CN113285224B - A method for avoiding strong electromagnetic interference in the far-field region of a radio telescope - Google Patents

Abstract

The invention provides a method for avoiding strong electromagnetic interference in a far field area of a radio telescope, which comprises the following steps: determining parameter information of a strong electromagnetic interference source and a radio telescope; measuring the frequency spectrum of a ground interference source at the focus of the radio telescope and determining the position of the ground interference source; determining an antenna directional pattern binary array of the radio telescope at the central frequency of the strong electromagnetic interference source; determining the gain of a strong electromagnetic and ground interference source entering a receiving system of the radio telescope when the radio telescope points to the strong electromagnetic interference source; determining the total power at the focus of the radio telescope; determining the input end power of an intermediate frequency amplifier of a receiver according to the total power and the parameter information of the radio telescope; and determining an avoiding angle of the strong electromagnetic interference source. According to the electromagnetic interference avoiding method provided by the invention, the influence on the radio telescope is reduced by determining the avoiding angle of a strong electromagnetic interference source, so that the strong electromagnetic interference is avoided, and the observed data quality and the observed efficiency are improved.

Description

A method for avoiding strong electromagnetic interference in the far-field region of a radio telescope

technical field

The invention relates to the technical field of radio astronomy, in particular to a method for avoiding strong electromagnetic interference in the far-field region of a radio telescope.

Background technique

Radio telescopes have extremely high system sensitivity. With the development of space radio technology, there is a strong electromagnetic interference source around the radio astronomy site or space, which causes the radio telescope receiver to fail to work normally. When the telescope is pointed to the strong electromagnetic interference, the strong interference causes the intermediate frequency amplifier in the telescope receiver to be in a nonlinear state, so that the observation data is invalid.

At present, there is no relevant method for avoiding strong electromagnetic interference in the field of radio astronomy technology.

Therefore, in order to improve the quality and efficiency of the observation data of radio telescopes, it is necessary to focus on the strong electromagnetic interference sources that lead to the saturation of the receiving system of the radio telescopes, and combine the receiving characteristics of the telescopes to study the avoidance methods of electromagnetic interference, and apply them to actual observations, so as to improve the large-scale radio telescopes. scientific output.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for avoiding strong electromagnetic interference in the far field area of a radio telescope, so as to avoid the strong electromagnetic interference and improve the data quality and observation efficiency of observation.

In order to achieve the above object, the present invention provides a method for avoiding strong electromagnetic interference in the far-field region of a radio telescope, including:

S1: Determine the parameter information of a strong electromagnetic interference source in the far-field region of the radio telescope;

S2: Determine the parameter information of the radio telescope;

S3: At the focal point of the radio telescope, measure the spectrum of the ground interference source and determine the location of the ground interference source;

以确定在干扰源处于各个方向时所分别对应的增益；G[m]为天线增益向量，

为干扰源所在方向偏离射电望远镜的主波束轴的角度向量，m为数组中的向量序数；S4: Determine the two-digit array of the antenna pattern of the radio telescope at the center frequency f _M of the strong electromagnetic interference source

to determine the corresponding gain when the interference source is in each direction; G[m] is the antenna gain vector,

is the angle vector of the direction of the interference source deviating from the main beam axis of the radio telescope, and m is the vector ordinal number in the array;

S5: Determine the gain of the receiving system that the strong electromagnetic interference source and the ground interference source enter the radio telescope when the radio telescope points to the strong electromagnetic interference source;

S6: Determine the power of the signal from the strong electromagnetic interference source and the ground interference source reaching the focus of the radio telescope;

S7: Determine the total power at the focus of the radio telescope;

S8: Determine the input power of the intermediate frequency amplifier of the receiver of the radio telescope according to the total power at the focal point of the radio telescope and the parameter information of the radio telescope;

S9: Determine the avoidance angle of the strong electromagnetic interference source.

S10: Make the main beam axis of the parabolic antenna of the radio telescope deviate from the strong electromagnetic interference angle by at least the avoidance angle

In the step S1, the parameter information of the strong electromagnetic interference source includes the operating frequency F ₁ , the power P _T , the polarization mode and the position of the signal; in the step S2, the parameter information of the radio telescope includes The position of the focal point of the radio telescope, the operating frequency F ₂ of its receiver's IF amplifier, its receiver's feed gain G _Feed , its receiver's low-noise amplifier gain G _LNA , and its receiver's feed to IF Other link losses between amplifiers, G _Loss .

The step S3 includes:

S31: According to the polarization mode and position of the signal of the strong electromagnetic interference source, set the polarization mode and direction of the measurement antenna located at the focus of the radio telescope;

作为地面干扰源的频谱，F[n]为频率点，P[n]为频率点对应的功率值，n为频率点的序数；S32: Take the operating frequency F ₂ of the intermediate frequency amplifier as the measurement frequency band to measure, and obtain

As the spectrum of the ground interference source, F[n] is the frequency point, P[n] is the power value corresponding to the frequency point, and n is the ordinal number of the frequency point;

S33: Determine the source and location of the strongest ground interference in the spectrum according to the frequency spectrum of the ground interference source and in combination with radio frequency division, and use it as the location of the ground interference source.

是采用仿真软件建立射电望远镜的抛物面天线模型，来仿真确定的。In the step S4, the two-digit array of the antenna pattern

It is determined by simulation software to establish the parabolic antenna model of the radio telescope.

In the step S5, when the radio telescope points to the strong electromagnetic interference source, the gain G _T of the strong electromagnetic interference source entering the receiving system of the radio telescope is:

G _T =max(G(m)),

中的天线增益向量G[m]；Among them, G(m) is the two-digit array of the antenna pattern

Antenna gain vector G[m] in ;

When the radio telescope points to a strong electromagnetic interference source, the gain G _T' of the ground interference source entering the receiving system of the radio telescope is:

H=Alt _A -Alt _B -,

为地面干扰源的电磁波方向偏离主波束轴的角度；x＝Lat_A；y＝Lat_B；z＝Lon_B-Lon_A，Lon_A、Lat_A、Alt_A分别表示强电磁干扰源的经度、纬度和海拔，Lon_B、Lat_B、Alt_B分别表示射电望远镜的焦点处的经度、纬度和海拔；h为地球半径；θ、θ′分别为强电磁干扰源、地面干扰源与水平面的夹角。In the formula, H and H′ are the vertical distances from the strong electromagnetic interference source and the ground interference source to the focus of the radio telescope, respectively; L and L′ are the projections from the strong electromagnetic interference source and the ground interference source to the focus of the radio telescope and the ground projection. Horizontal distance;

is the angle that the electromagnetic wave direction of the ground interference source deviates from the main beam axis; x=Lat _A ; y=Lat _B ; z=Lon _B -Lon _A , Lon _A , Lat _A , Alt _A represent the longitude and latitude of the strong electromagnetic interference source respectively and altitude, Lon _B , Lat _B , and Alt _B represent the longitude, latitude, and altitude of the focal point of the radio telescope, respectively; h is the radius of the earth;

In the step S6, determine the power P _RT at which the signal of the strong electromagnetic interference source reaches the focal point of the radio telescope, including:

S61: Determine the propagation loss P _Loss at the focal point of the radio telescope when the signal of the strong electromagnetic interference source is transmitted;

S62: When the radio telescope is pointed to the strong electromagnetic interference source, the influence of the gain GT of the strong electromagnetic interference source entering the receiving system of the radio telescope is considered to determine the power P _RT at which the signal of the strong electromagnetic interference source reaches the focus of the radio telescope;

Determine the power P _Rg of the terrestrial interferer reaching the focal point of the radio telescope, including:

S61': According to the spectrum of the ground interference source, determine the ungained power P _g of the signal from the ground interference source at the focus;

S62': Consider the influence of the gain G _T' of the ground interference source entering the receiving system of the radio telescope when the radio telescope is pointed to the strong electromagnetic interference source, to determine the power P _Rg of the signal of the ground interference source reaching the focus of the radio telescope.

In the step S7, the total power P at the focus of the radio telescope is:

Among them, f _T1 and f _T2 are the starting and ending frequencies of the strong electromagnetic interference source, f _R1 and f _R2 are the starting and ending frequencies of the working frequency of the intermediate frequency amplifier, and P _RT is the signal of the strong electromagnetic interference source reaching the radio telescope The power at the focal point of , P _Rg is the power of the signal of the ground interference source reaching the focal point of the radio telescope;

In the step S8, the input power P _Z of the intermediate frequency amplifier of the receiver of the radio telescope is:

P _Z =P+G _Feed +G _LNA -G _Loss ,

Among them, P is the total power at the focal point of the radio telescope, G _Feed is the feed gain of the receiver of the radio telescope, and G _Loss is the other link losses between the feed of the receiver of the radio telescope and the intermediate frequency amplifier.

The step S9 includes:

S91: Determine the gain reduction G ₁ of the parabolic antenna of the radio telescope;

The gain reduction G ₁ of the parabolic antenna of the radio telescope is:

G ₁ =P _Z -P _1dB +S,

In the formula, P _Z is the input power of the intermediate frequency amplifier of the receiver of the radio telescope, P _1dB is the power corresponding to the 1dB compression point of the intermediate frequency amplifier of the receiver, the unit is dBm; S is the safety margin;

确定在强电磁干扰源进入射电望远镜的接收系统的增益G_T减少所述减少量G₁得到的规避增益所对应的规避角度

S92: According to the two-digit array of the antenna pattern in the step S4

Determine the avoidance angle corresponding to the avoidance gain obtained by reducing the gain G _{T of} the receiving system of the radio telescope when the source of strong electromagnetic interference enters the radio telescope

为：the avoidance angle

for:

为天线增益向量G[m]为G[N]时天线方向图二位数组中求解得到的干扰源所在方向偏离射电望远镜的主波束轴的角度向量。Among them, G is the avoidance gain; G[N] is the antenna gain vector with the gain value found in the two-digit array of the antenna pattern as the avoidance gain G, and N is when the antenna gain vector G[m] is G[N] The vector ordinal in the array obtained by solving the two-digit array of the antenna pattern, which is a one-dimensional vector;

is the angle vector of the direction of the interference source deviating from the main beam axis of the radio telescope obtained by solving the two-digit array of the antenna pattern when the antenna gain vector G[m] is G[N].

The number of the strong electromagnetic interference sources is one or more.

When the number of strong electromagnetic interference sources is multiple, in the step S10, steps S1-S9 are repeated before the main beam axis of the parabolic antenna of the radio telescope is deviated to determine the avoidance angle of each strong electromagnetic interference source, The main beam axis of the parabolic antenna of the radio telescope is deviated from each strong electromagnetic interference angle by at least the avoidance angle corresponding to the strong electromagnetic interference source.

Therefore, in the electromagnetic interference avoidance method proposed by the present invention, by determining the avoidance angle of the strong electromagnetic interference source, the main beam axis of the parabolic antenna of the radio telescope is set to deviate from the strong electromagnetic interference angle by at least the avoidance angle, so that the radio telescope is at least the avoidance angle. The impact is reduced, so as to avoid strong electromagnetic interference and improve the data quality and observation efficiency of observations.

Description of drawings

Fig. 1 is a diagram showing the positional relationship between the ground interference source T' and the strong electromagnetic interference source T when the radio telescope is aimed at the strong electromagnetic interference source T.

Figure 2 is a schematic diagram of the ground electromagnetic interference measurement direction

Figure 3 is a spectrogram of a terrestrial interference source.

Figure 4 is the 0° tangent antenna pattern obtained by simulation.

Detailed ways

Below in conjunction with the accompanying drawings, preferred embodiments of the present invention are given and described in detail.

The present invention provides a method for avoiding strong electromagnetic interference in the far-field region of a radio telescope, which is suitable for the situation that at least one strong electromagnetic interference that causes receiver saturation exists in the far-field region of the radio telescope, and specifically includes the following steps:

Step S1: Determine the parameter information of a strong electromagnetic interference source T in the far-field area of the radio telescope; wherein, if there are multiple strong electromagnetic interference sources T in the far-field area of the radio telescope, the steps of the present invention can be repeated until all strong electromagnetic interference sources T are repeated. EMI sources are avoided.

Wherein, the parameter information of the strong electromagnetic interference source T includes the operating frequency F ₁ , the power P _T , the polarization mode and the position of the signal of the strong electromagnetic interference source T, so the step S1 specifically includes:

Step S11: Determine the operating frequency F ₁ and the power P _T of the strong electromagnetic interference source T; wherein, the operating frequency F ₁ is (f _T1 , f _T2 ), and f _T1 and f _T2 are the starting frequency and termination frequency of the strong electromagnetic interference source frequency, f _M is the center frequency of the strong electromagnetic interference source, f _M =(f _T2 +f _T1 )/2;

Step S12: Determine the polarization mode of the signal of the strong electromagnetic interference source T; wherein, the polarization mode Pol of the signal of the strong electromagnetic interference source T is horizontal polarization or vertical polarization, and the horizontal polarization is defined as H, and the vertical polarization is V.

Step S13: Determine the position of the strong electromagnetic interference source T; wherein, the position of the strong electromagnetic interference source T is A=(Lon _A , Lat _A , Alt _A ), and Lon _A , Lat _A , Alt _A respectively represent the strong electromagnetic interference source T of longitude, latitude and altitude. There are two ways to obtain the location of the strong electromagnetic interference source T. For the strong electromagnetic interference source T fixed on the ground, GPS measurement can be used to determine its position; for the strong electromagnetic interference source T moving in the air, its position can be determined by its operation. The location information published in real time by the website, such as satellites, etc.; the location of some interference sources can be broadcasted in real time through the method of real-time broadcast of their location, such as the real-time broadcast of their location information during the flight of civil aircraft; The real-time location information can be obtained after data demodulation. In the present invention, the strong electromagnetic interference source T is defined as the interference source whose signal strength causes the telescope receiver to be in a nonlinear working state (saturated) and invalidate the astronomical observation data.

Step S2: determine the parameter information of the radio telescope 20;

The parameter information of the radio telescope 20 includes the position of the focal point of the radio telescope 20, the operating frequency F ₂ of the intermediate frequency amplifier of its receiver, the feed gain G _Feed of its receiver, and the gain G _LNA of the low noise amplifier of its receiver. , and other link losses G _Loss between the feed of its receiver and the IF amplifier. Therefore, the step 2 specifically includes:

Step S21: determine the position of the focus of the radio telescope 20;

As shown in FIG. 1 , R is the focal point of the radio telescope 20 , wherein the position of the focal point R of the radio telescope 20 is B=(Lon _B , Lat _B , Alt _B ), where Lon _B , Lat _B , and Alt _B represent respectively The longitude, latitude and altitude at the focal point R of the radio telescope 20 are all determined according to the focal length of the radio telescope 20 when it leaves the factory.

Step S22: According to the working frequency F ₁ of the strong electromagnetic interference source T, select a receiver that affects the radio telescope 20, and determine the working frequency F ₂ of the intermediate frequency amplifier of the receiver;

The receiver is a part of the radio telescope 20 , and the feed of the receiver is installed at the focal point of the radio telescope 20 . The receiver is determined according to the working frequency F ₁ of the strong electromagnetic interference source T, the working frequency F ₂ of the intermediate frequency amplifier of the receiver is (f _R1 , f _R2 ), and f _R1 and f _R2 are the starting frequencies of the working frequency of the intermediate frequency amplifier. and the termination frequency, wherein the selected receiver makes a part of the working frequency of the strong electromagnetic interference source T within the working frequency F ₂ of the intermediate frequency amplifier of the receiver, so that the receiver has an influence on the radio telescope 20 . The number of receivers is one or more, so as to cover different frequency bands of the working frequency F1 _of the strong electromagnetic interference source T.

Step S23: Determine the feed gain G _Feed of the receiver, the gain G _LNA of the low noise amplifier, and other link losses G _Loss between the feed source and the intermediate frequency amplifier.

Among them, the feed, low noise amplifier, intermediate frequency amplifier and other structures are all parts of the receiver, and they are assembled into the receiver after integration. Therefore, the feed gain of the receiver G _Feed , the gain of the low noise amplifier G _LNA , and the gain of the feed Other link losses G _Loss from source to IF amplifier These performance parameters are determined in the design of the receiver.

Step S3: at the focal point of the radio telescope 20, measure the frequency spectrum of the ground interference source T', and determine the position of the ground interference source T';

Among them, the measurement method adopts the existing quasi-real-time electromagnetic environment measurement method of radio astronomy station (see [Liu Qi, Wang Na, Wang Yue, Liu Ye, Liu Feng, Chen Maozhen. Quasi-real-time electromagnetic environment measurement method of radio astronomy station. Journal of Radio Wave Science. 2017, 32(6): 718-724]), the step 3 specifically includes:

Step S31: according to the polarization mode and the position of the signal of the strong electromagnetic interference source T, set the polarization mode of the measuring antenna at the focus of the radio telescope 20 (actually adjust the attitude of the measuring antenna, determine that it can receive the corresponding polar electromagnetic waves) and pointing;

The measuring antenna is an independent electromagnetic wave receiving antenna, which needs to be placed at the focus R of the radio telescope 20 to receive radio signals from the ground. It should be noted that the measurement antenna is not a part of the radio telescope, but an antenna set up separately, which is only used to measure ground interference sources. The receiving system of the radio telescope mainly refers to the parabolic antenna and the above receiver.

The setting method of the polarization mode of the measurement antenna is as follows: according to the polarization mode of the signal of the strong electromagnetic interference source T, adjust the attitude of the measurement antenna to ensure that the measurement antenna can receive the polarization signal corresponding to the strong electromagnetic interference source T.

Since the measurement antenna is placed at the focal point R of the radio telescope 20, the position A of the strong electromagnetic interference source T and the direction of the measurement antenna are shown in FIG. 2, the direction of the measurement antenna and the position A of the strong electromagnetic interference source T are relative to the radio telescope 20 The direction of the focal point R is in the same plane, and the direction of the measuring antenna is horizontal to measure the radio signal from the ground. At this time, the measuring antenna can measure the conical area near the pointing direction. If the 3dB bandwidth of the measuring antenna is 60 degrees, Then it is possible to measure signals within a range of 60 degrees relative to the direction of the measuring antenna.

Step S32 _: Use the operating frequency F2 of the intermediate frequency amplifier as the measurement frequency band to measure, and obtain the spectrum (F[n], P[n]) as the spectrum of the ground interference source T', F[n] is the frequency point, F[n] The minimum and maximum values are respectively f _R1 , f _R2 , P[n] is the power value corresponding to the frequency point, n is the ordinal number of the frequency point, and the interval between adjacent frequency points is M.

Step S33: According to the spectrum (F[n], P[n]) of the ground interference source T', combined with the radio frequency division, determine the source of the strongest ground interference in the spectrum (F[n], P[n]) and position as the position of the terrestrial interference source T'. The position of the strongest interference on the ground is C (Lon _C , Lat _C , Alt _C ), and Lon _A , Lat _A , and Alt _A represent the longitude, latitude and altitude of the strongest interference on the ground, respectively. From this, all interferences in the measurement direction (ie, the ground direction) are obtained, and the position of the strongest interference is obtained as the position of the ground interference source, which is used to calculate the gain response between the ground electromagnetic interference and the radio telescope in the following.

以确定在干扰源处于各个方向时所分别对应的增益；在天线方向图二位数组

中，G[m]为天线增益向量，

为干扰源所在方向偏离射电望远镜的主波束轴的角度向量，m为数组中的向量序数。Step S4: Determine the two-digit array of the antenna pattern of the radio telescope 20 at the center frequency f _M of the strong electromagnetic interference source T

In order to determine the corresponding gain when the interference source is in each direction; the two-bit array in the antenna pattern

, G[m] is the antenna gain vector,

is the angle vector of the direction of the interference source deviating from the main beam axis of the radio telescope, and m is the vector ordinal number in the array.

是采用仿真软件(如grasp)建立射电望远镜的抛物面天线模型，来仿真确定的。The two-digit array of the antenna pattern

It is determined by simulation software (such as Grasp) to establish the parabolic antenna model of the radio telescope.

G[m]是抛物面天线(射电望远镜)的固有特性，由此，当干扰源处于不同方向，与抛物面天线的增益响应不一样，而确定了干扰源所在方向偏离射电望远镜的主波束轴的角度

也就可以计算出对应的增益G[m]了。obtained

G[m] is the inherent characteristic of the parabolic antenna (radio telescope). Therefore, when the interference source is in different directions, the gain response of the parabolic antenna is different, and the angle of the direction of the interference source deviating from the main beam axis of the radio telescope is determined.

The corresponding gain G[m] can also be calculated.

Step S5: When the radio telescope 20 points to the strong electromagnetic interference source _T , the gains GT and GT _' of the strong electromagnetic interference source T and the ground interference source T' entering the receiving system of the radio telescope are determined.

Wherein, when the radio telescope 20 points to the strong electromagnetic interference source T, the gain G _T of the strong electromagnetic interference source T entering the receiving system of the radio telescope is:

G _T =max(G(m)) (1)

中的天线增益向量G[m]。Among them, G(m) is the antenna gain vector, which is the two-digit array of the antenna pattern above.

The antenna gain vector G[m] in .

In addition, when the radio telescope 20 points to the strong electromagnetic interference source T, the gain G _T' of the ground interference source T' entering the receiving system of the radio telescope is determined.

为：Among them, when the radio telescope 20 points to the strong electromagnetic interference source T, the positional relationship between the strong electromagnetic interference source T and the focus R of the radio telescope 20 is shown in FIG. deflection angle of beam axis

for:

θ and θ′ are the angles between the strong electromagnetic interference source T, the ground interference source T′ and the horizontal plane, respectively. It should be noted that, since the strong electromagnetic interference source T, the ground interference source and the radio telescope 20 are all in the same plane, θ and θ′ are only calculated in one plane.

Therefore, when the radio telescope 20 points to the strong electromagnetic interference source T, the gain G _T' of the ground interference source T' entering the receiving system of the radio telescope is:

H=Alt _A -Alt _B -h (3)

为地面干扰源T′电磁波方向偏离主波束轴的角度；x＝Lat_A；y＝Lat_B；z＝Lon_B-Lon_A，Lon_A、Lat_A、Alt_A分别表示强电磁干扰源T的经度、纬度和海拔，Lon_B、Lat_B、Alt_B分别表示射电望远镜20的焦点R处的经度、纬度和海拔；h为地球半径，约为6371.004km；θ、θ′分别为强电磁干扰源T、地面干扰源T′与水平面的夹角。In the formula, H and H′ are the vertical distances from the strong electromagnetic interference source T and the ground interference source T′ to the focal point of the radio telescope 20 respectively; L and L′ are respectively the strong electromagnetic interference source T and the ground interference source T′ to the radio telescope. The horizontal distance between the focal point of 20 and the ground projection;

is the angle at which the electromagnetic wave direction of the ground interference source _T ′ deviates from the main beam axis; x _{= Lat A} ; y _{= Lat B} ; , latitude and altitude, Lon _B , Lat _B , Alt _B represent the longitude, latitude and altitude at the focus R of the radio telescope 20 respectively; h is the radius of the earth, about 6371.004km; θ, θ′ are the strong electromagnetic interference source T, respectively , the angle between the ground interference source T' and the horizontal plane.

Step S6: determine the powers P _RT and P _Rg at which the signals of the strong electromagnetic interference source T and the ground interference source T' reach the focus R of the radio telescope 20;

In the step S6, the power P _RT at which the signal of the strong electromagnetic interference source T reaches the focus R of the radio telescope 20 is determined, including:

Step S61: Determine the propagation loss P _Loss at the focal point R of the radio telescope 20 when the signal of the strong electromagnetic interference source T is transmitted;

Among them, P _Loss is calculated according to formula (7):

P _Loss = 32.44+20 log ₁₀ (fM)+20 log ₁₀ (D) (7)

In the formula, D is the straight-line distance between the interference source T and the focal point of the radio telescope 20, the unit is km; f _M is the center frequency of the strong electromagnetic interference source T, the unit is MHz.

Step S62: When the radio telescope 20 is pointed to the strong electromagnetic interference source T, the influence of the gain G _T of the strong electromagnetic interference source T entering the receiving system of the radio telescope is considered to determine that the signal of the strong electromagnetic interference source T reaches the focus R of the radio telescope 20 power P _RT at .

Wherein, the power P _RT at which the signal of the strong electromagnetic interference source T reaches the focus R of the radio telescope 20 is calculated according to formula (8):

P _RT =P _T -P _Loss +G _T (8)

Among them, P _T is the power of the strong electromagnetic interference source T, P _Loss is the propagation loss of the signal of the strong electromagnetic interference source T transmitted to the focus R of the radio telescope 20; G _T is when the radio telescope 20 points to the strong electromagnetic interference source T , the gain of the strong electromagnetic interference source T entering the receiving system of the radio telescope.

In the step S6, determine the power P _Rg of the ground interference source T' reaching the focus R of the radio telescope 20, including:

Step S61': According to the spectrum of the ground interference source T' obtained by the measurement in step S3, determine the ungained power P _g of the signal from the ground interference source T' at the focus R;

Among them, P[n] is the power value corresponding to the frequency point of the spectrum (F[n], P[n]) of the ground interference source T', n is the ordinal number of the frequency point, and M is the total number of frequency points.

Step S62 ′: When the radio telescope 20 is pointed to the strong electromagnetic interference source T, the influence of the gain G _T′ of the ground interference source T ′ entering the receiving system of the radio telescope is considered to determine the signal of the ground interference source T ′ reaching the radio telescope 20 . The power P _Rg at the focal point R.

Among them, the power P _Rg of the signal of the ground interference source T' reaching the focus R of the radio telescope 20 is:

P _Rg =P _g +G _T' (10)

Among them, P _g is the ungained power of the signal from the ground interference source T' at the focal point; G _T' is when the radio telescope 20 points to the strong electromagnetic interference source T, the ground interference source T' enters the receiving system of the radio telescope gain.

Step S7: Determine the total power P at the focus R of the radio telescope 20 .

The total power P at the focal point R of the radio telescope 20 is defined as the total power of the focal point R of the radio telescope 20 in the frequency band F ₂ (f _R1 , f _R2 ). Among them, the signal bandwidth of the strong electromagnetic interference source T is f _T2 -f _T1 ; the signal bandwidth from the ground interference source T' needs to deduct the signal bandwidth of the strong electromagnetic interference source T, which is (f _R2 -f _R1 -f _T2 +f _T1 ), the remaining two parts of the signal bandwidth after deduction are the intermediate frequency amplifier bandwidth of the receiver of the radio telescope, and it is necessary to calculate the power within this bandwidth. This is because generally speaking, electromagnetic waves are vectors, with directions, and between different directions. The superposition of the signals does not make much sense.

Therefore, the total power P at the focal point R of the radio telescope 20 is calculated according to formula (11):

Among them, f _T1 and f _T2 are the starting and ending frequencies of the strong electromagnetic interference source, f _R1 and f _R2 are the starting and ending frequencies of the intermediate frequency amplifier operating frequency, and P _RT is the signal of the strong electromagnetic interference source T reaching the radio The power at the focal point R of the telescope 20 , P _Rg is the power of the signal from the ground interference source T′ reaching the focal point R of the radio telescope 20 .

Step S8: determine the input power P _Z of the intermediate frequency amplifier of the receiver of the radio telescope according to the total power P at the focus R of the radio telescope 20 and the parameter information of the radio telescope;

The input power P _Z of the intermediate frequency amplifier of the receiver of the radio telescope is calculated by formula (12):

P _Z =P+G _Feed +G _LNA -G _Loss (12)

Among them, P is the total power at the focus R of the radio telescope 20, G _Feed is the feed gain of the receiver of the radio telescope, and G _Loss is the other link losses between the feed of the receiver of the radio telescope and the intermediate frequency amplifier.

Step S9: Determine the avoidance angle of the strong electromagnetic interference source.

In order to ensure the normal operation of the radio telescope receiver, the power P _Z of the input end of the intermediate frequency amplifier needs to be less than the power corresponding to the 1dB compression point of the intermediate frequency amplifier (the 1dB compression point of the intermediate frequency amplifier is the fixed performance index of the device), therefore, the steps of step S9 are as follows:

Step S91: determining the reduction amount G ₁ of the gain of the parabolic antenna of the radio telescope to ensure that the receiver of the radio telescope is not saturated;

When the main beam axis of the radio parabolic antenna points to a signal (such as a strong electromagnetic interference source), the signal enters the telescope receiving system and is amplified by the largest multiple (that is, the gain is the largest), when the main beam axis of the radio telescope deviates from this signal. , the gain response between this signal and the parabolic antenna will drop rapidly, thereby reducing the gain of the parabolic antenna of the radio telescope. What is calculated in this step S91 is the required gain reduction G ₁ of the parabolic antenna of the radio telescope.

The gain reduction G ₁ of the parabolic antenna of the radio telescope is calculated according to formula (13):

G ₁ =P _Z -P _1dB +S (13)

In the formula, P _Z is the input power of the intermediate frequency amplifier of the receiver of the radio telescope, P _1dB is the power corresponding to the 1dB compression point of the intermediate frequency amplifier of the receiver, and the unit is dBm; S is the safety margin.

确定在强电磁干扰源T进入射电望远镜的接收系统的增益G_T减少所述减少量G₁得到的规避增益所对应的规避角度

Step S92: according to the two-digit array of the antenna pattern in the step S4

Determine the avoidance angle corresponding to the avoidance gain obtained by reducing the reduction amount _G1 to the gain G _T of the receiving system of the radio telescope when the strong electromagnetic interference source T enters

为固有特性并保持不变，只是射电望远镜的指向位置变了，从而使得增益减小。During this process, the antenna pattern

It is an inherent characteristic and remains unchanged, but the pointing position of the radio telescope is changed, which reduces the gain.

的计算公式为：avoidance angle

The calculation formula is:

中找到的增益值为规避增益G的天线增益向量，N为在天线增益向量G[m]为G[N]时在天线方向图二位数组

中求解得到的数组中的向量序数，其为一维向量，N的数量为多个；

为天线增益向量G[m]为G[N]时天线方向图二位数组

中求解得到的干扰源所在方向偏离射电望远镜的主波束轴的角度向量。Among them, G is the avoidance gain; G[N] is the two-digit array in the antenna pattern

The gain value found in is the antenna gain vector of the avoidance gain G, and N is the two-digit array of the antenna pattern when the antenna gain vector G[m] is G[N]

The vector ordinal in the array obtained by solving in , which is a one-dimensional vector, and the number of N is multiple;

is the two-digit array of the antenna pattern when the antenna gain vector G[m] is G[N]

The angle vector of the direction of the interference source deviated from the main beam axis of the radio telescope obtained by solving in .

存在多个解的情况，为满足望远镜接收机系统处理非饱和状态，其取值考虑为最大值，依次规避角度

按照上述公式(15)进行计算。due to the angle

When there are multiple solutions, in order to satisfy the non-saturated state of the telescope receiver system, its value is considered to be the maximum value, and the angle of avoidance is in turn.

Calculate according to the above formula (15).

范围内即可)规避角度

(这里是个空间锥形角)，以达到避开所述强电磁干扰T的目的。其中，偏开的角度需等于或者大于规避角度

等于

时为临界情况，实际上望远镜主波束轴只要不在

准形角度内部，均可以观测，进入到这个角度后，观测数据无效，望远镜的有效观测时间和范围极其昂贵，所以需要尽量增加有效的观测范围。除了

这个角度不能观测外，其他范围均是有用的。Step S10: Make the main beam axis of the parabolic antenna of the radio telescope deviate from the strong electromagnetic interference by an angle T of at least (as long as the deviation is

range) avoidance angle

(here is a spatial cone angle), in order to achieve the purpose of avoiding the strong electromagnetic interference T. Among them, the deviation angle must be equal to or greater than the avoidance angle

equal

is a critical case, in fact, as long as the main beam axis of the telescope is not

The interior of the quasi-shaped angle can be observed. After entering this angle, the observation data is invalid, and the effective observation time and range of the telescope are extremely expensive, so it is necessary to increase the effective observation range as much as possible. Apart from

Except that this angle cannot be observed, other ranges are useful.

In addition, when the number of strong electromagnetic interference sources is multiple, in the step S10, steps S1-S9 are repeated before the main beam axis of the parabolic antenna of the radio telescope is deviated to determine the number of strong electromagnetic interference sources T. Avoidance angle, so that the main beam axis of the parabolic antenna of the radio telescope is deviated from each strong electromagnetic interference T by an angle at least equal to the avoidance angle of each strong electromagnetic interference source T, respectively.

Experimental results:

The following is an example of a civil aircraft with a position of A (89.7729°E, 43.6026°N, 8000m) as a source of strong electromagnetic interference, and the experimental results of the method for avoiding strong electromagnetic interference in the far-field region of a radio telescope of the present invention are given.

Step S1: The T position of the strong electromagnetic interference source (civil aircraft) in the far-field region of a certain radio telescope is given as A (89.7729°E, 43.6026°N, 8000m). The interference sources of civil aircraft are the airborne automatic dependent surveillance-Broadcast (ADS-B) and the airborne distance measuring equipment (DME). The detailed parameter information is shown in Table 1.

Step S2, the position point B (89.6822°E, 43.6011°N, 1760m) at the focal point of the radio telescope 20 is given; according to the working frequency of the interference source in step 1, the working frequency of the intermediate frequency amplifier of the receiver corresponding to the radio telescope 20 is 1000-2000MHz , the feed gain G _Feed is 19dB, the gain of the low noise amplifier G _LNA is 30dB, and the other link loss G _Loss between the feed source and the IF amplifier is about 6dB.

Table 1 CAS signal parameters

Step S3, measure the direction spectrum of the interference source at the focus of the radio telescope 20, the initial frequency range is 1000-2000MHz, the frequency point interval M is 30kHz, and the frequency point n is 33334. The measurement result of step S3 is shown in FIG. 3 . According to the obtained measurement spectrum, combined with the radio frequency division, the main ground interference source T' in the frequency band 1000-2000MHz is the mobile communication base station, and the location is C (89.7564°E, 43.5653°N, 2199.29m).

Step S4: As shown in FIG. 4, using the antenna simulation software, a parabolic antenna model is established, and the antenna pattern at the 20 frequency point of the radio telescope is obtained by simulation at 1090 MHz.

Step S5: Calculate the antenna gain G _T =60.94dBi of the signal interfered by the civil aircraft entering the telescope receiver system according to the antenna pattern. According to the position of the ground interference source T' as C, calculate the antenna gain G _T' =-38.07dBi of the signal of the ground interference source entering the receiving system of the radio telescope.

Step S6: Calculate the free space loss P _Loss =111.21dB according to the formula (7), where f _M is 1090MHz; according to the formula (8), calculate the power P _RT =16.52dBm at the focal point where the air signal arrives at the radio telescope; According to the formula (9)- (10) Calculate the power P _Rg = -119.05dBm at the focal point of the radio telescope of the ground electromagnetic interference in the frequency band 1000-2000MHz.

Step S7: Calculate the power P=-3.03dBm at the focal point of the radio telescope in the frequency band 1000-2000MHz according to formula (11).

Step S8: Calculate the power P _Z =39.97dBm at the input end of the intermediate frequency amplifier according to formula (12).

为1.085°。Step S9: The 1dB compression point power of the affected receiver intermediate frequency amplifier is 20dBm, the safety margin is 5dB, and the calculation is performed according to formulas (13)-(15), avoiding the angle

is 1.085°.

In step S10, the main beam axis of the radio telescope is deviated from the civil aircraft by at least 1.085°, so that the receiver can work normally. As a result, the original radio telescope pointed to a civil aircraft, which has the greatest impact. After the angle is deflected, the impact is reduced. The reason is that when the parabolic antenna points to a signal, the gain is the largest, and after the deflection, the gain decreases rapidly. That is to say, the observation data is valid only when the telescope is deflected at least 1.085 degrees. The observation target of the telescope is not an aircraft (the plane is the source of interference), and the range other than the cone angle of 1.085 degrees relative to the plane is all For the effective observation range, that is, the larger the effective observation range of the telescope, the better, and the more effective observation data will be.

The above descriptions are only preferred embodiments of the present invention, and do not limit the scope of the present invention. Various changes can be made to the above-mentioned embodiments of the present invention. That is, all simple and equivalent changes and modifications made according to the claims and descriptions of the present invention fall into the protection scope of the claims of the present invention. What is not described in detail in the present invention is conventional content.

Claims (7)

1. a radio telescope far-field area strong electromagnetic interference avoidance method, is characterized in that, comprises: Step S1: determine the parameter information of a strong electromagnetic interference source in the far-field area of the radio telescope; Step S2: determine the parameter information of the radio telescope; Step S3: at the focal point of the radio telescope, measure the frequency spectrum of the ground interference source, and determine the position of the ground interference source; Step S4: Determine the two-digit array of the antenna pattern of the radio telescope at the center frequency f _M of the strong electromagnetic interference source

to determine the corresponding gain when the interference source is in each direction; G[m] is the antenna gain vector,

is the angle vector of the direction of the interference source deviating from the main beam axis of the radio telescope, and m is the vector ordinal number in the array; Step S5: determine when the radio telescope points to the strong electromagnetic interference source, the gain of the strong electromagnetic interference source and the ground interference source entering the receiving system of the radio telescope; Step S6: determine the power at which the signals of the strong electromagnetic interference source and the ground interference source reach the focus of the radio telescope; Step S7: determine the total power at the focus of the radio telescope; Step S8: determine the input power of the intermediate frequency amplifier of the receiver of the radio telescope according to the total power at the focus of the radio telescope and the parameter information of the radio telescope; Step S9: determining the avoidance angle of the strong electromagnetic interference source; Step S10: Make the angle by which the main beam axis of the parabolic antenna of the radio telescope deviates from the source of strong electromagnetic interference is at least the avoidance angle

In the step S1, the parameter information of the strong electromagnetic interference source includes the operating frequency F ₁ , the power P _T , the polarization mode and the position of the signal; in the step S2, the parameter information of the radio telescope includes The position of the focal point of the radio telescope, the operating frequency F ₂ of its receiver's IF amplifier, its receiver's feed gain G _Feed , its receiver's low-noise amplifier gain G _LNA , and its receiver's feed to IF other link loss G _Loss between amplifiers; In the step S5, when the radio telescope points to the strong electromagnetic interference source, the gain G _T of the strong electromagnetic interference source entering the receiving system of the radio telescope is: G _T =max(G(m)), Among them, G(m) is the two-digit array of the antenna pattern

Antenna gain vector G[m] in ; When the radio telescope points to a strong electromagnetic interference source, the gain G _T' of the ground interference source entering the receiving system of the radio telescope is:

H=Alt _A -Alt _B -h,

In the formula, H and H′ are the vertical distances from the strong electromagnetic interference source and the ground interference source to the focus of the radio telescope, respectively; L and L′ are the projections from the strong electromagnetic interference source and the ground interference source to the focus of the radio telescope and the ground projection. Horizontal distance;

is the angle that the electromagnetic wave direction of the ground interference source deviates from the main beam axis; x=Lat _A ; y=Lat _B ; z=Lon _B -Lon _A , Lon _A , Lat _A , Alt _A represent the longitude and latitude of the strong electromagnetic interference source respectively and altitude, Lon _B , Lat _B , and Alt _B represent the longitude, latitude and altitude of the focal point of the radio telescope, respectively; h is the radius of the earth; The step S9 includes: Step S91: determine the reduction amount G ₁ of the gain of the parabolic antenna of the radio telescope; The gain reduction G ₁ of the parabolic antenna of the radio telescope is: G ₁ =P _Z -P _1dB +S, In the formula, P _Z is the input power of the intermediate frequency amplifier of the receiver of the radio telescope, P _1dB is the power corresponding to the 1dB compression point of the intermediate frequency amplifier of the receiver, the unit is dBm; S is the safety margin; Step S92: according to the two-digit array of the antenna pattern in the step S4

Determine the avoidance angle corresponding to the avoidance gain obtained by reducing the gain G _{T of} the receiving system of the radio telescope when the source of strong electromagnetic interference enters the radio telescope

the avoidance angle

for:

Among them, G is the avoidance gain; G[N] is the antenna gain vector with the gain value found in the two-digit array of the antenna pattern as the avoidance gain G, and N is when the antenna gain vector G[m] is G[N] The vector ordinal in the array obtained by solving the two-digit array of the antenna pattern, which is a one-dimensional vector;

is the angle vector of the direction of the interference source deviating from the main beam axis of the radio telescope obtained by solving the two-digit array of the antenna pattern when the antenna gain vector G[m] is G[N]. 2. The method for avoiding strong electromagnetic interference in the far-field region of a radio telescope according to claim 1, wherein the step S3 comprises: Step S31: according to the polarization mode and position of the signal of the strong electromagnetic interference source, set the polarization mode and the direction of the measuring antenna located at the focus of the radio telescope; Step S32 _: take the operating frequency F2 of the intermediate frequency amplifier as the measurement frequency band to measure, and obtain

As the spectrum of the ground interference source, F[n] is the frequency point, P[n] is the power value corresponding to the frequency point, and n is the ordinal number of the frequency point; Step S33: Determine the source and location of the strongest ground interference in the spectrum according to the frequency spectrum of the ground interference source and in combination with radio frequency division, and use it as the position of the ground interference source. 3. The method for avoiding strong electromagnetic interference in the far-field region of a radio telescope according to claim 1, wherein in the step S4, the two-digit array of the antenna pattern

It is determined by simulation software to establish the parabolic antenna model of the radio telescope. 4. radio telescope far-field area strong electromagnetic interference evasion method according to claim 1, is characterized in that, in described step S6, it is determined that the signal of strong electromagnetic interference source reaches the power P _RT at the focal point of radio telescope, including : Step S61: Determine the propagation loss P _Loss at the focal point of the radio telescope when the signal of the strong electromagnetic interference source is transmitted; Step S62: when the radio telescope is pointed to the strong electromagnetic interference source, the influence of the gain _GT of the strong electromagnetic interference source entering the receiving system of the radio telescope is considered to determine the power P _RT at which the signal of the strong electromagnetic interference source reaches the focus of the radio telescope; Determine the power P _Rg of the terrestrial interferer reaching the focal point of the radio telescope, including: Step S61': according to the spectrum of the ground interference source, determine the ungained power P _g of the signal from the ground interference source at the focus; Step S62': Consider the influence of the gain G _T' of the ground interference source entering the receiving system of the radio telescope when the radio telescope points to the strong electromagnetic interference source, to determine the power P _Rg at which the signal of the ground interference source reaches the focus of the radio telescope. 5. radio telescope far-field region strong electromagnetic interference avoidance method according to claim 1, is characterized in that, in described step S7, the total power P at the focal point of radio telescope is:

Among them, f _T1 and f _T2 are the starting and ending frequencies of the strong electromagnetic interference source, f _R1 and f _R2 are the starting and ending frequencies of the working frequency of the intermediate frequency amplifier, and P _RT is the signal of the strong electromagnetic interference source reaching the radio telescope The power at the focal point of , P _Rg is the power of the signal of the ground interference source reaching the focal point of the radio telescope; In the step S8, the input power P _Z of the intermediate frequency amplifier of the receiver of the radio telescope is: P _Z =P+G _Feed +G _LNA -G _Loss , Among them, P is the total power at the focal point of the radio telescope, G _Feed is the feed gain of the receiver of the radio telescope, and G _Loss is the other link losses between the feed of the receiver of the radio telescope and the intermediate frequency amplifier. 6 . The method for avoiding strong electromagnetic interference in the far-field region of a radio telescope according to claim 1 , wherein the number of the strong electromagnetic interference sources is one or more. 7 . 7. The method for avoiding strong electromagnetic interference in the far-field region of a radio telescope according to claim 6, wherein when the number of the strong electromagnetic interference sources is multiple, in the step S10, Steps S1-S9 are repeated before the main beam axis of the parabolic antenna is deviated to determine the avoidance angle of each strong electromagnetic interference source, so that the main beam axis of the parabolic antenna of the radio telescope is deviated from each strong electromagnetic interference angle by at least the strong electromagnetic interference angle. The avoidance angle corresponding to the interference source.

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