Rotor blockage fading adaptive tracking method and apparatus for helicopter satellite communications

Abstract

This invention discloses an adaptive tracking method and apparatus for rotor obstruction fading in helicopter satellite communication. Specifically, it involves: establishing a mathematical model of rotor obstruction in helicopter satellite communication; acquiring the signal after rotor obstruction fading detected by the helicopter's onboard communication terminal; adding noise immunity filtering to improve the detection signal-to-noise ratio; generating a rotor obstruction waveform based on measured rotor obstruction fading parameters; performing coarse synchronization between the generated and detected waveforms to accelerate system synchronization; comparing the parameter errors between the rotor obstruction waveform generated by a local periodic pulse generator and the measured rotor obstruction waveform to obtain error detection results; and using the error detection results to correct the period, phase, and width of the rotor obstruction waveform generated by the local periodic pulse generator, enabling it to adaptively track changes in rotor obstruction. This invention can adaptively track changes in helicopter rotor obstruction fading depth and obstruction time, improving the stability of helicopter satellite communication.

Description

Technical Field

[0001] This invention relates to the fields of satellite mobile communication systems and helicopter communication technology, and in particular to an adaptive tracking method for rotor shielding fading in helicopter satellite communication. Background Technology

[0002] Helicopters are widely used in various fields, undertaking tasks such as material transportation, emergency rescue and disaster relief, search and rescue, and security for major events. Due to the complexity of helicopter missions, high-reliability beyond-line-of-sight (BLOS) communication throughout the entire flight is a challenge. Satellite communication is an effective means to solve this problem. Compared to traditional communication methods, helicopter satellite communication not only has advantages such as large communication capacity, long communication distance, and the ability to operate at any time, but also wide coverage and strong communication stability, thus possessing significant research value.

[0003] Due to the limitations of helicopter fuselage layout and the requirement for satellite communication antennas to be constantly aligned with satellites, helicopter satellite communication antennas are typically mounted above the tail boom, below the rotor. Therefore, during satellite communication, the signal is affected by rotor obstruction. In recent years, significant research has been conducted on channel coding, forward link, and backlink communication strategies to address rotor obstruction, resulting in a substantial increase in helicopter communication speeds. The maximum communication speed achievable using geostationary orbit communication satellites abroad has reached 10 Mbps, while in China it has reached 2 Mbps.

[0004] Research on helicopter satellite communication began earlier abroad, with countries such as the United States, Russia, and Japan investing significant financial and human resources and achieving groundbreaking progress. In 2004, the world's first helicopter-borne satellite communication system, led by the Japan Institute of Information and Communications Technology (NJCT), was unveiled. This system employs a time-diversity multi-level transmission mechanism for its forward link and a rotor-synchronized burst transmission mode for its backward link. The system can transmit captured images back via satellite without relays. Operating in the Ku-band, with antennas mounted on both sides of the fuselage, the system achieves a forward transmission rate of 64 Kbps and a return transmission rate of 384 Kbps.

[0005] In 2009, ViaSat, an American company, successfully developed a broadband helicopter satellite communication system. Operating in the Ku band, the system employs dual time diversity technology in the forward link, achieving a maximum speed of 10 Mbps; the return link uses a burst transmission mechanism, reaching a maximum transmission rate of 512 Kbps. The system uses BPSK modulation and Turbo coding, and employs spread spectrum technology to reduce interference. Subsequently, the US installed it on the Black Hawk helicopter, with its single antenna positioned at the junction of the fuselage and tail boom. In 2015, Hughes Aircraft Company, also an American company, successfully developed an end-to-end airborne satellite communication system operating in the Ka band, achieving a maximum speed of 8 Mbps. This system was later applied to the Bell 407 helicopter. This system offers improved real-time performance, clarity, and communication range. Furthermore, the system features dynamically configurable waveform parameters, making it usable on mainstream modern drones, and its communication process is independent of the number and size of rotors.

[0006] In recent years, my country has invested heavily in this area and achieved some results. During the 2008 security operations, the Mi-171 helicopter equipped with an airborne satellite communication system featuring a 0.8-meter parabolic antenna was put into use. This system operates in the Ku band, employs a dual-antenna design with antennas positioned on both sides of the fuselage, and can achieve a communication rate of 5 Mbps. However, due to the increased weight of the aircraft with dual antennas, its flight speed is limited to 220 km / h. The system is primarily used in security missions.

[0007] Currently, thanks to the efforts of researchers, many research results have been achieved in addressing issues such as antenna installation location, rotor obstruction, and communication link design during helicopter communication. For example, in 2017, the article "Research on Test and Verification Methods for Satellite Communication Equipment's Resistance to Helicopter Rotor Obstruction" published by Ruan Xianli et al. first analyzed the mission performed by the helicopter and then proposed a gap detection algorithm based on nonlinear transform FFT to determine the obstruction window. In the same year, the article "Research on Anti-rotor Obstruction Methods for Helicopter-borne Satellite Communication Systems" published by Tang Mingwen proposed a method based on signal power rotor gap bursts to resist the impact of the rotor on communication.

[0008] In helicopter satellite communication, conventional satellite communication systems cannot function properly due to rotor obstruction. Therefore, there is an urgent need to design a method to detect helicopter rotor obstruction. This method should enable the airborne terminal to automatically track changes in the helicopter rotor rotation speed or phase changes when the helicopter changes its flight attitude, even under weak satellite communication signal reception conditions. This would help counteract the fading of large blocks of codewords caused by helicopter rotor obstruction and thus solve the problem of helicopters and satellites being unable to communicate when rotor obstruction exists. Summary of the Invention

[0009] The purpose of this invention is to provide a helicopter rotor obstruction tracking method with fast synchronization speed, high detection efficiency, and high stability.

[0010] The technical solution to achieve the purpose of this invention is: an adaptive tracking method for rotor blockage fading in helicopter satellite communication, comprising the following steps:

[0011] Step 1: Establish a mathematical model of rotor blockage in helicopter satellite communication;

[0012] Step 2: Obtain the signal after rotor obstruction fading detected by the helicopter's airborne communication terminal, and add an anti-noise filter to improve the detection signal-to-noise ratio;

[0013] Step 3: Generate a rotor blocking waveform based on the measured rotor blocking fading parameters, and perform coarse synchronization between the generated rotor blocking waveform and the detected rotor blocking waveform;

[0014] Step 4: Compare the parameter error between the rotor blocking waveform generated by the local periodic pulse generator and the measured rotor blocking waveform to obtain the error detection result;

[0015] Step 5: Use the error detection results to correct the period, phase, and width of the rotor blocking waveform generated by the local periodic pulse generator, thereby adaptively tracking changes in rotor blocking.

[0016] Furthermore, the mathematical model for establishing rotor blockage in helicopter satellite communication described in step 1 is as follows:

[0017] Step 1.1: Based on the rotor blocking process, from the rotor cutting into one side of the satellite communication antenna main surface to blocking and cutting out from the other side, establish a plane rectangular coordinate system, set the coordinates of the antenna center as (c,c), take the center of the rotor as the origin of the coordinate axis, and set the angle between the rotor axis direction and the coordinate axis as θ.

[0018] Step 1.2: Set the radius of the airborne satellite antenna to r, and the width of the helicopter rotor to 2D, where 2D < r; set the angle between the antenna and the satellite signal and the helicopter rotor during helicopter flight to be... Therefore, the equivalent width of the projection when the helicopter rotor blocks the antenna is calculated as follows:

[0019]

[0020] Where 2d < r;

[0021] Let the distances from the antenna center (c,c) to the two sides of the rotor be h1 and h2 respectively. Let h1 be the distance to the side that enters the antenna first, and h2 be the distance to the other side. Let α1 be the angle between the radius of the intersection of the side that enters the antenna first and the radar circumference and the radius of h1, and α2 be the angle between the radius of the intersection of the other side and the radar circumference and the radius of h2.

[0022] Step 1.3: Calculate the values ​​of the six critical points θ1 to θ6: front side entering the radar, rear side entering the radar, front side reaching the center of the circle, rear side reaching the center of the circle, front side leaving the radar, and rear side leaving the radar. The specific calculation process is as follows:

[0023]

[0024] Step 1.4: Based on the value of θ, divide the entire shading process into six segments, calculate the shading area of ​​each segment, and then synthesize the theoretical formula for the change of the shading area S with θ throughout the entire shading process:

[0025]

[0026] The formulas for calculating h1, h2, α1, and α2 for each θ are as follows:

[0027] When θ2 < θ < θ1, the formulas for calculating h1, h2, α1, and α2 are:

[0028]

[0029] When θ3 < θ < θ2, the formulas for calculating h1, h2, α1, and α2 are:

[0030] h2 = h1 + 2w

[0031] when When h1, h2, α1, and α2 are calculated, the formulas are as follows:

[0032] h1 + h2 = 2w, h1 < h2

[0033] when When h1, h2, α1, and α2 are calculated, the formulas are as follows:

[0034] h1 + h2 = 2w, h1 > h2

[0035] When θ5 < θ < θ4, the formulas for calculating h1, h2, α1, and α2 are:

[0036] h1 = 2w + h2

[0037] When θ6 < θ < θ5, the formulas for calculating h1, h2, α1, and α2 are:

[0038]

[0039] Furthermore, the transfer function of the noise immunity filter described in step 2 is:

[0040]

[0041] Where α is a filter parameter, typically taking the value of...

[0042] Further, step 3, which involves generating a rotor blocking waveform based on the measured rotor blocking fading parameters and performing coarse synchronization between the generated and detected rotor blocking waveforms, is detailed as follows:

[0043] Step 3.1: Measure the occlusion fading parameters, including the width and period of the occlusion fading;

[0044] Step 3.2: Based on the measured parameters and the position of the blocking pulse, generate a local rotor blocking periodic pulse using a local periodic pulse generator according to the measured parameters, and generate a rotor blocking waveform.

[0045] Step 3.3: Compare the generated rotor obstruction waveform with the detected rotor obstruction waveform, measure the phase, and adjust the phase of the generated signal to be basically aligned with the phase of the detected signal.

[0046] Furthermore, the measurement of occlusion fading parameters in step 3.1 includes the width and period of the occlusion fading, as detailed below:

[0047] The detection threshold for channel fading is set to 0.85 of the average signal power. When the detected signal strength is below the threshold, it indicates channel signal fading. This yields a periodic channel fading pulse, and the average period and average pulse width of the pulse are measured.

[0048] Furthermore, the measurement of occlusion fading parameters described in step 3.1 needs to be performed multiple times.

[0049] Further, in step 4, the parameter error between the rotor blocking waveform generated by the local periodic pulse generator and the measured rotor blocking waveform is compared to obtain the error detection result, as follows:

[0050] The error detection curve is obtained by correlating and accumulating the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform. When the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform slide relative to each other, the error of the correlation accumulation operation also changes accordingly, resulting in a typical error detection curve. The obtained error detection result also shows periodicity.

[0051] An adaptive tracking device for rotor blockage fading in helicopter satellite communication is provided. This device implements the aforementioned adaptive tracking method for rotor blockage fading in helicopter satellite communication. The device comprises first to fifth modules, wherein:

[0052] The first module is used to establish a mathematical model of rotor blockage in helicopter satellite communication;

[0053] The second module acquires the signal after rotor obstruction fading detected by the helicopter's airborne communication terminal, and adds an anti-noise filter to improve the detection signal-to-noise ratio.

[0054] The third module generates a rotor blocking waveform based on the measured rotor blocking fading parameters, and performs coarse synchronization between the generated rotor blocking waveform and the detected rotor blocking waveform.

[0055] The fourth module compares the parameter error between the rotor blocking waveform generated by the local periodic pulse generator and the measured rotor blocking waveform to obtain the error detection result;

[0056] The fifth module uses the error detection results to correct the period, phase, and width of the rotor blocking waveform generated by the local periodic pulse generator, thereby adaptively tracking changes in rotor blocking.

[0057] A mobile terminal includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the aforementioned rotor fading adaptive tracking method for helicopter satellite communication.

[0058] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the rotor fading adaptive tracking method for helicopter satellite communication.

[0059] Compared with the prior art, the present invention has the following significant advantages: (1) It uses an anti-noise filter to filter the received satellite communication signal which contains a lot of noise and is very weak. The filtered signal can reliably detect rotor blockage, which improves the signal-to-noise ratio of rotor blockage detection; (2) It uses a fast synchronization technology for rotor blockage waveform. According to the rotor blockage period, the synchronization parameters are preset in the synchronization module. Coarse synchronization is performed before tracking, which speeds up the synchronization speed of the receiving system; (3) It uses an adaptive synchronization tracking technology for rotor blockage fading. When the error between the local rotor blockage and the received rotor blockage is detected, the period, phase and width of the local periodic pulse generator are corrected so that it can adaptively track the changes in rotor blockage fading depth and blockage time caused by the helicopter heading and different maneuvers, which improves the stability of helicopter satellite communication. Attached Figure Description

[0060] Figure 1 This is a flowchart illustrating the adaptive tracking method for rotor fading in helicopter satellite communication according to the present invention.

[0061] Figure 2 This is a schematic diagram illustrating the principle of rotor shielding in helicopter satellite communication in the embodiment.

[0062] Figure 3 This is a schematic diagram illustrating the rotor blocking process in the embodiment.

[0063] Figure 4 The graph shows the signal fading curves of the helicopter satellite communication rotor blocked in the example.

[0064] Figure 5 This is a waveform diagram of channel fading detected by the airborne terminal in the embodiment.

[0065] Figure 6 The figures show the rotor blocking parameters measured in the actual embodiment and the locally generated rotor blocking pulse curve.

[0066] Figure 7 This is an error curve diagram of rotor obstruction detection in the embodiment.

[0067] Figure 8 The image shows the waveform curve of rotor obstruction detection in the embodiment. Detailed Implementation

[0068] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0069] Due to the limitations of helicopter fuselage layout and the requirement for satellite communication antennas to be constantly aligned with satellites, helicopter satellite communication antennas are generally mounted above the helicopter's tail boom, below the rotor. Figure 2 As shown, satellite communication signals can be affected by helicopter rotor obstruction during satellite communication.

[0070] Combination Figure 1 The present invention discloses an adaptive tracking method for rotor blockage fading in helicopter satellite communication, comprising the following steps:

[0071] Step 1: Establish a mathematical model of rotor blockage in helicopter satellite communication, combined with... Figure 3 The details are as follows:

[0072] Step 1.1: Based on the rotor blocking process, from the rotor cutting into one side of the satellite communication antenna main surface to blocking and cutting out from the other side, establish a plane rectangular coordinate system, set the coordinates of the antenna center as (c,c), take the center of the rotor as the origin of the coordinate axis, and set the angle between the rotor axis direction and the coordinate axis as θ.

[0073] Step 1.2: Set the radius of the airborne satellite antenna to r, and the width of the helicopter rotor to 2D, where 2D < r; set the angle between the antenna and the satellite signal and the helicopter rotor during helicopter flight to be... Therefore, the equivalent width of the projection when the helicopter rotor blocks the antenna is calculated as follows:

[0074]

[0075] Where 2d < r;

[0076] Let the distances from the antenna center (c,c) to the two sides of the rotor be h1 and h2 respectively. Let h1 be the distance to the side that enters the antenna first, and h2 be the distance to the other side. Let α1 be the angle between the radius of the intersection of the side that enters the antenna first and the radar circumference and the radius of h1, and α2 be the angle between the radius of the intersection of the other side and the radar circumference and the radius of h2.

[0077] Step 1.3: Calculate the values ​​of the six critical points θ: front side entering the radar, rear side entering the radar, front side reaching the center of the circle, rear side reaching the center of the circle, front side leaving the radar, and rear side leaving the radar. The specific calculation process is as follows:

[0078]

[0079] Step 1.4: Based on the value of θ, divide the entire shading process into six segments, calculate the shading area of ​​each segment, and then synthesize the theoretical formula for the change of the shading area S with θ throughout the entire shading process:

[0080]

[0081] The formulas for calculating h1, h2, α1, and α2 for each θ are as follows:

[0082] When θ2 < θ < θ1, the formulas for calculating h1, h2, α1, and α2 are:

[0083]

[0084] When θ3 < θ < θ2, the formulas for calculating h1, h2, α1, and α2 are:

[0085] h2 = h1 + 2w

[0086] when When h1, h2, α1, and α2 are calculated, the formulas are as follows:

[0087] h1 + h2 = 2w, h1 < h2

[0088] when When h1, h2, α1, and α2 are calculated, the formulas are as follows:

[0089] h1 + h2 = 2w, h1 > h2

[0090] When θ5 < θ < θ4, the formulas for calculating h1, h2, α1, and α2 are:

[0091] h1 = 2w + h2

[0092] When θ6 < θ < θ5, the formulas for calculating h1, h2, α1, and α2 are:

[0093]

[0094] Step 2: Obtain the signal after rotor obstruction fading detected by the helicopter's onboard communication terminal, and add an anti-noise filter to improve the detection signal-to-noise ratio; the transfer function of the anti-noise filter is:

[0095]

[0096] Where α is a filter parameter, typically taking the value of...

[0097] Step 3: Generate a rotor blocking waveform based on the measured rotor blocking fading parameters, and perform coarse synchronization between the generated rotor blocking waveform and the detected rotor blocking waveform to speed up system synchronization. The details are as follows:

[0098] Step 3.1: Measure the occlusion fading parameters, including the width and period of the occlusion fading, as follows:

[0099] The detection threshold for channel fading is set to 0.85 of the average signal power. When the detected signal strength is below this threshold, it indicates channel signal fading. This yields a channel fading pulse that exhibits a basic periodicity. The average period and average pulse width of this pulse are then measured. Due to the presence of channel noise, multiple measurements are required to improve test accuracy.

[0100] Step 3.2: Based on the measured parameters and the position of the blocking pulse, generate a local rotor blocking periodic pulse using a local periodic pulse generator according to the measured parameters, and generate a rotor blocking waveform.

[0101] Step 3.3: Compare the generated rotor obstruction waveform with the detected rotor obstruction waveform, measure the phase, and adjust the phase of the generated signal to be basically aligned with the phase of the detected signal.

[0102] Step 4: Compare the parameter errors between the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform to obtain the error detection results, as follows:

[0103] The error detection curve is obtained by correlating and accumulating the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform. When the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform slide relative to each other, the error of the correlation accumulation operation also changes accordingly, resulting in a typical error detection curve, which also exhibits periodicity.

[0104] Step 5: Use the error detection results to correct the period, phase, and width of the rotor blocking waveform generated by the local periodic pulse generator, so that it can adaptively track changes in rotor blocking.

[0105] The present invention also provides a rotor blockage fading adaptive tracking device for helicopter satellite communication. This device is used to implement the aforementioned rotor blockage fading adaptive tracking method for helicopter satellite communication. The device includes first to fifth modules, wherein:

[0106] The first module is used to establish a mathematical model of rotor blockage in helicopter satellite communication;

[0107] The second module acquires the signal after rotor obstruction fading detected by the helicopter's airborne communication terminal, and adds an anti-noise filter to improve the detection signal-to-noise ratio.

[0108] The third module generates a rotor blocking waveform based on the measured rotor blocking fading parameters, and performs coarse synchronization between the generated rotor blocking waveform and the detected rotor blocking waveform.

[0109] The fourth module compares the parameter error between the rotor blocking waveform generated by the local periodic pulse generator and the measured rotor blocking waveform to obtain the error detection result;

[0110] The fifth module uses the error detection results to correct the period, phase, and width of the rotor blocking waveform generated by the local periodic pulse generator, thereby adaptively tracking changes in rotor blocking.

[0111] The present invention also provides a mobile terminal, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the aforementioned rotor fading adaptive tracking method for helicopter satellite communication.

[0112] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the rotor fading adaptive tracking method for helicopter satellite communication.

[0113] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0114] Example

[0115] This embodiment provides an adaptive tracking method for rotor blockage fading in helicopter satellite communication, such as... Figure 1 As shown, it includes the following steps:

[0116] Step 1: Establish a mathematical model of rotor blockage in helicopter satellite communication, combined with... Figure 3 The details are as follows:

[0117] Step 1.1: Based on the rotor blocking process, from the rotor cutting into one side of the satellite communication antenna main surface to blocking and cutting out from the other side, establish a plane rectangular coordinate system, set the coordinates of the antenna center as (c,c), take the center of the rotor as the origin of the coordinate axis, and set the angle between the rotor axis direction and the coordinate axis as θ.

[0118] Step 1.2: Set the radius of the airborne satellite antenna to r, and the width of the helicopter rotor to 2D, where 2D < r; set the angle between the antenna and the satellite signal and the helicopter rotor during helicopter flight to be... Therefore, the equivalent width of the projection when the helicopter rotor blocks the antenna is calculated as follows:

[0119]

[0120] Where 2d < r;

[0121] Let the distances from the antenna center (c,c) to the two sides of the rotor be h1 and h2 respectively. Let h1 be the distance to the side that enters the antenna first, and h2 be the distance to the other side. Let α1 be the angle between the radius of the intersection of the side that enters the antenna first and the radar circumference and the radius of h1, and α2 be the angle between the radius of the intersection of the other side and the radar circumference and the radius of h2.

[0122] Step 1.3: Calculate the values ​​of the six critical points θ: front side entering the radar, rear side entering the radar, front side reaching the center of the circle, rear side reaching the center of the circle, front side leaving the radar, and rear side leaving the radar. The specific calculation process is as follows:

[0123]

[0124]

[0125] Step 1.4: Based on the value of θ, divide the entire shading process into six segments, calculate the shading area of ​​each segment, and then synthesize the theoretical formula for the change of the shading area S with θ throughout the entire shading process:

[0126]

[0127] The formulas for calculating h1, h2, α1, and α2 for each θ are as follows:

[0128] When θ2 < θ < θ1, the formulas for calculating h1, h2, α1, and α2 are:

[0129]

[0130] When θ3 < θ < θ2, the formulas for calculating h1, h2, α1, and α2 are:

[0131] h2 = h1 + 2w

[0132] when When h1, h2, α1, and α2 are calculated, the formulas are as follows:

[0133] h1 + h2 = 2w, h1 < h2

[0134] when When h1, h2, α1, and α2 are calculated, the formulas are as follows:

[0135] h1 + h2 = 2w, h1 > h2

[0136] When θ5 < θ < θ4, the formulas for calculating h1, h2, α1, and α2 are:

[0137] h1 = 2w + h2

[0138] When θ6 < θ < θ5, the formulas for calculating h1, h2, α1, and α2 are:

[0139]

[0140] In reality, the rotor sweeps across the helicopter antenna at a frequency of about 15-20 times per second, blocking 1 / 10 to 1 / 6 of the signal data each time. Due to differences in information transmission rate and codeword length, each codeword may be blocked by the blade more than once, and the position of the blocked content in the data frame is not fixed. Figure 4 The image shows the measured signal envelope attenuation caused by the rotor blockage of a satellite communication system. The blockage period is 13 times / second, the signal fading depth caused by the blockage is 15dB, and the signal-to-noise ratio is 12dB.

[0141] In summary, due to the influence of helicopter rotor obstruction on the signal, the signal power will be attenuated to varying degrees, thus affecting normal communication and, in severe cases, causing communication interruption. Therefore, it is necessary to detect and synchronously track the problem of helicopter signal being affected by rotor obstruction during communication, in order to resist the large-scale code word attenuation caused by helicopter rotor obstruction, thereby solving the problem of helicopters and satellites being unable to communicate when rotor obstruction exists.

[0142] Due to the inertia of rotor rotation, the rate of change of rotational speed and the proportion of rotor blockage will not change abruptly, and the fading of communication signals is periodic. Therefore, filtering and prediction techniques can be used to obtain a signal fading model of rotor blockage. Based on the changes in received signal fading, the helicopter airborne communication terminal can accurately detect the transmission fading of the channel using the signal fading model. Corresponding anti-rotor blockage technology measures can then be adopted in the receiving and transmitting equipment of the airborne terminal to overcome its influence.

[0143] Step 2: The signal detected by the helicopter's onboard communication terminal after rotor obstruction fading is unreliable because satellite communication signals are very weak and the channel has significant noise. Therefore, noise immunity filtering is needed to improve the signal-to-noise ratio. The transfer function of the noise immunity filter is:

[0144]

[0145] Where α is a filter parameter, typically taking the value of... The filtered signal fading pulse is as follows Figure 5 As shown in the figure, the signal-to-noise ratio of the detected waveform after noise filtering is significantly improved for rotor obstruction detection, but there are still obvious periodic and phase errors.

[0146] Step 3: Since the rotor blocking period is tens of milliseconds, the synchronization time would be long if a conventional synchronization algorithm were used. Therefore, a rotor blocking waveform is generated based on the measured rotor blocking fading parameters, and coarse synchronization is performed between the generated rotor blocking waveform and the detected rotor blocking waveform to speed up the system synchronization. Figure 6 As shown, the details are as follows:

[0147] Step 3.1: Measure the occlusion fading parameters, including the width and period of the occlusion fading, as follows:

[0148] The detection threshold for channel fading is set to 0.85 of the average signal power. When the detected signal strength is below this threshold, it indicates channel signal fading. This yields a channel fading pulse that exhibits a basic periodicity. The average period and average pulse width of this pulse are then measured. Due to the presence of channel noise, multiple measurements are required to improve test accuracy.

[0149] Step 3.2: Based on the measured parameters and the position of the blocking pulse, generate a local rotor blocking periodic pulse using a local periodic pulse generator according to the measured parameters, and generate a rotor blocking waveform.

[0150] Step 3.3: Compare the generated rotor obstruction waveform with the detected rotor obstruction waveform, measure the phase, and adjust the phase of the generated signal to be basically aligned with the phase of the detected signal.

[0151] Step 4: Compare the parameter errors between the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform to obtain the error detection results, such as... Figure 8 As shown, the details are as follows:

[0152] The error detection curve is obtained by correlating and accumulating the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform. When the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform slide relative to each other, the error of the correlation accumulation operation also changes accordingly, resulting in a typical error detection curve, which also exhibits periodicity.

[0153] Step 5: Use the error detection results to correct the period, phase, and width of the rotor obstruction waveform generated by the local periodic pulse generator, so that it can adaptively track changes in rotor obstruction. The main working waveform is as follows: Figure 8 As shown in the figure, pulse 4 and pulse 6 represent the cases of erroneously generated pulses and missing pulses, respectively.

[0154] Even when there is significant noise in the channel, causing the signal fading pulse detector to generate false pulses or leak pulses, this invention can still maintain the synchronization of the rotor obstruction synchronizer. Furthermore, this technical solution can automatically adapt to satellite communication applications for various types of helicopters.

[0155] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An adaptive tracking method for rotor blockage fading in helicopter satellite communication, characterized in that, Includes the following steps: Step 1: Establish a mathematical model of rotor blockage in helicopter satellite communication; Step 2: Obtain the signal after rotor obstruction fading detected by the helicopter's airborne communication terminal, and add an anti-noise filter to improve the detection signal-to-noise ratio; Step 3: Generate a rotor blocking waveform based on the measured rotor blocking fading parameters, and perform coarse synchronization between the generated rotor blocking waveform and the detected rotor blocking waveform, as follows: Step 3.1: Measure the occlusion fading parameters, including the width and period of the occlusion fading; Step 3.2: Based on the measured parameters and the position of the blocking pulse, generate a local rotor blocking periodic pulse using a local periodic pulse generator according to the measured parameters, and generate a rotor blocking waveform. Step 3.3: Compare the generated rotor obstruction waveform with the detected rotor obstruction waveform, measure the phase, and adjust the phase of the generated signal to be basically aligned with the phase of the detected signal; Step 4: Compare the parameter errors between the rotor obstruction waveform generated by the local periodic pulse generator and the measured rotor obstruction waveform to obtain the error detection results, as follows: The error detection curve is obtained by correlating and summing the rotor blocking waveform generated by the local periodic pulse generator and the measured rotor blocking waveform. When the rotor blocking waveform generated by the local periodic pulse generator and the measured rotor blocking waveform slide relative to each other, the error of the correlation summation operation also changes accordingly, resulting in a typical error detection curve. The obtained error detection result also shows periodicity. Step 5: Use the error detection results to correct the period, phase, and width of the rotor blocking waveform generated by the local periodic pulse generator, thereby adaptively tracking changes in rotor blocking.

2. The adaptive tracking method for rotor obstruction fading in helicopter satellite communication according to claim 1, characterized in that, The mathematical model for rotor blockage in helicopter satellite communication established in step 1 is as follows: Step 1.1: Based on the rotor blocking process, from the rotor cutting into the satellite communication antenna from one side to blocking it and then cutting out from the other side, establish a Cartesian coordinate system and set the coordinates of the antenna center as follows: With the center of the rotor as the origin of the coordinate axis, and the angle between the rotor axis and the coordinate axis set as... ; Step 1.2: Set the radius of the airborne satellite antenna to... The width of the helicopter rotor is ,in During helicopter flight, the angle between the antenna and the satellite signal and the helicopter rotor is set to... Therefore, the equivalent width of the projection when the helicopter rotor blocks the antenna is calculated as follows: ； in, ; Set antenna center The distances to the two sides of the rotor are respectively and The distance from the side that first enters the antenna is The distance to the other side is First, enter the radius of the intersection point of the antenna edge and the radar circumference. The angle between the radii is The radius of the intersection point between the other side and the radar circumference is... The angle between the radii is ; Step 1.3: Calculate the six critical points: front side entering the radar, rear side entering the radar, front side reaching the center of the circle, rear side reaching the center of the circle, front side leaving the radar, and rear side leaving the radar. The specific calculation process for the value of is as follows: ： ； ： ； ： ； ： ； ： ； ： ； Step 1.4, according to The value of is used to divide the entire occlusion process into six segments, calculate the occlusion area of ​​each segment separately, and then synthesize the occlusion area S in the entire occlusion process. Theoretical formula for change: ； Each of them In the corresponding formula , , and The calculation formula is: when hour, , , and The calculation formula is: ； when hour, , , and The calculation formula is: ； when hour, , , and The calculation formula is: ； when hour, , , and The calculation formula is: ； when hour, , , and The calculation formula is: ； when hour, , , and The calculation formula is: 。 3. The adaptive tracking method for rotor obstruction fading in helicopter satellite communication according to claim 2, characterized in that, The transfer function of the noise immunity filter described in step 2 is: ； in, These are filter parameters, typically taking the values... .

4. The rotor blockage fading adaptive tracking method for helicopter satellite communication according to claim 3, characterized in that, Step 3.1 involves measuring the occlusion fading parameters, including the width and period of the occlusion fading, as detailed below: The detection threshold for channel fading is set to 0.85 of the average signal power. When the detected signal strength is below the threshold, it indicates channel signal fading. This yields a periodic channel fading pulse, and the average period and average pulse width of the pulse are measured.

5. The adaptive tracking method for rotor blockage fading in helicopter satellite communication according to claim 3, characterized in that, The measurement of occlusion fading parameters described in step 3.1 needs to be performed multiple times.

6. A rotor-blocking fading adaptive tracking device for helicopter satellite communication, characterized in that, The device is used to implement the rotor blockage fading adaptive tracking method for helicopter satellite communication as described in any one of claims 1 to 5, and the device includes first to fifth modules, wherein: The first module is used to establish a mathematical model of rotor blockage in helicopter satellite communication; The second module acquires the signal after rotor obstruction fading detected by the helicopter's airborne communication terminal, and adds an anti-noise filter to improve the detection signal-to-noise ratio. The third module generates a rotor blocking waveform based on the measured rotor blocking fading parameters, and performs coarse synchronization between the generated rotor blocking waveform and the detected rotor blocking waveform. The fourth module compares the parameter error between the rotor blocking waveform generated by the local periodic pulse generator and the measured rotor blocking waveform to obtain the error detection result; The fifth module uses the error detection results to correct the period, phase, and width of the rotor blocking waveform generated by the local periodic pulse generator, thereby adaptively tracking changes in rotor blocking.

7. A mobile terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the rotor fading adaptive tracking method for helicopter satellite communication as described in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the rotor occlusion fading adaptive tracking method for helicopter satellite communication as described in any one of claims 1 to 5.

Images