In a superheterodyne receiver, the received AM wave is used to modulate the frequency of a tunable oscillator. The result is bandpass-filtered to produce a modulated signal at a fixed carrier frequency that can then be used for demodulation with a fixed circuit. Suppose that the carrier frequencies range in the interval 535-1605kHz. Find the range of tuning in the local oscillator so that the signal is translated to a frequency band centered at the intermediate frequency 455kHz.
Problem 2. Audio signals, bandlimited to 16kHz, are sampled and time-division multiplexed using PAM. The PAM pulses are 1us, and the multiplexing signal also provides an additional synchronizing pulse of sufficient amplitude and of the same 1us duration. If the signals are sampled at 40kHz, how many signals can be transmitted?
Problem 3. Show that an alternative asynchronous AM demodulation involves the following operations: – Modulation with sin and cos of the carrier frequency – Lowpass filter – Taking the Square – Adding up the signals and taking the square root.
Problem 4. Sketch the frequency domain representation of the intermediate signals involved in the Chopper Amplifier application