Variable-directivity MEMS microphone and electronic device

1. A variable-directivity MEMS (Micro-Electro-Mechanical system) microphone, comprising an acoustic cavity, wherein the following components are provided inside the acoustic cavity:

a first acoustic transducer for detecting an acoustic signal and converting the acoustic signal into a first acoustic conversion signal;

a first pre-amplifier, connected to the first acoustic transducer, and configured for outputting a first electric signal;

a second acoustic transducer for detecting a second acoustic signal and converting the detected second acoustic signal into a second acoustic conversion signal;

a second pre-amplifier, connected to the second acoustic transducer, and configured for outputting a second electric signal; and

a signal processing chip, connected to the first pre-amplifier and the second pre-amplifier, and configured for generating a directional output signal by performing an arithmetic operation on the first electric signal and the second electric signal under the action of a switching control signal;

the signal processing chip comprises:

a phase delayer, an output end of which is connected to the second electric signal, and the second electric signal is delayed by a predetermined phase based on the control signal, then a phase-delayed second electric signal is output;

an adder-subtractor for outputting the directional output signal after performing addition and subtraction operations on the first electric signal and the phase-delayed second electric signal;

wherein the phase delayer comprises:

an operational amplifier having a non-inverting input terminal and an inverting input terminal, an output terminal of the operational amplifier outputs the phase-delayed second electric signal;

a first resistor and a second resistor, connected in series between the input end of the phase delayer and the non-inverting input terminal;

a first capacitor, connected between the non-inverting input terminal and the ground;

a second capacitor, wherein one end of the second capacitor is connected at a joint where the first resistor and the second resistor are connected, the other end of the second capacitor is connected to the output terminal of the operational amplifier;

a third resistor, connected between the inverting input terminal and the ground;

a fourth resistor, connected between the inverting input terminal and the output end.

2. The variable-directivity MEMS microphone of claim 1 , wherein the adder-subtractor performs an addition operation or a subtraction operation on the first electric signal or the phase-delayed second electric signal in a controlled manner.

3. The variable-directivity MEMS microphone of claim 1 , comprising a substrate and a cover covering the substrate, wherein the substrate and the cover forms the acoustic cavity.

4. The variable-directivity MEMS microphone of claim 3 , wherein the first acoustic transducer, the first pre-amplifier, the second acoustic transducer, the second pre-amplifier and the signal processing chip are arranged on the substrate, and the substrate is provided with a first acoustic through-hole and a second acoustic through-hole.

5. The variable-directivity MEMS microphone of claim 3 , wherein the first acoustic transducer and the first pre-amplifier are provided on the cover, the second acoustic transducer and the second pre-amplifier are provided on the substrate, the signal processing chip is optionally provided on the substrate or the cover, and an acoustic through-hole is formed in the substrate and the cover, respectively.

6. The variable-directivity MEMS microphone of claim 1 , wherein the directional output signal is an omnidirectional output signal or a splayed directional output signal or a cardioid directional output signal.

7. An electronic device comprising the variable-directivity MEMS microphone of claim 1 , wherein the electronic device is provided with a control switch for providing the switching control signal.

8. The electronic device of claim 7 , wherein the control switch comprises an omnidirectional selector switch, a splayed selector switch, and a cardioid selector switch.