In a typical superheterodyne receiver the incoming radio signal from the antenna is passed through a tunable RF bandpass filter to attenuate some undesired signals, amplified in a radio frequency amplifier, and mixed with a sine wave produced by a local oscillator. The mixer produces a signal at a lower frequency than the RF signal called Intermediate Frequency (I F). In other words, the mixer demodulates the incoming signal from fRF down to f I F. The IF bandpassfilter removes all but the desired I F signal centered at f I F.

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