Circuit configuration for producing a quadrature-amplitude-modulated transmission signal

A circuit configuration for producing a quadrature-amplitude-modulated transmission signal, comprising:

• a coder having an input for receiving a digital user signal and outputs for outputting a real part and an imaginary part of a quadrature-amplitude-modulated (QAM) signal to be transmitted;
• a device for digital conversion of the QAM signal to be transmitted to a radio-frequency band, said device connected to said coder and having a first input for receiving the real part and a second input for receiving the imaginary part of the QAM signal, said device having a first output for outputting the real part and a second output for outputting the imaginary part;
• a first interpolation filter connected to said first output of said device for receiving the real part;
• a second interpolation filter connected to said first output of said device for receiving the real part;
• a third interpolation filter for receiving the imaginary part;
• a multiplexer connected to said second interpolation filter and said third interpolation filter to switch between said second interpolation filter and said third interpolation filter at an output frequency;
• a terminal connected to said multiplexer and at which the QAM signal may be tapped off, the QAM signal containing sample values sampled at the output frequency;
• and
• a switching device connected to said device, said first interpolation filter, said second interpolation filter and said third interpolation filter, in a first setting of said switching device said first interpolation filter connected to said first output for the real part of said device, and in a second setting of said switching device said second interpolation filter connected to said first output for the real part of said device and said third interpolation filter connected to said second output for the imaginary part of said device, said switching device being controllable in dependence on the output frequency.