RU2325670C1 - Radio range finder - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: design of the radio range finder for single valued measurement of small and extremely small distances under conditions of various noise, is achieved through a transmitter unit of noise signal, circulator, transceiver antenna, mixer, first narrow band pass filter, first frequency detector, second frequency detector, first inverter, first NAND element, memory element, second inverter, matching element, resolution device, second NAND element, third inverter and execution circuit, connected in a defined way.

EFFECT: reliability of single valued measurements of small distances in the immediate vicinity of objects and under conditions of various noises.

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Description

The proposed radio range finder belongs to the radar measuring technique and is mainly intended to solve the problems associated with the need to unambiguously measure small and ultra-small distances, calculated from a few meters to fractions of a meter (Note: by small and ultra-small we will mean distances commensurate with the resolution radio signal range).

The requirement for an unambiguous range measurement in the immediate vicinity of relatively moving objects (targets) arises in many practical cases. So, for example, such a measurement is necessary at the final stages of controlling the movement of short-term interacting objects when meeting aerospace objects for the purpose of docking, emergency assistance, controlling the mechanism of the object itself to achieve the final goal - bringing docking devices into operation, starting brake engines, issuing commands telemetry system, etc. (see Kogan I.M. Near Radar (Theoretical Foundations). M: Sov. Radio, 1973, 272 pp.).

The problem of unambiguous range measurement in the immediate vicinity of targets arises, for example, in the systems of protection and protection of objects and structures from unauthorized approximations.

In industrial production, when solving a number of technological processes, there are many tasks of remote assessment of the distances between movable tooling devices (for example, in rolling and metallurgical production).

Known radio devices for measuring relatively small distances. However, the solution of the problem of unambiguous range measurement in the immediate vicinity of an object cannot be performed by any of the existing radio range finders, since when measuring the speed of movement of an object of observation they do not have unambiguous selection along the range of the desired object (target) if they use an unmodulated probe signal , and in the presence of modulation of the probing signals (for example, pulse), the so-called "Dead zone", the value of which is often comparable or even exceeds the value of the measured range. Radio range finders, which use periodic frequency modulation of the probing signals, also have an ambiguity in the assessment of the measured range (see Kogan I.M. Near Radar (Theoretical Foundations). M: Sov. Radio, 1973, pp. 29-35).

An important requirement for such radio range finders is their noise immunity to all active and passive (intentional or random) interference, often resulting from the operation of others as radio engineering and electrical devices located in close proximity to an interacting object.

So the main problem arises of creating a radio range finder for the unambiguous measurement of small and ultra-small distances under various interference conditions.

To radio range finders, which have an unambiguous range reference within a certain fixed range of distances and which have a relatively high noise immunity to various external interference, is a radio device with a continuous noise sounding signal [see 1) see Varakin L.E. Theory of complex signals. M .: Sov. Radio, 1970. 2) Radar devices (theory and principles of construction). Ed. V.V. Grigoryan-Ryabov, Moscow: Sov. Radio, 1970, 680 pp.].

Radio rangefinders are known in which the processing of the noise signal is carried out in a correlation way, and the distance to the center of the measured range is determined by the delay of the signal in the heterodyne path of the correlation receiver [see 1) Kogan I.M. Near radar. M .: Sov. Radio, 1973, p.29-35. 2) US patent No. 3.614.782, MKI GOIS 42C 13/04; NKI 343-7RG, 102-70.2g for 1971].

Of the known closest in technical essence is a radio device with a noise signal described in US patent No. 3.419.861, class. 343-7, claimed 06/26/56, published. 12/31/68. This radio device contains a transmitter emitting a noise signal of the “white noise” type, a transceiver antenna, a circulator, a mixer, a delay line, a narrow-band filter, and an executive circuit.

The mixer, delay line, narrow-band filter form a correlator, at the output of which the maximum signal level will be determined by the position of the object at a distance proportional to the value of the delay line, because only in this case the reflected and reference noise signals arriving at the mixer will be maximally correlated. When the radio range finder encounters a moving object, an echo signal with a Doppler frequency shift arrives at the input of the mixer along with a reference signal (heterodyne) delayed in the delay line. A narrow-band filter at the mixer output transmits signals in the Doppler frequency range. When a moving object appears at a distance corresponding to the set delay line, the output signal of the filter triggers the actuation circuit. However, to measure small and super small distances, the delay line in the heterodyne path of the mixer should be absent.

The main drawback of all such structural schemes is the limitation of the lower boundary of the measured range, which arises both from the influence of the active signal leaking into the receiver from the transmitting path (the so-called decoupling signal), and due to the interference received from other sources at the input of the receiver, including from various reflections of closely spaced vibrating surfaces of the carrier itself of a radio device or technological equipment.

The isolation signal is caused both by the proximity of the receiving and transmitting antennas (or by combining the reception and transmission of a signal with one antenna), and by the weak isolation of individual elements of the transmitting and transmitting path, for example, a circulator. This disadvantage in the correlation receiver manifests itself especially when measurements are made of such small distances at which the signal delay line in its local oscillator path should be absent.

In the presence of interference and the absence of a delay line, taking into account the noise character of two signals - one heterodyne, and the second - reflected, they become correlated with each other, even when the observation object is absent. In this case, the so-called spurious signal, the level of which may be sufficient for false operation of the actuator circuit of the radio range finder.

The weakening of the influence of spurious signals, of course, can be carried out along the path of eliminating the sources of their occurrence, which in real devices of limited size is quite difficult to perform or, most often, almost impossible.

Figure 1 shows several types of signals at the output of the correlation receiver of a radio range finder with a noise sounding signal depending on the distance to the reflecting surface: in the presence of a signal delay in the heterodyne path, in the absence of a signal delay in the heterodyne path, when interference signals are received at the receiver input. If the heterodyne path DME set value τ _ro delay line, then the maximum signal level at the output of the correlator will then, when an object is at a distance R ₀ (see FIG. 1, position 1), i.e. then, when the delay time of the signal reflected from the observed object corresponds to the delay of the signal by the delay line in the heterodyne path

,

,

where c is the propagation velocity of the radio wave.

1, the reference numeral 1, it is shown that in the presence of delay line in the heterodyne signal path at time τ _ro maximum correlation signal at the receiver output will be at a distance R ₀ and the selected values of the probing signal spectrum width Δf and threshold triggering signal - U _cp , the range resolution element is characterized by the value - ΔR, determined by the formula

Without the influence of spurious signals, which were discussed above, and in the absence of a delay line in the heterodyne path, the shape of the output signal could be the same as in the first case, but shifted towards decreasing the distance, for example, to R _cp1 , as this is shown in figure 1, position 2. However, the presence of spurious signals with a level not lower than the threshold (U _cp ) leads to the appearance at the output of the mixer of the receiver of the signal sufficient for false operation of the actuator at any distance, determined by the presence at the input of the receiver ka interference signal (figure 1, position 3). So, for example, if the operating range R _{cp1 is specified} , however, the actual operation can occur at a different, greater distance, for example, R _cp2 , which indicates the fundamental impossibility of the prototype radio range finder to operate under interference only at a given distance R _cp1 less than R _cp2 due to the fact that at a greater distance at the output of the correlator due to the presence of interference, the signal can reach a level sufficient to issue a false executive command.

The technical result of the implementation of the proposed radio range finder is the reliability of an unambiguous measurement of small distances under various interference conditions.

The technical result is achieved by the fact that for measuring small distances under the influence of various interference in a radio range finder containing a noise signal transmitter, a circulator, a transmitting and receiving antenna, a mixer, a first narrow-band filter, an executive circuit, a second narrow-band filter, two frequency detectors, two inverters are introduced , two NAND elements, a storage device, a coincidence device, a resolution device.

The noise signal transmitter connected to the first input of the circulator, the second input of which is connected to the transmit-receive antenna, the output of the circulator is connected to the signal (first) input of the mixer, the local oscillator (second) input of which is connected to the output of the noise signal transmitter, the output of the mixer is connected to the inputs of two narrow-band filters, the outputs of which are connected to the inputs of two frequency detectors, the output of the first of them is connected to the input of the first inverter and to the first input of the second NAND element, the output of the second frequency detector connected to the second inputs of the first NAND element and the second NAND element, the output of the first inverter is connected to the first inputs of the first NAND element and the coincidence device, the output of the first NAND element is connected to the first input of the storage device, the output of the second And element NOT connected to the second input of the resolution device, the output of which is connected to the second input of the matching device, the second input of the storage device and the first input of the resolution device are connected to the terminal to which the “start” command is sent in the form of a single of the left pulse, the output of the storage device is connected to the third input of the coincidence device, the output of which is connected to the second inverter and the executive circuit connected in series.

Figure 2 presents the structural diagram of the proposed radio range finder, which indicates:

1 - transmitter noise signal,

2 - circulator

3 - transmit-receive antenna,

4 - mixer

5 - the first narrow-band filter

6 - second narrow-band filter,

7 - the first frequency detector,

8 - second frequency detector,

9 - the first inverter,

10 - the second element AND NOT,

11 - the first element AND NOT,

12 is a resolution device,

13 is a storage device,

14 - match device,

15 - second inverter,

16 is an executive diagram.

The radio range finder contains a noise signal transmitter 1, a circulator 2, a transmit-receive antenna 3, a mixer 4, a first narrow-band filter 5, a second narrow-band filter 6, a first frequency detector 7, a second frequency detector 8, a first inverter 9, a second AND-NOT 10 element, the first NAND element 11, a resolution device 12, a storage device 13, a matching device 14, a second inverter 15, an executive circuit 16. The proposed taxiway operates as follows.

By the command to turn on the radio range finder, a single zero pulse is supplied to the “start” terminal, which ensures the readiness of the radio range finder circuit for operation, and the signal processing elements are set to the initial state. The radio range finder is brought to its initial state in advance, then when the object (target) is either absent altogether or it is at a distance incommensurably greater than that required for measurements.

The noise signal transmitter 1 through the circulator 2 and the transmit-receive antenna 3 emits a wide-band noise signal (with deviation Δf _c ) into space and, if there is a target, the signal, reflected from it, enters through the transmit-receive antenna 3 to the input of the mixer 4, which has quadratic characteristic. As a result of the conversion in the mixer 4 of two signals (reflected and heterodyne, received at the mixer heterodyne input from the transmitter), its output will have a beat signal consisting of a set of frequency components due to both the band of the probe noise signal Δf _c and the delay of the signal reflected from the target relative to the emitted (heterodyne) by the value of τ so that when the distance to the target R, the delay of the reflected signal will be equal to

where c is the propagation velocity of the radio wave.

In the initial state, the signal from the target does not arrive at the input of the antenna 3 and it is not at the output of the mixer 4. At this time, at the inputs and outputs of two narrow-band filters 5 and 6, as well as at the outputs of the frequency detectors 7, 8, the signal is also absent, the signal absent at two inputs of the second element AND-NOT 10, and a logic zero is supplied to the input of the inverter 9; the logical unit appears at the output of the second AND-NOT 10 element; a logical unit appears at the output of the first AND-NOT 11 element, and a logical zero is set at the output of the resolution device 12 and the storage device 13 with the “start” command; at the output of the first inverter 9, a logical unit appears. Therefore, in the initial state, the logical unit arrives at the first input of the match device 14, and a logical zero arrives at its second and third inputs, as a result of which a logical unit arrives at the input of the second inverter 15, the output of which will be a logical zero, at the input of the Executive circuit 16 signal will not.

We give a more detailed explanation of the nature of the signal at the output of the mixer 4.

If we assume that the amplitude of the emitted signal is constant, and the frequency varies randomly ω ₀ + ω _f (t), then the probing signal can be represented in the form (see, for example, V. M. Svistov. Radar signals and their processing. M .: Sov. Radio, 1977, p. 310-314).

where ω _f (t) is a random function.

Then, when the target moves relative to the radio range finder, the received signal differs from the emitted (i.e., heterodyne, as reference) signal not only by the time delay by τ, but also by the Doppler frequency shift by Ω _d and can be represented as

where φ ₁ is a constant value (phase);

U _mc is the amplitude of the received signal.

After conversion in a quadratic mixer at its output, it is possible to select a signal of the form using narrow-band filters

where φ ₂ is a constant value (phase).

If we take into account that the spectrum can be described by the Fourier transform (see V.I. Tikhonov Static Radio Engineering. M: Sov. Radio, 1966, p. 85) of the form

it becomes clear that the frequency components of the converted signal are substantially dependent on the range and the law of frequency change.

Since the transmitter of the noise signal 1 emits a variable frequency signal according to a random (noise) law, the converted signal is characterized by a sinusoidal Doppler frequency signal with a random phase. If we assume that the distance R = 0, and therefore, τ = 0, then the signal converted in the mixer becomes harmonic with a frequency equal to the frequency of the Doppler shift.

Provided that there is a distance to the target, i.e. τ ≠ 0, the frequency (phase) of the signal at the mixer output fluctuates randomly and the greater, the greater the distance R, since τ proportionally increases. Therefore, different ranges correspond to their own upper frequency of the converted signal, and the lower frequency component of this signal is the Doppler frequency Ω _d , due to the approach speed of the radio range finder and the target V _sb and the transmitter wavelength, so

Using narrow-band filters, individual components of the converted signal frequencies are extracted.

If the interaction of the radio range finder and the target should be carried out at small and super short distances, then the signal delay due to the presence of spurious surfaces (for example, the intrinsic surface of the carrier of the radio range finder or other passive interference) or the leakage of a signal from the transmitting path to the receiving can cause the signal a level sufficient for the actuating circuit to operate, and the signal frequency corresponding to the transparency band of the narrow-band filter may be due to lenn parasitic phenomena (for example, vibration - the so-called vibration interference, or the movement of the carrier of the radio range finder under various passive interference, etc.). However, in this case, in the proposed radio range finder, the actuation circuit 16 will not occur. We show this by further consideration of the operation of the proposed radio range finder.

Let us consider possible situations in the presence and absence of a target under interference.

1. If there is a target, when the radio range finder is approaching it, then at a certain distance, for example, R _cp2 , greater than that necessary for actuating the actuating circuit (if the necessary distance for giving the command is, for example, R _cp1 , see _figure 1) , at the output of the first narrow-band filter 5, tuned to a frequency higher than the second narrow-band filter 6 and at the output of the second narrow-band filter 6, signals appear which, passing through the frequency detectors 7 and 8, cause voltage proportional to the frequency at their outputs m narrow-band filters. Thus, the use of frequency detectors, in addition to solving the main problem in this circuit - converting frequency to voltage, eliminates the influence of amplitude fluctuations of the output signals as a result of possible fluctuations of the effective scattering surface (EPR) of the targets.

From the output of the first frequency detector 7, the signal is fed to the input of the first inverter 9, as well as to the first input of the second AND-NOT element 10. From the output of the second frequency detector 8, the signal is fed to the second input of the first AND-NOT element 11 and to the second input of the second AND element -NOT 10, which determines the range boundaries from the moment the signals appear at the outputs of the frequency detectors 7 and 8 until the signal disappears at the output of the second frequency detector 8 as a result of the proximity of the range finder with the goal up to the distance R ₁ (from figure 1 it follows that R ₁ < R ₂ ), in which the upper frequencies of the resulting signal (beats) at the output of the mixer 4 become lower than the resonant frequency of the second narrow-band filter 6 (especially the first narrow-band filter 5). The following algorithm is formed by the operation of the second AND-NOT 10 element: the signal from the target must first appear on two inputs of the second AND-NOT 10 element, and then disappear sequentially, first at its first input, and then at the second. The moment the signal disappears at the second input of the second AND-NOT 10 element will characterize the achievement of a given range to the target and the moment the command was issued to trigger the actuating circuit 16.

So, at the initial moment of time, after the signal from the target appears at the outputs of two frequency detectors 7, 8, a logical zero will appear at the output of the second AND-NOT 10 element, which goes to the second input of the resolution device 12. A logical unit appears at the output of this device, which in the future it will be a constant value for any subsequent values of the signals at the second input of this device; a logical zero will appear at the output of the first inverter 9, a logical unit will appear at the output of the first AND-NOT 11 element, which is fed to the first input of the storage device 13, the output of which is a logical zero, fed to the third input of the matching device 14, the second input of which is output the resolution device 12 receives a logical unit, as a result of which the logical unit remains on the inverted output of the matching device 14, which, through the second inverter 15, supplies a logic zero to the input of the executive circuit 16, n not causing it to trigger. With the further approach of the radio range finder to the object, with a change in the distance between them, the upper frequency of the resulting signal at the output of the mixer 4 decreases. When this decrease becomes lower than the tuning frequency of the first narrow-band filter 5, then there will be no signal at its output and at the output of the first frequency detector 7. At this time, a logical zero will appear at the first input of the second AND-NOT 10 element and at the input of the first inverter 9, and the signal will continue to flow to the second inputs of the second AND-NOT 10 element and the first AND-NOT 11 element as a logical unit. As a result, the logical unit appears at the output of the second AND-NOT 10 element, the logical unit arrives at the output of the first inverter 9, which is fed to the first input of the first AND-NOT 11 element, at the output of which a logical zero appears and fed to the first input of the storage device 13, as a result, at its output, a logical zero continues to be received at the third input of the coincidence device 14, and at its output there remains a logical unit that is fed to the input of the second inverter 15, as a result of which at its output and and input circuit executive 16 will not signal without causing its actuation. With further approach of the radio range finder to the object by reducing the distance with the aim that the delay of the reflected signal turns out to be so small that the upper frequency of the converted signal at the output of the mixer 4 becomes lower than the tuning frequency of the second narrow-band filter 6, then its output, and therefore, there will be no signal at the output of the second frequency detector 8, just like there will be no signal at the outputs of the first narrow-band filter 5 and frequency detector 7. In this case, the first and second inputs of the second AND-NOT 10 element Torah input of the first AND-NO element 11 and to the first inverter input 9 receives a logical zero. As a result of this, at the output of the second AND-NOT element 10, a logical unit signal appears, which is fed to the second input of the resolution device 12, from the output of which the logical unit signal continues to be fed to the second input of the matching device 14. At the output of the first inverter 9, a logical unit signal remains to the first input of the first AND-NOT element 11, as a result of which a logical unit appears at its output, fed to the first input of the storage device 13, at the output of which a logical unit arrives I go to the third input of matching device 14. The logical unit of the output of the first inverter 9 continues to come to the first input of matching device 14.

Thus, the logical unit signals are received at the three inputs of match device 14, as a result of which a logical zero appears at its output, which is fed to the input of the second inverter 15, from the output of which the logic unit signal is input to the executive circuit 16, and, as a result, causing its operation.

2. In the presence of interference, when the target is absent, there may be situations:

- there are interference due to poor isolation of the transceiver path and false reflections;

- there is intentional active interference.

Consider the work of the proposed radio range finder in each interfering situation separately.

2.1. The situation of interference due to poor isolation of the transceiver path and false reflections.

As discussed above, interference caused by weak isolation of the transceiver path and reflections from a false surface (for example, from the surface of the carrier of a radio range finder) can create a signal at the output of the correlation receiver (at the output of a narrow-band filter) only if the narrow-band filter is tuned to the frequency , which may occur as a result of vibration of the reflection surface or as a result of vibration of the entire radio range finder, which causes the so-called vibrational noise in the transceiver path, and the isolation signal in level is quite large. If the narrow-band filters 5 and 6 are configured in such a way that their average frequencies are higher than the resonant frequency of oscillations (vibrations) of the reflecting surface, then there will be no interference signal at the output of the narrow-band filters 5 and 6, there will be no signal at the output of the frequency detectors 7 and 8. Then the initial (initial) situation is created, which was considered earlier in the paragraph describing the operation of the radio range finder in the absence of a signal at the outputs of two frequency detectors 7, 8. Without repeating itself in considering the state of the entire circuit, we note that the input will execute There will be no signal circuit 16, which ensures the failure of the radio range finder from the influence of the isolation signal and the presence of reflections from reflections of extraneous vibrating surfaces.

2.2. The situation in the presence of active interference.

If there is active interference at the output of the narrow-band filter of the correlation radio range finder with a noise sounding signal, there will be no signal, because the active interference signal will not be correlated with the reference (heterodyne) noise signal, and the degree of protection against active interference of the correlation receiver with the noise signal depends on the complexity of the noise signal (see, for example, L. Varakin, Theory of complex signals. M .: Sov Radio, 1970).

Thus, the previously considered situation arises in which there is no signal at the output of two narrow-band filters 5, 6, and, therefore, at the output of two frequency detectors 7 and 8, as a result of which the actuating circuit 16 will not operate.

The considered work of the proposed scheme of the radio range finder shows the actual attainability of the goal: it provides an unambiguous measurement of small and ultra-small distances and provides noise immunity of the radio range finder due to the use of a noise signal in it.

The practical implementation of the proposed radio range finder can be carried out using well-known analog elements and integrated circuits (see Integrated circuits. Handbook. / Under the general editorship of B.V. Tarabrin. M: Sov. Radio, 1984):

Inverters - K155 LN1;

Elements NAND - K155 LAZ;

Resolution device - K155 TM2;

The storage device - K155 TM2;

Coincidence device - K155 LA4.

By introducing the proposed new elements and the relationships between them, the problem of creating radar range finders for measuring small and ultra-small distances with increased accuracy under various interference conditions is fundamentally solved in a new way.

The manufactured and tested model of the proposed radio range finder showed its full performance under the conditions of the above interference. The tests were carried out in laboratory and full-scale conditions for the interaction of a radio range finder with an aircraft.

Information sources

1. Kogan I.M. Near radar (theoretical basis). M .: Sov. Radio, 1973, 272 p.

2. Varakin L.E. Theory of complex signals. M .: Sov. Radio, 1970.

3. Radar devices (theory and construction principles). / Ed. V.V. Grigoryan-Ryabov, Moscow: Sov. Radio, 1970, 680 p.

4. US patent No. 3.614.782, MKI GOIS 42C 13/04; NKI 343-7RG, 102-70.2 g for 1971

5. US Patent No. 3.419.861, cl. 343-7, claimed 06/26/56, published. 12/31/68 (prototype).

Claims (1)

A radio range finder containing a noise signal transmitter, a circulator, a transceiver antenna, a mixer, a first narrow-band filter, an executive circuit, characterized in that a second narrow-band filter, two frequency detectors, two inverters, two NAND elements, a memory device, a matching device are introduced , a resolution device, wherein the noise signal transmitter is connected to the first input of the circulator, the second input of which is connected to the transceiver antenna, the output of the circulator is connected to the signal input of the mixer, get the non-linear input of which is connected to the output of the noise signal transmitter, the mixer output is connected to the inputs of two narrow-band filters, the outputs of which are connected to the inputs of the corresponding two frequency detectors, the output of the first of them is connected to the input of the first inverter and to the first input of the second NAND element, the output of the second the frequency detector is connected to the second inputs of the first and second AND-NOT elements, the output of the first inverter is connected to the first inputs of the first AND-NOT element and the coincidence device, the output of the first AND-NOT element is connected is connected to the first input of the storage device, the output of the second NAND element is connected to the second input of the resolution device, the output of which is connected to the second input of the matching device, the second input of the storage device and the first input of the resolution device are connected to the terminal to which the “start” command is sent to in the form of a single zero pulse, the output of the storage device is connected to the third input of the coincidence device, the output of which is connected to the second inverter and the executive circuit connected in series.

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