RU2042145C1 - Direction finder - Google Patents

Abstract

FIELD: navigation. SUBSTANCE: direction finder has aerials 1-3, five switches 4, 5, 12, 31, 38, high frequency amplifier 6, frequency converter 7, restrictor 8, multiplying unit 9, read-out unit 10, counter 11, master oscillator 13, frequency by-two-divider 13, accumulator 15, clock oscillator 16, phase tuning channels 17-19, multipliers 20, 21, 24, adders 22, 23, 30, filter 25, transformed frequency oscillator 26, phase shift unit 27, squarers 28, 29, lower frequency filters 32, 33, standard oscillator 35, frequency multiplier 36, frequency divider 37, solving unit 37, phase meter 40, K irradiators 41(1)-41(K), K photodetectors 42(1)-42(K). EFFECT: improved precision of measurement; improved functional capabilities. 2 cl, 2 dwg

Description

 The invention relates to navigation and can be used to determine the direction of a moving object in space.

 A device is known that provides orientation information for an object, consisting of an antenna unit including a series of antennas, a controlled switch, an adder, and a receiver, the receiver consisting of a pseudo-noise modulation conversion unit, a phase synchronization and carrier tracking unit, a phase measurement unit, a decision unit, a unit antenna unit control. This device provides orientation of the object in space by measuring information about the phase shift of signals received from satellites of the navigation system.

 The disadvantage of this device is the low accuracy and the lack of the ability to automatically determine the health of the direction finder.

 Known direction finder containing at least two antennas.

 The aim of the invention is to improve the measurement accuracy and expand the functionality by automatically determining the health of the direction finder.

 In FIG. 1 shows a structural diagram of the proposed device; in FIG. 2 option for the location of antennas, emitters and photodetectors at the facility.

The direction finder contains antennas 1-3, the first switch 4, the fourth switch 5, the high-frequency amplifier 6, the frequency converter 7, the limiter 8, the multiplying unit 9, the reading unit 10, the counter 11, the second switch 12, a controlled generator 13, a frequency divider by 2 14, drive 15, clock 16, first 17, second 18 and third 19 phase adjustment channels, first phase adjustment channel 17 containing first 20 and second 21 multipliers, first 22 and second 23 adders, third multiplier 24, filter 25, transformed generator frequency 2 6, phase shift unit 27, quadrants 28 and 29, third adder 30, third switch 31, first 32 and second 33 low pass filters, generator control unit 34, reference generator 35, frequency multiplier 36, frequency divider 37, fifth switch 38, a decision unit 39, a phase meter 40, K emitters 41 ₁ -41 _k , K photodetectors 42 ₁ -42 _k .

 The second phase adjustment channel 18 comprises multipliers 20 and 21 ', adders 22' and 23 ', a multiplier 24', a filter 25 ', a frequency converter 26', a phase shift unit 27 '. The third channel phase adjustment 19 is made similarly.

 The device operates as follows.

 The signal emitted by the satellite, for example, Navstar signals, is received by antenna 1 and is supplied to frequency converter 7 via switches 4, 5 and high-frequency amplifier 6.

 In the frequency converter 7, the output signal is converted, for example, with a frequency of 1575 MHz to a 5 kHz signal. The converted frequency (5 kHz) is chosen so as not to reach a zero value at the maximum expected Doppler frequency shift, for example, for practicable Doppler frequencies, the converted frequency varies from 500 Hz to 9.5 kHz.

 The converted signal (5 kHz) is normalized by amplitude in the limiter 8 so that its output signal takes the value “1” when the threshold value is exceeded, or has the value “0” when the threshold level is not exceeded.

 As a threshold value, a zero amplitude value can be selected.

 A noise signal (interference) is superimposed on the carrier frequency signal received from the satellite and modulated by the data, the amplitude of which is significantly (more than 20 dB) greater than the amplitude of the modulated carrier signal. The amplitude-normalized signal from the output of the limiter 8 is fed to a multiplying unit 9, in which this signal is multiplied with a PRC code (precision code), read from drive 15 under the influence of a signal from the frequency divider by two 14. Then, the signal obtained from multiplication is selected in the reading unit 10 with doubled frequency from the generator 13.

 The signal obtained due to sampling in the reading unit 10 is supplied to the counter 11. In the absence of a carrier frequency signal from the satellite, the counting result in the counter 11 increases linearly, and in the presence of a carrier frequency signal at the direction finder input with or without a modulation, the time dependence of the counting result gives a line, the increase of which is alternately larger and smaller than the linear increase of the counting result in the absence of a carrier frequency signal. The obtained counting results are continuously received from the counter 11 through the switch 12 to two multipliers 20, 21. The multipliers 20, 21 also receive signals generated by the converted frequency generator 26, which are regular sequences of "+1" and "-1" . The frequency of the signal of the generator 26 is equal to the converted frequency (5 kHz) and may contain a Doppler shift. The signal for the multiplier 21 is shifted relative to the signal for the multiplier 20 by a quarter of the period of the converted frequency (5 kHz) in the phase shift unit 27. The output signals of the multipliers 20 and 21 correspond to the I and Q component signals and are used to obtain control signals.

-2Z

+Z(2π) (1) где слагаемые Z (.) являются текущими результатами суммирования для данных моментов времени.In the adders 22 and 23 for each period of the converted frequency (5 kHz) created in the generator 26, the accumulated total values in the form
I -Z (0) 2Z (π) Z (2π)
Q -Z (0) + 2Z

-2Z

+ Z (2π) (1) where the terms Z (.) Are the current summation results for the given time instants.

 In the multiplier 24, the total values of I and Q are multiplied and the resulting values are sent to the filter 25. The output signal of this filter 25, which can be made in the form of a low-pass filter, adjusts the frequency and phase of the signal of the converted frequency generator 26 so that its output signal equal in frequency and phase to the carrier signal transferred to the converted frequency (5 kHz). The multipliers 20, 21, 23, 24, the adders 22, 23, the filter 25, the generator 26 of the converted frequency 26 and the phase shift unit 27 form a known PLL control circuit. In the steady state, the sequence of values 1 output from the adder 2 reproduces a modulating signal from which data transmitted by the modulating signal from the satellite are obtained.

The values of I and Q are fed not only to the multiplier 24, but also to the squares 28, 29, in which these values are squaredI ^{2 +} Q ² | The squares of the values of I and Q are summed in the adder 30 and the total values (I ² + Q ² ), which are a display of the amplitude of the input signal of the carrier frequency of the device, are alternately supplied through the switch 31 to the low-pass filters 32, 33. Switching of the switch 31 is carried out with a clock the frequency with which the temporary position of the PRC code sample from the drive 15 is switched (for example, a frequency of 125 Hz). The output signals of the low-pass filters 32 and 33 are supplied to the control unit of the generator 34, in which the sums and differences of these values are calculated. The obtained values are used in the control unit of the generator 34 to determine the control signal that regulates the phase of the signal generated by the controlled generator 13. The signal of the generator 13 after dividing by two in the frequency divider 14 controls the selection of the PRC code from the drive 15 (for example, with a frequency of 125 Hz). The signal of the controlled oscillator 13 is, in addition, a clock signal for the reading unit 10. The phase adjustment of the signal is carried out so that the PRC code accumulated in the direction finder shows the same phase value as the PRC code of the received signal. The temporary position of the PRC code relative to the reference time of the direction finder will be proportional to the distance from the direction finder to the transmitting station (satellite) and transmitted to the evaluation device.

 The controlled generator 13, the frequency divider 14, the drive 15, the reading unit 10, the counter 11, the multipliers 20, 21, the adders 22, 23, the squares 28, 29, the adders 30, the low-pass filters 32, 33 and the control unit of the generator 34 form a control circuit . To implement this control circuit, in addition to the described signal, the signal output from the controlled generator 13 periodically (clock frequency 125 Hz) is tuned forward one clock cycle and comes back under the control of the generator control unit 34.

 In the Navstar system, each satellite is assigned a special precision code (PRC). For navigation, it is necessary to measure the distance to several satellites simultaneously. In the described device, this is due to temporary compaction as follows. The device must store PRC codes for the respective satellites. At time intervals equal to, for example, one millisecond, there is a switch from one PRC code to the next, and during these time intervals, adjustments are made in the tracking circuits. The phase matching of the control circuits with all selected satellites is preserved and demodulation of these signals applied from all satellites is possible continuously.

 In this device, the known interferometric principle is used to determine the direction. For its implementation, the phase of the received signal is measured in two places spatially remote from each other. Therefore, antennas 1, 2, 3 are provided in the direction finder. The distance between the antennas depends on the desired measurement accuracy, with an increase in this distance, the accuracy increases. Switch 4 connects to the high-frequency amplifier 6 antennas 1 either 2 or 3, which receive signals from the satellites of the Navstar system. The switch 12 switches the output signal of the counter 11 to the described PLL control circuit 17 or to the PLL control circuit 18. Both switches 4 and 12 are synchronously controlled from the clock generator 16. Thus, the output signal from the antenna 1 is supplied to the first control circuit 17, the output signal from antenna 2 to the second control circuit 18, and the output signal from antenna 3 to the third control circuit 19. The switching sequence is selected so that the signal of the control channels 7, 8 and 19 from the outputs of the converted frequency generators 26, 26 ' , 26 "remain in phase with the signals of the Navstar system supplied to them. Slight deviations during the disconnected state are corrected during the included time interval. The reasons for such deviations may be the movements of satellites and the object, the instability of the frequency of the direction finder generator.

 The construction of a direction finder, in which the signals from different antennas 1-3 passes through the same device blocks (4-12) sequentially in time, provides high accuracy in measuring the phase of the received signals, since the phase shifts in blocks 4-12 are the same for all channels ( 17, 18, 19) of the device.

 Since the output signal of the converted frequency generator 26 is in phase with the received antenna 1 and the conversion signal (5 kHz) of the Navstar system, and the output signal of the converted frequency generator 26 'is in phase with the received antenna 2 signal of the Navstar system, the difference phase φ of the output signals of the generators 26 and 26 'is determined according to the interferometric principle of the direction in space. The phase difference is measured in the phase meter 40 and then evaluated in the decision block 39. Depending on which direction should be measured (the angle between the row of antennas and the straight line from the antenna row to the satellite; direction in the coordinate system, etc.), block 39 serves additional satellite data and its own position. These data are always available in the consumer equipment of the Navstar system.

If it is necessary to determine the direction in three dimensional space, then it provides at least one linear series of antennas, which is preferably positioned at an angle ^of 90 to the first series of antennas. Moreover, one antenna can be common to both rows of antennas (see figure 2). Depending on the number of receiving antennas 1, 2, etc. the number of PLL control channels is selected (1, 2, etc.). Switches 4 and 12 are selected for the appropriate number of switching.

sinα (2) где λ длина волны принимаемых сигналов несущей частоты, например 1575 мГц;
α угол между направлением на спутник и нормалью к базе d, проходящей через ее середину;
d расстояние между антеннами 1 и 2, 1 и 3, называемое базой.From the measured value of the phase difference φ in the decision block 39, the direction in space can be determined from the formula
φ = 2π

sinα (2) where λ is the wavelength of the received carrier signals, for example 1575 MHz;
α is the angle between the direction to the satellite and the normal to the base d passing through its middle;
d distance between antennas 1 and 2, 1 and 3, called the base.

 It follows from expression (2) that the error in determining the direction in space α is proportional to the wavelength of the error; the measurement of the phase difference φ is inversely proportional to the distance between the antennas d. Moreover, an inaccurate value of the length of the base d leads to an error in determining the direction of α.

In order to increase the accuracy of measuring the direction to the satellite, a direction finder provides for automatic measurement of the distance d between antennas 1, 2, 3 with high accuracy. To this end, emitters 41 ₁ -41 _k and photodetectors 42 ₁ -42 _{k are} provided in the direction finder, the emitters and photodetectors being located on the antenna device so that radiation, for example, an emitter. 41 _{1 was} received by the corresponding photodetector 42 ₁ (see figure 2). For example, to measure the distance d ₁ between antennas 1 and 2, the emitter 41 ₁ is located near the antenna 1, and the photodetector 42 ₁ near the antenna 2, to measure the distance d ₂ between the antennas 1 and 3, the emitter 41 ₂ is located near the antenna 1, and the photodetector 42 ₂ about the antenna 3. In this arrangement, the emitters and photodetectors is no control over the change in the mutual position of one of a number of antennas (1 and 2) relative to another number of antennae (1 and 3) which are preferably arranged at an angle β ⁹⁰ °. Therefore, in order to determine the values of d ₁ and d ₂ , as well as to control the angle β, the emitters 41 ₁ -42 ₃ and the photodetectors 41 ₁ -42 ₃ should be placed on the antenna device in accordance with FIG. 2. Then, using the emitter 41 and photodetector 42 _{1 1 1} measured distance r, 41 of the radiator ₂ and the photodetector 42 a distance r _{2 2,} and ₃ of the radiator 41 and the photodetector 42 ₃ - distance r _3.

 In the automatic determination of the distances between antennas 1-3 according to the signal from the decision unit 39, the output of the frequency divider 37 is connected by a switch 38 to the second input of the phase meter 40.

(m+φ₁/2π) (3) где m целое число длин волн, укладывающееся на расстоянии r₁.The frequency of the output signal of block 37 is equal to the converted frequency of the direction finder (5 kHz) and is formed from the signal of the reference generator 35. It should be noted that the frequency of the output signal of the frequency multiplier 36 is chosen equal to the frequency of the Navstar system signal, for example 1575 MHz. The output signal of the frequency multiplier 36 is supplied to the inputs of the emitters 41 ₁ -41 _k and modulates the emitters 41 ₁ -41 _to high-frequency oscillations of the frequency of 1575 MHz. The modulated light fluxes arrive at the inputs of the respective photodetectors 42 ₁ -42 _k , having passed the corresponding distances r ₁ -r _k from the emitter to the photodetector. Photodetectors 42 ₁ -42 _k convert the input modulated light fluxes into output electrical signals with a frequency of 1575 MHz, which are fed to the inputs of switch 5. According to the signals from the deciding unit 39, the output of photodetector 42 _{1 is} connected by switch 5 to the input of high-frequency amplifier 6, while the signal the output of the photodetector 42 _{1 with a} frequency of 1575 MHz, passing through switch 5, the high-frequency amplifier 6 is supplied to the frequency converter 7. In the frequency converter 7, the input signal with a frequency of 1575 MHz is converted to l frequency of 5 kHz. Further, the device operates in accordance with the above, as in the presence of an unmodulated signal of the Navstar system at the input. The output signal of the generator of the converted frequency 26 (5 kHz) of the control circuit 17 is in phase with the signal from the photodetector 42 ₁ and is fed to the first input of the photo meter 40, the second input of which receives a signal from the frequency divider 37 (5 kHz). Then the result of measuring the phase shift of the phase meter 40 is determined by the distance between the emitter 41 ₁ and the photodetector 42 ₁ and are related by the formula
r ₁

(m + φ ₁ / 2π) (3) where m is an integer number of wavelengths that fit at a distance r ₁ .

Thus, the measurement of φ ₁ in the direction finder allows you to determine the desired distance r ₁ . Then, according to the control signals from the decision block 39, the output of the photodetector 42 _{2 is} connected by a switch 5 at the input of the high-frequency amplifier 6, while the output signal of the converted frequency generator 26 (5 kHz) of the control circuit 17 is in phase with the signal from the photodetector 42 ₂ (frequency 1575 MHz) and is fed to the first input of the phase meter 40. Then the result of measuring the phase shift φ ₂ in the phase meter 40 is determined by the distance r ₂ between the emitter 41 ₂ and the photodetector 42 ₂ in accordance with formula (3). Further, according to the control signals from the decision unit 39, the input of the photodetector 42 _{3 is} connected to the input of the high-frequency amplifier 6.

As a result, the phase shift φ ₃ is measured in the direction finder by the formula (3) in the decision block 39, the distance r ₃ between the emitter 41 _{3 of the} photodetector 42 _{3 is} determined.

; d₂=

; β₁=arctg

β₂=arctg

β=β₁+β₂ (4)
Величины d₁, d₂, β используются в решающем блоке 39 для высокоточного определения ориентации объекта в пространстве с учетом дополнительных спутниковых данных собственного положения.If the emitters 41 ₁ -41 ₃ and the photodetectors 42 ₁ -42 ₃ are placed on the antenna device in accordance with figure 2, then the measured values of d ₁ , d ₂ are calculated from the measured distances r ₁ -r ₃ in the solving unit 39 β by the formulas
d ₁ =

; d ₂ =

; β ₁ = arctg

β ₂ = arctg

β = β ₁ + β ₂ (4)
The values of d ₁ , d ₂ , β are used in the decision block 39 for high-precision determination of the orientation of the object in space, taking into account additional satellite data of its own position.

 The described mode of measuring the distance d can be performed before the direction finder starts, and is also repeated automatically with a given cycle.

In addition to the described arrangement of emitters and photodetectors, in order to determine the distances d ₁ and d ₂ , the emitter and the corresponding photodetector can be installed at one point of the antenna device, for example, at antenna 1, while the surface of antenna 2 can serve as a signal reflector. Then the phase shift measured by phase meter 40, will correspond to twice the distance, for example, d ₁ , through which the emitted signal passes.

 Improving the accuracy of measuring information parameters of the direction finder is achieved through automatic high-precision determination of the distances between spaced antennas 1, 2, 3.

Claims (2)

 1. DIRECTOR comprising three receiving antennas, each of the two antennas being located on one straight line and connected to the corresponding inputs of the first switch, a high-frequency amplifier, a frequency converter, a limiter, a multiplying unit, a reading unit, a counter and a second switch connected in series controlled generator, frequency divider into two and a drive, the output of which is connected to the second input of the multiplying unit, the output of the controlled generator is connected to the second input with a washing unit, also containing a phase meter, the output of which is connected to the first information input of the decision block, the second input of the decision block is the input of the information signal about its own position, the third input is the decisive input of the information signal of satellite data, a clock generator, the first output of which is connected to the control input of the first switch , the second output with a control input of the second switch, also containing three channels of phase adjustment, by the number of direction finding antennas, each the phase adjustment channel contains the first and second multipliers, the inputs of which are connected to each other and are the first inputs of each channel, each of which is connected to the corresponding output of the second switch, the outputs of the first and second multipliers of each phase adjustment channel are connected to the inputs of the first and second adders, respectively, when the outputs of each adder are connected to the corresponding inputs of the third multiplier, the output of which is connected to a filter, the output of which is connected through series the converted frequency generator and the phase shift unit are connected to the second input of the second multiplier, the output of the converted frequency generator is also connected to the second input of the first multiplier, the outputs of the first and second adders of the first phase adjustment channel are connected through the corresponding first and second quadrators with the inputs of the third adder, the output of which connected to the input of the third switch, the first and second outputs of which are connected respectively through the first and second low-pass filters associated with the first and second inputs of the generator control unit, the output of which is connected to the input of the controlled generator, the output of the converted frequency generator of the first phase adjustment channel is connected to the first input of the phase meter, characterized in that the fourth and fifth switches, a reference generator, a frequency multiplier are inserted into it, frequency divider, K emitters and K photodetectors, while the outputs of K photodetectors are connected to the corresponding K inputs of the fourth switch, the (K + 1) -th input of which is connected to the output of the first switch, (K + 2) -th input with the output of the deciding unit, the output with the input of the high-frequency amplifier, the first and second inputs of the fifth switch are connected respectively to the outputs of the converted frequency generators of the second and third channels of phase adjustment, the third input with the output of the frequency divider, the fourth input with the output of the deciding unit, the output with the second input of the phase meter, the output of the reference generator is connected to the inputs of the frequency divider and frequency multiplier, the output of which is connected to the inputs of K emitters, the output of each of which connected to the input of the corresponding photodetector.  2. The direction finder according to claim 1, characterized in that the three receiving antennas are located at the vertices of an isosceles right triangle, and the emitters are in the middle of the base of the triangle and are directed toward the corresponding receiving antenna.

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