| 摘要 |
Noise generated in a computer system on a modem adapter card (100) is effectivel y suppressed by providing an extension to a voltage reference plane (212). The extension reference plane is coupled to the voltage r eference plane of the adapter card by an impedance circuit (350, 352). The extension reference plane causes the adapter card to have a comp osite reference plane with has an overall length greater than one-quarter of the wavelength of the signal to be suppressed such that the composite reference plane does not resonate at the frequency of the signal which generated the noise. The reference planes are preferably con nected by a resonant circuit so that the two reference planes are effectively electrically connected at high frequencies and are electrically disconnected at low frequencies so that resonance of the boards is also suppressed at lower frequencies.
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