A radio receiver used in the AM system is shown in Fig. 3-25. The mixer translates the carrier frequency fe to a fixed IF of 455 kHz by using a local oscillator of frequency fo. The broadcast-band frequencies range from 540 to 1600 kHz. Determine the range of tuning that must be provided in the local oscillator when fo is higher than fe (superheterodyne receiver).
Antenna
RF section
IF section
Envelope detector
Mixer
Common tuning
Local oscillator
Audio amplifier
Speaker
Fig. 3-25: A superheterodyne AM receiver