RU2124270C1 - System for satellite communication - Google Patents

Abstract

FIELD: antenna equipment. SUBSTANCE: on-board equipment of system has digital computer 1, receiving-transmitting transponder antenna 2, which are located on gyro-stabilized platform 3 which also carries system for additional stabilization of antenna beam pattern, which has n receiving antennas 4, where n= 3, 5, one of which is reference antenna which is located in center of circle which radius is

, where θ_r - is error of gyro-stabilization. n-1 receiving antennas are arranged along this circle and spaced by 1/4 of its length. In addition device has n input microwave amplifiers 6, frequency converters 7, local oscillator 8, n-1 channel commutator 9, phase meter 10. Ground station equipment comprises transmitter, which consists of serial circuit of microwave generator 11, power amplifier 12 and transmitting antenna 13. Outputs of receiving antennas 4 and 5 are connected through corresponding microwave amplifier 6 to input of corresponding frequency converter 7. Output of local oscillator 8 is connected to heterodyne inputs of frequency converters 7. Output of n-1 frequency converters are connected to corresponding inputs of n-1 channel commutator 9, which output is connected to measuring input of phase meter 10, which reference input is connected to output of frequency converter 7, which belongs to channel of reference antenna 5. Output of phase meter 10 and control input of n-1 channel commutator 9 are connected to computer 1. EFFECT: increased precision of additional three-dimensional stabilization of transponder beam pattern towards service region, decreased cost of satellite communication system, increased speed of its operations. 2 dwg

Description

 The invention relates to antenna technology and is intended to further stabilize the radiation pattern of the antenna system of a communication satellite located in a geostationary orbit.

 The trajectory of the motion of artificial Earth satellites / satellites / located in the geostationary orbit is determined by many factors. The most significant destabilizing factor is the action of the torque causing the rotation of the satellite. This leads to a deviation of the beam pattern / DN / antenna system of the satellite from the service area. The consequence of this is a disconnection or loss of information, which in some cases can have disastrous consequences.

 To eliminate this drawback, various devices are used to stabilize the spatial orientation of the satellite.

The most applicable is a gyroscopic stabilization system [1], consisting of a stabilized platform, a connected antenna, two gyroscopes, a gear, an engine. However, gyroscopic stabilization has an accuracy of the order of / 0.5 - 1.5 / ^o and is ineffective for highly directional antennas with a beam width of the order of 1 ^o or less.

 A multi-reflector antenna with a consistent radiation pattern [2] is also known, which makes it possible to irradiate precisely defined sections of the earth's surface. The antenna consists of a main reflector and at least one auxiliary reflector, while the active surfaces of the reflectors are deformed so that there is a correspondence with the region of the earth's surface with precisely defined boundaries due to the fulfillment of the Michuguch condition to eliminate crossed polarization. However, this system has low accuracy due to atmospheric effects on polarization properties.

 Closest to the technical nature of the claimed invention is a satellite communications system [3], designed to maintain the position of the DN radiation of the first signal emitted by the antenna of a satellite communications system located in geosynchronous orbit to cover a specific area on Earth in which ground stations are located. The second satellite antenna emits a beacon signal with an antenna beam that covers an area on Earth larger than a predetermined one and includes a predetermined area. Each of the ground stations located inside and around the periphery of the region receives the first and second signals and determines between the received beacon signal and the first signal in order to create a ground station signal proportional to this ratio. The signals of ground stations are compared with one another only for peripheral stations in order to determine the error in the position of the radiation pattern of the communication system relative to a given area. The position of the satellite is corrected by an error signal in the position of the diagram.

 However, such a system has insufficient accuracy of additional stabilization of the DN due to the influence of atmospheric influences (hail, rain), the sun, the use of such a system is very expensive, since it is a multi-position system, and the speed of this system is quite large.

 The aim of the invention is to increase the accuracy of the additional stabilization of the spatial direction of the beam of the transponder beam on the service area, the cost of a satellite communications system, as well as increasing its speed.

где θ_r - погрешность гироскопической стабилизации, ^o, а /n-1/ приемные антенны расположены по этой окружности с интервалом в 1/4 ее длины, n входных усилителей СВЧ, n преобразователей частоты, гетеродина, /n-1/канального коммутатора, фазометра, при этом выход каждой из n приемных антенн через соответствующий усилитель СВЧ соединен со входом соответствующего преобразователя частоты, а выход гетеродина соединен с гетеродинными входами n преобразователей частоты, выходы /n-1/ преобразователей частоты соединены с соответствующими входами /n-1/-канального коммутатора, выход которого соединен с измерительным входом фазометра, опорный вход которого соединен с выходом преобразователя частоты, находящегося в опорном канале, а выход фазометра и управляющий вход /n-1/-канального коммутатора соединены с БЦВМ.This goal is achieved by the fact that in a satellite communication system consisting of an onboard part, including an onboard computer / BTsVM / and transceiver antennas of the repeater located on the gyro-stabilized platform, and the ground part, the ground part is a transmitter consisting of a series-connected microwave generator, excited at a frequency corresponding to the wavelength λ, a power amplifier and a transmitting antenna, and an additional system is installed on the gyrostabilized platform of the repeater stabilization of the bottom of the repeater, consisting of n receiving antennas, where n = 3, 5, one of which, being the reference, is in the center of the circle with a radius

where θ _r is the error of gyroscopic stabilization, ^o , and / n-1 / receiving antennas are located on this circle with an interval of 1/4 of its length, n microwave input amplifiers, n frequency converters, local oscillator, / n-1 / channel switch, a phase meter, with the output of each of the n receiving antennas through a corresponding microwave amplifier connected to the input of the corresponding frequency converter, and the local oscillator output connected to the heterodyne inputs of n frequency converters, the outputs of / n-1 / frequency converters are connected to the corresponding inputs / n-1 / - channel second switch, whose output is connected to a measuring input of the phase meter, the reference input of which is connected to the output of the frequency converter, located in the reference channel, and an output and a control input of the phase meter / n-1 / -channel switch connected to the onboard computer.

 Figure 1 presents the structural diagram of the proposed satellite communications system.

 Figure 2 shows the location of the plane of the platform of the repeater before and after the destabilizing rotation.

 The satellite communication system consists of an onboard part, including a digital computer 1, transceiver antennas of the repeater 2, located on the hydrostabilized platform 3, which also houses the additional stabilization system of the transponder DN, consisting of receiving antennas 4,5, input microwave amplifiers 6, frequency converters 7, a local oscillator 8, a four-channel switch 9, a phase meter 10. The ground part is a transmitting station, consisting of a microwave generator 11, a power amplifier 12 and a transmitting antenna 13.

 The system operates as follows.

 The BTSVM 1, controlling a four-channel switch 9, connects the signals of the receiving antennas 4 located on a circle with a radius d at a distance of 1/4 of the circumference of each other / to be called reference antennas / at the center of this circle receiving antenna 5, measures the phases of these signals relative to the signal of the reference receiving antenna 5, and based on these measurements, adjusts the plane of the platform 3 to the plane of the phase signal of the ground transmitting antenna 13.

 Consider the mechanism for restoring the parameters of the axis of the electromagnetic wave destabilizing from measurements of the phase of the electromagnetic wave from the reference antennas 4 caused by this rotation.

 As a rule, gyrostabilized platforms are located from a satellite in a plane perpendicular to the direction to the Earth. With destabilizing influences causing the rotation of the satellite around an axis located in the plane of the platform, the largest displacement of the transponder beam from the service area occurs. This explains the choice of the location of the additional stabilization system on board the satellite.

 As mentioned above, the system of additional DN stabilization should be located in a plane normal to the direction to the Earth / to the ground station /. The service area to which the satellite relay beam is directed may not coincide with the location of the ground station. It is important that the associated errors in directing the beam of the beam to the service area are small and acceptable.

 Figure 2 shows the spatial location of the platform of the relay 3 before and after the destabilizing rotation.

так, что ее центр 0 расположен в центре масс ИСЗ /опорная антенна 5/. Ось

направим на первую реперную антенну, ось

на вторую /нормальную к первой/. Тогда направление на наземную станцию будет определяться единичным вектором

а направление луча ДН - единичным вектором

Координаты реперных антенн в СК 0

где d_x, d_y-расстояние от опорной антенны к реперным антеннам.We associate with the initial orientation of the receiving antennas 4.5 the right Cartesian rectangular coordinate system / SK /

so that its center 0 is located in the center of mass of the satellite / reference antenna 5 /. Axis

we direct to the first reference antenna, the axis

to the second / normal to the first /. Then the direction to the ground station will be determined by a unit vector

and the direction of the beam of the beam is a unit vector

Coordinates of reference antennas in SK 0

where d _x , d _{y is the} distance from the reference antenna to the reference antennas.

на направление

соотношением

где φ - фаза электромагнитной волны;
λ - длина волны.The measured phase of the electromagnetic wave is rigidly connected with the projection of the location of the reference antennas

to direction

the ratio

where φ is the phase of the electromagnetic wave;
λ is the wavelength.

) нужна на тот случай, если антенна опорного канала 5 находится не в центре масс ИСЗ. Тогда при вращениях ИСЗ она также будет претерпевать пространственные перемещения, и изменения проекций двух противоположных реперных антенн, связанные с этим вращением, будут различными. Учесть это явление в первом приближении /для малых смещений опорной антенны от центра масс ИСЗ/ можно простым вычислением среднего арифметического 2-х изменений проекций реперных антенн, расположенных на одной диагонали на направлении

Поэтому, не ограничивая общности, дальнейшие вычисления будем производить только для двух реперных антенн

Для проекций векторов

на направление

получим:

Под действием дестабилизирующего поворота на угол θ вокруг оси, определяемой в СК

единичным вектором

, произойдет изменение ориентации векторов реперных антенн

Изменятся и проекции векторов

на направление n_c, которые примут значение

Фазометр зафиксирует изменение этих проекций относительно первоначальных значений

Ограничиваясь членами нулевого и первого порядка малости по параметру θ (ввиду малости угла поворота θ), получим

Система уравнений /7/ численно неразрешима. Поэтому, восстанавливая параметры оси дестабилизирующего вращения, примем методическое допущение, что ось вращения находится в плоскости расположения приемных антенн 4,5:

Тогда, представляя /8/ в /7/ и производя необходимые вычисления, получим систему уравнений

Отсюда следуют расчетные формулы:

Итак, в предположении, что ось вращения находится в плоскости платформы 3 /COS

= 0/ формулы /10/, находим ее параметры: единичный вектор, определяющий направление оси

и угол - θ , на который нужно повернуть платформу для того, чтобы вернуть ее в первоначальное положение
Общая погрешность системы стабилизации складывается из методической и аппаратной погрешности, включающей в себя погрешность измерительных приборов.Therefore, in all further calculations we will operate only with projections ΔR _i .
We also note that the apparent redundancy of the number of reference points (for unambiguous determination of the orientation of the plane, a sufficient reference, and two reference antennas

) is needed in case the antenna of the reference channel 5 is not in the center of mass of the satellite. Then, during the rotation of the satellite, it will also undergo spatial displacements, and the changes in the projections of the two opposite reference antennas associated with this rotation will be different. To take this phenomenon into a first approximation / for small displacements of the reference antenna from the center of mass of the satellite / it is possible to simply calculate the arithmetic average of 2 changes in the projections of the reference antennas located on the same diagonal in the direction

Therefore, without loss of generality, further calculations will be performed only for two reference antennas

For vector projections

to direction

we get:

Under the influence of a destabilizing rotation through an angle θ around an axis defined in the SK

unit vector

will change the orientation of the vectors of the reference antennas

Change and projection vectors

in the direction n _c , which will take the value

The phasometer will record the change in these projections relative to the initial values

Restricting ourselves to terms of zero and first order of smallness with respect to the parameter θ (due to the small angle of rotation θ), we obtain

The system of equations / 7 / is numerically insoluble. Therefore, restoring the parameters of the axis of the destabilizing rotation, we accept the methodological assumption that the rotation axis is in the plane of the receiving antennas 4,5:

Then, introducing / 8 / in / 7 / and making the necessary calculations, we obtain the system of equations

Hence the calculated formulas follow:

So, under the assumption that the axis of rotation is in the plane of the 3 / COS platform

= 0 / of the formula / 10 /, we find its parameters: a unit vector that determines the direction of the axis

and the angle - θ, on which you need to rotate the platform in order to return it to its original position
The total error of the stabilization system consists of a methodological and hardware error, which includes the error of the measuring instruments.

луча ДН ретранслятора ИСЗ и его направлением n_л после дестабилизирующего вращения вокруг оси

на угол θ и восстанавливающим поворотом оси

на угол - θ^x, произведенным по расчетным формулам /10/. Методическая погрешность зависит от взаимного расположения векторов

где

единичный вектор, задающий ориентацию антенной системы стабилизации, нормальный к плоскости расположения системы дополнительной стабилизации. Еще точнее от величин

и

(т.к.

по условию) в большей степени и от других сочетаний этих векторов в гораздо меньшей степени.By methodological error we mean the value of the angle between the initial direction of an arbitrary unit vector

the beam of the AES repeater's beam and its direction n _l after destabilizing rotation around the axis

angle θ and restoring rotation of the axis

angle θ ^x produced by the calculation formulas / 10 /. The methodological error depends on the relative position of the vectors

Where

a unit vector defining the orientation of the antenna stabilization system normal to the plane of the location of the additional stabilization system. More precisely from the values

and

(since

by assumption) to a greater extent and from other combinations of these vectors to a much lesser extent.

расположенной в плоскости системы дополнительной стабилизации. Последний вывод не является неожиданностью, так как при решении задачи использовалось методическое допущение, что ось вращения лежит в плоскости системы стабилизации, а значит именно такие вращения данная методика отрабатывает лучше всего, с минимальной, практически нулевой методической погрешностью. Максимальная погрешность соответствует дестабилизирующим вращениям при

т.е. когда ось вращения направлена на наземную станцию В качестве методической погрешности следует принять ее максимальное значение при

При этом направление луча ДН ИСЗ будет определяться выражением

а погрешность стабилизации - выражением /12/

Формула определяет максимальное значение методической погрешности в зависимости от угла между векторами

Так, если предположить, что этот угол равен 6^o /зона на Земле с радиусом примерно 4 тыс.км с центром в точке расположения наземной станции/, методическая погрешность не превышает величины, составляющей 0,1 от величины составляющей угла дестабилизирующего вращения, которая полностью определяется гироскопической системой стабилизации.Thus, the error in stabilizing the direction of the beam of the AES DN beam is minimal in the direction of the beam to the ground station, the minimum methodological error corresponds to rotations around the axis

located in the plane of the additional stabilization system. The last conclusion is not unexpected, since in solving the problem, the methodological assumption was used that the axis of rotation lies in the plane of the stabilization system, which means that this methodology fulfills such rotations best, with a minimal, practically zero methodological error. The maximum error corresponds to destabilizing rotations at

those. when the rotation axis is directed to the ground station As its methodological error, its maximum value should be taken at

In this case, the beam direction of the satellite AES beam will be determined by the expression

and the stabilization error is expressed by the expression / 12 /

The formula determines the maximum value of the methodological error depending on the angle between the vectors

So, if we assume that this angle is 6 ^o / zone on Earth with a radius of about 4 thousand km centered at the location of the ground station /, the methodological error does not exceed a value of 0.1 of the magnitude of the component of the angle of destabilizing rotation, which is completely determined by the gyroscopic stabilization system.

 Thus, the proposed stabilization system for the direction of the beam of the DN of the satellite repeater allows an order of magnitude to increase the accuracy of any gyroscopic stabilization system existing and installed on the satellite.

 The hardware error is insignificant in comparison with the methodological one; it imposes only certain requirements on the main elements of the stabilization system.

где K = 2π/λ,
λ - длина волны электромагнитного излучения;
d_x - радиус окружности, в центре которой находится опорная приемная антенна 5;
δφ - погрешность измерения фазы наземной станции.The hardware error is mainly determined by the phase measurement error. To connect the error in stabilizing the direction of the DN of the satellite repeater with the error in measuring the phase with phase meter 10 can be as follows. Methodically, the return of the MD beam is carried out by rotation around an axis located in the plane of the stabilization system according to the formulas / 10 /, whence we obtain by simple differentiation in the approximation of small

where K = 2π / λ,
λ is the wavelength of electromagnetic radiation;
d _x is the radius of the circle in the center of which is the reference receiving antenna 5;
δφ is the measurement error of the phase of the ground station.

Expression / 13 / shows that the hardware error of the reconstruction of the beam of the beam in Kd _x times less than the error of the phase meter. However, the linear dimensions of the receiving antenna system cannot be made arbitrarily large, because with a destabilizing rotation, the incursion of the phase of the electromagnetic wave from the reference antennas 4 caused by this rotation can go beyond the range of ± 180 ^o , which will lead to catastrophic consequences.

Подставляя /14/ в /12/, найдем

Выражение /15/ дает максимальную оценку погрешности стабилизации луча ДН в зависимости от ошибки измерения фазы фазометром. Ее можно уменьшить, увеличивая фазовый радиус окружности расположения приемных антенн 4. Но даже эта максимальная оценка не накладывает жестких условий на точность измерения фазы фазометром 10. Так, если положить, что погрешность фазометра составляет 2^o (δθ≢2^o), то выражение /15/ показывает, что связанная с этим погрешность стабилизации направления луча ДН ретранслятора δθ на два порядка меньше гироскопической погрешности θ_r, а значит ею можно пренебречь по сравнению с методической погрешностью.A reasonable choice of the minimum radius of the circle on which the reference antennas 4 are located is determined by the fact that the phase incursion from the reference antennas should not be less than 180 ^o when the satellite orientation changes within the gyroscopic error ± θ _r . I.e

Substituting / 14 / in / 12 /, we find

Expression / 15 / gives the maximum estimate of the error of stabilization of the beam of the beam depending on the error of phase measurement by a phase meter. It can be reduced by increasing the phase radius of the circumference of the location of the receiving antennas 4. But even this maximum estimate does not impose stringent conditions on the accuracy of the phase measurement by the phase meter 10. So, if we assume that the error of the phase meter is 2 ^o (δθ≢2 ^o ), then the expression / 15 / shows that the associated error in stabilizing the direction of the beam of the DN of the transponder δθ is two orders of magnitude smaller than the gyroscopic error θ _r , which means that it can be neglected in comparison with the methodological error.

 The speed of the stabilization system in the satellite communication system described in the prototype is generally determined by the response time of the measuring system of ground stations and the time of receipt and issuance of a control command on board the satellite via a command radio link. The speed of the proposed stabilization system will be determined by the response time of the measuring system located on board the satellite.

Thus, the proposed satellite communications system has the following advantages:
- command radio links are not involved;
- higher system performance, which follows from previous conclusions, which means that the restriction imposed on the value of the destabilizing torque is improved;
- the low cost of the ground-based transmitting station allows it to be located in each service area, thereby minimizing the error in stabilizing the beam direction to the service area;
- a decrease in the consumption of energy resources onboard the satellite, since the additional stabilization system works on reception, and not on the emission of large signal powers;
- there is no interruption in the stabilization system when the satellite passes through the solar disk;
- autonomy of the system. Of external systems, only a transmitting ground station is required, which is actually a beacon.

Sources of information:
1. H 01 Q 1/18, EPO application N 0209216, 1987

 2. H 01 Q 21/34, French application N 2577074, 1987

 3. H 01 Q 3/00, US patent N 4630058, 1986

Claims (1)

Satellite communication system, consisting of an onboard part, including an onboard digital computer (BCM) and transceiver antennas of a repeater located on a gyro-stabilized platform, and a terrestrial part, consisting of a microwave transmitter with a transmitting antenna connected to it, emitting a signal at a frequency corresponding to the wavelength λ, characterized in that on the gyrostabilized platform of the repeater installed system of additional stabilization of the radiation pattern of the repeater, consisting of n receiving x antennas, where n = 3.5, one of which, being a reference, is located in the center of a circle with a radius

where θ _{r the} error of gyroscopic stabilization,
and (n - 1) antennas are located along this circle with an interval of 1/4 of its length, n microwave input amplifiers, n frequency converters, local oscillator, a switch with (n - 1) inputs and one output, a phase meter, while the output of each of the receiving antennas through an appropriate microwave amplifier is connected to the input of the corresponding frequency converter, and the local oscillator output is connected to the heterodyne inputs of the frequency converters, the outputs (n - 1) of the frequency converters are connected to the corresponding (n - 1) inputs of the switch, the output of which is connected to the measuring input a phase meter house, the reference input of which is connected to the output of the frequency converter located in the reference channel, and the phase meter output and the control input of the switch are connected to the digital computer, designed to connect the receiving antennas to the measurement input of the phase meter of the signal, measure the phases of these signals by means of the phase meter and adjusting the plane of the phase front of the signals of the ground transmitting antenna based on these measurements.

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