A general design method for micro-nano satellite SAR antenna

Abstract

An integrated design method for the size of a micro-nano satellite SAR antenna is provided. The method first determines the parameters required by a user design task, including range and azimuth resolution, observation band width, SAR working time, and image system sensitivity. The envelope constraints of the SAR antenna launch and on-orbit state are determined according to the type of carrier fairing and the provided launch net envelope. The satellite energy supply per orbit is calculated according to the satellite configuration, orbit characteristics, and user design task requirements. The minimum antenna area that meets the sensitivity index requirements is calculated according to the satellite energy constraint conditions. The minimum antenna area that meets the range and azimuth ambiguity constraint conditions and the antenna size range that meets the azimuth resolution and observation band width are calculated. Finally, the range and azimuth antenna sizes are obtained according to the user design task requirements, carrying capacity, satellite configuration, orbit characteristics, SAR image system sensitivity, ambiguity, azimuth resolution, and observation band width involved.

Description

Technical Field

[0001] The invention relates to an overall design method of a micro-nano satellite SAR antenna, and belongs to the field of micro-nano satellite SAR antenna design. Background Art

[0002] The weight of micro-nano SAR satellite is hundreds of kilograms and the envelope size is less than 1m. 3 , which puts forward high requirements for the overall design of satellites. The SAR antenna size design is an important factor restricting the weight, envelope and power consumption of micro-nano SAR satellites, which is mainly restricted by multi-faceted factors such as range azimuth ambiguity, azimuth resolution, and beam coverage. The current design ideas of SAR antennas are:

[0003] Determine the minimum antenna area based on the range-azimuth ambiguity; determine the azimuth antenna size based on the azimuth resolution; determine the range antenna size based on parameters such as beam coverage and beam width; determine the power consumption requirement of the SAR antenna for the satellite based on factors such as antenna area, image system sensitivity, antenna efficiency, and TR component efficiency.

[0004] The above design method designs the satellite system based on the SAR payload. It usually requires multiple rounds of iteration and optimization to confirm a result that is suitable for engineering practice and has the best comprehensive performance in all aspects. This makes the satellite development cycle longer, and the weight and size envelope of the final designed SAR antenna are larger, which cannot meet the short-cycle and lightweight requirements of micro-nano satellites.

[0005] Therefore, how to integrate the SAR payload antenna and the satellite platform and quickly design a lightweight SAR antenna size is the key problem to be solved by the present invention. Summary of the invention

[0006] The technical problem solved by the present invention is: in view of the problems in the current prior art that satellite system design based on SAR payload is mainly used, such as long satellite development cycle and large antenna weight and size, a method for integrated design of micro-nano satellite SAR antenna size is proposed.

[0007] The present invention solves the above technical problems by the following technical solutions:

[0008] A method for integrated design of micro-nano satellite SAR antenna size, the steps are as follows:

[0009] (1) Determine the parameters required by the user's design mission, including range and azimuth resolution, observation bandwidth, SAR operating time, and image system sensitivity;

[0010] (2) Determine the envelope constraints of the SAR antenna launch and on-orbit state based on the launch fairing type and the net launch envelope provided;

[0011] (3) Calculate the satellite energy supply per orbit based on the satellite configuration, orbit characteristics, and user design mission requirements;

[0012] (4) Calculate the minimum antenna area that meets the sensitivity index requirements based on the satellite energy constraints;

[0013] (5) Calculate the minimum antenna area that satisfies the range-azimuth ambiguity constraints and the antenna size range that satisfies the azimuth resolution and observation bandwidth;

[0014] (6) Obtain the range and azimuth antenna dimensions based on the user design mission requirements, carrying capacity, satellite configuration, orbit characteristics, SAR image system sensitivity, ambiguity, azimuth resolution, and observation band width involved in steps (1) to (5).

[0015] In the step (1), the range and azimuth resolution refers to the resolvable units of the SAR image in the range and azimuth directions, the observation band width refers to the observation range of the SAR image in the range direction, the SAR working time refers to the maximum time that each track of the SAR can be turned on, and the system sensitivity represents the image signal-to-noise ratio level.

[0016] In the step (2), the satellite carrying capacity is the maximum weight and maximum envelope size of the satellite that can be launched, the SAR antenna transmission envelope constraint is the envelope size of the SAR antenna after being folded before launching into orbit, and the envelope constraint of the SAR antenna in the on-orbit state is the envelope size of the SAR antenna after being unfolded after launching into orbit.

[0017] In step (3), the satellite configuration is the three-dimensional size of the satellite shape, the orbital characteristics are the duration, speed, sunlight duration, and shadow duration of the satellite's orbit, and the satellite's energy supply per orbit is the output power that the satellite can provide to the SAR antenna after one orbit.

[0018] In step (4), the minimum antenna area is the product of the antenna size in the range direction and the antenna size in the azimuth direction.

[0019] In step (5), the ambiguity is the ratio of the sum of the amplitudes of the antenna sidelobe signals entering the mainlobe signal to the amplitude of the mainlobe signal, and the antenna size range is the antenna length in the range and azimuth directions under the constraint conditions.

[0020] The advantages of the present invention compared with the prior art are:

[0021] (1) The present invention provides a method for integrated design of micro-nano satellite SAR antenna size, which adopts the idea of ​​integrated design of SAR payload antenna and satellite platform, performs mission analysis based on the user's application requirements, comprehensively considers satellite factors such as launch capability, orbit characteristics, satellite energy supply capability, micro-nano satellite weight and envelope, and payload factors such as range and azimuth ambiguity, image system sensitivity, azimuth resolution, beam coverage, and beam width, and calculates the range antenna size and azimuth antenna size, so that the SAR antenna area and micro-nano satellite system performance ratio are optimal;

[0022] (2) The present invention takes into account the capabilities of the micro-nano satellite platform when designing the SAR payload antenna parameters, and makes a compromise between antenna area and performance to determine a result that is easy to implement in engineering and has the best comprehensive performance in all aspects, which greatly reduces the iteration process in the overall process of the satellite system and significantly improves the design cost and development cycle of the satellite. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of the integrated design method for the size of micro-nano satellite SAR antenna provided for the invention;

[0024] Figure 2 A flow chart of user application requirements analysis provided for the invention;

[0025] Figure 3 A flow chart of a method for calculating the maximum power consumption of the SAR during each orbit operation time provided by the invention;

[0026] Figure 4 A flow chart for calculating the power consumption of the SAR antenna provided for the invention;

[0027] Figure 5 A flow chart of a method for calculating the minimum antenna area provided for the invention;

[0028] Figure 6 A flow chart of a method for calculating the minimum antenna area provided for the invention;

[0029] Figure 7 A flow chart of the SAR antenna size calculation method provided for the invention; DETAILED DESCRIPTION

[0030] A method for integrated design of micro-nano satellite SAR antenna size is proposed. The weight, envelope and energy supply capacity of the micro-nano satellite are used as constraints. The range and azimuth antenna sizes that meet performance indicators such as range and azimuth ambiguity, azimuth resolution, and beam coverage are analyzed to optimize the SAR antenna scale and satellite system performance ratio, thereby improving the efficiency of satellite system design. The specific steps of the method are as follows:

[0031] (1) Determine the parameters required by the user's design task, including range and azimuth resolution, observation band width, SAR operating time, and image system sensitivity; range and azimuth resolution refers to the resolvable units of the SAR image in the range and azimuth directions, observation band width refers to the range of observation of the SAR image in the range direction, SAR operating time refers to the maximum time that the SAR can be turned on per track, and system sensitivity refers to the image signal-to-noise ratio level;

[0032] (2) Determine the envelope constraints of the SAR antenna launch and on-orbit state according to the launch fairing type and the provided launch net envelope; the satellite launch capacity is the maximum weight and maximum envelope size of the satellite that can be launched, the SAR antenna launch envelope constraint is the envelope size of the SAR antenna after being folded before launching into orbit, and the SAR antenna on-orbit envelope constraint is the envelope size of the SAR antenna after being unfolded after launching into orbit;

[0033] (3) Calculate the satellite energy supply per orbit based on the satellite configuration, orbital characteristics, and user design mission requirements; the satellite configuration is the three-dimensional dimensions of the satellite shape, the orbital characteristics are the duration, speed, sunlight duration, and shadow duration of the satellite's orbit, and the satellite energy supply per orbit is the output power that the satellite can provide to the SAR antenna after one orbit;

[0034] (4) Based on the satellite energy constraints, calculate the minimum antenna area that meets the sensitivity index requirements; the minimum antenna area is the product of the range antenna size and the azimuth antenna size;

[0035] (5) Calculate the minimum antenna area that satisfies the range and azimuth ambiguity constraints and the antenna size range that satisfies the azimuth resolution and observation bandwidth; the ambiguity is the ratio of the sum of the amplitudes of the antenna sidelobe signal entering the mainlobe signal to the amplitude of the mainlobe signal, and the antenna size range is the range and azimuth antenna lengths under the constraints;

[0036] (6) Obtain the range and azimuth antenna dimensions based on the user design mission requirements, carrying capacity, satellite configuration, orbit characteristics, SAR image system sensitivity, ambiguity, azimuth resolution, and observation band width involved in steps (1) to (5).

[0037] The following is further described based on specific embodiments:

[0038] First embodiment

[0039] The user application demand analysis flow chart provided in the first embodiment of the present invention is as follows: Figure 2 As shown, the processing steps include the following:

[0040] Step S11: Due to the large energy demand of SAR, the orbit height H is selected. orbit It is a sun-synchronous twilight circular orbit, ensuring the longest illumination time on the orbit.

[0041] Step S12, azimuth resolution ρ a It refers to the resolvable unit of the SAR image along the direction of satellite flight. The application scenarios of civil and commercial satellites include agriculture, forestry, urban construction, environmental protection, disaster reduction, etc. The azimuth resolution is usually selected as ρ a =3m.

[0042] Step S13, calculate the observation band width according to the SAR quality factor Q and azimuth resolution. The quality factor Q must satisfy

[0043]

[0044] where ρ a is the azimuth resolution, W i is the observation band width, V s is the satellite speed, θ i is the angle of incidence, and C is the speed of light.

[0045] Consider a certain redundancy coefficient coef 品质因子冗余系数 ,but

[0046] Step S14, assuming that the satellite observation coverage of each orbit is W g , then the SAR working time per orbit is T 工作时长 for:

[0047]

[0048] where ε 波位重叠度 is the wave position overlap, usually selected from 10% to 20%.

[0049] Step S15, select the SAR band and polarization mode, and obtain the backscatter coefficient σ of the ground target within a certain incident angle range. o , then the system sensitivity of the SAR image is

[0050]

[0051] Where SNR is the average signal-to-noise ratio of the signal.

[0052] Second embodiment

[0053] Embodiment 2 of the present invention determines the envelope constraint of the on-orbit state of the SAR antenna according to the launch capability of the carrier rocket and the deployment mode of the SAR antenna, and includes the following processing steps:

[0054] Step S21, select a launch vehicle to launch the satellite, and design the satellite body size to be L according to the launch envelope ben (X)×B ben (Y)×H ben(Z).

[0055] Step S22: When the SAR antenna is transmitting, the method of multiple folding along the azimuth direction is adopted to achieve a smaller transmission envelope. When the SAR antenna is folded N times along the satellite Z axis and the satellite Z axis size is H ben When , the azimuth antenna on-orbit flight size envelope is calculated as:

[0056] L a_运载 <N×H ben

[0057] Third embodiment

[0058] The flowchart of the method for calculating the maximum power consumption of each track of the SAR during the working time is provided in the third embodiment of the present invention. Figure 3 As shown, the processing steps include the following:

[0059] Step S3, analyzing and calculating the energy that the satellite can provide for each orbit based on the satellite energy supply and the SAR working time.

[0060] Step S31, perform orbit parameter analysis, and when the satellite orbit is a circular orbit, calculate the satellite orbit period T0 as:

[0061]

[0062] The longest shadow duration T of each track is obtained through STK simulation analysis 阴影时间 and the shortest light duration is T 阳照时间 , and T0=T 阴影时间 +T 阳照时间 .

[0063] Step S32: Analyze and obtain the maximum area of ​​the solar array as S square meters based on the satellite body size and the carrier envelope.

[0064] Step S33, calculating the number of solar cells in series and in parallel according to the area of ​​the solar cell array and the size of a single solar cell.

[0065] Step S331: According to the satellite platform power supply voltage standard, the voltage of the micro-nano satellite platform is V sat =32V; the voltage of a single solar cell is V 单片 , then the number of solar cells in series is:

[0066]

[0067] Step S332, calculate the number of solar cells in parallel:

[0068]

[0069] Where L is the length of a single solar cell, B is the width, and coef布片系数 is the cloth coefficient.

[0070] Step S34, calculate the maximum power consumption of each track SAR antenna during the working time according to the track sunshine time, SAR antenna working voltage, and SAR working time. The flow chart is as follows: Figure 4 As shown, the processing steps include the following:

[0071] Step S341, calculate the output power of each track of the solar array as:

[0072] P total =I 单片 ×V sat ×N 并联

[0073] Step S342, calculate the maximum chargeable power of each solar array track for the SAR antenna:

[0074]

[0075] Where P total is the output power of each track of the solar array; coef 分阵系数 The array coefficient for powering the SAR antenna is usually 0.16; U 充电 Charging voltage for SAR antenna; T 姿态机动 is the maneuvering time from satellite cruise to earth imaging; coef 光照效率 is the solar radiation efficiency during attitude maneuvering.

[0076] Step S343, calculating the maximum dischargeable power Q of each track of the SAR antenna 可放电 :

[0077]

[0078] Wherein, η is the load battery charge-discharge ratio, which is usually selected as 1.03.

[0079] Step S344, calculate the maximum power consumption P of each track of the SAR antenna SAR天线 :

[0080]

[0081] Fourth embodiment

[0082] The fourth embodiment of the present invention can provide a maximum power consumption P of the SAR antenna in each orbit of the satellite. SAR天线 、Image system sensitivity NEσ o , antenna efficiency η SAR天线 、TR module efficiency η TR , range resolution ρ rUnder the constraints of the radar equation, the minimum antenna area range A that meets the sensitivity index of the image system is calculated. min_NEσ 0Calculation method flow chart as follows Figure 5 As shown, the processing steps include the following:

[0083] Step S41, calculate the average transmission power P of the SAR antenna av :

[0084] P av =P SAR天线 ×η TR

[0085] Step S42, calculate the SAR antenna transmission gain G according to the radar equation:

[0086]

[0087] Where R is the slant distance between the target and the radar, V is the relative speed between the satellite and the target, k is the Boltzmann constant, T0 is the absolute temperature of the system, and F n is the system noise coefficient, k s is the system loss, M is the number of views, λ is the wavelength, P av is the average transmission power, ρ r is the distance resolution.

[0088] Step S43, calculate the system sensitivity NEσ o Minimum antenna area range A min_NEσ 0

[0089]

[0090] Fifth embodiment

[0091] Embodiment 5 of the present invention calculates the minimum antenna area A under the range and azimuth ambiguity constraint condition min_Amb ; Under the constraints of azimuth resolution, beam coverage and beam width, the flow chart of the method for calculating the range of antenna size and azimuth antenna size range is as follows: Figure 6 As shown, the processing steps include the following:

[0092] Step S51, calculate the minimum antenna area A that makes the radar signal completely unambiguous min_Amb :

[0093]

[0094] Step S52: Under the azimuth resolution constraint, calculate the azimuth antenna size L a :

[0095]

[0096] Among them, k s is the expansion coefficient, generally 1.2 is selected.

[0097] Step S53, under the constraints of beam coverage and beam width, the range of the antenna is calculated:

[0098]

[0099] Among them, θ f is the maximum incident angle, R f is the slant distance at the maximum angle of incidence.

[0100] Sixth embodiment

[0101] Embodiment 6 of the present invention combines the antenna area, range antenna size, and azimuth antenna size range obtained in steps S2, S4, and S5 to obtain a SAR antenna size that meets the requirements of a micro-nano satellite. The calculation method flow chart is as follows: Figure 7 As shown, the processing steps include the following:

[0102] Step S61, comprehensively consider the minimum antenna area A that makes the radar signal completely unambiguous min_Amb And satisfy the system sensitivity NEσ o Minimum antenna area range of the indicator Factors such as the minimum antenna area A are obtained. min for:

[0103]

[0104] Step S62, comprehensively considering factors such as the carrier envelope and azimuth resolution, and obtaining the azimuth antenna size L a for:

[0105] L a =min{L a_运载 ,L a_az}

[0106] Step S63: based on the minimum antenna area A min , calculate the distance to the antenna size constraint as:

[0107]

[0108] Step S64, comprehensively considering factors such as beam coverage, beam width and minimum antenna area, and obtaining the range antenna size L r for:

[0109]

[0110] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0111] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for integrated design of micro-nano satellite SAR antenna size, characterized in that Here are the steps: (1) Determine the parameters required by the user's design mission, including range and azimuth resolution, observation bandwidth, SAR operating time, and image system sensitivity; (2) Determine the envelope constraints of the SAR antenna launch and on-orbit state based on the launch fairing type and the net launch envelope provided; (3) Calculate the satellite energy supply per orbit based on the satellite configuration, orbit characteristics, and user design mission requirements; (4) Calculate the minimum antenna area that meets the sensitivity index requirements based on the satellite energy constraints; (5) Calculate the minimum antenna area that satisfies the range-azimuth ambiguity constraints and the antenna size range that satisfies the azimuth resolution and observation bandwidth; (6) Obtaining the range and azimuth antenna dimensions according to the user design mission requirements, carrying capacity, satellite configuration, orbit characteristics, SAR image system sensitivity, ambiguity, azimuth resolution, and observation band width involved in steps (1) to (5); Step S61, comprehensively consider the minimum antenna area A that makes the radar signal completely unambiguous min_Amb And satisfy the system sensitivity NEσ o Minimum antenna area range of the indicator Factor, get the minimum antenna area A min for: Step S62, comprehensively considering the carrier envelope and azimuth resolution factors, and obtaining the azimuth antenna size L a for: L a =min{L a_运载 ,L a_az } Where, L a_运载 ,L a_az They are respectively the size envelope of the azimuth antenna on-orbit and the size envelope of the azimuth antenna under the azimuth resolution constraint. Step S63: based on the minimum antenna area A min , calculate the distance to the antenna size constraint as: Step S64, comprehensively considering the beam coverage, beam width and minimum antenna area factors, and obtaining the range antenna size L r for: In the formula, They are: distance antenna range and distance antenna size constraint.

2. The method for integrated design of micro-nano satellite SAR antenna size according to claim 1, characterized in that: In the step (1), the range and azimuth resolution refers to the resolvable units of the SAR image in the range and azimuth directions, the observation band width refers to the observation range of the SAR image in the range direction, the SAR working time refers to the maximum time that each track of the SAR can be turned on, and the system sensitivity represents the image signal-to-noise ratio level.

3. The method for integrated design of micro-nano satellite SAR antenna size according to claim 2, characterized in that: In the step (2), the satellite carrying capacity is the maximum weight and maximum envelope size of the satellite that can be launched, the SAR antenna transmission envelope constraint is the envelope size of the SAR antenna after being folded before launching into orbit, and the envelope constraint of the SAR antenna in the on-orbit state is the envelope size of the SAR antenna after being unfolded after launching into orbit.

4. The method for integrated design of micro-nano satellite SAR antenna size according to claim 3, characterized in that: In step (3), the satellite configuration is the three-dimensional size of the satellite shape, the orbital characteristics are the duration, speed, sunlight duration, and shadow duration of the satellite's orbit, and the satellite's energy supply per orbit is the output power that the satellite can provide to the SAR antenna after one orbit.

5. The method for integrated design of micro-nano satellite SAR antenna size according to claim 4, characterized in that: In step (4), the minimum antenna area is the product of the antenna size in the range direction and the antenna size in the azimuth direction.

6. The method for integrated design of micro-nano satellite SAR antenna size according to claim 5, characterized in that: In step (5), the ambiguity is the ratio of the sum of the amplitudes of the antenna sidelobe signals entering the mainlobe signal to the amplitude of the mainlobe signal, and the antenna size range is the antenna length in the range and azimuth directions under the constraint conditions.

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