Dual-frequency direction finding system and method fusing ultra-wideband and bluetooth

Abstract

The application discloses a dual-frequency direction-finding system and method combining ultra-wideband and Bluetooth, which comprises a tag and a base station, and the tag and the base station are communicatively connected, further comprises a dual-frequency array antenna, the dual-frequency array antenna is installed on the base station, and the dual-frequency array antenna is compatible with a 2.4G Bluetooth frequency band and a 4G ultra-wideband frequency band. The dual-frequency array antenna is a binary array antenna, comprising an antenna array element one and an antenna array element two, and the distance between the antenna array element one and the antenna array element two is d. The dual-frequency direction-finding system combining ultra-wideband and Bluetooth can enlarge the array element spacing, improve the isolation between array elements, suppress array element coupling, has robustness to phase noise, can improve the direction-finding performance, and can be widely applied to the field of wireless positioning.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, and in particular relates to a dual-frequency direction finding system and method that integrates ultra-wideband and Bluetooth. Background Technology

[0002] Ultra-wideband (UWB) technology first appeared in the US military field. In April 2002, the US Federal Communications Commission (FCC) lifted civilian licensing restrictions on UWB technology, leading to its rapid popularization and development. Simultaneously, the FCC allocated a bandwidth of 7.5 GHz (3.1-10.6 GHz) for UWB. my country's UWB development started relatively late, but it has received high attention from the Party and the State. In early September 2001, my country's "15th Five-Year Plan" National 863 Program's communication technology theme research project included "Ultra-wideband wireless communication technology and its coexistence and compatibility technology" as a research content for common and innovative wireless communication technologies, demonstrating the country's emphasis on UWB development.

[0003] UWB technology transmits data using extremely narrow pulses instead of traditional carrier waves, resulting in extremely high data transmission speeds. In addition, UWB technology has advantages such as low system complexity, high information security, and strong resistance to multipath fading, making it a major highlight in the field of wireless positioning.

[0004] Chinese patent document CN110366105A discloses an ultra-wideband (UWB) positioning method and apparatus. In response to detecting first Bluetooth broadcast data, it resets positioning parameters that are inconsistent with those indicated by the first Bluetooth broadcast data. The first Bluetooth broadcast data includes at least one of the data transmission channel, data transmission rate, and data transmission frequency configured by the positioning base station to be communicated with. Based on the currently set positioning parameters and the UWB positioning mode, it sends a positioning signal to the positioning base station, enabling the positioning base station and positioning server to determine their current location according to the configured UWB positioning mode. However, in this technical solution, Bluetooth technology is used for transmitting tag configuration parameters and automatically resetting the positioning tag parameters; it does not participate in the measurement of positioning parameters, which rely solely on UWB technology. The problem it aims to solve is how to broadcast data via Bluetooth and how to listen to Bluetooth broadcast data.

[0005] Chinese patent document CN114430440A discloses a control method, tag, device, terminal, and storage medium for a smart device. The method, applied to a mobile terminal, includes: the mobile terminal sensing radio pulse signals emitted by an electronic tag in real time, the electronic tag being positioned within a preset range of the smart device; determining the orientation information between the mobile terminal and the electronic tag based on the radio pulse signals; and sending corresponding control commands to the smart device based on the orientation information to control the smart device. This application improves the convenience of controlling smart devices through the above method. In this technical solution, angle measurement is only performed using ultra-wideband technology, while Bluetooth signals are used for device connection and control signal transmission and do not participate in angle measurement.

[0006] Chinese patent document CN114495569A discloses a vehicle location and locating system, method, and vehicle based on ultra-wideband (UWB) technology. The system includes a vehicle-mounted terminal, a mobile terminal, a Bluetooth key, and an UWB positioning base station component. The mobile terminal sends a location and locating request to the vehicle-mounted terminal and receives vehicle location information from the terminal. The vehicle-mounted terminal activates the UWB positioning base station component upon receiving the request and receives distance information from it. The Bluetooth key contains an UWB positioning tag. The UWB positioning base station component includes four UWB base stations located around the vehicle. These base stations communicate with the UWB positioning tag, sending ranging requests and measuring the distance between them upon receiving the returned information. This technical solution adds UWB positioning functionality to a traditional Bluetooth car key, representing two independent functions. Bluetooth technology establishes communication between the key and the vehicle, used for control signal transmission. UWB, on the other hand, uses a multi-base station positioning method based on UWB ranging to track the car key's location; Bluetooth does not participate in the measurement of positioning parameters.

[0007] Chinese patent document CN115190425A discloses a three-dimensional indoor positioning method and system integrating Bluetooth AOA and ultra-wideband (UWB) positioning. It includes Bluetooth base station S1, Bluetooth base station S2, and UWB base station S3 established on the same plane. Bluetooth base station S1 and UWB base station S3 are set at the same point, while Bluetooth base station S1 and Bluetooth base station S2 are spaced apart by a distance P1. The positioning tag is located within the positioning space formed by Bluetooth base station S1, Bluetooth base station S2, and UWB base station S3. This invention integrates UWB positioning and Bluetooth angle-of-arrival (BLE-AOA) positioning; it provides a model for correcting ranging errors using the UWB least squares method and proposes an algorithm for processing outliers in IQ data acquired by the Bluetooth antenna array. Finally, adaptive filtering is used to optimize the angle measurement values ​​obtained from the IQ data. This allows for three-dimensional spatial positioning using only three base stations, overcoming the limitation of traditional three-dimensional positioning systems requiring at least four base stations. The method in this technical solution is to use Bluetooth technology to estimate the azimuth and elevation angles, use ultra-wideband technology to measure the distance, and then use the azimuth, elevation, and distance values ​​to perform positioning calculations to achieve three-dimensional positioning of three base stations. The fusion of Bluetooth and ultra-wideband is performed after the positioning parameters are measured and calculated, rather than during the positioning parameter measurement stage.

[0008] In existing, commonly used pure UWB direction finding methods, the small element spacing introduces mutual coupling between elements, leading to a decrease in angle estimation accuracy. Currently, in UWB direction finding systems, the high frequency of UWB signals results in very small antenna spacing and significant coupling between elements, thus introducing substantial angle measurement errors. While increasing the antenna spacing can improve ranging accuracy and reduce element coupling according to angle measurement principles, this introduces a new problem: the phase difference may increase with the antenna spacing, thereby increasing integer ambiguity. Therefore, eliminating integer ambiguity and improving direction finding accuracy becomes crucial for UWB direction finding. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a dual-frequency direction finding system that integrates ultra-wideband and Bluetooth. By integrating Bluetooth technology with a dual-frequency array antenna, the spacing between array elements can be increased, the isolation between array elements can be improved, the coupling between array elements can be suppressed, and the system is robust to phase noise, thereby improving the direction finding performance. It can be widely used in the field of wireless positioning.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: the dual-frequency direction finding system integrating ultra-wideband and Bluetooth includes a tag and a base station, the tag and the base station forming a communication connection, the dual-frequency direction finding system integrating ultra-wideband and Bluetooth also includes a dual-frequency array antenna, the dual-frequency array antenna is installed on the base station, and the dual-frequency array antenna is compatible with the 2.4G Bluetooth band and the 4G ultra-wideband band.

[0011] By employing the above technical solution, the fusion of Bluetooth technology with a dual-frequency array antenna can increase the spacing between array elements, improve the isolation between elements, suppress element coupling, and exhibit robustness against phase noise, thereby enhancing direction-finding performance and making it widely applicable in the field of wireless positioning. Based on UWB PDOA estimation, Bluetooth 5.1 direction-finding technology is innovatively integrated, utilizing dual-frequency constraints to remove ambiguity and improve direction-finding accuracy. This technical solution fuses the two technologies during the positioning parameter (angle value) measurement stage; the two technologies must complement each other. However, given an array element spacing, neither UWB nor Bluetooth technology alone can achieve accurate angle measurement.

[0012] Preferably, the tag integrates Bluetooth module one and ultra-wideband module one, and the base station integrates Bluetooth module two and ultra-wideband module two. Both Bluetooth module one and Bluetooth module two are Bluetooth chips integrating the Bluetooth 5.1 protocol, which transmit constant tone extension (CTE) signals. When the receiving end receives the constant tone extension (CTE) signals, it can directly obtain the IQ value with phase information. Ultra-wideband module one integrates a single DW1000 chip, and ultra-wideband module two integrates two DW1000 chips. The chips (DW1000 chips) integrated in ultra-wideband module one and ultra-wideband module two can obtain the phase difference (PDOA) information of the dual-frequency array antenna arriving at the base station.

[0013] Preferably, the dual-frequency array antenna is a two-element array antenna, including antenna element one and antenna element two, with a distance d between them. The accuracy of measuring the phase difference between antenna elements one and two is closely related to the distance d between them. In traditional single-frequency antenna arrays, the element spacing needs to be less than half the wavelength. For high-frequency signals like ultra-wideband signals, the signal wavelength is relatively short, the element spacing is very small, and the coupling between elements is relatively large, introducing a large angle measurement error. Simultaneously, according to the angle measurement principle, increasing the antenna spacing can improve ranging accuracy and reduce coupling between elements; however, this may also increase integer ambiguity due to the increased antenna spacing. Therefore, the value of the distance d between antenna elements one and two is crucial to eliminating integer ambiguity.

[0014] Preferably, the method for calculating the distance d between antenna element one and antenna element two is as follows:

[0015] If the center frequency of the Bluetooth signal is set to f1 and the center frequency of the ultra-wideband signal is set to f2, then according to the phase difference formula, we can obtain:

[0016]

[0017]

[0018] Where N1 and N2 represent the number of phase ambiguity periods, λ1 and λ2 represent the measured phase difference, respectively, and represent the wavelengths of different frequencies f1 and f2.

[0019] Combining equations (1) and (2), we can simplify to obtain:

[0020]

[0021] Further simplifying equation (3), we get:

[0022]

[0023] make Then we get:

[0024] N1=N2*λ2 / λ1+w (5);

[0025] As can be seen from equation (5), given w, if N2 is determined, then N1 is uniquely determined;

[0026] Let the phase difference measurement value If the standard deviation of is δ, then the standard deviation of w is:

[0027]

[0028] Let Q = N² * λ² / λ¹, then Q is represented by an integer part plus a fractional part; assuming the smallest fractional interval with no integer ambiguity is S (S > 0), the fractional part of Q is represented by M, w by W, and the noise of w by F, then we have:

[0029] M+W+F=N0+F (7);

[0030] Where N0 = M + W;

[0031] To avoid integer ambiguity, let the interval of the decimal part in Q be S, then:

[0032] M+S+W+F=N0+F+S (8);

[0033] M-S+W+F=N0+FS (9);

[0034] In other words, under conditions free from noise interference, F and S need to satisfy the following conditions:

[0035] abs(F+S)>abs(F) (10);

[0036] abs(FS)>abs(F) (11);

[0037] abs(F+S+1)>abs(F) (12);

[0038] abs(F+S-1)>abs(F) (13);

[0039] abs(F) < 1 / 2 (14);

[0040] 0 < S < 1 (15);

[0041] By combining equations (10) to (15), we can obtain:

[0042] 2*3*δ w <S<1-2*3*δ w (16);

[0043] Assuming the standard deviation of the phase difference measurement noise is 10 degrees, which translates to 10 / 180 = 0.056 radians, then according to equation (6), δ can be obtained. w Equal to 0.0104, from equation (16), the minimum interval S of the decimal part of Q needs to satisfy:

[0044] 0.0624 < S < 0.9376 (17);

[0045] According to Q=N2*λ2 / λ1, under the frequency combination of f1=2.4GHz and f2=4GHz, when the interval S of the fractional part of Q satisfies equation (17), the range of N2 is [1,5]; that is, the range of the distance d between antenna array element one and antenna array element two is [1*λ2,5*λ2].

[0046] Preferably, when the value range of N2 is [1,5], the value range of the decimal places of Q is [0.6097,0.0485].

[0047] Preferably, when f2 = 4 GHz, λ2 is 7.5 cm, so the distance d between the first antenna element and the second antenna element ranges from 7.5 to 37.5 cm.

[0048] Preferably, the method for direction finding using this dual-frequency direction finding system integrating ultra-wideband and Bluetooth specifically includes the following steps:

[0049] S1: The tag sends an ultra-wideband poll frame, the base station receives the poll frame and obtains the phase difference PDOA value of the dual-frequency array antenna of the poll frame arriving at the base station.

[0050] S2: The base station sends an ultra-wideband response frame carrying the phase difference PDOA information of the dual-frequency array antenna that arrived at the base station via the poll frame. The tag receives the ultra-wideband response frame, completes ultra-wideband ranging, and obtains ultra-wideband ranging information as well as the phase difference PDOA information of the dual-frequency array antenna that arrived at the base station via the tag poll frame.

[0051] S3: The tag sends a Bluetooth final frame carrying ultra-wideband ranging information and phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station. The base station receives the Bluetooth final frame and obtains the phase information IQ value of the base station's Bluetooth module, the phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station, and the ultra-wideband ranging information.

[0052] S4: The azimuth angle is obtained by fusing the phase information IQ value of the base station's Bluetooth module and the phase difference PDOA information of the ultra-wideband poll frames arriving at the base station.

[0053] By adopting the above technical solution, the direction finding method of the dual-frequency direction finding system that integrates ultra-wideband and Bluetooth utilizes dual-frequency constraints to remove ambiguity, thereby increasing the antenna spacing, increasing the direction finding resolution, and improving the direction finding accuracy of ultra-wideband PDOA.

[0054] Preferably, in step S4, the Bluetooth phase difference (PDOA) information of antenna array element 1 and antenna array element 2 is first obtained using the Bluetooth phase information IQ value of antenna array element 1 and the Bluetooth phase information IQ value of antenna array element 2. Specifically, let the Bluetooth phase information IQ value obtained by antenna array element 1 be I1 and Q1, and the Bluetooth phase information IQ value obtained by antenna array element 2 be I2 and Q2, then:

[0055] α1=arctan(Q1,I1) (18);

[0056] α2=arctan(Q2,I2) (19);

[0057] α12=α1-α2 (20);

[0058] Wherein, α1 is the Bluetooth phase information of antenna element one, α2 is the phase information of antenna element two, and α12 is the phase difference PDOA information between antenna element one and antenna element two.

[0059] Preferably, the specific steps for obtaining the azimuth angle in step S4 are as follows: Let the phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station be β12, and the azimuth angle be θ, then:

[0060]

[0061]

[0062] in, and Let α12 and β12 be the actual Bluetooth phase difference and UWB phase difference values, respectively, and let N1 and N2 be the measured Bluetooth phase difference and UWB phase difference PDOA values. Let λ1 and λ2 represent the number of ambiguity cycles of the Bluetooth and UWB phase differences, respectively, and let λ1 and λ2 represent the wavelengths of the Bluetooth center frequency f1 and the UWB center frequency f2, respectively. Combining equations (21) and (22) and simplifying, we get:

[0063]

[0064] When the distance d between antenna array element 1 and antenna array element 2 meets the range of values, N1 and N2 are in a one-to-one correspondence. The value of N2 can be obtained according to the value of the distance d between antenna array element 1 and antenna array element 2. Then, N1 can be obtained by equation (5). Substituting N1 into equation (23) will give the azimuth angle θ.

[0065] Compared with the prior art, the beneficial effects of the present invention are as follows: For ultra-wideband PDOA direction finding, increasing the antenna spacing can increase the direction finding resolution, but at the same time it will cause direction finding ambiguity. In order to remove ambiguity, the present invention innovatively integrates Bluetooth 5.1 direction finding technology and uses dual-frequency constraints to remove ambiguity, thereby improving the direction finding accuracy. Attached Figure Description

[0066] Figure 1 This is a schematic diagram of the dual-frequency direction finding system integrating ultra-wideband and Bluetooth according to the present invention;

[0067] Figure 2 This is a schematic diagram of the dual-frequency array antenna in the dual-frequency direction finding system integrating ultra-wideband and Bluetooth of the present invention.

[0068] Figure 3 The flowchart shows the dual-frequency direction finding method of the present invention using a dual-frequency direction finding system integrating ultra-wideband and Bluetooth;

[0069] Figure 4 This is a schematic diagram illustrating the relationship between Bluetooth IQ value and phase information in the dual-frequency direction finding method of the dual-frequency direction finding system using a fusion of ultra-wideband and Bluetooth according to the present invention.

[0070] Figure 5 This is a schematic diagram of the azimuth angle obtained by the dual-frequency direction finding method of the present invention using a dual-frequency direction finding system that integrates ultra-wideband and Bluetooth. Detailed Implementation

[0071] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0072] This embodiment of the dual-frequency direction finding system integrating ultra-wideband and Bluetooth, such as Figure 1As shown, the system includes tag 1 and base station 2, which form a communication connection. This dual-frequency direction finding system integrating ultra-wideband and Bluetooth also includes a dual-frequency array antenna 3, which is mounted on base station 2 and is compatible with both the 2.4 GHz Bluetooth band and the 4 GHz ultra-wideband band. Tag 1 integrates Bluetooth module 102 and ultra-wideband module 101, while base station 2 integrates Bluetooth module 202 and ultra-wideband module 201. Both Bluetooth module 102 and Bluetooth module 202 are Bluetooth chips integrating the Bluetooth 5.1 protocol, transmitting a constant frequency spread signal (CST). When the receiver receives a fixed-frequency spread signal (CTE), it can directly obtain the IQ value with phase information; the ultra-wideband module 101 integrates a single DW1000 chip; the ultra-wideband module 201 integrates two DW1000 chips. The chips (DW1000 chips) integrated in ultra-wideband module 101 and ultra-wideband module 201 can obtain the phase difference PDOA information of the dual-frequency array antenna reaching the base station; the dual-frequency array antenna 3 is a two-element array antenna, such as... Figure 2 As shown, the array includes antenna element 301 and antenna element 302, with a distance d between them. The correct measurement of the phase difference between antenna elements 301 and 302 is closely related to the distance d between them. In traditional single-frequency antenna arrays, the element spacing needs to be less than half the wavelength. For high-frequency signals like ultra-wideband, the signal wavelength is relatively short, the element spacing is small, and the coupling between elements is large, leading to significant angle measurement errors. According to the angle measurement principle, increasing the antenna spacing can improve ranging accuracy and reduce coupling between elements; however, this may also increase integer ambiguity due to the increased antenna spacing. Therefore, the value of the distance d between antenna elements 301 and 302 is crucial to eliminating integer ambiguity. The calculation method for the distance d between antenna elements 301 and 302 is as follows:

[0073] If the center frequency of the Bluetooth signal is set to f1 and the center frequency of the ultra-wideband signal is set to f2, then according to the phase difference formula, we can obtain:

[0074]

[0075]

[0076] Where N1 and N2 represent the number of phase ambiguity periods, λ1 and λ2 represent the measured phase difference, respectively, and represent the wavelengths of different frequencies f1 and f2.

[0077] Combining equations (1) and (2), we can simplify to obtain:

[0078]

[0079] Further simplifying equation (3), we get:

[0080]

[0081] make Then we get:

[0082] N1=N2*λ2 / λ1+w (5);

[0083] As can be seen from equation (5), given w, if N2 is determined, then N1 is uniquely determined;

[0084] Let the phase difference measurement value If the standard deviation of is δ, then the standard deviation of w is:

[0085]

[0086] Let Q = N² * λ² / λ¹, then Q is represented by an integer part plus a fractional part; assuming the smallest fractional interval with no integer ambiguity is S (S > 0), the fractional part of Q is represented by M, w by W, and the noise of w by F, then we have:

[0087] M+W+F=N0+F (7);

[0088] Where N0 = M + W;

[0089] To avoid integer ambiguity, let the interval of the decimal part in Q be S, then:

[0090] M+S+W+F=N0+F+S (8);

[0091] M-S+W+F=N0+FS (9);

[0092] In other words, under conditions free from noise interference, F and S need to satisfy the following conditions:

[0093] abs(F+S)>abs(F) (10);

[0094] abs(FS)>abs(F) (11);

[0095] abs(F+S+1)>abs(F) (12);

[0096] abs(F+S-1)>abs(F) (13);

[0097] abs(F) < 1 / 2 (14);

[0098] 0 < S < 1 (15);

[0099] By combining equations (10) to (15), we can obtain:

[0100] 2*3*δ w <S<1-2*3*δ w (16);

[0101] Assuming the standard deviation of the phase difference measurement noise is 10 degrees, which translates to 10 / 180 = 0.056 radians, then according to equation (6), δ can be obtained. w Equal to 0.0104, from equation (16), the minimum interval S of the decimal part of Q needs to satisfy:

[0102] 0.0624 < S < 0.9376 (17);

[0103] According to Q = N2 * λ2 / λ1, under the frequency combination of f1 = 2.4 GHz and f2 = 4 GHz, when the interval S of the fractional part of Q satisfies equation (17), the value range of N2 is [1, 5]; that is, the value range of the distance d between antenna element one and antenna element two is [1 * λ2, 5 * λ2]; when the value range of N2 is [1, 5], the value range of the fractional part of Q is [0.6097, 0.0485]. Specifically, as N2 increases, the fractional part of Q is as shown in Table 1 below; when f2 = 4 GHz, λ2 is 7.5 cm, so the value range of the distance d between antenna element one and antenna element two is 7.5 ~ 37.5 cm.

[0104] Table 1. Values ​​of the decimal places of Q as N2 increases.

[0105] N2 0 1 2 3 4 5 Q's decimal places 0 0.6097 0.2194 0.8291 0.4388 0.0485

[0106] The method of direction finding using the dual-frequency direction finding system integrating ultra-wideband and Bluetooth in this embodiment, such as Figure 3 As shown, the specific steps include:

[0107] S1: The tag sends an ultra-wideband poll frame, the base station receives the poll frame and obtains the phase difference PDOA value of the dual-frequency array antenna of the poll frame arriving at the base station.

[0108] S2: The base station sends an ultra-wideband response frame carrying the phase difference PDOA information of the dual-frequency array antenna that arrived at the base station via the poll frame. The tag receives the ultra-wideband response frame, completes ultra-wideband ranging, and obtains ultra-wideband ranging information as well as the phase difference PDOA information of the dual-frequency array antenna that arrived at the base station via the tag poll frame.

[0109] S3: The tag sends a Bluetooth final frame carrying ultra-wideband ranging information and phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station. The base station receives the Bluetooth final frame and obtains the phase information IQ value of the base station's Bluetooth module, the phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station, and the ultra-wideband ranging information.

[0110] S4: The azimuth angle is obtained by fusing the phase information IQ value of the base station's Bluetooth module and the phase difference PDOA information of the ultra-wideband poll frames arriving at the base station.

[0111] In step S4, the Bluetooth phase information IQ values ​​of antenna element 1 and antenna element 2 are first used to obtain the Bluetooth phase difference PDOA information. Specifically, let the Bluetooth phase information IQ values ​​obtained by antenna element 1 be I1 and Q1, and the Bluetooth phase information IQ values ​​obtained by antenna element 2 be I2 and Q2, as follows: Figure 4 As shown, according to Figure 4 The relationship between the IQ value and the phase is as follows:

[0112] α1=arctan(Q1,I1) (18);

[0113] α2=arctan(Q2,I2) (19);

[0114] α12=α1-α2 (20);

[0115] Wherein, α1 is the Bluetooth phase information of antenna element one, α2 is the Bluetooth phase information of antenna element two, and α12 is the Bluetooth phase difference (PDOA) information between antenna element one and antenna element two.

[0116] The specific steps for obtaining the azimuth angle in step S4 are as follows: Let the phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station be β12, and the azimuth angle be θ, then:

[0117]

[0118]

[0119] in, and Let α12 and β12 be the actual Bluetooth phase difference and UWB phase difference values, respectively, and let N1 and N2 be the measured Bluetooth phase difference and UWB phase difference PDOA values. Let λ1 and λ2 represent the number of ambiguity cycles of the Bluetooth and UWB phase differences, respectively, and let λ1 and λ2 represent the wavelengths of the Bluetooth center frequency f1 and the UWB center frequency f2, respectively. Combining equations (21) and (22) and simplifying, we get:

[0120]

[0121] When the distance d between antenna array element 1 and antenna array element 2 meets the range of values, N1 and N2 have a one-to-one correspondence. The value of N2 can be obtained according to the range of the distance d between antenna array element 1 and antenna array element 2. Then, N1 can be calculated by equation (5). Substituting N1 into equation (23) will give the azimuth angle θ. Figure 5 As shown.

[0122] For those skilled in the art, the specific embodiments are merely illustrative descriptions of the present invention. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A dual frequency direction finding system fusing ultra-wideband and Bluetooth, comprising a tag and a base station, the tag and the base station forming a communication connection, characterized in that, The dual-band direction finding system integrating ultra-wideband and Bluetooth also includes a dual-band array antenna, which is installed on the base station and is compatible with both the 2.4G Bluetooth band and the 4G ultra-wideband band. The dual-frequency array antenna is a two-element array antenna, including antenna element one and antenna element two, and the distance between antenna element one and antenna element two is d; The method for calculating the distance d between antenna array element one and antenna array element two is as follows: If the center frequency of the Bluetooth signal is set to f1 and the center frequency of the ultra-wideband signal is set to f2, then according to the phase difference formula, we can obtain: wherein N1, N2 represent the number of phase ambiguity periods, respectively, respectively, and λ1, λ2 represent the wavelengths of different frequencies f1 and f2. Combining equations (1) and (2), we can simplify to obtain: Further simplifying equation (3), we get: make Then we get: N1=N2*λ2 / λ1+w (5); As can be seen from equation (5), given w, if N2 is determined, then N1 is uniquely determined; Let the phase difference measurement value If the standard deviation of is δ, then the standard deviation of w is: Let Q = N² * λ² / λ¹, then Q is represented by an integer part plus a fractional part; assuming the smallest fractional interval with no integer ambiguity is S (S > 0), the fractional part of Q is represented by M, w by W, and the noise of w by F, then we have: M+W+F=N0+F (7); Where N0 = M + W; Let S be the interval of the decimal part in Q, then: M+S+W+F=N0+F+S(8); M-S+W+F=N0+FS(9); In other words, under conditions free from noise interference, F and S need to satisfy the following conditions: abs(F+S)>abs(F)(10); abs(FS)>abs(F)(11); abs(F+S+1)>abs(F)(12); abs(F+S-1)>abs(F)(13); abs(F) < 1 / 2(14); 0＜S＜1(15)； By combining equations (10) to (15), we can obtain: 2*3*δ w <S <1-2*3*δ w (16); Assuming that the standard deviation of the phase difference measurement noise is 10 degrees, which is converted to radian value as 10 / 180 = 0.056, then according to equation (6) can be obtained δ w equal to 0.0104, the smallest Q decimal part of the interval S needs to meet: 0.0624＜S＜0.9376(17)； According to Q=N2*λ2 / λ1, under the frequency combination of f1=2.4GHz and f2=4GHz, when the interval S of the fractional part of Q satisfies equation (17), the range of N2 is [1,5]; that is, the range of the distance d between antenna array element one and antenna array element two is [1*λ2,5*λ2].

2. The dual-frequency direction finding system integrating ultra-wideband and Bluetooth according to claim 1, characterized in that, The tag integrates Bluetooth module one and ultra-wideband module one, and the base station integrates Bluetooth module two and ultra-wideband module two. Both Bluetooth module one and Bluetooth module two are Bluetooth chips that transmit fixed-frequency spread signals. When the receiving end receives the fixed-frequency spread signal, it can directly obtain the phase information IQ value. Ultra-wideband module one integrates a chip; ultra-wideband module two integrates a chip. The chips integrated in ultra-wideband module one and ultra-wideband module two can obtain the phase difference PDOA information of the dual-frequency array antenna arriving at the base station.

3. The dual-frequency direction finding system integrating ultra-wideband and Bluetooth according to claim 1, characterized in that, When the value range of N2 is [1,5], the value range of the decimal places of Q is [0.6097,0.0485].

4. The dual-frequency direction finding system integrating ultra-wideband and Bluetooth according to claim 3, characterized in that, When f2 = 4 GHz, λ2 is 7.5 cm, so the distance d between antenna element one and antenna element two ranges from 7.5 to 37.5 cm.

5. The dual-frequency direction finding system integrating ultra-wideband and Bluetooth according to claim 2, characterized in that, The method for direction finding using this dual-frequency direction finding system that integrates ultra-wideband and Bluetooth specifically includes the following steps: S1: The tag sends an ultra-wideband poll frame, the base station receives the poll frame and obtains the phase difference PDOA value of the dual-frequency array antenna of the poll frame arriving at the base station. S2: The base station sends an ultra-wideband response frame carrying the phase difference PDOA information of the dual-frequency array antenna that arrived at the base station via the poll frame. The tag receives the ultra-wideband response frame, completes ultra-wideband ranging, and obtains ultra-wideband ranging information as well as the phase difference PDOA information of the dual-frequency array antenna that arrived at the base station via the tag poll frame. S3: The tag sends a Bluetooth final frame carrying ultra-wideband ranging information and phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station. The base station receives the Bluetooth final frame and obtains the phase information IQ value of the base station's Bluetooth module, the phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station, and the ultra-wideband ranging information. S4: The azimuth angle is obtained by fusing the phase information IQ value of the base station's Bluetooth module and the phase difference PDOA information of the ultra-wideband poll frames arriving at the base station.

6. The dual-frequency direction finding system integrating ultra-wideband and Bluetooth according to claim 5, characterized in that, In step S4, the Bluetooth phase information IQ value of antenna element 1 and the Bluetooth phase information IQ value of antenna element 2 are first used to obtain the Bluetooth phase difference PDOA information of antenna element 1 and antenna element 2. Specifically, let the Bluetooth phase information IQ value obtained by antenna element 1 be I1 and Q1, and the Bluetooth phase information IQ value obtained by antenna element 2 be I2 and Q2, then we have: α1 = arctan(Q1, I1) (18); α2=arctan(Q2,I2)(19); α12＝α1-α2(20)； Wherein, α1 is the Bluetooth phase information of antenna element one, α2 is the Bluetooth phase information of antenna element two, and α12 is the Bluetooth phase difference (PDOA) information between antenna element one and antenna element two.

7. The dual-frequency direction finding system integrating ultra-wideband and Bluetooth according to claim 6, characterized in that, The specific steps for obtaining the azimuth angle in step S4 are as follows: Let the phase difference (PDOA) information of the ultra-wideband poll frame arriving at the base station be β12, and the azimuth angle be θ, then: in, and Let α12 and β12 be the actual Bluetooth phase difference and UWB phase difference values, respectively, and let N1 and N2 be the measured Bluetooth phase difference and UWB phase difference PDOA values. Let N1 and N2 represent the number of ambiguity cycles of the Bluetooth and UWB phase differences, respectively, and let λ1 and λ2 represent the wavelengths of the Bluetooth center frequency f1 and the UWB center frequency f2, respectively. Combining equations (21) and (22) and simplifying, we get: When the distance d between antenna array element 1 and antenna array element 2 meets the range of values, N1 and N2 are in a one-to-one correspondence. The value of N2 can be obtained according to the value of the distance d between antenna array element 1 and antenna array element 2. Then, N1 can be obtained by equation (5). Substituting N1 into equation (23) will give the azimuth angle θ.

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