A TDOA distance difference measurement method based on chirp spread spectrum beat wave

Abstract

The application discloses a TDOA distance difference measurement method based on chirp spread spectrum beat wave, and the correlation between the chirp spread spectrum CSS time domain signals received by two antennas on a multi-antenna base station is utilized to obtain the time difference of arrival of the measurement signals transmitted by a target node to the two antennas on the multi-antenna base station, so that the distance difference is obtained. The multi-antenna receiving base station is used as a receiving device, and the CSS signal is used as a measurement signal, so that the method has the characteristics of strong anti-interference ability, long coverage distance and the like. At the receiving end, two intermediate frequency CSS signals are obtained through beat frequency quadrature demodulation, and the signals are continuously subjected to beat processing, so that the correlation function of the two received signals after the correlation operation still retains the beat phenomenon, and the distance difference measurement precision and the noise resistance are greatly improved. Through the above means, the measurement precision of the distance difference can be improved to the decimeter level even if the signal-to-noise ratio is as low as-7 dB.

Description

TECHNICAL FIELD

[0001] The present application relates to a wireless distance difference measurement method, which is a TDOA distance difference measurement method based on a Chirp Spread Spectrum (CSS) beat wave, and belongs to the technical field of wireless communication. BACKGROUND

[0002] In recent years, with the development of wireless technology and Internet of Things technology, target positioning has a wide demand in the field of wireless sensor networks and Internet of Things. In outdoor conditions, the global navigation satellite system (GNSS) represented by China's Beidou satellite navigation system and the American GPS system can provide accurate positioning. However, in indoor environments, GNSS cannot provide accurate positioning due to the shielding of satellite signals by buildings. Therefore, the research on indoor positioning technology has become an important research direction. At present, indoor positioning schemes based on various communication technologies and positioning methods are in full bloom, each with its own advantages and disadvantages, and so far there has been no scheme that performs well in all aspects. The main reason is that in the distance or distance difference measurement stage, it is difficult to achieve a measurement scheme that is accurate, has strong anti-interference ability, and has a long coverage distance.

[0003] The commonly used positioning schemes in the current indoor positioning technology include positioning schemes using communication modes of RFID, WiFi, Bluetooth, Zigbee, UWB, ultrasonic wave, LoRa, etc. In these positioning schemes, the RSSI method is used for distance estimation by RFID, WiFi, Bluetooth, Zigbee and LoRa. Due to the complex environment in the wireless network, the attenuation caused by the signal penetrating the wall or other interference in the channel will affect the RSSI, resulting in general distance measurement accuracy based on RSSI, and the final positioning accuracy can only be in meters. In addition to the LoRa scheme using spread spectrum modulation and demodulation technology, the communication distance of other schemes is limited, resulting in a relatively limited coverage range of the positioning system. Expanding the coverage range requires more positioning base stations. The positioning scheme based on ultrasonic wave uses a reflective ranging method, and the ranging accuracy can reach centimeters. However, the ultrasonic wave signal is greatly affected by the multipath effect and non-line-of-sight propagation, and the ultrasonic wave frequency is easily affected by the Doppler effect and temperature, so that the application scenarios of the positioning scheme based on ultrasonic wave are very limited. The positioning scheme based on UWB (Ultra Wide Band) technology uses a distance difference measurement method based on TDOA (Time Difference of Arrival). The TDOA method only needs to measure the time difference of the signal arriving at two receiving nodes rather than the time, so it does not require strict time synchronization between the receiving base station and the target node transmitting the measurement signal, simplifying the system and achieving high distance difference accuracy. The UWB positioning scheme based on the TDOA method can achieve sub-millimeter or even centimeter accuracy, but is limited by the short transmission distance of the UWB signal, resulting in high accuracy but limited coverage range of the UWB positioning scheme. Moreover, the UWB module has high power consumption and high cost, and is difficult to play a role in low-power Internet of Things. SUMMARY

[0004] In order to solve the problem that the existing indoor positioning technology cannot simultaneously achieve high-precision distance / distance difference measurement, strong anti-interference capability and wide coverage, the present application proposes a TDOA distance difference measurement method based on chirp spread spectrum beat wave. The target node sends a chirp spread spectrum CSS measurement signal after orthogonal modulation, which propagates through the wireless channel and reaches any two receiving antennas of the receiving base station. The received signals of the two receiving antennas are differentially quadrature demodulated to obtain an intermediate frequency signal, which is then beat processed. Then, the two beat processed signals are cross-correlated. The cross-correlation function still retains the beat phenomenon, and the maximum point of the real part of the cross-correlation function is searched to obtain the time difference between the two signals. After intermediate frequency + beat processing, the anti-noise performance and distance difference measurement accuracy can be significantly improved.

[0005] The correlation function (real part) of the two signals is completely aligned when the correlation function (real part) of the two signals is completely aligned, and the correlation function value of the two signals is different when the correlation function (real part) of the two signals is different by one sampling point, so that the anti-noise performance is improved, but the adjacent carrier peak of the correlation function (real part) is also generated, which affects the further improvement of the ranging accuracy; after the frequency mixing processing, the adjacent carrier peak of the correlation function (real part) is compressed obviously.

[0006] After the above processing, the time difference Δt of the measurement signal transmitted by the target node to the two antennas of the multi-antenna base station is obtained, and the distance difference Δr between the transmitting device and the two antennas is obtained. The hardware system used by the method is composed of a target node for transmitting measurement signals and a receiving base station with multiple antennas. The lengths of the feed lines between the antennas of the receiving base station and the radio frequency chip of the receiving base station are equal, and can be adjusted in length as needed. At the same time, the receiving base station is provided with a processor for data processing and operation. When deployed, the target node for transmitting measurement signals is located in the far field environment of the receiving base station, and the measurement signal can reach through the direct path. The method uses a multi-antenna receiving base station, which greatly reduces the implementation complexity and cost of the TDOA system.

[0007] Technical scheme: To solve the above technical problems, the technical scheme adopted by the present application is:

[0008] In a first aspect, the present application provides a TDOA distance difference measurement method based on chirp spread spectrum frequency mixing wave, comprising:

[0009] The positioning system comprises a target node and a multi-antenna receiving base station, and uses a chirp spread spectrum CSS signal after orthogonal modulation as a measurement signal.

[0010] In response to the target node transmitting the chirp spread spectrum CSS signal after orthogonal modulation, the receiving signals of at least any two receiving antennas in the multi-antenna receiving base station are obtained.

[0011] The difference frequency orthogonal demodulation is performed on the receiving signals to obtain intermediate frequency signals.

[0012] The frequency mixing processing is performed on the intermediate frequency signals to obtain frequency mixing signals.

[0013] The correlation operation is performed on the two frequency mixing signals, so that the correlation function still retains the frequency mixing phenomenon, and the maximum value point of the real part of the correlation function is determined.

[0014] The distance difference between the target node and the two antennas of the multi-antenna base station is obtained based on the time delay.

[0015] In some embodiments, the target node is used to transmit measurement signals, the multi-antenna receiving base station is used to receive measurement signals, and signal processing and distance difference calculation are performed.

[0016] The multi-antenna receiving base station has multiple receiving antennas, each antenna has the same specification, and the length of the feeder line between each antenna and the receiving end RF chip is equal and adjustable.

[0017] The target node transmitting the measurement signal is located in a far-field environment, and the measurement signal reaches each antenna of the multi-antenna receiving base station through a direct path.

[0018] In the positioning system, the target node and any two receiving antennas of the receiving base station form a TDOA measurement system, and there is a distance difference Δr between the to-be-measured transmitting device and the two antennas.

[0019] In some embodiments, the measurement signal is a chirp spread spectrum (CSS) signal after orthogonal modulation, and the complex baseband signal m(t) is:

[0020] The complex baseband signal m(t) = I(t) + jQ(t) = cosθ(t) + jsinθ(t) = e jθ(t) ;

[0021] Where I(t), Q(t), and j represent the in-phase component, the quadrature component, and the imaginary unit, respectively.

[0022]

[0023] mod represents the modulo operation.

[0024] μ is the sweep frequency slope of the spread spectrum modulation.

[0025] f0 is the starting frequency of the sweep.

[0026] BW is the signal bandwidth.

[0027] In some embodiments, in the target node as the transmitting end, the baseband measurement signal is converted into a radio frequency signal s(t) by means of orthogonal modulation:

[0028]

[0029] Where Re{} represents the real part operation; ω cu = 2πf cu , and f cu is the local oscillator frequency of the orthogonal modulation.

[0030] In some embodiments, the radio frequency signal s(t) passes through a wireless channel to reach an antenna i of the multi-antenna receiving base station, i = 1, 2, 3…, and the received signal r i (t) on the antenna i is represented as:

[0031]

[0032] where h i (t) is the unit impulse response of the wireless channel i, N i (t) is the random noise signal of the channel i, represents a convolution operation.

[0033] In some embodiments, the received signal r i (t) is subjected to a difference frequency quadrature demodulation to obtain an intermediate frequency signal y i (t), comprising:

[0034]

[0035] y i (t) = I i (t) + jQ i (t)

[0036] where the quadrature demodulation ω cd ≠ ω cu ; represents passing the signal through a low-pass filter LPF;

[0037] The intermediate frequency signal y i (t) is subjected to a beat frequency processing to obtain a beat frequency signal y iBF (t), comprising:

[0038] y iBF (t) = y i (t) cos ω BF t

[0039] In some embodiments, the two beat frequency signals are subjected to a cross-correlation operation to determine the maximum value point of the real part of the cross-correlation function, which corresponds to a time delay; based on the time delay, the distance difference between the target node and the two antennas on the multi-antenna base station is obtained, comprising:

[0040] In the TDOA system composed of the target node and the antennas i and l of the receiving base station, i ≠ l, when measuring the distance difference Δr il , the two beat frequency signals are subjected to a cross-correlation operation to search for the point when the real part of the cross-correlation function R il (τ) reaches the maximum value and its corresponding time delay τ ilm , the time difference Δt il is obtained, and then the distance difference Δr il is calculated, and the formula is:

[0041]

[0042] corr il (τ) = Re[R il (τ)]

[0043] corril (τ ilm ) = corr ilmax

[0044] Δt il =-τ ilm (continuous domain)

[0045] Δr il =c×Δt il

[0046] Where τ is the time delay, c is the speed of light (3×10⁻⁶). 8 n / s, y iBF Re[R] is the intermediate frequency signal after beat frequency conversion, and T is the signal period; il [τ] represents the cross-correlation function R. il (τ) is the operation of taking the real part, corr il (τ) represents the result after taking the real part, corr ilmax The function corr il The maximum value of (τ), τ ilm The function corr il (τ) reaches its maximum value corr ilmax The value of τ.

[0047] In a second aspect, the present invention provides a distance difference measurement device based on TDOA and a multi-antenna receiving base station, including a processor and a storage medium;

[0048] The storage medium is used to store instructions;

[0049] The processor is configured to operate according to the instructions to perform the steps of the method according to the first aspect.

[0050] Thirdly, the present invention provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in the first aspect.

[0051] Fourthly, the present invention provides a computer device including one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods described in the first aspect.

[0052] Beneficial effects: the TDOA distance difference measurement method and multi-antenna receiving base station device based on chirp spread frequency beat wave provided by the application have the following advantages: the distance difference measurement method uses a multi-antenna receiving base station, each receiving antenna is naturally synchronized, and the difficulty of implementing the TDOA system is reduced. The CSS signal is used as a measurement signal, the target node transmits the CSS signal, the received signals of any two receiving antennas are subjected to difference frequency quadrature demodulation in the base station receiving equipment, the intermediate frequency signals are obtained, the intermediate frequency signals are subjected to beat frequency processing, then the two beat frequency signals are subjected to cross-correlation operation, the cross-correlation function still retains the beat frequency phenomenon, the maximum point of the cross-correlation function (real part) is searched, and thus the time difference between the two signals can be obtained. After the intermediate frequency + beat frequency processing, the anti-noise performance and the distance difference measurement accuracy can be obviously improved.

[0053] The cross-correlation operation is performed on the intermediate frequency signals instead of the baseband signals, so that the cross-correlation function (real part maximum) when the two signals are completely aligned and the cross-correlation function value when the two signals are different by one sampling point have obvious differences, and thus the anti-noise performance can be improved, but the cross-correlation function (real part) also has peaks at adjacent carriers, which affects the further improvement of the ranging accuracy; after the beat frequency processing, the adjacent carrier peaks of the cross-correlation function (real part) are obviously compressed. By comprehensively using the above methods, the distance difference measurement accuracy can be improved to the decimeter level even when the signal-to-noise ratio is as low as -7 dB, and the method has wide application prospects in the indoor / outdoor positioning system of the low-power wide-area network (LPWAN). BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is a distance difference measurement model diagram of an embodiment of the application.

[0055] Figure 2 It is a principle block diagram of a distance difference measurement system of an embodiment of the application.

[0056] Figure 3 It is a quadrature modulation principle diagram of an embodiment of the application.

[0057] Figure 4 It is an intermediate frequency CSS beat wave generation principle diagram of an embodiment of the application.

[0058] Figure 5 It is a comparison diagram of a baseband signal obtained by zero intermediate frequency demodulation and an intermediate frequency signal real part obtained by difference frequency demodulation under ideal noiseless conditions in an embodiment of the application.

[0059] Figure 6 It is a CSS beat signal (real part) waveform diagram and a spectrum diagram thereof under ideal noiseless conditions in an embodiment of the application.

[0060] Figure 7is the simulation result of the cross-correlation calculation in the ideal noise-free case of the embodiment of the present application.

[0061] Figure 8 is the waveform chart of the CSS beat signal (real part) in the case of adding different degrees of noise in the embodiment of the present application.

[0062] Figure 9 is the simulation result of the cross-correlation calculation in the case of adding different degrees of noise in the embodiment of the present application. DETAILED DESCRIPTION

[0063] Embodiments of the present application are described in detail below with reference to the accompanying drawings, in which the same or similar components are denoted by the same or similar reference numerals throughout, and embodiments described below with reference to the accompanying drawings are exemplary and are for the purpose of explaining the present application only, and cannot be construed as limiting the present application.

[0064] In the description of the present application, the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, more than, etc. are understood as not including the number, above, below, within, etc. are understood as including the number. If it is described as first, second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0065] In the description of the present application, the description of the reference terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0066] Embodiment 1

[0067] In a first aspect, a TDOA distance difference measurement method based on a chirp spread spectrum beat wave is provided, comprising:

[0068] The positioning system includes a target node and a multi-antenna receiving base station, and uses a chirp spread spectrum (CSS) signal after orthogonal modulation as a measurement signal.

[0069] In response to the target node transmitting the chirp spread spectrum (CSS) signal after orthogonal modulation, the received signals of at least any two receiving antennas in the multi-antenna receiving base station are obtained.

[0070] The received signals are subjected to beat frequency orthogonal demodulation to obtain intermediate frequency signals.

[0071] performing beat frequency processing on the intermediate frequency signals to obtain beat frequency signals;

[0072] performing cross-correlation operation on the two beat frequency signals, so that the cross-correlation function still retains the beat frequency phenomenon, and determining a time delay corresponding to a maximum value point of a real part of the cross-correlation function;

[0073] obtaining a distance difference between the target node and two antennas of the multi-antenna base station based on the time delay.

[0074] In some embodiments, a TDOA distance difference measurement method based on a chirp spread spectrum beat wave includes:

[0075] Step 1, the positioning system includes a target node for transmitting a measurement signal and a multi-antenna receiving base station with data processing and calculation functions, so that the lengths of the feed lines between the antennas and the RF chip of the base station are equal.

[0076] Step 2, at the transmitting end, the CSS baseband complex signal m(t) is quadrature modulated, and the local oscillator frequency is f cu during modulation, to obtain an RF signal s(t):

[0077]

[0078] Step 3, at the receiving end, only considering the far-field environment and the direct path, the received signal r i (t) of the receiving antenna i (i = 1, 2, 3…) is degraded to:

[0079] r i (t) = A i × s(t) + N i (t)

[0080] Step 4, at the receiving end, the received signal r i (t) is beat frequency quadrature demodulated, and the local oscillator frequency is f cd ≠ f cu during demodulation.

[0081]

[0082] y i (t) = I i (t) + jQ i (t)

[0083] Step 5, according to the Fourier frequency shift characteristic: multiply the beat frequency quadrature demodulated signal y i (t) by cosω BF t to obtain a beat wave with two superimposed frequencies and a strong and weak changing envelope, and the block diagram is shown inFigure 4 .

[0084] y iBF (t) = y i (t) cos ω BF t

[0085] Step 6, after processing the received signals of any two receiving antennas i, l (i≠l) into beat waves, the cross-correlation operation is performed to find the maximum value corr ilmax of the real part of the cross-correlation function and the corresponding time delay τ ilm .

[0086]

[0087] corr il (τ) = Re[R il (τ)]

[0088] corr il (τ ilm ) = corr ilmax

[0089] Step 7, the distance difference Δr ilm corresponding to the time delay τ il is calculated (continuous domain) ;

[0090] Δt il = -τ ilm (continuous domain)

[0091] Δr il = c × Δt il

[0092] where τ is the time delay, c is the speed of light 3 × 10 8 m / s, y iBF is the intermediate frequency signal after beat processing, T is the signal period; Re[R il (τ)] represents the real part operation of the cross-correlation function R il (τ), corr il (τ) is the result after taking the real part, corr ilmax represents the maximum value of the function corr il (τ), τ ilm represents the value of τ when the function corr il (τ) reaches the maximum value corr ilmax .

[0093] In some specific embodiments, the TDOA distance difference measurement method based on the chirp spread spectrum beat wave includes the following steps:

[0094] 1. Measurement model and problem modeling;

[0095] Known: A0 is a multi-antenna base station with data processing and operation functions, A 01 ,A 02 are two receiving antennas of base station A0, and their lengths of feeder to the RF chip of A0 are the same. T is a target node for transmitting measurement signals, r 01 ,r 02 are the distances from node T to antennas A 01 ,A 02 of base station A0 (see the attached Figure 1 ), and the distance difference Δr 12 = r 01 - r 02 is the target to be measured by the method. The implementation block diagram of the measurement system of the method is shown in the attached Figure 2 .

[0096] 2. At the transmitting end, the CSS baseband complex signal m(t) is quadrature modulated;

[0097] The local oscillator frequency during modulation is f cu = 470 MHz, and the RF signal s(t) is obtained:

[0098]

[0099] 3. At the receiving end, the 1st and 2nd antennas of the receiving base station receive signals r1(t) and r2(t) respectively;

[0100] There is a time difference Δt (Δt can be positive or negative) between r1(t) and r2(t), and r1(t) and r2(t) are expressed as:

[0101] r1(t) = A1cos[ω cu t + θ(t)] + N1(t)

[0102] r2(t) = A2cos[ω cu (t - Δt) + θ(t - Δt)] + N2(t)

[0103] N1(t) = N 1c (t)cosω cu t - N 1s (t)sinω cu t

[0104] N2(t) = N 2c (t)cosω cu t - N 2s (t)sinω cu t

[0105] N ic (t) is the co-directional component of noise Nt i (t), i = 1, 2

[0106] N is (t) is the orthogonal component of noise N i (t), i = 1, 2

[0107] 4. At the receiving end, the received two signals r1(t), r2(t) are subjected to the difference frequency orthogonal demodulation; the local frequency during the demodulation is f cd = 460.5 MHz ≠ f cu

[0108]

[0109] The above signals are subjected to the low-pass filter to filter out the high frequency part and adjust the amplitude, to obtain

[0110] I1(t) = A1cos[θ(t) + (ω cu - ω cd )t] + [N 1c (t)cos(ω cu - ω cd )t - N 1s (t)sin(ω cu - ω cd )t]

[0111] Similarly, the Q channel:

[0112]

[0113] The above signals are subjected to the low-pass filter to filter out the high frequency part and adjust the amplitude and direction, to obtain

[0114] Q1(t) = A1sin[θ(t) + (ω cu - ω cd )t] + [N 1c (t)sin(ω cu - ω cd )t + N 1s (t)cos(ω cu - ω cd )t]

[0115] The intermediate frequency complex signal is obtained;

[0116] y1(t) = I1(t) + jQ1(t) = A1{cos[θ(t) + (ω cu - ω cd )t] + jsin[θ(t) + (ω cu - ω cd )t]} + N 1y (t)

[0117] Noise N 1y(t) = [N 1c (t) + N 1s (t)] cos(ω cu - ω cd )t + [N 1c (t) - N 1s (t)] sin(ω cu - ω cd )t]

[0118] Similarly, the intermediate frequency signal y2(t) is obtained by heterodyne demodulation of the signal received by the antenna 2;

[0119] y2(t) = I2(t) + jQ2(t) = A2{cos[θ(t) + (ω cu - ω cd )t] + j sin[θ(t) + (ω cu - ω cd )t]} + N 2y (t)

[0120] 5. The intermediate frequency signal obtained by demodulation is processed by heterodyning;

[0121] According to the Fourier frequency shift property: The signal y i (t) obtained by heterodyne quadrature demodulation is multiplied by cosω BF t to obtain a beat wave with two frequency waves superimposed and a strong and weak envelope, and the block diagram is shown in FIG. 2. Figure 4 .

[0122] ω BF = 2πf BF (f BF = 1.42MHz)

[0123]

[0124] The real part of the signal y 1BF (t) is the superposition of signals with frequencies and . Similarly, the imaginary part of the signal y 1BF (t) is also the superposition of signals with frequencies and .

[0125] Similarly, the intermediate frequency signal of the antenna 2 channel after heterodyning is:

[0126]

[0127] 6. The two-way CSS beat wave is operated by cross-correlation to find the maximum cross-correlation value corr 12maxand its corresponding time delay τ 12m .

[0128] Generally, the sinusoidal signal and the random noise are not correlated, and the signals received by the two antennas pass through different channels to arrive, and the random signals N 1BF (t) are not correlated, so the signals y 2BF (t) can also be considered not correlated, so the cross-correlation function of y 1BF (t) and y 2BF (t) can be simplified to the cross-correlation function between the useful signals excluding the random noise signals.

[0129]

[0130] Using N-point participation operation in the discrete domain, the discrete time τ d is the discrete domain time delay, and

[0131]

[0132] corr 12 (τ d ) is a function of the independent variable τ d , when τ d = Δn, corr 12 reaches the maximum value

[0133]

[0134] On the contrary, find the maximum value corr 12 of the function corr d (τ 12max ), and its corresponding digital time delay is τ 12dm

[0135] (Discrete domain), then the time delay between the signal y 1BF (t) and the signal y 2BF (t) is

[0136] Δt 12 = -τ 12dm × T samp (discrete domain, T samp is the sampling period)

[0137] 7、Calculate the distance difference Δr 12 corresponding to the time delay Δt 12

[0138] Δr 12 = c × Δt 12

[0139] 8、About the distance difference measurement resolution

[0140] In digital discrete system, when corr 12 takes maximum value , There is an error of [0, T samp ) between the actual time difference in continuous domain and the measured time difference, so there is a measurement error of between the measured distance difference and the actual distance difference (F s is the sampling frequency), which is called distance difference measurement resolution.

[0141] There are two methods to improve the measurement resolution:

[0142] 1) If the hardware sampling rate of the hardware system allows, the sampling rate F a can be directly improved;

[0143] 2) If the hardware sampling rate of the hardware system is limited, one of the frequency-converted signals can be passed through a polyphase filter first, and then the correlation operation is performed with the other signal to achieve the purpose of improving the measurement resolution. The measurement resolution brought by the polyphase filter is determined by the number of phases of the polyphase filter. The higher the number of phases, the greater the measurement resolution brought.

[0144] Simulation case

[0145] Programming in MATLAB to simulate the measurement method;

[0146] Suppose in the discrete domain, the digital time delay of the Rx2 (antenna 2) channel signal r2(n) relative to the Rx1 (antenna 1) channel signal r1(n) is Δn = -8, that is, the signal r2(n) leads the signal r1(n), which is equivalent to Δr 12 = r 01 -r 02 = c x 8 x T samp ;

[0147] Under ideal conditions without noise interference (SNR = 60 dB), the received signals r1(n) and r2(n) are respectively difference frequency quadrature demodulated to obtain intermediate frequency signals y1(n) and y2(n); the waveform comparison between the intermediate frequency signal y1(n) (real part) obtained by the Rx1 channel and the baseband signal (real part) obtained by zero frequency reception is shown in FIG. 1. Figure 5 ;

[0148] The intermediate frequency signals y1(n) and y2(n) are respectively frequency-converted to obtain frequency waves y 1BF (n) and y 2BF (n). The frequency wave y 1BF (n) obtained by the Rx1 channel is composed of two frequencies with a difference of 2fBF The waveform (real part) and spectrum of the signals are superimposed and are shown in the appendix. Figure 6 ;

[0149] One beat frequency signal is delayed before and after, and then multiplied with the beat frequency signal of another channel by the conjugate of N points. The sum is then divided by N to obtain a range of values ​​for the cross-correlation function.

[0150] To reduce computational complexity, a threshold value `shift_th` can be applied to the beat frequency signal used for pre- and post-delay calculations. This threshold value is determined based on antenna A. 01 With A 02 The straight-line distance between |A 01 A 02 The reason is that, according to the properties of a triangle, the difference between any two sides of a triangle is less than the difference between the two sides of the third side; in the appendix... Figure 1 triangle ΔTA 01 A 02 In the middle, |Δr 12 |=|r 01 -r 02 |<|A 01 A 02 |,then Digital time difference Therefore, let the threshold For one beat frequency signal, delay it sequentially from -shift_th to +shift_th. Each delay is followed by conjugate multiplication with the beat frequency signal of another channel using N points of data, and the sum is accumulated. The accumulated sum is then divided by N to obtain a value of the cross-correlation function. After iterating through delays (-shift_th, +shift_th), a range of values ​​for the cross-correlation function is obtained. This range must contain the maximum value of the entire cross-correlation function (calculated using N points). The discrete time delay τ corresponding to the maximum real part of the cross-correlation function is... 12dm ∈(-shift th ,+shift_th).

[0151] In the simulation, in corr 12 When the value reaches its maximum value, the corresponding discrete time delay τ 12dm The value is -8, which is equal to the preset digital time difference Δn. The simulation result is correct. The simulation results are attached. Figure 7 (The data has been magnified several times for easier observation, so the vertical axis value of the simulation graph is relatively large).

[0152] The distance difference Δr can be obtained from this. 12 =r 01 -r 02 =c×8×T samp As assumed, the measurement is correct.

[0153] In the actual engineering environment, there are often random noises; in MATLAB simulation, different degrees of noise (SNR=0 dB, SNR=-9 dB, SNR=-15 dB) are added to the signal, and the received signals in different noise environments are processed by difference frequency quadrature demodulation and beat frequency after processing, and the waveform graph (real part) is shown in the following table and the following Figure 8 ;

[0154] In different noise environments, the maximum value and the corresponding discrete time delay τ 12 are obtained by cross-correlation operation, corr 12dm The simulation results are shown in the following table and the following Figure 9 (for the convenience of observation, the data is multiplied by a certain multiple, so the vertical coordinate value of the simulation graph is relatively large);

[0155]

[0156] After multiple simulations and tests, when SNR≥-7dB, the measurement method can ensure that the measurement result is completely correct;

[0157] When SNR=-9dB, the measurement method can still ensure 99% accuracy, and the accuracy can be ensured by removing extreme values through multiple measurements.

[0158] Embodiment 2

[0159] In a second aspect, the embodiment provides a TDOA distance difference measurement device based on a chirp spread frequency beat wave, including a processor and a storage medium.

[0160] The storage medium is used to store instructions.

[0161] The processor is used to operate according to the instructions to perform the steps of the method according to embodiment 1.

[0162] Embodiment 3

[0163] In a third aspect, the embodiment provides a storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the steps of the method of embodiment 1.

[0164] Embodiment 4

[0165] In a fourth aspect, the embodiment provides a computer device including one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for executing any one of the methods according to embodiment 1.

[0166] Those skilled in the art will appreciate that embodiments of the present application can be readily used as software, hardware, or a combination of software and hardware. In one embodiment, embodiments of the present application can be implemented in software and / or firmware. In this embodiment, the software implementation can include a computer program product which can include one or more computer program elements having computer readable program instructions stored in them which can be executed by one or more processors to implement the techniques of the present application. The computer program elements can be provided in the form of a program code to be executed by a processor of a computer or processor complex.

[0167] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions of the flow Figure 1 one or more functions specified in the flow or flows and / or blocks. Figure 1 one or more functions specified in the flow or flows and / or blocks.

[0168] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flow Figure 1 one or more functions specified in the flow or flows and / or blocks. Figure 1 one or more functions specified in the flow or flows and / or blocks.

[0169] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions of the flow Figure 1 one or more functions specified in the flow or flows and / or blocks. Figure 1 one or more functions specified in the flow or flows and / or blocks.

[0170] It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present application.

Claims

1. A TDOA range difference measurement method based on chirp spread spectrum beat wave, characterized in that, the positioning system comprises a target node and a multi-antenna receiving base station, and a chirp spread spectrum CSS signal after orthogonal modulation is used as a measurement signal; in response to the target node transmitting the chirp spread spectrum CSS signal after orthogonal modulation, receiving signals of at least any two receiving antennas in the multi-antenna receiving base station are obtained; the multi-antenna receiving base station has multiple receiving antennas, each antenna has the same specification, and the lengths of the feed lines between each antenna and a receiving end radio frequency chip are equal and adjustable; the receiving signals are subjected to beat orthogonal demodulation to obtain intermediate frequency signals; the intermediate frequency signals are subjected to beat processing to obtain beat signals; cross-correlation operation is performed on the two beat signals to determine a time delay corresponding to a maximum value point of a real part of a cross-correlation function; a range difference between the target node and two antennas on the multi-antenna base station is obtained based on the time delay.

2. The TDOA range difference measurement method based on chirp spread spectrum beat wave according to claim 1, characterized in that, the target node is used for transmitting a measurement signal, and the multi-antenna receiving base station is used for receiving the measurement signal and performing signal processing and range difference calculation; the target node for transmitting the measurement signal is located in a far field environment, and the measurement signal reaches each antenna of the multi-antenna receiving base station through a direct path; in the positioning system, the target node and any two receiving antennas of the receiving base station form a TDOA measurement system, and there is a range difference Δr between a to-be-measured transmitting device and the two antennas.

3. The method of claim 1, wherein the chirp spread frequency beat wave is generated by a laser source. the measurement signal uses a chirp spread spectrum CSS signal after orthogonal modulation, and a complex baseband signal m(t) is: Complex baseband signal m(t) = I(t) + jQ(t) = cos θ(t) + jsin θ(t) = e jθ(t) ; wherein I(t), Q(t) and j represent in-phase component, quadrature component and imaginary unit respectively; mod represents a modulo operation; μ is a spread spectrum modulation sweep slope; f0 is a sweep start frequency; BW is a signal bandwidth.

4. The TDOA range difference measurement method based on chirp spread spectrum beat wave according to claim 3, characterized in that, in the target node as a transmitting end, the baseband measurement signal is converted into a radio frequency signal s(t) through orthogonal modulation: where Re{} denotes the real part operation; ω cu = 2πf cu , f cu is the local oscillator frequency for quadrature modulation.

5. The method of claim 1, wherein the chirp spread frequency beat wave is generated by a laser. The radio frequency signal s(t) passes through a wireless channel to reach the antennas i of the multi-antenna receiving base station, i = 1, 2, 3, …, the received signal r i (t) is represented as: where h i (t) is the unit impulse response of the wireless channel i, N i (t) is a random noise signal of the channel i, denotes a convolution operation.

6. The method of claim 1, wherein the chirp spread frequency beat wave is generated by a laser. receiving a signal r i (t) performing heterodyne quadrature demodulation to obtain an intermediate frequency signal y i (t), comprising: y i (t) = I i (t) + jQ i (t) wherein the quadrature demodulation ω cd ≠ ω cu ; denotes passing the signal through a low-pass filter LPF; The intermediate frequency signal y i (t) is obtained by performing a beat processing on the signal x iBF (t) including: y iBF (t) = y i (t) cos ω BF t where ω BF = 2πf BF , f BF represents the frequency of the sinusoidal signal multiplied with the intermediate frequency signal y i (t).

7. The method of claim 1, wherein the chirp spread frequency beat wave is generated by a laser. cross-correlation operation is performed on the two beat signals to determine a time delay corresponding to a maximum value point of a real part of a cross-correlation function; a range difference between the target node and two antennas on the multi-antenna base station is obtained based on the time delay, including: In a TDOA system composed of the target node and the antennas i, l of the receiving base station, i≠l, the distance difference Δr il is measured by measuring the time difference Δt il between the two signals, and the distance difference Δr ilm is calculated according to the formula: Δr = c Δt il where c is the speed of light. il In a TDOA system composed of the target node and the antennas i, l of the receiving base station, i≠l, the distance difference Δr il is measured by measuring the time difference Δt il between the two signals, and the distance difference Δr ilm is calculated according to the formula: Δr = c Δt il where c is the speed of light. il In a TDOA system composed of the target node and the antennas i, l of the receiving base station, i≠l, the distance difference Δr il is measured by measuring the time difference Δt <000 corr il (τ) = Re[R il (τ)] corr il (τ ilm )=corr ilmax Δt il = -τ ilm (continuous domain) Δr il = c x Δt il where τ is the time delay, c is the speed of light 3 x 10 8 m / s, y iBF is the frequency-converted intermediate frequency signal, T is the signal period; Re[R il (τ)] represents the real part operation on the cross-correlation function R il (τ), corr il (τ) is the result after taking the real part, corr ilmax represents the maximum value of the function corr il (τ), τ ilm represents the value of τ when the function corr il (τ) reaches the maximum value corr ilmax .

8. A TDOA range difference measurement apparatus based on chirped spread spectrum beat waves, characterized by including a processor and a storage medium; the storage medium is used for storing instructions; the processor is used for operating according to the instructions to perform the steps of the method according to any one of claims 1 to 7.

9. A storage medium having stored thereon a computer program, characterized in that the computer program is executed by the processor to realize the steps of the method according to any one of claims 1 to 7.

10. A computer device, comprising: including one or more processors, one or more memories and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for executing any one of the methods according to claims 1 to 7.

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