# Carrier signal

Discussion in 'Wireless & RF Design' started by cpleng7, Sep 13, 2009.

1. ### cpleng7 Thread Starter Active Member

Dec 18, 2008
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Normally what we know after the AM wave to be demodulate the output is the information signal.

So did anyone know how to demodulate out the carrier signal from the AM wave?

2. ### mik3 Senior Member

Feb 4, 2008
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Multiply the modulated signal by another signal with the same frequency as the carrier signal. Best results are achieved if the other signal is in phase with the carrier signal.

3. ### t_n_k AAC Fanatic!

Mar 6, 2009
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Is that the same thing as "Double Sideband Suppressed Carrier"?

4. ### cpleng7 Thread Starter Active Member

Dec 18, 2008
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what i need to do now is using the disadvantage of the AM circuit apply in another circuit. can someone help me?

i have found out that the AM circuit have two disadvantages which is
(i) wasting power carrier
(ii) wasting bandwidth

what I am thinking now is using the wasting power carrier to make advantage to another circuit. the problem is I don't know how to extract the power carrier of the AM circuit. Can someone tell me how to do?

Apr 5, 2008
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2,299
Hello,

The power distribution is as followed:
The carrier has minimum 50 % of the power.
The two sidebands together the other 50 %.

http://www.educypedia.be/electronics/modulation.htm

Greetings,
Bertus

6. ### t_n_k AAC Fanatic!

Mar 6, 2009
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Do you mean you want to take advantage of the energy normally transmitted in an AM system by using another modulation technique? Or do you want to somehow extract the energy from an AM transmission and make use of it elsewhere? Presumably you mean on the transmitter side?

In reality you wouldn't be supplying this energy at the transmitter if you opted (say) for a single sideband (SSB) transmission method. So it's impractical to think about creating an AM transmit level signal and then trying to recover the energy. In the SSB case you would first generate the low level modulated signal and then feed this to the final (output) linear RF amplifier stage - the carrier component would be removed from the total information signal band before it reaches the high power RF amplification level and its subsequent feed to the transmitting antenna. No doubt your RF power amplifier will consume less energy as it does not need to send the unwanted energy in the carrier.

Keep in mind you have to use different demodulation techniques (at the receiver) to those that apply to AM transmission.