RU2754124C1 - Method for forming a video pulse sequence using an acoustic delay line - Google Patents

Abstract

FIELD: video pulse technology.

SUBSTANCE: invention relates to tools for forming a video pulse sequence using an acoustic delay line. Direct conversion of the input electrical pulse into acoustic pulses and back into electrical pulses is performed by means of a multi-channel acoustic delay line formed by pairs of emitting and receiving piezoelectric converters unified by acoustic lines. A unipolar rectangular video pulse is used as an input electric pulse, wherein the polarisation polarity signs of the piezoelectric converters of each pair of channels are pre-determined based on the condition of emission/reception of heteropolar leading edges of acoustic waves in the acoustic line. The sought electrical pulse sequence is formed by combining the heteropolar electrical signals received at the receiving piezoelectric converters. The polarity and the time delay are set by the propagation time of acoustic pulses in acoustic lines.

EFFECT: expanding the operational capabilities by providing a possibility of forming heteropolar video pulses with a preset time delay.

8 cl, 13 dwg

Description

The invention relates to radio engineering and can be used in the design of piezoelectric components of signal processing devices, sensors of physical quantities, as well as in physical experiments.

It is known that for processing electrical signals of various nature and purpose, systems are used that use piezoelectric components to convert signals into acoustic waves and vice versa. This makes it possible to build various converters of electrical and magnetic quantities in computer devices, monitoring and control systems, including acoustic delay lines (ALL) (see, for example, R.G.Dzhagupov, A.A. Erofeev Piezoceramic elements in instrumentation and automation, L, Mechanical Engineering, 1986, pp. 207-244).

For these purposes, systems are described using both volumetric (BAW) and surface acoustic waves (SAW). When generating and detecting surfactants, structures are used with electrodes of periodically alternating polarity, deposited on the surface of a piezoelectric substrate. A conventional interdigital converter (IDT) can be used to process RF pulses, but not video pulses. This is due to the fact that the IDT itself is a bandpass filter with a finite bandwidth Δf / f, which is inversely proportional to the number of electrodes N. The resonant frequency f is determined by the SAW propagation speed V and the period λ of the converter. For example, at V = 3000 m / s, λ = 20 μm and N = 20, the values of f and Δf / f are equal to 150 MHz and 5%, respectively.

In the patent for the invention US 3680007 (A), IBM, 07.25.1972 describes a device for signal processing on SAW using IDT for generating and detecting returning to zero sequences of surface waves. The IDT includes main electrodes, which are perpendicular to the transducer leads, and auxiliary electrodes, which are inclined at an angle to the main electrodes. In order to increase the product of the bandwidth and the delay time for the video pulses used in data processing, coding is applied, for example, Barker code and Golay code. The advantage of this type of coding can be seen in the fact that the input signals of the complementary sequence are digits with one amplitude unit, while the output signal has a digit with four amplitude units in the center and zero elsewhere. The disadvantage of this method of signal processing is its high sensitivity to the accuracy of manufacturing the required topology and to the state of the surface due to the use of the surface type of vibration.

In the invention GB 765780 (A) from 09.01.1957 - a prototype, an acoustic transducer system is described, including a multi-tap ALS on bulk acoustic waves. It contains an input piezoelectric transducer (PC) emitting an acoustic pulse and output PCs, placed along paths of various lengths, which read acoustic pulses with high-frequency filling and convert them into electrical pulses of the same frequency. These pulses create a sequence of electrical pulses of the same polarity across the load at a repetition rate multiplied by the number of acquisition units and the provided delay traces. To ensure operation, it is required to excite the input PP with a radio pulse with a carrier frequency equal to half the acoustic wavelength in the PP. The unconditional disadvantages of the device are the impossibility of receiving multipolar video pulses and the presence of a liquid sound line in the ALZ. These disadvantages limit the possibilities of the device implementation.

The present invention is aimed at expanding the capabilities of acoustic signal processing devices in terms of overcoming these disadvantages and simplifying circuitry implementation. It is based on the following premises.

As already noted above, the generation of acoustic pulses using the PP is provided in the resonant mode, that is, when the PP thickness (for BAW) or the distance between the electrodes (for SAW) is an integer number of half-wavelengths. This is the mode used in the above solutions.

Piezoceramic PP, in its simplest form, is a rectangular or circular plate polarized in a constant electric field to create a piezoelectric effect. To generate thickness vibration modes, the PP has two electrodes deposited on wide surfaces perpendicular to the direction of polarization (Piezoceramic transducers: Handbook, L., Sudostroenie, 1984, pp. 45-72). Thick modes of PP vibrations cause an acoustic wave with longitudinal polarization in a sound-conducting medium.

If a short video pulse, for example, of positive polarity, is applied to the PP, then the piezoelectric element, due to the inverse piezoeffect, will instantly change its dimensions and generate an acoustic wave in the connected acoustic conductor with a leading edge of compression or extension, depending on the polarity of the video pulse in relation to the polarization sign of the polarization of the PP. When the polarity of the video pulse changes and / or the sign of the polarity of the piezoceramic element changes, the sign of the leading edge of the acoustic wave changes to the opposite, which is observed experimentally.

The patented method for generating a sequence of electrical pulses includes direct conversion of an input electrical pulse into acoustic pulses and back into electrical pulses by means of a multichannel acoustic delay line (ALL).

The difference is as follows.

ALZ is formed by pairs of emitting and receiving piezoelectric transducers, united by sound lines. As an input electrical pulse, a unipolar rectangular video pulse is used, while the polarization signs of the piezoelectric transducers of each pair of channels are preliminarily determined from the condition of emission / reception of multipolar leading fronts of acoustic waves in the acoustic duct.

The desired sequence of electrical pulses is formed by adding bipolar electrical video signals obtained on the receiving piezoelectric transducers, and the polarity and time delay between single electrical pulses are set by the propagation time of acoustic pulses in sound lines.

The method can be characterized in that the emitting and receiving piezoelectric transducers are piezoceramic elements with thickness polarization for excitation / reception of longitudinal acoustic waves.

The method can also be characterized by the fact that for a two-channel ALZ having identical sound lines and parallel-connected pairs of emitting and receiving piezoceramic transducers, the said receiving transducers have opposite polarization polarization signs, and also by the fact that for a two-channel ALS formed by a common emitting piezoceramic transducer and a single sound line , and having parallel-connected receiving piezoceramic transducers, said receiving transducers have opposite signs of polarization polarity.

The method can be characterized, in addition, by the fact that for the ALZ formed by a pair of parallel-connected emitting piezoceramic transducers, each of which is connected to an individual acoustic conductor, and a common receiving piezoceramic transducer, the acoustic conduits are made of identical materials and are located in the direction of propagation of the acoustic wave counter to each other , the polarization signs of the named emitting and receiving transducers are the same, while the dimensions L ₁ , L _{2 of the} acoustic ducts are selected from the condition | L ₁ -L ₂ | = Δt × V, where V is the velocity of the acoustic wave in the acoustic duct, Δt is the delay time between the nearest output signals of both pairs of converters, and the delay time τ of the generated pulse relative to the input video pulse is determined by the smaller of the two values L ₁ / V, L ₂ / V.

The method can be characterized by the fact that for the ALZ formed by a pair of parallel connected emitting piezoceramic transducers and a common receiving piezoceramic transducer, the sound lines are made of identical materials and are located in the direction of propagation of acoustic waves in series with each other, the polarization signs of the emitting piezoceramic transducers are the same, and the polarization sign of the receiving transducer is opposite to them, and the dimensions L ₁ , L _{2 of the} acoustic ducts are selected from the condition | L ₁ -L ₂ | = Δt × V, where V is the velocity of the acoustic wave in the acoustic duct, Δt is the delay time between the nearest output signals of both pairs of transducers , and the delay time τ of the generated pulse relative to the input video pulse is determined by the smaller of the two values L ₁ / V, L ₂ / V.

The method can also be characterized by the fact that for an ALZ formed by pairs of parallel-connected emitting piezoceramic transducers, each of which is connected to an individual acoustic conductor, and a common receiving piezoceramic transducer, the acoustic conduits are made of different materials and are located in the direction of propagation of acoustic waves counter to each other, the polarization signs of the named emitting and receiving transducers are the same, while the distances L _i , L _{i + 1} from the i-th and i + 1-th emitters to the common receiver are selected from the condition | L _i / V _n -L _{i + 1} / V _m | = Δt, where V _n , V _m are the velocities of acoustic waves in the sound ducts n and m, Δt is the delay time between the nearest output signals for the i-th and i + 1-th pairs of transducers, and the delay times τ of the generated sequence of signals of the relative the input pulse is determined by the lesser of the two values L _i / V _n , L _{i + 1} / V _m .

The method can be characterized, in addition, by the fact that for the ALZ formed by pairs of parallel-connected emitting piezoceramic transducers, each of which is connected to an individual acoustic conductor, and a common receiving piezoceramic transducer, the acoustic conduits are made of different materials and are located in the direction of propagation of acoustic waves in series with each other , the polarization signs of the emitting piezoceramic transducers are the same, and the polarization sign of the receiving transducer is opposite to them, and the distances L _i , L _{j + 1} from the i-th and i + 1-th emitting transducers to the common receiving transducer are selected from the condition | L _i / V _n -L _{i + 1} / V _m | = Δt, where V _n , V _m are the velocities of acoustic waves in the sound ducts n and m, Δt is the delay time between the nearest output signals for the i-th and i + 1-th pair of transducers, and the delay time τ _{i of the} generated sequence of signals of the relative input pulse is determined by the smaller of the two values L _i / V _n , L _{i + 1} / V _m .

The technical result is an expansion of functionality, namely: the formation of either equidistant pulses of the same (different) polarity, or non-equidistant pulses of the same (different) polarity, and with a given amount of time delay between individual pulses of the formed sequence. An additional technical result is a demonstration, in the learning process, of the capabilities of piezoceramic transducers on the simplest measuring equipment (oscilloscope, pulse generator).

The essence of the invention is illustrated in the drawings, where:

fig. 1-3 - the principle of excitation of video signals in the single-span ALZ mode, taking into account the polarization signs of the emitting and receiving transducers;

fig. 4-5 - experimental data;

fig. 6 - signal generation at ALZ using two spatially separated single-span ALZs;

fig. 7, 8 - formation of signals at ALZ using a single sound conduit, a common emitting and two receiving transducers;

fig. 9, 10 - formation of signals based on ALZ using two sound lines located opposite to the directions of propagation of acoustic waves, two emitting transducers and one receiving transducer between them;

fig. 11, 12 - formation of signals based on ALZ using two sound lines arranged in series with respect to the directions of propagation of acoustic waves, two emitting transducers and one receiving transducer;

fig. 13 shows examples of sequences of video pulses that can be obtained by the patented method.

FIG. 1-5 explains the principle of obtaining video signals in the single-span ALZ mode, taking into account the polarization signs of the emitting and receiving transducers.

The circuit (Fig. 1) contains a pulse generator 1 for supplying a unipolar rectangular video pulse 10, a receiver 2 for receiving electrical pulses at the output load, an emitting 3 piezoelectric transducer with electrodes 4, a sonic conductor 5, a receiving 6 piezoceramic transducer with electrodes 7, the direction 8 of acoustic propagation waves in ALZ. As mentioned above, in the case when a piezoelectric material is used as a piezoelectric material, the latter undergoes a polarization process with a high DC voltage during production and is characterized by a polarization polarity sign, the direction of which is shown by an arrow (Fig. 2, 3).

In the event that the polarity of the rectangular video pulse 10 applied to the emitting transducer 3 coincides with the polarization polarity sign, as well as with the polarization sign of the receiving transducer 6, then an acoustic wave is recorded at the receiver, the leading edge 21 of which repeats the sign of the input pulse of the transducer 3 (Fig. 2 , 4).

If the polarization sign of the receiving transducer 6 is opposite to the sign of the emitting transducer 3, then an acoustic wave is generated, the leading edge 23 of which has the opposite polarity (Figs. 3, 5). In this case, the delay time Δt between the nearest output signals of the ALZ is determined by the multiple reflections of the received acoustic wave between the surfaces of the receiving transducer 6.

Thus, in FIG. 4, 5 show the results of an experiment confirming the possibility of changing the polarity of the leading edge of the signal recorded at the receiver 2 due to the change in the polarity of the receiving transducer 6. The small difference in the signal amplitude in the experiment is due to the difference in gluing between the transducers and sound lines.

FIG. 6 shows the principle of formation of a sequence of electrical pulses using two spatially separated single-span ALZs. Emitting 3 and 6 receiving transducers are piezoceramic elements with polarization in thickness for exciting longitudinal acoustic waves. Sound ducts 5 are made of the same material and have the same length. Emitting converters 3 are connected in parallel to the pulse generator 1 so that the signs of their polarization coincide. Receiving transducers 6 are also connected in parallel to receiver 2, however, they have opposite polarization. As a result (addition), bipolar acoustic pulses at the output of the transducers 6 compensate each other, which ensures the formation of a zero signal in the receiver 2 (Fig. 8).

FIG. 7 shows a diagram of the ALZ formed by a single acoustic conductor 5 and a common emitting piezoceramic transducer 31, generating a longitudinal acoustic wave in the direction 8. The wave is recorded at distances L ₁ , L ₂ from the emitter 31, receiving piezoceramic transducers 61, 62, the electrodes 71, 72 of which are connected in parallel and together with a common electrode 73 are connected to the receiver 2. The converters 61, 62 have opposite signs of polarization polarization, therefore, at their output, bipolar electrical pulses are formed, which, when L ₁ ≠ L ₂ , are added to each other, create an output electrical signal, and when L ₁ = L ₂ - compensate each other and form in the receiver 2 a "zero" electrical signal 63 of small amplitude at the level of the ALZ noise (Fig. 8), which is not used. This signal is a consequence of the non-identity of the receiving transducers 61, 62 and their acoustic contact with the sound line 5.

FIG. 9-10 and FIG. 11-12 show various embodiments of the method using two non-identical sound lines and three piezoceramic transducers.

Thus, in FIG. 9 shows a composite ALZ formed by a pair of emitting piezoceramic transducers 31, 32, connected in parallel to a pulse generator 1. Transducers 31, 32 are connected to individual sound lines 51, 52. With respect to the directions of propagation of the radiated acoustic waves, the sound lines 51, 52 are located opposite, and the common receiving piezoceramic transducer 6 is located in the middle of the ALZ. Sound ducts 51, 52 have dimensions L ₁ , L ₂ in the directions 81, 82 of propagation of acoustic waves. The polarization signs of the named emitting and receiving transducers are unidirectional.

In the event that the sonic conduits 51.52 are made of the same material and differ only in the size L ₁ , L ₂ , then the condition : | L ₁ -L ₂ | = Δt × V, where V is the speed of acoustic waves in the acoustic duct, Δt is the delay time between the nearest output signals of both pairs of transducers (Fig. 10). When L ₂ <L _{1, the} value of the delay τ of the signal of positive polarity (pos. 81 + 82) relative to the input pulse 10 is equal to L ₂ / V. The value of τ is regulated by changing the length L _{2 of} the shorter acoustic conduit 52 while observing the condition | L ₁ -L ₂ | = Δt × V. FIG. 10 shows the result of signal interference at the receiving transducer 6. It can be seen that as a result of the interference, opposite polarity acoustic pulses 81 and 82, being added to each other, form a signal 81 + 82 of positive polarity.

In the event that the sound lines 51, 52 are made of different materials, that is, they are characterized by different velocities V ₅₁ , V _{52 of} acoustic waves in the sound lines 51, 52, then the distances L _i , L _{i + 1} from the i-th and i + 1- emitting transducers to the common receiving transducer 6 are selected from the condition | L _i / V ₅₁ -L _{i + 1} / V ₅₂ | = Δt, where V ₅₁ , V ₅₂ are the wave velocities in the acoustic ducts 51 and 52, Δt is the delay time between the nearest output signals 81, 82 i-th and i + 1-th pair of emitter-receiver (Fig. 10). The delay times τ _i formed by different pairs of the signal sequence of the relative input pulse 10 is determined by the lesser of the two values L _i / V ₅₁ , L _{i + 1} / V ₅₂ . The values of τ _{i are} regulated by changing the lengths of the corresponding sound lines while observing the condition: | L _i / V ₅₁ -L _{i + 1} / V ₅₂ | = Δt.

FIG. 11, 12 shows another variant of signal generation based on a composite ALS using two sound lines, two emitting and one receiving transducer.

The composite ALZ is formed by a pair of parallel-connected emitting piezoceramic transducers 31 and 32, each of which is connected to individual sound ducts 51, 52 made of different materials, and with respect to the directions of propagation of the emitted acoustic waves, the sound ducts 51, 52 are arranged in series. ALZ has a common receiving transducer 6, while the polarization signs of the emitting piezoceramic transducers 31, 32 are unidirectional, and the polarization sign of the receiving transducer 6 is opposite to them. The distances L _i , L _{i + 1} from the i-th and i + 1-emitting transducers to the common receiving transducer 6 are selected from the condition: | L _i / V ₅₁ -L _{i + 1} / V ₅₂ | = Δt, where V ₅₁ , V ₅₂ are the velocities of acoustic waves in the acoustic ducts 51 and 52, Δt is the delay time between the nearest output signals of the i-th and i + 1-st pairs of emitter-receiver. The delay times τ _i formed by different pairs of the signal sequence 81 + 82 of the relative input pulse 10 are determined by the lesser of the two values L _i / V ₅₁ , L _{i + 1} / V ₅₂ . The values of τ _i are set by changing the lengths of individual sound lines while observing the condition | L _i / V ₅₁ -L _{i + 1} / V ₅₂ | = Δt.

In the event that the propagation velocities of acoustic waves in the acoustic ducts 51 and 52 are the same (V ₅₁ = V ₅₂ = V), the distances L ₁ , L ₂ are selected from the condition: | L ₁ -L ₂ | = Δt × V, and the delay time signal 81 + 82 is determined by the value of L ₂ / V of the shorter sound line.

FIG. 12 shows the result of signal interference at the receiving transducer 6. It can be seen that as a result of the interference, bipolar acoustic pulses 81 and 82, being added to each other, form a signal 81 + 82 of negative polarity.

Thus, the polarities and delay times of the video signals 81 + 82 at the output of the receiver 2 (Fig. 9-12) are adjustable and can be used to form a given time code (a sequence of positive and / or negative pulses following each other in a certain way), as well as for modulating RF signals following one after another with a given time interval.

FIG. 13 shows examples of sequences of video pulses that can be obtained by the patented method. Numerals 101 and 102 show sequences of positive unipolar pulses, the duration between which is adjustable. Pulses of negative polarity are shown at pos. 105, single pulses of bipolar form - pos. 103; A sequence of pulses with alternating polarity is shown at pos. 104.

Thus, the use of multichannel delay lines, in which, during the excitation and reception of delayed acoustic pulses, the polarization sign of piezoceramic transducers is purposefully taken into account, makes it possible to expand the functionality, namely, to form either a sequence of equidistant pulses of the same (different) polarity, or a sequence of non-equidistant pulses of the same (different) polarity, and with a given value of the time delay between the individual pulses of the formed sequence. An additional technical result is a demonstration, in the learning process, of the capabilities of piezoceramic transducers on the simplest measuring equipment (oscilloscope, pulse generator).

Claims (18)

1. A method for generating a sequence of electrical pulses, including direct conversion of an input electrical pulse into acoustic pulses and back into electrical pulses by means of a multichannel acoustic delay line (ALL), characterized in that ALZ is formed by pairs of emitting and receiving piezoelectric transducers, united by sound lines, as an input electric pulse, a unipolar rectangular video pulse is used, while the polarization signs of the piezoelectric transducers of each pair of channels are preliminarily determined from the condition of emission / reception of multipolar leading fronts of acoustic waves in the acoustic duct, and the sought-for sequence of electrical pulses is formed by adding bipolar electrical video signals obtained on the receiving piezoelectric transducers, and the polarity and time delay between single electrical pulses are set by the propagation time of acoustic pulses in sound lines. 2. A method according to claim 1, characterized in that the emitting and receiving piezoelectric transducers are piezoceramic elements with thickness polarization for exciting / receiving longitudinal acoustic waves. 3. The method according to claim 1 or 2, characterized in that for a two-channel ALS having identical sound lines and parallel-connected pairs of emitting and receiving piezoceramic transducers, said receiving transducers have opposite signs of polarization polarity. 4. The method according to claim 1 or 2, characterized in that for a two-channel ALS formed by a common emitting piezoceramic transducer and a single acoustic conductor and having parallel-connected receiving piezoceramic transducers, said receiving transducers have opposite polarization polarization signs. 5. The method according to claim 1 or 2, characterized in that for the ALZ formed by a pair of parallel-connected emitting piezoceramic transducers, each of which is connected to an individual sound conductor, and a common receiving piezoceramic transducer, The sound lines are made of identical materials and are located in the direction of propagation of acoustic waves counter to each other, the polarization signs of the named emitting and receiving transducers are the same, while the dimensions L ₁ , L _{2 of the} sound lines are selected from the condition | L ₁ -L ₂ | = Δt × V, where V is the speed of the acoustic wave in the acoustic duct, Δt is the delay time between the nearest output signals of both pairs of transducers, and the delay time τ of the generated pulse relative to the input video pulse is determined by the smaller of the two values L ₁ / V, L ₂ / V. 6. The method according to claim 1 or 2, characterized in that for the ALZ formed by a pair of parallel connected emitting piezoceramic transducers and a common receiving piezoceramic transducer, The sound lines are made of identical materials and are located in the direction of propagation of acoustic waves in series with each other, the polarization signs of the emitting piezoceramic transducers are the same, and the polarization sign of the receiving transducer is opposite to them, and the dimensions L ₁ , L _{2 of the} sound lines are selected from the condition | L ₁ -L ₂ | = Δt × V, where V is the speed of the acoustic wave in the acoustic duct, Δt is the delay time between the nearest output signals of both pairs of transducers, and the delay time τ of the generated pulse relative to the input video pulse is determined by the smaller of the two values L ₁ / V, L ₂ / V. 7. The method according to claim 1 or 2, characterized in that for the ALZ formed by pairs containing the first and second emitting piezoceramic transducers connected in parallel, each of which is connected with individual first and second sound conductors, and a common receiving piezoceramic transducer, sound lines are made of different materials and are located in the direction of propagation of acoustic waves counter to each other, the polarization signs of the named emitting and receiving transducers are the same, while the distances L ₁ , L ₂ from the first and second emitting transducers to the common receiving transducer are selected from the condition | L ₁ / V ₁ -L ₂ / V ₂ | = Δt, where V ₁ , V ₂ are the velocities of acoustic waves in the first and second acoustic ducts , Δt is the delay time between the nearest output signals for the mentioned pairs of converters, and the delay times τ _{i of the} generated signal sequence relative to the input pulse are determined by the smaller of the two values L ₁ / V ₁ and L ₂ / V ₂ . 8. The method according to claim 1 or 2, characterized in that for the ALZ formed by pairs containing parallel-connected first and second emitting piezoceramic transducers, each of which is associated with individual first and second sound conductors, and a common receiving piezoceramic transducer, the sound lines are made of different materials and are located in the direction of propagation of acoustic waves sequentially to each other, the polarization signs of the emitting transducers are the same, and the polarization sign of the receiving transducer is opposite to them, while the distances L ₁ , L ₂ from the first and second emitting transducers to the common receiving transducer are selected from the condition | L ₁ / V ₁ -L ₂ / V ₂ | = Δt, where V ₁ , V ₂ are the velocities of acoustic waves in the first and second acoustic ducts , Δt is the delay time between the nearest output signals for the mentioned pairs of converters, and the delay time τ _{i of the} generated signal sequence relative to the input pulse is determined by the smaller of the two values L ₁ / V ₁ and L ₂ / V ₂ .

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