A low-noise primary amplifier circuit and noise decomposition method suitable for a transceiver transducer

Abstract

The present invention discloses a low-noise primary amplifier circuit and a noise decomposition method suitable for a transceiver transducer, which mainly includes a transceiver conversion module, a filter module, and an operational amplifier circuit. The transceiver conversion module is provided with a pair of protection diodes D1, D2, D3, and D4, as well as a resistor R4 and a power inductor L. The filter module includes a resistor R1 and a capacitor C, which form a bandpass filter with the power inductor. The operational amplifier circuit is composed of a low-voltage and current noise amplifier and resistors R2 and R3. The present invention replaces the power resistor of the transceiver conversion module with a power inductor, adjusts and optimizes the RC filter parameters at the input end of the amplifier circuit, thereby eliminating the influence of the power resistor in the original circuit on the noise of the amplifier circuit and the signal receiving efficiency; it can be used for low-noise amplification of active sonar echo signals and circuit noise level evaluation; it improves the signal receiving efficiency; a noise calculation model is established to verify the correctness of the circuit design, which can guide the design of the same type of circuits.

Description

Technical Field

[0001] The invention relates to the field of active sonar signal receiving circuits, and in particular to a low-noise primary amplifier circuit and a noise decomposition method suitable for a transceiver transducer. Background Art

[0002] From the Freese formula, we know that each stage of the cascade amplifier circuit has different effects on noise. The earlier the stage, the greater the impact. When the gain of the primary amplifier circuit is large enough, the total noise of the system depends on the noise of the primary amplifier circuit. Therefore, the low noise design of the primary amplifier circuit is very important.

[0003] When the transmitter and receiver share a transducer array, a transceiver conversion module must be used to protect the receiver from damage by high-power signals during transmission and to receive echoes normally during reception. The widely used transceiver conversion module is a power resistor connected in series at the front end of the primary amplifier circuit. The advantages are simple and reliable circuits and strong anti-interference capabilities. The disadvantage is that in order to reduce the impact of the power resistor on the transmission efficiency, the resistance value is required to be much larger than the transducer impedance. When the transducer impedance is large, the thermal noise of the power resistor is much larger than other noises, becoming the main noise source of the primary amplifier circuit. In addition, this resistor and the resistor R in the RC filter circuit at the input end of the amplifier circuit form a voltage divider circuit, which reduces the receiving efficiency of the circuit and becomes an important factor limiting the working distance of the sonar equipment. Summary of the invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and to provide a low-noise primary amplifier circuit and a noise decomposition method suitable for a transceiver transducer.

[0005] The objective of the present invention is achieved through the following technical scheme: This low-noise primary amplifier circuit suitable for a transceiver transducer mainly includes a transceiver conversion module, a filter module, and an operational amplifier circuit. The transceiver conversion module is provided with a pair of protection diodes D1, D2, D3, and D4, as well as a resistor R4 and a power inductor L. The filter module includes a resistor R1, a capacitor C, and a bandpass filter formed with the power inductor. The operational amplifier circuit is composed of a low-voltage, current noise operational amplifier and resistors R2 and R3.

[0006] The equivalent input noise model of the low-noise primary amplifier circuit decomposes the circuit noise into five parts and gives the corresponding calculation method, which mainly includes the following contents:

[0007] 1) Amplify the chip voltage noise Vn;

[0008] 2) Amplify the flow noise Vireq1 generated by the chip current noise In flowing through the equivalent impedance Zreq1 at the positive input end;

[0009] 3) Amplify the flow noise Vireq2 generated by the chip current noise In flowing through the negative input equivalent resistor Rreq2;

[0010] 4) The thermal noise of the resistor R1 at the positive input terminal is equivalent to the noise value Vnreq1 at the input terminal;

[0011] 5) Thermal noise Vnreq2 generated by the equivalent resistance Rreq2 at the negative input end.

[0012] The beneficial effects of the present invention are as follows: the present invention replaces the power resistor of the transceiver conversion module with a power inductor, adjusts and optimizes the RC filtering parameters at the input end of the amplifier circuit, thereby eliminating the influence of the power resistor in the original circuit on the noise of the amplifier circuit and the signal receiving efficiency; can be used for low-noise amplification of active sonar echo signals and circuit noise level evaluation; eliminates the influence of the current noise at the positive input end of the amplifier chip and the thermal noise of the power resistor, reduces the circuit noise of the primary amplifier circuit; improves the signal receiving efficiency; establishes a noise calculation model, verifies the correctness of the circuit design, and can guide the design of the same type of circuits; can be widely used in transducer preamplifier circuits with combined transmission and reception. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the principle of the primary amplifier circuit commonly used for combined transmitting and receiving sonars.

[0014] Figure 2 Schematic diagram of the equivalent input noise model of a universal primary amplifier circuit.

[0015] Figure 3 It is a schematic diagram of the principle of the present invention.

[0016] Figure 4 It is a schematic diagram of the equivalent input noise model of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be described in detail below with reference to the accompanying drawings:

[0018] Embodiment: As shown in the accompanying drawings, this low-noise primary amplifier circuit suitable for a transceiver transducer mainly includes a transceiver conversion module, a filtering module, and an operational amplifier circuit. The transceiver conversion module is provided with a protection diode pair D1, D2, D3, D4, as well as a resistor R4 and a power inductor L. The filtering module includes a resistor R1, a capacitor C, and a power inductor to form a bandpass filter. The operational amplifier circuit is composed of a low voltage, current noise operational amplifier and resistors R2 and R3.

[0019] The equivalent input noise model of the low-noise primary amplifier circuit decomposes the circuit noise into five parts and gives the corresponding calculation method, which mainly includes the following contents:

[0020] 1) Amplify the chip voltage noise Vn;

[0021] 2) Amplify the flow noise Vireq1 generated by the chip current noise In flowing through the equivalent impedance Zreq1 at the positive input end;

[0022] 3) Amplify the flow noise Vireq2 generated by the chip current noise In flowing through the negative input equivalent resistor Rreq2;

[0023] 4) The thermal noise of the resistor R1 at the positive input terminal is equivalent to the noise value Vnreq1 at the input terminal;

[0024] 5) Thermal noise Vnreq2 generated by the equivalent resistance Rreq2 at the negative input end.

[0025] The specific design of the present invention:

[0026] (1) Calculation of power inductor parameters: The selection of power inductor mainly includes the following aspects:

[0027] 1) Inductive reactance: much larger than the impedance of the transducer array, approximately equal to the resistance of the power resistor it replaces, that is,

[0028] ω0L≈R w

[0029] Where ω0 represents the sonar operating angular frequency; L represents the power inductance value; R w Indicates the resistance value of power resistor.

[0030] 2) Maximum current (IDC): greater than the average current when the transmitter is working;

[0031] 3) Electromagnetic interference: Select devices with magnetic shielding.

[0032] (2) Calculation of RC filter parameters of the amplifier circuit: In order to eliminate the influence of the power inductor on the receiving circuit and improve the circuit receiving efficiency, the values ​​of R1, R4, and C of the filter circuit at the input end of the amplifier circuit are optimized.

[0033] 1) Calculation method of capacitance C:

[0034]

[0035] 2) The value of resistor R1 should be considered from two aspects:

[0036] a) The resistance of R1 is much larger than the impedance of the transducer to ensure the signal receiving efficiency;

[0037] b) The bandwidth of the amplifier circuit should be greater than the sonar working bandwidth, and the low-frequency interference at the input end should be suppressed. The calculation formula for the bandwidth of the circuit input end is:

[0038]

[0039] Where ω0 represents the sonar operating angular frequency; f0 represents the sonar operating frequency; Q represents the circuit quality factor, L represents the power inductance value; R1 represents the input filter resistor value, and C represents the filter capacitor value.

[0040] 3) The value of resistor R4:

[0041] The impedance of resistor R4 is required to be much larger than the series impedance of R1 and C to eliminate their influence on the receiving circuit.

[0042] (3) Calculation of transmitting circuit parameters:

[0043] The use of the above circuit is equivalent to connecting an inductor in parallel to the transmitting circuit. During the transmitter impedance matching process, the influence of the parallel inductor on the transmitting circuit should be eliminated as much as possible.

[0044] (4) Noise calculation model:

[0045] As attached Figure 1 As shown: In the design, the capacitive reactance of C is much smaller than R1 and Rw. Ignoring its influence on signal receiving efficiency and circuit noise, the signal receiving efficiency is:

[0046]

[0047] Attached Figure 2 This is a schematic diagram of the equivalent input noise model of a general primary amplifier circuit (ignoring the influence of C, protection diodes and transducer array). The noise sources are mainly divided into five parts:

[0048] 1) Amplify the chip voltage noise Vn;

[0049] 2) Amplify the flow noise Vireq1 generated by the chip current noise In flowing through the equivalent resistor Rreq1 at the positive input end;

[0050] 3) Amplify the flow noise Vireq2 generated by the chip current noise In flowing through the negative input equivalent resistor Rreq2;

[0051] 4) Thermal noise Vnreq1 of the equivalent resistance Rreq1 at the positive input end;

[0052] 5) Thermal noise Vnreq2 generated by the equivalent resistance Rreq2 at the negative input end.

[0053] Among them: Rreq1=R1 / / Rw; Rreq2=R2 / / R3.

[0054] Any resistor above absolute zero has thermal noise. The noise spectrum is calculated as follows:

[0055]

[0056] Where k is the Boltzmann constant, k = 1.38 × 10 -23 J / K; temperature T is absolute temperature, thus:

[0057] V ireq1 =I n ·Rreq1;V ireq2 =I n Rreq2;

[0058]

[0059] By selecting low voltage and low current noise chips, Vn, Vireq1, and Vireq2 are made much smaller than Vnreq1. The feedback circuit resistors R2 and R3 are reasonably set to make Vnreq2 much smaller than Vnreq1, thus:

[0060] V total ≈V nreq1

[0061] In the design, R1 is generally much larger than Rw, Rreq1 is approximately equal to Rw, and the main noise of the circuit is the thermal noise of the power resistor.

[0062] Attached Figure 3 It is a schematic diagram of the principle of the present invention, and the signal receiving efficiency is:

[0063]

[0064] Near the operating frequency,

[0065]

[0066] Attached Figure 4 This is a schematic diagram of the equivalent input noise model of the present invention (ignoring the influence of the protection diode pair and the transducer array). The circuit noise also consists of five parts:

[0067] 1) Amplify the chip voltage noise Vn;

[0068] 2) Amplify the flow noise Vireq1 generated by the chip current noise In flowing through the equivalent impedance Zreq1 at the positive input end;

[0069] 3) Amplify the flow noise Vireq2 generated by the chip current noise In flowing through the negative input equivalent resistor Rreq2;

[0070] 4) The thermal noise of the resistor R1 at the positive input terminal is equivalent to the noise value Vnreq1 at the input terminal;

[0071] 5) Thermal noise Vnreq2 generated by the equivalent resistance Rreq2 at the negative input end.

[0072] Among them, the calculation methods of items 1, 3, and 5 are the same as those of the general amplifier circuit noise model.

[0073]

[0074] Near the operating frequency,

[0075]

[0076] V nreq1 ≈0; V ireq1 ≈0;

[0077]

[0078] Taking an actual project as an example, the equipment operating frequency is 150kHz, the bandwidth is 30kHz, the transducer impedance is about 200Ω, and the amplifier chip voltage noise Vn is The current noise is Using a common primary amplifier circuit, R w =1.5kΩ; C = 100nF; R1 = 5.1kΩ; R2 = 100Ω; R3 = 2kΩ; the signal receiving efficiency is 77.2%, and the equivalent input noise spectrum is about The in-band noise is about 0.92μVrms. Using this primary amplifier circuit, a 2.2mH power inductor L is used instead of R w ; Filter capacitor C = 470pF; R1 = 2kΩ; R4 = 15kΩ; R2 = 100Ω; R3 = 2kΩ; The signal receiving efficiency is about 100%, and the equivalent input noise spectrum is about The in-band noise is approximately 0.43μVrms.

[0079] It is understandable that, for those skilled in the art, any equivalent replacement or change to the technical solution and inventive concept of the present invention should fall within the protection scope of the claims attached to the present invention.

Claims

1. A low-noise primary amplifier circuit suitable for a transceiver transducer, characterized in that: It includes a transceiver conversion module, a filter module, and an operational amplifier circuit. The transceiver conversion module is provided with a pair of protection diodes D1, D2, D3, and D4, as well as a resistor R4 and a power inductor L. The filter module includes a resistor R1 and a capacitor C, which form a bandpass filter with the power inductor. The operational amplifier circuit is composed of a low-voltage, current noise operational amplifier and resistors R2 and R3. One end of the protection diode pair D1 and D2 of the transceiver conversion module is connected to the transmission signal, and the other end is connected to the transducer; one end of the power inductor L is connected to the transducer, and the other end is connected to the protection diode pair D3, D4 and the resistor R4; the other ends of D3, D4 and R4 are all grounded; one end of the capacitor C of the filter module is connected to the output end of the transceiver conversion module, and one end is connected to the resistor R1, and the other end of R1 is connected to the ground; the positive input end of the low voltage and current noise operational amplifier of the operational amplifier circuit is connected to the output end of the filter module, the negative input end is connected to the resistors R2 and R3, the output end is connected to the other end of R3, and the other end of R2 is connected to the ground.

2. The low-noise primary amplifier circuit suitable for a transceiver transducer according to claim 1, characterized in that: The inductive reactance of the power inductor is much larger than the impedance of the transducer array, and is approximately equal to the resistance of the replaced power resistor, that is, ω0L≈R w Where ω0 represents the sonar operating angular frequency; L represents the power inductance value; R w Indicates the resistance value of power resistor.

3. The low-noise primary amplifier circuit suitable for a transceiver transducer according to claim 1, characterized in that: The resistance of R1 is much larger than the impedance of the transducer, and the bandwidth of the amplifier circuit is larger than the working bandwidth of the sonar. At the same time, the low-frequency interference at the input end is suppressed. The calculation formula of the bandwidth at the input end of the circuit is: Where ω0 represents the sonar operating angular frequency; f0 represents the sonar operating frequency; Q represents the circuit quality factor, L represents the power inductance value; R1 represents the input filter resistor value, and C represents the filter capacitor value.

4. The low-noise primary amplifier circuit suitable for a transceiver transducer according to claim 1, characterized in that: The impedance of the resistor R4 is required to be much greater than the series impedance of R1 and C.

5. A noise decomposition method using a low-noise primary amplifier circuit suitable for a transceiver transducer, using the low-noise primary amplifier circuit suitable for a transceiver transducer as claimed in claim 1, characterized in that: The equivalent input noise model of the low-noise primary amplifier circuit decomposes the circuit noise into five parts and gives the corresponding calculation methods, including the following: 1) Amplify the chip voltage noise Vn; 2) Amplify the flow noise Vireq1 generated by the chip current noise In flowing through the equivalent impedance Zreq1 at the positive input end; 3) Amplify the flow noise Vireq2 generated by the chip current noise In flowing through the negative input equivalent resistor Rreq2; 4) The thermal noise of the resistor R1 at the positive input terminal is equivalent to the noise value Vnreq1 at the input terminal; 5) Thermal noise Vnreq2 generated by the equivalent resistance Rreq2 at the negative input terminal; Among them, Rreq1=R1 / / Rw; Rreq2=R2 / / R3; The noise spectrum calculation formula is as follows: Where k is the Boltzmann constant, k = 1.38 × 10 -23 J / K; temperature T is absolute temperature, thus: Near the operating frequency, V nreq1 ≈0;V ireq1 ≈0;

Images