Re: Best way to design a sine wave generator with 3 sync out
Heres my two cents:
Hmm, I'm no professional at this, but you really do need some form of low pass filter after the DAC, since the output spectrum will have a big spike at the sampling freuency (50Mhz). The phase problem is down to the design of your filter. You want a filter that has a fixed phase response.
Am I right in saying this is the sort of system you want?:
Microcontroller/PC -> DSP -> DAC -> LPF -> 3 different amplfiers with different gains.
Looking at your problem again, what 'exactly' are you trying to do? I mean, if you just want a sine-wave generator, why not go analogue? That way, you could produce 3 very good sinewaves, with a couple of potentiometers to change the frequency (you could using digital pots if you want to control it with a micro controller). And for getting exactly the right frequency, you could use a frequency counter on its output. That way, the oscillator creating the sine waves doesn't have to be accurate (it does have to be stable though), the frequency counter tells you the EXACT frequency of the wave, so you can vary its frequency be hand until you get the right frequency. Or just run the freqncy counter back into a micro controller and let that controll the frequency using 2nd order feedback.
A link here generates a really good sine wave, but its limited to low frequency (<20Khz), but its gives you some ideas:
https://www.edn.com/archives/1997/061997/13di_01.htm
One I've used:
**broken link removed**
If you're going digital (ie: DAC) then you want to have more than 16 samples per period, ideally over 32. You said you were using 50Mhz to achieve a 10Mhz output, but this means that each sinewave period would have 5 samples. This just ain't enough if you want a decent sine wave. Also, the bigger the difference between the sample period (update time of the DAC) and you frequency output the easier it will be to design a filter after the DAC.
Sorry, I'm rambling, but I just spurt out ideas sometimes
Heres how I would do it:
Microcontroller -> PLL chip -> FIR filter (converts square to sine) -> DAC -> LPF -> 3 separate amplifiers with individual gain controls but with same phase response.
Well, hope this helps in some way. As I said, it really depends on how 'clean' you want the sine wave, how complex you can build the circuit, and how much control you want over the 3 outputs.
Buried(in)Code.