CN114460609A - A kind of missile-borne navigation receiver rotation compensation and tracking method - Google Patents

Abstract

The invention provides a missile-borne navigation receiver rotation compensation and tracking method, which comprises the following steps: separating the rotating doppler from the doppler shift of the received signal; establishing a warhead rotation analysis model to determine the Doppler frequency shift of a carrier wave and the Doppler frequency shift of a code caused by rotation; estimating and acquiring the rotation speed of the warhead; respectively initializing and tracking a space cone angle formed by a satellite signal ray and the vertical direction and a distance r from an antenna phase center to a rotation center; the rotary NCO value is calculated and then the carrier NCO value is corrected with the rotary NCO value. The method can effectively improve the stability and the precision of tracking.

Description

A kind of missile-borne navigation receiver rotation compensation and tracking method

technical field

The invention belongs to the technical field of satellite navigation, and in particular relates to a rotation compensation and tracking method of a missile-borne navigation receiver.

Background technique

Satellite navigation can provide all-weather, full-time, continuous high-precision three-dimensional position, three-dimensional speed and time information for users of land, sea and space, and has incomparable advantages over other navigation methods. In recent years, it has been widely used in various fields of social life. applications, especially in the military. Various types of precision guided missiles have many technical advantages such as high precision, long range, accurate strike and reliable performance. They are the main means for military powers to ensure national security and enhance military deterrence. At the same time, countries also generally add guidance and control components to traditional conventional unguided munitions to reduce the amount of ammunition missed, effectively improve the strike effect, and realize the upgrading and transformation of munitions. Therefore, various advanced precision-guided weapons have become the protagonists of modern warfare.

In order to maintain the stability of the flight, the projectile usually rotates at a high speed during flight, and the rotation speed can reach 30,000 rpm. In practice, in order to facilitate the continuous reception of satellite signals during rotation, a loop antenna or a multi-antenna structure is usually used. For the loop antenna, due to various reasons, the rotation center of the antenna and the phase center of the antenna will not coincide, which will cause the Doppler of the received satellite signal to be modulated, which will adversely affect the normal reception and stable tracking of the signal. In severe cases, the tracking loop will lose lock. As a result, the tracking stability and accuracy of the missile-borne navigation receiver are not high.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a rotation compensation and tracking method for a missile-borne navigation receiver to solve the deficiencies of the prior art.

To achieve the above object, the present invention adopts the following technical solutions:

An embodiment of the present invention provides a method for rotation compensation and tracking of a missile-borne navigation receiver, including:

Separating the rotational Doppler from the Doppler shift of the received signal;

A warhead rotation analysis model is established to determine the Doppler frequency shift of the carrier and the Doppler frequency of the code caused by the rotation; where the Doppler frequency shift of the carrier is Δf=2πnr sin(2πnt-β)cosαf/c; Le frequency shift Δf _C =2πnrsin(2πnt-β)cosαf _C /c; where f is the carrier frequency, f _C is the code rate, n is the rotation speed of the warhead, r is the distance from the antenna phase center to the rotation center, and α is The included angle between the satellite signal ray and the projection line of the satellite signal ray on the vertical projection plane passing through the rotation axis of the shell; β is the included angle between the projection line of the satellite signal ray on the vertical projection plane passing through the shell rotation axis and the vertical direction;

Estimate the rotation speed of the warhead;

Initialize and track the space cone angle formed by the satellite signal ray and the vertical direction and the distance r from the antenna phase center to the rotation center;

Calculate the rotational NCO value, and then use the rotational NCO value to correct the carrier NCO value.

Further, to estimate and obtain the rotation speed of the warhead, the rotation speed value is obtained by performing FFT on the product sequence of the I/Q values before compensation; the details include:

De-modulate and spread the received satellite signal before compensation to obtain the I/Q integral value;

Do a dot product calculation on the integral value of I/Q to obtain a set of IQ sequences;

The spectrum sequence IQ _spectrum =abs(fft(IQ, M)) of IQ sequence is obtained by FFT processing to IQ sequence; Wherein, abs() represents taking absolute value calculation, and M represents the number of points calculated by FFT;

Find the peak value of the spectrum sequence and note the unit m where it is located, and finally calculate the rotational speed n=f _s *(m-1)/M, where f _s represents the frequency of the IQ sequence.

Further, the initialization and tracking of the space cone angle formed by the satellite signal ray and the vertical direction specifically include:

Three sets of local codes and local carriers are generated at three angles of β+θ, β, and β-θ, where β is the spatial cone angle and θ is the convergence step size; then according to the Doppler frequency shift of the carrier and the Doppler frequency of the code Calculate the compensation amount for the frequency shift, obtain the rotation compensation amount and then apply the rotation compensation amount to the rotating NCO;

Three groups of local codes and local carriers are used for demodulation and despreading respectively, and three groups of I/Q values are obtained. The angle corresponding to the optimal group of I/Q values is selected as a new reference, and the NCO is updated.

Further, initializing and tracking the distance r from the antenna phase center to the rotation center specifically includes:

On the basis of the current r, add and subtract a step value respectively, then calculate the rotation compensation amount respectively, and then perform demodulation and despreading respectively to obtain three sets of I/Q values, and select the optimal set of I/Q values. Corresponding to r as the current compensation amount.

Further, calculating the rotating NCO value, and then correcting the carrier NCO value with the rotating NCO value specifically includes:

When the navigation signal is the L1 signal of GPS, the accumulator bit width of the carrier NCO is 32 bits, the signal sampling rate is f _s , the signal intermediate frequency is f _i , the satellite Doppler is f _d , the code rate is f _ca , and the rotation speed is n revolutions per second, the step values of no rotation compensation carrier NCO, no rotation compensation code NCO, and rotation NCO are:

f _carrystep =(f _i +f _d )*2 ³² /f _s

f _castep = (f _ca +f _d /1540)*2 ³² /f _s

f _rotatestep =n*2 ³² /f _s

After the phase value of the rotating NCO is obtained, the rotating phase difference is performed to obtain _Δθrotate , and then the rotating phase difference value _Δθrotate is added to the carrier NCO and the code NCO to complete the effective compensation of the rotating phase;

f _carrystep =(f _i +f _d )*2 ³² /f _s +Δθ _rotate

f _castep =(f _ca +f _d /1540)*2 ³² /f _s +Δθ _rotate /1540.

The invention provides a method for rotation compensation and tracking of a missile-borne navigation receiver, which can effectively improve the stability and accuracy of tracking.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

1 is a flowchart of a method for compensating rotation and tracking of a missile-borne navigation receiver provided by an embodiment of the present invention;

Figure 2 is the coordinate system of the missile-borne receiver;

Figure 3 is the I/Q output without rotation compensation;

Figure 4 is the Doppler output without rotation compensation;

Figure 5 is the I/Q output after rotation compensation;

Figure 6 is the Doppler output after rotation compensation.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

FIG. 1 is a schematic flowchart of a rotation compensation and tracking method for a missile-borne navigation receiver according to an embodiment of the present invention. Include the following steps:

S101. Separate the rotational Doppler from the Doppler frequency shift of the received signal.

The Doppler of the received signal consists of two parts: translational Doppler and rotational Doppler, and the translational Doppler and rotational Doppler are separable, which is an effective way to compensate the missile rotation for the navigation receiver. Influence creates the conditions.

S102 , establishing a warhead rotation analysis model to determine the Doppler frequency shift of the carrier and the Doppler frequency shift of the code caused by the rotation.

Model the rotation of the warhead. The main method steps are as follows:

Figure 2 shows the coordinate system of the missile-borne receiver. The deviation between the antenna phase center and the antenna rotation center is r(OP), O is the antenna rotation center, P is the antenna phase center, the shell rotates around the Y axis, and S is the satellite position, α is the angle between OS and OE, and β is the angle between OE and OD. α is the angle between the satellite signal ray OS and the projection line OE of the satellite signal ray on the vertical projection plane passing through the rotation axis of the shell; β is the projection line OE and the vertical direction of the satellite signal ray on the vertical projection plane passing through the shell rotation axis OD angle. where cosαcosβ=cos∠DOS.

The formula for calculating satellite Doppler shift is:

Δf=v _r f/c (1)

Among them, Δf is the Doppler frequency shift, v _r is the relative velocity of the receiver and the satellite, f is the frequency of the transmitted signal, and c is the speed of light.

As shown in Figure 1, let v _τ be the tangential velocity of the receiver antenna phase center with the antenna rotation center, then the component of this velocity in the OS direction can be expressed as:

v _r = v _τ sin(2πnt-β)cosα (2)

Among them, n is the rotation speed of the antenna. Since v _τ = 2πnr (n is the rotation speed of the warhead, and r is the distance between the antenna phase center and the rotation center), the Doppler frequency shift of the carrier and the code caused by the rotation can be expressed as :

Δf=2πnr sin(2πnt-β)cosαf/c (3)

Δf _C = 2πnr sin(2πnt-β)cosαf _C /c (4)

Since the code rate is much lower than the carrier frequency, the rotation mainly has a great influence on the carrier tracking, but has little effect on the code tracking. Only the carrier compensation is considered below.

In principle, as long as the rotational speed n, the radius r and the angles α and β are known, the corresponding local carrier and local code can be generated to demodulate the Doppler modulation brought by the rotation.

S103, estimate and obtain the rotation speed of the warhead.

The speed value can be obtained by performing fast Fourier transform (FFT) on the product sequence of the I/Q values before compensation.

If the estimated period of the rotation speed of the warhead is 1 second, the I/Q integral value can be obtained by demodulating and de-spreading the received satellite signal before compensation. The integral value is denoted as I and Q, and then the integral value of I/Q is dot-multiplied to obtain a set of sequences:

IQ(k)=I(k)*Q(k)(k=1,2,...,1000)

Then perform FFT processing on the IQ sequence to obtain the spectral sequence of the IQ sequence:

IQ _spectrum =abs(fft(IQ,M))

Among them, abs() represents the calculation of the absolute value, and M represents the number of points in the FFT calculation. Then find the peak of the spectrum sequence and note the unit m where it is located, and finally calculate the rotational speed:

n= _fs *(m-1)/M. where f _s is the frequency of the IQ sequence, and f _s is 1000 for an integration duration of 1 ms.

S104, respectively initialize and track the space cone angle formed by the satellite signal ray and the vertical direction and the distance r from the antenna phase center to the rotation center.

Initialization and tracking of the space cone angle ∠DOS formed by the satellite signal ray OS and the vertical direction OZ.

In practice, for the navigation receiver, the position of the satellite is unknown, so the space cone angle ∠DOS pair in Fig. 1 is unknown, so the space cone angle ∠DOS is initialized to 0°.

In order to ensure the convergence of the space cone angle, and take into account the convergence speed and tracking accuracy of the space cone angle tracking, the initial convergence step is set to θ=90°, which will ensure that the satellite can converge in the entire airspace. Adaptive adjustment is made in the process of space cone angle tracking, and the step size is set to θ=10° during the final stable tracking.

Assuming that the angle ∠DOS is β at a certain moment, similar to code loop tracking, three sets of local codes and local carriers are generated with β+θ, β, β-θ, and three ∠DOS angles respectively, and then according to formula (3), ( 4) Calculate the compensation amount, get the rotation compensation amount, and then apply the rotation compensation amount to the rotating NCO.

Three groups of local codes and local carriers are used for demodulation and despreading respectively, and three groups of I/Q values are obtained. The angle ∠DOS corresponding to the optimal group of I/Q values is selected as the new benchmark, and the NCO is updated.

Initialization and tracking of the distance r from the center of the antenna phase to the center of rotation.

The distance r can be set as an initial value according to product characteristics.

The tracking of the distance r is similar to the space cone angle. On the basis of the current radius r, a step value is added and subtracted respectively, and then the rotation compensation amount is calculated respectively, and then demodulation and despreading are performed respectively to obtain three sets of I/Q values. , select the optimal set of I/Q values corresponding to the radius r as the current compensation radius.

S105: Calculate the rotational NCO value and then use the rotational NCO value to correct the carrier NCO value.

The rotation NCO is similar to the carrier NCO and the code NCO, and the step value is related to the rotation speed.

Taking GPS L1 as an example, if the accumulator bit width of the carrier NCO is 32 bits, the signal sampling rate is f _s , the signal intermediate frequency is f _i , the satellite Doppler is f _d , the code rate is f _ca , and the rotation speed is n rev/sec, the carrier NCO (without rotation compensation), the code NCO (without rotation compensation), and the step values of the rotation NCO are:

f _carrystep =(f _i +f _d )*2 ³² /f _s (5)

f _castep = (f _ca +f _d /1540)*2 ³² /f _s (6)

f _rotatestep = n*2 ³² /f _s (7)

After the phase value of the rotating NCO is obtained, the rotating phase difference is performed to obtain Δθ _rotate , and then the rotating phase difference value Δθ _rotate is added to the carrier NCO and the code NCO to complete the effective compensation of the rotating phase:

f _carrystep =(f _i +f _d )*2 ³² /f _s +Δθ _rotate (8)

f _castep =(f _ca +f _d /1540)*2 ³² /f _s +Δθ _rotate /1540 (9)

After getting the value of the rotation NCO, add the value to the carrier NCO and the code NCO to obtain effective rotation compensation.

The following calculation and simulation examples take the L1 of GPS as an example of C/A code modulation, the code rate is 1.023MHz, the navigation receiver is installed on the projectile warhead, the sampling ring microstrip antenna, the projectile speed is 30000 rpm, the antenna rotation center and the antenna The distance between the phase centers is 0.05 meters. The actual elevation angle of the satellite is 30° (60° from the zenith), the Doppler is 0 Hz, and the loop tracking period is 1 millisecond.

Figure 3 and Figure 4 show the I/Q integral output and Doppler output without rotation compensation. Figure 5 and Figure 6 show the I/Q integral value and Doppler output result after rotation compensation. Figure 3 - The unit of the abscissa of Fig. 6 is milliseconds, the ordinate of Fig. 3 and Fig. 5 is the relative amplitude value, and the unit of the ordinate of Fig. 4 and 6 is Hz. As can be seen from the figure, the performance is significantly improved after compensation.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (5)

1. A missile-borne navigation receiver rotation compensation and tracking method, comprising:

separating the rotating doppler from the doppler shift of the received signal;

establishing warhead rotation analysis model to determine rotationDoppler shift of the carrier and Doppler shift of the code caused by the transition; wherein the Doppler shift of the carrier wave is 2 pi nr sin (2 pi nt-beta) cos alpha f/c; doppler shift of code Δ f_C＝2πnr sin(2πnt-β)cosαf_CC; where f is the carrier frequency, f_CThe code rate is n, the rotation speed of the warhead is n, r is the distance from the phase center of the antenna to the rotation center, and alpha is the included angle between the satellite signal ray and the projection line of the satellite signal ray on the vertical projection plane passing through the rotating shaft of the cannonball; beta is an included angle between a projection line of the satellite signal ray on a vertical projection surface passing through the shell rotating shaft and the vertical direction;

estimating and acquiring the rotation speed of the warhead;

respectively initializing and tracking a space cone angle formed by a satellite signal ray and the vertical direction and a distance r from an antenna phase center to a rotation center;

the rotary NCO value is calculated and then the carrier NCO value is corrected with the rotary NCO value.

2. The method of claim 1, wherein the estimation of the rotation speed of the bullet is performed by performing FFT on the product sequence of I/Q values before compensation to obtain a rotation speed value; the method specifically comprises the following steps:

demodulating and despreading the satellite signals received before compensation to obtain an I/Q integral value;

performing point multiplication on the integral value of the I/Q to obtain a group of IQ sequences;

carrying out FFT processing on the IQ sequence to obtain a frequency spectrum sequence IQ of the IQ sequence_spectrumAbs (fft (IQ, M)); wherein abs () represents the absolute value calculation, and M represents the number of points of FFT calculation;

finding out the peak value of the frequency spectrum sequence, recording the unit m where the frequency spectrum sequence is located, and finally calculating the rotating speed n ═ f_s(M-1)/M, wherein f_sRepresenting the frequency of the IQ sequence.

3. The method of claim 1, wherein initializing and tracking the space cone angle formed by the satellite signal ray and the vertical direction specifically comprises:

generating three groups of local codes and local carriers by using three angles of beta + theta, beta and beta-theta respectively, wherein beta is a space cone angle, and theta is a convergence step length; then calculating compensation amount according to the Doppler frequency shift of the carrier and the Doppler frequency shift of the code, and applying the rotation compensation amount to the rotary NCO after obtaining the rotation compensation amount;

and demodulating and despreading the signals by using the three groups of local codes and the local carrier waves respectively to obtain three groups of I/Q values, selecting an angle corresponding to the optimal group of I/Q values as a new reference, and updating the NCO.

4. The method of claim 1, wherein initializing and tracking the distance r from the antenna phase center to the center of rotation specifically comprises:

and respectively adding and subtracting a stepping value on the basis of the current r, respectively calculating rotation compensation quantities, respectively demodulating and despreading to obtain three groups of I/Q values, and selecting the r corresponding to the optimal group of I/Q values as the current compensation quantity.

5. The method of claim 1, wherein calculating a rotated NCO value and then correcting the carrier NCO value using the rotated NCO value specifically comprises:

when the L1 signal of GPS, the accumulator bit width of the carrier NCO is 32 bits, and the signal sampling rate is f_sThe intermediate frequency of the signal being f_iThe satellite Doppler is f_dCode rate is f_caAnd if the rotating speed is n revolutions per second, the step values of the carrier NCO without rotation compensation, the NCO without rotation compensation and the NCO with rotation compensation are respectively as follows:

f_carrystep＝(f_i+f_d)*2³²/f_s

f_castep＝(f_ca+f_d/1540)*2³²/f_s

f_rotatestep＝n*2³²/f_s

after obtaining the phase value of the rotary NCO, carrying out rotary phase difference to obtain delta theta_rotateThen the rotational phase difference score Δ θ_rotateThe effective compensation of the rotation phase can be completed by adding the carrier NCO and the code NCO;

f_carrystep＝(f_i+f_d)*2³²/f_s+Δθ_rotate

f_castep＝(f_ca+f_d/1540)*2³²/f_s+Δθ_rotate/1540。

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