Anti-interference capacitor microphone

Abstract

The utility model provides an anti-interference capacitor microphone. The anti-interference capacitor microphone comprises a capacitor sound head configured to receive an audio signal and convert the audio signal into an electric signal; the input end of the pre-amplification circuit is connected with the output end of the capacitance sound head; the input end of the impedance matching circuit is connected with the output end of the pre-amplification circuit, and the output end of the impedance matching circuit is used for being connected with a sound console; the outer sides of the capacitance sound head, the pre-amplification circuit and the impedance matching circuit are provided with metal shielding sleeves. According to the invention, the anti-interference capability of the existing condenser microphone can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of audio processing technology, and in particular to an anti-interference condenser microphone. Background Technology

[0002] A condenser microphone converts sound signals into electrical signals. These electrical signals are then processed at a mixing console and transmitted to a power amplifier. The power amplifier amplifies the electrical signals and drives the speakers in the speaker enclosure. The speakers, based on the changes in the electrical signals, convert them back into sound signals, thus amplifying the sound.

[0003] In situations where radio frequency interference exists, such as when a walkie-talkie is placed near a condenser microphone, the signal of the condenser microphone will be affected, resulting in poor sound transmission. Utility Model Content

[0004] This disclosure provides an anti-interference condenser microphone to improve the anti-interference capability of existing condenser microphones.

[0005] This disclosure provides an anti-interference condenser microphone, including:

[0006] A condenser microphone is configured to receive audio signals and convert them into electrical signals.

[0007] A preamplifier circuit, wherein the input terminal of the preamplifier circuit is connected to the output terminal of the condenser capsule;

[0008] An impedance matching circuit is provided, wherein the input terminal of the impedance matching circuit is connected to the output terminal of the preamplifier circuit, and the output terminal of the impedance matching circuit is used to connect to a mixing console.

[0009] The capacitor microphone, the preamplifier circuit, and the impedance matching circuit are all provided with metal shielding sleeves on their outer sides.

[0010] In one exemplary embodiment of this disclosure, the preamplifier circuit includes an operational amplifier U2B, a peak detection circuit, a subtraction circuit, and a first voltage setting circuit.

[0011] The non-inverting input of operational amplifier U2B is connected to the output of the capacitor capsule, the inverting input of operational amplifier U2B is grounded through resistor R1, and the output of operational amplifier U2B is fed back to the inverting input of operational amplifier U2B. The output of operational amplifier U2B is the output of the preamplifier circuit.

[0012] The output terminal of the operational amplifier U2B is connected to the input terminal of the peak detection circuit. The output terminal of the peak detection circuit is connected to the first input terminal of the subtraction circuit. The second input terminal of the subtraction circuit is connected to the second reference voltage. The output terminal of the subtraction circuit is connected to the gain control terminal of the operational amplifier U2B.

[0013] The output terminal of the first voltage setting circuit is connected to the gain control terminal of the operational amplifier U2B.

[0014] In one exemplary embodiment of this disclosure, the first voltage setting circuit includes a resistor R10 and a potentiometer RP1. The first end of the resistor R10 is connected to a power supply, and the second end of the resistor R10 is grounded through the potentiometer RP1. The second end of the resistor R10 is the output terminal of the first voltage setting circuit.

[0015] In one exemplary embodiment of this disclosure, the peak detection circuit includes a diode D1, a resistor R5, and a capacitor C1.

[0016] The anode of the diode D1 is connected to the output terminal of the operational amplifier U2B, the cathode of the diode D1 is connected to the first terminal of the capacitor C1, the second terminal of the capacitor C1 is grounded, and the capacitor R5 is connected in parallel across the two terminals of the capacitor C1.

[0017] In one exemplary embodiment of this disclosure, the anti-interference condenser microphone further includes a Zener diode, the cathode of which is connected to the output terminal of the subtraction circuit, and the anode of which is grounded.

[0018] In one exemplary embodiment of this disclosure, a bandpass filter circuit is provided between the condenser microphone and the preamplifier circuit.

[0019] In one exemplary embodiment of this disclosure, the impedance matching circuit includes operational amplifier U3B.

[0020] The non-inverting input of the operational amplifier U3B is connected to the output of the preamplifier circuit, the output of the operational amplifier U3B is fed back to the inverting input of the operational amplifier U3B, and the output of the operational amplifier U3B is the output of the impedance matching circuit.

[0021] The anti-interference condenser microphone provided in this embodiment has the following working principle and beneficial effects:

[0022] In this embodiment of the disclosure, the condenser microphone is used to convert the audio signal into a weak electrical signal. The weak electrical signal is amplified by the preamplifier circuit, and then impedance-transformed by the impedance matching circuit before being sent to the mixing console for further processing, thereby amplifying the sound signal.

[0023] Considering that the capacitance of the condenser microphone capsule is approximately tens of pF, according to the capacitive reactance calculation formula Xc=1 / (2πfC), the capacitive reactance is 3.4MΩ at 1kHz and 170MΩ at 20Hz. This indicates that the capacitive reactance of the microphone is very large. Therefore, all microphones have high impedance characteristics, and the high impedance part is particularly susceptible to external and radio frequency interference. Therefore, by setting metal shielding sleeves on the outside of the condenser microphone capsule, the preamplifier circuit, and the impedance matching circuit, the high impedance part can be protected and external interference can be shielded. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a circuit diagram of the anti-interference capacitor microphone provided in the embodiments of this disclosure. Detailed Implementation

[0026] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0027] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0028] The implementation of this disclosure will be described in detail below with reference to the specific accompanying drawings:

[0029] Figure 1 A circuit diagram of an anti-interference condenser microphone provided in an embodiment of this disclosure. (Refer to...) Figure 1 The anti-interference condenser microphone includes:

[0030] A condenser microphone is configured to receive audio signals and convert them into electrical signals.

[0031] The input terminal of the preamplifier circuit is connected to the output terminal of the condenser capsule.

[0032] Impedance matching circuit: The input of the impedance matching circuit is connected to the output of the preamplifier circuit, and the output of the impedance matching circuit is used to connect to the mixing console.

[0033] The capacitor microphone, preamplifier circuit, and impedance matching circuit are all equipped with metal shielding sleeves.

[0034] In this embodiment of the disclosure, the condenser microphone is used to convert the audio signal into a weak electrical signal. The weak electrical signal is amplified by the preamplifier circuit, and then impedance-transformed by the impedance matching circuit before being sent to the mixing console for further processing, thereby amplifying the sound signal.

[0035] Considering that the capacitance of the condenser microphone capsule is approximately tens of pF, according to the capacitive reactance calculation formula Xc=1 / (2πfC), the capacitive reactance is 3.4MΩ at 1kHz and 170MΩ at 20Hz. This indicates that the capacitive reactance of the microphone is very large. Therefore, all microphones have high impedance characteristics. The high impedance part is particularly susceptible to external and radio frequency interference. Therefore, by setting metal shielding sleeves on the outside of the condenser microphone capsule, preamplifier circuit, and impedance matching circuit, the high impedance part can be protected and external interference can be shielded.

[0036] In one exemplary embodiment of this disclosure, the preamplifier circuit includes operational amplifier U2B, a peak detection circuit, a subtraction circuit, and a first voltage setting circuit.

[0037] The non-inverting input of op-amp U2B is connected to the output of the condenser capsule, and the inverting input of op-amp U2B is grounded through resistor R1. The output of op-amp U2B is fed back to the inverting input of op-amp U2B, and the output of op-amp U2B is the output of the preamplifier circuit.

[0038] The output of operational amplifier U2B is connected to the input of the peak detection circuit. The output of the peak detection circuit is connected to the first input of the subtraction circuit. The second input of the subtraction circuit is connected to the second reference voltage. The output of the subtraction circuit is connected to the gain control terminal of operational amplifier U2B.

[0039] The output of the first voltage setting circuit is connected to the gain control terminal of operational amplifier U2B.

[0040] In this embodiment, the preamplifier circuit uses an operational amplifier U2B with gain adjustment function. For example, a general-purpose operational amplifier such as TL081 or LM324 can be selected. By providing different voltage signals to the gain control terminal of the operational amplifier U2B through the first voltage setting circuit, the amplification factor of the operational amplifier U2B can be adjusted, that is, the amplification factor of the preamplifier circuit can be adjusted, so as to amplify the electrical signal output by the capacitor tone capsule to the set voltage level.

[0041] Furthermore, this embodiment, based on the first voltage setting circuit, includes a peak detection circuit and a subtraction circuit to achieve automatic gain adjustment of operational amplifier U2B. Its working principle is as follows: the peak detection circuit detects the peak voltage at the output of the preamplifier circuit. The output of the peak detection circuit is connected to the first input (specifically, the inverting input) of the subtraction circuit. When the voltage at the output of the preamplifier circuit is greater than the second reference voltage, the output voltage of the subtraction circuit is negative. The output of the subtraction circuit is connected to the gain control terminal of operational amplifier U2B and superimposed with the given voltage output by the first voltage setting circuit. Since the output voltage of the subtraction circuit is negative, the gain of operational amplifier U2B is reduced, and the voltage at the output of the preamplifier circuit decreases. When the voltage at the output of the preamplifier circuit is less than the second reference voltage, the output voltage of the subtraction circuit is positive, increasing the gain of operational amplifier U2B, and the voltage at the output of the preamplifier circuit increases. Therefore, through the above process, the gain of operational amplifier U2B is adjusted according to the magnitude of the voltage at the output of the preamplifier circuit, maintaining a stable voltage output.

[0042] The subtraction circuit is implemented by operational amplifier U3A, resistor R9, and resistor R8. The amplification factor of the subtraction circuit can be adjusted by adjusting the resistance values ​​of resistors R9 and R8.

[0043] As can be seen from the above, the configuration of the peak detection circuit, the subtraction circuit and the first voltage setting circuit in this embodiment can stabilize the voltage at the output of the preamplifier circuit within the set range. The stable voltage signal is input to the subsequent mixing console and speaker, which is beneficial for the speaker to output a stable audio signal.

[0044] In one exemplary embodiment of this disclosure, the first voltage setting circuit includes a resistor R10 and a potentiometer RP1. The first end of the resistor R10 is connected to a power supply, and the second end of the resistor R10 is grounded through the potentiometer RP1. The second end of the resistor R10 is the output terminal of the first voltage setting circuit.

[0045] In this embodiment, resistor R10 and potentiometer RP1 form a series voltage divider circuit. The output voltage at the second end of resistor R10 is used as the first given voltage. The circuit structure is simple and easy to operate. According to actual needs, the magnitude of the first given voltage can be adjusted by adjusting the resistance value of potentiometer RP1, thereby adjusting the gain of operational amplifier U2B.

[0046] In one exemplary embodiment of this disclosure, the peak detection circuit includes a diode D1, a resistor R5, and a capacitor C1.

[0047] The anode of diode D1 is connected to the output terminal of operational amplifier U2B, the cathode of diode D1 is connected to the first terminal of capacitor C1, the second terminal of capacitor C1 is grounded, and capacitor R5 is connected in parallel across the two terminals of capacitor C1.

[0048] In this embodiment, diode D1, resistor R5, and capacitor C1 constitute a peak detection circuit. Its working principle is as follows: During the positive half-cycle of the op-amp U2B output voltage, diode D1 conducts, charging capacitor C1 and increasing its voltage. When the voltage of capacitor C1 reaches the op-amp U2B output voltage, its voltage stops increasing. During the negative half-cycle of the op-amp U2B output voltage, diode D1 is turned off, and capacitor C1 discharges through resistor R5, preparing for the next charging cycle. Through this process, the voltage of capacitor C1 changes with the peak value of the op-amp U2B output voltage. By detecting the voltage of capacitor C1, the peak value of the op-amp U2B output voltage can be obtained.

[0049] As can be seen from the above, the arrangement of diode D1, resistor R5 and capacitor C1 in this embodiment enables the detection of the peak output voltage of the preamplifier circuit, providing a basis for subsequent gain adjustment of the preamplifier circuit.

[0050] In one exemplary embodiment of this disclosure, the anti-interference condenser microphone further includes a Zener diode, the cathode of which is connected to the output terminal of the subtraction circuit, and the anode of which is grounded.

[0051] In this embodiment, Zener diode U1 acts as a limiter. When the output voltage of the subtraction circuit is greater than the stable voltage of Zener diode U1, Zener diode U1 limits the output voltage of the subtraction circuit to the stable voltage of Zener diode U1, thus preventing excessively high voltage from being input to the gain control terminal of operational amplifier U2B and causing signal distortion.

[0052] As can be seen from the above, the setting of the Zener diode in this embodiment can effectively avoid signal distortion caused by excessive gain of operational amplifier U2B.

[0053] In one exemplary embodiment of this disclosure, a bandpass filter circuit is provided between the condenser microphone and the preamplifier circuit.

[0054] In this embodiment, resistor R26 and capacitor C5 form a low-pass filter circuit to filter out high-frequency signals; capacitor C6 and resistor R25 form a high-pass filter circuit to filter out low-frequency signals. The above circuit and operational amplifier U2A constitute an active bandpass filter circuit, allowing only audio signals (frequency range 85Hz - 1100Hz) to pass through, preventing low-frequency or high-frequency interference signals from entering subsequent circuits, thereby improving the accuracy of audio signal acquisition.

[0055] In one exemplary embodiment of this disclosure, the impedance matching circuit includes operational amplifier U3B.

[0056] The non-inverting input of op-amp U3B is connected to the output of the preamplifier circuit, the output of op-amp U3B is fed back to the inverting input of op-amp U3B, and the output of op-amp U3B is the output of the impedance matching circuit.

[0057] In this embodiment, operational amplifier U3B forms a voltage follower. The voltage follower has a high input impedance and a low output impedance, thereby achieving impedance matching between the preamplifier circuit and the subsequent circuit.

[0058] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure.

Claims

1. An anti-interference condenser microphone, characterized in that, include: A condenser microphone is configured to receive audio signals and convert them into electrical signals. A preamplifier circuit, wherein the input terminal of the preamplifier circuit is connected to the output terminal of the condenser capsule; An impedance matching circuit is provided, wherein the input terminal of the impedance matching circuit is connected to the output terminal of the preamplifier circuit, and the output terminal of the impedance matching circuit is used to connect to a mixing console. The capacitor microphone, the preamplifier circuit, and the impedance matching circuit are provided with metal shielding sleeves on their outer sides. The preamplifier circuit includes operational amplifier U2B, peak detection circuit, subtraction circuit, and first voltage setting circuit. The non-inverting input of operational amplifier U2B is connected to the output of the capacitor capsule, the inverting input of operational amplifier U2B is grounded through resistor R1, and the output of operational amplifier U2B is fed back to the inverting input of operational amplifier U2B. The output of operational amplifier U2B is the output of the preamplifier circuit. The output terminal of the operational amplifier U2B is connected to the input terminal of the peak detection circuit. The output terminal of the peak detection circuit is connected to the first input terminal of the subtraction circuit. The second input terminal of the subtraction circuit is connected to the second reference voltage. The output terminal of the subtraction circuit is connected to the gain control terminal of the operational amplifier U2B. The output terminal of the first voltage setting circuit is connected to the gain control terminal of the operational amplifier U2B.

2. The anti-interference condenser microphone as described in claim 1, characterized in that, The first voltage setting circuit includes a resistor R10 and a potentiometer RP1. The first end of the resistor R10 is connected to the power supply, and the second end of the resistor R10 is grounded through the potentiometer RP1. The second end of the resistor R10 is the output terminal of the first voltage setting circuit.

3. The anti-interference condenser microphone as described in claim 1, characterized in that, The peak detection circuit includes diode D1, resistor R5, and capacitor C1. The anode of the diode D1 is connected to the output terminal of the operational amplifier U2B, the cathode of the diode D1 is connected to the first terminal of the capacitor C1, the second terminal of the capacitor C1 is grounded, and the capacitor R5 is connected in parallel across the two terminals of the capacitor C1.

4. The anti-interference condenser microphone as described in claim 1, characterized in that, It also includes a Zener diode, the cathode of which is connected to the output terminal of the subtraction circuit, and the anode of which is grounded.

5. The anti-interference condenser microphone as described in claim 1, characterized in that, A bandpass filter circuit is provided between the condenser microphone and the preamplifier circuit.

6. The anti-interference condenser microphone as described in claim 1, characterized in that, The impedance matching circuit includes operational amplifier U3B. The non-inverting input of the operational amplifier U3B is connected to the output of the preamplifier circuit, the output of the operational amplifier U3B is fed back to the inverting input of the operational amplifier U3B, and the output of the operational amplifier U3B is the output of the impedance matching circuit.

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