Multi-band multi-feed-source focus shifting device and method for GSO satellite parabolic antenna

Abstract

The invention discloses a multi-band multi-feed source focus shifting device and method for a GSO satellite parabolic antenna, and the device comprises a focus shifting fixed ring body which is provided with a plurality of feed sources, a transmission gear is engaged with an outer ring gear of the focus shifting fixed ring, and a control motor drives the focus shifting fixed ring to rotate through the transmission gear; wherein the ring surface of the focus-shifting fixing ring is perpendicular to the axial direction of the antenna, and when the feed source rotates along with the focus-shifting fixing ring, the center rotation path of the feed source passes through the focus of the antenna. According to the invention, through a mode of rotation control of the receiving feed source, measurement with highest gain at different frequency bands can be realized, measurement of ground weak electronic signals by a GSO satellite can be satisfied, results of non-specific targets, rapid discovery and positioning monitoring can be solved, and debugging of each frequency band and debugging of other frequency bands are ensured not to influence each other. The method has the advantages of rapidness, accuracy, convenience in assembly, easiness in expansion and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of GSO satellite antenna feed defocusing, and particularly relates to a multi-band multi-feed defocusing device and method for a GSO satellite parabolic antenna. Background Art

[0002] With the increase in the number of geostationary satellites, the fixed positions in the orbit are becoming fewer and fewer. Currently, the most widely adopted method internationally is to use a single antenna to receive signals from multiple satellites simultaneously, which is achieved by arranging multiple feeds at appropriate positions in the antenna feed. Currently, for foreign electronic reconnaissance series satellites, large-sized (greater than 100 meters) main reflector antennas are installed on the satellites (such as the antenna described in "Overview of the Structure of Large Spaceborne Electronic Reconnaissance Antennas", DOI: 10.19341 / j.cnki.issn.1009 - 0401.2006.04.011). Multiple feeds are installed on the antenna simultaneously to achieve the collection of weak signals and signals in a relatively wide frequency spectrum. The main method is that for a parabolic antenna, the signal beam is closely related to the position where the feed is located. The signal beam generated by the focal plane electric field is related to the operating frequency, focal length / diameter, and feed offset. Currently, for multi-feed receiving antennas, the generally adopted deployment method is to calculate the beam deflection angle when the antenna points to a specific satellite for a specific target, so as to obtain the offset of the feed from the focal point. That is, the offset of the feed deployment is calculated and fixedly installed at the focal plane of the main reflector. The advantage of this is stable signal reception and high antenna utilization rate.

[0003] The existing deficiencies are as follows: (1) The calculated offset is applicable to the communication between a ground station and a fixed target. Multiple feeds must be fixedly installed basically on the plane perpendicular to the antenna axis at the focal point. (2) Existing antenna technology research shows that if the feed deviates from the focal point, the directivity, sidelobe level, and efficiency of the antenna will decrease, which is suitable for small-aperture antennas. However, the space monitoring coverage for a large range of space-based, multi-band, and multi-targets is limited.

[0004] For GSO satellite antennas, the existing monitoring technology for ground and low-altitude electromagnetic wave signals obtains the signal level through the reflection of the main radiation surface, and selects and receives signals in a specific frequency band through the frequency selection function of the feed. At this time, multiple feeds are basically on the plane perpendicular to the antenna axis near the focal point. Although the signal beam is also strongly correlated with the position where the feed is located, the maximum gain of the antenna and its variation cannot be utilized, and only non-identified collection of signals is performed, and the approximate positioning of ground targets cannot be completed. Summary of the Invention

[0005] Aiming at the above problems, the purpose of the present invention is to provide a multi-band multi-feed defocusing device and method for a GSO satellite parabolic antenna, which realizes efficient scanning and monitoring of multi-band and multi-target signals by providing a multi-feed switching device at the antenna focus, receives the signal power in real time, and can quickly obtain the basic position of the target.

[0006] An embodiment of the present invention provides a multi-band multi-feed defocusing device and method for a GSO satellite parabolic antenna.

[0007] First aspect: A multi-band multi-feed defocusing device for a GSO satellite parabolic antenna, the device includes:

[0008] A plurality of feeds are installed on the defocusing fixed ring body, the driving gear meshes with the outer ring gear of the defocusing fixed ring, and the control motor drives the defocusing fixed ring to rotate through the driving gear;

[0009] Wherein, the plane of the defocusing fixed ring is perpendicular to the antenna axis, and when the feed follows the defocusing fixed ring to rotate, the rotation path center of the feed passes through the antenna focus.

[0010] Further, the plurality of feeds respectively adopt different frequency bands, and the frequency band range is 0.335G to 40G.

[0011] Further, the antenna aperture D≥100m.

[0012] Second aspect: A multi-band multi-feed defocusing method for a GSO satellite parabolic antenna, including the steps:

[0013] S1. Set a rotating feed within the maximum lateral offset range of the GSO satellite antenna feed;

[0014] S2. During the process of the feed rotating from the antenna focus position to the lateral off-axis position, analyze and calculate the included angle of the antenna pattern to obtain the position of the ground transmitter.

[0015] Further, the rotation path plane of the feed is perpendicular to the antenna axis, and the antenna focus is located on the rotation path center of the feed.

[0016] Further, during the rotation of the feed, monitor and obtain the maximum power value P point, and analyze and calculate the included angle of the antenna pattern based on the P point to obtain the position of the ground transmitter.

[0017] Further, the steps of obtaining the position of the ground transmitter by the included angle of the antenna pattern include:

[0018] S21. Obtain the parameters of the parabolic antenna, and calculate the axial maximum gain of the antenna considering the antenna efficiency factor. The formula is:

[0019]

[0020] Among them, G max is the maximum gain in the antenna axial direction, μ is the antenna efficiency factor, π is the ratio of the circumference of a circle to its diameter, λ is the operating wavelength, and D is the diameter of the parabolic antenna aperture.

[0021] For S22, use the first-order Bessel function to model the gain of the antenna at the focus and after defocusing, obtain the receiving pattern, and calculate the numerical values of each angle of the antenna pattern using the first-order Bessel function. The formula is:

[0022]

[0023] The formula for the gain pattern at the focus is expressed as:

[0024]

[0025] The formula for the gain pattern after defocusing is expressed as:

[0026] G(θ) = G max f(x) (4)

[0027] Among them, is the angle between the antenna patterns, J1(x) represents the first-order Bessel function with variable x, and f(x) is the function related to the off-axis angle after defocusing;

[0028] For S23, calculate the antenna received power P through the engineering experience formula of the International Telecommunication Union (ITU);

[0029]

[0030] P ≥ P th (6)

[0031] Among them, EIRP is the ground transmit power, P th is the threshold value monitored and received by the antenna, L u is the uplink loss, is the gain of the receiving antenna at a certain angle, and P is the received power of the satellite receiver;

[0032] Derive the satellite received power based on the antenna received power P. The formula is expressed as:

[0033]

[0034] Derive the satellite received power based on the antenna received power P. The formula is expressed as:

[0035] G(θ) = P' + L u -EIRP (8)

[0036] For S24, calculate the monitored off-axis angle at the focus according to formulas (7) and (3) Calculate the off-axis angle θ after defocusing according to formulas (8) and (4); obtain the off-axis angle For the two intersection points between the boundary and the off-axis angle θ boundary, calculate the longitude and latitude of the two intersection points through reverse calculation;

[0037] S25. Combine the maximum power value monitored during the defocusing process to determine the position of the emission source, exclude false emission intersection points, and obtain the target approximate position.

[0038] Advantages of the present invention:

[0039] The present invention provides a method for completing the switching of receiving feeds in different frequency bands by controlling the rotation of the receiving feed, which can achieve the measurement with the highest gain in different frequency bands and meet the measurement of weak electronic signals on the ground by GSO satellites. Compared with the method of offset deployment of multiple feeds on the focal plane, it can solve the problem of non-specific targets, quickly discover and locate the monitoring results, and at the same time ensure that the debugging of each frequency band does not affect other frequency bands, having the advantages of fast speed, accuracy, convenient assembly, and easy expansion. Description of the drawings

[0040] Figure 1 It is a schematic structural diagram of the multi-band multi-feed defocusing device of the present invention;

[0041] Figure 2 It is a schematic overall installation diagram of the multi-band multi-feed defocusing device of the present invention;

[0042] Figure 3 It is a schematic flow diagram of the multi-band multi-feed defocusing method of the present invention;

[0043] Figure 4 It is a schematic diagram of the multi-band multi-feed defocusing and positioning principle of the present invention. Specific embodiments

[0044] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar symbols represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0045] For a parabolic antenna, defocusing will cause the electrical performance of the antenna to decline, but defocusing also has its utilizable aspects; defocusing is divided into two types: the phase center of the feed is defocused along the axis of the parabolic surface, which is called longitudinal defocusing; the phase center of the feed is defocused perpendicular to the axis of the parabolic surface, which is called transverse defocusing.

[0046] Longitudinal defocusing causes a rotationally symmetric phase shift on the parabolic aperture, widening the main lobe of the radiation pattern while keeping the maximum radiation direction unchanged, which is beneficial for target search. When in the normal focus state, the main lobe of the radiation pattern is narrow, which is beneficial for target tracking. Such a radar can be used for both search and tracking purposes simultaneously.

[0047] When there is small-sized lateral defocusing, a linear-phase shift occurs on the parabolic aperture, and the maximum radiation direction of the antenna deflects, but the beam shape remains almost unchanged. If the feed rotates around the axis of the parabolic reflector in a laterally defocused manner, the maximum radiation direction of the antenna will perform conical scanning in space, expanding the search space.

[0048] For the large-aperture electronic surveillance satellite antenna of a geostationary orbit (GSO) satellite, since it is far from the ground, signals on the ground can all be regarded as far-field signals. Therefore, it has a large size on the aperture to collect various signals on the ground. So for a large-aperture antenna, its feed is deployed on the focal plane around the antenna axis. There is no difference in the order of magnitude of the received signal intensity. However, due to the large aperture, the half-power angle of the antenna is very small. For example, in the GSO orbit, with a 100-meter aperture and an operating frequency band of 10 GHz, the coverage range of the sub-satellite point on the ground is only within a circular area with a diameter of about 11 kilometers.

[0049] Therefore, in the existing GSO satellite parabolic antennas, multiple feeds must be basically fixed and installed on a plane perpendicular to the antenna axis at the focus. If the feed deviates from the focus, the directivity, sidelobe level, and efficiency of the antenna will decrease, and the space monitoring coverage for a large range of space-based, multi-band, and multi-targets will be limited.

[0050] To address the above problems, the present invention provides a multi-band and multi-feed defocusing device for a GSO satellite parabolic antenna. Figure 1 FIG. [X] is a schematic structural diagram of the multi-band and multi-feed defocusing device for a GSO satellite parabolic antenna provided by an embodiment of the present invention. The device structure includes:

[0051] The entire mechanism includes receiving feeds (taking Figure 1 the four receiving feeds shown as an example), a defocusing fixing ring, and a control motor.

[0052] Receiving feeds: The receiving feeds of the parabolic antenna mainly include LNAs. Different LNAs can be used for different frequency bands. Multiple feeds use different frequency bands respectively. The feeds of the parabolic antenna cover a frequency band from 0.335 GHz to 40 GHz, which covers most of the frequencies used on the ground. A certain number of receiving feeds can be set according to the monitoring frequency band range, and the feed selection can be completed according to the characteristics of the antenna surface.

[0053] And a fixed ring for feed defocusing. Different-frequency receiving feeds can be installed on the toroidal surface of the defocusing fixed ring as needed. When the feed follows the rotation of the defocusing fixed ring, the rotation path of the feed center passes through the antenna focus. The antenna receiving feeds can be installed in place at equal division positions. The outer ring gear of the defocusing fixed ring meshes with the transmission gear driven by the control motor, and the control motor drives the defocusing fixed ring to rotate through the transmission gear.

[0054] The control motor rotates at a certain rate to make feeds of different channels reach the focus position. In this way, it can be ensured that the signals received by different feeds can utilize the maximum gain of the antenna, and there is no large obstruction to the antenna surface. For unspecified monitoring targets, the signal level can be efficiently collected, which is convenient for demodulation processing.

[0055] Such as Figure 2 shown, the entire structure (receiving feed, defocusing fixed ring, and control motor) is fixed on the GSO satellite parabolic antenna. The GSO satellite parabolic antenna is a single-reflector antenna. It uses an axially symmetric rotating paraboloid as the main reflector, places the feed at the focus of the paraboloid. When receiving, after being reflected by the reflector, the radio waves converge to the feed, and the feed can receive the maximum signal energy.

[0056] Based on the multi-feed defocusing device of the above multi-feed defocusing device, the present invention discloses a multi-band multi-feed defocusing method for a GSO satellite parabolic antenna. Such as Figure 3 shown, including the steps:

[0057] S1. Set a rotating feed within the maximum lateral offset range of the GSO satellite antenna feed.

[0058] S2. During the process of the feed rotating from the antenna focus position to the lateral off-axis position, analyze and calculate the included angle of the antenna pattern to obtain the position of the ground transmitter.

[0059] By using the multi-band multi-feed defocusing device of the present invention, the feed can be set according to the maximum lateral offset range of the feed. During the process of rotating the feed from the focus position to the lateral off-axis position, the maximum radiation direction of the antenna will change, so that the energy value at the receiving end will change. By analyzing and calculating the included angle between the received energy and the pattern, the position of the transmitter can be obtained. Such as Figure 4 shown.

[0060] In the figure, the large solid circle is the rear view of the antenna, the small solid circle is the rotation path of the feed center, and the cross center O is the focal point position of the antenna. The plane is divided into four quadrants with the O point as the center of the coordinate. Assume A is the emission source on the ground. When the feed is at the center, through calculation, it can be known that there is radiation in the range of the left dotted circle, but the position cannot be determined; O' is the position where the feed moves. Through calculation, it can be known that there is an emission source in the range of the right dotted circle. At this time, the two dotted circles will generate two intersection points A and a. During the rotation process, the maximum power value P point is monitored. Based on the P point, the included angle of the antenna pattern is analyzed and calculated, and then the quadrant where the target is located can be determined, and the position of the ground emission source can be obtained.

[0061] Specifically, based on the first-order Bessel function, establish the pattern function of the parabolic antenna, establish the antenna model, and conduct simulation calculations. The calculation method includes the following steps:

[0062] Construct a parabolic antenna, input the parameters of the antenna, including the aperture diameter of the antenna and the operating wavelength, and calculate the maximum axial gain of the antenna considering the antenna efficiency factor;

[0063]

[0064] Among them, μ is the antenna efficiency factor. Theoretically, the efficiency of each antenna is unique and unchanged, and its value range is 50% - 70%. π is the pi, λ is the operating wavelength, with the unit of meter, and D is the aperture diameter of the parabolic antenna, with the unit of meter.

[0065] Use the first-order Bessel function to model the antenna gain. For a parabolic antenna, the transmitting and receiving gains are the same at the same frequency, and thus the receiving pattern is obtained;

[0066]

[0067] Define the variable x, and establish the pattern function according to the first-order Bessel function to simplify the electric field direction gain, where J1(x) represents the first-order Bessel function with the variable x. The gain pattern at the focal point can be expressed as:

[0068]

[0069] The gain pattern after defocusing can be expressed as:

[0070] G(θ) = G max f(x) (4)

[0071] Among them, f(x) is the function related to the off-axis angle after defocusing.

[0072] Use the first-order Bessel function to calculate the numerical values of each angle of the antenna pattern, which is convenient for subsequent calculation to look up the off-axis angle in the table.

[0073] Set the EIRP value of the ground transmission source and set the threshold value P for antenna monitoring and reception th , calculate the antenna received power P through the engineering experience formula of the International Telecommunication Union (ITU);

[0074]

[0075] P ≥ P th (6)

[0076] where EIRP is the ground transmission power, L u is the uplink loss, is the gain of the receiving antenna at a certain angle, P is the received power of the satellite receiver. If the received power P is greater than the reception threshold P th , the signal from the ground transmission station can be received; otherwise, the signal from the ground transmission station cannot be received.

[0077] Thus, the calculation formula for the satellite received power is derived,

[0078]

[0079] Substitute this formula into formula (3), and the off-axis angle value of the transmission source can be derived

[0080] After calculating the off-axis angle monitored at the focus , based on the off-axis angle the boundary where the transmitter position on the ground is located can be determined ( Figure 4 the left virtual circle in);

[0081] Similarly, after defocusing, the satellite received power will change, and the calculation formula is

[0082] G(θ) = P' + L u - EIRP (8)

[0083] Calculate the off-axis angle θ monitored after defocusing according to formulas (8) and (4); based on the off-axis angle θ, the boundary where the transmitter position on the ground is located can be determined ( Figure 4 the right virtual circle in);

[0084] At Figure 4 find two intersection points A and a on the ground within the boundary shown, and obtain the longitude and latitude of the two points through reverse calculation;

[0085] Combine the maximum power value monitored during the defocusing process to determine the quadrant where the transmission source is located, exclude the false emission point a, and obtain the target approximate position.

[0086] Among them, the focus of the satellite antenna and the pattern after defocusing are obtained by query.

[0087] Application test data: By establishing the antenna aperture and operating frequency parameters, setting different receiver sensitivities, with a GSO orbital altitude of 36,000 km and an operating frequency of 6 GHz. From the simulation calculation results, the range areas of different transmitted powers of the ground station that can be received under different threshold levels can be obtained.

[0088] Table 1 Test parameters of a GSO satellite antenna with an antenna aperture of 10 m and a receiver threshold of -120 dBm

[0089]

[0090] As shown in Table 1, when the antenna aperture is 10 m and the operating frequency is 6 GHz, the maximum gain of the antenna is only 53.37, and the value is greater than the maximum gain of the antenna. Therefore, when the receiver threshold is -120 dBm, the received power of the ground station within 200 W cannot be monitored.

[0091] Table 2 Test parameters of a GSO satellite antenna with an antenna aperture of 100 m and a receiver threshold of -120 dBm

[0092]

[0093] As shown in Table 2, when the antenna aperture is adjusted to 100 m and the operating frequency is 6 GHz, the maximum gain of the antenna increases to 73.37 dB, and the value is within the detection range of the maximum gain of the antenna. Therefore, when the receiver threshold is -120 dBm, the received power of the ground station within 200 W can be monitored. And as the transmitted power of the ground increases, the detection range gradually increases. The detection area in the table is the circular diameter inclusion area centered on the sub-satellite point.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-band and multi-feed defocusing device for a GSO satellite parabolic antenna, characterized in that, The device includes: A plurality of feeds are installed on the body of the focus shifting fixed ring. The driving gear meshes with the outer ring gear of the focus shifting fixed ring, and the control motor drives the focus shifting fixed ring to rotate through the driving gear. Among them, the plane of the focus shifting fixed ring is perpendicular to the antenna axis. When the feed follows the rotation of the focus shifting fixed ring, the rotation path center of the feed passes through the antenna focus.

2. The multi-band multi-feed defocusing device according to claim 1, wherein The plurality of feeds respectively adopt different frequency bands, and the frequency band range is 0.335G to 40G.

3. The multi-band multi-feed defocusing device according to claim 1, characterized in that The antenna aperture D ≥ 100m.

4. A multi-feed defocusing method for the multi-feed defocusing device according to any one of claims 1 to 3, characterized in that It includes the steps: S1. Set a rotating feed within the maximum lateral offset range of the GSO satellite antenna feed. S2. During the process of the feed rotating from the antenna focus position to the lateral off-axis position, analyze and calculate the included angle of the antenna pattern to obtain the position of the ground emission source.

5. The multi-feed defocusing method according to claim 4, characterized in that The plane of the feed rotation path is perpendicular to the antenna axis, and the antenna focus is located on the rotation path center of the feed.

6. The multi-feed defocusing method according to claim 4, wherein During the rotation of the feed, monitor and obtain the maximum power value P point, and analyze and calculate the included angle of the antenna pattern based on the P point to obtain the position of the ground emission source.

7. The multi-feed defocusing method according to claim 6, wherein, For the included angle of the antenna pattern to obtain the position of the ground emission source, the steps include: S21. Obtain the parabolic antenna parameters, and calculate the axial maximum gain of the antenna considering the antenna efficiency factor. The formula is: Among them, G max is the maximum gain in the antenna axial direction, μ is the antenna efficiency factor, π is the pi, λ is the operating wavelength, and D is the diameter of the parabolic antenna aperture; S22. Use the first-order Bessel function to model the antenna focus and the gain after antenna focus shifting to obtain the receiving pattern, and use the first-order Bessel function to calculate the numerical values of each angle of the antenna pattern. The formula is: The formula for the gain pattern at the focus is expressed as: The formula for the gain pattern after focus shifting is expressed as: Among them, is the antenna pattern angle, J1(x) represents the first-order Bessel function with variable x, and f(x) is the function related to the off-axis angle after defocusing; S23. Calculate the antenna received power P through the engineering experience formula of the International Telecommunication Union (ITU). P≥P th (6) Among them, EIRP is the ground transmission power, P th is the threshold value monitored and received by the antenna, L u is the uplink loss, is the gain of the receiving antenna at a certain angle, and P is the receiving power of the satellite receiver; Derive the satellite received power based on the antenna received power P. The formula is expressed as: Derive the satellite received power based on the antenna received power P. The formula is expressed as: G(θ) = P' + L u -EIRP (8) S24. Calculate the off-axis angle monitored at the focus according to formulas (7) and (3). Calculate the off-axis angle θ monitored after defocusing according to formulas (8) and (4); obtain the off-axis angle For the two intersection points of the boundary and the off-axis angle θ boundary, calculate the longitude and latitude of the two intersection points through reverse calculation; S25. Combine the maximum power value monitored during the focus shifting process to determine the emission source position, exclude false emission intersection points, and obtain the target approximate position.

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