A method for estimating ultra-bandwidth distance by incorporating carrier phase

Abstract

This invention relates to an ultra-wideband distance estimation method incorporating carrier phase, comprising the following steps: receiving a preamble sent by a UWB initiator, the preamble being divided into a first part and a second part, the carrier frequencies of the first part and the second part being different; determining the carrier phase values ​​of the first part and the second part based on the received preamble; completing a ranging process based on envelope information to obtain an estimated distance, and setting an error range between the estimated distance and the actual distance; calculating a first parameter based on the estimated distance, the carrier phase values ​​of the first part and the second part; determining the value range of a second parameter based on the error range between the estimated distance and the actual distance, the carrier wavelengths of the first part and the second part, and finding the second parameter that minimizes the objective function; and calculating the actual distance based on the first parameter and the second parameter. This invention can significantly improve the accuracy of UWB ranging and positioning.

Description

Technical Field

[0001] This invention relates to the field of time of arrival estimation technology, and in particular to an ultra-wideband distance estimation method that incorporates carrier phase. Background Technology

[0002] UWB systems are communication systems that transmit information using nanosecond-level pulses. Due to their short pulses and large bandwidth, they have an excellent ability to distinguish multipath signals. In complex environments such as indoors, they can accurately measure the time of flight of electromagnetic waves, enabling high-precision ranging and positioning. The bandwidth of a UWB system is generally above 500MHz, corresponding to a pulse duration of approximately 2ns.

[0003] The receiver estimates the arrival time (ATT) of a UWB signal by finding the first path signal in the channel impulse response of the preamble signal. After finding the approximate location of the first path signal in the channel impulse response, the next step is to perform an accurate ATT. The receiver extracts the amplitude values ​​of several accumulator sample points before and after the peak point of the first path. The sample points near the peak point should be discrete samples of the UWB pulse envelope. The accurate ATT is to match the time correspondence between the discrete points and the known envelope shape. The actual matching algorithm needs to consider a balance between computational complexity and accuracy. Many related papers have studied the ATT based on envelope, and the UWB standard 802.15.4 also has a specific algorithm description.

[0004] Existing time-of-arrival (TOA) estimation algorithms only process the amplitude information of the first path signal. They match several samples near the peak of the first path signal with a known envelope to estimate the peak position and thus obtain the TOA. However, due to the limited sampling frequency of UWB receiver ADCs (mostly 1 GHz), the duration of a single UWB pulse is approximately 2 ns, resulting in only about three effective sample points within the pulse – a relatively small number. Currently, mainstream UWB receivers using the aforementioned TOA estimation method can achieve a ranging accuracy of approximately ±6 cm.

[0005] The technical terms involved in this invention are explained as follows:

[0006] UWB: Ultra Wide Band

[0007] TOA: Time of Arrival

[0008] ADC: Analog to Digital Converter

[0009] TWR: Two-Way Ranging. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide an ultra-wideband distance estimation method that combines carrier phase, which can greatly improve the accuracy of UWB ranging and positioning.

[0011] The technical solution adopted by this invention to solve its technical problem is: to provide an ultra-bandwidth distance estimation method combining carrier phase, comprising the following steps:

[0012] (1) Receive the preamble sent by the UWB initiator, the preamble is divided into a first part and a second part, the carrier frequencies of the first part and the second part are different;

[0013] (2) Determine the carrier phase value of the first part and the carrier phase value of the second part based on the received preamble;

[0014] (3) Complete the ranging process based on the envelope information to obtain the estimated distance, and set the error range between the estimated distance and the actual distance;

[0015] (4) Calculate the first parameter based on the estimated distance, the carrier phase value of the first part, the carrier phase value of the second part, and the carrier wavelength of the first part and the carrier wavelength of the second part;

[0016] (5) Determine the range of values ​​for the second parameter based on the error range between the estimated distance and the actual distance, the carrier wavelength of the first part, and the carrier wavelength of the second part;

[0017] (6) Construct an objective function using the first parameter, the second parameter, the carrier frequency coefficient of the first part, and the carrier frequency coefficient of the second part, and find the second parameter when the objective function is minimized;

[0018] (7) Calculate the actual distance based on the first parameter, the second parameter, and the carrier wavelength of the first part or the carrier wavelength of the second part.

[0019] The carrier frequency of the first part is w1 = Mw0, and the carrier frequency of the second part is w2 = Nw0, where w0 is the reference frequency of the crystal oscillator, and M and N are the carrier frequency coefficients of the first part and the second part, respectively, and are coprime integers.

[0020] In step (4), through Calculate the first parameter, where k′ and j′ are the first parameters of the first part and the second part, respectively; R is the estimated distance, and λ1 and λ2 are the carrier wavelengths of the first part and the second part, respectively. Φ1 and Φ2 are the carrier phase values ​​of the first part and the second part, respectively. {·} indicates taking the fractional part, and mod(·,·) indicates taking the modulus.

[0021] The step (5) is through Determine the range of values ​​for the second parameter, where m′ and n′ are the second parameters of the first part and the second parameter of the second part, respectively, and E r The error range between the estimated distance and the actual distance is defined as λ1 and λ2, where λ1 and λ2 are the carrier wavelengths of the first part and the second part, respectively.

[0022] The objective function in step (6) is |(m′+k′)N-(n′+j′)M|, where k′ and j′ are the first parameters of the first part and the first parameters of the second part, respectively; m′ and n′ are the second parameters of the first part and the second parameters of the second part, respectively; and M and N are the carrier frequency coefficients of the first part and the second part, respectively.

[0023] In step (7), the actual distance is calculated by R0 = R + (m′ + k′)λ1 or R0 = R + (n′ + j′)λ2, where R0 represents the actual distance, k′ and j′ are the first parameters of the first part and the first parameters of the second part, respectively, m′ and n′ are the second parameters of the first part and the second parameters of the second part, respectively, R is the estimated distance, and λ1 and λ2 are the carrier wavelengths of the first part and the second part, respectively.

[0024] Beneficial effects

[0025] By adopting the above-mentioned technical solution, the present invention has the following advantages and positive effects compared with the prior art: By combining existing UWB time of arrival estimation methods and carrier phase information processing, the present invention greatly improves the accuracy of UWB time of arrival estimation, and can achieve millimeter-level ranging accuracy, thus greatly improving the ranging accuracy and positioning accuracy of the UWB system. Attached Figure Description

[0026] Figure 1 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] Embodiments of the present invention relate to an ultra-bandwidth distance estimation method that incorporates carrier phase, such as... Figure 1 As shown, it includes the following steps:

[0029] Receive a preamble sent by the UWB initiator. The preamble is divided into a first part and a second part, and the carrier frequencies of the first part and the second part are different.

[0030] Based on the received preamble, determine the carrier phase value of the first part and the carrier phase value of the second part;

[0031] The ranging process is completed based on the envelope information to obtain the estimated distance, and the error range between the estimated distance and the actual distance is set.

[0032] The first parameter is calculated based on the estimated distance, the carrier phase value of the first part, the carrier phase value of the second part, and the carrier wavelength of the first part and the carrier wavelength of the second part;

[0033] The range of values ​​for the second parameter is determined based on the error range between the estimated distance and the actual distance, the carrier wavelength of the first part, and the carrier wavelength of the second part.

[0034] An objective function is constructed using the first parameter, the second parameter, the carrier frequency coefficient of the first part, and the carrier frequency coefficient of the second part, and the second parameter is obtained when the objective function is minimized.

[0035] The actual distance is calculated based on the first parameter, the second parameter, and the carrier wavelength of the first part or the carrier wavelength of the second part.

[0036] The ranging method in this embodiment requires a UWB transmitter and a UWB receiver. The main functions of the UWB transmitter are pulse shaping and up-conversion. The carrier frequency and system clock frequency are obtained from the same crystal oscillator source through frequency multiplication. The mathematical expression for transmitting the UWB pulse signal is: Where s(t) is the pulse signal envelope, and w is the carrier frequency. This represents the initial phase of the carrier. In this embodiment, the transmitter needs to synchronize the envelope and the carrier to ensure the synchronization of each transmitted pulse. Let be a constant, without loss of generality, assume It is 0 degrees.

[0037] The UWB transmitter sends a preamble consisting of several repeatedly transmitted symbols. In this embodiment, the transmitter divides the preamble into a first part and a second part, with slightly different carrier frequencies. The mathematical expression for the pulse signal in the first part is as follows: The mathematical expression for the second part of the pulse signal is: In the UWB physical layer standard 802.15.4z, an STS segment was added. The STS segment is a scrambled and encrypted preamble signal, which is very suitable as the second preamble signal in this implementation.

[0038] Let the reference frequency of the crystal oscillator be w0, w1 = Mw0, w2 = Nw0, where M and N are the carrier frequency coefficients of the first part and the second part, respectively, and are coprime integers. Both w1 and w2 should be near the standard carrier frequency. For example, if the standard carrier frequency is 6489.6MHz and the crystal oscillator frequency is w0 = 38.4MHz, we can choose M = 169 and N = 168. Then w1 = Mw0 = 169 × 38.4MHz = 6489.6MHz, w2 = Nw0 = 168 × 38.4MHz = 6451.2MHz.

[0039] A signal with 128 preamble symbols is divided into two parts of 64 symbols each. The duration of each symbol is approximately 1µs, so the two parts are 64µs apart. At low speeds (<10m / s), the distance moved within 64µs is no more than 0.64mm, which can be ignored. Therefore, it can be approximated that the first and second parts are transmitted simultaneously.

[0040] The UWB receiver performs a normal ranging procedure at both the transmitting and receiving ends, receiving two preamble signals to obtain the carrier phase values ​​of the first and second parts: Φ1 and Φ2, both ranging from [0, 2π). The ranging distance R has already been estimated using envelope information. Assuming the actual distance is R0, and the ranging error is less than 10cm, the error range between the estimated and actual distance is E. r =0.1.

[0041] We have: R0 = R + ΔR = (m + k)λ1, where m ≥ 0 is an integer number of cycles.

[0042] Also: R0=R+ΔR=(n+j)λ2, where n≥0 is an integer number of cycles.

[0043] Since R is a known observation, subtracting R from both sides yields:

[0044] ΔR=(m′+k′)λ1=(n′+j′)λ2

[0045] Where m′ and n′ are the second parameters of the first part and the second parameter of the second part, respectively, and both are integers; k′ and j′ are the first parameters of the first part and the first parameter of the second part, respectively, where k′∈[0,1) and j′∈[0,1). Here, {·} represents taking the decimal part, and mod(·,·) represents taking the modulus, normalizing the result to [0,1). Since ΔR≤E r Then there must be In this embodiment, E r =0.1, therefore we have For a UWB signal with a carrier frequency of 6489.6MHz and a wavelength of approximately 4.6cm, then:

[0046] -3≤m′≤2

[0047] -3≤n′≤2

[0048] Based on the previous frequency settings, we have:

[0049] (m′+k′)λ1=(n′+j′)λ2

[0050] (m′+k′)N=(n′+j′)M

[0051] Considering the presence of noise, the solution for the second parameters m′ and n′ is derived from... Choose the value that minimizes (m′+k′)N-(n′+j′)M from the range of values.

[0052] After obtaining the second parameters m′ and n′, the actual distance can be calculated using R0=R+(m′+k′)λ1 or R0=R+(n′+j′)λ2.

[0053] Therefore, this invention, by combining existing UWB time of arrival estimation methods with carrier phase information processing, greatly improves the accuracy of UWB time of arrival estimation, achieving millimeter-level ranging accuracy and significantly enhancing the ranging and positioning accuracy of the UWB system.

Claims

1. A method for estimating ultra-bandwidth distance by incorporating carrier phase, characterized in that, Includes the following steps: (1) Receive the preamble sent by the UWB initiator, the preamble is divided into a first part and a second part, the carrier frequencies of the first part and the second part are different; (2) Determine the carrier phase value of the first part and the carrier phase value of the second part based on the received preamble; (3) Complete the ranging process based on the envelope information to obtain the estimated distance, and set the error range between the estimated distance and the actual distance; (4) Calculate the first parameter based on the estimated distance, the carrier phase value of the first part, the carrier phase value of the second part, and the carrier wavelength of the first part and the carrier wavelength of the second part; (5) Determine the range of values ​​for the second parameter based on the error range between the estimated distance and the actual distance, the carrier wavelength of the first part, and the carrier wavelength of the second part; (6) Construct an objective function using the first parameter, the second parameter, the carrier frequency coefficient of the first part, and the carrier frequency coefficient of the second part, and find the second parameter when the objective function is minimized; (7) Calculate the actual distance based on the first parameter, the second parameter, and the carrier wavelength of the first part or the carrier wavelength of the second part.

2. The ultra-bandwidth distance estimation method combining carrier phase according to claim 1, characterized in that, The carrier frequency of the first part is w1 = Mw0, and the carrier frequency of the second part is w2 = Nw0, where w0 is the reference frequency of the crystal oscillator, and M and N are the carrier frequency coefficients of the first part and the second part, respectively, and are coprime integers.

3. The ultra-bandwidth distance estimation method combining carrier phase according to claim 1, characterized in that, In step (4), through Calculate the first parameter, where k′ and j′ are the first parameters of the first part and the second part, respectively; R is the estimated distance, and λ1 and λ2 are the carrier wavelengths of the first part and the second part, respectively. Φ1 and Φ2 are the carrier phase values ​​of the first part and the second part, respectively. {·} indicates taking the fractional part, and mod(·,·) indicates taking the modulus.

4. The ultra-bandwidth distance estimation method combining carrier phase according to claim 1, characterized in that, The step (5) is through Determine the range of values ​​for the second parameter, where m′ and n′ are the second parameters of the first part and the second parameter of the second part, respectively, and E r The error range between the estimated distance and the actual distance is defined as λ1 and λ2, where λ1 and λ2 are the carrier wavelengths of the first part and the second part, respectively.

5. The ultra-bandwidth distance estimation method combining carrier phase according to claim 1, characterized in that, The objective function in step (6) is |(m′+k′)N-(n′+j′)M|, where k′ and j′ are the first parameters of the first part and the first parameters of the second part, respectively; m′ and n′ are the second parameters of the first part and the second parameters of the second part, respectively; and M and N are the carrier frequency coefficients of the first part and the second part, respectively.

6. The ultra-bandwidth distance estimation method combining carrier phase according to claim 1, characterized in that, In step (7), the actual distance is calculated by R0 = R + (m′ + k′)λ1 or R0 = R + (n′ + j′)λ2, where R0 represents the actual distance, k′ and j′ are the first parameters of the first part and the first parameters of the second part, respectively, m′ and n′ are the second parameters of the first part and the second parameters of the second part, respectively, R is the estimated distance, and λ1 and λ2 are the carrier wavelengths of the first part and the second part, respectively.

Images