known to the at least second object and / or are made aware of them, which is preferred, it can determine the switching times of the frequencies of the first object from the relationship between the switching times, at least as a function of the distance between the first and at least one third object, leading to a further improvement.

[0079] If the second object (or at least) knows the switching times between frequencies of the first object and / or is made aware of them, which is preferred, it can directly determine the propagation time (pulse propagation time, ToF) of the signal from the first to the second object and thus the distance. However, even based solely on the frequency switching of the signals emitted by the first object, with or without a known phase shift, the distance can be directly determined by the second object, for example, as shown above using: Distance = dPhaseshift(f1,f2) / 2π / dFrequency(f1,f2) * c

[0080] To increase accuracy (except for, e.g., FO), the measured phase shifts (Ph) can be adjusted for time differences and / or frequency differences (including drift). It is sufficient to approximate the drift. Determining this drift is known from the prior art and can be done, for example, by determining the time differences at various times, such as before and after the signal exchange for distance measurement.

[0081] The point in time at which the clocks are synchronized may differ, for example, it may not coincide with the transmission time. The calculation can then be adjusted accordingly.

[0082] To resolve multipathing, for example, the individual phases with their associated measured amplitudes can be entered as complex values ​​into a Fourier transform, or a spectral estimation can be performed in matrices using super-resolution methods such as MUSIC or CAPON.

[0083] Fig. 1 The diagram shows, purely as an example and only schematically and without limitation, a car with several second objects (2) and a third object (3) arranged inside, as well as a first object (1) designed as a key fob. During the execution of the procedure, the distances between the first and each second object are determined. If the time synchronization between the third and second objects is achieved, for example, via a cable, the second objects can be designed without transmitters and thus be passive or unlocatable.

Claims

1. A method for determining the distance, in particular directly, between a first and a second object (1, 2), wherein a first of the objects (1) transmits at least one first-object signal, in particular several first-object signals, at different first-object frequencies, and wherein said at least one second and at least one third object are clock- and / or time-synchronised, wherein said at least one second object transmits no signals other than for time synchronisation and / or said at least one second object transmits no signals used for distance determination and / or is passive apart from time synchronisation, characterised in that said at least one third object (3) transmits at least one third-object signal, wherein said at least one third-object signal has different third-object frequencies, and said at least one second object receives the first object signals from the first object and the third object signals from said at least one third object, and the distance between the first object and said at least one second object is determined based on the frequencies and phases of these received first object signals and third object signals, wherein the third object switches between at least two third-object frequencies in a phase-coherent manner and / or switches in such a way that the phase difference at the first and / or second object is known and / or the phase difference is made known to the first and / or second object, whereby knowledge of the phase shift during the frequency change is utilised, and / or whereby the first object switches phase-coherently between at least two of the first-object frequencies of said at least one first-object signal and / or switches in such a way that the phase difference at the second and / or third object is known and / or the phase difference is made known to the second and / or third object in a phase-coherent manner, wherein the knowledge of the phase jump is utilised during the frequency change.

2. A method according to claim 1, wherein the first object transmits at least one first-object signal before or after said at least one third-object signal, in particular each third object, wherein in particular the first object performs a signal exchange, in particular bidirectional frequency hopping, with said at least one, in particular each, third object, in which, in particular, each of the two objects involved in the signal exchange transmits, in a fixed and / or predetermined sequence, at least one signal, each having different frequencies, in particular a frequency hopping, and wherein, in particular, the first object in said at least one first-object signal and / or said at least one third object in said at least one third-object signal switches / switch between the different frequencies in a phase-coherent manner and / or switches / switch such that the phase difference during the frequency change, in particular at the second, first and / or at least one third object, is known and / or the phase difference during the frequency change, in particular at the second, first and / or third object, is made known.

3. A method according to any one of the preceding claims, wherein for first and / or third object signals received at said at least one second object, in particular for each received frequency and / or first and / or third object frequency and / or each frequency of the frequency hopping, a value proportional to their amplitude and a phase value are determined, and in particular a complex number is determined from each of these, which is used for determining the distance between the first and the second object, in particular by creating a vector from the complex numbers and / or an autocorrelation matrix, in particular for each received first and / or third object signal.

4. A method according to one of the preceding claims, wherein the second and said at least one third object are arranged in a fixed relative spatial position and / or orientation.

5. A method according to one of the preceding claims, wherein the first object is a remote authorisation device, such as a key fob or mobile phone, and wherein, in particular, the second and third objects form part of an arrangement to which access is sought and / or granted by means of the authorisation device, the arrangement being, in particular, a building, a motor vehicle or a barrier, a vending machine and / or a computer.

6. A method according to any of the preceding claims, wherein the third object receives said at least one first-object signal and / or provides information about said at least one received first-object signal, and this is used in the calculation of the distance, and / or wherein the first object receives the third-object signals and provides information about the received third-object signals, and / or this is used in the calculation of the distance.

7. A method according to any one of the preceding claims, wherein at least one of the objects determines at least one phase correction piece of information from a received first or third object signal, which is used in the distance calculation, in particular, the third object determines at least one phase correction parameter from the first object signals and / or the first object determines at least one phase correction parameter from the third object signals and / or the second object determines at least one phase correction parameter from the first and / or third object signals, and wherein said at least one phase correction parameter is used in the distance calculation.

8. A method according to one of the preceding claims, wherein the timings and / or the timing schedule of the transmissions of said at least one third-object and / or first-object signal and / or their characteristics are predetermined and / or are known to the second object and / or are taken into account in the distance calculation.

9. A method according to one of the preceding claims, wherein the method comprises synchronising the times and / or clock signals in the second and third objects, wirelessly or via a cable.

10. A method according to any of the preceding claims, wherein the distance between the first and second objects is determined without determining the distance between the first and third objects, and / or wherein the distance between the first and second objects is determined independently of the distance between the first and third objects.

11. A method according to any of the preceding claims, wherein the method is carried out according to one of the preceding methods with a plurality of second objects and with exactly one common first object and, in particular, at least one common third object, and wherein the calculated distances, in particular between the first object and the plurality of second objects, are used to perform mapping and / or positioning of the first object,12. A method according to claim 11, wherein, in particular, the plurality of second and / or third objects have a fixed position and / or orientation relative to one another.

13. A system comprising at least one first, one second, in particular a plurality greater than one, in particular greater than two, second objects (1, 2), and at least one third object (3), wherein the first object (1) is configured to transmit at least one first-object signal at different frequencies and wherein all objects are configured to receive signals, wherein said at least one second and the third object are configured to perform clock and / or time synchronisation, and wherein the system comprises at least one controller configured to perform the method according to the invention and thereby to determine at least one distance between at least one second object and the first object, characterised in that said at least one third object is configured to transmit at least one third-object signal at different third-object frequencies, and the second object is configured receiving the first-object signals of the first object and the third-object signals of the third object, and determining the distance between the first object and said at least one second object based on the frequencies and phases of these received first-object signals and third-object signals, wherein the third object is configured to switch between at least two third-object frequencies in a phase-coherent manner and / or to switch in such a way that the phase difference at the first and / or second object is known and / or the phase difference is made known to the first and / or second object, wherein knowledge of the phase shift upon a change in frequency is utilised, and / or wherein the first object is configured to switch phase-coherently between at least two of the first-object frequencies of said at least one first-object signal and / or to switch in such a way that the phase difference at the second and / or third object is known and / or the phase difference is made known to the second and / or third object, whereby knowledge of the phase shift upon frequency change is utilised.

14. An access system comprising at least one access control device, wherein the access control device is configured to grant and / or deny access, in particular by means of an access control means, further comprising the system referred to in claim 13.