A method for calibrating the gain difference of a GNSS-R delay mapping receiver channel

Abstract

The application discloses a GNSS-R delay mapping receiver channel gain difference calibration method and relates to the technical field of global navigation satellite system reflected signal measurement. The method comprises the following steps: acquiring a direct waveform sequence and a reflected waveform sequence of a GNSS-R delay mapping receiver; for any visible star, calculating average delay power waveforms of the direct waveform sequence and the reflected waveform sequence respectively; extracting a wave peak and a delay index of the average delay power waveform; calculating average noise power; and calculating a gain difference calibration coefficient of a direct channel and a reflected channel of the GNSS-R delay mapping receiver. The application can realize low-cost and high-precision calibration of the channel gain difference of the GNSS-R delay mapping receiver.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of global navigation satellite system reflectometry, and particularly relates to a GNSS-R delay mapping receiver channel gain difference calibration method. BACKGROUND

[0002] Global Navigation Satellite System Reflectometry (GNSS-R) is a technology that uses GNSS signals reflected by the earth surface to retrieve geophysical parameters, and has great application potential in remote sensing of geophysical parameters such as sea surface wind field and soil moisture.

[0003] GNSS-R delay mapping receiver is a technical device specially used for processing GNSS reflected signals, and is mainly suitable for geophysical parameter remote sensing applications based on ground and space. The intensity of GNSS signals reflected by the earth surface is weak, and traditional GNSS receivers cannot complete the acquisition and tracking of reflected signals. GNSS-R delay mapping receiver has a direct signal processing channel (direct channel) and a reflected signal processing channel (reflected channel), and realizes continuous and effective processing of GNSS reflected signals in a way that direct signal closed-loop synchronization assists reflected signal open-loop synchronization, and outputs delay power waveforms of direct signals and reflected signals as basic observation quantities for geophysical parameter remote sensing. In GNSS-R power measurement applications such as soil moisture retrieval and sea ice detection, the peak value ratio of reflected signal and direct signal delay power waveforms is usually used as the medium reflectivity to retrieve geophysical parameters. However, the gain effect of the direct signal processing channel and the reflected signal processing channel of the GNSS-R delay receiver on the signal has certain difference, which will cause the estimation deviation of the reflectivity, and finally cause the retrieval error of the geophysical parameters, and needs to be calibrated.

[0004] Currently, the channel gain difference calibration methods of GNSS-R delay mapping receiver mainly include water surface calibration method and channel switching method. The water surface calibration method takes the water reflectivity obtained by the GNSS-R delay mapping receiver in the calm water surface scene as a reference, and takes the ratio of the medium reflectivity obtained by the GNSS-R delay mapping receiver in the scene to be measured to the reference as the calibrated reflectivity. The method is simple in operation and low in cost, but it is too dependent on the condition of calm water surface, and is easily affected by the water surface condition and multipath environment in actual application, and the calibration accuracy is difficult to guarantee. The channel switching method assumes that the direct signal and the reflected signal strength remain unchanged in a short time, and realizes the timing exchange of the direct channel and the reflected channel by adding a channel switching device to the GNSS-R delay mapping receiver, and takes the square root of the product of the reflectivity calculated before and after the channel exchange as the calibrated reflectivity. The channel switching method has high calibration accuracy, but needs to add a radio frequency channel switching device to the GNSS-R delay mapping receiver, which will increase the complexity, volume, weight and development cost of the GNSS-R delay mapping receiver.

[0005] Therefore, there is a need for a new GNSS-R delay mapping receiver channel gain difference calibration method to realize low-cost and high-precision GNSS-R delay mapping receiver channel gain difference calibration. SUMMARY

[0006] Based on this, the embodiment of the present application provides a GNSS-R delay mapping receiver channel gain difference calibration method, which realizes low-cost and high-precision calibration of the channel gain difference of the GNSS-R delay mapping receiver by using a standard dual-channel GNSS signal simulator.

[0007] To achieve the above object, the present application provides the following scheme:

[0008] A GNSS-R delay mapping receiver channel gain difference calibration method, comprising:

[0009] Obtaining direct wave form sequences and reflected wave form sequences; the direct wave form sequences are signal delay power wave form sequences of each visible star tracked by a direct channel of a GNSS-R delay mapping receiver; the reflected wave form sequences are signal delay power wave form sequences of each visible star tracked by a reflected channel of the GNSS-R delay mapping receiver; a direct signal input port of the GNSS-R delay mapping receiver is connected with a first signal output port of a GNSS simulator through a first radio frequency connection line; a reflected signal input port of the GNSS-R delay mapping receiver is connected with a second signal output port of the GNSS simulator through a second radio frequency connection line; signal output powers of the first signal output port and the second signal output port are the same; the signal delay power wave form sequences comprise M groups of delay power wave forms; each group of the delay power wave forms comprises N delay power sample points; M and N are both integers greater than zero;

[0010] For any visible star, an average delay power wave form of the direct wave form sequences is calculated to obtain a first average wave form, and an average delay power wave form of the reflected wave form sequences is calculated to obtain a second average wave form;

[0011] For any visible star, peak detection and peak extraction are performed on the first average wave form to obtain a first peak and a first delay index, and peak detection and peak extraction are performed on the second average wave form to obtain a second peak and a second delay index; the first delay index is a delay index of a delay power sample point where the first peak is located; the second delay index is a delay index of a delay power sample point where the second peak is located;

[0012] For any visible star, a first noise power is calculated according to the first average wave form and the first delay index, and a second noise power is calculated according to the second average wave form and the second delay index; the first noise power is an average noise power of the direct wave form sequences; the second noise power is an average noise power of the reflected wave form sequences;

[0013] For any visible star, a power ratio value is calculated according to the first peak, the second peak, the first noise power and the second noise power; the power ratio value is a ratio of a signal power of a visible star output by a direct channel to a signal power of the visible star output by a reflected channel;

[0014] According to power ratio values of all visible stars, an insertion loss of the first radio frequency connection line and an insertion loss of the second radio frequency connection line, a gain difference calibration coefficient of a direct channel and a reflected channel of the GNSS-R delay mapping receiver is calculated; the gain difference calibration coefficient is used for compensating and calibrating a channel gain difference of the GNSS-R delay mapping receiver.

[0015] Optionally, the signal output power of the first signal output port and the second signal output port satisfies a power setting principle.

[0016] The power setting principle comprises: the signal output power is not lower than the direct signal capture sensitivity of the GNSS-R delay mapping receiver and the signal output power is not higher than 1 / 10 of the noise power of the GNSS-R delay mapping receiver in a test environment.

[0017] Optionally, the expression of the direct waveform sequence and the reflected waveform sequence is:

[0018]

[0019] wherein, is the direct waveform sequence of the kth visible star; is the reflected waveform sequence of the kth visible star; is the first group of delay power waveforms in is the first group of delay power waveforms in is the second group of delay power waveforms in is the second group of delay power waveforms in is the mth group of delay power waveforms in is the mth group of delay power waveforms in is the Mth group of delay power waveforms in is the Mth group of delay power waveforms in

[0020] Optionally, the expression of the first average waveform and the second average waveform is:

[0021]

[0022] wherein, is the first average waveform of the kth visible star; is the second average waveform of the kth visible star; is the mth group of delay power waveforms in is the mth group of delay power waveforms in is the direct waveform sequence of the kth visible star; is the reflected waveform sequence of the kth visible star.

[0023] ​​​​​​​​​​Optionally, the expression of the first noise power and the second noise power is:

[0024]

[0025] wherein, is the first noise power of the kth visible star; is the second noise power of the kth visible star; is the first delay index of the kth visible star; is the second delay index of the kth visible star; s is the number of delay power samples on a unit pseudo-code chip; [1.5s] is the integer part of the product of 1.5 and s; is the first average waveform of the kth visible star; is the delay power sample with the delay index n in the first average waveform; is the second average waveform of the kth visible star; is the delay power sample with the delay index n in the second average waveform; is the first average waveform of the kth visible star; is the second average waveform of the kth visible star.

[0026] Optionally, the calculation formula of the power ratio is:

[0027]

[0028] wherein, F (k) is the power ratio of the kth visible star; is the first delay index of the kth visible star; is the second delay index of the kth visible star; is the value of the first peak of the kth visible star; is the value of the second peak of the kth visible star; is the first noise power of the kth visible star; is the second noise power of the kth visible star.

[0029] Optionally, the calculation formula of the gain difference calibration coefficient is:

[0030]

[0031] wherein, F0 is the gain difference calibration coefficient; F (k) is the power ratio of the kth visible star; K represents the total number of visible stars; L1 is the insertion loss of the first radio frequency connecting line; L2 is the insertion loss of the second radio frequency connecting line.

[0032] According to the specific embodiments of the present application, the following technical effects are provided:

[0033] The embodiment of the present application provides a GNSS-R delay mapping receiver channel gain difference calibration method, obtains direct wave sequence and reflected wave sequence of the GNSS-R delay mapping receiver; for any visible star, average delay power waveforms of the direct wave sequence and the reflected wave sequence are calculated respectively; the wave peak and the delay index of the average delay power waveform are extracted; the average noise power is calculated; and the gain difference calibration coefficient of the direct channel and the reflected channel of the GNSS-R delay mapping receiver is calculated. The present application does not need to implement additional field test experiments, can avoid the influence of test environment factors on the channel gain difference calibration precision of the GNSS-R delay mapping receiver, does not need to additionally install a channel switching device for the GNSS-R delay mapping receiver, and can reduce the complexity, volume, weight and manufacturing cost of the GNSS-R delay mapping receiver, so that the present application can realize low-cost and high-precision calibration of the channel gain difference of the GNSS-R delay mapping receiver. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 The flow chart of the GNSS-R delay mapping receiver channel gain difference calibration method provided by the embodiment of the present application is shown in the figure.

[0036] Figure 2 The device connection schematic diagram provided by the present application is shown in the figure.

[0037] Figure 3 The Beidou B1I signal acquisition result schematic diagram is shown in the figure.

[0038] Figure 4 The direct channel Beidou PRN04 star B1I signal delay power waveform sequence schematic diagram is shown in the figure.

[0039] Figure 5 The reflected channel Beidou PRN04 star B1I signal delay power waveform sequence schematic diagram is shown in the figure.

[0040] Figure 6 The Beidou PRN04 star B1I signal average delay power waveform schematic diagram is shown in the figure.

[0041] Figure 7 The B1I signal average delay power waveform peak value schematic diagram of each visible star is shown in the figure.

[0042] Figure 8Fig. 1 is a schematic diagram of delay index of peak value of average delay power waveform of B1I signal of each visible star;

[0043] Figure 9 Fig. 4 is a schematic diagram of average noise power of delay power waveform sequence of B1I signal of each visible star;

[0044] Figure 10 Fig. 5 is a schematic diagram of power ratio of direct channel and reflection channel and calibration coefficient result of each visible star. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0046] The present application aims to provide a GNSS-R delay mapping receiver channel gain difference calibration method, which realizes low-cost and high-precision calibration of GNSS-R delay mapping receiver channel gain difference by using a standard double-channel GNSS signal simulator.

[0047] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0048] Reference Figure 1 The GNSS-R delay mapping receiver channel gain difference calibration method of the present embodiment comprises:

[0049] Step 101: Obtain direct waveform sequence and reflection waveform sequence.

[0050] The direct waveform sequence is a signal delay power waveform sequence of each visible star tracked by a direct channel of a GNSS-R delay mapping receiver; the reflection waveform sequence is a signal delay power waveform sequence of each visible star tracked by a reflection channel of the GNSS-R delay mapping receiver.

[0051] The signal delay power waveform sequence comprises M groups of delay power waveforms; each group of delay power waveforms comprises N delay power sample points; M and N are both integers greater than zero.

[0052] The direct signal input port of the GNSS-R delay mapping receiver is connected with the first signal output port of the GNSS simulator through a first radio frequency connecting line; the reflected signal input port of the GNSS-R delay mapping receiver is connected with the second signal output port of the GNSS simulator through a second radio frequency connecting line; the signal output power of the first signal output port and the second signal output port is the same.

[0053] In practical application, the implementation process of step 101 is as follows:

[0054] 1. Connecting the dual-channel GNSS signal simulator and the GNSS-R delay mapping receiver

[0055] Referring to Figure 2 , the first signal output port (signal output port 1) and the first signal output port (signal output port 2) of the GNSS simulator are connected to the direct signal input port and the reflected signal input port of the GNSS-R receiver respectively by using the first radio frequency connecting line (i.e. radio frequency connecting line 1) and the second radio frequency connecting line (i.e. radio frequency connecting line 2) with known insertion loss. The insertion loss of the first radio frequency connecting line and the second radio frequency connecting line is L1 and L2 respectively.

[0056] 2. Starting, configuring and running the dual-channel GNSS signal simulator

[0057] The power supply is turned on, the dual-channel GNSS signal simulator is started, the signal to be calibrated is selected, the same ephemeris file, signal simulation starting time, receiver spatial coordinates and signal output power are configured for the two signal output channels, and the running is performed until the signal output power is stable, and the signal output power of the first signal output port and the second signal output port is the same. Among them, the signal output power meets the power setting principle, and the power setting principle is: (1) the signal output power is not lower than the direct signal acquisition sensitivity of the GNSS-R delay mapping receiver; (2) the signal output power is not higher than 1 / 10 of the noise power of the GNSS-R delay mapping receiver in the test environment. That is:

[0058]

[0059] Among them, P is the set signal output power value of the dual-channel GNSS signal simulator, P0 is the direct signal acquisition sensitivity of the GNSS-R delay mapping receiver, is the noise power of the GNSS-R delay mapping receiver in the test environment.

[0060] 3. Running the GNSS-R delay mapping receiver to obtain two-channel signal delay power waveform sequences, i.e. direct waveform sequence and reflected waveform sequence

[0061] Power on, run GNSS-R delay mapping receiver. Direct channel completes the capture and tracking of the signal, calculates and outputs the signal delay power waveform sequence of each visible star, and obtains the direct waveform sequence; the reflected channel uses the signal parameters of each visible star obtained by the direct channel to perform open-loop tracking on the signal in the reflected channel, calculates and outputs the signal delay power waveform sequence of each satellite, that is, the reflected waveform sequence. The visible star signal parameters include: carrier frequency, carrier phase and pseudo code phase.

[0062] Assume that the number of visible stars tracked by the GNSS-R delay mapping receiver is K, and the signal delay power waveform sequence output includes M groups of delay power waveforms, and the number of delay power samples in each group of delay power waveforms is N. The signal delay power waveform sequence (direct waveform sequence and reflected waveform sequence) of the kth visible star (1≤k≤K) output by the direct channel and the reflected channel is respectively denoted as and

[0063] wherein, is the direct waveform sequence of the kth visible star; is the reflected waveform sequence of the kth visible star; is the 1st group of delay power waveforms in is the 1st group of delay power waveforms in is the 2nd group of delay power waveforms in is the 2nd group of delay power waveforms in is the mth group of delay power waveforms in is the mth group of delay power waveforms in is the Mth group of delay power waveforms in is the Mth group of delay power waveforms in is the 1st delay power sample in the waveform is the 1st delay power sample in the waveform is the 2nd delay power sample in the waveform is the 2nd delay power sample in the waveform is the mth delay power sample in the waveform is the mth delay power sample in the waveform is the Mth delay power sample in the waveform is the Mth delay power sample in the waveform.

[0064]

[0065] wherein, is the 1st delay power sample in the waveform is the 1st delay power sample in the waveform is the 2nd delay power sample in the waveform is the 2nd delay power sample in the waveform is the mth delay power sample in the waveform is the mth delay power sample in the waveform is the Mth delay power sample in the waveform is the Mth delay power sample in the waveform is the waveform is the delayed power sample with delay index n in is the waveform is the delayed power sample with delay index n in is the waveform is the delayed power sample with delay index N in is the waveform is the delayed power sample with delay index N in ; T denotes transpose.

[0066] Step 102: for any visible star, calculate the average delay power waveform of the direct waveform sequence to obtain a first average waveform, and calculate the average delay power waveform of the reflected waveform sequence to obtain a second average waveform.

[0067] Specifically, this step calculates the average delay power waveforms of each visible star signal in the two channels, i.e., the first average waveform and the second average waveform:

[0068]

[0069] wherein, is the first average waveform of the kth visible star; is the second average waveform of the kth visible star; is the mth group of delay power waveforms in is the mth group of delay power waveforms in is the direct waveform sequence of the kth visible star; is the reflected waveform sequence of the kth visible star. is the delayed power sample with delay index n in

[0070] is the delayed power sample with delay index n in is the delayed power sample with delay index n in is the delayed power sample with delay index n in is the delayed power sample with delay index n in is the delayed power sample with delay index n in, and the specific calculation formula is:

[0071]

[0072] Step 103: for any visible star, perform peak detection and peak extraction on the first average waveform to obtain a first peak and a first delay index, and perform peak detection and peak extraction on the second average waveform to obtain a second peak and a second delay index.

[0073] The first delay index is the delay index of the delay power sample where the first peak is located; and the second delay index is the delay index of the delay power sample where the second peak is located.

[0074] Specifically, this step extracts the peak value (first peak and second peak) and its delay index (first delay index and second delay index) of the average delay power waveform of each visible star signal of the two channels:

[0075] The peak value detection and extraction are sequentially performed on the average delay power waveform of each visible star signal of the two channels obtained in step 103. The delay index (i.e., the first delay index) at which the peak value of the average delay power waveform of each visible star signal of the direct channel is recorded as The corresponding peak value (the value of the first peak) is The delay index (the second delay index) at which the peak value of the average delay power waveform of each visible star signal of the reflected channel is recorded as The corresponding peak value (the value of the second peak) is

[0076] Step 104: For any visible star, the first noise power is calculated according to the first average waveform and the first delay index, and the second noise power is calculated according to the second average waveform and the second delay index.

[0077] The first noise power is the average noise power of the direct waveform sequence; and the second noise power is the average noise power of the reflected waveform sequence.

[0078] Specifically, this step calculates the average noise power of the delay power waveform sequence of each visible star signal of the two channels, i.e., the first noise power and the second noise power:

[0079]

[0080] wherein, is the first noise power of the kth visible star; is the second noise power of the kth visible star; is the first delay index of the kth visible star; is the second delay index of the kth visible star; s is the number of delay power samples per unit pseudo-code chip; and [1.5s] is the integer part of the product of 1.5 and s; is is the delay power sample with the delay index n in the first average waveform; is is the delay power sample with the delay index n in the second average waveform.

[0081] Step 105: For any visible star, the power ratio value is calculated according to the first peak, the second peak, the first noise power and the second noise power.

[0082] The power ratio value is the ratio of the signal power of the visible star output by the direct channel to the signal power of the visible star output by the reflected channel.

[0083] Specifically, the power ratio is calculated by the following formula:

[0084]

[0085] wherein F (k) is the power ratio of the kth visible star; is the first delay index of the kth visible star; is the second delay index of the kth visible star; is the value of the first peak of the kth visible star; is the value of the second peak of the kth visible star; is the first noise power of the kth visible star; is the second noise power of the kth visible star.

[0086] Step 106: According to the power ratios of all visible stars, the insertion loss of the first radio frequency connecting line and the insertion loss of the second radio frequency connecting line, the gain difference calibration coefficient of the direct channel and the reflected channel of the GNSS-R delay mapping receiver is calculated.

[0087] The gain difference calibration coefficient is used to compensate and calibrate the channel gain difference of the GNSS-R delay mapping receiver.

[0088] Specifically, the gain difference calibration coefficient is calculated by the following formula:

[0089]

[0090] wherein F0 is the gain difference calibration coefficient; F (k) is the power ratio of the kth visible star; K represents the total number of visible stars; L1 is the insertion loss of the first radio frequency connecting line; and L2 is the insertion loss of the second radio frequency connecting line.

[0091] Through the above steps, the accurate measurement of the gain difference calibration coefficient of the GNSS-R delay mapping receiver channel is realized, which can be directly used for the compensation and calibration of the gain difference of the GNSS-R delay mapping receiver channel in actual application.

[0092] The GNSS-R delay mapping receiver channel gain difference calibration method of the embodiment does not need to implement additional field test experiments, can avoid the influence of test environment factors on the calibration accuracy of the GNSS-R delay mapping receiver channel gain difference, and does not need to additionally install a channel switching device for the GNSS-R delay mapping receiver, which can reduce the complexity, volume, weight and manufacturing cost of the GNSS-R delay mapping receiver.

[0093] For further illustration, below takes an example of calibrating the channel gain difference of a GNSS-R delay mapping receiver working at Beidou B1I frequency point by using a certain standard dual-channel GNSS signal simulator, and the calibration process specifically includes the following steps:

[0094] Step 1: connecting the dual-channel GNSS signal simulator and the GNSS-R delay mapping receiver

[0095] Still referring to Figure 2 , the GNSS simulator signal output port 1 and output port 2 are connected to the GNSS-R receiver direct signal input port and reflected signal input port respectively by using equal-length and same-type radio frequency connecting line 1 and radio frequency connecting line 2. The insertion loss of the two radio frequency connecting lines is equal, i.e. L1=L2.

[0096] Step 2: starting, configuring and running the dual-channel GNSS signal simulator

[0097] Turn on the power supply, start the dual-channel GNSS signal simulator, select the signal to be calibrated, and configure the same ephemeris file, signal simulation starting time, receiver spatial coordinates and signal output power for the two signal output channels. Among them, the signal output power setting principle is: (1) not less than the GNSS-R delay mapping receiver direct signal acquisition sensitivity; (2) not higher than 1 / 10 of the GNSS-R delay mapping receiver noise power in the test environment. That is:

[0098]

[0099] Among them, P is the set dual-channel GNSS signal simulator output signal power value, P0 is the GNSS-R delay mapping receiver direct signal acquisition sensitivity, is the GNSS-R delay mapping receiver noise power in the test environment. Here, the acquisition sensitivity of the GNSS-R delay mapping receiver to be calibrated for Beidou B1I signal is about -160dBW, and the receiver noise power in room temperature environment is about -140dBW. According to the above signal output power setting principle, the signal output power of the two channels is set to -150dBW. After the configuration is completed, the dual-channel GNSS signal simulator is run until the output signal power is stable.

[0100] Step 3: running the GNSS-R delay mapping receiver, and acquiring two-channel signal delay power waveform sequences

[0101] Power on, run GNSS-R delay mapping receiver. Direct channel completes the capture and tracking of signals, calculates and outputs the delay power waveform sequence of each visible star signal; the reflected channel uses the parameters of each visible star signal obtained by the direct channel to perform open-loop tracking on the signals in the reflected channel, and calculates and outputs the delay power waveform sequence of each satellite signal. The direct channel captures B1I signals from 15 Beidou satellites, and tracks B1I signals of 6 Beidou satellites, namely PRN02, PRN04, PRN05, PRN18, PRN24 and PRN26. Figure 3 The capture results of the direct channel for Beidou B1I signals are shown, Figure 4 and Figure 5 The delay power waveform sequence of Beidou PRN04 star B1I signal with a length of 30s output by the direct channel and the reflected channel is shown, and each delay power waveform has 30000 groups, and each group of delay power waveform has 64 delay power waveform points.

[0102] Step 4: Calculate the average delay power waveform of each visible star signal of the two channels

[0103] According to the following formula, the average delay power waveforms (first average waveform and second average waveform) of each visible star signal output by the direct channel and the reflected channel are calculated in turn:

[0104]

[0105] Among them,

[0106]

[0107] Figure 6 The average delay power waveforms of each visible star signal of the direct channel and the reflected channel are shown.

[0108] Step 5: Extract the peak value of the average delay power waveform of each visible star signal of the two channels and its delay index

[0109] The peak value detection and extraction are performed in turn for the average delay power waveforms of each visible star signal of the two channels obtained in step 4. The delay index where the peak value of the average delay power waveform of each visible star signal of the direct channel is recorded as The corresponding peak value is The delay index where the peak value of the average delay power waveform of each visible star signal of the reflected channel is recorded as The corresponding peak value is Figure 7 and Figure 8 The peak value of the average delay power waveform of each visible star signal tracked by the two channels and its delay index are shown. The delay index of the peak value of the average delay power waveform of all visible star signals of the two channels is 33.

[0110] Step 6: Calculate the average noise power of each visible star signal delay power waveform sequence of the two channels (first noise power and second noise power).

[0111] Using the average delay power waveform of each visible star signal of the two channels obtained in step 4 and the delay index of the peak value of the average delay power waveform obtained in step 5, the average noise power of each visible star signal delay power waveform sequence output by the direct channel and the reflected channel is calculated in turn according to the following formula.

[0112]

[0113] In the formula, s is the number of delay samples on a single pseudo-code chip. Here, s = 8.

[0114] Figure 9 The average noise power of each visible star signal delay power waveform sequence of the two channels is given.

[0115] Step 7: Calculate the channel gain difference calibration coefficient of the GNSS-R delay mapping receiver

[0116] Using the peak value of each satellite average delay power waveform obtained in step 5 and the average noise power of each satellite delay power waveform sequence obtained in step 6, the power ratio of each visible star signal output by the direct channel and the reflected channel is calculated in turn according to the following formula:

[0117]

[0118] Further, using the radio frequency connection line insertion loss mentioned in step 1 and the power ratio of each visible star signal output by the direct channel and the reflected channel, the gain difference calibration coefficient of the direct channel and the reflected channel is calculated according to the following formula:

[0119]

[0120] Figure 10 For the power ratio of each visible star signal and the calibration coefficient, the channel gain difference calibration coefficient of the GNSS-R delay mapping receiver is finally determined to be 0.87.

[0121] The GNSS-R delay mapping receiver channel gain difference calibration method provided by the embodiment of the application uses a standard double-channel GNSS signal simulator to provide a test signal, and uses the signal delay power waveform sequences output by the direct channel and the reflection channel of the GNSS-R delay mapping receiver to calculate the two-channel gain difference calibration coefficients, specifically: connecting the double-channel GNSS signal simulator with the GNSS-R delay mapping receiver; starting, configuring and running the double-channel GNSS signal simulator (configuring the double-channel GNSS simulator to output two identical signals); running the GNSS-R delay mapping receiver to obtain two-channel signal delay power waveform sequences; calculating the average delay power waveform of each visible star signal of the two channels; extracting the peak value of the average delay power waveform of each visible star signal of the two channels and the delay index thereof; calculating the average noise power of the delay power waveform sequences of each visible star signal of the two channels; and calculating the GNSS-R delay mapping receiver channel gain difference calibration coefficients (first calculating the ratio of the power of the two signals for each visible star, then calculating the statistical mean of the power ratios of all visible stars, then performing radio frequency connection line insertion loss compensation, and finally obtaining the channel gain difference calibration coefficients). The method realizes low-cost and high-precision calibration of the channel gain difference of the GNSS-R delay mapping receiver.

[0122] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the system disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0123] The principles and implementation manners of the application are described by using specific examples in the present application, and the above embodiment description is only used to help understand the method of the application and its core idea; meanwhile, for those skilled in the art, according to the idea of the application, the specific implementation manner and application range will be changed. In conclusion, the content of the specification should not be understood as a limitation of the application.

Claims

1. A method of GNSS-R delay mapping receiver channel gain difference calibration, characterized in that, The method comprises the following steps: obtaining a direct waveform sequence and a reflected waveform sequence; the direct waveform sequence is a signal delay power waveform sequence of each visible star tracked by a direct channel of a GNSS-R delay mapping receiver; the reflected waveform sequence is a signal delay power waveform sequence of each visible star tracked by a reflected channel of the GNSS-R delay mapping receiver; a direct signal input port of the GNSS-R delay mapping receiver is connected with a first signal output port of a GNSS simulator through a first radio frequency connection line; a reflected signal input port of the GNSS-R delay mapping receiver is connected with a second signal output port of the GNSS simulator through a second radio frequency connection line; the signal output power of the first signal output port and the second signal output port is the same; the signal delay power waveform sequence comprises M groups of delay power waveforms; each group of delay power waveforms comprises N delay power sample points; M and N are both integers greater than zero; for any visible star, an average delay power waveform of the direct waveform sequence is calculated to obtain a first average waveform, and an average delay power waveform of the reflected waveform sequence is calculated to obtain a second average waveform; for any visible star, peak detection and peak extraction are performed on the first average waveform to obtain a first peak and a first delay index, and peak detection and peak extraction are performed on the second average waveform to obtain a second peak and a second delay index; the first delay index is the delay index of the delay power sample point where the first peak is located; the second delay index is the delay index of the delay power sample point where the second peak is located; for any visible star, a first noise power is calculated according to the first average waveform and the first delay index, and a second noise power is calculated according to the second average waveform and the second delay index; the first noise power is the average noise power of the direct waveform sequence; the second noise power is the average noise power of the reflected waveform sequence; for any visible star, a power ratio is calculated according to the first peak, the second peak, the first noise power and the second noise power; the power ratio is the ratio of the signal power of the visible star output by the direct channel to the signal power of the visible star output by the reflected channel; a gain difference calibration coefficient of the direct channel and the reflected channel of the GNSS-R delay mapping receiver is calculated according to the power ratio of all visible stars, the insertion loss of the first radio frequency connection line and the insertion loss of the second radio frequency connection line; the gain difference calibration coefficient is used for compensating and calibrating the channel gain difference of the GNSS-R delay mapping receiver.

2. The method of claim 1, wherein the method further comprises: the signal output power of the first signal output port and the second signal output port satisfies a power setting principle; the power setting principle comprises that the signal output power is not lower than the direct signal acquisition sensitivity of the GNSS-R delay mapping receiver and the signal output power is not higher than 1 / 10 of the noise power of the GNSS-R delay mapping receiver in a test environment.

3. The method of claim 1, wherein the method further comprises: the expression of the direct waveform sequence and the reflected waveform sequence is wherein, is the direct waveform sequence for the kth visible star; is the reflected waveform sequence for the kth visible star; is the first group of delayed power waveforms in is the first group of delayed power waveforms in is the first group of delayed power waveforms in is the first group of delayed power waveforms in is the second group of delayed power waveforms in is the second group of delayed power waveforms in is the second group of delayed power waveforms in is the second group of delayed power waveforms in is the mth group of delayed power waveforms in is the mth group of delayed power waveforms in is the mth group of delayed power waveforms in is the mth group of delayed power waveforms in is the Mth group of delayed power waveforms in is the Mth group of delayed power waveforms in is the Mth group of delayed power waveforms in is the Mth group of delayed power waveforms in 4. The method of claim 1, wherein the method further comprises: Expressions of the first average waveform and the second average waveform are: wherein, is the first average waveform of the kth visible star; is the second average waveform of the kth visible star; is the mth group of delayed power waveforms in is the mth group of delayed power waveforms in is the mth group of delayed power waveforms in is the mth group of delayed power waveforms in is the direct waveform sequence of the kth visible star; is the reflected waveform sequence of the kth visible star.

5. The method of claim 1, wherein, Expressions of the first noise power and the second noise power are: wherein is a first noise power for the kth visible star; is a second noise power for the kth visible star; is a first delay index for the kth visible star; is a second delay index for the kth visible star; s is a number of delay power samples on a unit pseudo-code chip; [1.5s] is an integer part of a product of 1.5 and s; is a first average waveform for the kth visible star; is a delay power sample with delay index n in the first average waveform for the kth visible star; is a second average waveform for the kth visible star; is a delay power sample with delay index n in the second average waveform for the kth visible star; is a first average waveform for the kth visible star; is a second average waveform for the kth visible star.

6. The method of claim 1, wherein: The calculation formula of the power ratio is: wherein F (k) is the power ratio of the kth visible star; is the first delay index of the kth visible star; is the second delay index of the kth visible star; is the value of the first peak of the kth visible star; is the value of the second peak of the kth visible star; is the first noise power of the kth visible star; is the second noise power of the kth visible star.

7. The method of claim 1, wherein the method further comprises: The calculation formula of the gain difference calibration coefficient is: The calculation formula of the gain difference calibration coefficient is: Wherein, F0 is the gain difference calibration coefficient; F (k) is the power ratio of the kth visible star; K represents the total number of visible stars; L1 is the insertion loss of the first radio frequency connecting line; L2 is the insertion loss of the second radio frequency connecting line.

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