Final answer:
With a zero frequency error in a demodulator, the output would be the original baseband message signal with minimal distortion, assuming other factors are also ideal. The demodulator can accurately extract the information from the carrier wave under these conditions.
Step-by-step explanation:
If the frequency error of a signal being input into a demodulator is zero, it means that there is no discrepancy between the expected carrier frequency and the actual carrier frequency of the received signal. In such a case, a demodulator would output the original baseband signal or message signal with minimal distortion or errors. This assumes that other factors such as noise, phase errors, or signal strength variations are also minimal or compensated for.
The demodulator's main function is to extract the useful information from the carrier wave. With a zero frequency error, the demodulator can effectively and accurately recover the original information as it maintains proper synchronization with the incoming signal, which is crucial in various forms of modulation such as Frequency Modulation (FM) or Phase Modulation (PM).