RU2725160C1 - Hydroacoustic signals optimum receiver - Google Patents

Abstract

FIELD: radio equipment.SUBSTANCE: invention relates to radio engineering and sonar and can be used in hydroacoustic equipment for receiving weak hydroacoustic signals. Optical wavelength range and a set of fiber-optic components are used to filter electric signals: transmitting and receiving optoelectronic modules, optical splitters / couplers and fiber-optic delay lines.EFFECT: technical result consists in improvement of reliability, efficiency of filtration and expansion of operating frequencies range.1 cl, 1 tbl, 2 dwg

Description

The invention relates to radio engineering and sonar and can be used in sonar equipment for receiving weak sonar signals of the following types [1]:

- simple bandpass signals, for which F⋅T≈1, where F is the signal strip, T is the signal duration;

- complex phase-manipulated (FM), in which the phase (0 or π) changes according to a given law;

- complex, representing radio pulses with a wide range of frequencies (in particular, such signals include signals whose frequency varies according to the linear law (LFM) and discrete frequency signals (DF)).

A device is known for optimal filtering of phase-shifted signals [2], comprising N phase shifters, 2N amplitude limiters, 2N compression filters for FM signals, N amplitude detectors and N - input MAX selection circuit.

The essence of this technical solution lies in the fact that the input FM signal is distributed between N quadrature channels. Using a sampling circuit, a signal with a maximum amplitude is selected, this signal is taken as reliable.

The disadvantages of the proposed technical solutions are the following:

- the selection of the useful signal is not reliable, but probabilistic in nature;

- there is no accumulation of a useful signal against a background of noise;

- the difficulty of the technical feasibility of compressive filters for FM signals of sound and ultrasonic frequency.

Another device is known that implements optimal filtering of FM signals [3]. The device implements the method proposed by the author for processing the M - positional Barker signal when it is detected.

The Barker signal is a sequence of closed radio pulses having the same frequency and duration, the phases of which (0 or π) change according to a given law [4].

The device contains an input auxiliary filter, a multi-tap delay line, with the number of taps equal to M-2, the time delay between the taps is equal to the duration T of each signal position, M adders implementing the summing operation modulo 2, M elements of the reference signal, M inverters and the output adder inverter signals.

The essence of this technical solution lies in the fact that the radio pulses are fed to the delay line with taps, the delay between taps is equal to the duration T of each signal position. The selected signals are summed modulo two with the reference signals and converted into amplitude-manipulated (0 or 1) signals that accumulate in the adder of the output signals of the inverters.

The disadvantages of the proposed technical solutions are the following:

- the need for a reference signal generator in the receiver, for sonar equipment, as a rule, the transmitter and receiver are separated in space;

- the difficulty of realizing the delay line for several microseconds for signals of sound and ultrasonic frequency.

For hydroacoustic signals, a delay line of up to several hundred microseconds is required, operating in the frequency range from several kHz to several hundred kHz [1]. Acoustic-electric delay lines having the following parameters allow delaying electrical signals for several hundred microseconds for a time [5, 6]:

- at body waves (including hypersonic): frequency range from units to hundreds of MHz, delay up to 4 ms, losses up to 70 dB, false signal level up to minus 26 dB;

- on surface acoustic waves: frequency range from units to hundreds of MHz, delay up to 200 μs, loss up to 50 dB;

- waveguide: frequency range from 10 to 15 MHz, loss up to 40 dB.

That is, such lines operate at frequencies of at least 10 MHz. Sonar equipment needs a lower frequency range. In addition, losses in such delay lines are up to 40-70 dB.

Other delay lines of electrical signals for a few hundred microseconds are delay lines made on integrated circuits [7].

Analog delay lines are performed on the basis of LC lines or discrete-analog devices, including devices of the type: "fire chains", with charge coupling and on the basis of switched capacitors.

The disadvantages of such delay lines include:

- high complexity, therefore low reliability, so the microcircuit used to build delay lines based on switched capacitors, type KR1016BR1 contains over 10 thousand integral elements, the mean time between failures is 25,000 hours;

- nonlinearity of the phase characteristic.

The closest in technical solution to the proposed invention is a device (optimal receiver - drive) presented in [8].

The structural diagram of the receiver - drive shown in figure 1.

The receiver-drive contains a four-terminal 1 with a transmission coefficient K ₁ (ω) (preamplifier), the output of which is connected to a multi-tap delay line 2, n - of which are connected to n inertia-less four-terminal 3, the outputs of which are connected to the adder 4.

Receiver - drive works as follows. The input of the four-terminal 1 receives n - positional sequence of radio pulses.

The bandwidth of the quadrupole 1 corresponds to the spectrum of this sequence of radio pulses. All radio pulses have the same frequency and duration, the initial phases of the radio pulses (0 or π) change according to a given law.

From the output of the four-terminal 1, the sequence of radio pulses is sent to the input of the delay line 2, which has n - conclusions. The delay of the signal propagating along the delay line between its outputs is equal to the period of the following radio pulses.

The conclusions of the delay line are connected to the inputs of n inertial four-terminal 3, which perform the following function: they pass the pulse without change if its initial phase is 0, or change its phase by π if its initial phase is 180 °.

The findings of n inertial four-pole connected to the input of the adder 4, which accumulates a useful signal. The longer the sequence of radio pulses, the more efficient the operation of the receiver - drive, which is the optimal filter for the described input signal.

The optimal receiver - drive described in [8] has the following disadvantages:

- the difficulty of implementing a delay line for sonar signals in the frequency range from several kHz to several hundred kHz;

- with an increase in the number of positions of the sequence of radio pulses, the efficiency of the optimal filter decreases due to an increase in losses introduced by the delay line, which can be 70 or more dB [5];

- low reliability.

At a frequency of radio pulses from several kHz to several hundred kHz, typical for signals of hydroacoustic equipment [1], the delay time between the taps of the delay line should be at least several microseconds.

For example, with a closed sequence of five radio pulses with a frequency of 100 kHz, the minimum delay time between the taps of the delay line should be 30 μs, the total delay time is 150 μs.

When using a modern component base, the feasibility of such a delay line is difficult. Known acoustic delay lines providing a signal delay of up to several hundred microseconds operate at frequencies not lower than 10 MHz and have significant insertion loss [5], known electronic analog delay lines [7] do not provide linear phase characteristics, in addition, the complexity of construction, the presence of a large number of components parts, reduces their reliability.

The proposed design of an optimal receiver of hydroacoustic signals solves the problems of simplifying the design, increasing reliability, increasing filtering efficiency, expanding the operating frequency range to sound frequencies.

The essence of the invention lies in the fact that a transmitting optoelectronic module, an optical splitter with a configuration of 1 × optical poles, are introduced into an optimal receiver of hydroacoustic signals containing a band-pass amplifier, the input of which is the input of the optimal filter, n-delay lines, the outputs of which are connected to n inputs of the adder n, n additional delay lines, a receiving optoelectronic module, wherein the output of the strip amplifier is connected to the input of the 1 × n optical splitter through the transmitting optoelectronic module, n outputs of the 1 × n splitter are connected to the inputs of n - delay lines, the outputs of which are connected to the n inputs of the adder through n - additional delay lines, the output of the adder is connected to the input of the receiving optoelectronic module, the output of which is the output of the optimal filter, all delay lines are made in the form of pieces of optical fiber of a certain length, and the adder is made in the form of an optical combiner with the configuration of the optical poles n × 1.

The structural diagram of the proposed optimal receiver of hydroacoustic signals is presented in figure 2.

The optimal receiver of hydroacoustic signals consists of the following components:

- a strip pre-amplifier 1, the passband of which corresponds to the spectrum of the n - positional sequence of radio pulses of sound or ultrasonic frequency supplied to its input;

- transmitting optoelectronic module 3, converting the n - positional sequence of radio pulses from the output of the strip amplifier 3 into optical radiation, the intensity of which varies with the frequency of the radio pulses;

- optical splitter 5, distributing the output optical signal of the transmitting optoelectronic module between n - channels;

- n fiber-optic delay lines (FOL) 2, representing a regular FOL (in accordance with GOST R 54417 - 2011 "Components of fiber-optic transmission systems. Terms and definitions" of a regular FOL is called multipolar FOL, whose optical signal delay times are a series of arithmetic progression, multi-pole fiber optic link is a combination of unipolar fiber optic links integrated structurally);

- n additional FOL 6;

- optical combiner 4, combining the output optical signals from the delay lines into a single optical signal

- receiving optoelectronic module 7, converting a single optical signal into an electrical output signal, which is the total signal of the input sequence of radio pulses.

Moreover:

- the transmission coefficient of the optical signals of n - parallel transmission channels remains constant, since the losses introduced by n fiber-optic delay lines (FOL) 2 and 6 are compensated by the adjustable transmission coefficients of the splitter 5 and combiner 4;

- the step of the arithmetic progression of the delay time of the regular fiber optic link 2 is equal to the period of following T radio pulses of n - positional sequence of radio pulses;

- the delay value of the i-th fiber optic link from n additional fiber-optic links 6 (i∈ {1, 2, n}) depends on the initial phase of the FM of the i-th radio pulse entering the i-th transmission channel, with the initial phase of the radio pulse equal to 0, the delay value τ is much less than the oscillation period of the radio pulse t (τ << t), with the initial phase of the radio pulse equal to 180 °, the delay value τ is equal to half the oscillation period of the radio pulse (τ = t / 2);

- if non-FM radio pulses arrive at the filter input, then the delay values of all additional delay lines 6 are minimal and the same.

The proposed device (the optimal receiver of hydroacoustic signals) can work with the following input signals used in sonar [1]:

- simple signals representing n - a positional sequence of radio pulses of the same frequency;

- complex signals representing FM n - a positional sequence of radio pulses of the same frequency;

- complex signals representing radio pulses with a wide spectrum of frequencies (in particular, these signals include signals whose frequency varies according to the linear law (LFM) and discrete frequency signals (DF)).

If there is a simple signal at the input, which is an n - positional sequence of radio pulses of the same frequency, the strip preamplifier 1 should have a narrow passband with a central frequency equal to the frequency of the radio pulses.

The step of the arithmetic progression of the delay time of the regular VOLZ 2 should be equal to the period T of the radio pulses. The signal delay of the ith fiber optic link τ _i relative to the signal delay of the (i-1) fiber optic link τ _i-1 should be greater by T, where T is the period of the radio pulses

Additional VOLZ 6 should be shorted or delay signals at the same time.

If there is a complex signal at the input, which is an FM n - positional sequence of radio pulses of the same frequency, the strip pre-amplifier 1 must have a narrow passband with a central frequency equal to the frequency of the radio pulses.

The step of the arithmetic progression of the delay time of the regular fiber optic link 2 should be equal to the period of the following T radio pulses, as in the case of a simple signal.

The delay time of additional VOLZ 6 depends on the selected code for changing the phase of the radio pulses.

The delay value of the i-th fiber optic link (i - varies from 1 to n) with the initial phase of the i-th radio pulse equal to 0, should be much less than the oscillation period of the radio pulse, with the initial phase of the i-th radio pulse equal to 180 °, should be equal to half the oscillation period radio pulse.

If there is a complex signal at the input, which is radio pulses with a wide spectrum of frequencies or with a discrete set of frequencies, the bandwidth of the strip pre-amplifier should correspond to the signal spectrum.

The step of the arithmetic progression of the delay time of the regular fiber optic link 2 should be equal to the period of the following T radio pulses, as in the case of a simple signal.

Additional FOCLs must be shorted or delayed at the same time.

Consider the design of the individual nodes of the proposed optimal receiver of hydroacoustic signals.

The input preamplifier can be assembled on a component base for general use.

Optoelectronic receiving and transmitting modules are components of general application, a wide range of such modules is produced by domestic industry.

The production of optical splitters / combiners has been mastered by domestic industrial enterprises. For their manufacture, either welded technology (RSV - Fused Biconical Taper) or planar technology (PLC - Planar Lightwave Circuit) is used [10]. Both that and other technologies allow to make splitters / combiners with the set (adjusted) transmission coefficients at the far end.

Delay lines 2 and 6 are made in the form of segments of an optical fiber of a certain length.

Consider the parameters of such delay lines for a typical signal.

Let the sequence of FM radio pulses with the following characteristics come to the filter input:

- the number of pulses n is 6, n = 6;

- frequency filling radio pulses - 200 kHz;

- duration of radio pulses - 15 μs (three periods);

- the period of the following radio pulses is 20 μs.

The maximum delay time (for the n-th delay line) is τ = 20⋅ (n-1) = 100 μs.

Note - The delay time of the 1st delay line can be several nanoseconds, that is, the first delay line is quasi shorted, the delay time of the 2nd delay line should be 20 μs, the second - 40 μs, and so on.

The length of the fiber for delaying the signal by 100 μs is

where c is the speed of light in vacuum, 3⋅10 ⁸ m / s;

τ is the delay value;

n _with - the refractive index of the fiber core (for a standard fiber n _with = 1,48).

Loss α _LZ introduced by such a delay line into the transmission path will be

where β is the attenuation coefficient of a standard fiber at a wavelength of optical radiation of 1.55 μm (β = 0.18 dB / km);

L is the fiber length, L = 20.27 km.

Loss of α _LZ will amount to 3.6 dB, which is much less than the power budget of modern optoelectronic transceiver modules, which at a frequency of 200 kHz is at least 40 dB.

To delay the signal by a half-cycle of the radio pulse (τ = t / 2 = 2.5 μs), the length of the fiber segment of the additional delay line should be 506 m.

To ensure the uniformity of optical powers in n parallel transmission channels, it is advisable to set the requirements for the transmission coefficients of optical splitters and combiners such that the product of the splitter transmission coefficient and the delay line transmission coefficient and the combiner transmission coefficient remains constant for all transmission channels.

For the possibility of operational tuning of the filter when changing the FM code, it is advisable to connect all fiber-optic components using detachable optical connectors.

As shown above, the present invention solves the following problems:

- simplification of the design;

- increased reliability;

- increasing the efficiency of filtration;

- expanding the range of operating frequencies to sound frequencies.

The evidence for solving the tasks are as follows.

Simplification of the design is achieved by simplifying the design of the delay lines. The delay line in the proposed design is a coil with optical fiber wound around it, the outer diameter of the fiber with a buffer coating of 245 microns. In the prototype device, the delay line is a complex device based on surface acoustic waves, or a multistage electronic device.

The design of the adder is simplified, in the proposed device it is a fiber-optic component (optical combiner), manufactured according to the proven technology, in the prototype device is a complex multi-input electronic device that provides mutual isolation of input circuits.

Improving reliability is achieved by the fact that components with increased reliability are introduced into the device: optoelectronic receiving and transmitting modules, fiber-optic delay lines, optical splitter and combiner Their reliability indicators exceed the reliability used in the prototype multi-tap delay line and adder.

We will evaluate the reliability of the components of the proposed device and the prototype device for specific components.

Consider a set of transceiver optoelectronic modules POM-27 and PrOM-15, manufactured by ZhGDK.433769.048 TU.

The gamma-percent operating time to failure (T _γ ) of the kit in the operating modes established in the technical specifications for the kit, with a value of γ = 90% within the service life of T _sl = 25 years, must be at least T _γ = 100,000 h.

The failure rate of optical fibers according to [11] is λ = 2.33 2,310 ^-15 (1 / h) ⋅ m.

Gamma-percent MTBF (T _γ ) of optical splitters of the type OR-BE010, manufactured according to TU 6665-018-41085936-2006, in the operating modes established in TU, with a value of γ = 90% within the service life of T _sl = 25 years must be at least T _γ = 100,000 hours

Suppose that the prototype device uses an ultrasonic delay line of the LZRP type, manufactured according to ОУ0.206.020 TU, according to [11], the gamma-percent MTBF (T _γ ) of the delay line in the operating modes established in the TU, with λ = 95% should be at least T _γ = 7500 hours

For comparison, we will recalculate the presented reliability indicators of the components of the proposed device and the prototype device in the failure rate. The calculation results are summarized in a table.

Even without taking into account the reliability of the adder, the reliability of the components of the proposed device is more than three times higher than the reliability of the components of the prototype device.

Improving the filtering efficiency is achieved by reducing the signal loss in the delay line (losses in the fiber-optic line delay for a time of 100 μs are 3.6 dB, losses in a similar delay time of the ultrasonic delay line will be about 60 dB). In addition, in the proposed device, it is possible to equalize the amplitudes of the component components of the signal (in parallel transmission channels), which also increases the filtering efficiency.

The extension of the operating frequency range is ensured by the principle of the fiber-optic delay line. Optical fiber has virtually no bandwidth limitations.

The operating frequency range is determined only by the operating frequency range of the set of transceiver modules, which at the present stage of technological development is from 0 to 20 GHz.

References:

1. Algorithms for processing sonar signals: monograph / I.V. Karabanov, A.S. Mironov. - Khabarovsk: Publishing House of the Pacific State University, 2018 .-- 140 p.

2. RF patent 2249831 "Device for optimal filtering of phase-shifted signals." S.F. Lukyanov.

3. RF patent 2332707 "Method for processing a Barker signal when it is detected." A.V. Smirnov.

4. Baskakov S.I. Radio circuits and signals. - M.: Higher School, 2000 .-- 462 p.

5. Acoustic delay lines, information from the site http://bourabai.ru/physics/1963.html

6. Dmitriev V.F. Integrated Electronics Devices: Acousto-Electronics. Fundamentals of theory, calculation and design: study guide / SUAI. - SPb., 2006 .-- 169 p.

7. Shustov MA, Circuitry. 500 devices on analog microcircuits. - St. Petersburg: Science and Technology, 2013 .-- 352 p.

8. I.S. Gonorovsky Radio engineering circuits and signals: a textbook for high schools, 3rd edition, revised and supplemented. - M .: Soviet Radio, 1977 .-- 608 p.

9. Theory of telecommunications: a textbook for open source software / V.I. Nefedov, A.S. Sigov; under the editorship of IN AND. Nefedova. - M.: Yurayt Publishing House, 2016 .-- 495 p.

10. Tsukanov V.N., Yakovlev M.Ya. Fiber optic technology. A practical guide. - M .: Infra-Engineering, 2014 .-- 304 p.

11. Reliability of electrical products. Handbook of the Ministry of Defense of the Russian Federation, 2006 - 641 p.

Claims (1)

An optimal receiver of hydroacoustic signals containing a band amplifier, the input of which is the input of the optimal filter, n are delay lines, the outputs of which are connected to n inputs of the adder, characterized in that a transmitting optoelectronic module and an optical splitter with a configuration of optical poles 1 × n are inserted into it, n additional delay lines, a receiving optoelectronic module, the output of a strip amplifier connected to the input of a 1 × n optical splitter through a transmitting optoelectronic module, n outputs of a 1 × n splitter connected to the inputs of n - delay lines, the outputs of which are connected to n inputs of the adder through n - additional delay lines, the output of the adder is connected to the input of the receiving optoelectronic module, the output of which is the output of the optimal filter, all delay lines are made in the form of pieces of optical fiber of a certain length, and the adder is made in the form of an optical combiner with the configuration of the optical poles n × 1.

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