Hi All
I came back again , as i promised .
Thanks for reading my blogs.
Well , the PWM ( pulse width modulation ) consist from DC component ( DC as message ) and High frequency components .
And SPWM ( sinusoidal pulse width modulation ) consist from message signal and high frequency sidebands .
According to the Shannon-Hartley Law , the frequency of message signal should be about 2Fm that Fm is message signal ( e.g your voice )( remember that each non sine wave is contain from many or some sine waves e.g square wave )
But in practice the frequency of carrier should be about more than 10Fm . so what is the carrier wave ?
It is simple . it can be a sawtooth wave or a triangle wave . but there is a different between triangle and sawtooth :triangle can be used for SMPS or Audio amps , but sawtooth can't be used for audio amps ( it destroy the message signal , and i will demonstrate it with some simple equations )
Note :for SMPS , we'd better to use 2 level signal as carrier ( between zero and +v ).
Note : if the frequency of carrier be very higher than 10 Fm the precision will increase . you'll ask the precision of what ?!
As we know , we want detect the voice or message signal from that PWM or SPWM , and if the frequency of sampling (carrier become higher , the samples will be more , and thus the precision can be higher ( don't worry i'll demonstrate it with mathematical equations ) .
Try to think about things that i said .
I'll come back with the real spectrum of SPWM and PWM signal ( it is like mountains ! and very beautiful !!!!)
Best Wishes until i come back ! :-D
Goldsmith
I came back again , as i promised .
Thanks for reading my blogs.
Well , the PWM ( pulse width modulation ) consist from DC component ( DC as message ) and High frequency components .
And SPWM ( sinusoidal pulse width modulation ) consist from message signal and high frequency sidebands .
According to the Shannon-Hartley Law , the frequency of message signal should be about 2Fm that Fm is message signal ( e.g your voice )( remember that each non sine wave is contain from many or some sine waves e.g square wave )
But in practice the frequency of carrier should be about more than 10Fm . so what is the carrier wave ?
It is simple . it can be a sawtooth wave or a triangle wave . but there is a different between triangle and sawtooth :triangle can be used for SMPS or Audio amps , but sawtooth can't be used for audio amps ( it destroy the message signal , and i will demonstrate it with some simple equations )
Note :for SMPS , we'd better to use 2 level signal as carrier ( between zero and +v ).
Note : if the frequency of carrier be very higher than 10 Fm the precision will increase . you'll ask the precision of what ?!
As we know , we want detect the voice or message signal from that PWM or SPWM , and if the frequency of sampling (carrier become higher , the samples will be more , and thus the precision can be higher ( don't worry i'll demonstrate it with mathematical equations ) .
Try to think about things that i said .
I'll come back with the real spectrum of SPWM and PWM signal ( it is like mountains ! and very beautiful !!!!)
Best Wishes until i come back ! :-D
Goldsmith