how to decide which modulator is use for am

[Parth86]

hello

there are three types of am modulation
ssb sc modulations
dsb sc modulations
vsb modulations

now i want to know what kind of modulator is use for these modulations

thanks

 

[davenn]

What is your specific need.... What are you trying to achieve??

Well there are more than the 3 you named. Each of those modes have their purpose

SSB .... Great for weak signal use and cuz of its narrow bandwidth .... ~2.5 kHz doesn't take up a lot of spectrum ... Used lots by amateur radio services, military and other commercial services
DSB .... Not sure who uses that these days
VSB .... Used for standard analog TV transmission .... Also dying out with the switch to digital services

Standard AM is still used by a few services like aviation ... Control tower to aircraft in the ~118 to 128 MHz


So again .... What are you wanting to achive ?

Dave

 

[WTP Pepper]

A diode is the simplest AM demodulator as it strips off the negative part of the signal and a simple filter removes the carrier.

However better performance can be achieved using a synchronous demodulator. Amplify the original signal so you end up with a square wave at the carrier frequency. If you have drop outs because of high levels of modulation then you can use a phase locked loop to maintain the carrier signal in the short term.

You then take this square wave signal derived from the carrier and 'sample' the original signal with it and filter. A mixer can achieve this as it is effectively multiplying the carrier (0 or 1) by the incoming signal.

At low intermediate frequencies <1MHz, a CD4016 analog switch is very effective in sampling if you bias the input to mid rail.

 

[Parth86]

thanks dave and wtp pepper
in transmitter circuit i need modulator but i don't know what kind of modulator is use for am transmitter
please tell me which modulator and oscillator is use for low level am transmitter

 

[davenn]

A diode is the simplest AM demodulator as it strips off the negative part of the signal and a simple filter removes the carrier.

However better performance can be achieved using a synchronous demodulator. Amplify the original signal so you end up with a square wave at the carrier frequency. If you have drop outs because of high levels of modulation then you can use a phase locked loop to maintain the carrier signal in the short term.

You then take this square wave signal derived from the carrier and 'sample' the original signal with it and filter. A mixer can achieve this as it is effectively multiplying the carrier (0 or 1) by the incoming signal.

At low intermediate frequencies <1MHz, a CD4016 analog switch is very effective in sampling if you bias the input to mid rail.

He needs a modulator not a demodulator

D

 

[davenn]

thanks dave and wtp pepper
in transmitter circuit i need modulator but i don't know what kind of modulator is use for am transmitter
please tell me which modulator and oscillator is use for low level am transmitter

Have you done a google search yet ??
There are dozens of hits for AM modulator circuits

Dave

 

[Parth86]

hi dave
i tried google but i could not find exactly what kind of modulator is exactly use for dsb,ssc and vsb modulations
i want to design low level transmitter
which modulations technique is use for low level
i think dsb sc i am not sure