RU2110077C1 - Method determining course angle and coordinates of locations of objects by radio signals of spacecraft of satellite radio navigation systems - Google Patents

Abstract

FIELD: space radio navigation and geodesy. SUBSTANCE: navigation radio signals of satellites are received by each of four antenna and receiver devices installed on objects. In this case antennas of these antenna and receiver devices form rectangular system of coordinates which axes are parallel to axes of objects. Pseudoranges are found, differences of ranges are determined by way of their mutual subtraction, coordinates of location and course angle are also calculated. Navigation radio signals of one and same satellite are received simultaneously by each antenna and receiver device. Increments of ranges are calculated by measurement of increments of phases caused by Doppler shifts of carrier frequency over measured interval with use of phase autoadjustments of frequency and differences of increments of ranges in mutually orthogonal bases are determined by way of mutual subtraction of measured increments of phases. EFFECT: improved authenticity of method. 1 cl, 2 dwg

Description

 The invention relates to space radio navigation, geodesy and can be used to determine the course angle and the coordinates of the location of objects.

 A known method for determining the location and heading angle of objects from the navigation radio signals of spacecraft (SC) of satellite radio navigation systems (SRNS) using measured pseudorange using four antenna receivers of satellite signals, the antennas of which are mounted on objects so that they form a rectangular coordinate system (Applications of Navstar GPS fo presion attitude determination Roht Ben. D., Singh Ram-Nandan P. "Proc. 4 th. Geod. Symp Sattel. Position., Austin, Tex. 28.Apr.-28 Max, 1986, v .2. "S.1, 2, 1345-1359, prototype).

The disadvantages of this method are:
errors in navigation definitions due to the instability of the frequencies of the radio signals of the navigation artificial satellite of the Earth (NIE) and generators of objects;
measurement errors, definitions caused by the angular displacement of the antennas of objects in the process of their movement.

,
где
λ_н -длина волны несущей частоты;
B_ссн -ширина полосы схемы слежения за несущей;
P_c/P_ш - отношение мощности сигнала к спектральной мощности шума;
π = 3,1415... .To evaluate the accuracy of phase increment measurements using CCH, the dispersion expression ε $\genfrac{}{}{0ex}{}{\text{2}}{\text{f}}$ (Airborne satellite navigation devices. / Ed. By V.S.Shebshaevich.- M .: Transport, 1988)

,
Where
λ _n is the wavelength of the carrier frequency;
B _SSN is the bandwidth of the carrier tracking circuit;
P _c / P _W - the ratio of signal power to spectral noise power;
π = 3.1415 ....

) при P_с/P_ш = 30 дБ Гц и B_ссн = 20 Гц составят 0,62 см.Measurement errors of phase increment, for example, at a frequency f ≈ 1600 MHz of the global positioning system (

) at P _s / P _w = 30 dB Hz and B _ssn = 20 Hz will be 0.62 cm.

 In CPHC, the material carrier of information about the relative position and relative movement in space of a navigation object and a navigation point (NESS) is an electromagnetic wave propagating in the medium between the antennas of these two objects. This information is contained in the parameters of the signals emitted by the navigation spacecraft; therefore, in the CPHC during the measurement of the radio navigation parameters, a functional relationship is established not between the spacecraft and the determined objects, the position of which in space is determined by the position of their centers of mass in a certain coordinate system, but between the phase centers of the object antennas and artificial navigation satellite of the Earth (NISH). Consequently, the phase center of the antennas is a reference point for the location coordinates and a reference point for the navigation parameter of both the NISS and the detected objects.

 Physically, the phase center is the point from which for the observer located in the far zone of the antenna, spherical electromagnetic waves of the emitted (received) field emit (enter). As is known, spherical wavefront of an electromagnetic wave is produced by point emitters. Actually, in practice, antennas, depending on the operating frequency range, on the design, take a well-defined specific volume, therefore, for example, determining the base of an interferometer as the distance between antennas is technically incorrect. The accuracy of knowing the length of the base of the interferometer, its orientation in space determines the accuracy of determining the angular coordinates, and in general the accuracy of solving the navigation problem, determined by objects.

 In accordance with the foregoing, the concept of the "phase center" of the antenna. Accordingly, the distance between the antennas, which is the base of the radio interferometer, will be determined as the distance between the phase centers of the antennas.

 The purpose of the invention is to increase the accuracy of determining the heading angle and the coordinates of the location of objects on the navigation radio signals of the SRNS.

The goal is achieved by:
a new set of actions on received satellite radio navigation signals;
separation of signals with Doppler frequency offset in the leading and slave antenna-receiving devices of the interferometer by squaring the received satellite radio signals and filtering them, followed by returning the frequencies to the desired using frequency dividers;
measurements on the measured interval of phase increments caused by the Doppler frequency shift by using quadrature phase detectors, the first outputs of which receive signals with a Doppler frequency shift, and the second - the signal of the reference generator;
determining the difference in the path of the radio signals between the phase center of the satellite antenna and the phase centers of the antennas of the interferometer as the difference of the phase increments measured on the measured interval due to the Doppler frequency shift.

 The geometric interpretation of the proposed method is illustrated by the example of one orthogonal base formed by two phase centers of the antennas of the interferometer FC1 and FC2 and three positions of the phase center of the same satellite (Fig. 1).

.The points T ₁ , T ^* , T ₂ (Fig. 1) denote the positions of the phase center of the satellite antenna in orbit, which are the boundaries of the samples of the navigation parameter. Using the cosine theorem and expansion in a series with terms no higher than second order for the three positions of the phase center of the NESA antenna, one can obtain
for the phase center FC1 of the antenna An1 of the detected object

.

.for the phase center FCZ antenna AnZ

.

Thus, each difference in the path of the radio signals ΔR ₁ (t ^* ), ΔR ₃ (t ^* ) gives information about the projection of the path traveled by the phase center of the NESA antenna from point T ₁ to point T ₂ on the direction of the lines R ₁ (t ^* ), R ₃ (t ^* ) connecting the point T ^* (the position of the phase center of the NISS antenna at time T ³ ) with the phase centers An1 and An2.

.Using the theorem of cosines and row expansion with terms no higher than second order for the phase center of the NHA antenna located at point T ^* , it is possible to obtain

.

Двойная разность дальностей ΔR_1,3(t^*) - разность приращений дальности R(t) дает информацию о проекции базового расстояния d₁ между фазовыми центрами антенн объекта Ан1, Ан3 на направление прямой R(t^*), соединяющей среднюю точку базы с фазовым центром антенны НИСЗ в момент времени T^*

Аналогичным образом выводится соотношение разности приращений дальности для второй ортогональной пары интерферометра

В соответствии с вышеизложенным разностям приращений дальностей - разностям хода радиосигналов между фазовым центром антенны спутника и фазовыми центрами антенн интерферометра в каждой взаимно-ортогональной базе, выражения (1) и (2) соответствуют разности измеренных на мерном интервале приращений фаз,
обусловленных доплеровским смещением частоты

где
cosθ_x,cosθ_y - направляющие косинусы.As noted above, the ranges R ₁ (t ^* ) and R ₃ (t ^* ) contain the projection of the path traveled by the phase center of the NHA antenna from point T ₁ to point T ₂ . Therefore, taking the difference in distances ΔR _1.3 (t ^* ) = R ₁ (t ^* ) -R ₃ (t ^* ), we find information on the projection of the difference in the path of the radio signals between the phase center of the N NSS antenna located at point T ^* and phase centers detectable object interferometer antennas

The double range difference ΔR _1.3 (t ^* ) - the difference in the range increments R (t) gives information about the projection of the base distance d ₁ between the phase centers of the antennas of the object An1, An3 on the direction of the line R (t ^* ) connecting the midpoint of the base with the phase NISS antenna center at time T ^*

In a similar way, the ratio of the difference in the distance increments for the second orthogonal pair of the interferometer is derived

In accordance with the aforementioned differences in the increments of ranges - the differences in the path of radio signals between the phase center of the satellite antenna and the phase centers of the antennas of the interferometer in each mutually orthogonal base, expressions (1) and (2) correspond to the difference of the phase increments measured on the measuring interval,
due to Doppler frequency shift

Where
cosθ _x , cosθ _y are the direction cosines.

,
где
X, Y, Z - известные координаты фазового центра антенны спутника;
X₀, Y₀, Z₀ - неизвестные координаты фазового центра антенны определяющегося объекта.The _direction cosines cosθ _x , cosθ _y , cosθ _z are the cosines of the angles between the segment R (t ^* ) connecting the middle of the base of the interferometer with the phase center of the NISS antenna and the positive directions of the axes OX, OY, OZ, respectively

,
Where
X, Y, Z - known coordinates of the phase center of the satellite antenna;
X ₀ , Y ₀ , Z ₀ - unknown coordinates of the phase center of the antenna of the detected object.

Navigation measurements using interferometers make it possible to implement an azimuthal method for determining the coordinates of the location of objects, a goniometric-rangefinder method using directing cosines, etc. The above are the functional dependencies between the known coordinates of the phase center of the NISS antenna and the known coordinates of the middle of the bases of the interferometer of the detected object through the direction cosines
ΔΔφ _1,3 (t) = Δφ ₁ (t) -Δφ ₃ (t),
Where
Δψ ₁ (t), Δψ ₃ (t) - phase increment due to Doppler frequency shift, measured using the signals of the first and third antenna-receiving devices.

 The difference in the travel of the satellite navigation radio signal received by the antenna-receiving devices by each mutually orthogonal pair of the interferometer is called the difference in the arguments of the sinusoidal or cosine function that describes this signal.

где t₁, t₃ - время распространения навигационного сигнала от фазового центра антенн НИСЗ до фазовых центров антенн АН1, Ан3 соответственно

F_y1, F_y3 - доплеровские сдвиги частот, принятые первым и третьим антенно-приемными устройствами соответственно;
f_н - несущая частота.In the general case, it contains several components due to various reasons. So, in the harmonic vibration of the form
u = Ucos [ωt + φ (t) + φ _beg ],
we have
ωt is a linearly increasing phase;
φ (t) is a deterministic or random function that displays the process of phase modulation or interference;
φ _nach - initial phase, i.e. phase at t = 0, φ (t) = 0.
In accordance with the above, the received satellite navigation signal by the first and third antenna-receiving devices of the interferometer can be described by the expressions:

where t ₁ , t ₃ - propagation time of the navigation signal from the phase center of the NISS antennas to the phase centers of the antennas AN1, An3, respectively

F _y1 , F _y3 - Doppler frequency shifts received by the first and third antenna-receiving devices, respectively;
f _n - carrier frequency.

 Carrier frequency - the frequency of harmonic oscillations, subject to modulation in order to transmit information.

The difference in the signal paths received by the antenna-receiving devices of the interferometer can also be measured by the phase difference of the carrier f _n , then knowledge of the components 2πF _d and the phase difference of the Doppler frequency shifts are required, then knowledge of the component 2πf _n is required.

Quadrature phase detector just those devices which allow the output without knowledge of f _n to obtain a phase increment due to the Doppler shift frequency corresponding to increments of distance between the antenna phase center and the SS flag interferometer antenna phase centers. Taking the mutual differences of the phase increments, determine the difference in the signal paths corresponding to expressions (1) and (2).

 In FIG. Figure 2 shows a block diagram of a device that allows one to measure the phase increments Δφ (t) due to Doppler frequency shift using the example of the operation of one antenna-receiving device for radio signals of the SRNS GLONASS, GPS. Transformed received signals are subjected to quadrature detection, in which phase modulation is removed by squaring and filtering, followed by returning to the original frequency. Amplitude modulation is removed using an amplifier-limiter.

 Figure 2 shows: 1, 6, 7 and 9 - voltage multipliers; 2,5 and 8 - low-pass filters; 3, 13 and 15 - phase shifters; 4 - tunable generator; 10 - band-pass filter; 11- amplifier limiter; 12-frequency divider; 14 and 17 are phase detectors; 16 - voltage adder; 18 - reference generator.

 At the same time, it is necessary to clearly understand that by squaring the received converted satellite radio navigation signals into a square and filtering them with subsequent return to the original frequency, one can distinguish both the carrier frequency, the definition of which is given above, and Doppler shifts.

 With the output of convolution devices for GLONASS, GPS satellite satellite signal receivers, the signals of which are fed to the PLL SSN fig. 2 in the synchronism mode for the delays of the rangefinder codes, are significantly narrow-band signals modulated by digital information. The range of variation in the values of the carrier frequencies is determined mainly by the Doppler shift (± 50 kHz), and the width of the signal spectrum by the spectrum of digital information (± 50 Hz). PLL systems can track signals corresponding to only one of the two sidebands, and therefore have an energy loss of 3 dB. The connection of the devices for separation from the received navigation signals of Doppler frequency shifts of the proposed method from the second side bands does not introduce additional energy losses. When implementing the proposed method for measuring range increments (phase increments), the SSN signals are not used. Therefore, in the measurements there are no errors due to CCH and inherent in the prototype.

Since the intrinsic noise of the receiving channels is independent, doubling the amplitudes of the total signals at the outputs of the quadrature phase detectors leads to a decrease in the potential dispersion of the phase samples by half. As a result, both the accuracy of radio navigation measurements and the accuracy of the navigation solution are improved.
Distinctive features of the proposed method:
separation of signals with Doppler frequency offset in the master and slave antenna receiving devices by squaring the received converted satellite radio navigation signals into a square, filtering them and removing amplitude modulation, followed by returning to the desired frequencies using frequency dividers;
measurement on the measured interval of phase increments due to Doppler frequency shift by using quadrature phase detectors, the first inputs of which receive signals with Doppler frequency shift, and the second inputs the signal of the reference generator;
determination of the difference in the path of the radio signals between the phase center of the satellite and the phase centers of the antennas of the interferometer as the difference of the phase increments measured on the measured interval due to the Doppler frequency shift.

 Thus, the proposed method for determining the heading angle and the coordinates of the location of objects from the radio navigation signals of the spacecraft of the satellite radio navigation systems has novelty, existing differences and gives a positive effect, which consists in improving the accuracy of navigation definitions.

Claims (2)

 1. The method of determining the heading angle and the coordinates of the location of objects from the radio navigation signals of the spacecraft of the satellite radio navigation systems, in which each of the four antenna-receiving devices installed on the object receive the navigation radio signals of the satellites, while the antennas of the four antenna-receiving devices form a rectangular coordinate system whose axes are parallel to the axes of the object, determine the pseudorange, determine the difference of the pseudorange by their mutual subtraction, determine location coordinates and heading angle, characterized in that each antenna receiving device simultaneously receives the navigation radio signal of the same satellite, determines the distance increment between the phase center of the satellite antenna and the phase centers of the interferometer antenna by measuring the phase increments due to Doppler shifts carrier frequency using phase locked loop systems, and determine the difference in increments of ranges in mutually orthogonal base x by subtracting the measured phase increments.  2. The method according to claim 1, characterized in that the range increments on the measured interval is determined by measuring the phase increments, highlighting the Doppler frequency shifts of the carriers by erecting the second side bands of the received and converted satellite navigation radio signals into a square, and then returning to the desired frequencies using frequency dividers and quadrature phase detectors, at the first inputs of which the signals of the desired frequencies are supplied, and at the second inputs the signal of the reference generator is fed, and the multiplication of the selected Doppler shifts gov frequencies on a measured interval.

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