| 摘要 |
An impedance matching circuit for a set-top box including a diplexer at a preceding stage having a given output impedance, and a network interface having a given input impedance different from the output impedance of the diplexer. The impedance matching circuit is connected between the diplexer and the network interface, and matches the output impedance of the diplexer to the input impedance of the network interface. Further, the impedance matching circuit includes a transformer having a primary coil and a secondary coil being connected to th e network interface, a first resistor for connecting an output end of the diplexer to an end of the primary coil of the transformer, a second resistor for connecting another output end of the diplexer to another end of the primary coil of the transformer, and a third resistor connected in parallel to the primary coil of the transforme r. In addition, the impedance matching circuit comprises a surge protection elemen t, connected in parallel to the diplexer, for protecting the impedance matching circuit from a surge voltage output from the diplexer.
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