Method for one-sided radio-based distance measurement
A method for one-sided radio-based distance measurement. The object is to speed up the determination of the distance between a first object and a second object, to enable greater accuracy and/or to enable or improve the determination, even in the event of interference, particularly in the case of one-sided and/or asymmetric interference in the radio connection. The method is carried out largely without radio signals in a transmission direction. The method includes use of a transit time measurement between the first object and the second object to eliminate the ambiguity of the distance measurement; the distance measurement being carried out on the basis of a change in the phase shift, in particular relative to the frequency change, of the signal propagation from the first object to the second object as a result of a frequency change.
1 . A method for distance determination between at least two objects, wherein the at least two objects are time- or clock-cycle-synchronized or at least one time- or clock synchronization or correction is carried out between the at least two objects, the method comprising the steps of:
emitting a plurality of signals by a first object of the at least two objects, wherein at least a first signal is emitted on a first frequency and at least a second signal is emitted on a second frequency different than the first frequency;
wherein for emitting the first signal and the second signal, the first object switches between the first frequency and the second frequency in a phase-coherent manner with a phase jump of zero, or changes so that upon changing frequencies, the phase jump is known or determined upon transmission;
receiving the plurality of signals emitted by the first object at a second object of the at least two objects and carrying out phase measurements on at least the first signal and the second signal upon receipt to determine a first phase value for the first signal and a second phase value for the second signal respectively;
performing a time-of-flight measurement based on knowledge of at least one point in time at which emission of features of the first signal or the second signal took place, thereby determining a distance estimate;
calculating a phase shift between the first phase value and the second phase;
determining a distance between the first object and the second object based on the phase shift between the first phase value and the second phase value in relation to a difference in frequency between the first frequency and the second frequency, the distance having an ambiguity; and
resolving the ambiguity in the distance by comparing the distance to the distance estimate determined by the time-of-flight measurement.
2 . The method according to claim 1 , wherein each signal of the plurality of signals that is received with an energy of less than 20% or more than 140% of a mean energy of all received signals of the plurality of signals is not used as either the first signal or the second signal for the distance determination.
3 . The method according to claim 1 , wherein the plurality of signals is emitted by the first object on multiple frequencies successively or consecutively.
4 . The method according to claim 3 , wherein a frequency spacing between two consecutive frequencies of the multiple frequencies is at least 0.1 MHz or a maximum of 17 MHz, or wherein the multiple frequencies span a frequency band with a bandwidth of at least two MHz or a maximum of 100 MHz.
5 . The method according to claim 4 , wherein at no time the bandwidth of the signals exceeds 50 MHz.
6 . The method according to claim 5 , wherein at no time the bandwidth exceeds 25 MHz.
7 . The method according to claim 3 , wherein the multiple frequencies are at least five frequencies or a maximum of 200 frequencies.
8 . The method according to claim 1 , wherein the at least one time- or clock-cycle synchronization or correction between the at least two objects is performed before, after or while performing the step of emitting the first signal and the second signal.
9 . The method according to claim 1 , wherein an accuracy of the time-of-flight measurement lies in a range from 0.3 m to 3 m.
10 . The method according to claim 1 , wherein a time drift of at least one or both of the at least two objects or between the at least two objects is determined or corrected or is taken into account for determining the distance.
11 . The method according to claim 1 , wherein a mean value for the distance between the first object and the second object is determined from multiple distance determinations performed using the first object and the second object.
12 . The method according to claim 11 , wherein the multiple distance determinations are performed using same or different first frequencies and same or different second frequencies.
13 . The method according to claim 1 , wherein each signal of the plurality of signals that is received at the second object with a received power below a predetermined or calculated lower power limit or above a predetermined or calculated upper power limit is not used as either the first signal or the second signal or are not taken into account for determining the distance.
14 . The method according to claim 1 , further comprising:
forming a plurality of object pairs;
wherein the at least two objects comprise more than one first object or more than one second object;
wherein each object pair of the plurality of object pairs comprises one first object and one second object, wherein all pairs of the plurality of pairs either comprise the same first object or comprise the same second object; and
wherein an individual distance between the respective first object and the second object is determined for each of the object pairs of the plurality of object pairs and the individual distances are used to carry out a mapping or position determination of the first objects and the second objects in relation each other.
15 . An object pair configured for carrying out the method according to claim 1 .
16 . The method according to claim 1 , further including the step of, prior to calculating the phase shift between the first and second phase value, modifying one or both of the first and second phase value based on the phase jump known or determined upon emitting.
17 . The method according to claim 1 , wherein one or both of the first and second signal received at the second object comprises more than one signal component, wherein, of said one or more signal components of respective first or second signals, signal components having an energy of less than 40% of a maximum energy of all of the respective signal components of said respective first or second signal are not taken into account for determining the distance.