Method for determining distance using high-resolution methods based on signal propagation time measurements

Description

[0001] The invention relates to a method for determining distances using high-resolution methods based on signal propagation time measurements.

[0002] It is known to determine distances from radio signals with high accuracy using mathematical methods, for example using MUSIC or CAPON or as known from EP 3 564 707, EP 3 502 736 A1 or EP 2 212 705.

[0003] EP2525238A1 and WO2020060686A1 describe systems for determining the distance between two devices. A distance estimation unit first extracts the phase of the frequency signals and then calculates a propagation delay between the two devices based on each extracted phase and estimates the distance.

[0004] However, these methods generally require phase measurements. The object of the invention is to enable such methods to be applied to pure time-of-flight measurements.

[0005] This is achieved by constructing complex numbers from propagation time measurements and amplitude measurements and / or propagation time measurements and power measurements, which provide an introduction to known methods. The problem is also solved by a method for determining the distance between two objects based on a plurality of radio signal propagation time measurements at a plurality of different frequencies between the two objects. The problem is also solved by using phase values for the different frequencies calculated from signal propagation time measurements between two objects at different frequencies and / or arguments of complex numbers for the different frequencies to determine a distance between the two objects using phase-based distance calculation methods and / or distance calculation methods based on complex numbers.

[0006] Such construction or extraction of phase values or arguments of complex numbers from a signal propagation time, in particular pulse propagation time (ToF), and their measurement instead of a phase measurement is thus carried out solely from pure propagation time measurements, in particular pulse propagation time measurements or ToF measurements. The complex number is obtained, in particular, solely on the basis of propagation time measurements, in particular pulse propagation time measurements or ToF measurements, as well as amplitude measurements and / or propagation time measurements, in particular pulse propagation time measurements or ToF measurements, and power measurements. In particular, phase measurements are therefore not necessary to construct, determine, or computationally obtain the complex numbers. In particular, no phase measurement of a radio signal is used to computationally obtain the complex number and / or the phase values.

[0007] Preferably, at least one first radio signal with a plurality of different frequencies is sent from a first object to a second object and received at the second object. Preferably, at least some or all of the radio signal propagation time measurements are performed on this at least one first radio signal. In a bidirectional embodiment, at least one second radio signal with a plurality of different frequencies is also sent from the second object to the first object and received at the first object. Preferably, at least some or all of the radio signal propagation time measurements are performed on this at least one second radio signal. In particular, the radio signal propagation time measurements are performed on the at least one first radio signal and the at least one second radio signal. In particular, the radio signal propagation time measurements are performed on radio signal components that have different frequencies.In particular, the at least one first radio signal and the at least one second radio signal form the at least one radio signal. In particular, at least one radio signal propagation time measurement is performed at each frequency of the at least one radio signal.

[0008] In particular, an amplitude and / or power measurement is also carried out on at least one radio signal during each radio signal propagation time measurement and / or on a similar signal part and / or in temporal proximity to each radio signal propagation time measurement.

[0009] For this purpose, at least one of the two objects preferably has means for transmitting the at least one radio signal, in particular means for generating the signal, means for amplifying the signal and / or means for radiating the signal, in particular at least one antenna. For this purpose, at least the other of the two objects also has means for receiving and measuring the at least one radio signal, in particular at least one antenna, and / or means for amplifying the received radio signal and / or means for determining the amplitude and / or power of the radio signal. In particular, the objects together have means for measuring the propagation time. For this purpose, in particular both objects have timers or clocks and the objects are in particular configured to align and / or compare and / or synchronize the clocks or timers.

[0010] The method according to the invention is particularly characterized in that phase values for different frequencies and / or arguments of complex numbers for different frequencies are determined from the radio signal propagation time measurements. This is done, in particular, computationally.

[0011] Phase values for different frequencies and / or arguments of complex numbers for different frequencies are particularly characterized by the fact that they can be used as phase measurement values or complex numbers in, in particular, previously known, mathematical methods for phase-based distance calculation to determine a distance between the two objects. In a preferred embodiment, the method also includes their use in, in particular, previously known, mathematical methods for phase-based distance calculation to determine a distance between the two objects and, in particular, also the calculation of the distance.

[0012] Particularly advantageously, in addition to the majority of radio signal propagation time measurements, amplitude and / or power measurements are also performed at the majority of different frequencies. A number proportional to the amplitude or power can be used as the amplitude or magnitude of the complex number in, in particular, known mathematical methods for phase-based distance calculation or mathematical methods based on complex numbers, or can be used to determine a distance between the two objects. This approach expands the possible applications of the method.

[0013] Preferably, radio signal propagation times of the radio signal propagation time measurements at frequencies, in particular adjacent frequencies of the plurality of different frequencies, are used to calculate a phase shift difference normalized to the spacing of the frequencies of the radio propagation time measurements. Preferably, the respective argument of the complex numbers at a frequency and / or the phase value at a frequency is assumed to be the phase shift difference summed up to this frequency, weighted by the frequency spacing.

[0014] Advantageously, for the radio signal propagation time measurement, at least one radio signal with a plurality of different frequencies is sent from a first of the two objects to a second of the two objects and / or vice versa, wherein in particular switching is carried out between at least two of the plurality of different frequencies in a phase-coherent manner and / or switching is carried out in such a way that the phase jump is known and / or measured at the transmitter. Advantageously, not only the transmitting object switches in a phase-coherent manner, but also the receiving object, in particular a PLL is switched in a phase-coherent manner in each object. The phase difference or phase jump usually arises when switching between two frequencies for technical reasons, but can also be avoided. The switching between two frequencies can be carried out with a short interruption or without interruption. At the time of the uninterrupted switch, the phase orDuring switching with an interruption, the phase of the signals imaginarily continued into the interruption jumps before and after the switching. At the switching point without an interruption or at an imaginary switching 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.

[0015] Phase-coherent switching or switching between two frequencies means, in particular, that the phase after switching is known relative to the phase position before switching. This is the case when the phase change during switching is zero or amounts to a previously known or determinable value. This avoids further phase measurements at the transmitter and simplifies the calculation, particularly when switching between frequencies without a phase change. Alternatively, switching can also be non-phase-coherent, and the phase change can be determined locally, in particular at the transmitter before transmission and / or at the receiver with respect to the receiver's PLL, and this change can be corrected in the calculation.

[0016] In some applications, the method can advantageously be carried out unidirectionally, which is a major advantage over originally phase-based measurements, which generally have to be carried out by bidirectional exchange. For example, it may be preferable for the radio signal propagation time measurements used for the method according to the invention to be carried out only on radio signals that are sent by a first of the two objects and received by a second of the two objects. The decision as to which radio signals are sent by the first or second object can be part of the method and is carried out in particular in such a way that the signals with less interference during reception are used. The decision can also be made separately for frequencies or frequency ranges. The decision can be made before or after the partial or complete transmission of the radio signals from the first to the second and / or from the second to the first object.

[0017] In some scenarios, the procedure is advantageously carried out in such a way that the second object does not send any signals for distance determination and / or the second object sends signals only for time and / or clock synchronization or is passive apart from time and / or clock synchronization.

[0018] Particularly advantageously, the method is carried out such that the first and / or second of the two objects emits the multiple frequencies consecutively and / or one after the other, in particular directly following one another, and / or wherein the bandwidth of the signals never exceeds 50 MHz, in particular 25 MHz. This allows for the use of simple components and minimizes interference.

[0019] Particularly preferably, at least one time and / or clock and / or time drift synchronization and / or correction between the two objects is performed before, after, and / or during the execution of the method. This increases accuracy. Advantageously, a time drift and / or a time drift difference between the two objects is determined and / or corrected for at least one of the two objects and / or taken into account when calculating the distance.

[0020] It is particularly advantageous if the frequency spacing between two consecutive different frequencies is selected to be at least 0.1 MHz and / or a maximum of 17 MHz, in particular a maximum of 10 MHz, and / or if the number of different frequencies is at least five frequencies and / or a maximum of 200 frequencies, and / or if the different frequencies span a frequency band of at least two MHz and / or a maximum of 100 MHz. This has proven sufficient in practice for high levels of accuracy and, on the other hand, requires only manageable complex structures and only acceptable frequency bands.

[0021] Advantageously, when determining the distance at the second or first object, radio signals received with a received power below a predetermined and / or, in particular, determined from or taking into account the received radio signals, lower power limit are disregarded. In particular, radio signals that are more than 50% below the average power of the received radio signals are disregarded. Alternatively or additionally, when determining the distance at the second or first object, radio signals received with a power above a predetermined and / or, in particular, determined from or taking into account the received radio signals, upper power limit are disregarded.

[0022] In another embodiment, from the signals selected in particular in the decision, the x% of the signals with the smallest received amplitude are sorted out and not used, and / or the y% of the signals with the largest received amplitude are sorted out and not used. It has proven particularly advantageous if the sum of x and y does not fall below 10 and / or does not exceed 75 and / or x is in the range from 10 to 75 and / or y is in the range from 20 to 50. With these values, high accuracy and reliable distance determination can be achieved in most situations.

[0023] If required, the method is advantageously carried out in such a way that the method is carried out between a plurality of pairs of objects, wherein in particular one object of each pair is an object that is involved in all pairs, and wherein the determined distances of the pairs are used to carry out mapping and / or position determination.

[0024] Advantageously, for each radio signal received at the second and / or first object, a value proportional to its amplitude or power and a phase value are determined and, in particular, a complex number is determined therefrom, which is used to determine the distance between the first and the second object.

[0025] The phase value or argument is determined, in particular, by calculating a phase shift change normalized to a frequency separation for a plurality of pairs of radio signals with, in particular, adjacent frequencies. This means approximately calculating the derivative of the phase shift at one or more frequencies of the pair. To do this, the phase shift for the frequencies of the respective pair is first calculated from the signal propagation time, which is directly possible using the relationship between frequency, wavelength, and propagation speed, for example, using the relationship: Phasenverschiebung = 2 Pi * 2 * Entfernung * Frequenz / c RTT = 2 * Entfernung / c and consequently: Phasenverschiebung = 2 Pi * RTT * c * Frequenz / c

[0026] Phase shift is a phase shift in the frequency transmission from one object to another and back, which occurs due to distance. It can be approximately equated to twice the phase shift that occurs in the frequency transmission from one object to another due to distance.

[0027] Then, or skipping this step, the preferred (normalized) phase shift changes (dphase shift) between two adjacent frequencies are determined, for example by means of dPhasenverschiebung f 1 , f 2 = Pi * RTT * c * dFrequenz f 1 , f 2 / c

[0028] The RTT can be used as twice the signal propagation time or the signal round trip time between the first and second object at a frequency similar to the frequencies f1 and / or f2, or an averaging of signal propagation times at similar frequencies.

[0029] Frequencies are considered to be similar in particular if they differ from each other by less than 17 MHz, in particular 9 MHz, in particular less than 2 MHz, and / or less than 5%, in particular less than 2%, of the lower frequency.

[0030] Frequency hopping refers in particular to successive transmission on different frequencies.

[0031] In particular, the frequencies, in particular of the frequency hopping, lie in a range from 25 to 100 MHz, in particular they completely span such a range. In particular, the frequencies, in particular of the frequency hopping, lie in the range from 2 to 6 GHz. In particular, there is a spacing in the range from 0.1 to 10 MHz, in particular in the range from 0.5 to 10 MHz, between adjacent but not necessarily consecutive frequencies, in particular of the frequency hopping. In particular, the frequencies between which a change in the phase shift is calculated have a spacing in the range from 0.1 to 10 MHz, in particular in the range from 0.5 to 10 MHz, in particular up to 2 MHz.

[0032] Adjacent frequencies are in particular the frequencies lying next to each other in the majority of different frequencies, in particular the frequencies lying next to each other that were transmitted by one of the objects, they are preferably similar.

[0033] The standardized phase shift change values collected in this way are preferably used to determine the phase of the complex number at the respective frequency (the value corresponding to the value proportional to the amplitude) and / or the phase values at the respective frequency, in particular by approximate integration over the frequency and / or weighted summation over the frequency. In this case, the integration or summation need not begin at f = 0 Hz; instead, an offset common to all complex numbers or phase values can and is preferably used, in particular the lowest frequency of the, in particular, selected, plurality of different frequencies.

[0034] In particular, the phase value is thus determined from the signal propagation time or signal round trip time.

[0035] In particular, the phase shift change (dPhaseshift(fb,fa)) is obtained using the formula: dPhaseverschiebung fb fa = k 1 * RTT fm * dFrequenz fb fa or dPhaseverschiebung fb fa = k 2 * STT fm * dFrequenz fb fa where dFrequency(fb,fa) is the difference between the frequencies fb and fa, RTT(fm) is twice the signal propagation time or the signal round trip time or STT(fm) is half the signal propagation time or half the signal round trip time between the first and second object at one or more frequencies fm, similar to fb and / or fa and / or vice versa, and where k1, k2 is each a constant, in particular equal to Pi and k2 is equal to 2 Pi.

[0036] f(m) is the frequency at which the propagation time measurement was performed, fb and fa are two frequencies chosen such that fb is not equal to fa and fb is similar to fa and fm. In particular, fb is greater than fa and / or fa is less than fm and / or fb is greater than fm. No measurements are required for fb and fa. These, or rather the expected change in phase shift between them, are calculated from the measurement at fm using the formula above.

[0037] The complex value Z for a frequency is then determined in particular by: Amount(Z(f)) = (k3* Amplitude(fm) + offset), with f similar to fm and as close as possible to fm and preferably uniformly as large or small as possible as fm or as an average value of amplitudes at neighboring and / or similar frequencies with offset a constant, in particular equal to 0 and / or k3 a constant, in particular equal to 1.

[0038] The phase shift changes are summed from the lowest frequency to the frequency in question for which the complex number is to be determined. The lowest frequency is approximately the same, in particular identical, for all complex numbers. Furthermore, the phase shift changes are always summed for consecutive frequency pairs where the higher frequency is approximately the same, in particular identical, to the lower frequency of the next pair, i.e., in particular mit f = f n + 1 f0 is approximately the same for all complex numbers of a vector and / or a matrix, in particular equal.

[0039] The narrower the steps of the real measurement, i.e. the available fm, the smaller the step size can be chosen in the sequence f0 to f and the more accurate the method is.

[0040] For example, we measure as follows F1 STT1 (STT = signal propagation time) F2 STT2 F3 STT3 F4 STT4 ... ... Fn STTn

[0041] And if the distance between the neighboring frequencies is equidistant with the distance 2d, then F1 + 2 * d = F2, F2 + 2 * d = F3 etc. Then one can form: dPhaseverschiebung F 1 + d , F 1 − d = k 1 * 2 * STT F 1 * 2 d , generally dPhaseverschiebung Fn + d , Fn − d = k 1 * 2 * STT Fn * 2 d ,

[0042] Then you form, for example, Betrag Z fn + d = k 3 * Amplitude Fn + offset and

[0043] If the distances are not equidistant, the frequencies fa and fb are selected as the lowest frequency, in particular slightly below the lowest measurement frequency, and then continuously ascending frequencies, in particular midway between the ascending measurement frequencies. k1 is in particular constant equal to Pi and / or k3 is in particular equal to 1 and / or offset is in particular equal to 1.

[0044] The constants are identical, especially for the calculation of all complex numbers of a vector or matrix.

[0045] The complex numbers are combined to form a complex vector, which is composed of the complex numbers as row or column values. An autocorrelation matrix is then created from the complex vector. This can then be used for known distance determination methods based on such an autocorrelation matrix, such as CAPON, MUSIK, or virtual distance calculations based on radiation or reception characteristics, especially groups of matrices.

[0046] As described above, the phase shift changes are summed up from the lowest frequency or a fixed starting frequency to the frequency in question for which the complex number or the phase value equal to the argument of the complex number is to be determined.

[0047] In particular, a matrix, in particular an autocorrelation matrix, is formed from a plurality of complex numbers, and the distance is determined using this matrix and, in particular, using known methods, for example, MUSIC, CAPON, comparison with, distance calculation based on, and / or projection onto radiation and / or reception characteristics. Advantageously, the distance calculation is carried out by determining the eigenvalues or eigenvectors of the at least one matrix and / or by Fourier transformation of the complex values.

[0048] Such approaches are particularly advantageous in multipath signal propagation to achieve reliable determination.

[0049] The calculation can be illustrated as follows: All signal round trip times or double signal transit times (RTT) are converted into a phase shift and then phase shift differences or phase shift derivatives are determined for pairs of phase shifts: dPhasenverschiebung f 1 , f 2 = 2 Pi * 2 * Entfernung * dFrequenz f 1 , f 2 / c RTT = 2 * Entfernung / c dPhasenverschiebung f 1 , f 2 = 2 Pi * RTT * c * dFrequenz f 1 , f 2 / c

[0050] Here, dphase shift is the phase shift difference between two frequencies f1 and f2, which are separated by dfrequency. c is the speed of light.

[0051] Then the calculated phase shift differences are summed: sumPh(Fn) = sum dPh(FO... Fn) to obtain the phase values.

[0052] FO to Fn are the several different frequencies.

[0053] These summed phase shift differences, along with the corresponding amplitudes determined during reception, can then be input as complex values into a Fourier transform, or they can be used to estimate the spectrum in matrices using super-resolution methods (e.g., MUSIC or CAPON). The spectrum is then the spectrum of paths of varying length that the signal travels before arriving at the receiving antenna in superposition. In this case, it is particularly advantageous to use multiple antenna paths during transmission and to include them in the analysis.

[0054] In principle, it is preferable to use several, in particular at least three, preferably at least four, different antenna paths, in particular one after the other, for the radio signal propagation time measurements. An antenna path is characterized by the antennas used for transmitting and receiving. For example, if a first antenna is used for transmitting at the first object and a second antenna is used for receiving at the second object, this is a first antenna path. If the antenna used for transmitting at the first object is then changed to a third antenna at the first object, a different, second, antenna path is used. The radio signal propagation time measurements are advantageously carried out, in particular one after the other, with different antennas at the first and / or second object.

[0055] Fig. 1 shows a possible embodiment of the method according to the invention in a schematic, exemplary and non-limiting manner.

[0056] The described method begins with the transmission of radio signals from object A to object B at frequencies f0 to fn. The frequencies are switched between in a phase-coherent manner without phase jumps. The receiver also switches between frequencies in a phase-coherent manner without phase jumps.

[0057] Time of flight and amplitude measurements are made on the received radio signals at object B. Equivalent phase shifts are calculated from the time of flight or using these or directly, using dPhasenverschiebung f 1 , f 2 = Pi * RTT f 3 * c * dFrequenz f 1 , f 2 / c

[0058] Phase shift changes.

[0059] Here, dphase shift is the phase shift difference between two frequencies f1 and f2 separated by dfrequency. c is the speed of light, and RTT is twice the signal propagation time at frequency fe, similar to f1 and / or f2.

[0060] Based on this, the phases phi for all fO to fn are calculated using phi f 0 = 0 and phi fc = Summe phi f 0 bis phi fc − 1 + dPhasenverschiebung fc − 1 , fc

[0061] From this, complex numbers Z(f0) to Z(fn) are created with Betrag Z fd = A fd and Argument Z fd = phi fd

[0062] The distance between object A and B is then calculated based on Z(f0) to Z(fn).

Claims

1. Method for determining the distance between two objects on the basis of a plurality of radio signal propagation time measurements at a plurality of different frequencies, in particular a frequency hopping, between the two objects, characterised in that phase values for different frequencies and / or arguments of complex numbers for different frequencies are determined from the radio signal propagation time measurements, which can be used as phase measurement values in mathematical methods for phase-based distance calculation and / or arguments of complex numbers in mathematical methods for complex distance calculation or are used to determine a distance between the two objects.

2. Method according to claim 1, wherein amplitude and / or power measurements at the plurality of different frequencies are also made to the plurality of radio signal propagation time measurements, wherein a number proportional to the amplitude or power can be used as the amplitude or magnitude of the complex number in known mathematical methods for phase-based distance calculation or are used to determine a distance between the two objects.

3. Method according to one of the preceding claims, wherein radio signal propagation times of the radio signal propagation time measurements at, in particular neighbouring ones of the plurality of different, frequencies are used to calculate a phase difference normalised to the spacing of the frequencies of the measurements of the radio propagation times and the argument of the complex numbers at a frequency and / or the phase value at a frequency is given by phase differences summed up to this frequency.

4. Method according to claims 2 and 3, wherein a vector and / or an autocorrelation matrix is formed from the complex numbers, wherein in particular a distance between the two objects is calculated from the vector and / or the autocorrelation matrix.

5. Method according to one of the preceding claims, wherein at least one radio signal with the plurality of different frequencies is transmitted from a first of the two objects to a second of the two objects and / or vice versa for the radio signal propagation time measurement, wherein in particular switching between at least two of the plurality of different frequencies takes place in a phase-coherent manner, in particular at the transmitting object and received object.

6. Method according to any one of the preceding claims, wherein the radio signal propagation time measurements are performed only on signals transmitted by a first one of the two objects and received at a second one of the two objects.

7. Method according to one of the preceding claims, wherein the second or first object does not transmit signals for distance determination and / or the second object transmits signals only for time and / or clock synchronisation.

8. Method according to one of the preceding claims, wherein the first and / or second of the two objects radiates the signals at several frequencies one after the other and / or success-sively, in particular directly successively, and / or wherein the bandwidth of the signals does not exceed 50 MHz, in particular 25 MHz, at any time.

9. Method according to one of the preceding claims, wherein at least one time and / or clock and / or time-drift synchronisation and / or correction is performed between the two objects before, after and / or during the performance of the method.

10. Method according to one of the preceding claims, wherein the frequency spacing between two successive ones of the different frequencies is at least 0.1 MHz and / or at most 10 MHz and / or the different frequencies represent at least five frequencies and / or at most 200 frequencies and / or wherein the different frequencies span a frequency band of at least two MHz and / or at most 100 MHz.

11. Method according to one of the preceding claims, wherein a time drift of at least one of the two objects is determined and / or corrected and / or taken into account in the calculation of the distance.

12. Method according to one of the preceding claims, wherein, when determining the distance at the second or first object, signals received with a received power below a predetermined lower power limit and / or, in particular, determined from or taking into account the received signals, are not taken into account, in particular signals which are more than 50% below the average power of the received signals are not taken into account and / or wherein, when determining the distance at the second or first object, signals received with a power above a predetermined upper power limit and / or, in particular, determined from or taking into account the received signals, are not taken into account.

13. Method according to any one of the preceding claims, wherein the method according to any one of the preceding methods is performed between a plurality of pairs of objects, wherein in particular one object of each pair is an object participating in all pairs, and wherein the determined distances of the pairs are used to perform mapping and / or position determination.

14. Use of phase values computed from radio signal propagation time measurements between two objects at different frequencies for the different frequencies and / or arguments of complex numbers for the different frequencies to determine a distance between the two objects by means of phase-based distance calculation methods and / or distance calculation methods based on complex numbers.

15. Use according to claim 14, wherein radio signal propagation time measurements originate from a plurality of different antenna paths.