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johny_n5 22nd November 2009 02:06 PM

AM modulation transmitter and receiver

I want to design "AM modulation transmitter and receiver"

All the system (transmitter and receiver equipments) will be supplied by a symmetrical 12-V power supply voltage.

Block Diagram of the Transmitter Equipment to Be Designed

1.1 - An audio amplifier. This circuit amplifies the audio or voice signal provided by a microphone or CD player.

1.2 - A low-pass filter. It must limit (cut-off) the band of the signal provided by the microphone (information signal) to 4.5 kHz. It has to be a filter with a Butterworth approximation and following specifications:

Maximum band-pass frequency (fP): 4.5 kHz.
Minimum band-stop frequency (fA): 13.5 kHz.
Minimum band-stop attenuation (Amin): 40 dB.

1.3 - A carrier generator. It has to generate the sinusoid waveform carrier with a 10-V amplitude and a frequency comprised between 80 kHz and 100 kHz.

1.4 - A DSB-LC AM modulator. It has to take the 4.5-kHz band modulating signal (audio information) and modulate the sinusoidal carrier (There are different kinds of AM modulations. However, in this case, the design has to consider a DSBLC (double side band with large carrier) AM modulation.).

1.5 - A line amplifier. This circuit amplifies the modulated signal provided by the AM modulator in order to send it by the transmission line(In this case, the transmission line will be a simple copper wire.).

Block Diagram of the Receiver Equipment to Be Designed.

2.1 - A DSB-LC AM demodulator. It has to take the modulated signal from de
transmission line and has to recover the original modulating information signal(In this case, a simple diode demodulator is not allowed. You have to use a synchronous or coherent demodulator.) (If you need the sinusoid waveform carrier in the receiver equipment, you can use the same carrier signal that is provided in the transmitter equipment.).

2.2 - An audio preamplifier. Together with the volume control potentiometer, this circuit will adjust the level of the audio or voice signal.

2.3 - A power amplifier. This circuit amplifies the power of the demodulated audio signal provided by the audio preamplifier and has to apply it to an 8-Ω loudspeaker. Notice that this loudspeaker is a low impedance load for the power amplifier. The minimum value of the output power has to be 3 W.

Can I help design it?

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