Fully differential output vector acoustic sensor

Abstract

The invention discloses a fully differential output vector acoustic sensor, which comprises a metal cap, a printed circuit board, an MEMS acoustic sensitive structure and a special acoustic-electric conversion circuit, the metal cap is fixed on the surface of the printed circuit board, and a cavity is formed in the middle; the MEMS acoustic sensitive structure and the special acoustic-electric conversion circuit are arranged in a cavity formed by the metal cap and the printed circuit board, and the MEMS acoustic sensitive structure and the special integrated circuit are welded on the printed circuit board in an inverted mode and are electrically connected through a wire on the printed circuit board. According to the fully differential output vector acoustic sensor, the two mutually coupled sensing units are adopted to output signals to the special acoustic-electric conversion circuit and finally output in a differential mode, the average value of the two output ports can achieve measurement of standard sound pressure signals in a sound field, and the difference value of the two output ports can achieve measurement of sound pressure gradient vector signals in the sound field. The differential structure can also improve the linearity of microphone output and suppress the influence of common-mode interference signals such as temperature on the acoustic performance.

Description

Technical Field

[0001] The present invention relates to the field of MEMS technology, and in particular to a fully differential output vector acoustic sensor. Background Art

[0002] Bottom-inlet microphones have a relatively small front cavity and a relatively large back cavity, and have advantages over top-inlet microphones in terms of operating frequency, signal-to-noise ratio, and sensitivity. Existing MEMS microphones are basically scalar microphones that can only measure scalar information of sound pressure. The sound field also has vector information such as velocity, acceleration, and sound pressure gradient. The measurement of vector information can more comprehensively reflect the sound field information. Fully differential output microphones can improve the linearity of microphone output while reducing the impact of common-mode interference signals such as temperature on acoustic performance. Therefore, it is of great significance to study bottom-inlet fully differential output vector microphones. Summary of the invention

[0003] The purpose of the present invention is to provide a fully differential output vector acoustic sensor in order to achieve the measurement of sound field vector signals, improve the linearity of microphone output, and suppress the influence of common mode interference signals such as temperature on acoustic performance.

[0004] The technical solution of the present invention is: A fully differential output vector acoustic sensor comprises a metal cap, a printed circuit board, a MEMS acoustic sensitive structure and a dedicated acoustic-to-electric conversion circuit; the metal cap is fixed to the surface of the printed circuit board to form a cavity in the middle; the MEMS acoustic sensitive structure and the dedicated acoustic-to-electric conversion circuit are arranged in the cavity formed by the metal cap and the printed circuit board, the MEMS acoustic sensitive structure and the dedicated integrated circuit are flip-chip welded on the printed circuit board, and electrical connection is achieved through the wires on the printed circuit board; a sound inlet hole is provided on the printed circuit board.

[0005] Preferably, the MEMS acoustic sensing structure comprises an anchor point, two mutually coupled acoustic sensing units and two mutually isolated lower electrodes; The two acoustic sensing units are symmetrically distributed on both sides of the bottom of the anchor point, the two acoustic sensing units are rigidly connected by two connecting beams, and the two connecting beams are elastically suspended at the bottom of the anchor point through two torsion beams; The two lower electrodes are symmetrically distributed on both sides of the middle of the anchor point, respectively located directly above the two sound sensitive units, and a plurality of damping holes are distributed on the two lower electrodes.

[0006] Preferably, two stop structures symmetrically distributed about the anchor point are arranged outside the two lower electrodes, and the stop structures prevent the acoustic sensitive unit from excessive displacement and structural damage.

[0007] Preferably, there are two sound inlet holes on the printed circuit board, which respectively correspond to the positions of two sound sensitive units.

[0008] The advantages of the present invention are: The fully differential output vector acoustic sensor of the present invention adopts two mutually coupled sensitive units to output to a dedicated acoustic-to-electric conversion circuit, and finally outputs differentially. The average value of the two output ports can realize the measurement of the scalar sound pressure signal in the sound field, and the difference of the two output ports can realize the measurement of the sound pressure gradient vector signal in the sound field, thereby improving the linearity of the microphone and suppressing the influence of common-mode interference signals such as temperature on the acoustic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 A cross-sectional view of a fully differential output vector acoustic sensor; Figure 2 It is a cross-sectional view of the MEMS sensitive structure; Figure 3 It is a top view of the MEMS sensitive structure; Figure 4 This is the distribution diagram of the sound holes on the printed circuit board. DETAILED DESCRIPTION

[0010] like Figure 1 As shown, the fully differential output vector acoustic sensor of the present invention comprises a metal cap 1, a printed circuit board 2, a MEMS acoustic sensitive structure 3 and a dedicated acoustic-to-electric conversion circuit 4. The metal cap 1 is fixed to the surface of the printed circuit board 2, forming a cavity in the middle; the MEMS acoustic sensitive structure 3 and the dedicated acoustic-to-electric conversion circuit 4 are arranged in the cavity formed by the metal cap 1 and the printed circuit board 2, and the MEMS acoustic sensitive structure 3 and the dedicated integrated circuit 4 are flip-chip soldered on the printed circuit board 2, and are electrically connected through the wires on the printed circuit board 2.

[0011] like Figure 2 , 3 As shown, the MEMS acoustic sensing structure includes an anchor point 32, two acoustic sensing units 31 and two lower electrodes 33; the two acoustic sensing units 31 are coupled to each other and symmetrically distributed on both sides of the bottom of the anchor point 32, and the two acoustic sensing units 31 are connected by two connecting beams 38, and the two connecting beams 38 are elastically suspended at the bottom of the anchor point 32 through two torsion beams 37; The two lower electrodes 33 are symmetrically distributed on both sides of the middle of the anchor point 32 , and are respectively located directly above the two acoustic sensitive units 31 . The two lower electrodes 31 are physically isolated from each other, and a plurality of damping holes 34 are distributed on the two lower electrodes 31 .

[0012] Two stopper structures 35 symmetrically distributed about the anchor point 31 are arranged outside the two lower electrodes 31 . The stopper structures 35 prevent the acoustic sensing unit from excessive displacement and structural damage.

[0013] The bottom ends of the two lower electrodes 31 are connected with bonding rings 36 . The bonding rings 36 not only physically protect sensitive structures, but also are used to form a common upper electrode pad 30 and two lower electrode pads 39 .

[0014] like Figure 4 As shown, the printed circuit board 2 is provided with sound inlet holes 21 corresponding to the positions of the two sound sensitive units. The outputs of the two sound sensitive units 31 are input to the dedicated sound-to-electric conversion circuit 4 through gold wires, and finally differentially output. The average value of the two output ports can realize the measurement of the scalar sound pressure signal in the sound field, and the difference between the two output ports can realize the measurement of the sound pressure gradient vector signal in the sound field.

[0015] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any modifications made according to the spirit of the main technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A fully differential output vector acoustic sensor, characterized in that: It includes a metal cap, a printed circuit board, a MEMS sound-sensitive structure and a dedicated sound-to-electric conversion circuit; the metal cap is fixed to the surface of the printed circuit board to form a cavity in the middle; the MEMS sound-sensitive structure and the dedicated sound-to-electric conversion circuit are arranged in the cavity formed by the metal cap and the printed circuit board, the MEMS sound-sensitive structure and the dedicated integrated circuit are flip-chip welded on the printed circuit board, and electrical connection is achieved through the wires on the printed circuit board; a sound inlet hole is provided on the printed circuit board.

2. The fully differential output vector acoustic sensor according to claim 1, characterized in that: The MEMS acoustic sensing structure includes an anchor point, two mutually coupled acoustic sensing units and two lower electrodes; The two acoustic sensing units are symmetrically distributed on both sides of the bottom of the anchor point, the two acoustic sensing units are rigidly connected by two connecting beams, and the two connecting beams are elastically suspended at the bottom of the anchor point through two torsion beams; The two lower electrodes are symmetrically distributed on both sides of the middle of the anchor point, respectively located directly above the two sound sensitive units, and a plurality of damping holes are distributed on the two lower electrodes.

3. The fully differential output vector acoustic sensor according to claim 2, characterized in that: Two stopper structures symmetrically distributed about the anchor point are arranged outside the two lower electrodes, and the stopper structures prevent the acoustic sensitive unit from excessive displacement and structural damage.

4. The fully differential output vector acoustic sensor according to claim 2, characterized in that: There are two sound inlet holes on the printed circuit board, which correspond to the positions of the two sound sensitive units respectively.

Images