Sonar transmitting-receiving isolation circuit based on bridge balance network

Abstract

The application provides a sonar transmitting-receiving isolation circuit based on a bridge balance network, which comprises a control and signal processing unit, a transmitting signal amplification circuit, a differential drive circuit, a bridge isolation network, an ultrasonic transducer and a receiving channel. The bridge isolation network is arranged between the differential drive circuit and the receiving channel and is connected with the ultrasonic transducer. In the transmitting stage, the differential drive circuit outputs high-voltage differential drive signals with a phase difference of 180 degrees, which drives the ultrasonic transducer to transmit ultrasonic waves through the bridge balance isolation network. Meanwhile, the bridge balance structure formed by the cross-coupled resistance network is used to offset the transmitting leakage signals, so as to reduce the leakage of the high-voltage signals to the receiving channel. In the receiving stage, the ultrasonic transducer receives echo signals, and the echo signals are input into the control and signal processing unit for subsequent signal processing operation after being processed by the bridge isolation network to form a differential output signal at the receiving end, the controllable gain amplification of the programmable weak signal amplification circuit and the processing of the band-pass filter and the level matching circuit. The application has the characteristics of simple structure, small nonlinear distortion and high system stability, and is suitable for high-voltage ultrasonic ranging, underwater sonar detection and other scenes.

Description

Technical Field

[0001] This invention relates to the field of underwater sonar detection and ultrasonic transceiver technology, and in particular to a sonar transceiver isolation circuit based on a bridge balanced network. Background Technology

[0002] In ultrasonic ranging and underwater sonar detection systems, a single ultrasonic transducer is typically used to simultaneously transmit and receive ultrasonic signals. During transmission, a high-voltage excitation signal needs to be applied to the ultrasonic transducer. However, during reception, it is necessary to detect echo signals with extremely small amplitudes. Therefore, achieving effective isolation between transmission and reception is one of the key issues in sonar systems.

[0003] In existing technologies, mechanical relays, analog switches, or diode clamping networks are commonly used for transmit / receive switching. While mechanical relays offer high isolation, they suffer from drawbacks such as large size, slow switching speed, and limited lifespan. Analog switches are easily limited by withstand voltage in high-voltage ultrasonic applications. Traditional diode clamping structures typically rely on diode conduction to limit high-voltage transmitted signals; while relatively simple in structure, they are prone to nonlinear distortion under high voltage and high-frequency conditions, and also affect weak echo signals. Furthermore, traditional isolation methods cannot fully utilize the symmetrical characteristics of differential signals, allowing transmitted leakage signals to easily enter the receiving channel, affecting system performance and echo detection capabilities.

[0004] Therefore, there is an urgent need for a sonar transceiver isolation circuit that does not require mechanical switching, diode limiting, or clamping, but utilizes the characteristics of the differential drive signal itself to suppress transmission leakage while ensuring high-frequency response and weak echo detection capabilities. Summary of the Invention

[0005] This invention proposes a sonar transceiver isolation circuit based on a bridge balanced network, constructing a differential cross-coupled bridge isolation network between the transmitting and receiving channels. This invention utilizes the anti-symmetry relationship of the differential drive signals to achieve leakage cancellation of high-amplitude transmitted signals, reducing the impact of high-voltage transmitted signals on the receiving channel and thus protecting the receiving channel. It also enables multiplexing of the ultrasonic transducer's transmitting and receiving functions, improving the system's reliability and stability.

[0006] The technical solution to achieve the objective of this invention is as follows: a sonar transceiver isolation circuit based on a bridge balanced network, comprising: a control and signal processing unit, a transmit signal amplification circuit, a differential drive circuit, a bridge balanced isolation network, an ultrasonic transducer, and a receiving channel, wherein:

[0007] The transmit signal amplification circuit is used to amplify the transmit signal output by the control and signal processing unit; the differential drive circuit is used to convert the amplified transmit signal into a differential signal with a phase difference of 180° and perform power amplification.

[0008] The bridge balanced isolation network includes a first symmetrical diode unit, a second symmetrical diode unit, and a cross-coupled resistor network; the differential signal after power amplification is output as a first high-voltage differential drive signal and a second high-voltage differential drive signal through the first symmetrical diode unit and the second symmetrical diode unit, respectively; the two ends of the ultrasonic transducer are respectively connected to the output ends of the first symmetrical diode unit and the second symmetrical diode unit.

[0009] The cross-coupled resistor network includes a first resistor unit and a second resistor unit. Each first and second resistor unit includes two resistors. One end of one resistor in the first resistor unit is connected to the output terminal of a first symmetrical diode unit, and one end of the other resistor is connected to the input terminal of a second symmetrical diode unit. The two ends of the two resistors in the first resistor unit are connected together as a first output terminal. Similarly, one end of one resistor in the second resistor unit is connected to the output terminal of the second symmetrical diode unit, and one end of the other resistor is connected to the input terminal of the first symmetrical diode unit. The two ends of the two resistors in the second resistor unit are connected together as a second output terminal. The two output terminals of the cross-coupled resistor network are connected to a receiving channel. The receiving channel amplifies and filters the signal output from the cross-coupled resistor network before inputting it to a control and signal processing unit.

[0010] Compared with the prior art, the significant advantages of this invention are:

[0011] (1) The anti-symmetric characteristics of the differential driving signal are utilized to cancel transmission leakage through a cross-coupling structure, thereby improving the transmission and reception isolation performance of the circuit. (2) The ultrasonic transducer's transmission and reception functions are multiplexed without the use of mechanical relay switching or diode limiting and clamping, thereby improving the system's response speed and reliability. (3) An anti-parallel diode structure is adopted to improve the symmetry and balance characteristics of the isolation network under differential driving conditions. (4) A bridge-type balanced structure is adopted to suppress high-voltage transmission signal leakage and protect the weak echo signal detection capability of the receiving channel. (5) The structure is simple and the response speed is fast, making it suitable for applications such as high-voltage ultrasonic ranging and underwater sonar detection.

[0012] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0013] Figure 1 This is a block diagram of the overall system structure of the present invention.

[0014] Figure 2This is a schematic diagram of the differential leakage cancellation principle during the launch phase of this invention.

[0015] Figure 3 This is a schematic diagram illustrating the principle of differential echo output during the receiving stage of this invention. Detailed Implementation

[0016] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0017] like Figure 1 As shown, this embodiment provides a sonar transceiver isolation circuit based on a bridge balanced network, which achieves transceiver multiplexing of the ultrasonic transducer by utilizing differential driving, cross coupling, and balanced cancellation. This invention has a simple structure, high system stability, and is suitable for underwater sonar detection, high-voltage ultrasonic ranging, and other scenarios. This invention includes a control and signal processing unit, a transmit signal amplification circuit, a differential driving circuit, an ultrasonic transducer, a bridge balanced isolation network, a programmable weak signal amplification circuit, a bandpass filter, and a level matching circuit.

[0018] The control and signal processing unit generates a sonar transmission excitation signal and performs subsequent signal processing operations on the target echo signal. The transmission excitation signal may include BPSK, QPSK phase-coded intra-pulse modulation signals, etc. The transmission excitation signal generated by the control and signal processing unit is input to a transmission signal amplification circuit for preliminary signal amplification, and then input to a differential drive circuit. The differential drive circuit includes an active balun circuit and a power amplifier circuit, which converts the single-ended transmission signal output from the transmission signal amplification circuit into high-power differential drive signals Vpa1 and Vpa2 with a phase difference of 180°, thereby driving the ultrasonic transducer to emit ultrasonic waves for target detection.

[0019] The bridge balanced isolation network includes a first symmetrical diode unit, a second symmetrical diode unit, and a cross-coupled resistor network. A differential drive signal Vpa1 is input to the input terminal of the first symmetrical diode unit, and a differential drive signal Vpa2 is input to the input terminal of the second symmetrical diode unit. The first symmetrical diode unit includes a first diode D1 and a second diode D2 connected in anti-parallel, and the second symmetrical diode unit includes a third diode D3 and a fourth diode D4 connected in anti-parallel. The output terminals of the first and second symmetrical diode units are respectively connected to the two ends of an ultrasonic transducer to drive the transducer to emit ultrasonic waves. Further, a first coupling resistor R1 is led out from the input terminal node of the first symmetrical diode unit, and a second coupling resistor R2 is led out from the output terminal of the second symmetrical diode unit. The other ends of the first coupling resistor R1 and the second coupling resistor R2 are coupled together to form a differential output node Vout−. A third coupling resistor R3 is led out from the output terminal of the first symmetrical diode unit, and a fourth coupling resistor R4 is led out from the input terminal of the second symmetrical diode unit. The other ends of the third coupling resistor R3 and the fourth coupling resistor R4 are coupled together to form a differential output node Vout+. The first, second, third, and fourth coupling resistors of the cross-coupled resistor network are selected with the same resistance value to ensure the symmetry of the cross-coupled resistor network and improve the balance and cancellation effect of differential leakage signals during the transmission phase.

[0020] The differential echo output signal is input to a programmable weak signal amplification circuit for low-noise amplification. In this embodiment, the programmable weak signal amplification circuit uses a low-noise programmable gain amplifier to amplify the weak echo signal in the pre-stage, and dynamically adjusts the receiving gain according to the echo signal strength to adapt to the echo detection requirements under different target distance conditions. The amplified echo signal is then input to a bandpass filter for frequency band selection and out-of-band noise suppression. The passband frequency range of the bandpass filter is matched to the operating frequency of the ultrasonic transducer to improve the signal-to-noise ratio of the target echo signal. The filtered effective echo signal is adjusted to the input range of the subsequent analog-to-digital converter by a level matching circuit, and finally input to the control and signal processing unit for digital signal processing.

[0021] This invention utilizes a differential cross-coupling structure and the anti-symmetric relationship of differential driving signals to cancel transmission leakage, thus enabling the multiplexing of ultrasonic transducer transmission and reception functions. It features simple structure, fast response speed, and good isolation performance. It is suitable for high-voltage ultrasonic ranging, underwater sonar detection, and ultrasonic imaging systems.

[0022] like Figure 2As shown, during the transmission phase, the differential drive signals Vpa1 and Vpa2 satisfy an anti-symmetrical relationship, with a phase difference of 180°, Vpa1 = -Vpa2. The high-voltage differential drive signal is input to the bridge balanced isolation network and coupled through the first symmetrical diode unit, the second symmetrical diode unit, and the cross-coupling resistor network. Assume the diode forward voltage drop is... ,Right now = = = = The node voltages after passing through the diodes are as follows:

[0023] =Vpa1-

[0024] =Vpa2-

[0025] The differential drive signal satisfies: Vpa1 = -Vpa2. After passing through the cross-coupled resistor network, the leakage voltage formed at the nodes of Vout+ and Vout- is:

[0026] =0.5*( +Vpa2)-0.5*( +Vpa1)

[0027] Substituting the above relationships and simplifying, we get: =- Therefore, under ideal symmetry conditions, most of the common-mode components of the transmitted leakage signal are canceled out after passing through the cross-coupling network, and the residual leakage voltage at the receiver is mainly related to the diode forward voltage drop. This invention utilizes the anti-symmetry relationship of the differential drive signal and the balance characteristics of the cross-coupling network to achieve transmit leakage suppression, thereby reducing the amount of high-voltage transmitted signal entering the receiving channel. Simultaneously, since both the first and second symmetrical diode units adopt an anti-parallel structure, they can adapt to the bidirectional conduction requirements under the positive and negative half-cycles of the differential drive signal and improve the symmetry of the isolation network under high-voltage differential drive conditions.

[0028] like Figure 3 As shown, during the receiving phase, the transmit drive is turned off, and Vpa1=Vpa2=0. At this time, the target echo differential signal is output from both ends of the transducer. =- .when At that time, the output voltage of the receiving node is:

[0029] =0.5* -0.5*

[0030] Substituting the above relationships and simplifying, we get:

[0031] =

[0032] During the receiving phase, the differential echo signal is output at the Vout+ and Vout- nodes and input to the subsequent receiving channel for further signal processing. When the echo signal amplitude is small, the diode is in the off state, and the signal is output at the Vout+ and Vout- nodes.

[0033] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A sonar transceiver isolation circuit based on a bridge balanced network, characterized in that, include: The system comprises a control and signal processing unit, a transmit signal amplification circuit, a differential drive circuit, a bridge balanced isolation network, an ultrasonic transducer, and a receiving channel, wherein: The transmit signal amplification circuit is used to amplify the transmit signal output by the control and signal processing unit; the differential drive circuit is used to convert the amplified transmit signal into a differential signal with a phase difference of 180° and perform power amplification. The bridge balanced isolation network includes a first symmetrical diode unit, a second symmetrical diode unit, and a cross-coupled resistor network; the differential signal after power amplification is output as a first high-voltage differential drive signal and a second high-voltage differential drive signal through the first symmetrical diode unit and the second symmetrical diode unit, respectively; the two ends of the ultrasonic transducer are respectively connected to the output ends of the first symmetrical diode unit and the second symmetrical diode unit. The cross-coupled resistor network includes a first resistor unit and a second resistor unit. Each first and second resistor unit includes two resistors. One end of one resistor in the first resistor unit is connected to the output terminal of a first symmetrical diode unit, and one end of the other resistor is connected to the input terminal of a second symmetrical diode unit. The two ends of the two resistors in the first resistor unit are connected together as a first output terminal. Similarly, one end of one resistor in the second resistor unit is connected to the output terminal of the second symmetrical diode unit, and one end of the other resistor is connected to the input terminal of the first symmetrical diode unit. The two ends of the two resistors in the second resistor unit are connected together as a second output terminal. The two output terminals of the cross-coupled resistor network are connected to a receiving channel. The receiving channel amplifies and filters the signal output from the cross-coupled resistor network before inputting it to a control and signal processing unit.

2. The sonar transceiver isolation circuit based on a bridge balanced network according to claim 1, characterized in that, The differential drive circuit includes an active balun circuit and a power amplifier circuit. The active balun circuit is used to convert the amplified transmitted signal into a differential signal with a phase difference of 180°. The power amplifier circuit is used to amplify the differential signal to obtain a high-amplitude differential signal.

3. The sonar transceiver isolation circuit based on a bridge balanced network according to claim 1, characterized in that, The receiving channel includes a programmable weak signal amplification circuit, a bandpass filter, and a level matching circuit connected in sequence. The programmable weak signal amplification circuit is used to amplify the signal output from the two output terminals of the cross-coupled resistor network with low noise, and dynamically adjusts the amplification gain according to the signal amplitude. The bandpass filter is used to filter the signal amplified by the programmable weak signal amplification circuit, thereby suppressing out-of-band noise and interference signals. The level matching circuit is used to adjust the amplitude and level of the filtered signal, and to control the input signal processing unit.

4. The sonar transceiver isolation circuit based on a bridge balanced network according to claim 1, characterized in that, The first symmetrical diode unit includes a first diode and a second diode connected in reverse parallel, and the second symmetrical diode unit includes a third diode and a fourth diode connected in reverse parallel. The first symmetrical diode unit and the second symmetrical diode unit are respectively disposed in the transmission path of the differential drive signal to realize bidirectional conduction under the positive and negative half-cycle conditions of the differential drive signal.

5. The sonar transceiver isolation circuit based on a bridge balanced network according to claim 1, characterized in that, During the transmission phase, the differential drive circuit outputs a differential signal with a phase difference of 180°, which is then output as a high-voltage differential drive signal through the first symmetrical diode unit and the second symmetrical diode unit, thereby driving the ultrasonic transducer to emit ultrasonic waves. At the same time, the high-voltage differential drive signal cancels out the transmission leakage at the output end of the cross-coupled resistor network through the cross-coupled resistor network, thereby reducing the leakage of the high-voltage transmission signal to the receiving channel, realizing transmission and reception isolation and protecting the subsequent receiving circuit. During the receiving phase, the ultrasonic transducer receives the target echo and generates a weak differential voltage signal at both ends of the ultrasonic transducer. The differential voltage signal passes through a cross-coupled resistor network and outputs an echo differential voltage signal at the output end of the cross-coupled resistor network. This signal is then input into the receiving channel for amplification and filtering before being input into the control and signal processing unit.

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