Hey guys, I am doing this envelope detector to demodulate the modulating signal.

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/RadCom/part9/page2.html

Can anyone briefly tell me the function of each components there ?

Really appreciate your help.

Thanks !

 

The germanium diode half wave rectifies the incoming signal, and the capacitor/resistor filter out the rf and smooth out the recovered signal.

 

The germanium diode half wave rectifies the incoming signal, and the capacitor/resistor filter out the rf and smooth out the recovered signal.

Ay detail explanation about all these ?

Thanks !

 

The AM modulation produces an RF waveform that varies in amplitude in response to the amplitude. The diode rectifies the RF to produce a half-wave of the RF which has an average value equal to the modulation signal. The RC filter removes the RF, leaving the signal that originally modulated the radio wave.

 

Hey guys, normally what will the questions been asked for the modulating and demoudlting circuit ?

I am so confused now..LOL

 

So this is homework for a quiz?

 

Nope.. This is like a presentation I need some help in this

Appreciate your help

Thanks !

 

Have you read the Wikipedia entries on AM modulation?

 

Have you read the Wikipedia entries on AM modulation?

Yes, so I wonder what would the instructor ask probably

 

Yes, so I wonder what would the instructor ask probably

Likely questions to determine if you understand the basic of AM modulation and demodulation. Do you?

 

Likely questions to determine if you understand the basic of AM modulation and demodulation. Do you?

Not really fully understand yet ..Sigh.

 

Not really fully understand yet ..Sigh.

If you have specific questions, perhaps we can help.

 

how the resistor and capacitor discharge and change ?

I am not really understand fully yet about functions of every components in envelope detector.

Thanks

 

If you don't understand the operation of resistors and capacitors then we are really starting at the beginning.

Try reading this and this.

 

If you don't understand the operation of resistors and capacitors then we are really starting at the beginning.

Try reading this and this.

HAHAHA, well, I know the basic function of both components. Just that I am not so sure how it works in this circuit . How/ when it discharge and charge ?

Thanks

 

Hello,

Have a look at page 5 and 6 of the following PDF:
http://educypedia.karadimov.info/library/tut331_04am_dem.pdf

Bertus

 

Wow, that pretty good pdf. Anyway, what does it means by distortion ? It might be asked by instructor. I may say the facts that if RC is not correct, distortion will occrus. But well how is it ?

Thanks

 

Hello,

Have a look at page 5 and 6 of the following PDF:
http://educypedia.karadimov.info/library/tut331_04am_dem.pdf

Bertus

Hey, based on the picture, what does it means by creating a baseband signal ?

I dont get it. I understand that baseband filter is a filter that will not filter a specific range of frequency.

Thanks

 

Hello,

Have a look at page 5 and 6 of the following PDF:
http://educypedia.karadimov.info/library/tut331_04am_dem.pdf

Bertus

Hey, what is the function of the LOW pass filter there actually ? Why we use a low pass filter there ?

Thanks

 

The function of a low pass filter is to pass low frequencies and attenuate frequencies above the filter's corner frequency.

In this case the LP filter is used to attenuate the RF frequency but pass the modulation frequency.

Note that a standard op amp will not work very well as a filter here because of the op amps limited frequency response. An active filter requires the op amp to have significant gain at the RF frequency and a standard op amp doesn't. Better to use just a passive RC LP filter.