A UWB doppler velocimetry method

Abstract

The application relates to a UWB Doppler velocity measurement method, which comprises the following steps: determining the time and sequence of the message sent by each UWB base station in a time-division manner; each UWB base station receives the signal sent by the UWB base station whose sending sequence is in front of itself, measures the actual carrier frequency difference between the UWB base station sending the signal, and sends the actual carrier frequency difference in the message; the tag receives the signal sent by all the UWB base stations, measures the Doppler frequency shift of all the UWB base stations, obtains the second Doppler frequency shift observation, calculates the carrier frequency difference based on the actual carrier frequency difference and the second Doppler frequency shift observation, and takes the i-th UWB base station as the reference; the equation of the carrier frequency difference and the tag speed listed by the observation of more than four UWB base stations is subjected to least square fitting to obtain the motion speed estimation of the tag. The application can estimate the moving speed of the tag, thereby effectively improving the positioning effect.

Description

TECHNICAL FIELD

[0001] The present application relates to a Doppler velocity measurement system, in particular to a UWB Doppler velocity measurement method. BACKGROUND

[0002] Doppler shift refers to the change of phase and frequency caused by the difference in propagation distance when the mobile station moves at a constant speed in a certain direction. It reveals the law of the change of wave properties in motion. When the motion is in front of the wave source, the wave is compressed, the wavelength becomes shorter, and the frequency becomes higher; when the motion is behind the wave source, the opposite effect occurs, the wavelength becomes longer, and the frequency becomes lower.

[0003] The velocity measurement technology using Doppler shift is widely used in GNSS system and can achieve quite high velocity measurement accuracy. The UWB receiver, like the GNSS receiver, can output the Doppler frequency difference between the two ends of transmission and reception. However, the UWB base station generally uses a cheap temperature-compensated crystal oscillator (TCXO), and its frequency accuracy is about 1 PPM. Since different crystal oscillators have different frequencies, the Doppler frequency difference observation of the UWB receiver has not been well applied in the positioning system, and the moving speed of the target to be positioned (hereinafter referred to as the tag) cannot be estimated. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a UWB Doppler velocity measurement method, which can estimate the moving speed of the tag, thereby effectively improving the positioning effect.

[0005] The technical solution adopted by the present application to solve the technical problem is to provide a UWB Doppler velocity measurement method, comprising the following steps:

[0006] determining the time and order of sending messages by each UWB base station in a time-division manner;

[0007] each UWB base station receives the signal sent by the UWB base station in front of itself in the order of sending messages, and measures the actual carrier frequency difference between the UWB base station sending the signal and itself, and at the time of sending the signal, the actual carrier frequency difference is sent together in the message;

[0008] the tag receives the signal sent by all UWB base stations, measures the Doppler shift of all UWB base stations to obtain a second Doppler shift observation, reads the actual carrier frequency difference attached in the message, and calculates the carrier frequency difference based on the actual carrier frequency difference and the second Doppler shift observation with the i-th UWB base station as the reference;

[0009] The carrier frequency difference and tag velocity equations derived from observations of more than four UWB base stations are fitted using least squares to obtain an estimate of the tag's motion velocity.

[0010] When determining the time and order of message transmission for each UWB base station in a time-division manner, the overall UWB downlink frame is divided into several subframes. Each subframe corresponds to a UWB base station. Each subframe includes one message transmission opportunity and a protection time. Each UWB base station transmits signals in its corresponding subframe and receives signals in other subframes.

[0011] The actual carrier frequency difference is: ,in, Indicates the first The actual carrier frequency difference between the i-th UWB base station and the i-th UWB base station Indicates the first The actual carrier frequency of each UWB base station This represents the actual carrier frequency of the i-th UWB base station. This indicates the number of UWB base stations.

[0012] The second Doppler frequency shift observation is: ,in, Indicates the label and the first Doppler frequency shift between UWB base stations This indicates the actual carrier frequency of the tag. Indicates the first The actual carrier frequency of each UWB base station This indicates the number of UWB base stations.

[0013] The carrier frequency difference based on the i-th UWB base station is: ,in, This represents the carrier frequency difference relative to the i-th UWB base station. Indicates the label and the first Doppler frequency shift between UWB base stations Indicates the first The actual carrier frequency difference between the i-th UWB base station and the i-th UWB base station.

[0014] The equation for the carrier frequency difference and tag velocity, derived from observations from more than four UWB base stations, is fitted using least squares to obtain an estimate of the tag's motion velocity. Specifically: Let... of dimensional column vector, where, Let be the carrier wavelength; denoted as for A four-row matrix They represent from the first The location of each base station points to the tag location. direction, direction and A vector of direction; denoted as It is a four-dimensional column vector, where, These respectively represent the tags in direction, direction and The velocity vector in the direction, Represent the carrier frequency difference between the tag and the reference base station; solve The least squares solution is obtained. .

[0015] Beneficial effects

[0016] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: The present invention designs a communication mechanism between UWB base stations to realize mutual Doppler frequency shift measurement between UWB base stations and send the measurement results to the tag. The tag measures the Doppler frequency shift between itself and each UWB base station, and at the same time receives the Doppler frequency shift observation between UWB base stations. Thus, it is possible to use the Doppler frequency shift observation to realize motion speed estimation and enhance the system positioning effect. Attached Figure Description

[0017] Figure 1 This is a flowchart of an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the overall UWB downlink frame structure in an embodiment of the present invention. Detailed Implementation

[0019] 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.

[0020] The embodiments of the present invention relate to a UWB Doppler velocity measurement method, such as... Figure 1 As shown, it includes the following steps:

[0021] Step 1: Determine the time and order of message transmission for each UWB base station using a time-division multiplexing method. This step designs a communication mechanism between UWB base stations; specifically, as follows... Figure 2As shown, the overall UWB downlink frame is divided into several subframes, each subframe corresponds to a UWB base station, each subframe includes one message transmission opportunity and a protection time G. Each UWB base station transmits signals in its corresponding subframe and receives signals in other subframes, thereby realizing time division multiplexing between different UWB base stations.

[0022] Step 2: Each UWB base station receives signals sent by UWB base stations that precede it in the transmission sequence, measures the actual carrier frequency difference between itself and the UWB base station that sent the signal, and includes the actual carrier frequency difference in the message when it transmits its own signal.

[0023] In this step, when a UWB base station receives signals from other UWB base stations, it measures the actual carrier frequency difference with other UWB base stations and piggybacks this difference in the next transmitted information. The calculation method for the actual carrier frequency difference is as follows: ,in, Indicates the first The actual carrier frequency difference between the i-th UWB base station and the i-th UWB base station Indicates the first The actual carrier frequency of each UWB base station This represents the actual carrier frequency of the i-th UWB base station. This indicates the number of UWB base stations.

[0024] Step 3: The tag receives signals transmitted by all UWB base stations and measures the Doppler frequency shift of all UWB base stations to obtain the second Doppler frequency shift observation. At the same time, it reads the actual carrier frequency difference attached to the message and calculates the carrier frequency difference based on the i-th UWB base station based on the actual carrier frequency difference and the second Doppler frequency shift observation.

[0025] In this step, the tag receives signals from each UWB base station in the order they were transmitted. After receiving the signals, the tag... The Doppler frequency shift between the tag and the UWB base station is calculated to obtain the second Doppler frequency shift observation, where, Indicates the label and the first Doppler frequency shift between UWB base stations This represents the actual carrier frequency of the tag. Assuming the first base station is used as a reference, the actual carrier frequency difference is: Comprehensive utilization of second Doppler frequency shift observations Difference from actual carrier frequency This allows us to obtain an estimate of the carrier frequency difference based on the first base station: .

[0026] It's easy to see that choosing which UWB base station to use as the reference does not affect the subsequent speed estimation results, and the crystal oscillator deviation of the reference base station also does not affect the subsequent speed estimation results. Different UWB base stations will have some time differences in transmission, so the Doppler frequency difference estimations for different UWB base stations are not strictly simultaneous. However, since the transmission time of UWB base stations is approximately 200µs, the overall time difference is very short and has little impact on the speed estimation.

[0027] Step 4: Using the carrier frequency difference and tag velocity equation derived from observations from more than four UWB base stations, least squares fitting is performed to obtain an estimate of the tag's motion velocity. Specifically, after obtaining the estimated carrier frequency difference... Next, the tag's moving speed can be estimated. The difference between UWB and GNSS systems lies not only in the different crystal oscillator frequencies between base stations, but also in the fact that the base station positions are known and unchanging, and the base station's moving speed is zero. Therefore, the following equation can be derived:

[0028]

[0029] in, Indicates the carrier wavelength (known). The carrier frequency difference is an estimated value (known). The three-dimensional velocity vector of the label (unknown). Let be the direction vector (known) pointing from the location of the I-th UWB base station to the tag location. The carrier frequency difference between the tag and the reference base station is unknown. Since there are four unknowns in the above equation, the tag's motion velocity can be estimated by performing a least-squares fit on the equation derived from observations from more than four UWB base stations.

[0030] When performing least squares fitting, let of dimensional column vector, ;remember for A four-row matrix They represent from the first The location of each base station points to the tag location. direction, direction and A vector of direction; denoted as It is a four-dimensional column vector, where, These respectively represent the tags in direction, direction and The velocity vector in the direction. The original equation can be expressed as: The least squares solution to this equation is: Therefore, a speed estimate can be obtained. The impact of choosing different reference base stations and the frequency error of the reference base stations is reflected in... middle.

[0031] Therefore, this invention designs a communication mechanism between UWB base stations to realize mutual Doppler frequency shift measurement between UWB base stations and send the measurement results to the tag. The tag measures the Doppler frequency shift between itself and each UWB base station, and at the same time receives the Doppler frequency shift observation between UWB base stations. Thus, the Doppler frequency shift observation can be used to estimate the motion speed and enhance the system positioning effect.

Claims

1. A UWB Doppler velocity measurement method, characterized in that, Includes the following steps: The time and order in which each UWB base station sends messages are determined using a time-division method. Each UWB base station receives signals sent by the UWB base station that precedes it in the order of sending messages, and measures the actual carrier frequency difference between itself and the UWB base station that sent the signal. When it sends its own signal, it includes the actual carrier frequency difference in the message and sends it together. The tag receives signals transmitted by all UWB base stations and measures the Doppler frequency shift of all UWB base stations to obtain a second Doppler frequency shift observation. At the same time, it reads the actual carrier frequency difference attached to the message and calculates the carrier frequency difference based on the i-th UWB base station based on the actual carrier frequency difference and the second Doppler frequency shift observation. The carrier frequency difference and tag velocity equations derived from observations of more than four UWB base stations are fitted using least squares to obtain an estimate of the tag's motion velocity.

2. The UWB Doppler velocity measurement method according to claim 1, characterized in that, When determining the time and order of message transmission for each UWB base station in a time-division manner, the overall UWB downlink frame is divided into several subframes. Each subframe corresponds to a UWB base station. Each subframe includes one message transmission opportunity and a protection time. Each UWB base station transmits signals in its corresponding subframe and receives signals in other subframes.

3. The UWB Doppler velocity measurement method according to claim 1, characterized in that, The actual carrier frequency difference is: ,in, Indicates the first The actual carrier frequency difference between the i-th UWB base station and the i-th UWB base station Indicates the first The actual carrier frequency of each UWB base station This represents the actual carrier frequency of the i-th UWB base station. This indicates the number of UWB base stations.

4. The UWB Doppler velocity measurement method according to claim 1, characterized in that, The second Doppler frequency shift observation is: ,in, Indicates the label and the first Doppler frequency shift between UWB base stations This indicates the actual carrier frequency of the tag. Indicates the first The actual carrier frequency of each UWB base station This indicates the number of UWB base stations.

5. The UWB Doppler velocity measurement method according to claim 1, characterized in that, The carrier frequency difference based on the i-th UWB base station is: ,in, This represents the carrier frequency difference relative to the i-th UWB base station. Indicates the label and the first Doppler frequency shift between UWB base stations Indicates the first The actual carrier frequency difference between the i-th UWB base station and the i-th UWB base station.

6. The UWB Doppler velocity measurement method according to claim 1, characterized in that, The equation for the carrier frequency difference and tag velocity, derived from observations from more than four UWB base stations, is fitted using least squares to obtain an estimate of the tag's motion velocity. Specifically: Let... of dimensional column vector, where, Let be the carrier wavelength; denoted as for A four-row matrix They represent from the first The location of each base station points to the tag location. direction, direction and A vector of direction; denoted as It is a four-dimensional column vector, where, These respectively represent the tags in direction, direction and The velocity vector in the direction, Represent the carrier frequency difference between the tag and the reference base station; solve The least squares solution is obtained. .

Images