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The radio signal undergoes significant processing
after it reaches the interferometer. The following diagram is the frequency
domain representation of a typical signal at an RF center frequency of fc for
one antenna (station "X") of the interferometer. The signal emitted by
the radio source contains no Doppler shift other than that due to its own
motion. The signal at the antenna feed contains a Doppler shift due to the
relative motion of the source and the antenna. Once the signal is in the
receiver, noise is added to it due to the inherent noise of the receiver
electronics.
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