CN110673176A - Novel method for carrier multipath inversion of GNSS receiver - Google Patents

Novel method for carrier multipath inversion of GNSS receiver Download PDF

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CN110673176A
CN110673176A CN201911041614.3A CN201911041614A CN110673176A CN 110673176 A CN110673176 A CN 110673176A CN 201911041614 A CN201911041614 A CN 201911041614A CN 110673176 A CN110673176 A CN 110673176A
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signal
carrier
multipath
direct
equation
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张鹏
吴亮亮
郜建峰
李春雨
蔡欣欣
李彩萌
孟庆伟
陈林
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SHANGHAI SHUANGWEI NAVIGATION TECHNOLOGY CO.,LTD.
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Shanghai Huace Navigation Technology Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)

Abstract

The invention discloses a novel carrier multipath inversion method of a GNSS receiver, which obtains the relation among a direct signal, a reflected signal and a combined signal through carrier multipath and calculates the relation between the carrier multipath and the signal quality so as to obtain the carrier multipath inversion method. The method can estimate and correct the multipath error of the carrier phase of each epoch in real time, does not need star day filtering or an inter-epoch difference algorithm, can utilize more effective observed values, and provides powerful guarantee for GNSS data processing.

Description

Novel method for carrier multipath inversion of GNSS receiver
Technical Field
The invention relates to the field of GNSS receivers, in particular to a novel method for multi-path inversion of carrier waves of a GNSS receiver.
Background
In GNSS precision positioning, carrier multipath is one of the most important error sources affecting positioning accuracy. Taking L1 and L2 of GPS as examples, the maximum generated carrier phase error can reach 4.8 and 6.1 centimeters. The carrier multipath has a direct relation with the environment of the observation station, and in the GNSS measurement, most of the carrier multipath errors are usually eliminated through star-day filtering or difference between epochs, or the carrier multipath values are back-calculated through precise coordinates of known points. However, in some other GNSS applications, the precise coordinates of a known point cannot be obtained in advance, for example, the CORS site selection, and how to estimate the carrier multipath value becomes a difficult problem.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a novel method for carrier multipath inversion of a GNSS receiver, namely, carrier multipath is fit-inverted according to a signal-to-noise ratio observed value of a continuous period of time; test results show that the method can accurately obtain the carrier multipath value of the environment where the observation station is located.
In order to achieve the purpose, the invention provides the following technical scheme: a novel carrier multipath inversion method of a GNSS receiver is disclosed, which obtains the relation among a direct signal, a reflected signal and a combined signal through carrier multipath, and calculates the relation between the carrier multipath and the signal quality so as to obtain the carrier multipath inversion method.
Carrier multipath: the receiver receives a satellite signal which has a direct signal and a reflected signal; the reflected signal will be superimposed on the direct signal, and the received combined signal will generate a phase shift; the direct signal, reflected signal and combined signal expressions can be seen in the following formulas;
SD＝AD·cos(φD) (1)
SR＝α·AD·cos(φD+ΔφR) (2)
SC＝SD+SR＝AD·cos(φD)+α·AD·cos(φD+ΔφR) (3)
ADrepresenting the amplitude of the carrier wave, phiDRepresenting the phase of the direct signal, the carrier amplitude of the reflected signal is reduced compared to the direct signal, represented by a scale factor α (0 ≦ α ≦ 1); sDRepresenting a direct signal, SRRepresenting the reflected signal, SCRepresenting a combined signal; carrier amplitude a of the combined signalCAnd the phase error is expressed as:
Figure BDA0002252991490000021
Figure BDA0002252991490000022
signal quality: the signal quality of the GNSS receiver is measured by carrier-to-noise ratio, that is, the intensity of the GNSS signal which is not demodulated and received by the antenna of the receiver is divided by the intensity of the noise; the signal intensity after demodulation filtering processing is very close to CANTThe following equation is found:
Figure BDA0002252991490000023
since the signal strength S is several orders of magnitude greater than the noise N, S is measuredQThe unit is converted into decibel:
SQ(dB)＝10·log10(SQ) (7)
meanwhile, the system noise N is expressed as a noise spectral density N0And loop bandwidth BLProduct of (a):
N＝N0·BL(8)
the signal quality can be normalized by equation (7-8):
SQ0(dBHz)＝10·log10(SQ)(dB)+BL(dBHz) (9), wherein CANT/NANTRepresenting the carrier-to-noise ratio; the signal strength is denoted by S.
Carrier multipath and signal quality relationship:
wherein the scale factor alpha and the phase offset phi of the reflected signalRIs a variable that affects the signal quality due toROver time, the signal quality may fluctuate.
The carrier multipath inversion method comprises the following steps: the carrier multipath inversion algorithm is based on the formula (4), a reflection source is assumed to be the ground, and the scale factor alpha in the formula is regarded as being kept unchanged for a period of time; because the receiver antennas are different, the amplitude value A of the direct signal is obtained by fitting the signal-to-noise ratio parametersDThe fitting method may use a polynomial fit, with the ratio Q of the combined signal amplitude and the direct signal amplitude being expressed as:
Figure BDA0002252991490000031
q and phiRThe differential equation of (a) is as follows:
rearranging equation (5) to merge into equation (12) yields:
Figure BDA0002252991490000033
the simplification can be obtained:
Figure BDA0002252991490000034
so that the multi-path error of the carrier can be formed by Q and phiRThe differential of (a) represents:
from the above equation, we cannot directly calculate the differential between Q and the phase offset of the reflected signal, and assuming that the reflection source of the carrier multipath is only caused by the level ground, the phase offset of the transmitted signal can be represented by the satellite altitude el:
lR＝2hsinel (16)
Figure BDA0002252991490000036
through the formula (16-17), the differential of the phase offset of the reflected signal to the time can be indirectly obtained, and meanwhile, the differential of Q to the time can also be obtained through signal-to-noise ratio calculation;
compared with the prior art, the invention has the following beneficial effects: according to the invention, the precise coordinates of the known point are not required to be obtained in advance, complex algorithms such as precise single-point positioning and the like are not required, namely, the multi-path error of the carrier can be inverted only by the signal-to-noise ratio value of a period of continuous observation time, and the field working cost and time are greatly reduced. The method can estimate and correct the multipath error of the carrier phase of each epoch in real time, does not need star day filtering or an inter-epoch difference algorithm, can utilize more effective observed values, and provides powerful guarantee for GNSS data processing.
Drawings
FIG. 1 is a schematic diagram of the receiver signal reception of the present invention;
FIG. 2 is a vector diagram of the direct signal and combined signal relationship of the present invention;
fig. 3 is a schematic diagram of the relationship between phase offset of the reflected signal and the altitude of the satellite according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "both ends", "one end", "the other end", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," "connected," and the like are to be construed broadly, such as "connected," which may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Referring to fig. 1-3, an example of the present invention is shown: a novel method for carrier multipath inversion of a GNSS receiver comprises the following steps:
carrier multipath:
in practice, the receiver receives the satellite signal and not only the direct signal (S)D) Also present is a reflected signal (S)R) (see FIG. 1). The reflected signal will be superimposed on the direct signal, resulting in a final received combined signal (S)C) A phase offset is generated. The direct signal, reflected signal and combined signal expressions can be seen in equations (1-3).
SD＝AD·cos(φD) (1)
SR＝α·AD·cos(φD+ΔφR) (2)
SC＝SD+SR＝AD·cos(φD)+α·AD·cos(φD+ΔφR) (3)
ADRepresenting the amplitude of the carrier wave, phiDRepresenting the phase of the direct signal, the carrier amplitude of the reflected signal is reduced compared to the direct signal, here represented by a scale factor alpha (0 ≦ alpha ≦ 1). Carrier amplitude a of the combined signalCAnd the phase error can be expressed as:
Figure BDA0002252991490000051
Figure BDA0002252991490000052
signal quality:
GNSS receiver signal quality to carrier-to-noise ratio (C)ANT/NANT) The strength of the GNSS signal received by the receiver antenna without demodulation is divided by the noise strength. The signal intensity (S) after demodulation filtering processing is very close to CANTThe following equation can be considered to hold:
Figure BDA0002252991490000061
since the signal strength S is several orders of magnitude greater than the noise N, S is measuredQUnits are converted to decibels (dB):
SQ(dB)＝10·log10(SQ) (7)
to make each vendor receiver comparability, the signal quality is typically normalized to a specified bandwidth, e.g., 1 Hz. Meanwhile, the system noise N may be expressed as a noise spectral density N0And loop bandwidth BLProduct of (a):
N＝N0·BL(8)
the signal quality can be normalized by equation (7-8):
SQ0(dBHz)＝10·log10(SQ)(dB)+BL(dBHz) (9)
carrier multipath and signal quality relationship:
the relationship between signal quality and carrier multipath is shown in fig. 2 (in fig. 2, it is assumed that the phase offset of the reflected signal is pi/2), and δ Φ represents the phase offset caused by carrier multipath. From the relationship in FIG. 2, one can see:
Figure BDA0002252991490000062
it can be found that equation (10) corresponds to equation (4). Wherein the scale factor alpha and the phase offset phi of the reflected signalRIs a variable that affects the signal quality due toROver time, the signal quality may fluctuate.
The carrier multipath inversion method comprises the following steps:
the carrier multipath inversion algorithm is based on equation (4) and assumes that the source of the reflection is the ground, where the scaling factor α is assumed to remain constant over time. Because the receiver antennas are different, the amplitude value A of the direct signal is obtained by fitting the signal-to-noise ratio parametersDThe fitting method may adopt polynomial fitting, and the estimation method may adopt a least square method, which is not described herein. The ratio Q of the combined signal amplitude and the direct signal amplitude can be expressed as:
Figure BDA0002252991490000063
q and phiRThe differential equation of (a) is as follows:
Figure BDA0002252991490000071
rearranging equation (5) to merge into equation (12) yields:
Figure BDA0002252991490000072
the simplification can be obtained:
Figure BDA0002252991490000073
so that the multi-path error of the carrier can be formed by Q and phiRThe differential of (a) represents:
Figure BDA0002252991490000074
from the above equation we cannot directly calculate the differential of Q and the phase offset of the reflected signal, which is replaced by a simplified method. Assuming that the reflection source at the carrier multipath is only due to level ground, the radiated signal phase offset can be represented by the satellite elevation angle el:
lR＝2hsinel (16)
Figure BDA0002252991490000075
through the equations (16-17), the differential of the phase offset of the reflected signal with respect to time can be indirectly obtained (as shown in fig. 3), and the differential of Q with respect to time can also be obtained through signal-to-noise ratio calculation.
Figure BDA0002252991490000076
The invention can realize that complex algorithms such as precise coordinates of known points and precise single-point positioning are not needed in advance, namely, the multi-path error of the carrier can be inverted only by the signal-to-noise ratio value of a period of continuous observation time, thereby greatly reducing the field working cost and time, and the method is simple and efficient and is not considered by the previous algorithm. The method can estimate and correct the multipath error of the carrier phase of each epoch in real time, does not need star day filtering or an inter-epoch difference algorithm, can utilize more effective observed values, and provides powerful guarantee for GNSS data processing.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Claims (5)

1. A new method for multi-path inversion of carrier waves of a GNSS receiver is characterized in that: and obtaining the relation among the direct signal, the reflected signal and the combined signal through carrier multipath, and calculating the relation between the carrier multipath and the signal quality to obtain the carrier multipath inversion method.
2. The method of claim 1, wherein the carrier multipath is: the receiver receives a satellite signal which has a direct signal and a reflected signal; the reflected signal will be superimposed on the direct signal, and the received combined signal will generate a phase shift; the direct signal, reflected signal and combined signal expressions can be seen in the following formulas;
SD＝AD·cos(φD) (1)
SR＝α·AD·cos(φD+ΔφR) (2)
SC＝SD+SR＝AD·cos(φD)+α·AD·cos(φD+ΔφR) (3)
ADrepresenting the amplitude of the carrier wave, phiDRepresenting the phase of the direct signal, the carrier amplitude of the reflected signal is reduced compared to the direct signal, represented by a scale factor α (0 ≦ α ≦ 1); sDRepresenting a direct signal, SRRepresenting the reflected signal, SCRepresenting a combined signal; carrier amplitude a of the combined signalCAnd the phase error is expressed as:
Figure FDA0002252991480000011
Figure FDA0002252991480000012
3. the method of claim 2, wherein the signal quality is: the signal quality of the GNSS receiver is measured by carrier-to-noise ratio, that is, the intensity of the GNSS signal which is not demodulated and received by the antenna of the receiver is divided by the intensity of the noise; the signal intensity after demodulation filtering processing is very close to CANTThe following equation is found:
Figure FDA0002252991480000013
since the signal strength S is several orders of magnitude greater than the noise N, S is measuredQThe unit is converted into decibel:
SQ(dB)＝10·log10(SQ) (7)
meanwhile, the system noise N is expressed as a noise spectral density N0And loop bandwidth BLProduct of (a):
N＝N0·BL(8)
the signal quality can be normalized by equation (7-8):
Figure FDA0002252991480000021
wherein C isANT/NANTRepresenting the carrier-to-noise ratio; the signal strength is denoted by S.
4. The method of claim 3, wherein the method further comprises: carrier multipath and signal quality relationship:
Figure FDA0002252991480000022
wherein the scale factor alpha and the phase offset phi of the reflected signalRIs a variable that affects the signal quality due toROver time, the signal quality may fluctuate.
5. The method of claim 4, wherein the GNSS receiver comprises a new carrier multipath inversion method, and wherein: the carrier multipath inversion method comprises the following steps: the carrier multipath inversion algorithm is based on the formula (4), a reflection source is assumed to be the ground, and the scale factor alpha in the formula is regarded as being kept unchanged for a period of time; because the receiver antennas are different, the amplitude value A of the direct signal is obtained by fitting the signal-to-noise ratio parametersDThe fitting method may use a polynomial fit, with the ratio Q of the combined signal amplitude and the direct signal amplitude being expressed as:
Figure FDA0002252991480000023
q and phiRThe differential equation of (a) is as follows:
Figure FDA0002252991480000024
rearranging equation (5) to merge into equation (12) yields:
Figure FDA0002252991480000025
the simplification can be obtained:
Figure FDA0002252991480000026
so that the multi-path error of the carrier can be formed by Q and phiRThe differential of (a) represents:
from the above equation, we cannot directly calculate the differential between Q and the phase offset of the reflected signal, and assuming that the reflection source of the carrier multipath is only caused by the level ground, the phase offset of the transmitted signal can be represented by the satellite altitude el:
lR＝2hsinel (16)
through the formula (16-17), the differential of the phase offset of the reflected signal to the time can be indirectly obtained, and meanwhile, the differential of Q to the time can also be obtained through signal-to-noise ratio calculation;
Figure FDA0002252991480000033
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