JPH04334297A - Digital microphone - Google Patents

Abstract

PURPOSE:To convert the sound wave directly into the digital sound signal. CONSTITUTION:An oscillation part 2 has opposing electric stations 11, 12, oscillates a receiving sound part 1 for which the capacitance changes according to the sound wave as a part of the resonance circuit and transmits an oscillation signal S1. A reference frequency generation part 3 generates a reference signal S3 having the frequency which is almost equal to the frequency of the oscillation signal S1 in the silent state. A mixture part 4 receives the oscillation signal S1 and the reference signal S3 and generates a signal S2 having the frequency of the difference of the both signals. A counter part 5 counts the frequency of the signal S2 and the countes value is outputted as digital data D1. A gate part 7 generates a digital parallel signal D2 by sampling the digital data D1 by a sampling clock C and a parallel serial conversion part 8 converts the digital parallel signal D2 into the prescribed format serial digital sound signal D3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital microphone, and more particularly to a digital microphone that directly converts sound waves into digital audio signals.

0002

BACKGROUND OF THE INVENTION Conventional microphones convert sound waves directly into analog audio signals. Therefore, when used in a digital system, the analog audio signal of this microphone is amplified and then converted to a digital audio signal by an analog-to-digital converter.

0003

In conventional microphones, a digital audio signal is obtained through an analog-to-digital converter, so there is a problem in that the fidelity is affected by the performance of the analog-to-digital converter. Further, in addition to the microphone, an amplifier, an analog-to-digital converter, etc. are required, which has the disadvantage of complicating the configuration.

An object of the present invention is to provide a digital microphone that directly converts sound waves into digital audio signals.

[0005]

[Means for Solving the Problems] The digital microphone of the present invention includes a sound receiving section having opposing electrodes whose capacitance changes according to sound waves, and a sound receiving section that oscillates as the capacitance of a resonant circuit to generate an oscillation signal. an oscillating section that generates a reference signal having a frequency approximately equal to the frequency of the oscillation signal in a silent state; A mixing section that generates a signal, a counter section that counts the frequency of the output signal of the mixing section and outputs the counted value as digital data, and means that converts the digital data into a predetermined serial digital audio signal. There is.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a microphone showing one embodiment of the present invention. The sound receiving section 1 includes a conductive sound receiving diaphragm 11 and a conductive fixed plate 1 disposed opposite to the conductive sound receiving diaphragm 11.
2 and functions as a capacitor, and when the diaphragm 11 vibrates due to sound pressure, the capacitance changes. The oscillating section 2 oscillates the sound receiving section 1 as a capacitance of a resonant circuit, and outputs a signal S1.

The reference frequency generator 3 outputs a signal S3 having a frequency close to the frequency of the oscillation signal S1 during silence. The mixing unit 4 outputs a signal S2 that is the difference in frequency between the signals S1 and S3. The frequency counter section 5 counts the frequency of the signal S2 and outputs the digital data D1. The sampling clock generator 6 outputs a clock C having a sampling frequency of the digital audio signal. The gate section 7 cuts out the digital data D1 from the frequency counter 5 using the clock C and outputs a digital parallel signal D2. The parallel-serial converter 8 converts the digital parallel signal D
2 into, for example, AES/EBU or EIAJ format and output as a serial digital audio signal D3.

[0009]

[Effects of the Invention] As explained above, the present invention generates an oscillation signal whose frequency changes according to the sound wave by causing a counter electrode whose capacitance changes when vibrated by a sound wave to oscillate as part of a resonant circuit. On the other hand, a reference signal with a frequency almost equal to the frequency of the oscillation signal in a silent state is generated, a signal with a frequency difference between the oscillation signal and the reference signal is generated, and the frequency of this difference is counted to generate digital data. By converting digital data into a predetermined serial digital audio signal, it is possible to directly convert sound waves into digital audio signals, eliminating the need to convert analog audio signals into digital audio signals using an analog-to-digital converter as in the past. , there is no characteristic deterioration due to the converter,
It also has the advantage of being able to interface directly to digital audio systems.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

[Explanation of symbols]

1 Sound receiving section 2 Oscillation section 3. Reference frequency generation section 4 Mixing section 5 Counter section 6 Sampling clock generation section 7 Gate part 8 Parallel-serial conversion section S1 Oscillation signal S3 Reference signal D1 Digital data

Claims (1)

[Claims] 1. A sound receiving section having opposing electrodes and having a capacitance that changes according to the sound wave; an oscillating section that uses the sound receiving section as a capacitance of a resonant circuit to oscillate and send out an oscillation signal; a reference frequency generating section that generates a reference signal with a frequency substantially equal to the frequency of the oscillation signal; a mixing section that receives and mixes the oscillation signal and the reference signal to generate a signal with a frequency that is the difference between the two signals; and the mixing section What is claimed is: 1. A digital microphone comprising: a counter section that counts the frequency of an output signal of the microphone and outputs the counted value as digital data; and means that converts the digital data into a predetermined serial digital audio signal.