Broadband beam forming acoustic Doppler velocity measurement system and method based on time delay control

Abstract

The invention provides a broadband beam forming acoustic Doppler velocity measurement system and method based on time delay control, which can transmit and receive broadband signals and solve the problem that the measurement precision of the existing acoustic Doppler velocity measurement system is influenced by bandwidth. The velocity measurement system comprises a transducer module, a beam forming module and a conversion module, the transducer module comprises a planar transducer array and an impedance matching module connected with the planar transducer array; the transducer module is in signal connection with the beam forming module through the conversion module, and the beam forming module is used for performing time delay compensation and weighting processing on a received signal; and the conversion module is used for converting the echo signal acquired by the transducer module into a digital signal and inputting the digital signal into the beam forming module, or converting a to-be-transmitted signal received from the beam forming module into an analog signal and transmitting the analog signal through the transducer module.

Description

Technical Field

[0001] This invention relates to an acoustic Doppler velocity measurement system and method, specifically to an acoustic Doppler velocity measurement system and method based on time delay control, belonging to the field of underwater acoustic navigation and velocity and flow measurement technology. Background Technology

[0002] Velocity sonar typically transmits and receives acoustic signals using a planar transducer, calculating the velocity of the sonar carrier relative to the water or seabed based on the echo Doppler frequency shift. Velocity sonar based on the acoustic Doppler effect can be used not only for positioning and navigation of ships, submarines, and other vehicles—such sonar equipment is generally called a Doppler Velocity Log (DVL)—but also for measuring the current velocity of rivers and oceans; such sonar equipment is generally called an Acoustic Doppler Current Profiler (ADCP).

[0003] To measure three-dimensional velocity information, acoustic transducers must simultaneously transmit and receive beam signals from at least three different directions. For this purpose, four independent piston-type acoustic transducers are typically combined together via a mechanical structure to form four spatially symmetrical beams (Janus structure). However, the Janus structure piston-type transducer may interfere with the flow field near the transducer during velocity measurement, and the measurement accuracy is significantly affected by the speed of sound. Furthermore, to ensure the acoustic wave travel distance and echo signal-to-noise ratio, the transducer generally requires a small beam opening angle, resulting in very large weight and size for low-frequency Janus structure transducers, making them impractical for many applications.

[0004] Phased array technology, by controlling the phase information of a large number of array element signals, can simultaneously form four spatial beams using a single planar transducer, effectively avoiding the aforementioned problems of piston arrays. It is currently widely used in the field of acoustic Doppler velocimetry. The principle of velocity and current measurement based on the Doppler effect is as follows: pulsed sound waves are emitted into the water or seabed through multiple obliquely arranged sound beams, the echoes are received, and the relative velocity is calculated based on the change in echo frequency (i.e., Doppler shift).

[0005] A typical phased array acoustic Doppler velocimetry system includes key components such as a circular planar transducer, a phase control system, and an impedance matching network. It generally fixes the beam pointing at 30°, extracts rows and columns with the same phase and merges them into a single path, achieving beam transmission and reception with fewer transmitters and receivers. However, current phased array acoustic Doppler velocimetry systems have the following significant drawbacks: To reduce the short-term uncertainty of velocity measurement results and improve measurement accuracy and data update rate, phase-coded signals with a relative bandwidth of 6.25% to 12.5% ​​are generally used in Doppler velocimetry systems. However, beam pointing achieved through phase shifting is bandwidth-sensitive, leading to widening of the main lobe and increased side lobes in the beam formed by wide-bandwidth phase-coded signals. This limits the application of phase-coded signals in high-precision velocity measurement scenarios; therefore, current phased array acoustic Doppler velocimetry systems are only used for narrowband signal transmission and reception. Summary of the Invention

[0006] In view of this, the present invention provides a broadband beamforming acoustic Doppler velocimetry system based on time delay control. Compared with phase control, time delay control can better adapt to complex signals such as phase coding, and can transmit and receive broadband signals, thus solving the problem that the measurement accuracy of existing acoustic Doppler velocimetry systems is affected by bandwidth.

[0007] The technical solution of the present invention is: a broadband beamforming acoustic Doppler velocimetry system based on time delay control, comprising: a transducer module, a beamforming module and a conversion module;

[0008] The transducer module includes a planar transducer array and an impedance matching module connected to the planar transducer array.

[0009] The transducer module is signal-connected to the beamforming module through the conversion module. The beamforming module is used to perform time delay compensation and weighting processing on the received signal.

[0010] The conversion module is used to convert the echo signal collected by the transducer module into a digital signal and input it to the beamforming module, or to convert the signal to be transmitted received from the beamforming module into an analog signal and transmit it through the transducer module.

[0011] In a preferred embodiment of the present invention, the planar transducer array includes a plurality of transducer units arranged in a multi-row, multi-column structure;

[0012] Each row of the planar transducer array has one external interface, and each column has one external interface.

[0013] The impedance matching module is a multi-channel impedance matching module, including impedance matching circuits that correspond one-to-one with the multiple external interfaces led out from the planar transducer array; the external interfaces led out from the planar transducer array are respectively connected to their corresponding impedance matching circuits; the impedance matching circuits are used to perform impedance matching processing on the received signals.

[0014] The multi-channel impedance matching module adopts a distributed common reference connection, that is, all impedance matching circuits in the multi-channel impedance matching module have the same common reference ground and secondary reference ground;

[0015] The multi-channel impedance matching module is signal-connected to the conversion module.

[0016] In a preferred embodiment of the present invention, the impedance matching circuit includes a transformer, a primary circuit located on the primary winding side of the transformer, and a secondary circuit located on the secondary winding side of the transformer.

[0017] The primary circuit is provided with a first positive connection port and a first negative connection port; the first positive connection port is electrically connected to the corresponding signal led out from the planar transducer array; the first negative connection ports of the primary circuits in all the impedance matching circuits are connected together to form a common reference ground.

[0018] The secondary circuit is provided with a second positive terminal and a second negative terminal. The second positive terminal is electrically connected to the corresponding subsequent circuit. The second negative terminal of the secondary circuit in all impedance matching circuits is connected together to form the secondary reference ground.

[0019] In a preferred embodiment of the present invention, the second positive terminal connection port in the impedance matching circuit corresponds to the positive terminal of the transmitted signal;

[0020] When the second positive terminal of the secondary circuit in all impedance matching circuits is connected together, all emitted acoustic beam signals are the same.

[0021] When the second positive port of the secondary circuit in the impedance matching circuit is configured independently, it can emit different acoustic beam signals.

[0022] In a preferred embodiment of the present invention, the positive terminal of the primary winding of the transformer is provided with a first positive terminal connection port, and the negative terminal is provided with a first negative terminal connection port; the primary circuit includes: a first resistor, a first inductor, a first capacitor, a second capacitor, and a third capacitor, wherein the first resistor, the first inductor, and the first capacitor are connected in series; the second capacitor and the third capacitor are connected in parallel between the first capacitor and the first resistor; the first capacitor, the second capacitor, and the third capacitor are all electrically connected to the first positive terminal connection port, and the negative terminal of the primary winding is connected to the other end of the first resistor, the second capacitor, and the third capacitor;

[0023] The positive terminal of the transformer secondary winding is provided with a second positive terminal connection port, and the negative terminal is provided with a second negative terminal connection port. The secondary circuit includes a fourth capacitor, a second inductor, and a third inductor. One end of the fourth capacitor is electrically connected to the second positive terminal connection port, and the other end is connected in series with the third inductor. The other end of the third inductor is electrically connected to the positive terminal of the secondary winding and one end of the second inductor, respectively. The negative terminal of the secondary winding is connected to the other end of the second inductor.

[0024] In a preferred embodiment of the present invention, the planar transducer array includes a plurality of transducer units arranged in a multi-row, multi-column structure;

[0025] The planar transducer array is divided into several subarrays by row and column, namely row subarray and column subarray;

[0026] Signals are extracted after pre-beamforming within each row subarray and each column subarray in a phase-shift manner;

[0027] The impedance matching module performs impedance matching processing on the signals derived from each of the row subarrays and each of the column subarrays.

[0028] In a preferred embodiment of the present invention, the effective aperture of the subarray is set to be ,but:

[0029]

[0030] in: For the desired transmit signal bandwidth, The nominal beam pointing angle, The speed of sound in the medium;

[0031] The maximum effective aperture of the subarray can be obtained based on the above formula.

[0032] In a preferred embodiment of the present invention, the beamforming module includes a transmitting component and a receiving component;

[0033] The transmitting component includes: an upsampling unit, a first time delay unit, a first phase shift unit, a first weighting unit, and an upconversion unit; the upsampling unit is used to perform digital interpolation filtering on the baseband data and increase the sampling rate to the rate required for internal beamforming processing; the first time delay unit and the first phase shift unit sequentially perform time delay compensation and phase compensation on the interpolated baseband data according to the target transmission direction to generate multiple baseband data streams; the first weighting unit is used to apply amplitude weighting to each baseband data stream; the upconversion unit is used to perform upconversion processing on the weighted baseband data.

[0034] The receiving component includes: a down-conversion unit, a second time delay unit, a second phase shift unit, a second weighting unit, and a downsampling unit; the down-conversion unit performs down-conversion processing on the received signal, the second time delay unit and the second phase shift unit sequentially perform time delay compensation and phase compensation on the down-converted baseband data; the second weighting unit performs weighted accumulation on the baseband data to form beam output data, and the downsampling unit is used to downsample the beam output data to form a digital signal to be processed.

[0035] Furthermore, based on the velocity measurement system, this invention provides a broadband beamforming acoustic Doppler velocimeter method based on time delay control, comprising the following steps:

[0036] Generate a baseband signal from the baseband data to be transmitted;

[0037] According to the preset transmission direction, the baseband signal is time-delayed to form multiple signals, and then each signal is weighted.

[0038] The weighted data is upsampled and mixed to a preset center frequency, and then converted into a real signal;

[0039] After signal conditioning and power amplification of the real signal, the transmitted signal is obtained and transmitted through the planar transducer array;

[0040] The planar transducer array receives the echo signal;

[0041] The received signal is conditioned, and then the conditioned signal is subjected to quadrature mixing and downsampling to obtain the baseband complex signal;

[0042] Inter-channel delay compensation and amplitude weighting are performed on the baseband complex signal to synthesize the received beam data.

[0043] The velocity information is obtained by estimating the Doppler frequency shift parameters of the received beam data.

[0044] Beneficial effects:

[0045] (1) The speed measurement system of the present invention is based on the time delay beamforming theory, which can correct the beam distortion caused by broadband signals. Compared with phase control, time delay control can better adapt to complex signals such as phase coding, thereby enabling the transmission and reception of broadband signals and solving the problem that the measurement accuracy of the existing acoustic Doppler speed measurement system is affected by bandwidth.

[0046] (2) In the speed measurement system of the present invention, when each row and column of the planar transducer array leads out an external interface, a distributed common reference connection is adopted to form a multi-channel impedance matching module for its impedance matching module, which can solve the problem of transducer impedance matching in the complex structure of the time delay array and improve the system energy transmission efficiency. This kind of full time delay speed measurement system takes into account the flexibility of beam pointing control and low distortion. It can control the beam pointing through time delay adjustment. Theoretically, it can achieve precise control of beam pointing at any angle under broadband conditions, significantly reduce the beam broadening error caused by broadband signals, and has the application capability in complex scenarios (non-uniform flow field, unmanned cluster, etc.).

[0047] (3) In the speed measurement system of the present invention, when the planar transducer array is divided into subarrays, after the full array is divided into subarrays, pre-beamforming can be performed in the subarrays in a phase-shift manner, and impedance matching can be performed in a conventional impedance matching manner; time delay compensation and weighting between subarrays are performed outside the subarrays, thereby completing beamforming. This can effectively avoid the beam pointing error generated by the traditional phase-shift method during broadband transmission, and can also greatly reduce the complexity of the engineering implementation of the full time delay control method and simplify the structure of the system. Attached Figure Description

[0048] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0049] Figure 1 This is a structural block diagram of the acoustic Doppler velocimetry system based on time delay control in Embodiment 1 of the present invention;

[0050] Figure 2 This is a schematic diagram of the multi-channel impedance matching network in Embodiment 1 of the present invention;

[0051] Figure 3 In the figure, (a) and (b) are respectively the transmitted waveforms of a single-frequency narrowband signal and a wideband phase-coded signal after impedance matching according to the present invention;

[0052] Figure 4 This is a schematic diagram of the transmission link of the speed measurement system according to Embodiment 1 of the present invention;

[0053] Figure 5 This is a schematic diagram of the receiving link of the speed measurement system according to Embodiment 1 of the present invention;

[0054] Figure 6 This is a flowchart of the acoustic Doppler velocimetry system based on time delay control, which is an embodiment of the present invention.

[0055] Figure 7This is a schematic diagram of the subarray division and impedance matching connection in Embodiment 2 of the present invention;

[0056] Figure 8 This is a schematic diagram of the beam pointing and transmission design after subarray division in Embodiment 2 of the present invention;

[0057] Figure 9 This is a schematic diagram of the beam pointing and receiving design after subarray division in Embodiment 2 of the present invention.

[0058] Wherein: 1-planar transducer array, 2-impedance matching circuit, 21-first positive terminal connection port. Detailed Implementation

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0060] To keep the drawings concise, only the parts relevant to the invention are shown schematically in each figure, and they do not represent the actual structure of the product. Furthermore, for ease of understanding, in some figures, only one of components with the same structure or function is shown schematically, or only one is labeled. In this document, "one" can mean not only "only one" but also "more than one".

[0061] The broadband beamforming acoustic Doppler velocimetry system based on time delay control proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0062] The broadband beamforming acoustic Doppler velocimetry system based on time delay control proposed in this embodiment can effectively avoid the beam pointing error caused by traditional phase shift methods during broadband transmission, and solve the problem that the measurement accuracy of existing acoustic Doppler velocimetry systems is affected by bandwidth.

[0063] The speed measurement system includes a transducer module, a beamforming module, and a conversion module. The transducer module comprises a planar transducer array 1 and an impedance matching module connected to the planar transducer array 1. As an example, the planar transducer array 1 is a circular planar array, comprising several transducer elements arranged in a multi-row, multi-column structure, with each transducer element being an array element. The impedance matching module is used to perform impedance matching on the received signal.

[0064] The transducer module is connected to the beamforming module via a conversion module. The beamforming module is used to perform time delay compensation and weighting processing on the received signal. The conversion module is used to convert the echo signal collected by the transducer module into a digital signal and input it to the beamforming module, or to convert the signal to be transmitted received from the beamforming module into an analog signal and transmit it through the transducer module.

[0065] The following are two specific implementations of a broadband beamforming acoustic Doppler velocimetry system based on time delay control.

[0066] Example 1:

[0067] The broadband beamforming acoustic Doppler velocimetry system based on time delay control in this embodiment adopts full time delay control technology. Compared with phase control, it can not only better adapt to complex signals such as phase coding and solve the problem that the measurement accuracy of existing acoustic Doppler velocimetry systems is affected by bandwidth, but also control the beam pointing by adjusting the time delay, which can theoretically achieve beam pointing at any angle.

[0068] like Figure 1 As shown, the acoustic Doppler velocimetry system in this example includes a transducer module, a beamforming module, and a conversion module. The transducer module includes a planar transducer array 1 and an impedance matching module; the planar transducer array 1 is a circular planar array, including several transducer elements, which are arranged in a multi-row, multi-column structure, with each transducer element being an array element.

[0069] The planar transducer array 1 is extracted by row and column, and each row and column is led out by physical wires. The first column is led out as "H-CH1", the second column is led out as "H-CH2", and so on, until all columns are led out. The same lead-out method is used for the rows, and all rows are led out, where the first row is led out as "V-CV1", the second row is led out as "V-CV2", and so on.

[0070] As an example, the planar transducer array 1 has 32 rows and 32 columns.

[0071] For full-delay control technology, the main problem to be solved is the impedance matching problem of transducers in the complex structure of the time-delay array. In this example, the impedance matching problem of transducers in the complex structure of the time-delay array can be solved by designing a multi-channel impedance matching network, thereby improving the system's energy transmission efficiency.

[0072] In this example, the impedance matching module is a multi-channel impedance matching module. The planar transducer array 1 is connected to the multi-channel impedance matching module. The multi-channel impedance matching module is connected to the beamforming module through a conversion module. After phase shifting, time delay and other operations in the beamforming module, the signal can be transmitted and received in any direction.

[0073] The multi-channel impedance matching module includes impedance matching circuits that correspond one-to-one with the multiple interfaces led out from the planar transducer array; the signals led out from the planar transducer array 1 are respectively connected to the corresponding impedance matching circuits.

[0074] like Figure 1 As shown, in this example, the multi-channel impedance matching module includes a V-channel multi-channel impedance matching network and an H-channel multi-channel impedance matching network. The V-channel multi-channel impedance matching network has impedance matching circuits 2 (32 in this example) that correspond one-to-one with the rows led out of the planar transducer array 1. The H-channel multi-channel impedance matching network has impedance matching circuits 2 (32 in this example) that correspond one-to-one with the columns led out of the planar transducer array 1. All rows led out of the planar transducer array 1 are sequentially connected to the corresponding impedance matching circuits 2 in the V-channel multi-channel impedance matching network, and all columns are sequentially connected to the corresponding impedance matching circuits 2 in the H-channel multi-channel impedance matching network.

[0075] In acoustic Doppler velocimeters, the impedance matching method of the planar transducer array directly affects the overall power transmission efficiency, bandwidth performance, and phase consistency. In order to form arbitrary beam pointing, distributed impedance matching is adopted. On this basis, the multi-channel impedance matching module adopts a common reference connection, thus forming a distributed common reference connection transformer matching network. This matching network is an impedance matching scheme that takes into account both system complexity and performance consistency.

[0076] Impedance matching circuit 2 includes a transformer, and primary and secondary circuits located on either side of the transformer. The primary circuit has a first positive connection port and a first negative connection port. The first positive connection port is electrically connected to the corresponding row or column pin of the planar transducer array 1; that is, the first positive connection port of any impedance matching circuit 2 is connected to the corresponding row or column pin of the planar transducer array 1. The negative connection ports of the primary windings of all transformers in all impedance matching circuits 2, i.e., the first negative connection ports, are all connected together (i.e., the negative terminals of the primary windings of all transformers in all impedance matching circuits 2 are commonly connected), forming a common reference ground, equivalent to the system's virtual ground / zero potential reference plane. This structure ensures that the primary input current of each transformer in the multi-channel impedance matching module references the same potential, enhancing the phase consistency and driving stability between rows and columns of the planar transducer array 1. It can be understood that "all impedance matching circuits 2" mentioned here refers to all the impedance matching circuits corresponding to rows and columns of the planar transducer array 1.

[0077] The secondary circuit has a second positive terminal and a second negative terminal. The second positive terminal is electrically connected to the corresponding subsequent circuit. The negative terminals of the transformer secondary windings in all impedance matching circuits 2, i.e., the second negative terminals, are connected together (i.e., the negative terminals of the transformer secondary windings in all impedance matching circuits are connected together) to form the secondary reference ground. In this way, while ensuring isolation, the secondary reference is kept consistent, providing a standard potential reference for subsequent circuit processing.

[0078] Specifically, such as Figure 2 As shown, the circuit structure of impedance matching circuit 2 will now be described. Since the structure of each impedance matching circuit 2 is the same, any one circuit will be used for description:

[0079] Impedance matching circuit 2 includes transformer TR1, a primary circuit located on the primary winding N1 side of transformer TR1, and a secondary circuit located on the secondary winding N2 side of transformer TR1. The positive terminal of the primary winding N1 has a first positive connection port 21, and the negative terminal has a first negative connection port J1. The primary circuit includes a first resistor R1, a first inductor L1, a first capacitor C1, a second capacitor C0, and a third capacitor C3. The first resistor R1, the first inductor L1, and the first capacitor C1 are connected in series. The second capacitor C0 and the third capacitor C3 are connected in parallel between the first capacitor C1 and the first resistor R1. The first capacitor C1, the second capacitor C0, and the third capacitor C3 are all electrically connected to the first positive connection port 21. The pins of the row or column of the planar transducer array 1 corresponding to this impedance matching circuit 2 are electrically connected to the first positive connection port 21. The negative terminal of the primary winding N1 is connected to the other end of the first resistor R1, the second capacitor C0, and the third capacitor C3. In all impedance matching circuits 2, the first negative terminal J1 of the primary winding N1 is connected together to form the primary reference ground, which is also the common reference ground, equivalent to the virtual ground / zero potential reference surface of the system.

[0080] The secondary circuit includes a fourth capacitor C2, a second inductor L2, and a third inductor L3. The positive terminal of the secondary winding N2 of transformer TR1 has a second positive connection port J0, and the negative terminal has a second negative connection port J2. One end of the fourth capacitor C2 is electrically connected to the second positive connection port J0, and the other end of the fourth capacitor C2 is connected in series with the third inductor L3. The other end of the third inductor L3 is then electrically connected to the positive terminal of the secondary winding N2 and one end of the second inductor L2. The negative terminal of the secondary winding N2 and the other end of the second inductor L2 are both electrically connected to the second negative connection port J2. All the negative connection ports J2 of the secondary winding N2 in all impedance matching circuits 2 are connected together to form the secondary reference ground.

[0081] In impedance matching circuit 2, the positive terminal of the secondary winding N2 corresponds to the positive terminal of the transmitted signal. When the second positive terminal J0 of the secondary winding N2 in all impedance matching circuits 2 is connected together, all transmitted acoustic beam signals are the same. When the second positive terminal J0 of the secondary winding N2 in impedance matching circuit 2 is configured independently, the row transmission signal and the column transmission signal can drive the corresponding transducer array elements respectively. Different beams can transmit different signal modes, realizing the differentiation of signal waveforms in the spatial domain, thereby improving the anti-interference performance of the system.

[0082] Figure 3 Images (a) and (b) show a single-frequency narrowband signal and a wideband phase-coded signal, respectively, when using... Figure 2 The transmitted waveform obtained after impedance matching network is shown. Results show that for single-frequency narrowband signals, this design performs consistent with traditional schemes in waveform preservation; while for wideband phase-coded signals, this design can better preserve phase flip information while maintaining amplitude characteristics. The common reference ground structure effectively reduces phase mismatch caused by reference drift between columns or rows of the planar transducer array 1, and facilitates use with phase shifters or fractional delay modules, thereby supporting full-delay beam control at the subarray level.

[0083] In this system, beamforming, upsampling, and downsampling are performed through beamforming and conversion modules. Specifically, the system includes two beamforming modules and two conversion modules. A V-channel multi-channel impedance matching network corresponds to one beamforming module and one conversion module, while an H-channel multi-channel impedance matching network corresponds to one beamforming module and one conversion module. Figure 1 As shown.

[0084] The beamforming module is connected to the corresponding impedance matching network (V-channel multi-channel impedance matching network or H-channel multi-channel impedance matching network) in the multi-channel impedance matching module through the conversion module. It is used to perform delay, phase shift and weighting processing on the signal. The conversion module is used to convert the acquired echo signal (analog signal) into a digital signal and input it to the beamforming module, or to convert the signal to be transmitted (digital signal) received from the beamforming module into an analog signal and transmit it through the planar transducer array 1.

[0085] Specifically: the beamforming module includes a transmitting component and a receiving component; the transmitting component includes an upsampling unit, a first delay unit, a first phase shift unit, a first weighting unit, and an upconversion unit (i.e., a digital upconverter, DUC); for example... Figure 4As shown, the upsampling unit performs digital interpolation filtering on the baseband data, increasing the sampling rate to a higher rate required for internal beamforming processing, thereby achieving finer fractional delay resolution and reducing delay quantization errors. Based on the target transmission direction, the first time delay unit and the first phase shift unit apply precise delay (i.e., time delay compensation) and phase compensation to the interpolated baseband data, respectively, generating multiple baseband data streams. The first weighting unit applies amplitude weighting (beam weighting coefficients) to each baseband data stream to optimize beamform characteristics such as main lobe width and sidelobe suppression. Each weighted baseband data stream enters the upconversion unit (DUC), undergoes integer multiple interpolation to the operating sampling rate of the DAC unit in the conversion module, and is mixed to the specified center frequency, simultaneously generating a real signal. The real signal is sent to the DAC unit for digital-to-analog conversion to form the analog signal to be transmitted.

[0086] When a high-precision delay compensation is used in the first delay unit, the first phase shift unit may not be added to the transmitting component. That is, only the interpolated baseband data is subjected to precise delay compensation to generate multiple baseband data.

[0087] The receiving components include: a down-conversion unit (i.e., a digital down-converter, DDC), a second time delay unit, a second phase shift unit, a second weighting unit, and a downsampling unit; such as Figure 5 As shown, the received signal from the ADC unit in the conversion module first enters the down-conversion unit (DDC) and is mixed to shift the signal near the specified center frequency to the complex baseband. Then, it is low-pass filtered to suppress image and out-of-band noise, and downsampled by an integer multiple to the sampling rate required for beamforming processing. Based on the target wave direction, precise delay (i.e., delay compensation) and phase compensation are applied to the baseband data in the second delay unit and the second phase shift unit, respectively, to achieve wavefront alignment. Each delayed and phase-shifted compensated baseband data is then amplitude-weighted (beam weighting coefficients) in the second weighting unit to optimize the main lobe width and sidelobe suppression performance. Subsequently, the weighted signals are accumulated to form the beam output data. The beam output data is again low-pass filtered and downsampled by an integer multiple to form the digital signal to be processed.

[0088] When a high-precision delay compensation is used in the first delay unit, the first phase shift unit may not be added to the transmitting component. That is, only the interpolated baseband data is subjected to precise delay compensation to generate multiple baseband data.

[0089] As an example, the planar transducer array 1 has 32 rows and 32 columns; therefore, in the transmitting component, the upsampling unit, the first delay unit, the first phase shift unit, the first weighting unit, and the upconversion unit each have 32 channels. In the receiving component, the downconversion unit, the second delay unit, the second phase shift unit, the second weighting unit, the second weighting unit, and the downsampling unit each have 32 channels.

[0090] The conversion module includes a DAC unit and an ADC unit; wherein the DAC unit is configured to convert the digital signal after upconversion processing by the upconversion unit in the transmitting component into an analog signal, and send it as the signal to be transmitted to the planar transducer array 1; the ADC unit is configured to convert the acquired echo data into a digital signal and send it to the downconversion unit.

[0091] The main workflow of this speed measurement system is divided into two parts: transmission and reception. The transmission link and reception link are described in detail below:

[0092] As an example, in the transmission link: the baseband data to be transmitted (complex I / Q form) is first transmitted to the upsampling unit for preprocessing. The upsampling unit upsamples the baseband data to a higher rate (typically 4 to 8 times) through zero-value insertion combined with FIR digital filtering. The upsampling factor must meet the requirement that the delay resolution is ≤ 1 / 4 of the sampling interval to ensure delay and phase shift accuracy. After upsampling is completed, the signal enters the beamforming preprocessing stage: the first delay unit calculates the delay of each column or row according to the set beam pointing angle. ( For the spacing between array elements, This refers to the speed of sound in the medium, typically 1500 m / s. To achieve precise time delay compensation (in the direction of sound wave emission), the first time delay unit sends the calculated time delay signal to the first phase shift unit. The first phase shift unit performs complex multiplication phase compensation on the received time delay signal to ensure phase alignment of each column or row signal, and then sends it to the first weighting unit. The first weighting unit applies amplitude weighting coefficients (such as Taylor weighting) to suppress sidelobes, with a dynamic range of 0.1~1.0 to balance main lobe gain and sidelobe suppression. Subsequently, the signal is upsampled to the carrier sampling rate by a digital upconversion unit (DUC), which satisfies the Nyquist criterion.

[0093] Finally, the complex mixer shifts the baseband signal processed by the transmitter module to the preset center frequency. After being converted into a real signal by Hilbert transformation, the DAC unit completes the digital-to-analog conversion and outputs an analog signal. After signal conditioning and power amplification, it drives the planar transducer array 1 to form a beam in a specified direction.

[0094] As an example, in the receiving link: the ADC unit acquires the echo signal at a sampling rate greater than 4 times the center frequency, and the signal near the specified frequency is mixed to baseband by the down-conversion unit (DDC). The digital down-conversion process uses a local oscillator matched to the transmitter to achieve frequency shifting, and the baseband signal is preserved by low-pass filtering. The down-converted baseband data is processed sequentially by the second time delay unit and the second phase shift unit before being sent to the second weighting unit. The time delay calculation is symmetrical with that of the transmitter, and the phase shift (the negative sign indicates that the receiving phase compensation direction is opposite to the transmitting direction) ensures the spatiotemporal alignment of the multi-element signals. The second weighting unit uses the same weighting coefficients as the transmitter (such as Taylor weighting) to perform amplitude weighted accumulation on the baseband data. After synthesizing the beam data, it is downsampled twice to a lower sampling rate by the downsampling unit, and finally transmitted to the CPU for beamforming post-processing. The conventional method is to estimate the Doppler frequency shift parameters of the beam data to obtain velocity information.

[0095] The system control and signal processing section, as a key component of the acoustic Doppler velocimetry device, is mainly responsible for coordinating the transmission and reception process, and completing tasks such as echo signal preprocessing (data interception, filtering, etc.), echo detection, Doppler frequency estimation (phase estimation, time delay estimation, etc.) and velocity calculation.

[0096] The acoustic Doppler velocimetry system in this example is based on time-delay beamforming theory (full time-delay technology). It solves the impedance matching problem between the complex structure of the time-delay array and the planar transducer by using a transformer matching network with a distributed common reference connection, thereby improving the system's energy transmission efficiency.

[0097] The velocity measurement method based on the above-mentioned time delay control broadband beamforming acoustic Doppler velocimetry system is as follows: Figure 6 As shown, the following steps are included:

[0098] First, the baseband signal to be transmitted is generated;

[0099] Then, according to the preset transmission direction, the baseband signal is sequentially subjected to time delay compensation and phase shift processing to form multiple (e.g., 32) signals;

[0100] The signals are weighted to control the beam shape; then the weighted data is upsampled and mixed to a preset center frequency, and converted into a real signal suitable for transmission.

[0101] After signal conditioning and power amplification, the real signal is transmitted through planar transducer array 1.

[0102] Planar transducer array 1 receives the echo signal; the received signal is pre-conditioned, including low-pass filtering to suppress high-frequency noise, low-noise pre-amplification to improve the signal-to-noise ratio, and time-varying gain control to compensate for signal attenuation;

[0103] The conditioned received signal is subjected to quadrature mixing downconversion and downsampling to obtain the baseband complex signal;

[0104] The baseband complex signal is subjected to inter-channel delay compensation, phase compensation and amplitude weighting processing to synthesize the received beam data;

[0105] The Doppler frequency shift is estimated based on the phase change of the received beam data, and the velocity information of the target is finally calculated.

[0106] Example 2:

[0107] The full-time delay technology used in the above embodiment 1 can solve the problem that the measurement accuracy of the existing acoustic Doppler velocities is affected by the bandwidth, but the full-time delay array has a complex structure. This embodiment provides a simplified design with a specific orientation based on time delay control for acoustic Doppler velocities.

[0108] In this example, the planar transducer array 1 is divided into several subarrays by row and column, namely row subarrays and column subarrays; the subarray division follows the following principles:

[0109] Maximum bandwidth of transmitted signal Aperture of planar transducer array 1 (For a circular planar array, aperture) (approximately its diameter) and nominal beam pointing angle The mathematical relationship between them satisfies the following formula:

[0110] (1)

[0111] in: The velocity of sound in the medium is typically 1500 m / s.

[0112] The subarray design involves dividing the entire array (planar transducer array 1) into multiple subarrays by rows and columns, with each subarray having an effective aperture. This will significantly reduce and relax bandwidth restrictions, effectively reducing the number of transmitters and receivers while meeting the broadband signal transmission requirements of the acoustic Doppler velocimetry system.

[0113] If the system requires a transmit signal bandwidth (i.e., the desired bandwidth) of Then we have:

[0114] (2)

[0115] With a center frequency of 75 kHz, the desired bandwidth Taking a 15 kHz acoustic Doppler velocimetry system as an example, the speed of sound is measured. 1500 m / s, nominal beam pointing angle Given an angle of 30°, substituting this into formula (2) yields a maximum aperture of approximately 0.18 m for the subarray. In this example, the total aperture is... The value is 0.35 m, and the number of subarrays is 2. That is, the entire array (planar transducer array 1) is evenly divided into two column subarrays (left half and right half) along the horizontal direction. At this time, each column subarray contains 16 columns. The entire array is evenly divided into two row subarrays (upper half and lower half) along the vertical direction. At this time, each row subarray contains 16 rows.

[0116] Within each row subarray and each column subarray, pre-beamforming is performed using phase shifting before signal extraction. For example, for row or column subarrays, based on the phase relationship of the array elements during transmission or reception, array elements with the same or equivalent phase (meaning achieving phase equivalence through polarity adjustment, etc., by utilizing phase change laws such as opposite phases) can be extracted in one path, thereby reducing the number of signal channels and lowering hardware design costs.

[0117] In this example, the planar transducer array 1 is designed with subarray division and array element polarity to realize the transmission and reception of broadband signals with a fixed beam direction of 30° in the acoustic Doppler velocimetry system.

[0118] like Figure 7 As shown, taking a half-wavelength array with a beam pointing angle of 30° as an example, under this condition, the phases of the transmitted or received signals of the array elements within each subarray are sequentially spaced at 90° intervals. Therefore, the polarities of the array elements can be arranged sequentially by column or row as positive, positive, negative, negative, and array elements with the same or equivalent phase of transmitted or received signals are led out as one path. This achieves pre-beamforming within the group through phase shifting, followed by conventional impedance matching. Specifically, in this example, each row subarray can be grouped into four rows, with the transducer elements within each group arranged sequentially as positive, positive, negative, negative; each column subarray can be grouped into four columns, with the transducer elements within each group arranged sequentially as positive, positive, negative, negative. This achieves pre-beamforming within each row subarray group and each column subarray group through phase shifting, followed by two signal outputs; then, impedance matching is performed on the signals output from each row subarray and each column subarray.

[0119] It should be noted that, Figure 7 The illustrated implementation is merely a specific example of grouping and channel merging using the phase relationship of array elements. This invention is not limited to this specific array spacing, beam pointing angle, or the number of array elements within a group. Under different array designs and beam pointing conditions, array elements with the same or equivalent phase can still be extracted into a single signal based on the phase relationship of the transmitted or received signals, thereby achieving pre-beamforming within the group through phase shifting, thus simplifying hardware and reducing costs.

[0120] Therefore, in this embodiment, after dividing the entire array into subarrays according to the limiting conditions of formula (2), since the beam direction is fixed, beamforming can be performed first in a fixed phase shift manner inside the subarray, and impedance matching can be performed using a conventional impedance matching method; then, time delay compensation and weighting processing between subarrays are performed outside the subarray, such as... Figure 8 As shown, it is not necessary to perform broadband delay compensation at the full array level; thus, it can effectively avoid the beam pointing error caused by traditional phase shifting methods during broadband transmission, and greatly reduce the engineering complexity of delay control methods.

[0121] In this example, the beamforming module includes a transmitting component and a receiving component; the transmitting component includes an upsampling unit, a first delay unit, a first weighting unit, and an upconversion unit (i.e., a digital upconverter, DUC). During the transmission phase, the upsampling unit performs digital interpolation filtering on the baseband data, upsampling it to a higher rate to achieve finer fractional delay resolution and reduce delay quantization errors. Based on the target transmission direction, the first delay unit applies precise delay compensation to the interpolated baseband data, generating multiple baseband data streams. The first weighting unit applies amplitude weighting (beamweighting coefficients) to each baseband data stream to optimize beamform characteristics such as main lobe width and sidelobe suppression. Each weighted baseband data stream enters the upconversion unit (DUC), is interpolated to an integer multiple of the operating sampling rate of the DAC unit in the conversion module, and mixed to a specified center frequency, simultaneously generating a real signal. The real signal is sent to the DAC unit for digital-to-analog conversion to form the analog signal to be transmitted, such as... Figure 8 As shown.

[0122] The receiving components include: a down-conversion unit (i.e., a digital down-converter, DDC), a second delay unit, a second weighting unit, and a downsampling unit. During the receiving phase, the ADC unit in the conversion module performs analog-to-digital conversion on the received signal to form a digital signal to be processed. The digital signal enters the down-conversion unit (DDC) and is mixed to shift the signal near the specified center frequency to the complex baseband. Subsequently, the signal is received through a beamformer within the subarray. After phase compensation and summation, subarray external beamforming is performed using the second time delay unit and the second weighting unit. Specifically, precise time delay compensation is applied in the second time delay unit to achieve wavefront alignment. For each time-delay-compensated baseband data channel, amplitude weighting (beam weighting coefficients) is applied in the second weighting unit to optimize main lobe width and sidelobe suppression performance. The downsampling unit downsamples the beam output data by integer multiples to form the digital signal to be processed, such as... Figure 9 As shown.

[0123] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A broadband beamforming acoustic Doppler velocimeters system based on time delay control, characterized in that, include: Transducer module, beamforming module and conversion module; The transducer module includes a planar transducer array and an impedance matching module connected to the planar transducer array. The transducer module is signal-connected to the beamforming module through the conversion module. The beamforming module is used to perform time delay compensation and weighting processing on the received signal. The conversion module is used to convert the echo signal collected by the transducer module into a digital signal and input it to the beamforming module, or to convert the signal to be transmitted received from the beamforming module into an analog signal and transmit it through the transducer module.

2. The broadband beamforming acoustic Doppler velocimetry system based on time delay control according to claim 1, characterized in that, The planar transducer array includes several transducer units arranged in a multi-row, multi-column structure; Each row of the planar transducer array has one external interface, and each column has one external interface. The impedance matching module is a multi-channel impedance matching module, including impedance matching circuits that correspond one-to-one with the multiple external interfaces led out from the planar transducer array; the external interfaces led out from the planar transducer array are respectively connected to their corresponding impedance matching circuits; the impedance matching circuits are used to perform impedance matching processing on the received signals. The multi-channel impedance matching module adopts a distributed common reference connection, that is, all impedance matching circuits in the multi-channel impedance matching module have the same common reference ground and secondary reference ground; The multi-channel impedance matching module is signal-connected to the conversion module.

3. The broadband beamforming acoustic Doppler velocimetry system based on time delay control according to claim 2, characterized in that, The impedance matching circuit includes a transformer, as well as a primary circuit on the primary winding side and a secondary circuit on the secondary winding side of the transformer. The primary circuit is provided with a first positive connection port and a first negative connection port; the first positive connection port is electrically connected to the corresponding signal led out from the planar transducer array; the first negative connection ports of the primary circuits in all impedance matching circuits are connected together to form a common reference ground. The secondary circuit is provided with a second positive terminal and a second negative terminal. The second positive terminal is electrically connected to the corresponding subsequent circuit. The second negative terminal of the secondary circuit in all impedance matching circuits is connected together to form the secondary reference ground.

4. The broadband beamforming acoustic Doppler velocimetry system based on time delay control according to claim 3, characterized in that, The second positive terminal in the impedance matching circuit corresponds to the positive terminal of the transmitted signal; When the second positive terminal of all secondary circuits in all impedance matching circuits is connected together, all emitted acoustic beam signals are the same. When the second positive port of the secondary circuit in the impedance matching circuit is configured independently, it can emit different acoustic beam signals.

5. The broadband beamforming acoustic Doppler velocimetry system based on time delay control according to claim 3 or 4, characterized in that, The primary winding of the transformer has a first positive terminal connection port on its positive terminal and a first negative terminal connection port on its negative terminal. The primary circuit includes a first resistor, a first inductor, a first capacitor, a second capacitor, and a third capacitor. The first resistor, the first inductor, and the first capacitor are connected in series. The second capacitor and the third capacitor are connected in parallel between the first capacitor and the first resistor. The first capacitor, the second capacitor, and the third capacitor are all electrically connected to the first positive terminal connection port. The negative terminal of the primary winding is connected to the other end of the first resistor, the second capacitor, and the third capacitor. The positive terminal of the transformer secondary winding is provided with a second positive terminal connection port, and the negative terminal is provided with a second negative terminal connection port. The secondary circuit includes a fourth capacitor, a second inductor, and a third inductor. One end of the fourth capacitor is electrically connected to the second positive terminal connection port, and the other end is connected in series with the third inductor. The other end of the third inductor is electrically connected to the positive terminal of the secondary winding and one end of the second inductor, respectively. The negative terminal of the secondary winding is connected to the other end of the second inductor.

6. The broadband beamforming acoustic Doppler velocimetry system based on time delay control according to claim 1, characterized in that, The planar transducer array includes several transducer units arranged in a multi-row, multi-column structure; The planar transducer array is divided into several subarrays by row and column, namely row subarray and column subarray; Signals are extracted after pre-beamforming within each row subarray and each column subarray in a phase-shift manner; The impedance matching module performs impedance matching processing on the signals derived from each of the row subarrays and each of the column subarrays.

7. The broadband beamforming acoustic Doppler velocimetry system based on time delay control according to claim 6, characterized in that, Let the effective aperture of the subarray be ,but: ； in: For the desired transmit signal bandwidth, The nominal beam pointing angle, The speed of sound in the medium; The maximum effective aperture of the subarray can be obtained based on the above formula.

8. The broadband beamforming acoustic Doppler velocimetry system based on time delay control according to claim 2, 3, or 4, characterized in that, The beamforming module includes a transmitting component and a receiving component; The transmitting component includes: an upsampling unit, a first time delay unit, a first phase shift unit, a first weighting unit, and an upconversion unit; the upsampling unit is used to perform digital interpolation filtering on the baseband data and increase the sampling rate to the rate required for internal beamforming processing; the first time delay unit and the first phase shift unit sequentially perform time delay compensation and phase compensation on the interpolated baseband data according to the target transmission direction to generate multiple baseband data streams; the first weighting unit is used to apply amplitude weighting to each baseband data stream; the upconversion unit is used to perform upconversion processing on the weighted baseband data. The receiving component includes: a down-conversion unit, a second time delay unit, a second phase shift unit, a second weighting unit, and a downsampling unit; the down-conversion unit performs down-conversion processing on the received signal, the second time delay unit and the second phase shift unit sequentially perform time delay compensation and phase compensation on the down-converted baseband data; the second weighting unit performs weighted accumulation on the baseband data to form beam output data, and the downsampling unit is used to downsample the beam output data to form a digital signal to be processed.

9. The broadband beamforming acoustic Doppler velocimetry system based on time delay control according to claim 6 or 7, characterized in that, The beamforming module includes a transmitting component and a receiving component; The transmission component includes: an upsampling unit, a first delay unit, a first weighting unit, and an upconversion unit; the upsampling unit is used to perform digital interpolation filtering on the baseband data and increase the sampling rate to the rate required for internal beamforming processing; the first delay unit performs delay compensation on the interpolated baseband data according to the target transmission direction to generate multiple baseband data streams; the first weighting unit is used to apply amplitude weighting to each baseband data stream; the upconversion unit is used to perform upconversion processing on the weighted baseband data. The receiving component includes: a down-conversion unit, a second delay unit, a second weighting unit, and a downsampling unit; the down-conversion unit performs down-conversion processing on the received signal, the second delay unit performs delay compensation on the down-converted baseband data; the second weighting unit performs weighted accumulation on the baseband data to form beam output data, and the downsampling unit is used to downsample the beam output data to form a digital signal to be processed.

10. A broadband beamforming acoustic Doppler velocimeters method based on time delay control, characterized in that, The speed measuring system according to any one of claims 1-9 includes the following steps: Generate a baseband signal from the baseband data to be transmitted; According to the preset transmission direction, the baseband signal is time-delayed to form multiple signals, and then each signal is weighted. The weighted data is upsampled and mixed to a preset center frequency, and then converted into a real signal; After signal conditioning and power amplification of the real signal, the transmitted signal is obtained and transmitted through the planar transducer array; The planar transducer array receives the echo signal; The received signal is conditioned, and then the conditioned signal is subjected to quadrature mixing and downsampling to obtain the baseband complex signal; Inter-channel delay compensation and amplitude weighting are performed on the baseband complex signal to synthesize the received beam data. The velocity information is obtained by estimating the Doppler frequency shift parameters of the received beam data.

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