Angle of arrival, angle of departure direction finding apparatus and carrier frequency offset estimation method

Abstract

The application discloses an angle of arrival, angle of departure direction finding device and a carrier frequency offset estimation method for the angle of arrival direction finding device and the angle of departure direction finding device. The carrier frequency offset estimation method for the angle of arrival direction finding device comprises the following steps: determining an antenna switching mode, wherein the antenna switching mode comprises at least one continuous repeating antenna mode; switching the antenna according to the antenna switching mode, receiving a signal containing direction finding information sent by a target device, and obtaining corresponding sampling points; for each piece of sampling data of each continuous repeating antenna mode, calculating a carrier frequency offset estimation value corresponding to a sampling time of each sampling point starting from a second sampling point; and based on the carrier frequency offset estimation values corresponding to the sampling times of the obtained carrier frequency offset estimation values, obtaining carrier frequency offset estimation values corresponding to other sampling times of which the carrier frequency offset estimation values are not obtained through interpolation. The carrier frequency offset estimation method disclosed by the application can be applied to a larger frequency offset range and can track carrier frequency drift, thereby improving direction finding precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular, to an angle of arrival and angle of departure direction finding device and a carrier frequency offset estimation method thereof. BACKGROUND

[0002] Radio direction finding technology is widely used in various wireless devices.

[0003] Bluetooth protocol starts from version 5.1, and the low power Bluetooth (BLE) standard adds a direction finding function, supporting two direction finding methods, namely angle of arrival (AoA) method and angle of departure (AoD) method. Figure 1A The principle diagram of the angle of arrival direction finding method is shown, in which the transmitting device uses a single antenna to transmit signals, the receiving device uses an antenna array composed of two or more antennas, and each antenna is used to receive signals in turn according to a certain antenna switching mode. The phase difference of the signals arriving at different antennas of the receiving device is used to calculate the angle of the transmitting device relative to the antenna array of the receiving device, that is, AoA. Figure 1B The principle diagram of the angle of departure direction finding method is shown, in which the transmitting device uses an antenna array composed of two or more antennas, and each antenna is used to transmit signals in turn according to a preset antenna switching mode. The receiving device uses a single antenna to receive signals. The phase difference of the signals arriving at the receiving device from different antennas of the transmitting device is used to calculate the angle of the receiving device relative to the antenna array of the transmitting device, that is, AoD.

[0004] However, due to the mismatch of the oscillators of the receiving device and the transmitting device, and the frequency drift of the transmitting device or the receiving device, etc., the carrier frequency offset is inevitably present in the received signal. The carrier frequency offset mainly includes the fixed carrier offset between the receiving device and the transmitting device and the frequency drift. The carrier frequency offset will be reflected in the phase of the sampling data in the AoA / AoD estimation, and then affect the accuracy of the angle estimation.

[0005] To solve the above problems, document CN115051741A proposes a method for eliminating the influence of BLE direction finding carrier frequency offset to obtain phase delay. The method configures the antenna switching mode as a specific switching mode, thereby obtaining the phase difference between antennas and angle without estimating the carrier frequency offset. However, due to the specific antenna switching mode used by the method, the range of frequency offset that can be eliminated by the method is small. For a time slot length of 1us, the maximum frequency offset that can be eliminated by the method is 125kHz; for a time slot length of 2us, the maximum frequency offset that can be eliminated is 62.5kHz. Considering the noise in practice, the range of frequency offset that can be eliminated will be smaller. Since the Bluetooth protocol allows the center frequency of the BLE device to deviate by no more than ±150kHz, it can be seen that the method of the patent cannot cover the entire frequency offset range allowed by the BLE device. In addition, the specific antenna switching mode used in the patent will make the number of sampling points of one antenna much larger than that of other antennas, which cannot uniformly use each antenna, resulting in low angle estimation accuracy of the patent. SUMMARY

[0006] One purpose of the present application is to provide a carrier frequency offset estimation method, an angle of arrival direction finding device and an angle of departure direction finding device to solve the influence of carrier frequency offset and frequency drift existing in the received signal of the angle of arrival or angle of departure direction finding device and improve the angle estimation accuracy.

[0007] One aspect of the present application provides a carrier frequency offset estimation method for an angle of arrival direction finding device, the angle of arrival direction finding device comprising at least two antennas, the method comprising: determining an antenna switching mode, the antenna switching mode comprising at least one continuous repeating antenna mode; switching antennas according to the antenna switching mode, receiving a signal containing direction finding information sent by a target device to obtain corresponding sampling points; for each piece of sampling data of each continuous repeating antenna mode, calculating a carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from the second sampling point; and based on the frequency offset estimation value corresponding to the sampling time of the obtained frequency offset estimation value, obtaining the carrier frequency offset estimation value corresponding to other sampling times by interpolation.

[0008] In some embodiments, after obtaining the carrier frequency offset estimation value corresponding to other sampling times by interpolation, the method further comprises filtering the carrier frequency offset estimation value corresponding to each sampling time, and using the filtered result as a new carrier frequency offset estimation value.

[0009] In some embodiments, the receiving time window of the angle of arrival direction finding device comprises a reference period, and alternately distributed switching time slots and sampling time slots after the reference period; and switching the antennas according to the antenna switching mode, receiving the signal containing direction finding information sent by the target device, and obtaining the corresponding sampling points, comprises: in the reference period, using the first antenna in the antenna switching mode to receive the signal containing direction finding information sent by the target device; according to the antenna arrangement order of the antenna switching mode, sequentially switching the antennas to the next antenna in the antenna switching mode in each switching time slot; and in each sampling time slot, using the antenna switched in the last switching time slot to receive the signal containing direction finding information sent by the target device.

[0010] In this embodiment, according to the antenna arrangement order of the antenna switching mode, sequentially switching the antennas to the next antenna in the antenna switching mode in each switching time slot comprises: in each switching time slot, if the antenna before switching and the antenna after switching are the same antenna, then receiving the signal containing direction finding information sent by the target device in the switching time slot.

[0011] In this embodiment, the time length of the sampling time slot is the same as that of the switching time slot.

[0012] In some embodiments, for each piece of sampling data of each continuous repeated antenna mode, calculating the carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from the second sampling point comprises: for each sampling point starting from the second sampling point, calculating the phase difference between the sampling point and the previous sampling point, and then subtracting the carrier time delay phase difference to obtain the carrier frequency offset phase difference corresponding to the sampling time of the sampling point; and based on the carrier frequency offset phase difference and the sampling period, calculating the carrier frequency offset estimation value corresponding to the sampling time of the sampling point.

[0013] In some embodiments, the signal containing direction finding information is sent by the target device using a single antenna.

[0014] In some embodiments, the angle of arrival direction finding device is a Bluetooth low power consumption device, and the signal containing direction finding information is a constant tone spread signal.

[0015] In a second aspect of the present application, a carrier frequency offset estimation method for an angle of departure device is provided, comprising: determining an antenna switching mode of a target device, judging whether the antenna switching mode comprises at least one continuous repeated antenna mode; in response to the antenna switching mode comprising at least one continuous repeated antenna mode, receiving a signal containing direction finding information sent by the target device to obtain corresponding sampling points; for each piece of sampling data corresponding to each continuous repeated antenna mode of the target device, calculating a carrier frequency offset estimation value corresponding to a sampling time of each sampling point starting from a second sampling point; and based on the carrier frequency offset estimation values corresponding to the sampling times for which the carrier frequency offset estimation values have been obtained, obtaining carrier frequency offset estimation values corresponding to other sampling times for which the carrier frequency offset estimation values have not been obtained through interpolation.

[0016] In some embodiments, after obtaining the carrier frequency offset estimation values corresponding to the other sampling times for which the carrier frequency offset estimation values have not been obtained through interpolation, the method further comprises: filtering the carrier frequency offset estimation values corresponding to the respective sampling times, and taking the filtered results as new carrier frequency offset estimation values.

[0017] In some embodiments, the transmission time window of the target device comprises sampling slots and switching slots alternately distributed; and the receiving of the signal containing direction finding information sent by the target device to obtain corresponding sampling points comprises: receiving the signal containing direction finding information sent by the target device in each sampling slot.

[0018] In some embodiments, the calculation of the carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from the second sampling point for each piece of sampling data corresponding to each continuous repeated antenna mode of the target device comprises: for each sampling point starting from the second sampling point, calculating a phase difference between the sampling point and a previous sampling point, and then subtracting a carrier time delay phase difference to obtain a carrier frequency offset phase difference corresponding to the sampling time of the sampling point; and based on the carrier frequency offset phase difference and a sampling period, calculating the carrier frequency offset estimation value corresponding to the sampling time of the sampling point.

[0019] In some embodiments, the receiving of the signal containing direction finding information sent by the target device comprises: receiving the signal containing direction finding information sent by the target device using a single antenna.

[0020] In some embodiments, the angle of departure device is a Bluetooth low energy device, and the signal containing direction finding information is a constant tone spread signal.

[0021] In a third aspect of the present application, a device for angle of arrival direction finding is provided, which comprises a receiver and a processor, the receiver comprises at least two antennas, and the processor is configured to: determine an antenna switching mode, the antenna switching mode comprising at least one continuous repeated antenna mode; control the receiver to switch antennas according to the antenna switching mode, receive a signal containing direction finding information sent by a target device, and obtain corresponding sampling points; for each piece of sampling data corresponding to each continuous repeated antenna mode, calculate a carrier frequency offset estimation value corresponding to a sampling time of each sampling point starting from the second sampling point; and based on the frequency offset estimation values corresponding to the sampling times for which the frequency offset estimation values have been obtained, obtain carrier frequency offset estimation values corresponding to other sampling times for which the frequency offset estimation values have not been obtained through interpolation.

[0022] In a third aspect of the present application, a device for angle of departure direction finding is provided, which comprises a receiver and a processor, and the processor is configured to: determine an antenna switching mode of a target device, judge whether the antenna switching mode comprises at least one continuous repeated antenna mode; in response to the antenna switching mode comprising at least one continuous repeated antenna mode, control the receiver to receive a signal containing direction finding information sent by the target device, and obtain corresponding sampling points; for each piece of sampling data corresponding to each continuous repeated antenna mode of the target device, calculate a carrier frequency offset estimation value corresponding to a sampling time of each sampling point starting from the second sampling point; and based on the frequency offset estimation values corresponding to the sampling times for which the frequency offset estimation values have been obtained, obtain carrier frequency offset estimation values corresponding to other sampling times for which the frequency offset estimation values have not been obtained through interpolation.

[0023] The above is a summary of the present application, which may have simplified, generalized and omitted details, so those skilled in the art should recognize that this part is only illustrative and is not intended to limit the scope of the present application in any way. This summary part is neither intended to determine the key features or essential features of the claimed subject matter, nor intended to serve as an auxiliary means to determine the scope of the claimed subject matter. BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and other features of the present application will become more fully understood from the following detailed description and the accompanying drawings, in which:

[0025] Figure 1A A schematic diagram of the principle of the angle of arrival direction finding method is shown;

[0026] Figure 1B A schematic diagram of the principle of the angle of departure direction finding method is shown;

[0027] Figure 2A CTE structure of the transmitting end and the receiving end of the AoA method is shown;

[0028] Figure 2B CTE structure of the transmitting end and the receiving end of the AoD method is shown;

[0029] Figure 3 A schematic diagram of a carrier frequency offset estimation method 200 for an angle of arrival direction finding device according to an embodiment of the present disclosure is shown;

[0030] Figure 4 A schematic diagram of sampling points obtained by an embodiment of an AoA receiver when the antenna switching pattern is {A0, A1, A1, A2} is shown;

[0031] Figure 5 A schematic diagram of sampling points obtained by another embodiment of an AoA receiver when the antenna switching pattern is {A0, A1, A1, A2} is shown;

[0032] Figure 6 A schematic diagram of a carrier frequency offset estimation method 400 for an angle of departure direction finding device according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0033] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments can be utilized, and other changes can be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

[0034] For the convenience of those skilled in the art, the principles of the angle of arrival (AoA) and angle of departure (AoD) direction finding methods are briefly described below with reference to the principle schematic diagrams shown in FIGS. Figure 1A and Figure 1B It should be noted that although the present disclosure is described with respect to the CTE structure of the BLE protocol, the methods of the present disclosure are not limited to being applied to BLE devices.

[0035] In order to support direction finding, a constant tone extension (CTE) is added to the data packet of the BLE protocol, and the CTE is located after the data packet payload. The transmitting end transmits a CTE signal during the CTE. The CTE signal is a single tone signal of a fixed frequency.

[0036] Figure 2A The CTE structure of the transmitter and receiver in the AoA method is shown. During the CTE period, the transmitter continuously transmits CTE signals using a single antenna. The receiver's CTE period is divided into a guard period, a reference period, and time-alternating switching and sampling time slots. Depending on the antenna switching mode, the receiver uses one antenna for data sampling during the reference period and sampling time slot, but antenna switching can only be performed during the switching time slot.

[0037] Figure 2B The CTE structure of the transmitter and receiver in the AoD method is shown. The CTE period of the transmitter is divided into a guard period, a reference period, and time-alternating switching and sampling time slots. The transmitter uses one antenna to transmit the CTE signal during the reference period and sampling time slot, depending on the antenna switching mode, but antenna switching can only occur during the switching time slot. The receiver uses a single antenna to sample data during the corresponding reference period and sampling time slot.

[0038] Antenna switching modes in AoA or AoD methods can be represented by antenna sequences. For example, an antenna switching mode P of length N can be represented as a sequence of N antennas, i.e., P = {p0, p1, ..., p...} N-1}, where p n This represents the (n+1)th antenna in the antenna switching mode, where n = 0, 1, ..., N-1. The same antenna can appear multiple times in the antenna switching mode. For the AoA method, during the reference time period, the receiver uses the first antenna p0 of the antenna switching mode to receive the signal, the second antenna p1 of the antenna switching mode is used in the first sampling time slot to receive the signal, and so on. After the Nth antenna in the antenna switching mode is used, the first antenna is used cyclically in the next sampling time slot to receive the signal, and so on. The AoD method is similar: during the reference time period, the transmitter uses the first antenna p0 of the antenna switching mode to transmit the signal, the second antenna p1 of the antenna switching mode is used in the first sampling time slot to transmit the signal, and so on. After the Nth antenna in the antenna switching mode is used, the first antenna is used cyclically in the next sampling time slot to transmit the signal, and so on.

[0039] By utilizing the phase difference of the signals received between different antennas and the spacing between the antennas, AoA or AoD can be estimated. If we denote the angle of arrival (AoA) or departure angle (AoD) as θ, the spacing between two adjacent antennas at the receiver (AoA method) or transmitter (AoD method) as d, and the phase difference between the signals received by two adjacent antennas at the AoA receiver or transmitted by two adjacent antennas at the AoD transmitter as... Based on the assumption that the incident signal is a plane wave, we can obtain Where λ is the signal wavelength. Therefore, the angle of arrival or departure angle where arccos(·) denotes the inverse cosine function.

[0040] From the above analysis, it can be seen that if there is a carrier frequency offset in the received signal, it will inevitably lead to errors in the calculation of the above phase difference at the receiving end, thereby causing deviations in the AoA / AoD estimation. In addition, due to the frequency drift phenomenon of the oscillators at the receiving end and the transmitting end, the carrier frequency offset will change over time. Therefore, it is necessary to estimate and track the changes in the carrier frequency offset in real time in order to obtain more accurate angle estimation.

[0041] Embodiments of the present disclosure propose a carrier frequency offset estimation method 200 for an angle of arrival direction finding device, and a carrier frequency offset estimation method 400 for an angle of departure direction finding device. The method 200 and the method 400 can be applied in an AoA direction finding device and an AoD direction finding device respectively to obtain a carrier frequency offset estimation result. After obtaining the carrier frequency offset estimation result, the received signal can be compensated for frequency offset, thereby eliminating the influence of the carrier frequency offset in the received signal and obtaining more accurate direction finding results. On the other hand, the method 200 and the method 400 have less restrictions on the antenna switching mode, and can flexibly set the antenna switching mode as needed.

[0042] Figure 3 A schematic diagram of the carrier frequency offset estimation method 200 for an angle of arrival direction finding device of embodiments of the present disclosure is shown. The method 200 includes the following steps:

[0043] In step 210, the antenna switching mode is determined.

[0044] As described above, the angle of arrival (AoA) direction finding device should include at least two antennas. The AoA direction finding device can configure the antenna switching mode P as needed, but the antenna switching mode should include at least one continuous repeating antenna mode. The continuous repeating antenna mode means that the same antenna appears continuously in the antenna switching mode P. If the antenna switching mode P is represented as P={p0,p1,…,p N-1 N-1}, where N is the length of the antenna switching mode, then the antenna switching mode P including at least one continuous repeating antenna mode can be represented as: there is at least one n (0≤n n N-1}, where N is the length of the antenna switching mode, then the antenna switching mode P including at least one continuous repeating antenna mode can be represented as: there is at least one n (0≤n (n+1)mod N Here, "mod" denotes the modulo operation, and for a mod b (where a and b are both integers), the result is the remainder of a divided by b.

[0045] Since each antenna in the antenna switching pattern is used in turn, the use of antennas continues to cycle from the first antenna, for the case that the last antenna in the antenna switching pattern is the same as the first antenna, it also belongs to the continuous repeating antenna pattern, for this case, the antenna switching pattern P can be circularly shifted, the last antenna of the original antenna switching pattern P is taken as the first antenna of the new antenna switching pattern P', that is, P' = {p N-1 , p0, p1, …, p N-2}. If the last antenna of P' is still the same as the first antenna thereof, the circular shift can be continued until it is different. After the above transformation, an antenna switching pattern in which the first antenna is different from the last antenna can be obtained. Therefore, the case that the first antenna is the same as the last antenna also belongs to the antenna switching pattern including the continuous repeating antenna pattern. In the following, the antenna switching pattern in which the first antenna is different from the last antenna is taken as an example for description, unless otherwise specified. The person skilled in the art can apply the method described in the embodiment of the present disclosure to the antenna switching pattern in which the first antenna is the same as the last antenna.

[0046] The longest antenna sequence in which the antennas in the antenna switching pattern P remain unchanged is referred to as an antenna pattern, and the antenna pattern includes the continuous repeating antenna pattern and the single antenna pattern. The length of the antenna sequence of the antenna pattern is referred to as the antenna repetition number of the antenna pattern. The antenna repetition number of the continuous repeating antenna pattern is greater than 1, and the antenna repetition number of the single antenna pattern is equal to 1. For the convenience of description, the antenna repetition number of the (m+1)th antenna pattern is denoted as N m , and the number of antenna patterns is denoted as N c . Taking four antennas A0, A1, A2 and A3 as an example, if the antenna switching pattern is {A0, A1, A1, A1, A0, A0, A2, A3}, the number of antenna patterns N c = 5, the first antenna pattern is "A0", which is a single antenna pattern, and the antenna repetition number N0= 1; the second antenna pattern is "A1, A1, A1", which is a continuous repeating antenna pattern, and the antenna repetition number N1= 3; the third antenna pattern is "A0, A0", which is a continuous repeating antenna pattern, and the antenna repetition number N2= 2; the fourth and fifth antenna patterns are "A2" and "A3" respectively, which are both single antenna patterns, and the corresponding antenna repetition numbers N3= N4= 1.

[0047] In step 220, the antennas are switched according to the antenna switching pattern, and the signal containing the direction finding information sent by the target device is received to obtain the corresponding sample points.

[0048] Here, the target device is the device whose angle of arrival (AoA) is to be measured. The angle of arrival refers to the angle between the target device and the antenna array of the AoA direction-finding device. When the target device transmits a signal containing direction-finding information using a single antenna, the AoA direction-finding device equipped with two or more antennas can receive the signal from the target device by switching antennas and measure the angle of arrival of the target device.

[0049] The signal containing direction-finding information can be a single-frequency signal, such as a CTE signal. In some embodiments, the signal containing direction-finding information can also be a narrowband modulated signal. In this case, the receiver can preprocess the received signal to remove the influence of the narrowband modulated signal. Without preprocessing, the frequency of the narrowband modulated signal is equivalent to the frequency offset superimposed on the carrier. Therefore, the bandwidth of the narrowband modulated signal should be lower than the maximum allowable error of the carrier frequency offset estimation; otherwise, it will significantly affect the accuracy of the carrier frequency offset estimation. The maximum allowable error of the carrier frequency offset estimation depends on the required estimation accuracy, which can be determined by those skilled in the art in specific implementations.

[0050] Within its time window for receiving signals containing direction-finding information from the target device, the AoA device sequentially uses one antenna in each sampling time slot, according to the antenna arrangement order of antenna switching mode P, to receive the signals containing direction-finding information transmitted by the target device. The AoA device's reception time window can be... Figure 2A The structure during CTE is shown. During the reference period, the first antenna p0 of antenna switching mode P is used to receive the signal. In the subsequent first switching time slot, the antenna is switched to p1. In the subsequent first sampling time slot, the signal is received using antenna p1. In the second switching time slot, the antenna is switched to p2, and so on, until the last antenna p0 of antenna switching mode P is used. N-1 After use, the first antenna p0 is used cyclically, and so on, until the reception time window ends or a sufficient number of sampling points are obtained. The lengths of the sampling time slot and the switching time slot can be the same or different. The following explanation mainly uses the case where the sampling time slot and the switching time slot are set to the same length as an example, so the lengths of the sampling time slot and the switching time slot are uniformly represented as T. slot The implementation method is similar when the sampling time slot and the switching time slot lengths are different.

[0051] For ease of explanation, the sampling points obtained by the AoA receiver from sampling the received signal are represented as follows: Where m is the antenna mode number in antenna switching mode P, 0≤m <N c n is the sampling point number corresponding to this antenna mode, 0≤n <N m, u represents the number of times of using the antenna switching pattern P to sample data. The sampling point is the IQ data represented by complex number obtained by the receiver sampling the received signal, the real part is the in-phase component, and the imaginary part is the quadrature component.

[0052] Figure 4 The sampling point obtained by the AoA receiver is shown when the antenna switching pattern is {A0, A1, A1, A2}. Figure 4 In the figure, the AoA receiver samples in the reference period and the sampling time slots, and samples once in each sampling time slot, and does not sample in the switching time slot. From the beginning of the reference period to the third sampling time slot, the antenna switching pattern is used for the first time, so u = 0, wherein antenna A0 is used in the reference period, and the last sampling point obtained is The first and second sampling time slots correspond to the continuous repeated antenna pattern "A1, A1", and antenna A1 is used to obtain the sampling points and The sampling interval between the two sampling points is 2T slot , antenna A2 is used in the third sampling time slot to obtain the sampling point From the fourth sampling time slot to the seventh sampling time slot, the antenna switching pattern is used for the second time, so u = 1, and the sampling points obtained in each sampling time slot are and The rest of the sampling points are the same, and will not be described again.

[0053] It should be noted that when the antenna is switched according to the antenna switching pattern P, in each switching time slot, if the antenna before switching and the antenna after switching are the same antenna, no physical antenna switching operation needs to be performed. The antenna before switching and the antenna after switching are the same antenna, which corresponds to the case of the continuous repeated antenna pattern in the antenna switching pattern P. The continuous repeated antenna pattern can be fully utilized to receive the signal corresponding to the switching time slot between the continuously repeated antennas to obtain more sampling points. Therefore, in some embodiments, in each switching time slot, if the antenna before switching and the antenna after switching are the same antenna, the signal containing the direction finding information sent by the target device is received in the switching time slot. Figure 5 The sampling point obtained by the AoA receiver is shown when the antenna switching pattern is {A0, A1, A1, A2}, and when the antennas used in the sampling time slots before and after the switching time slot are the same antenna. The sampling point obtained by the AoA receiver is shown when the antenna switching pattern is {A0, A1, A1, A2}, and when the antennas used in the sampling time slots before and after the switching time slot are the same antenna. Figure 4 and Figure 5 It can be seen that in the case where the antenna before switching and the antenna after switching are the same antenna, if sampling is also performed in the switching time slot, one sampling point can be increased, and the sampling interval between adjacent sampling points is correspondingly reduced. For example, in Figure 5In the first time of using the antenna switching mode, the first sampling time slot, the second switching time slot and the second sampling time slot are all sampled by using the antenna A1, and the obtained sampling points are respectively denoted as and The sampling interval between two adjacent sampling points is T slot It can be understood that Figure 4 and Figure 5 The same symbol is used in the above two formulas and But the corresponding sampling positions in the two cases are not the same, and the sampling intervals are also different.

[0054] In step 230, for each piece of sampling data of each continuous repeated antenna mode, the carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from the second sampling point is calculated.

[0055] The sampling data corresponding to the continuous repeated antennas in the antenna switching mode at least includes two sampling points. Since these sampling points are all sampling points of the same antenna, the phase difference between these sampling points can be used to estimate the carrier frequency offset. Specifically, for each piece of sampling data of each continuous repeated antenna mode, the phase difference between each sampling point starting from the second point of the piece of data and the previous sampling point is calculated, and then the carrier delay phase difference is subtracted to obtain the carrier frequency offset phase difference corresponding to the sampling time of the sampling point. Then, based on the carrier frequency offset phase difference and the sampling period, the carrier frequency offset estimation value corresponding to the sampling time of the sampling point is calculated.

[0056] If the carrier frequency of the received signal is denoted as f0, and the carrier frequency offset is denoted as Δf, then the phase difference between the next sampling point and the previous sampling point received by the same antenna can be expressed as

[0057] Δφ=Principal[2π(f0+Δf)T] (1)

[0058] Where T is the sampling interval between the two sampling points, Principal(x) represents the principal value of the real angle x, and the unit is radian, which is equal to x+2πk, where k is an integer such that -π<Principal(x)≤π. According to the phase difference Δφ between the adjacent sampling points of the same antenna, the carrier frequency offset

[0059]

[0060] From the expression of the above phase difference Δφ, it can be seen that since the carrier frequency f0 and the sampling interval T are constants, when -π<2πΔfT≤π, each Δφ corresponds to Δf one by one, therefore, the frequency offset range that can be estimated by the method 200 of the present disclosure is That is, the maximum frequency offset that can be estimated is For the case that the sampling interval T is 1us and 2us respectively, the maximum frequency offset that can be estimated by the method 200 is 500KHz and 250KHz respectively, which is 4 times of the maximum frequency offset that can be eliminated by the method disclosed in the document CN115051741A.

[0061] In this step, for each piece of sampling data corresponding to each continuous repeated antenna mode, the phase difference between each sampling point and the previous sampling point from the second point of the piece of data is calculated, and then the carrier delay phase difference is subtracted to obtain the carrier frequency offset phase deviation corresponding to the sampling time of the sampling point, which can be exemplarily expressed as follows:

[0062]

[0063] wherein, is the carrier frequency offset phase deviation corresponding to the sampling time of the sampling point c , n is the sampling point sequence number of the continuous repeated antenna mode, Q m is the sampling point number of the piece of sampling data, and Q m ≥2. Angle(x) represents the angle of complex number x, whose unit is radian, Angle(x)=arctan[Imag(x) / Real(x)], wherein Real(x) and Image(x) represent the real part and the imaginary part of x respectively, and arctan(·) represents the inverse tangent function. represents the carrier frequency offset phase deviation corresponding to the sampling time of the sampling point , which is mainly caused by the carrier frequency offset.

[0064] After obtaining the carrier frequency offset phase deviation, the carrier frequency offset estimation value corresponding to the sampling time of the sampling point is calculated based on the carrier frequency offset phase deviation and the sampling period, which can be exemplarily expressed as follows:

[0065]

[0066] wherein, is the carrier frequency offset estimation value corresponding to the sampling time of the sampling point when the antenna switching mode is used for the (u+1)th time.

[0067] In order to facilitate the understanding of those skilled in the art, the following will be described by taking Figure 4 and Figure 5 as examples.

[0068] For Figure 4In the example shown, the second antenna mode in the antenna switching mode is the continuous repeating antenna mode "A1,A1", where the repeating antenna is A1. When the antenna switching mode is used for the first time, continuous sampling using antenna A1 yields a sample data segment including two sampling points. and The sampled data length Q1 = 2, and the sampling interval T = 2T slot The sampling points are obtained according to formula (3). The carrier frequency offset phase deviation corresponding to the sampling time And the carrier frequency offset estimate is obtained according to formula (4). Similarly, when using the antenna switching mode for the second time, the sampling points can be obtained. The carrier frequency offset phase deviation corresponding to the sampling time and carrier frequency offset estimate The situation is similar when using the antenna switching mode later.

[0069] for Figure 5 In the example shown, during the first use of the antenna switching mode, continuous sampling using antenna A1 yields a data segment comprising three sampling points, namely... and The sampled data length Q1 = 3, and the sampling interval T = T slot The sampling points are obtained according to formula (3). The carrier frequency offset phase deviation corresponding to the sampling time The corresponding carrier frequency offset estimate is obtained according to formula (4). and sampling points The carrier frequency offset phase deviation corresponding to the sampling time Corresponding carrier frequency offset estimate Similarly, when using the antenna switching mode for the second and subsequent times, we can obtain the carrier frequency offset estimate corresponding to the sampling time of each sampling point starting from the second sampling point of the continuously repeating antenna.

[0070] In step 240, based on the frequency offset estimate corresponding to the sampling time for which the frequency offset estimate has been obtained, the carrier frequency offset estimate corresponding to other sampling times for which the frequency offset estimate has not been obtained is obtained by interpolation.

[0071] Available interpolation methods include linear interpolation and polynomial interpolation. The following explanation uses linear interpolation as an example; the principles are similar for other interpolation methods. If linear interpolation is used, for other sampling times where a frequency offset estimate is not obtained, the frequency offset estimate for that sampling time can be obtained by interpolating using the frequency offset estimates corresponding to the two adjacent sampling times. For example, for...Figure 4 in the frequency offset estimation value corresponding to the sampling time may be obtained by and interpolation, for Figure 4 in and the frequency offset estimation corresponding to the sampling time, may be obtained by and interpolation. Figure 4 and Figure 5 In and, the solid circles show the sampling time corresponding to the carrier frequency offset estimation value obtained by continuously repeating the sampling data of the antenna, and the hollow circles show the sampling time corresponding to the carrier frequency offset estimation value obtained by interpolation.

[0072] Through the above steps of the method 200, the carrier frequency offset estimation value corresponding to each sampling time can be obtained. It should be noted that since a carrier frequency offset estimation value can be obtained for each sampling time, it can be understood that the carrier frequency offset estimation value obtained by the method 200 is time-varying, so as to track the carrier frequency drift. The sampling point at the sampling time is compensated for frequency offset using the carrier frequency offset estimation value, and the sampling point after the frequency offset is eliminated is obtained, and the AoA estimation is performed using the sampling point after the frequency offset is eliminated, so as to improve the direction finding accuracy.

[0073] In some embodiments, after step 240, the method 200 further includes step 250.

[0074] In step 250, the carrier frequency offset estimation value corresponding to each sampling time is filtered, and the filtered result is used as a new carrier frequency offset estimation value.

[0075] The purpose of filtering is to obtain a smooth carrier frequency offset estimation value, so as to reduce the variance of the carrier frequency offset estimation value and improve the accuracy of the carrier frequency offset estimation. The specific filtering method can be selected as needed, for example, a filtering method using a finite impulse response (FIR) filter, an infinite impulse response (IIR) filter, and a Kalman filter, and the present disclosure does not limit the specific filtering method. The sampling point is compensated for frequency offset using the filtered carrier frequency offset estimation value, which can further improve the accuracy of direction finding.

[0076] Figure 6A schematic diagram of a carrier frequency offset estimation method 400 of an AoD direction finding device is shown, the method 400 can be applied in an AoD direction finding device. The method 400 and the carrier frequency offset estimation method 200 of an AoA direction finding device have a corresponding relationship, the switching of the target device transmitting antenna in the method 400 can correspond to the switching of the AoA direction finding device receiving antenna in the method 200, therefore, the method 400 and the method 200 have similar features, and in the following, for the same concept, no longer will be described separately. Specifically, the method 400 includes the following steps:

[0077] In step 410, the antenna switching mode of the target device is determined.

[0078] Here, the target device is a device whose departure angle is to be measured, and the departure angle refers to the angle between the AoD direction finding device and the antenna array of the target device. The target device has two or more antennas, which switch the transmitting antenna according to the antenna switching mode when transmitting a signal containing direction finding information. The AoD direction finding device uses a single antenna to receive the signal containing direction finding information transmitted by the target device, and estimates the departure angle of the target device based on the received signal.

[0079] The antenna switching mode of the target device can be configured by the target device itself, and then signaled to the AoD direction finding device, or determined by the target device and the AoD direction finding device through negotiation.

[0080] In step 420, it is determined whether the antenna switching mode includes at least one continuous repeating antenna mode.

[0081] The method 400 is applicable to the case where there is a continuous repeating antenna mode in the antenna switching mode, so the AoD direction finding device first needs to determine whether there is a continuous repeating antenna mode in the antenna switching mode, if not, the carrier frequency offset cannot be estimated using this method. If there is a continuous repeating antenna mode, the subsequent steps can be continued.

[0082] In step 430, in response to the antenna switching mode including at least one continuous repeating antenna mode, the signal containing direction finding information transmitted by the target device is received to obtain the corresponding sampling points.

[0083] In this step, after the AoD direction finding device confirms that the antenna switching mode includes at least one continuous repeating antenna mode, the signal containing direction finding information transmitted by the target device is received.

[0084] The target device transmits the signal containing direction finding information in the continuous repeating antenna mode. Figure 2BThe AoD transmitting end generates continuous signals containing direction finding information in the time window, and transmits the signals according to the antenna switching mode. In the reference period, the first antenna of the antenna switching mode is used to transmit signals, in the first sampling time slot, the second antenna is used to transmit signals, and so on. After the use of all antennas in the current switching mode is completed, the first antenna is used in a cycle. The AoD direction finding device obtains a plurality of sampling points in sequence according to Figure 2B The receiving time window of the AoD receiving end uses a single antenna to receive signals in the reference period and each sampling time slot. Because the sampling mode of the AoD direction finding device is the same as that of the AoA direction finding device, the sampling time and the value of the sampling point of the AoD direction finding device can also be exemplarily represented by Figure 4 The sampling time and the sampling point. For example, for the antenna switching mode of the target device being {A0, A1, A1, A2}, the AoD direction finding device obtains the sampling point Figure 4 and and

[0085] In step 440, for each piece of sampling data corresponding to each continuous repeated antenna mode of the target device, the carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from the second sampling point is calculated.

[0086] This step has the same principle as step 230 of method 200. For each piece of sampling data corresponding to each continuous repeated antenna mode, starting from the second sampling point of the data, the carrier frequency offset estimation value corresponding to the sampling time of the sampling point can be obtained in sequence by using formulas (3) and (4).

[0087] Similarly, the carrier frequency offset estimation value corresponding to the sampling time of the sampling point when the antenna switching mode is used for the (u+1)th time is represented as m is the antenna mode number of the continuous repeated antenna mode, 0≤m<N c ; n is the sampling point number corresponding to the continuous repeated antenna mode, 0≤n<Q m .

[0088] In step 450, based on the frequency offset estimation value corresponding to the sampling time of the obtained frequency offset estimation value, the carrier frequency offset estimation value corresponding to the sampling time of the other sampling points which have not obtained the frequency offset estimation value is obtained by interpolation.

[0089] This step has the same principle as step 240 of method 200. For specific details, please refer to step 240, which will not be described here again. After interpolation, the carrier frequency offset estimation value corresponding to the sampling time of each sampling point of the AoD direction finding device can be obtained.

[0090] It can be seen that, through the above steps of the method 400, the carrier frequency offset estimation value corresponding to each sampling time can be obtained, and the carrier frequency drift can be tracked. The sampling points at the sampling time are compensated for frequency offset using the carrier frequency offset estimation value, the sampling points after the frequency offset are eliminated, and the AoD estimation is performed using the sampling points after the frequency offset, so that the direction finding accuracy can be improved.

[0091] In some embodiments, after step 450, the method 400 further includes step 460.

[0092] This step is similar to step 260 of method 200. By filtering the carrier frequency offset estimation value corresponding to each sampling time, the filtered result is obtained as a new carrier frequency offset estimation value, which can further improve the accuracy of direction finding.

[0093] The present disclosure also provides an angle of arrival direction finding device, which includes a receiver and a processor, and can be used to implement the carrier frequency offset estimation method 200 for the angle of arrival direction finding device of the embodiments of the present disclosure. The receiver of the angle of arrival direction finding device includes at least two antennas, and the processor is configured to perform the following steps 610 to 640.

[0094] In step 610, a determination is made of an antenna switching mode, the antenna switching mode including at least one continuously repeated antenna mode.

[0095] In step 620, the receiver is controlled to switch antennas according to the antenna switching mode, and a signal containing direction finding information sent by a target device is received to obtain corresponding sampling points.

[0096] In step 630, for each piece of sampling data of each continuously repeated antenna mode, a carrier frequency offset estimation value corresponding to a sampling time of each sampling point starting from the second sampling point is calculated.

[0097] In step 640, based on the frequency offset estimation values corresponding to the sampling times for which the frequency offset estimation values have been obtained, interpolation is performed to obtain carrier frequency offset estimation values corresponding to other sampling times for which the frequency offset estimation values have not been obtained.

[0098] The present disclosure also provides an angle of departure direction finding device, which includes a receiver and a processor, and can be used to implement the carrier frequency offset estimation method 400 for the angle of departure direction finding device of the embodiments of the present disclosure. The processor of the angle of departure direction finding device is configured to perform the following steps 810 to 840.

[0099] In step 810, a determination is made of an antenna switching mode of a target device, and a determination is made of whether the antenna switching mode includes at least one continuously repeated antenna mode.

[0100] In step 820, in response to the antenna switching pattern comprising at least one continuous repeated antenna pattern, the receiver is controlled to receive the signal containing direction finding information sent by the target device to obtain corresponding sample points.

[0101] In step 830, for each piece of sample data corresponding to each continuous repeated antenna pattern of the target device, the carrier frequency offset estimation value corresponding to the sampling time of each sample point starting from the second sample point is calculated.

[0102] In step 840, based on the frequency offset estimation value corresponding to the sampling time of the obtained frequency offset estimation value, the carrier frequency offset estimation value corresponding to the sampling time of other sample points which do not have the frequency offset estimation value is obtained by interpolation.

[0103] Those skilled in the art can understand and implement other changes to the disclosed embodiments by reading the specification, disclosure and drawings and the appended claims, and such changes fall within the protection scope of the claims of the present disclosure. In the claims, the word "comprising" does not exclude other elements and steps, and the word "a" or "one" does not exclude a plurality. In the practical application of the present application, one part can perform the functions of multiple technical features referred to in the claims. Any reference signs in the claims should not be understood as limiting the scope.

Claims

1. A carrier frequency offset estimation method for a direction of arrival device, the direction of arrival device comprising at least two antennas, characterized in that, The method comprises: determining an antenna switching pattern, the antenna switching pattern comprising at least one continuous repeating antenna pattern, the antenna switching pattern can be represented as an antenna sequence of length N , representing one of the at least two antennas, wherein a continuous repeating antenna pattern refers to the same antenna appearing consecutively in the antenna sequence P or a cyclic shift of P ​ switching antennas according to the antenna switching mode, receiving signals containing direction finding information sent by the target device, and obtaining corresponding sampling points; for each piece of sampling data corresponding to each continuous repeated antenna mode, calculating a carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from the second sampling point; and based on the carrier frequency offset estimation value corresponding to the sampling time of the obtained carrier frequency offset estimation value, obtaining a carrier frequency offset estimation value corresponding to the sampling time of other sampling points which do not have the carrier frequency offset estimation value through interpolation.

2. The method of claim 1, wherein, After obtaining the carrier frequency offset estimation value corresponding to the sampling time of other sampling points which do not have the carrier frequency offset estimation value through interpolation, the method further comprises: filtering the carrier frequency offset estimation value corresponding to each sampling time, and taking the filtered result as a new carrier frequency offset estimation value.

3. The method of claim 1, wherein, The receiving time window of the angle of arrival direction finding device comprises a reference period, and alternately distributed switching time slots and sampling time slots after the reference period; switching antennas according to the antenna switching mode, receiving signals containing direction finding information sent by the target device, and obtaining corresponding sampling points, comprising: in the reference period, using the first antenna in the antenna switching mode to receive the signals containing direction finding information sent by the target device; in each switching time slot, switching the antenna to the next antenna in the antenna switching mode according to the antenna arrangement order of the antenna switching mode; and in each sampling time slot, using the antenna switched in the last switching time slot to receive the signals containing direction finding information sent by the target device.

4. The method of claim 3, wherein, in each switching time slot, switching the antenna to the next antenna in the antenna switching mode according to the antenna arrangement order of the antenna switching mode, comprising: in each switching time slot, if the antenna before switching and the antenna after switching are the same antenna, receiving the signals containing direction finding information sent by the target device in the switching time slot.

5. The method of claim 3, wherein, The time length of the sampling time slot and the switching time slot is the same.

6. The method of claim 1, wherein, for each piece of sampling data corresponding to each continuous repeated antenna mode, calculating a carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from the second sampling point, comprising: for each sampling point starting from the second sampling point, calculating the phase difference between the sampling point and the previous sampling point, and then subtracting the carrier time delay phase difference to obtain the carrier frequency offset phase difference corresponding to the sampling time of the sampling point; based on the carrier frequency offset phase difference and the sampling period, calculating the carrier frequency offset estimation value corresponding to the sampling time of the sampling point.

7. The method of claim 1, wherein, The signals containing direction finding information are sent by the target device using a single antenna.

8. The method of claim 1, wherein, The angle of arrival direction finding device is a Bluetooth low energy device, and the signals containing direction finding information are constant tone spread signals.

9. A carrier frequency offset estimation method for an angle of departure direction finding device, characterized by, The method comprises: determining an antenna switching pattern of a target device, judging whether the antenna switching pattern comprises at least one continuous repeating antenna pattern, the target device comprising two or more antennas, the antenna switching pattern can be represented as an antenna sequence of length N , representing one of the two or more antennas, wherein the continuous repeating antenna pattern refers to the same antenna continuously appearing in the antenna sequence P or a cyclic shift of P . in response to the antenna switching mode comprising at least one continuous repeated antenna mode, receiving signals containing direction finding information sent by the target device, and obtaining corresponding sampling points; for each piece of sampling data corresponding to each continuous repeated antenna mode of the target device, calculating a carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from the second sampling point; and Based on the frequency offset estimation value corresponding to the sampling time at which the frequency offset estimation value has been obtained, a carrier frequency offset estimation value corresponding to other sampling times at which the frequency offset estimation value has not been obtained is obtained through interpolation.

10. The method of claim 9, wherein, After the carrier frequency offset estimation value corresponding to other sampling times at which the frequency offset estimation value has not been obtained is obtained through interpolation, the method further comprises: Filtering the carrier frequency offset estimation value corresponding to each sampling time, and taking the filtered result as a new carrier frequency offset estimation value.

11. The method of claim 9, wherein, The transmission time window of the target device comprises sampling slots and switching slots which are alternately distributed; receiving the signal containing direction finding information transmitted by the target device to obtain corresponding sampling points comprises: Receiving the signal containing direction finding information transmitted by the target device in each sampling slot.

12. The method of claim 9, wherein, For each piece of sampling data corresponding to each continuously repeated antenna mode of the target device, calculating a carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from a second sampling point comprises: For each sampling point starting from the second sampling point, calculating a phase difference between the sampling point and a previous sampling point, and then subtracting a carrier time delay phase difference to obtain a carrier frequency offset phase difference corresponding to the sampling time of the sampling point; Based on the carrier frequency offset phase difference and a sampling period, calculating a carrier frequency offset estimation value corresponding to the sampling time of the sampling point.

13. The method of claim 9, wherein, Receiving the signal containing direction finding information transmitted by the target device comprises: Receiving the signal containing direction finding information transmitted by the target device using a single antenna.

14. The method of claim 9, wherein, The angle of departure direction finding device is a Bluetooth Low Energy device, and the signal containing direction finding information is a constant tone spread signal.

15. An angle of arrival direction finding device, characterized by The angle of arrival direction finding device comprises a receiver and a processor, the receiver comprises at least two antennas, and the processor is configured to: determining an antenna switching pattern, the antenna switching pattern comprising at least one consecutive repeating antenna pattern, the antenna switching pattern can be represented as an antenna sequence of length N , representing one of the at least two antennas, wherein a consecutive repeating antenna pattern refers to the same antenna appearing consecutively in the antenna sequence P or a cyclic shift of P ​ Control the receiver to switch antennas according to the antenna switching mode, receive the signal containing direction finding information transmitted by the target device, and obtain corresponding sampling points; For each piece of sampling data of each continuously repeated antenna mode, calculate a carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from a second sampling point; and Based on the frequency offset estimation value corresponding to the sampling time at which the frequency offset estimation value has been obtained, a carrier frequency offset estimation value corresponding to other sampling times at which the frequency offset estimation value has not been obtained is obtained through interpolation.

16. An angle of departure direction finding device characterized by The angle of departure direction finding device comprises a receiver and a processor, and the processor is configured to: determining an antenna switching pattern of a target device, judging whether the antenna switching pattern comprises at least one continuous repeating antenna pattern, the target device comprising two or more antennas, the antenna switching pattern can be represented as an antenna sequence of length N , denotes one of the two or more antennas, wherein a continuous repeating antenna pattern means that the same antenna continuously appears in the antenna sequence P or a cyclic shift of P ​ In response to the antenna switching mode comprising at least one continuously repeated antenna mode, control the receiver to receive the signal containing direction finding information transmitted by the target device to obtain corresponding sampling points; For each piece of sampling data corresponding to each continuously repeated antenna mode of the target device, calculate a carrier frequency offset estimation value corresponding to the sampling time of each sampling point starting from a second sampling point; and Based on the frequency offset estimation value corresponding to the sampling time at which the frequency offset estimation value has been obtained, a carrier frequency offset estimation value corresponding to other sampling times at which the frequency offset estimation value has not been obtained is obtained through interpolation.

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