| 摘要 |
The invention relates to a method and an arrangement implementing the method for implementing the transmitter operation of a digital data transmission system. The method comprises the steps of converting an information signal to be transmitted into a first intermediate-frequency signal such that the first intermediate-frequency signal is processed to a desired frequency band, and converting the first intermediate-frequency signal into a variable-frequency signal on the above mentioned frequency band, and filtering away interference signals. The method further comprises the steps of mixing the first intermediate-frequency signal with a fixed-frequency signal in order to generate a second intermediate-frequency signal such that the second intermediate-frequency signal is a variable-frequency signal similarly as the first intermediate-frequency signal, converting the second intermediate-frequency signal into an output signal to a transmission band width which is in its entirety at a higher frequency range than the second intermediate-frequency signal, and converting the second intermediate-frequency signal into the output signal such that the output signal is adapted to frequency changes of the second intermediate-frequency signal.
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