Method and apparatus for reducing radiant noise energy
AssigneeNEC Corporation
InventorMitsuo Suzuki
Life of this patent
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Abstract
An EMI suppression apparatus allowing a common mode radiant noise energy to be reduced without attenuating a normal mode signal level is disclosed. A communication LSI has an earth terminal connected to the housing via a common mode impedance. A Common mode choke composed of two coils having a mutual inductance is provided in the housing. One coil connects a signal terminal of the communication LSI to a signal transmission wire. The other coil connects the earth terminal of the communication LSI to the quasi-ground surface of the housing. The common mode chokes causes a common mode radiant noise generated by the common mode impedance to be removed from the signal transmission wire without affecting a normal mode signal flowing through the signal transmission wire.
Claims24
A method for suppressing a radiant noise of an electronic circuit having at least one signal transmission wire connected thereto, wherein the electronic circuit includes an electronic device having an earth terminal and at least one signal terminal, the earth terminal being connected to a housing of the electronic circuit via a common mode impedance, comprising the steps of:
- forming a plurality of current paths such that a first current path affects any other current path corresponding to one of said at least one signal transmission wire;
- transmitting an output signal of an electronic device to a corresponding signal transmission wire through a corresponding one of the current paths;
- flowing a current between an earth terminal of the electronic device and a quasi-ground through the first current path;
- and
- suppressing a common mode radiant noise included in the output signal by flowing the current through the first current path.
An electronic apparatus comprising:
- a housing having at least one signal transmission wire extending to outside the housing;
- an electronic device having an earth terminal and at least one signal terminal corresponding to the at least one signal transmission wire, wherein the earth terminal is connected to the housing via a common mode impedance;
- at least one common mode choke having a plurality of coils having a mutual inductance, wherein
- one of the plurality of coils connects a signal terminal of the electronic device to a corresponding signal transmission wire, and
- another one of the plurality of coils connects the earth terminal of the electronic device to a quasi-ground surface of the housing.
An electronic apparatus comprising:
- a housing having at least one signal transmission wire extending to outside the housing;
- an electronic device having an earth terminal and at least one signal terminal corresponding to the at least one signal transmission wire, wherein the earth terminal is connected to the housing via a common mode impedance;
- at least one ferrite bead having a plurality of holes therein, wherein
- a signal wire connecting a signal terminal of the electronic device to a corresponding signal transmission wire is passed through one of the plurality of holes;
- and
- another signal wire connecting the earth terminal of the electronic device to a quasi-ground surface of the housing is passed through another one of the plurality of holes.
An electronic apparatus comprising:
- a housing having at least one signal transmission wire extending to outside the housing;
- an electronic device having an earth terminal and at least one signal terminal corresponding to the at least one signal transmission wire, wherein the earth terminal is connected to the housing via a common mode impedance;
- a resistor for generating a reference voltage from a current flowing between the housing and the earth terminal of the electronic device;
- and
- at least one operational amplifier having an inverting input terminal connected to a corresponding signal terminal of the electronic device, wherein the reference voltage is inputted at a non-inverting input terminal thereof.
Dependencies are inferred from the claim text.