CN112083450B - Method, system and device for suppressing multipath errors using antenna circular motion - Google Patents

Abstract

The invention discloses a multipath error suppression method, a system and a device using antenna circular motion, wherein the method comprises the following steps: constructing an antenna circular motion model and obtaining the maximum multipath frequency; obtaining a minimum fault-tolerant multipath frequency according to the single reflection model; obtaining preset circular motion parameters according to the maximum multipath frequency and the minimum fault tolerance multipath frequency; collecting observation data and calculating actual multipath frequency; and evaluating multipath inhibition performance by adopting code multipath error and statistical characteristics thereof, and adjusting circular motion parameters according to the maximum multipath frequency, the minimum fault-tolerant frequency and the actual multipath frequency. The invention can provide a technical scheme for solving the problem that the positioning accuracy is limited due to multipath error for the user-level navigation receiver. The method, the system and the device for restraining the multipath error by utilizing the circular motion of the antenna can be widely applied to the field of satellite navigation.

Description

A method, system and device for suppressing multipath errors using antenna circular motion

technical field

The invention relates to the field of satellite navigation, in particular to a method, system and device for suppressing multipath errors by using antenna circular motion.

Background technique

For satellite navigation, multipath error is still an error variable that cannot be modeled accurately and cannot be completely eliminated. Due to the complex and diverse environment around the navigation receiver and the ups and downs of the obstructions, it is inevitable to bring multipath signals to the receiver. The complexity of multipath also limits researchers to accurately model it. The impact of the data correlation from the data also has a certain impact on the positioning algorithm. Therefore, it is particularly important to implement multipath suppression technology. Usually, in order to reduce the impact of multipath effects, the observation environment usually chooses a scene with open sky and few occluders, and avoids environments with severe reflection of multipath signals such as hillsides and water surfaces. The multipath error time series is a non-stationary random process, which brings great challenges and influences to the high-precision positioning algorithm.

Due to the complexity and non-correlation characteristics of multipath in space, it brings many difficulties to multipath modeling. It is particularly important to use the characteristics and influence laws of multipath errors.

Contents of the invention

In order to solve the above technical problems, the object of the present invention is to provide a method, system and device for suppressing multipath errors using antenna circular motion, which can solve the technical problem that the positioning accuracy of the receiver is limited due to multipath errors at low cost.

The first technical solution adopted in the present invention is: a method for suppressing multipath errors utilizing circular motion of the antenna, comprising the following steps:

Construct the circular motion model of the antenna and obtain the maximum multipath frequency;

Obtain the minimum fault-tolerant multipath frequency according to the single reflection model;

Obtain preset circular motion parameters according to the maximum multipath frequency and the minimum fault-tolerant multipath frequency;

Collect observation data and calculate actual multipath frequency;

The code multipath error and its statistical characteristics are used to evaluate the multipath suppression performance, and the circular motion parameters are adjusted according to the maximum multipath frequency, the minimum error tolerance frequency and the actual multipath frequency.

Further, the step of constructing the circular motion model of the antenna and obtaining the maximum multipath frequency is described, which specifically includes:

According to the multipath reflection model of the user receiver, the antenna circular motion model is constructed and the preset circular motion parameters are obtained.

The maximum multipath frequency is obtained according to the preset circular motion parameters.

Further, the expression of the maximum multipath frequency is specifically:

In the above formula, the r represents the radius of the circular motion, ω represents the angular velocity of the object doing the circular motion, and λ is the wavelength of the signal.

Further, the step of obtaining the minimum fault-tolerant multipath frequency according to the single reflection model specifically includes:

Obtain an acceptable maximum multipath error according to user characteristics;

The minimum error-tolerant frequency is obtained according to the maximum multipath error and the multipath delay and multipath frequency model derived from the single reflection model.

Further, the expression of the model of the multipath delay and multipath frequency is specifically:

为高度角的变化率，δ表示为当前时刻下的多径延迟，λ为信号的波长。In the above formula,

is the rate of change of the altitude angle, δ is the multipath delay at the current moment, and λ is the wavelength of the signal.

Further, the step of collecting observation data and calculating the actual multipath frequency specifically includes:

Collect a set of GNSS observation data whose sampling frequency is a preset value;

Perform fast Fourier transform processing on GNSS observations to extract the actual multipath frequency.

Further, the GNSS observation data includes carrier-to-noise ratio data and pseudo-range observation data.

Further, the step of evaluating the multipath suppression performance by using the code multipath error and its statistical characteristics and adjusting the circular motion parameters according to the maximum multipath frequency, the minimum error tolerance frequency and the actual multipath frequency is specifically:

According to the code multipath error and its statistical characteristics, it is judged that the multipath error suppression performance of the circular motion of the antenna exceeds the preset range, and the code multipath error is recalculated after adjusting the circular motion parameters according to the maximum multipath frequency, minimum error tolerance frequency and actual multipath frequency and its statistical characteristics, until the multipath error suppression performance of the circular motion of the antenna judged by using the code multipath error and its statistical characteristics is within a preset range.

The second technical solution adopted by the present invention is: a multipath error suppression system utilizing circular motion of the antenna, including: an upper limit module, which is used to construct a circular motion model of the antenna and obtain the maximum multipath frequency;

The lower limit module is used to obtain the minimum fault-tolerant multipath frequency according to the single reflection model;

A circular motion parameter module, configured to obtain preset circular motion parameters according to the maximum multipath frequency and the minimum fault-tolerant multipath frequency;

The multipath frequency extraction module is used to collect observation data and calculate the actual multipath frequency;

The multipath performance evaluation module is used to evaluate the multipath suppression performance by using the code multipath error and its statistical characteristics, and adjust the circular motion parameters according to the maximum multipath frequency, the minimum error-tolerant multipath frequency and the actual multipath frequency.

The third technical solution adopted by the present invention is: a multipath error suppression device utilizing antenna circular motion, comprising: at least one processor;

at least one memory for storing at least one program;

When the at least one program is executed by the at least one processor, the at least one processor is enabled to implement the method for suppressing multipath errors by using circular motion of the antenna as described above.

The beneficial effects of the method, system and device of the present invention are: the present invention obtains the preset circular motion parameters according to the theoretical limit value of the multipath frequency, evaluates the multipath suppression performance by calculating the code multipath error and its statistical characteristics, and adjusts the circular motion according to the evaluation result Motion parameters or circular motion parameters are determined, and the final circular motion parameters can be used for subsequent multipath suppression, and the low-cost solution for user-level navigation receivers is the problem of poor positioning accuracy caused by multipath errors.

Description of drawings

Fig. 1 is a flow chart of the steps of multipath error suppression utilizing antenna circular motion in the present invention;

Fig. 2 is a structural block diagram of a multipath error suppression system utilizing antenna circular motion in the present invention;

Fig. 3 is the multipath reflection model under the circular motion of the specific embodiment of the present invention;

Fig. 4 is a reflection model of a single-path multi-path signal at any time according to a specific embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. For the step numbers in the following embodiments, it is only set for the convenience of illustration and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art sexual adjustment.

As shown in Figure 1, the present invention provides a kind of multipath error suppression method utilizing antenna circular motion, and this method comprises the following steps:

S101. Construct an antenna circular motion model and obtain a maximum multipath frequency.

S102. Obtain the minimum fault-tolerant multipath frequency according to the single reflection model;

S103. Obtain preset circular motion parameters according to the maximum multipath frequency and the minimum fault-tolerant multipath frequency;

S104. Collect observation data and calculate an actual multipath frequency.

S105. Evaluate the multipath suppression performance by using code multipath errors and their statistical characteristics, and adjust circular motion parameters according to the maximum multipath frequency, the minimum error tolerance frequency, and the actual multipath frequency.

Further as a preferred embodiment of the method, the step of constructing the antenna circular motion model and obtaining the maximum multipath frequency specifically includes:

Construct the circular motion model of the antenna according to the multipath reflection model of the user receiver and obtain the preset circular motion parameters;

The maximum multipath frequency is obtained according to the preset circular motion parameters.

Specifically, under the circular motion of the antenna, the multipath reflection model of the user receiver is shown in Figure 3. According to this model, the expression of the multipath delay distance can be obtained as:

Among them, m(t) is PU( _t )-P _F (t), which is the distance vector of multipath delay from the position of the reflection point to the position of the user receiver, and d(t) is _PU (t)-P _S (t), expressed as the distance vector of the direct signal from the satellite pointing to the position of the user receiver, time t indicates the current observation epoch, _PS (t) indicates the real-time position of the satellite moving along the trajectory, P _U (t), _PF (t) respectively represent the real-time positions of the user receiver antenna and the multipath reflection point in the ECEF coordinate system.

The multipath phase can be calculated from the multipath delay distance:

Among them, λ is the wavelength of a certain frequency band signal, for example, the wavelength of a GPS satellite L1 frequency band signal is 19.04cm.

In order to further obtain the multipath variation under circular motion, the multipath frequency is introduced, and the multipath frequency is further expressed as:

Among them, P _⊥d(t) is the projection matrix projected to the orthogonal space of d(t); v _U (t) is P _U (t)/dt, and v _F (t) is the same as v _S (t) . Since |d(t)| is much larger than the relative motion between the satellite and the receiver, it is further simplified to get:

The upper limit of the multipath frequency is further obtained by using the above circular motion parameters.

Further as a preferred embodiment of the method, the expression of the maximum multipath frequency is specifically:

In the above formula, the r represents the radius of the circular motion, ω represents the angular velocity of the object doing the circular motion, and λ is the wavelength of the signal.

Specifically, the upper limit of the multipath frequency can be used to control the circular motion parameters r, ω.

Further as a preferred embodiment of the method, the step of obtaining the minimum fault-tolerant multipath frequency according to the single reflection model specifically includes:

Obtain an acceptable maximum multipath error according to user characteristics;

The minimum error-tolerant frequency is obtained according to the maximum multipath error and the multipath delay and multipath frequency model derived from the single reflection model.

Specifically, referring to Figure 4, using the static ground single reflection model, the multipath delay at this moment can be expressed as:

δ＝2h sin(β)

Wherein, h is the vertical distance between the receiver antenna and the ground, and β is the angle between the multipath signal and the ground. In particular, it is regarded as the altitude angle of the receiver relative to the satellite. The phase delay can be expressed as:

Further as a preferred embodiment of the method, the expression of the model of the multipath delay and multipath frequency is specifically:

为高度角的变化率，δ表示为当前时刻下的多径延迟，λ为信号的波长。In the above formula,

is the rate of change of the altitude angle, δ is the multipath delay at the current moment, and λ is the wavelength of the signal.

Specifically, it can be known from the above formula that in a short period of time, the multipath frequency generated by the reflective object closer to the receiver is smaller, and what is reflected in the carrier-to-noise ratio time series is a slower oscillation with a smaller amplitude; The multipath frequency generated by far reflecting objects is relatively large, which is reflected in the carrier-to-noise ratio time series as faster and larger amplitude oscillations. The long-delay reflected signal will be filtered out when the receiver performs signal tracking. The multipath frequency expression can determine the minimum theoretical value that the multipath frequency needs to reach according to the maximum fault-tolerant multipath error.

Further as a preferred embodiment of the method, the step of collecting observation data and calculating the actual multipath frequency specifically includes:

Collect a set of GNSS observation data whose sampling frequency is a preset value;

Perform fast Fourier transform processing on GNSS observations to extract the actual multipath frequency.

Specifically, in the actual observation, the receiver mainly stores four types of observation data: pseudorange, carrier phase, carrier-to-noise ratio, and Doppler frequency shift, and the carrier-to-noise ratio (C/N ₀ ) can best reflect the multipath effect zone coming changes.

The C/N ₀ mathematical model under circular motion can be expressed as:

C/N ₀ ≡A _C ＝A _d +A _f cos(ΔΦ(t))

Among them, _AC represents the amplitude of the composite signal, A _d and A _f represent the amplitude of the direct signal and the reflected signal respectively, ΔΦ(t) represents the carrier phase deviation caused by the additional propagation distance, which can be expressed by the multipath frequency, ΔΦ(t) =2πf _mp t+Δφ ₀ . The multipath frequency oscillation due to antenna movement should be independent of the initial phase, and C/N ₀ can be transformed into:

C/N ₀ ≡A _C ＝A _d +A _f cos(2πf _mp t)

The carrier-to-noise ratio variation caused by multipath effects can be expressed by the carrier-to-noise ratio residual:

C/N ₀ _RES＝C/N ₀ -MA(C/N ₀ )

Wherein, MA(C/N ₀ ) means that the moving average processing is performed on C/N ₀ . Perform fast Fourier transform (FFT) transformation on the carrier-to-noise ratio residual sequence to extract the multipath frequency.

Given a time series x[k] randomly sampled at time interval T, its discrete Fourier transform (DFT) is mathematically defined as:

为旋转因子，N为离散采样的总点数。采用频率抽取2FFT简化计算，设N＝2^M，将x[k]划分为两个部分进行下列分解：In the formula,

is the rotation factor, and N is the total number of discrete sampling points. Use frequency extraction 2FFT to simplify the calculation, set N=2 ^M , divide x[k] into two parts for the following decomposition:

Divide into two groups according to the parity difference of m, and get:

In the above formula, l=0,1,...,N/2-1. Convert the N-point DFT operation into M-point FFT operation, and decompose and iterate to complete the calculation. Therefore, the multipath frequency under the actual circular motion can be extracted from the result of the FFT operation.

Further as a preferred embodiment of the method, the GNSS observation data includes carrier-to-noise ratio data and pseudorange observation data.

Further as a preferred embodiment of this method, the step of evaluating the multipath suppression performance by using the code multipath error and its statistical characteristics and adjusting the circular motion parameters according to the maximum multipath frequency, the minimum error tolerance frequency and the actual multipath frequency, is specifically for:

According to the code multipath error and its statistical characteristics, it is judged that the multipath error suppression performance of the circular motion of the antenna exceeds the preset range, and the code multipath error is recalculated after adjusting the circular motion parameters according to the maximum multipath frequency, minimum error tolerance frequency and actual multipath frequency and its statistical characteristics, until the multipath error suppression performance of the circular motion of the antenna judged by the calculated code multipath error and its statistical characteristics is within a preset range.

Specifically, the carrier-to-noise ratio sequence is used to perform FFT transformation to extract the multipath frequency, combined with the statistical characteristics obtained by the multipath error calculation of the code, it is fed back to the selection of the upper limit of the multipath frequency, and the motion parameters are further adjusted.

The code multipath error and its statistical characteristics are used to evaluate the multipath error suppression performance of the circular motion of the antenna. The pseudorange mathematical model of any satellite signal in any frequency band is expressed as:

P＝ρ+c(t _r -t ^s )+I+T+MP _P +d _r +d ^s +ε _p

In the formula, P is the pseudo-range observation, the unit is m, ρ is the relative distance between the satellite and the user receiver, the unit is m, c is the speed of light, t _r and t ^s are the clocks on the receiver and the satellite respectively Difference, the unit is s, I and T respectively represent the delay caused by the signal passing through the ionosphere and troposphere, the unit is m, MP _P represents the multipath error on the pseudo-range observation value, also known as the code multipath error, the unit m, d _r , d ^s represent the hardware delay between the receiver and the satellite, ε _p is the random error on the pseudorange, d _r , d ^s , ε _p are generally small and can be ignored.

After the position velocity time (PVT) solution, the code multipath error can be calculated, and the mathematical expression is:

MP _P ＝P-(ρ+c(t _r -t ^s )+I+T)

Specific embodiments of the present invention are as follows:

Collect a set of GNSS observation data with a sampling frequency of 1 Hz (including observation data of carrier-to-noise ratio and pseudo-range observation value), and perform fast Fourier transform on the carrier-to-noise ratio data to calculate the multipath frequency. The message data determines the multipath frequency characteristics in a static environment and the statistical characteristics of code multipath errors (probability distribution, STD, RMS, etc.). Collect a set of observation data with motion parameters as empirical values, determine the circular motion parameters suitable for this type of navigation equipment according to the flow chart in Figure 1, and evaluate the multipath suppression effect of this method, if the multipath suppression performance is not good, readjust the motion parameters; if the performance is good, the determined motion parameters are used for subsequent multipath suppression.

As shown in Figure 2, a multipath error suppression system using antenna circular motion includes:

The upper limit module is used to construct the circular motion model of the antenna and obtain the maximum multipath frequency;

The lower limit module is used to obtain the minimum fault-tolerant multipath frequency according to the single reflection model;

A circular motion parameter module, configured to obtain preset circular motion parameters according to the maximum multipath frequency and the minimum fault-tolerant multipath frequency;

The multipath frequency extraction module is used to collect observation data and calculate the actual multipath frequency;

The multipath performance evaluation module is used to evaluate the multipath suppression performance by using the code multipath error and its statistical characteristics, and adjust the circular motion parameters according to the maximum multipath frequency, the minimum error tolerance frequency and the actual multipath frequency.

The content in the above-mentioned method embodiments is applicable to this system embodiment. The functions realized by this system embodiment are the same as those of the above-mentioned method embodiments, and the beneficial effects achieved are also the same as those achieved by the above-mentioned method embodiments.

A multipath error suppression device using antenna circular motion:

at least one processor;

at least one memory for storing at least one program;

When the at least one program is executed by the at least one processor, the at least one processor is enabled to implement the method for suppressing multipath errors by using circular motion of the antenna as described above.

The content in the above-mentioned method embodiment is applicable to this device embodiment, and the specific functions realized by this device embodiment are the same as those of the above-mentioned method embodiment, and the beneficial effects achieved are also the same as those achieved by the above-mentioned method embodiment.

The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the described embodiments, and those skilled in the art can also make various equivalent deformations or replacements without violating the spirit of the present invention. , these equivalent modifications or replacements are all within the scope defined by the claims of the present application.

Claims (6)

1. A multipath error mitigation method utilizing circular motion of an antenna, comprising the steps of:

constructing an antenna circular motion model and obtaining the maximum multipath frequency;

obtaining the minimum fault-tolerant multipath frequency of the user according to the single reflection model;

obtaining preset circular motion parameters according to the maximum multipath frequency and the minimum fault tolerance multipath frequency;

collecting observation data and calculating actual multipath frequency;

adopting code multipath error and its statistical characteristic to evaluate multipath inhibition performance and regulating circular motion parameter according to maximum multipath frequency, minimum fault-tolerant frequency and actual multipath frequency;

the step of constructing the antenna circular motion model and obtaining the maximum multipath frequency specifically comprises the following steps:

constructing an antenna circular motion model according to a multipath delay mathematical model of a user receiver and obtaining preset circular motion parameters;

obtaining the maximum multipath frequency according to the preset circular motion parameters;

the expression of the maximum multipath frequency is specifically:

in the above formula, r represents the radius of circular motion, ω represents the angular velocity of the circular motion of the object, and λ is the wavelength of the satellite signal;

the step of obtaining the minimum fault-tolerant multipath frequency of the user according to the single reflection model specifically comprises the following steps:

obtaining an acceptable maximum multipath error according to the user characteristics;

deducing a model of multipath delay and multipath frequency according to the maximum multipath error and through a single reflection model to obtain the minimum fault-tolerant frequency;

the expression of the model of the multipath delay and the multipath frequency is specifically as follows:

in the above-mentioned method, the step of,

delta is the rate of change of the altitude angle, delta is the multipath delay at the current time, and lambda is the wavelength of the signal.

2. The method of claim 1, wherein the step of acquiring the observation data and calculating the actual multipath frequency comprises:

collecting a group of GNSS observation data with a sampling frequency of a preset value;

and performing fast Fourier transform processing on the GNSS observation, and extracting to obtain the actual multipath frequency.

3. A method of multipath error mitigation utilizing circular motion of an antenna according to claim 2, wherein the GNSS observations comprise carrier-to-noise ratio data and pseudorange observations data.

4. A multipath error mitigation method utilizing circular motion of an antenna according to claim 3, wherein the step of evaluating multipath mitigation performance using code multipath errors and their statistical properties and adjusting the circular motion parameters based on the maximum multipath frequency, the minimum fault tolerance frequency, and the actual multipath frequency comprises the steps of:

and judging that the multipath error restraining performance of the circular motion of the antenna exceeds a preset range according to the code multipath error and the statistical characteristics thereof, and re-calculating the code multipath error and the statistical characteristics thereof after adjusting the circular motion parameters according to the maximum multipath frequency, the minimum fault-tolerant frequency and the actual multipath frequency until the code multipath error and the statistical characteristics thereof are utilized to judge that the multipath error restraining performance of the circular motion of the antenna is within the preset range.

5. A multipath error mitigation system utilizing circular motion of an antenna, comprising:

the upper limit module is used for constructing an antenna circular motion model and obtaining the maximum multipath frequency;

the lower limit module is used for obtaining the minimum fault-tolerant multipath frequency according to the single reflection model;

the circular motion parameter module is used for obtaining preset circular motion parameters according to the maximum multipath frequency and the minimum fault tolerance multipath frequency;

the multipath frequency extraction module is used for collecting observation data and calculating actual multipath frequency;

the multipath performance evaluation module is used for evaluating multipath inhibition performance by adopting code multipath error and statistical characteristics thereof and adjusting circular motion parameters according to the maximum multipath frequency, the minimum fault-tolerant frequency and the actual multipath frequency;

the step of constructing the antenna circular motion model and obtaining the maximum multipath frequency specifically comprises the following steps:

constructing an antenna circular motion model according to a multipath delay mathematical model of a user receiver and obtaining preset circular motion parameters;

obtaining the maximum multipath frequency according to the preset circular motion parameters;

the expression of the maximum multipath frequency is specifically:

in the above formula, r represents the radius of circular motion, ω represents the angular velocity of the circular motion of the object, and λ is the wavelength of the satellite signal;

the step of obtaining the minimum fault-tolerant multipath frequency of the user according to the single reflection model specifically comprises the following steps:

obtaining an acceptable maximum multipath error according to the user characteristics;

deducing a model of multipath delay and multipath frequency according to the maximum multipath error and through a single reflection model to obtain the minimum fault-tolerant frequency;

the expression of the model of the multipath delay and the multipath frequency is specifically as follows:

in the above-mentioned method, the step of,

delta is the multipath delay at the current time, and lambda is the signalNumber wavelength.

6. A multipath error suppressing apparatus utilizing circular motion of an antenna, comprising:

at least one processor;

at least one memory for storing at least one program;

the at least one program, when executed by the at least one processor, causes the at least one processor to implement a multipath error mitigation method utilizing circular motion of an antenna as recited in any one of claims 1-4.

Images