Condenser microphone

An exemplary condenser microphone includes a printed circuit board, a first via, a second via, and a number of through holes. The first and second vias are formed in the printed circuit board for the signal line and ground line respectively passing therethrough. The through holes are formed surrounding the first and second vias. Inner walls of the through holes are coated with a conductive material.

BACKGROUND

1. Field of the Invention

The present invention relates to condenser microphones and, more particularly, to a condenser microphone capable of reducing acoustic noise from high-frequency sources.

2. Description of the Related Art

Condenser microphones are used in many portable electronic devices, such as digital video cameras, digital still cameras, and mobile phones. One of the challenges of utilizing condenser microphones in electronic devices is that noise generated by high-frequency components in the electronic devices may affect recording quality.

What is needed, therefore, is a condenser microphone that can overcome the above-described shortcoming.

SUMMARY

An exemplary condenser microphone apparatus includes a printed circuit board, a first via, a second via, and a number of through holes. The first and second vias are formed in the printed circuit board for the signal line and ground line respectively passing therethrough. The through holes are formed surrounding the first and second vias. Inner walls of the through holes are coated with a conductive material.

DETAILED DESCRIPTION

Embodiments of the present condenser microphone will now be described in detail below, with reference to the drawings.

Referring toFIG. 1, a condenser microphone100is shown. The condenser microphone100is formed by successively inserting a polar ring102, a diaphragm104, a spacer103, an insulating ring105, an electrode plate106, a conductive pattern107, and a printed circuit board (PCB)130into a cylindrical case110. The polar ring102is disposed on the top end of the cylindrical case110and the diaphragm104is disposed on one side of the polar ring102. The electrode plate106is disposed on the diaphragm104with the spacer103positioned therebetween. The top end of the cylindrical case110is provided with a number of sound holes101. The diaphragm104is electrically connected to the cylindrical case110through the polar ring102that is formed of a conductive material. The diaphragm104and the polar ring102may be integrally formed as a single body.

The electrode plate106is formed of a metal plate coated with an organic (polymer) film on which the electrode is formed. The electrode plate106is insulated from the cylindrical case110by the insulating ring105. Moreover, the electrode plate106is supported by the conductive pattern107and is electrically connected to the PCB130via the conductive pattern107. A circuit component108, such as a junction field effect transistor (JFET), is embedded in the PCB130. The electrode plate106, the conductive pattern107, and the PCB130cooperatively define a back chamber120. In this embodiment, when sound waves strike the condenser microphone100through the sound holes101, the diaphragm104vibrates. The sound waves also enter the back chamber120. When the diaphragm104vibrates, the interval between the diaphragm104and the electrode plate106varies thereby varying electrostatic capacity generated by the diaphragm104and the electrode plate106. As a result, a voltage signal is varied according to the sound waves. The voltage signal is transmitted to the circuit component108such as the JFET embedded in the PCB130and amplified. The amplified voltage signal is externally transmitted through a connection terminal (not shown).

Referring toFIG. 2, the PCB130embedded in the condenser microphone100is shown according to a first exemplary embodiment. The PCB130defines a first via131, and a second via132therein. A signal line140and a ground line150corresponding to the first via131and the second via132are inserted through the PCB130respectively and soldered thereto, thereby electrically connecting a digital signal processor (DSP) (not shown) to the PCB130. The PCB130defines a number of through holes133arranged around the signal line140and the ground line150along the edge of the PCB130. In this embodiment, the signal line140and the ground line150, each has three through holes133therearound, and the distances from the first via131or the second via132to their corresponding through holes133are the same. Inner walls of the through holes133are formed with a conductive coating such as copper. Induction/capacitance introduced in the through holes133corresponding to the signal line140can shorten a backflow route of the signal line140, thereby reducing characteristic impedance of signals transmitted via the signal line140and edge rate of the signals. Characteristics of the capacitance can be manipulated by adjusting the number, shape, and dimensions of the coated through holes133to reduce noise interference from the high frequency signals transmitted through the signal line140that might interfere with the microphone100. In this embodiment, the number of the through holes133is six and cross-sectional shape of each through hole133is circular shape. In other embodiments, more or less through holes can be used and cross-sectional shapes other than circular, such as hexagonal may be used.

Referring toFIG. 3, another PCB230embedded in the condenser microphone100is shown according to a second exemplary embodiment. The second exemplary embodiment is identical to the first exemplary embodiment except that the PCB230has a number of through holes233distributed between the first via131and the second via132of the PCB230. The number of the through holes233is four and they form a square pattern. Other aspects of the second embodiment are the same as that of the first embodiment, and are not described in detail.

The present condenser microphone100has the through holes133,233, with the conductive coating formed on the inner wall thereof, positioned adjacent to the signal line140and the ground line150. Thus, noise interference to the microphone100from the high frequency signals transmitted through the signal line140is reduced.

While certain embodiments have been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.