Preprocessing method adaptive to strength change of pseudo satellite pulse signal and receiver

Abstract

The invention discloses a preprocessing method and a receiver adapted to intensity changes of pseudo satellite pulse signals, and the method comprises the steps: converting a high-bit-width digital intermediate frequency signal outputted by a high-bit-width analog-to-digital conversion chip into a low-bit-width digital intermediate frequency signal adaptive to a capture circuit and a tracking circuit; through a preprocessing circuit, the amplitude of an input signal of a high-bit-width analog-to-digital conversion chip is controlled, and when no pseudo-satellite pulse signal is input, the output power of an amplifier is controlled, so that the amplitude bit of a high-bit-width digital intermediate frequency signal is low 3 bits, and the rest are sign bits; the control parameter is the same as that when no pseudo-satellite pulse signal is input; under the conditions of not changing the data bit width in the existing capture circuit and tracking circuit and not obviously increasing the logic resources of the circuit, the receiver can adapt to satellite navigation signals and pseudo satellite pulse signals with variable strength, and the application range of the navigation receiver is expanded.

Description

Technical Field

[0001] The invention relates to the field of simplified grids, and in particular to a preprocessing method and a receiver adapted to the strength change of pseudo-satellite pulse signals. Background Art

[0002] The Global Navigation Satellite System (GNSS) is a space-based navigation system that broadcasts navigation signals through satellites to provide navigation, positioning and timing services to users on Earth. The current mainstream navigation systems include China's Beidou Navigation Satellite System (BDS), the United States' Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS) and Europe's Galileo system (Galileo). Since the ground level of space-based satellite signals is weak and easily blocked and interfered with, pseudo-satellites, as a navigation enhancement method, are usually deployed on the ground or in low-altitude areas to make up for the vulnerability of space-based satellites and provide navigation enhancement services independently or collaboratively.

[0003] Conventional navigation receiver as attached Figure 1 As shown, it includes an antenna, a radio frequency front-end processing circuit and a baseband signal processing circuit.

[0004] The RF front-end processing circuit receives the RF signal from the antenna, and converts it into an analog intermediate frequency signal through filters, preamplifiers, down-conversion and amplifier processing. The analog intermediate frequency signal is sent to the analog-to-digital converter (ADC) through the automatic gain control (AGC) module, and outputs a digital intermediate frequency signal to the outside. The analog-to-digital converter (ADC) is a general low-bit-width converter, commonly 2 bits (bit) or 4 bits, and outputs a low-bit-width digital intermediate frequency signal to the outside. In order to ensure that the limited bits output by the ADC can represent valid symbol amplitude information, there will be an AGC module before the ADC input to keep the signal entering the ADC constant amplitude. The statistical circuit in the AGC module of a general RF chip is to count energy in a fixed time period. For example, the MAX2769C and MAX2771 chips of Maxim's company have a fixed statistical number in the AGC circuit of 512 analog-to-digital conversion clock cycles.

[0005] To save hardware resources and power consumption, the acquisition circuit and tracking in conventional navigation receivers only process digital intermediate frequency signals of 4 bits or less. Except for the traditional GLONASS satellite signals, which use frequency division multiple access (FDMA), the Beidou satellite signals, GPS satellite signals, Galileo satellite signals and modern GLONASS satellite signals all use code division multiple access (CDMA). Pseudo-satellites are usually deployed on the ground or in low-altitude areas. The use of CDMA will have the problem of near-far effect, that is, the distances between multiple pseudo-satellites and the navigation receiver are different, and the signal strengths of their signals reaching the navigation receiver are quite different. When the distance ratio between the navigation receiver and two pseudo-satellites reaches 10 times, the difference between the signals received by the navigation receiver from the two pseudo-satellites is 60dB. In order to effectively suppress the near-far effect, most of them use pulse signals in a combined manner of code division multiple access (CDMA) and time division multiple access (TDMA). Currently, the pseudo-satellite-related signal systems include RTCM SC-104, RTCA SC-159, and Locata ICD-100E, all of which use CDMA+TDMA, with a pulse broadcast time slot of ≤1 / 10ms.

[0006] Patents CN105487090A and CN105425256A describe that by using blanking technology, the capture circuit and tracking circuit of the navigation receiver are slightly modified to process pseudo-satellite pulse signals. The premise for implementing this method is that the low-bit-width digital intermediate frequency signal sent to the capture circuit and tracking is correct and effective. When the distance ratio between the two pseudo-satellites and the navigation receiver reaches 10 times, the difference in signal strength between their signals reaching the receiver antenna is 60dB. Conventional navigation receivers cannot adapt to rapid changes in strong and weak signals because the AGC module of the RF processing unit counts energy in a fixed time period, resulting in an overflow of the ADC, which in turn causes the navigation receiver to operate abnormally. Summary of the invention

[0007] The present invention aims to solve the technical problem that a conventional navigation receiver cannot adapt to the rapid strength change of a pseudo-satellite pulse signal, resulting in abnormal operation of the receiver. A preprocessing method and a receiver adapted to the strength change of a pseudo-satellite pulse signal are proposed. Without changing the data bit width in the existing capture circuit and tracking circuit and without significantly increasing the circuit logic resources, the navigation receiver can adapt to satellite navigation signals and pseudo-satellite pulse signals with rapid strength change.

[0008] A preprocessing method adapted to the strength change of pseudolite pulse signals comprises the following steps: S1: The high-bitwidth digital intermediate frequency signal is input into the preprocessing circuit, which divides the high-bitwidth digital intermediate frequency signal into two paths, one of which is output to the power statistics and control module, and the other is output to the truncation selection module; S2: The power statistics and control module counts the noise power when there is no pseudo-satellite pulse signal input. The power statistics and control module outputs control parameters to the outside to control the output power of the amplifier so that the amplitude bits of the high-bit width digital intermediate frequency signal are the lower 3 bits, and the rest are sign bits; S3: The truncation selection module converts the high-bit width digital intermediate frequency signal into a 4-bit digital intermediate frequency signal by taking the highest bit of the input as the sign bit and the lowest 3 bits as the amplitude bits. The 4-bit digital intermediate frequency signal is divided into two paths, one of which is output to the selector and the other is output to the absolute value module; S4: The absolute value module converts the 4-bit digital intermediate frequency signal into an unsigned number, first multiplies it with the external input parameter Coef_0, and then compares it with the external input parameter Threshold_0 to obtain the amplitude bit in the 2-bit digital intermediate frequency signal; The value of the amplitude bit is 0 or 1; S5: Combine the sign bit with the amplitude bit in the 2-bit digital intermediate frequency signal, convert the encoding format, and obtain the encoded 2-bit digital intermediate frequency signal, and output the 2-bit digital intermediate frequency signal to the selector; S6: The selector selects a 4-bit digital intermediate frequency signal or a 2-bit digital intermediate frequency signal as a low-bit-width digital intermediate frequency signal to be output externally through an external input parameter Sel, and outputs the low-bit-width digital intermediate frequency signal to the capture circuit and the tracking circuit.

[0009] Furthermore, a preprocessing method is provided to adapt to the change in the strength of pseudolite pulse signals. When there is a pseudolite pulse signal input, the control parameters are the same as when there is no pseudolite pulse signal input.

[0010] Further, a preprocessing method adapted to the strength change of pseudolite pulse signal, the encoding format is: When the sign bit is 0 and the amplitude bit is 0, the effective value is 1; When the sign bit is 0 and the amplitude bit is 1, the effective value is 3; When the sign bit is 1 and the amplitude bit is 0, the effective value is -1; When the sign bit is 1 and the magnitude bit is 1, the effective value is -3.

[0011] A receiver adapted to the strength change of pseudo-satellite pulse signals, comprising an antenna, a radio frequency front-end processing end, a high-bitwidth analog-to-digital conversion chip, and a baseband signal processing end; The baseband signal processing end includes a preprocessing circuit, a capture circuit, a tracking circuit, and a microprocessor; The antenna outputs an RF signal to the input end of the RF front-end processing end, the output end of the RF front-end processing end outputs an analog intermediate frequency signal to the input end of a high-bit-width analog-to-digital conversion chip, the output end of the high-bit-width analog-to-digital conversion chip outputs a high-bit-width digital intermediate frequency signal to the input end of a preprocessing circuit, and the output end of the preprocessing circuit outputs a low-bit-width digital intermediate frequency signal to the input ends of a capture circuit and a tracking circuit, respectively.

[0012] Further, a receiver adapted to the strength variation of pseudolite pulse signals, the RF front-end processing end includes a filter, a preamplifier, a down-conversion and an amplifier; The preprocessing circuit receives external control parameters to control the amplifier gain and controls the amplitude of the output analog intermediate frequency signal.

[0013] Furthermore, in a receiver adapted to changes in the strength of pseudolite pulse signals, the conversion bit number of the high-bit-width analog-to-digital conversion chip is higher than 11 bits.

[0014] Furthermore, in a receiver adapted to changes in the strength of pseudolite pulse signals, the low-bit-width digital intermediate frequency signal is in a 4-bit complement format or a 2-bit Sign Mag mode.

[0015] Furthermore, a receiver that adapts to changes in the strength of pseudo-satellite pulse signals, wherein the capture circuit receives a low-bitwidth digital intermediate frequency signal to capture satellite signals, and when a satellite signal is captured, the code phase and carrier Doppler frequency deviation are sent to a tracking circuit, wherein the tracking circuit receives the low-bitwidth digital intermediate frequency signal, the code phase and carrier Doppler frequency deviation of the capture circuit, tracks the satellite signal, completes control and solution operations on the capture circuit and the tracking circuit, and outputs navigation information including position, speed and time.

[0016] The beneficial effects of the present invention are as follows: a high-bit-width digital intermediate frequency signal output by a high-bit-width analog-to-digital conversion chip is converted into a low-bit-width digital intermediate frequency signal adapted to a capture circuit and a tracking circuit through a preprocessing method and a receiver adapted to changes in the strength of a pseudo-satellite pulse signal; the amplitude of the input signal of the high-bit-width analog-to-digital conversion chip is controlled through the preprocessing circuit, and when no pseudo-satellite pulse signal is input, the output power of the amplifier is controlled so that the amplitude bits of the high-bit-width digital intermediate frequency signal are the lower 3 bits, and the rest are sign bits, and when a pseudo-satellite pulse signal is input, the control parameters are the same as when no pseudo-satellite pulse signal is input; without changing the data bit width in the existing capture circuit and tracking circuit and without significantly increasing the circuit logic resources, the present invention can adapt to satellite navigation signals and pseudo-satellite pulse signals with changes in strength, thereby expanding the application range of the navigation receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the circuit diagram of a conventional navigation receiver.

[0018] Figure 2 It is the structural diagram of the preprocessing circuit.

[0019] Figure 3 Schematic diagram of a receiver that adapts to changes in the strength of pseudolite pulse signals. DETAILED DESCRIPTION

[0020] The present invention is further described below, but the protection scope of the present invention is not limited to the following description.

[0021] As attached Figure 2 As shown, a preprocessing method adapted to the strength change of pseudolite pulse signals comprises the following steps: S1: The high-bitwidth digital intermediate frequency signal (AD_in[N-1:0]) is input into the preprocessing circuit, which divides the high-bitwidth digital intermediate frequency signal into two paths, one of which is output to the power statistics and control module, and the other is output to the truncation selection module; S2: The power statistics and control module counts the noise power when there is no pseudo-satellite pulse signal input. The power statistics and control module outputs control parameters to the outside to control the output power of the amplifier so that the amplitude bits of the high-bit width digital intermediate frequency signal are the lower 3 bits, and the rest are sign bits; S3: The truncation selection module converts the high-bit width digital intermediate frequency signal into a 4-bit digital intermediate frequency signal (AD_in[N-1,2:0]) by taking the highest bit of the input as the sign bit and the lowest 3 bits as the amplitude bits. The 4-bit digital intermediate frequency signal is divided into two paths, one of which is output to the selector and the other is output to the absolute value module. S4: The absolute value module converts the 4-bit digital intermediate frequency signal into an unsigned number, first multiplies it with the external input parameter Coef_0, and then compares it with the external input parameter Threshold_0 to obtain the amplitude bit (Mag) in the 2-bit digital intermediate frequency signal; The value of the amplitude bit is 0 or 1; S5: Combine the sign bit AD_in[N-1] with the amplitude bit (Mag) in the 2-bit digital intermediate frequency signal, convert the encoding format, and obtain the encoded 2-bit digital intermediate frequency signal. The 2-bit digital intermediate frequency signal is output to the selector; S6: The selector selects a 4-bit digital intermediate frequency signal or a 2-bit digital intermediate frequency signal as a low-bit-width digital intermediate frequency signal to be output externally through an external input parameter Sel, and outputs the low-bit-width digital intermediate frequency signal to the capture circuit and the tracking circuit.

[0022] Furthermore, a preprocessing method is provided to adapt to the change in the strength of pseudolite pulse signals. When there is a pseudolite pulse signal input, the control parameters are the same as when there is no pseudolite pulse signal input.

[0023] Further, a preprocessing method adapted to the strength change of pseudolite pulse signal, the encoding format is: When the sign bit is 0 and the amplitude bit is 0, the effective value is 1; When the sign bit is 0 and the amplitude bit is 1, the effective value is 3; When the sign bit is 1 and the amplitude bit is 0, the effective value is -1; When the sign bit is 1 and the magnitude bit is 1, the effective value is -3.

[0024] As attached Figure 3 As shown, a receiver adapted to the strength change of pseudo-satellite pulse signals includes an antenna, a radio frequency front-end processing end, a high-bitwidth analog-to-digital conversion chip, and a baseband signal processing end; The baseband signal processing end includes a preprocessing circuit, a capture circuit, a tracking circuit, and a microprocessor; The antenna outputs an RF signal to the input end of the RF front-end processing end, the output end of the RF front-end processing end outputs an analog intermediate frequency signal to the input end of a high-bit-width analog-to-digital conversion chip, the output end of the high-bit-width analog-to-digital conversion chip outputs a high-bit-width digital intermediate frequency signal to the input end of a preprocessing circuit, and the output end of the preprocessing circuit outputs a low-bit-width digital intermediate frequency signal to the input ends of a capture circuit and a tracking circuit, respectively.

[0025] Further, a receiver adapted to the strength variation of pseudolite pulse signals, the RF front-end processing end includes a filter, a preamplifier, a down-conversion and an amplifier; The preprocessing circuit receives external control parameters to control the amplifier gain and controls the amplitude of the output analog intermediate frequency signal.

[0026] Furthermore, in a receiver adapted to changes in the strength of pseudolite pulse signals, the conversion bit number of the high-bit-width analog-to-digital conversion chip is higher than 11 bits.

[0027] Furthermore, in a receiver adapted to changes in the strength of pseudolite pulse signals, the low-bit-width digital intermediate frequency signal is in a 4-bit complement format or a 2-bit Sign Mag mode.

[0028] Furthermore, a receiver that adapts to changes in the strength of pseudo-satellite pulse signals, wherein the capture circuit receives a low-bitwidth digital intermediate frequency signal to capture satellite signals, and when a satellite signal is captured, the code phase and carrier Doppler frequency deviation are sent to a tracking circuit, wherein the tracking circuit receives the low-bitwidth digital intermediate frequency signal, the code phase and carrier Doppler frequency deviation of the capture circuit, tracks the satellite signal, completes control and solution operations on the capture circuit and the tracking circuit, and outputs navigation information including position, speed and time.

[0029] Specific embodiment 1 The principle of the preprocessing circuit converting the high-bitwidth digital intermediate frequency signal into a low-bitwidth digital intermediate frequency signal and sending it to the capture circuit and the tracking circuit is: (1) The influence of the bit width of the digital intermediate frequency signal on the sensitivity of the acquisition circuit and the tracking circuit. Under the condition that no frequency aliasing occurs, the sensitivity loss caused by a one-bit quantized digital intermediate frequency signal is 1.96dB, the sensitivity loss caused by a two-bit quantized digital intermediate frequency signal is 1.2dB, and the sensitivity loss caused by a three-bit quantized digital intermediate frequency signal is 0.6dB. Most navigation receivers rarely use analog-to-digital converters with more than four bits, because analog-to-digital converters with more than four bits no longer help to reduce sensitivity loss.

[0030] (2) When the power of the pseudo-satellite pulse signal and the satellite navigation signal at the antenna aperture of the navigation receiver is not higher than the noise power, taking the 10.23MHz code rate as an example, the noise power within the bandwidth is about -100dBmW, and the ground power of the satellite navigation signal is generally -115dBmW~-133dBmW, which is much smaller than the noise power value within the bandwidth. Therefore, the amplitude of the analog intermediate frequency signal output by the amplifier is constant. For the pseudo-satellite pulse signal, when the signal power is less than -100dBmW, it is the same as the satellite navigation signal and is submerged in the in-band noise. The amplitude of the analog intermediate frequency signal output by the amplifier is relatively constant.

[0031] (3) When the pseudo-satellite pulse signal power at the antenna aperture of the navigation receiver is higher than the noise power, taking the 10.23MHz code rate as an example, when the pseudo-satellite pulse signal power is greater than -100dBmW, it is higher than the in-band noise power. The sign bit of the low-bit-width digital intermediate frequency signal output by the preprocessing circuit is valid, while the amplitude bit is invalid. The digital intermediate frequency signal with valid sign bit and invalid amplitude bit has a sensitivity loss of slightly more than 2dB for the receiver. Since the pseudo-satellite pulse signal power is very strong, this sensitivity loss does not affect the navigation receiver's reception of pseudo-satellite signals with power higher than the noise power.

[0032] This scheme uses a preprocessing method and a receiver that adapt to the strength changes of pseudo-satellite pulse signals, converts the high-bit-width digital intermediate frequency signal output by a high-bit-width analog-to-digital conversion chip into a low-bit-width digital intermediate frequency signal that is adapted to the capture circuit and the tracking circuit; controls the amplitude of the input signal of the high-bit-width analog-to-digital conversion chip through the preprocessing circuit, and controls the output power of the amplifier when there is no pseudo-satellite pulse signal input, so that the amplitude bits of the high-bit-width digital intermediate frequency signal are the lower 3 bits, and the rest are sign bits, and when there is a pseudo-satellite pulse signal input, the control parameters are the same as when there is no pseudo-satellite pulse signal input; and can adapt to satellite navigation signals and pseudo-satellite pulse signals with varying strengths without changing the data bit width in the existing capture circuit and tracking circuit and without significantly increasing the circuit logic resources, thereby expanding the application range of the navigation receiver.

[0033] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A preprocessing method adapted to the strength change of pseudolite pulse signals, characterized in that: The following steps are involved: S1: The high-bitwidth digital intermediate frequency signal is input into the preprocessing circuit, which divides the high-bitwidth digital intermediate frequency signal into two paths, one of which is output to the power statistics and control module, and the other is output to the truncation selection module; S2: The power statistics and control module counts the noise power when there is no pseudo-satellite pulse signal input. The power statistics and control module outputs control parameters to the outside to control the output power of the amplifier so that the amplitude bits of the high-bit width digital intermediate frequency signal are the lower 3 bits, and the rest are sign bits; S3: The truncation selection module converts the high-bit width digital intermediate frequency signal into a 4-bit digital intermediate frequency signal by taking the highest bit of the input as the sign bit and the lowest 3 bits as the amplitude bits. The 4-bit digital intermediate frequency signal is divided into two paths, one of which is output to the selector and the other is output to the absolute value module; S4: The absolute value module converts the 4-bit digital intermediate frequency signal into an unsigned number, first multiplies it with the external input parameter Coef_0, and then compares it with the external input parameter Threshold_0 to obtain the amplitude bit in the 2-bit digital intermediate frequency signal; The value of the amplitude bit is 0 or 1; S5: Combine the sign bit with the amplitude bit in the 2-bit digital intermediate frequency signal, convert the encoding format, and obtain the encoded 2-bit digital intermediate frequency signal, and output the 2-bit digital intermediate frequency signal to the selector; S6: The selector selects a 4-bit digital intermediate frequency signal or a 2-bit digital intermediate frequency signal as a low-bit-width digital intermediate frequency signal to be output externally through an external input parameter Sel, and outputs the low-bit-width digital intermediate frequency signal to the capture circuit and the tracking circuit.

2. A preprocessing method for adapting to the strength change of pseudolite pulse signals according to claim 1, characterized in that: When there is a pseudolite pulse signal input, the control parameters are the same as when there is no pseudolite pulse signal input.

3. A preprocessing method for adapting to the strength change of pseudolite pulse signals according to claim 1, characterized in that: The encoding format is: When the sign bit is 0 and the amplitude bit is 0, the effective value is 1; When the sign bit is 0 and the amplitude bit is 1, the effective value is 3; When the sign bit is 1 and the amplitude bit is 0, the effective value is -1; When the sign bit is 1 and the magnitude bit is 1, the effective value is -3.

4. A receiver adapted to the strength change of pseudolite pulse signals, implemented by a preprocessing circuit of a preprocessing method adapted to the strength change of pseudolite pulse signals according to any one of claims 1 to 3, characterized in that: Including antenna, RF front-end processing end, high-bitwidth analog-to-digital conversion chip, and baseband signal processing end; The baseband signal processing end includes a preprocessing circuit, a capture circuit, a tracking circuit, and a microprocessor; The antenna outputs an RF signal to the input end of the RF front-end processing end, the output end of the RF front-end processing end outputs an analog intermediate frequency signal to the input end of a high-bit-width analog-to-digital conversion chip, the output end of the high-bit-width analog-to-digital conversion chip outputs a high-bit-width digital intermediate frequency signal to the input end of a preprocessing circuit, and the output end of the preprocessing circuit outputs a low-bit-width digital intermediate frequency signal to the input ends of a capture circuit and a tracking circuit, respectively.

5. A receiver adapted to the strength variation of pseudo-satellite pulse signals according to claim 4, characterized in that: The RF front-end processing end includes a filter, a preamplifier, a down-conversion and an amplifier; The preprocessing circuit receives external control parameters to control the amplifier gain and controls the amplitude of the output analog intermediate frequency signal.

6. A receiver adapted to the strength variation of pseudo-satellite pulse signals according to claim 4, characterized in that: The conversion bit number of the high-bit-width analog-to-digital conversion chip is higher than 11 bits.

7. A receiver adapted to the strength variation of pseudolite pulse signals according to claim 4, characterized in that: The low-bit-width digital intermediate frequency signal is in 4-bit complement format or 2-bit Sign Mag mode.

8. A receiver adapted to the strength variation of pseudolite pulse signals according to claim 4, characterized in that: The capture circuit receives a low-bit-width digital intermediate frequency signal and captures a satellite signal. When a satellite signal is captured, the code phase and carrier Doppler frequency deviation are sent to the tracking circuit. The tracking circuit receives the low-bit-width digital intermediate frequency signal, the code phase and carrier Doppler frequency deviation of the capture circuit, tracks the satellite signal, completes the control and solution operations of the capture circuit and the tracking circuit, and outputs navigation information including position, speed and time.

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