- #1
Jdo300
- 554
- 5
Hello All,
For those of you who haven been following my last two threads, I finally decided to go with the Microcontroller/DDS combination to make my three-channel sine wave generator (since I have yet to find one in existence at all that doesn't cost megabucks).
I have the microcontroller part worked out already (I'm working with the dsPIC30F2020 since I already have some code written for it from my pulse generator project). The DDS IC I plan to use is the AD9834. I have two of them in house tight now on surfboards and I just finished breadboarding up a basic test circuit to check that I A. didn't burn the IC up when I soldered it and B, can actually communicate with it.
I'll be doing that testing tomorrow but I an curious to know how to properly design the output reconstruction filter for the output waveform. I've done some searching around online to see what other people are doing and It seems like some kind of nth order elliptical filter type thing is a popular choice. However, I am very much filter illiterate (beyond the basic AC Circuits 101 High pass and Low pass filters).
I do at least know that in order to begin the design, I have to know what the maximum frequency and clock speed of the IC will be. At this time, I plan to use an input clock that has a frequency of 53.6870912 MHz. The oddball frequency was calculated so that I would have a frequency resolution of exactly 0.2Hz through the entire range. I plan to make the top frequency of the generator 10.737Mhz to keep the resolution from getting to bad. So I'm wondering what is the first steps to design a filter that can adequately smooth out the steps in the waveforms.
In case anyone is interested here's a link to the product page for more info on the DDS:
http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad9834/products/product.html
Any help/assistance/pointers would be greatly appreciated as I have no clue where to even start with this.
Thanks,
Jason O
For those of you who haven been following my last two threads, I finally decided to go with the Microcontroller/DDS combination to make my three-channel sine wave generator (since I have yet to find one in existence at all that doesn't cost megabucks).
I have the microcontroller part worked out already (I'm working with the dsPIC30F2020 since I already have some code written for it from my pulse generator project). The DDS IC I plan to use is the AD9834. I have two of them in house tight now on surfboards and I just finished breadboarding up a basic test circuit to check that I A. didn't burn the IC up when I soldered it and B, can actually communicate with it.
I'll be doing that testing tomorrow but I an curious to know how to properly design the output reconstruction filter for the output waveform. I've done some searching around online to see what other people are doing and It seems like some kind of nth order elliptical filter type thing is a popular choice. However, I am very much filter illiterate (beyond the basic AC Circuits 101 High pass and Low pass filters).
I do at least know that in order to begin the design, I have to know what the maximum frequency and clock speed of the IC will be. At this time, I plan to use an input clock that has a frequency of 53.6870912 MHz. The oddball frequency was calculated so that I would have a frequency resolution of exactly 0.2Hz through the entire range. I plan to make the top frequency of the generator 10.737Mhz to keep the resolution from getting to bad. So I'm wondering what is the first steps to design a filter that can adequately smooth out the steps in the waveforms.
In case anyone is interested here's a link to the product page for more info on the DDS:
http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad9834/products/product.html
Any help/assistance/pointers would be greatly appreciated as I have no clue where to even start with this.
Thanks,
Jason O