| 摘要 |
In a frequency converter for community systems and cable distribution systems with an input converter with mixing stage, in which the received frequency is mixed with a frequency generated by a voltage-controlled oscillator, a frequency synthesis circuit with programmable divider is provided for the tuning. The output converter similarly exhibits a free programmable frequency or voltage synthesis circuit for tuning and for generating a second oscillator frequency for mixing it with that present from the input converter. To provide for individual tuning of the input and output converter to various frequencies without calibrating the circuits, the adjustment variables significant for the tuning are determined in a tuning process, including all frequency-changing parameters of the circuit, and are stored in a memory. This memory is activated by a microprocessor which optionally switches through the corresponding adjustment values to the adjustment elements of the input and output converter.
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