Low-orbit constellation conduction fusion signal generating and receiving method

Abstract

The invention discloses a low-orbit constellation conduction fusion signal generating and receiving method, and belongs to the technical field of satellite navigation and communication. According to the conduction fusion signal generation method, the real-time signal-to-noise ratio of an inter-satellite channel is estimated according to the inter-satellite distance, the power distribution proportion of a communication component and a navigation component is determined according to the real-time signal-to-noise ratio, and fusion of a communication signal and a navigation signal is achieved in a phase modulation mode. In the signal receiving method, demodulation separation of a communication component and a navigation component is completed in a directional separation mode. According to the method, the power ratio of the communication component to the navigation component is adaptively allocated according to the inter-satellite distance, so that the satellite navigation signal positioning precision can be improved and the autonomous navigation capability of a low-orbit navigation constellation can be enhanced on the premise of meeting the inter-satellite communication error rate requirement.

Description

Technical Field

[0001] The present invention belongs to the field of satellite navigation and communication technology, and in particular relates to a method for generating and receiving a low-orbit constellation communication-guidance fusion signal. Background Art

[0002] At present, low-orbit constellations are usually equipped with two channels, namely low-rate omnidirectional tracking and control channels and high-rate business data channels, which realize navigation positioning and data transmission respectively. The core is to realize navigation and communication functions. Navigation signals and communication signals are transmitted independently through two different frequencies, which not only requires a large bandwidth, but also requires the configuration of two sets of transmitting and receiving equipment, which requires high research and development costs.

[0003] The applicant believes that integrating navigation and communication functions can simplify onboard equipment, reduce power consumption, save frequency resources, improve hardware electromagnetic compatibility, integrate ground station resources, and reduce the complexity of the management system. In addition, by using communication links to transmit high-precision satellite time and position information, the satellite's own clock can be calibrated, a relative position relationship network of low-orbit constellations can be constructed, and the autonomous navigation capability of low-orbit constellations can be enhanced.

[0004] However, in the process of realizing communication and navigation fusion, how to allocate on-board power resources and improve navigation performance while ensuring the reliability of information transmission is still a difficult problem that researchers in this field urgently need to solve. Summary of the invention

[0005] In view of the above problems, the present invention proposes a method for generating and receiving low-orbit constellation communication and navigation fusion signals. The present invention adopts phase modulation to achieve the fusion of communication signals and navigation signals, and allocates the power ratio of communication components and navigation components according to the channel status of the inter-satellite link, which can improve the system navigation performance on the basis of ensuring the communication performance.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for generating a low-orbit constellation communication and guidance fusion signal, applied to a launching satellite, comprises the following steps:

[0008] Step 1, calculating the distance between the transmitting satellite and the receiving satellite based on the ephemeris information stored in the transmitting satellite and the position information of the receiving satellite;

[0009] Step 2: According to the distance between the two satellites and the gain of the satellite antenna, the real-time signal-to-noise ratio of the inter-satellite channel is estimated as:

[0010]

[0011] Among them, E b is the transmitted signal bit energy, N0 is the power spectral density of the noise, P tis the total transmitter power, G t is the transmitting antenna gain, G r is the receiving antenna gain, R b is the transmission signal bit rate, L fs (dB) = 10lg(4πdf / c) 2 is the free space transmission loss, d is the distance between the two satellites, f is the carrier frequency, c is the speed of light, and L0 represents the remaining losses including Doppler shift, antenna pointing error, and polarization loss;

[0012] Step 3, using the satellite historical measured data to draw the bit error rate curve of the communication-guide fusion signal under different signal weighting factors;

[0013] Step 4, determining the target communication bit error rate required by the service, and dividing the signal-to-noise ratio switching interval according to the intersection of the bit error rate curves of different signal weighting factors and the target bit error rate curve;

[0014] Step 5, in each signal-to-noise ratio switching interval, determine all signal weighting factors that can meet the target bit error rate requirement, and select the maximum value therein as the selected signal weighting factor;

[0015] Step 6, generating the phase of the communication component by subjecting the communication information to be transmitted to LDPC encoding, level conversion, Gaussian filter, and integrator;

[0016] Step 7, after the navigation information to be transmitted is subjected to level conversion and shaping filter, it is multiplied by the selected signal weighting factor to obtain the phase of the navigation component;

[0017] Step 8, add the phase of the communication component and the phase of the navigation component to obtain the communication-conduction fusion phase, and generate the communication-conduction fusion signal based on GMSK+PN after phase modulation:

[0018]

[0019] Among them, P t is the total transmitter power, ω is the carrier frequency, is the phase of the communication component, is the phase of the navigation component.

[0020] A method for receiving a communication-conductor fusion signal of a low-orbit constellation is applied to a receiving satellite and is used to receive and separate the communication-conductor fusion signal generated by the above method, comprising the following steps:

[0021] Step 1, performing GMSK demodulation on the received GMSK+PN conduction fusion signal to obtain the phase of the communication component;

[0022] Step 2, performing GMSK remodulation on the phase of the obtained communication component to obtain the phase of the regenerated communication signal;

[0023] Step 3, after conjugating the phase of the regenerated communication signal, perform complex domain correlation with the received GMSK+PN conduction fusion signal to obtain:

[0024]

[0025] in, is the low-pass equivalent of the received signal in the complex domain, To regenerate the communication signal phase, is the phase of the communication component, is the phase of the navigation component, n(t) is the noise in the transmission process;

[0026] Step 4: Take the imaginary part of the complex correlation result to obtain the navigation component separated from the GMSK+PN conduction fusion signal:

[0027]

[0028] in, To separate the noise carried in the navigation component;

[0029] Step 5, capturing and tracking the separated navigation component to achieve synchronous demodulation of the navigation signal;

[0030] Step 6, calculating and obtaining the position information of the transmitting satellite according to the synchronous demodulation result;

[0031] Step 7, update the ephemeris information of the receiving satellite itself and the position information of the transmitting satellite.

[0032] Compared with the existing low-orbit constellation communication and navigation link technology, the present invention has the following beneficial effects:

[0033] (1) The present invention is applicable to intersatellite links of low-orbit satellites and can enhance the autonomous navigation capability of low-orbit navigation constellations;

[0034] (2) The present invention adopts a communication-guidance fusion method based on GMSK+PN, which can improve the system frequency band utilization rate and realize the synchronous transmission of high-code rate communication data and high-precision navigation information;

[0035] (3) The present invention adopts a power allocation method based on signal-to-noise ratio, which can adaptively allocate the power of the communication component and the navigation component according to the inter-satellite distance, thereby improving the utilization rate of satellite-borne resources;

[0036] (4) The present invention adopts a directional separation method to separate the communication component and the navigation component in the communication-conduction fusion signal, reduce the mutual interference between the signal components, and improve the system demodulation performance.

[0037] In summary, the present invention adaptively allocates the power ratio of the communication component and the navigation component according to the inter-satellite distance, which can improve the positioning accuracy of satellite navigation signals and enhance the autonomous navigation capability of the low-orbit navigation constellation while meeting the inter-satellite communication bit error rate requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the principle of generating a GMSK+PN fusion signal in an embodiment of the present invention;

[0039] Figure 2 It is a schematic diagram of the principle of directional separation based on GMSK+PN in an embodiment of the present invention;

[0040] Figure 3 It is a schematic diagram of signal transmission between a transmitting satellite and a receiving satellite in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] A method for generating a low-orbit constellation communication and guidance fusion signal is applied to launching satellites, such as Figure 1 As shown, the following steps are included:

[0043] Step 1, calculating the distance between the transmitting satellite and the receiving satellite based on the ephemeris information stored in the transmitting satellite and the position information of the receiving satellite;

[0044] Step 2: According to the distance between the two satellites and the gain of the satellite antenna, the real-time signal-to-noise ratio of the inter-satellite channel is estimated as:

[0045]

[0046] Among them, E b is the transmitted signal bit energy, N0 is the power spectral density of the noise, P t is the total transmitter power, G t is the transmitting antenna gain, G r is the receiving antenna gain, R b is the transmission signal bit rate, L fs (dB) = 10lg(4πdf / c) 2 is the free space transmission loss, d is the distance between the two satellites, f is the carrier frequency, c is the speed of light, and L0 represents the remaining losses including Doppler shift, antenna pointing error, and polarization loss;

[0047] Step 3, using the satellite historical measured data to draw the bit error rate curve of the communication-guide fusion signal under different signal weighting factors;

[0048] Step 4, determining the target communication bit error rate required by the service, and dividing the signal-to-noise ratio switching interval according to the intersection of the bit error rate curves of different signal weighting factors and the target bit error rate curve;

[0049] Step 5, in each signal-to-noise ratio switching interval, determine all signal weighting factors that can meet the target bit error rate requirement, and select the maximum value therein as the selected signal weighting factor;

[0050] Step 6, generating the phase of the communication component by subjecting the communication information to be transmitted to LDPC encoding, level conversion, Gaussian filter, and integrator;

[0051] Step 7, after the navigation information to be transmitted is subjected to level conversion and shaping filter, it is multiplied by the selected signal weighting factor to obtain the phase of the navigation component;

[0052] Step 8, add the phase of the communication component and the phase of the navigation component to obtain the communication-conduction fusion phase, and generate the communication-conduction fusion signal based on GMSK+PN after phase modulation:

[0053]

[0054] Among them, P t is the total transmitter power, ω is the carrier frequency, is the phase of the communication component, is the phase of the navigation component.

[0055] A method for receiving a communication-conductor fusion signal of a low-orbit constellation is applied to a receiving satellite to receive and separate the communication-conductor fusion signal generated by the above method, such as Figure 2 As shown, the following steps are included:

[0056] Step 1, performing GMSK demodulation on the received GMSK+PN conduction fusion signal to obtain the phase of the communication component;

[0057] Step 2, performing GMSK remodulation on the phase of the obtained communication component to obtain the phase of the regenerated communication signal;

[0058] Step 3, after conjugating the phase of the regenerated communication signal, perform complex domain correlation with the received GMSK+PN conduction fusion signal to obtain:

[0059]

[0060] in, is the low-pass equivalent of the received signal in the complex domain, To regenerate the communication signal phase, is the phase of the communication component, is the phase of the navigation component, n(t) is the noise in the transmission process;

[0061] Step 4: Take the imaginary part of the complex correlation result to obtain the navigation component separated from the GMSK+PN conduction fusion signal:

[0062]

[0063] in, To separate the noise carried in the navigation component;

[0064] Step 5, capturing and tracking the separated navigation component to achieve synchronous demodulation of the navigation signal;

[0065] Step 6, calculating and obtaining the position information of the transmitting satellite according to the synchronous demodulation result;

[0066] Step 7, update the ephemeris information of the receiving satellite itself and the position information of the transmitting satellite.

[0067] In the low-orbit constellation communication-guidance fusion signal receiving method, the navigation signal component accounts for a relatively small proportion of the fusion signal and can be regarded as a small phase shift of the communication component; the navigation signal component is regarded as "noise" in the transmission process, and the received communication-guidance fusion signal is directly demodulated by GMSK to obtain a restored communication signal; the restored communication signal is re-modulated by GMSK to obtain the phase of the regenerated communication signal; the phase of the regenerated communication signal is complex-correlated with the received signal to complete the separation of the communication-guidance fusion signal to obtain the restored navigation signal, which is then sent to the navigation signal synchronization module to solve the satellite position and inter-satellite distance information.

[0068] In the low-orbit constellation communication and navigation fusion signal generation method, the power allocation of the communication component and the navigation component is completed by a power allocation method based on real-time signal-to-noise ratio, such as Figure 3 shown.

[0069] The receiving satellite forwards the calculated satellite position and inter-satellite distance information to the transmitting satellite. The transmitting satellite estimates the real-time signal-to-noise ratio based on the inter-satellite distance and the onboard antenna gain:

[0070]

[0071] Among them, E b is the transmitted signal bit energy, N0 is the power spectral density of the noise, P t is the total transmitter power, G t is the transmitting antenna gain, G r is the receiving antenna gain, R b is the transmission signal bit rate, L fs (dB) = 10lg(4πdf / c) 2is the free space transmission loss, d is the distance between the two satellites, f is the carrier frequency, c is the speed of light, and L0 represents the remaining losses including Doppler frequency shift, antenna pointing error and polarization loss.

[0072] The power ratio of the communication component and the navigation component is determined according to the real-time signal-to-noise ratio, and the signal weighting factor h is used to calculate the power ratio of the communication component and the navigation component. c Control. c The larger the h is, the more navigation components are contained in the communication-guidance fusion signal, the better the navigation performance is, and the corresponding communication bit error rate is lower. c When it is 0, the signal no longer contains the navigation component and the transmitted signal becomes a regular communication signal.

[0073] The power control principle of the communication component and the navigation component is "to maximize the navigation performance of the system while meeting the target communication bit error rate". The specific method is:

[0074] Step 101, using simulation or measured data, draw a graph based on the conduction fusion signal at different weighting factors h. c (such as 0.1, 0.2, 0.3, 0.4...) bit error rate curve;

[0075] Step 102: according to different weighting factors h c The bit error rate curve and the target bit error rate (such as 10 -5 ) The intersection of the curves divides the signal-to-noise ratio switching interval;

[0076] Step 103: Determine the weighting factor h that can meet the target bit error rate requirement in each signal-to-noise ratio switching interval. c , where the largest h c is the selected weighting factor;

[0077] Step 104: according to the selected weighting factor h c , determine the communication component power P s and navigation component power P c for:

[0078]

[0079] Among them, J n (×) is the first kind nth order Bessel function.

[0080] In summary, the present invention can be used for the generation and reception of communication and navigation fusion signals of low-orbit constellations. It adopts a method based on the inter-satellite distance and the real-time signal-to-noise ratio to adaptively select signal weighting factors to complete the power allocation of the communication component and the navigation component. It can improve the navigation and positioning accuracy of low-orbit satellites and enhance the autonomous navigation capability of low-orbit navigation constellations while meeting the requirements of the bit error rate of inter-satellite communications. It is of great significance to the construction, operation and service of low-orbit navigation constellations.

Claims

1. A method for generating a low-orbit constellation communication and guidance fusion signal, characterized in that: Applied to launching a satellite, the method comprises the following steps: Step 1, calculating the distance between the transmitting satellite and the receiving satellite based on the ephemeris information stored in the transmitting satellite and the position information of the receiving satellite; Step 2: According to the distance between the two satellites and the gain of the satellite antenna, the real-time signal-to-noise ratio of the inter-satellite channel is estimated as: Among them, E b is the transmitted signal bit energy, N0 is the power spectral density of the noise, P t is the total transmitter power, G t is the transmitting antenna gain, G r is the receiving antenna gain, R b is the transmission signal bit rate, L fs (dB) = 10lg(4πdf / c) 2 is the free space transmission loss, d is the distance between the two satellites, f is the carrier frequency, c is the speed of light, and L0 represents the remaining losses including Doppler frequency shift, antenna pointing error and polarization loss; Step 3, using the satellite historical measured data to draw the bit error rate curve of the communication-guide fusion signal under different signal weighting factors; Step 4, determining the target communication bit error rate required by the service, and dividing the signal-to-noise ratio switching interval according to the intersection of the bit error rate curves of different signal weighting factors and the target bit error rate curve; Step 5, in each signal-to-noise ratio switching interval, determine all signal weighting factors that can meet the target bit error rate requirement, and select the maximum value therein as the selected signal weighting factor; Step 6, generating the phase of the communication component by subjecting the communication information to be transmitted to LDPC encoding, level conversion, Gaussian filter, and integrator; Step 7, after the navigation information to be transmitted is subjected to level conversion and shaping filter, it is multiplied by the selected signal weighting factor to obtain the phase of the navigation component; Step 8, add the phase of the communication component and the phase of the navigation component to obtain the communication-conduction fusion phase, and generate the communication-conduction fusion signal based on GMSK+PN after phase modulation: Among them, P t is the total transmitter power, ω is the carrier frequency, is the phase of the communication component, is the phase of the navigation component.

2. A method for receiving low-orbit constellation communication and guidance fusion signals, characterized in that: The method is applied to a receiving satellite and is used to receive and separate the communication-conduction fusion signal generated by claim 1, comprising the following steps: Step 1, performing GMSK demodulation on the received GMSK+PN conduction fusion signal to obtain the phase of the communication component; Step 2, performing GMSK remodulation on the phase of the obtained communication component to obtain the phase of the regenerated communication signal; Step 3, after conjugating the phase of the regenerated communication signal, perform complex domain correlation with the received GMSK+PN conduction fusion signal to obtain: in, is the low-pass equivalent of the received signal in the complex domain, To regenerate the communication signal phase, is the phase of the communication component, is the phase of the navigation component, n(t) is the noise in the transmission process; Step 4: Take the imaginary part of the complex correlation result to obtain the navigation component separated from the GMSK+PN conduction fusion signal: in, To separate the noise carried in the navigation component; Step 5, capturing and tracking the separated navigation component to achieve synchronous demodulation of the navigation signal; Step 6, calculating and obtaining the position information of the transmitting satellite according to the synchronous demodulation result; Step 7, update the ephemeris information of the receiving satellite itself and the position information of the transmitting satellite.

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