Method and configuration for evaluating the distance between at least two antenna units

Abstract

A method for estimating a distance between at least a first antenna unit and a second antenna unit by bidirectional transmission of at least two signals having different circular polarizations between the antenna units, where phase information is determined and used to determine at least a first phase sum and a second phase sum, which are utilized to determine at least one distance indicator indicative of a distance between the first antenna unit and the second antenna unit.

Description

[Technical Field]

[0001] This invention generally relates to wireless communication and localization. More specifically, the invention relates to evaluating the distance between at least a first antenna unit and a second antenna unit by bidirectional transmission of at least two signals having different circular polarizations between antenna units. Background of the Invention

[0002] Systems and methods involving signal transmission, such as wireless signals, from a first (transmitting) device to a second (receiving) device are used in many applications, such as tracking and various purposes where distance measurement is required. In some systems, the distance between two devices can be evaluated by alternately using the first and second devices as transmitter and receiver. In this case, the phase of one or more transmitted signals received by the receiving device may be determined and used for distance measurement. However, such measurements present many complex problems, and obtaining accurate results regarding the distance between devices can be time-consuming or even impossible.

[0003] One problem relates to signal reflection. Reflections of transmitted signals from other objects reaching the receiving device may be indistinguishable from signals received directly from the transmitting device. When determining the phase of the received signal relative to the receiving device's local oscillator and then determining the distance or phase length from that phase, the determined distance or phase length can be affected by the reflected signal and may be erroneous. Distinguishing between the original transmitted signal and the reflected signal is particularly difficult when the reflection occurs in a direction close to the direction of the original signal. In such cases, the reflected signal has almost the same delay as the original signal, making it virtually indistinguishable from the original signal in spatial or temporal signal processing. However, in applications requiring extremely high distance measurement accuracy, such signal phase distortion is detrimental.

[0004] Polarized signals can be used for transmission to reduce or eliminate the effects of reflection. Circularly polarized signals are known to be particularly advantageous in that they can reduce the effects of reflected signals from metal surfaces. Metal surfaces are the most problematic reflective surfaces when using linearly polarized signals. Reflections from metal surfaces (or other surfaces with similar reflection coefficients) inherently alter the polarization of the signal. Therefore, if the receiving antenna is configured to receive only the circularly polarized version of the original signal, the reflected signal will not be received, or at least will be strongly attenuated. Furthermore, circularly polarized signals can reduce the effects of reflections from other types of surfaces even if the polarization of the reflected signal is not perfectly circular.

[0005] However, the use of circularly polarized signals presents several problems. Rotation along the line-of-sight (LOS) axis between antenna units affects phase measurements and, consequently, the determination of distances between antenna units. For example, in geodetic GNSS, the problem of rotation along the LOS axis between the transmitter and receiver is attempted to be resolved by using a joint solution of rotation angles and position coordinates, along with the derivative with respect to a nearby reference station. However, this requires a large number of satellites to solve the problem, making this solution impractical for ground systems where only a small number of antenna units are available to track the position of a moving radio device. Furthermore, reference antennas may be impractical for ground navigation. [Overview of the project]

[0006] The object of the present invention is to alleviate at least some of the problems of the prior art. According to one interpretation of the present invention, a method is provided for evaluating the distance between at least a first antenna unit and a second antenna unit. This method includes at least, - Transmitting a first signal having first circular polarization through the first antenna unit; The second antenna unit receives the first signal; The second antenna unit determines first phase information indicating the phase of the received first signal with respect to the local oscillator of the associated wireless unit; - Transmitting a first response signal that essentially matches the first signal through the second antenna unit; The first antenna unit receives the first response signal; - To determine first response phase information indicating the phase of the received first response signal with respect to the local oscillator of the wireless unit associated with the first antenna unit; • To determine a first phase sum that represents the sum of the first phase information and the first response phase information; Transmitting a second signal having a second circular polarization opposite to the first circular polarization through either the first antenna unit or the two antenna units; The second signal is received by the other of the first antenna unit or the second antenna unit; The antenna unit that receives the second signal determines second phase information indicating the phase of the received second signal with respect to the local oscillator of the associated radio unit; Transmitting a second response signal that is essentially consistent with the second signal through the first antenna unit or the other of the second antenna unit that does not transmit the second signal; The antenna unit that transmitted the second signal receives the second response signal; The antenna unit that receives the second response signal determines second response phase information indicating the phase of the received second response signal with respect to the local oscillator of the associated radio unit; • To determine a second phase sum that represents the sum of the second phase information and the second response phase information; • Determining at least one distance index indicating the distance between the first antenna unit and the second antenna unit based on at least the first phase sum and the second phase sum; Includes.

[0007] Alternatively, the present invention also relates to configurations as defined in independent claim 13.

[0008] The present invention enables the highly accurate determination of at least one distance index indicating the distance between antenna units based on determined phase information. The accuracy of the determined distance index can be high enough to evaluate or determine the distance between a first antenna unit and a second antenna unit with sub-millimeter accuracy. However, the absolute distance measurement accuracy depends on the accuracy of the phase measurement at the carrier frequency converted to wavelength in meters. The present invention relates to the determination of phase information and subsequent operations via one or more distance indexes, thereby enabling the determination of highly accurate absolute distances. However, the determination of absolute distances is not a constituent element of the invention specified in the claims. Various methods that may be used to obtain such absolute distance measurements are not discussed in detail herein.

[0009] This invention enables high-precision measurements using cost-effective antenna units. This solution uses circularly polarized antenna units and signals to mitigate the effects of reflection in phase measurements and compensate for rotation between antenna units and, in some cases, changes in the antenna phase center (which is a function of the signal direction). Without these corrections and compensations enabled by this invention, if centimeter-wave radio were used for distance measurement, the accuracy of the determined distance would at best be at the centimeter level.

[0010] The present invention may be useful for any application of evaluating or monitoring one or more distances. Configurations according to the present invention may be used, for example, in systems for tracking objects, or other location tracking, indoor positioning systems, etc. Object tracking may be performed, for example, by tracking changes in distance between a first antenna unit associated with a reference position and a second antenna unit associated with or coupled to an object.

[0011] The antenna units that can be used may be of lower quality than those used in, for example, geodetic GNSS measurements. Antenna units used in geodetic GNSS measurements are selected to eliminate the problem of phase center fluctuation, and such high-quality antenna units are expensive. However, in the present invention, a simpler and less expensive circularly polarized antenna unit can be used. Therefore, the configuration according to the present invention can be implemented and used inexpensively.

[0012] The present invention allows for compensation or elimination of the effect of rotation between the first and second antenna units along the LOS axis in determining a distance index between antenna units (or at least their reference points) (in the distance potentially determined thereafter). This leads to a more accurate assessment of the distance than without compensation. With respect to the distance between the first and second antenna units, it may be understood that the distance can be determined or assessed through a distance index that can be used to determine the phase length indicating the distance between the antenna units. Assessment of the distance does not necessarily mean that the absolute distance is determined, but as will be understood by those skilled in the art, the distance may be assessed through knowledge of the phase length that gives a known fractional part of the wavelength of the total distance between the antenna units. Determination of the absolute perfect distance between antenna units may then involve further calculations, for example, of integer ambiguity, but these are not described herein.

[0013] Furthermore, it may be possible to evaluate the distance between antenna units using only the first and second antenna units. That is, it may be sufficient to evaluate the distance (or at least a distance index) with satisfactory accuracy using only the antenna units for which the link distance or baseline distance is being evaluated. Consideration of separate reference antenna units or congruent solutions may not be necessary. (In congruent solutions, multiple satellites or antenna units are observed, and a solution is determined that fits the data obtained from them.) Depending on the embodiment, calibration data for the standard antenna pattern of the antenna unit can be obtained. However, this data may be previously determined data, or only data relating to antenna units that are structurally similar to the first and / or second antenna unit may be required.

[0014] The at least one distance index may have a first distance variable that represents the sum of a first phase sum and a second phase sum. By using this first distance variable, it may be possible to eliminate rotation between the first and second antenna units along the LOS axis in determining the distance index. The distance index and the (determinable) distance may be determined completely independently of the rotation.

[0015] The direction of the signal data with respect to the coordinate systems of the first and second antenna units may be obtained. The direction of the signal data may be used in determining the at least one distance index. In particular, depending on the embodiment, the direction data may be used in determining the at least one distance index by obtaining antenna phase pattern calibration data and interpolating the antenna phase response.

[0016] The transmitted signal may be received by at least three different antenna elements provided in the first antenna unit and / or the second antenna unit in order to determine the direction of the signal data.

[0017] Embodiments of the above method may include determining self-measurement data indicating the phase of the self-measurement signals for the first and second polarizations, received by the transmitting antenna unit during signal transmission. The self-measurement data may be used to determine at least one distance index.

[0018] The at least one distance index may include a rotation variable indicating the difference between the first phase sum and the second phase sum. The method may, depending on the embodiment, include determining the rotation angle between the first antenna unit and the second antenna unit based on the rotation variable. Thus, it is also possible to explicitly determine the rotation angle. The rotation variable may be determined at least once and then used in tracking the rotation angle between the first antenna unit and the second antenna unit. Subsequent first signals and first response signals may be transmitted to determine a subsequent first phase sum for tracking the distance between the first antenna unit and the second antenna unit. Thus, it is possible to track the distance index at a high rate with a single polarization measurement without transmitting a signal with a second polarization, and even if a signal including a second polarization is transmitted, it may only be at a low rate.

[0019] Each of the at least first and second antenna units may transmit at least one signal within a predetermined time slot, preferably in a predetermined order. In some embodiments, the first antenna unit may be a master unit, and the remaining at least the second antenna units may be slave units. The master unit may be configured to transmit the first signal, which may be configured to check whether a radio channel is available for transmission before transmitting the first signal in each measurement cycle, and to transmit at least the first signal if the radio channel is available, and not to perform the transmission if the radio channel is not available.

[0020] In an embodiment having a master and slave antenna unit, before transmitting a signal in a predetermined measurement cycle, the slave unit determines whether the previous antenna unit in a predetermined order of the antenna units transmitted a signal in the predetermined measurement cycle. If it is determined that a signal was transmitted, the slave unit transmits its signal. On the other hand, if it is determined that the previous antenna unit did not transmit a signal, the slave unit may be configured not to transmit its signal.

[0021] In some embodiments, the first signal may also be received by at least a third antenna unit. The third antenna unit may also be configured to transmit a first response signal, which may be received by at least the first antenna unit and / or the second antenna unit, and in some embodiments, by all other antenna units that did not transmit the first response signal. The second signal may also be received by at least the third antenna unit, and the third antenna unit may be configured to transmit a second response signal. This second response signal may be received by at least the first antenna unit and / or the second antenna unit. Thus, at least two sets of antenna units that perform bidirectional transmission of a signal having at least a first polarization and a signal having a second polarization may be obtained. For each set of antenna units, respective phase information, a first phase sum, and a second phase sum may be determined. Therefore, for each set of antenna units, at least one distance indicator indicating the distance between the antenna units may be determined, and at least two distances between the antenna units may be evaluated.

[0022] The novel features believed to be characteristic of the invention are set forth particularly in the appended claims. However, the construction and method of operation of the invention, together with additional objects and advantages thereof, will be best understood from the following description of specific illustrative embodiments read in conjunction with the accompanying drawings.

[0023] As those skilled in the art will understand, the considerations presented above regarding various embodiments of the method can be flexibly applied to embodiments of the apparatus, and vice versa. [Brief explanation of the drawing]

[0024] Next, the present invention will be described in more detail with reference to exemplary embodiments shown in the accompanying drawings. [Figure 1] An exemplary configuration according to one embodiment of the present invention is schematically shown. [Figure 2] Further exemplary configurations according to one embodiment of the present invention are shown. [Figure 3] A first antenna unit and a second antenna unit according to one embodiment of the present invention are shown. A circularly polarized signal is also shown. [Figure 4] The orientations of the first and second antenna units along the connecting lines, and the electrical vector reference directions (as unit vector e) of both antenna units and their LCP and RCP feeds are shown. [Figure 5] This shows the first wireless unit, the first antenna unit, the second wireless unit, and the second antenna unit. [Figure 6] An exemplary wireless unit and antenna unit that may be used in embodiments of the present invention are shown. [Figure 7] This shows the allocation of time slots in the measurement cycle. [Figure 8] This is a flowchart of a method according to one embodiment of the present invention. [Figure 9] This is a message sequence chart of a method according to one embodiment of the present invention. Detailed description

[0025] Figure 1 schematically shows a configuration 100 according to one embodiment of the present invention. This configuration has at least a first antenna unit (AU) 104 and a second antenna unit 106, which are associated with a first radio unit 108 and a second radio unit 110, respectively. The antenna units 104 and 106 may be located within the radio units 108 and 110, or they may be coupled to the radio units, for example, via cables. The antenna units may have one or more antennas, which are not shown in detail in Figure 1. An exemplary antenna unit is depicted in more detail in Figure 3.

[0026] Configuration 100 may also have a number of other antenna units and radio units, such as a third radio unit and a fourth radio unit. Each set of antenna units transmits and receives one or more signals between the antenna units. These antenna units can be thought of as being separated by a baseline or distance D. This baseline or distance D generally refers to the distance between antenna units or at least between their reference points. A reference point is a point on an antenna unit, such as the geometric center on the antenna unit plane with respect to the antenna element positions, which can be simply considered as the point at which signal transmission or reception occurs. In a given configuration, the distance between each set of antenna units can be evaluated.

[0027] The wireless units 108 and 110 are coupled to at least one processing unit 102. The processing unit 102 may be a controller unit located outside the wireless units 108 and 110, may be implemented as a microprocessor unit, or may be provided as part of a larger computing device such as a personal computer. However, depending on the embodiment, the processing unit 102 may be located inside the wireless units 108 and 110, or may be considered as part of the wireless units 108 and 110.

[0028] The processing unit 102 may be configured to control the wireless units and / or antenna units of the configuration 100. The processing unit 102 may receive data from the antenna units 104, 106 or the wireless units 108, 110 and may use such received data in any information decisions performed. The processing unit 102 may also have, or access, one or more databases or memory units containing additional data. Such additional data may include, for example, complex (amplitude and phase) antenna gain pattern and antenna phase pattern calibration data for one or more antenna unit types.

[0029] Additionally or alternatively, the processing unit 102 may be configured to receive data from the antenna units and / or wireless units of configuration 100 via a wired (e.g., Ethernet) or wireless (e.g., WLAN) method. Figure 2 shows an embodiment of configuration 100 in which the processing unit 102 is wirelessly coupled to wireless units 108, 110. The processing unit 102 may also be associated with the processor antenna unit 112.

[0030] The processing unit 102 and the wireless units 108 and 110 can receive power using, for example, PoE (Power-over-Ethernet), a direct mains power supply, a battery, a solar panel, or a mechanical generator (such as a wind turbine blade).

[0031] Depending on the embodiment, in configuration 100, in addition to the processing unit 102, which may be a locally provided processing unit, a processing unit located at a remote location may be used. Alternatively, the processing unit 102 may be implemented as a remote processing unit that does not require a local processing unit. The remote processing unit can receive any of the obtained data and, for example, perform at least part of the data determination performed by configuration 100. The remote processing unit may refer to a processing unit that can be accessed via cloud computing. Alternatively, the remote processing unit may refer to a virtual processor configured in multiple locations, which can be configured to perform the processing presented herein through parallel processing means.

[0032] The first antenna unit 104 is configured to transmit a first signal having at least a first circular polarization. The first circular polarization may be, for example, left-hand circular polarization (LCP). The first signal and subsequent transmitted signals may be radio frequency signals (RF signals). These signals may be unmodulated RF signals (i.e., sine waves), combs of RF sine waves over a predetermined frequency range, or RF signals modulated by any known (complex) sequence.

[0033] The frequencies of the first signal and subsequent signals may be, for example, less than 10 GHz. However, configuration 100 is not limited to any frequency range. For example, 60 GHz may be used. In the case of high frequencies, the quality of the local oscillator (LO) of the radio unit may be a factor to be considered. For example, to use a frequency of 60 GHz, an oscillator of, for example, 5 PPB would provide sufficient quality.

[0034] The frequencies used for at least the first signal, the first response signal, the second signal, and the second response signal should essentially match each other. If the configuration is set up to transmit a subsequent signal (to determine subsequent phase information indicating the distance between antenna units in subsequent time), the signal frequency may be the same as, for example, the one used for the first signal, or the frequency may be varied.

[0035] The duration of the first signal (and subsequent signals transmitted by either the radio unit or antenna unit of configuration 100) may be between 10 μs and 10,000 μs, depending, for example, the distance between the antenna unit or radio unit, the time interval of the measurement cycle, and / or the quality of the local oscillators provided by the radio units 108, 110 in terms of path loss. The duration of the signal may be, for example, about 100 μs.

[0036] It should be noted that, depending on the system, time variations in the signal throughout the measurement sequence, i.e., phase rotation, may be compensated for. Such phase rotation can be caused by the frequency difference of the local oscillator or the movement of the antenna unit (Doppler). Estimation and compensation for the frequency difference of the local oscillator or Doppler may be performed using additional signals (e.g., time-repeating signals), but this technique is well known and is outside the scope of this invention.

[0037] The first signal is received by the second radio unit 110 through the second antenna unit 106. Based on the received first signal, at least first phase information related to the first signal is determined. This first phase information indicates the phase of the received first signal with respect to the local oscillator of the second radio unit 110.

[0038] More precisely, the signal frequency is usually higher than the local oscillator frequency, and phase measurements are often performed in the digital baseband using methods such as the Fast Fourier Transform (FFT). This is essentially equivalent to measuring the phase of a local oscillator that, for simplicity's sake, is assumed to operate at the signal frequency.

[0039] If the configuration 100 has further radio units and antenna units, such as a third radio unit associated with a third antenna unit, the first signal may also be received by the third radio unit (through the third antenna unit), and the first phase information may also be determined by the third (and other) radio units.

[0040] A configuration having two or more antenna units may be used to determine the relative positions between antenna units. The relative distance may be determined multiple times to track or monitor changes in distance. For example, the relative distance may be determined multiple times to track a three-dimensional shape including three or more antenna units. Embodiments of the configuration may be used, for example, in terrestrial positioning.

[0041] The second wireless unit 110 is configured to transmit at least a first response signal through the second antenna unit 106. The first response signal may be equivalent to the first signal, or may essentially match the first signal, at least in frequency and polarization.

[0042] The first response signal is received by the first radio unit 108 through the first antenna unit 104. Based on the received first response signal, at least first response phase information is determined. This first response phase information indicates the phase of the received first response signal with respect to the local oscillator of the first radio unit 108.

[0043] Next, the first phase information and the first response phase information are used (by the processing unit 102) to determine at least a first phase sum which represents the sum of the first phase information and the first response phase information.

[0044] Furthermore, if the configuration includes additional wireless and antenna units, for example, a third antenna unit may also be configured to transmit a signal matching the first response signal. This signal may be received by at least the first antenna unit, preferably by all other antenna units that did not transmit the first response signal, and in each of the antenna units that received the first response signal, a first response phase information relating to the received first response signal may be determined. Of course, the third antenna unit may receive the first response signal transmitted by the second antenna unit 106 and determine its own phase information. Thus, multiple first phase sums may be determined.

[0045] The first wireless unit 108 may also be configured to transmit at least a second signal having a second circular polarization through the first antenna unit 104. The second circular polarization may differ from the first circular polarization and may be, for example, right-hand circular polarization (RCP).

[0046] The second signal may be received by the second radio unit 110 through the second antenna unit 106. Based on the received second signal, at least second phase information related to the second signal is determined. This second phase information indicates the phase of the received second signal with respect to the local oscillator of the second radio unit 110.

[0047] The second wireless unit 110 may be configured to transmit at least a second response signal through the second antenna unit 106. The second response signal may be equivalent to the second signal, or it may be essentially identical to the second signal, at least in frequency and polarization.

[0048] The second response signal is received by the first radio unit 108 through the first antenna unit 104. Based on the received second response signal, at least second response phase information is determined. This second response phase information indicates the phase of the received second response signal with respect to the local oscillator of the first radio unit 108.

[0049] The second signal is transmitted by the second antenna unit and received by the first antenna unit. The second response signal is transmitted by the first antenna unit and received by the second antenna unit. If the transmission sequence (which antenna unit transmits which signal) is known, time dependence due to Doppler shift may be corrected.

[0050] Next, the second phase information and the second response phase information are used to determine at least a second phase sum, which represents the sum of the second phase information and the second response phase information.

[0051] Based on the first and second phase sums, at least one distance index may be determined that indicates the distance D between the first antenna unit 104 and the second antenna unit 106 (or at least the distance between their reference points). At least some of the candidate distance indexes may be independent of the rotation angle between the LOS axes of the antenna units, as will be described later.

[0052] Therefore, configuration 100 has at least one pair of antenna units that transmit and receive at least two signals and their response signals to each other, and enables the determination of bidirectional phase information and its sum through bidirectional transmission.

[0053] In embodiments of configuration 100 including further radio units and antenna units, such as a third radio unit and an associated third antenna unit, the further antenna unit may be configured to receive a second signal and optionally a second response signal transmitted by at least a second antenna unit 108, determine the respective second phase information, and transmit the second response signal. Thereafter, a plurality of second phase sums may be determined, and a plurality of distance indicators may be determined (for each evaluated distance, based on a plurality of first phase sums and second phase sums).

[0054] Any antenna unit in the configuration may be configured to receive some or all of the signals transmitted by the other antenna units in the configuration. In some embodiments, each transmitting antenna unit may broadcast its signal in a predetermined time slot, and the other antenna units may receive that signal.

[0055] Accordingly, the configuration may have multiple antenna units, and may include a set of antenna units configured to perform bidirectional transmission of first and second signals having a first polarization and first and second response signals having a second polarization. In order to obtain a first phase sum and a second phase sum for each set of antenna units that transmit and receive the first and second signals having the first polarization and transmit and receive the first and second response signals having the second polarization, bidirectional phase information may be determined for each of the received transmitted signals. In this way, multiple distance indicators may be determined. Each of these distance indicators represents the distance between antenna units in a particular set of antenna units.

[0056] In some embodiments, each transmitting antenna unit may transmit at least one signal within a predetermined time slot, and furthermore, the first antenna unit may be a master unit and the second antenna unit (and the rest) may be slave units. The master unit may be an antenna unit configured to transmit the first signal. The master unit may be configured to check whether a radio channel is available for transmission before transmitting the first signal. It may then be configured to transmit at least the first signal if the channel is available, and not to transmit the first signal if the channel is not available.

[0057] The master unit may check whether a radio channel is available before transmitting the first signal, and if yes, it may continue the measurement cycle, and the radio channel may be reserved by configuration for at least one measurement cycle. That is, the configuration can advantageously utilize a radio band / channel that requires a Listen Before Talk (LBT) function. If it is determined that the radio channel is not available, the first signal may not be transmitted, and the measurement cycle itself may be stopped or canceled without transmitting a signal. The master unit or the first antenna unit may then wait for a predetermined time between measurement cycles. Then, in the next measurement cycle, it may check again whether the radio band is available, and if the radio band is available, it may transmit the first signal to start the measurement cycle.

[0058] In embodiments having a master antenna unit and one or more slave antenna units, each slave unit may determine, before transmitting a signal in a predetermined measurement cycle, whether the previous antenna unit in a predetermined sequence transmitted a signal in the measurement cycle. If yes, the slave unit transmits the signal; however, if it determines that the previous antenna unit did not transmit a signal, i.e., no valid measurement signal was received, it may be configured not to transmit the signal (i.e., to wait for a complete measurement cycle).

[0059] In some configuration embodiments, at least a first antenna unit may transmit a time-synchronized signal, which will be received by at least the remaining wireless antenna units, before transmitting the first signal. Time synchronization allows the antenna units to perform synchronous signal transmission, taking into account time slots related to a predetermined order in which the signals should be transmitted. Such synchronous signal transmission may be performed particularly in embodiments where the time between measurement cycles in subsequent measurement cycles is relatively long, such as one minute or more.

[0060] The information processing and steps performed may be in a different order than those proposed herein. For example, the first signal may be the RCP signal and the second signal may be the LPC signal.

[0061] In some embodiments, the first signal and the second signal may be transmitted before the first response signal and the second response signal.

[0062] In other embodiments of the present invention, the first signal and the second signal may be transmitted simultaneously (and therefore in the same time slot). The first response signal and the second response signal may be transmitted simultaneously, either additionally or alternatively. In the simultaneous transmission of multiple signals, each having left or right circular polarization, coded transmission is utilized.

[0063] Figure 3A shows exemplary first antenna unit 104 and second antenna unit 106 that configuration 100 according to an embodiment of the present invention may have. Here, both antenna units 104 and 106 each have four antenna elements. The first antenna unit 104 has a first antenna element 114, a second antenna element 116, a third antenna element 118, and a fourth antenna element 120. The second antenna unit 106 has a first antenna element 122, a second antenna element 124, a third antenna element 126, and a fourth antenna element 128. Depending on the embodiment, the first and second antenna units may each have a different number of antenna elements. The antenna units 104 and 106 may have only one dual-polarization antenna element in association with an antenna element having high phase center stability with respect to the signal direction.

[0064] If the antenna elements do not have high phase performance, the antenna units 104 and 106 preferably each have at least three antenna elements 114, 116, 118, 120, 122, 124, and 126. In this case, the direction of arrival of the signal may be determined. In particular, it is preferable that the direction of arrival of the signal is determined when the phase centers of the antenna elements are not constant.

[0065] If antenna units 104 and 106 have multiple antenna elements 114, 116, 118, 120, 122, 124, and 126, all antenna elements of an antenna unit preferably receive signals transmitted by the other antenna unit in the antenna unit combination consisting of antenna units 104 and 106. Some or all of the multiple antenna elements of an antenna unit may transmit, for example, a first signal and / or a second signal. However, it would be more efficient if all antenna elements were used to receive signals, but only one antenna element was used to transmit them.

[0066] In the example shown in Figure 3A, for the first antenna unit 104, the first antenna element 114 may be a transmit / receive (TX / RX) antenna element, while the second antenna element 116, the third antenna element 118, and the fourth antenna element 120 may be receiving antenna elements. For the second antenna unit 106, the first antenna element 122 may be a transmit / receive (TX / RX) antenna element, while the second antenna element 124, the third antenna element 126, and the fourth antenna element 128 may be receiving (RX) antenna elements.

[0067] The first antenna unit 104 and the second antenna unit 106 may each have at least one RCP feed and one LCP feed. Each antenna element may also have either a single polarization feed or a multiple polarization feed. It is preferable that the TX / RX elements 114 and 122 have feeds for both polarizations.

[0068] Figure 3A also shows the reference point P1 of the first antenna unit and the reference point P2 of the second antenna unit. The measurements to be performed can be simplified to be performed at the reference points. Reference points P1 and P2 can be considered to be connected by a connecting line X (LOS axis), the length of which corresponds to the distance D between the antenna units.

[0069] The LOS axis X forms an angle β with the plane on which the antenna unit lies, for example, the plane x1,y1 of the first antenna unit 104. The projection of the LOS axis X onto the plane x1,y1 forms an angle α with the x1 axis. These angles α and β can be obtained by direction of arrival (DOA) measurement. The axis z1 represents the normal to the surface of the first antenna unit 104.

[0070] The rotation of the antenna unit relative to the LOS axis X cannot be determined or evaluated using the DOA method. However, when using circularly polarized signals, this rotation affects the determination of phase information, and therefore needs to be considered in order to obtain more accurate phase information.

[0071] Figure 3B shows, as an example, a circularly polarized signal transmitted from a first antenna 104 having a first antenna element 114 (not shown). This signal can be received by a second antenna unit 106 having a first antenna element 122. For simplicity, only the first antenna elements 114 and 122 are considered. Figure 3B shows the transmission of a circularly polarized signal to demonstrate that a rotating antenna unit affects the signal and the determined phase. As will be understood by those skilled in the art, for example, the rotation of the first antenna unit 104 relative to the second antenna unit 106 affects the phase of the received signal at the second antenna unit 106. Thus, even though the distance D between the antenna units remains the same, the determined phase information and the determined distance index, and therefore the distance D to be evaluated, are affected.

[0072] Figure 4 shows the directions of the first and second antenna units along the LOS axis, assuming the connecting line (LOS axis) is perpendicular to the page. These directions are based on the unit vector of the normal of the first antenna unit. TIFF0007836839000001.tif2656 and the unit vector of the normal of the second antenna unit It is drawn based on TIFF0007836839000002.tif2656. The electrical vector reference direction of both antenna units and their LCP feeds and RCP feeds is also unit vector. It is shown as TIFF0007836839000003.tif2656. For example, TIFF0007836839000004.tif2656 corresponds to the direction of the unit vector of the LCP feed of the first antenna unit 104. Later, the signs of the terms refer to the case where the first antenna unit 104 is below the second antenna unit 106 along the page normal.

[0073] Figure 5 shows the first wireless unit 104, the first antenna unit 104, the second wireless unit 110, and the second antenna unit 106. In this example, the first antenna unit 104 includes antenna elements corresponding to the first antenna element 114 and the fourth antenna element 120 in Figure 3. The second antenna unit 106 includes antenna elements corresponding to the first antenna element 122 and the fourth antenna element 128. The TX / RX switch in Figure 4 is assumed to be in the "TX" position.

[0074] The following describes the case where the first antenna element 114 of the first antenna unit transmits the first and second signals, which are received by the fourth antenna element 128 of the second antenna unit, and the first antenna element 122 of the second antenna unit transmits the first and second response signals, which are received by the fourth antenna element 120 of the first antenna unit. If antenna units 104 and 106 have two or more antenna elements, similar considerations apply to the other antenna elements. Individually determined information, such as phase information and / or distance indicators, may be combined to obtain information (such as distance indicators) corresponding to the information about the corresponding reference points of antenna units 104 and 106.

[0075] The first antenna unit 104 may transmit a first signal, for example, with LCP polarization, through the first antenna element 114 during its own time slot (time T1). The phase of the transmitted signal received by the second antenna unit 106 through the fourth antenna element 128, i.e., the first phase information to be determined, is as follows.

[0076] TIFF0007836839000005.tif26170

[0077] Here, TIFF0007836839000006.tif2656 and TIFF0007836839000007.tif2656 represents the phases of the local oscillators of the first radio unit 108 and the second radio unit 110 at the transmission time T1 of the first radio unit 108. Note that the subscripts represent antenna units, not antenna elements. Φ 12 This is the geometric phase corresponding to the distance, baseline, or connecting geometric line between the transmitting antenna element 114 of the first antenna unit 104 and the receiving antenna element 128 of the second antenna unit 106. TIFF0007836839000008.tif2656 is the phase length of the transmitting branch (transmitting section) corresponding to the first antenna unit 104. TIFF0007836839000009.tif2656 is the phase length of the receiving branch (receiving section) corresponding to the second antenna unit 106. (Here, phase length refers to the phase shift that occurs in a signal traversing a certain distance.)Ψ LCP As shown in Figure 4, the electrical vector reference plane (X and The plane formed by TIFF0007836839000010.tif2656 and the electrical vector reference plane (X and This is the angle between the planes formed by TIFF0007836839000011.tif2656.

[0078] Phase length of the transmit branch and receive branch, for example TIFF0007836839000012.tif2656 and TIFF0007836839000013.tif2656 includes the phase length resulting from the physical lengths of the transmit and receive branches of the antenna unit and associated radio unit, and may also include the cable length. For example, as seen in Figure 5, the phase length TIFF0007836839000014.tif2656 corresponds to the length of the transmit branch of the first radio unit 108 from the digital-to-analog converter (DAC) to the transmit antenna 114. It should be noted that the phase length between the DAC and the mixer corresponds to a much lower frequency (baseband frequency) than the phase length between the mixer and the antenna. The phase length from the local oscillator to the mixer must also be considered. Here, all of these effects are considered. Assume it is included in the entry for TIFF0007836839000015.tif2656.

[0079] Following the reception of the first signal by the second antenna unit 106, the second antenna unit 106 transmits a first response signal by the first antenna element 122. This first response signal may be received by the fourth antenna element 120 of the first antenna unit in its time slot (time T2). The first response phase information, determined or measured in relation to the first antenna unit received (at the fourth antenna element 120), is as follows, assuming that the second antenna unit 106 transmitted the response signal in zero phase with respect to its local clock / oscillator:

[0080] TIFF0007836839000016.tif26170

[0081] Here, TIFF0007836839000017.tif2656 and TIFF0007836839000018.tif2656 represents the phase of the LO of the second radio unit 110 and the first radio unit 108 at the transmission time T2 of the second radio unit 110. For simplicity, the following processing will consider the phase relationship between radio nodes 108 and 110. It is assumed that TIFF0007836839000019.tif2656 remains the same between transmissions. Normally, this does not happen because radio nodes have independently operating clocks. However, with a reasonably good clock, the rate of change of this phase relationship is constant over time and can be easily determined by repeated measurements, and therefore easily corrected. Φ 21 This is the geometric phase corresponding to the distance between the transmitting antenna, in this case the first antenna element 122 of the second antenna unit, and the receiving antenna, in this case the fourth antenna element 120 of the first antenna unit. TIFF0007836839000020.tif2656 and TIFF0007836839000021.tif2656 represents the transmit and receive branch phase lengths corresponding to the second antenna unit 106 and the first antenna unit 104, respectively. Ψ LCP This is as previously defined. Here, we assume that the rotation between antenna units 104 and 106 does not change significantly between transmissions. This is a valid assumption, given that the typical time between transmissions is on the order of 100 microseconds.

[0082] Subsequently, a second signal having RCP polarization may be transmitted from the first antenna element 114 of the first antenna unit (in a time slot allocated at time T3) and received by the fourth antenna element 128 of the second antenna unit. The second phase information to be determined is as follows: TIFF0007836839000022.tif26170

[0083] Here, Ψ RCP As can be seen from Figure 4, Ψ LCPThis is similar, but for RCP feed. The second response signal is transmitted by the first antenna element 122 of the second antenna unit and received by the fourth antenna element 120 of the first antenna unit in that time slot at time T4. The second response phase information to be determined is as follows:

[0084] TIFF0007836839000023.tif26170

[0085] Branch topology terms, for example TIFF0007836839000024.tif2656 may be removed by self-measurement data or self-calibration data indicating the phase of the self-measurement signal received by the transmitting antenna unit during signal transmission. For example, when the first antenna element 114 of the first antenna unit transmits the first signal, the fourth antenna element 120 of the first antenna unit may determine the first self-measurement phase as follows. TIFF0007836839000025.tif26170

[0086] When the first antenna unit 104 transmits the second signal, the self-measured phase information may be determined as follows. TIFF0007836839000026.tif26170

[0087] Here, TIFF0007836839000027.tif2656 represents the phase of the signal transfer function between the first antenna element 114 (transmitting antenna element) of the first antenna unit and the fourth antenna element 120 (receiving antenna element) of the first antenna unit. A stable phase term like TIFF0007836839000028.tif2656 can be measured for a single antenna unit, for example, in an anechoic chamber. This measurement data may be used to remove the influence of the stable phase term on self-calibration phase data such as TIFF0007836839000029.tif2656. (However, it is assumed that it is approximately the same for all similar antenna units.) For this reason, antenna unit i TIFF0007836839000030.tif2656 may be omitted or compensated for in further calculations. The second antenna unit 106 may similarly determine its own measured phase information.

[0088] The first topological sum S1 is determined as follows:

[0089] TIFF0007836839000031.tif26170

[0090] On the other hand, the second topological sum S2 is as follows:

[0091] TIFF0007836839000032.tif26170

[0092] In particular, if the transmit and receive branches are stable, their lengths are known, and it is known that they are being corrected somewhere, the phase sum can be calculated without self-measured phase information.

[0093] However, if the configuration has multiple antenna units, each transmitting antenna unit may determine its own self-calibration / self-measurement phase information.

[0094] As can be seen from Figure 4,

[0095] TIFF0007836839000033.tif26170 and

[0096] The filename is TIFF0007836839000034.tif26170.

[0097] Here, Ω is the rotation angle along the LOS axis between the first antenna unit 104 and the second antenna unit 106. TIFF0007836839000035.tif2656 and TIFF0007836839000036.tif2656 is the z-axis and electrical reference vector measured along the LOS axis (signal direction) for antenna unit i and its respective polarization feed. TIFF0007836839000037.tif2656 and This is the angle between TIFF0007836839000038.tif2656 and the file. TIFF0007836839000039.tif2656 and TIFF0007836839000040.tif2656 can also be understood as the phase response of each polarization feed in a given direction.

[0098] As a distance index, the first distance variable VD may be determined based on the first and second topological sums S1 and S2, for example, as their sum. Using the above,

[0099] TIFF0007836839000041.tif51170

[0100] Assuming no significant change in rotation during transmission, we can see that the rotation Ω between the antenna units cancels out. This is a safe assumption for tracking typical objects such as a forklift, given that the time between transmissions is on the order of 100 microseconds. Thus, the geometric phase length between the reference points of the first and second antenna units is 1 / 2(Φ). 12 +Φ 21 ) may be determined from the sum of self-calibrated phase measurements. For example, it can be easily derived from equation (11) using a first distance variable VD.

[0101] Remaining feed-specific phase response parameters TIFF0007836839000042.tif2656 and TIFF0007836839000043.tif2656 It depends on the signal direction. When the antenna unit has good phase performance, that is, when the antenna phase center is independent of the signal direction and is essentially constant, the following can be written for antenna unit i.

[0102] TIFF0007836839000044.tif26170

[0103] As a result, Φ 12 The phase lengths such as can be directly derived from the (self-calibrated) phase sums S1 and S2 as can be seen from Equation (13).

[0104] However, when the approximate formula (12) does not hold, in order to obtain antenna phase pattern calibration data, for example, in an anechoic chamber, the phase response of the antenna feed TIFF0007836839000045.tif2656 and TIFF0007836839000046.tif2656 can be measured. Such calibration data may be obtained by measurement, obtained from an external source, or stored in a database. Although it is very common in mass production, assuming that the produced antenna units are sufficiently similar to each other, these antennas may be assumed to have essentially similar patterns at their feeds. If the direction of the signal (α,β) is known in the antenna unit coordinate system, TIFF0007836839000047.tif2656 and TIFF0007836839000048.tif2656 may be interpolated from the stored antenna phase pattern calibration data, and also, in order to obtain 1 / 2(Φ 12 +Φ 21 ) indicating the distance between the antenna unit reference points from the (preferably self-calibrated) phase sum measurement values, it may be used as follows.

[0105] TIFF0007836839000049.tif26170

[0106] Some examples of determining the direction (direction of arrival) of a signal include the following: 1) Apply a direction-of-arrival algorithm (such as beamforming or subspace-based methods like MUSIC) to the signals received by multiple receiving antennas. 2) Track the position and orientation of the antenna unit. Or a combination of these.

[0107] The interpolation of the antenna phase response with respect to the signal direction determined from antenna phase pattern calibration data may be modeled based on well-known techniques. For example, it may be modeled based on vector spherical harmonics, or based on a 2D-FFT-based decomposition calculated from measurement data.

[0108] In yet another embodiment, the rotation angle Ω can also be explicitly determined. This can be done by determining the rotation variable VR as a distance index. The rotation variable VR can be determined by forming the difference of the phase sum as follows: TIFF0007836839000050.tif26170

[0109] The Ψ term, which depends on the direction of the signal, can be determined as described above. From this, the rotation angle Ω between the antenna units can be determined from the (self-calibrated) phase sum.

[0110] TIFF0007836839000051.tif26170

[0111] The advantage of explicitly determining Ω is that it can be tracked in estimation algorithms such as Kalman estimation and particle estimation. The estimated value can be used to remove rotational effects in single-polarization measurements.

[0112] TIFF0007836839000052.tif51170

[0113] With this configuration, by transmitting only the first signal and the first response signal having the first polarization, without transmitting a signal having the second polarization, and determining the first phase sum, it becomes possible to track the rapidly changing geometric phase length with a single polarization measurement. The first phase sum may be determined at a selected first time interval (e.g., 70-300 times per second, 100-250 times, or 150-200 times per second), and the geometric phase length may be determined therefrom as follows.

[0114] TIFF0007836839000053.tif26170

[0115] The slowly changing rotation angle Ω may be tracked using an estimator employing less frequent dual-polarization measurements. In this case, signals with first and second polarizations (first signal, first response signal, second signal, and second response signal) may be transmitted at a selected second time interval (e.g., between 1 and 30 times or 1 and 10 times per second).

[0116] Figure 6 shows exemplary radio units 108, 110 and antenna units 104, 106 having four antenna elements, which may be used in embodiments of the present invention. Radio units 108, 110 in Figure 6 may be used in embodiments in which self-calibration and / or signal direction measurement is performed.

[0117] Figures 7A and 7B illustrate how time slots may be allocated in a measurement cycle for signal transmission and / or, optionally, data communication in configuration 100. A measurement cycle may represent a set of signals to be transmitted, or it may represent a time duration over which signals are transmitted successively such that the interval between transmissions is less than a threshold. A first measurement cycle may include, for example, the transmission (and reception) of a first signal, a first response signal, a second signal, and a second response signal. In some embodiments, a second measurement cycle may be performed. A second measurement cycle may be, for example, equivalent to the first measurement cycle.

[0118] A single measurement cycle may include at least one measurement frame (having N measurement slots). During the measurement frame, at least the first antenna unit 104 and the second antenna unit 106 may transmit their respective signals separately in the time slots assigned to them. The measurement cycle in Figure 7A is applicable to a configuration 100 having N radio units, and the distance between each antenna unit may be evaluated. Each antenna unit may transmit its respective signal in its respective time slot.

[0119] Transmissions may be performed so that no empty time slots remain between transmissions, with transmissions occurring in subsequent time slots. Transmissions and time slots may be balanced such that the time interval between the end of a transmission and the start of the subsequent time slot in which the subsequent antenna unit begins transmitting is less than or equal to the selected maximum time interval. The time interval between the end of a transmission and the start of a subsequent transmission may be less than 50 μs, preferably less than 20 μs, for example less than 16 μs, between transmissions occurring within the same measurement frame.

[0120] However, there may be long time intervals between measurement frames, from the end of one transmission to the start of the next. In such cases, the master unit may be configured to check whether a transmission channel is available at the start of each measurement frame.

[0121] The compact transmission signal supply is advantageous because it can be used in combination with, for example, a Wi-Fi network. In this invention, the wireless channel for transmission only needs to be reserved once per measurement cycle. This feature can enable compatibility with networks such as Wi-Fi.

[0122] If no transmission occurs in a subsequent time slot, it may take a longer, unpredictable amount of time to complete the measurement cycle. This is because, for example, on radio channels that require channel competition only once, as defined in ETSI EN 301 893 (a standard specification regulating 5GHz Wi-Fi transmission), one measurement cycle cannot be effectively performed as one transmission. During transmission, each transmitting antenna unit must compete for the channel separately, so if the channel is occupied by another user during transmission, the measurement sequence can become considerably longer.

[0123] Figure 7B shows how time slots are allocated in a measurement cycle that also employs at least one communication frame (having one or more communication slots). During the communication frame, signals, measurement / determination data, or other data may be transmitted to the processing unit 102. At least one data communication may be transmitted and multiplexed in the time domain or frequency domain with the measurement signal transmitted by the wireless unit. At least one data communication may include at least determined phase information. Additionally or alternatively, the data communication may include any other information. Thus, configuration 100 can function simultaneously as a measurement system and a communication network.

[0124] The required time synchronization accuracy should ideally be better than one-quarter of the duration of the possible guard time between subsequent signals in order to prevent transmission duplication.

[0125] Figure 8 is a flowchart of one embodiment of the present invention. In 802, at least a first signal having a first polarization is transmitted by the first antenna unit (AU) 104. In 804, this first signal is received by at least a second antenna unit (AU) 106 and at least first phase information is determined. The first signal transmitted by the first antenna unit 104 may also be received by any other antenna units of the configuration 100, and first phase information relating to the phase of the received first signal with respect to the local oscillator of the receiving antenna unit may be determined. In 806, at least one first response signal is transmitted by at least a second antenna unit 106. The first response signal essentially matches the first signal. The first response signal may also be transmitted through any third or other antenna units of the configuration, each antenna unit preferably transmits the signal in its own predetermined time slot, preferably in a predetermined order. In 808, the first response signal is received by at least the first antenna unit 104, and the first response phase information is determined. Any transmitted signal may also be received by an antenna unit that did not transmit it, and phase information may be determined for each. If self-calibration information is also to be determined, the signal may also be received by the receiving antenna of the antenna unit that transmitted it.

[0126] In 810, at least one first phase sum is determined with respect to at least the first antenna unit 104 and the second antenna unit 106. The first phase sum may be the sum of first phase information and first response phase information. The first phase sum may be determined for any or all of the pairs of antenna units that transmitted bidirectional signals between them.

[0127] In 812, a second signal having at least a second polarization is transmitted to an antenna unit. The second signal may be transmitted by the first antenna unit 104, the second antenna unit 106, or any other AU in the configuration. In 814, the second signal is received by at least one other antenna unit that did not transmit the second signal, and at least a second phase information is determined. The second signal transmitted by any of the antenna units may also be received by any other antenna units in the configuration 100, and a second phase information relating to the phase of the received second signal with respect to the local oscillator of the receiving antenna unit may be determined. In 816, at least one second response signal is transmitted by at least one of the other antenna units that did not transmit the second signal. The second response signal essentially matches the second signal. The second response signal may also be transmitted through another antenna unit (that did not transmit the second signal). These antenna units preferably transmit the second response signal in their own predetermined time slots, preferably in a predetermined order. In 818, the second response signal is received by at least one of the antenna units to determine the second response phase information.

[0128] In 820, at least one second phase sum is determined with respect to at least the first antenna unit 104 and the second antenna unit 106. The second phase sum may be the sum of the second phase information and the second response phase information. The second phase sum may be determined for any or all of the pairs of antenna units that transmitted bidirectional signals between them.

[0129] In 822, at least one distance index is determined. This distance index indicates at least the distance between the first antenna unit 104 and the second antenna unit 106. At least one distance index may be determined for each pair of antenna units that transmitted a bidirectional signal between them with respect to the first and second polarizations, i.e., a signal comprising at least a first signal, a first response signal, a second signal, and a second response signal.

[0130] Figure 9 shows a message sequence chart relating to at least a portion of a method according to one embodiment of the present invention. Figure 9 relates to a configuration and method including N antenna units 104, 106, and depicts signal and data transmissions that may be performed. Each antenna unit is associated with radio units 108, 110, and a radio unit may be associated with one or more antenna units. For example, the first antenna unit 104 and the second antenna unit 106 may be associated with the same radio unit, or may be considered to be contained within the same radio unit. In the embodiment of Figure 9, the first antenna unit 104 transmits a first signal at time T1. The first signal may be received by at least some of the other antenna units of the configuration 100. Figure 9 shows that the first signal is received by the second antenna unit 106, the third antenna unit 902, and the Nth antenna unit 904.

[0131] The second antenna unit 106 may be configured to transmit a first response signal at time T2, and this signal may be received by at least some or all of the other antenna units of configuration 100. The third antenna unit 902 may also be configured to transmit a first response signal at time T3, and this signal may be received by at least some of the other antenna units of configuration. Figure 9 also shows that antenna unit N transmits a first response signal at time TN, and this signal is received by at least the first antenna unit 104, the second antenna unit 106, and the third antenna unit 902.

[0132] At time TN+1, the first antenna unit 104 may be configured to transmit a second signal. In other embodiments of the present invention, the second signal may be transmitted by one of the other antenna units in the configuration. It has been shown that the second response signal is transmitted by the second antenna unit (time TN+2), the third antenna unit (time TN+3), and the Nth antenna unit (time T2N).

[0133] Each of the radio units 108, 110 (the first radio unit 108, the second radio unit 110, and / or any further radio units of configuration 100) may determine at least a first phase information, a first response phase information, a second phase information, and / or a second response phase information. Figure 9 shows that the determined phase information is transmitted to the processing unit 102 at time T2N+1. The processing unit 102 may then determine at least a first and a second phase sum in relation to each set of antenna units. It may also determine at least one distance index.

[0134] The present invention has been described above with reference to the embodiments described above, and several advantages of the present invention have been demonstrated. The present invention is not limited to these embodiments, but includes the spirit and scope of the invention, as well as all possible embodiments within the scope of the following claims.

[0135] Unless otherwise specified, the features described in the dependent claims may be freely combined with each other.

Claims

1. A method for evaluating the distance between at least a first antenna unit and a second antenna unit, - Transmitting a first signal having first circular polarization through the first antenna unit; - The second antenna unit receives the first signal; - To determine first phase information indicating the phase of the received first signal with respect to the local oscillator of the wireless unit associated with the second antenna unit; - Transmitting a first response signal that essentially matches the first signal through the second antenna unit; - The first antenna unit receives the first response signal; - To determine first response phase information indicating the phase of the received first response signal with respect to the local oscillator of the wireless unit associated with the first antenna unit; - To determine a first phase sum that represents the sum of the first phase information and the first response phase information; - Transmitting a second signal having a second circular polarization opposite to the first circular polarization through either the first antenna unit or the two antenna units; - Receiving the second signal with the other of the first antenna unit or the second antenna unit; - The antenna unit that receives the second signal determines second phase information indicating the phase of the received second signal with respect to the local oscillator of the associated wireless unit; - Transmitting a second response signal that is essentially consistent with the second signal through the first antenna unit or the other of the second antenna unit that is not transmitting the second signal; - The antenna unit that transmitted the second signal receives the second response signal; - The antenna unit that receives the second response signal determines second response phase information indicating the phase of the received second response signal with respect to the local oscillator of the associated wireless unit; - To determine a second phase sum that represents the sum of the second phase information and the second response phase information; - Determining at least one distance index indicating the distance between the first antenna unit and the second antenna unit based on at least the first phase sum and the second phase sum; Methods that include...

2. The method according to claim 1, wherein the at least one distance index includes a first distance variable that represents the sum of a first phase sum and a second phase sum.

3. To obtain the direction of the signal data relating to the coordinate systems of the first antenna unit and the second antenna unit; The direction of the signal data is used in determining the at least one distance indicator; The method according to claim 1, including the method described in claim 1.

4. The method according to claim 3, wherein the transmitted signal is received by at least three different antenna elements provided in the first antenna unit and / or the second antenna unit in order to determine the direction of the signal data.

5. The phase information, the phase sum, and / or the distance index are determined with reference to the reference point of the first antenna unit and / or the second antenna unit. The aforementioned reference point is the geometric center of the positions of two or more antenna elements of each antenna unit, and is the geometric center on the plane of the antenna unit. The method according to claim 1.

6. The method according to claim 1, comprising determining self-measurement data indicating the phase of the self-measurement signals for the first circular polarization and the second circular polarization received by the transmitting antenna unit during the transmission of a signal, and using the self-measurement data when determining at least one distance index.

7. The method according to claim 1, wherein the at least one distance index includes a rotation variable that indicates the difference between the first phase sum and the second phase sum.

8. The method according to claim 7, wherein the rotation variable is determined at least once and then used in tracking the rotation angle between the first antenna unit and the second antenna unit, the method comprising transmitting a subsequent first signal and a subsequent first response signal to determine a subsequent first phase sum, and the rotation variable is used to compensate the rotation angle between the first antenna unit and the second antenna unit in order to track the distance between the first antenna unit and the second antenna unit.

9. The method according to claim 1, wherein each of the at least first antenna unit and the second antenna unit transmits at least one signal in a predetermined order within a predetermined time slot.

10. The method according to claim 9, wherein the first antenna unit is a master unit, and at least the remaining second antenna units are slave units, the master unit is configured to transmit a first signal, and the master unit is configured to check whether a radio channel is available for transmission before transmitting the first signal in each measurement cycle, and transmit at least the first signal if the radio channel is available, and not perform the transmission if the radio channel is not available.

11. The method according to claim 10, wherein the slave unit is configured to determine whether the antenna unit preceding it in a predetermined order of antenna units has transmitted a signal in the predetermined measurement cycle before transmitting a signal in the predetermined measurement cycle, and if it determines that the antenna unit has transmitted a signal, it transmits a signal from the slave unit, and if it determines that the preceding antenna unit has not transmitted a signal, it does not transmit a signal from the slave unit.

12. A method comprising evaluating at least two distances between a plurality of antenna units, wherein the evaluation is at least - The first signal is received by at least the third antenna unit; - Transmitting a first response signal through the third antenna unit and receiving the first response signal with at least the first antenna unit; - The second signal is received by at least the third antenna unit; - Transmitting a second response signal through the third antenna unit and receiving the second response signal with at least the first antenna unit; This includes obtaining at least two sets of antenna units that perform bidirectional transmission of at least one signal having the first circular polarization and the other signal having the second circular polarization, and further, - To determine the phase information for each set of antenna units; - Determine the first phase sum and the second phase sum for each set of antenna units; - For each set of antenna units, determine at least one distance index indicating the distance between antenna units; The method according to claim 1, including the method described in claim 1.

13. The method according to claim 3, wherein using the direction of the signal data in determining the at least one distance index includes acquiring antenna phase pattern calibration data and interpolating the antenna phase response.

14. The method according to claim 7, comprising determining the rotation angle between the first antenna unit and the second antenna unit based on the rotation variable.

15. A system comprising processing means and storage means, wherein the storage means stores program instructions, and when the program instructions are executed by the processing means, the system is configured to cause the system to perform the method according to any one of claims 1 to 14.

16. A computer program comprising a program instruction, which, when executed by the system's processing means, causes the system to perform the method described in any one of claims 1 to 14.

17. A configuration for evaluating the distance between at least a first antenna unit and a second antenna unit, wherein the configuration comprises at least a first antenna unit associated with a first wireless unit, a second antenna unit associated with a second wireless unit, and a processor, and the configuration is - Transmitting a first signal having first circular polarization through the first antenna unit; - The second antenna unit receives the first signal; - To determine first phase information indicating the phase of the received first signal with respect to the local oscillator of the wireless unit associated with the second antenna unit; - Transmitting a first response signal that essentially matches the first signal through the second antenna unit; - The first antenna unit receives the first response signal; - To determine first response phase information indicating the phase of the received first response signal with respect to the local oscillator of the wireless unit associated with the first antenna unit; - To determine a first phase sum that represents the sum of the first phase information and the first response phase information; - Transmitting a second signal having a second circular polarization opposite to the first circular polarization through the first antenna unit or one of the two antenna units; - Receiving the second signal with the other of the first antenna unit or the second antenna unit; - The antenna unit that receives the second signal determines second phase information indicating the phase of the received second signal with respect to the local oscillator of the associated wireless unit; - Transmitting a second response signal that is essentially consistent with the second signal through the first antenna unit or the other of the second antenna unit that is not transmitting the second signal; - The antenna unit that transmitted the second signal receives the second response signal; - The antenna unit that receives the second response signal determines second response phase information indicating the phase of the received second response signal with respect to the local oscillator of the associated wireless unit; - To determine a second phase sum that represents the sum of the second phase information and the second response phase information; - Determining at least one distance index indicating the distance between the first antenna unit and the second antenna unit based on at least the first phase sum and the second phase sum; A configuration that is set up to perform a certain action.

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