Dual-Channel Sine-cosine generator

[Jdo300]

Hello All,

I am doing some random experiments where I want to generate a very fast rotating magnetic field using two out of phase sine waves (90 degrees separated). I wanted to ask you all here if you have ever seen any kits for a dual sine wave generator that allows the user to adjust the phase shift. I know that I could build something using Op-amps but I'm really looking for an off the shelf solution (a kit or something) that I can put together. If anyone is curious, the frequency range I'm aiming for is 1Hz to 1Mhz roughly. So far I found a nice DDS board on eBay that would do exactly what I want if it had two channels:

http://cgi.ebay.ca/N3ZI-80-MHz-30MHz-DDS-Direct-Digital-Synthesizer_W0QQitemZ130306100829QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item1e56d94e5d&_trksid=p3286.c0.m14&_trkparms=72%3A1215|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

but so far I haven't found anything else. Any tips would be crealy appreciated.

Thanks,
Jason O

 

[vk6kro]

I don't know of any ready made units, but I can suggest one approach.

If you get two 8 bit eproms and program them for 8 bit sinewaves out, but calculated to be 90 degrees out of phase with each other, you could produce the sinewaves from ladder networks or D to A converters. You would have to clock them together at 256 times the output frequency, so clocking at 10 MHz would give an output frequency of about 39 KHz.

This frequency could be higher if you could accept a rougher sinewave by taking bigger steps than 1 degree.

I have an Excel file that does this if you want to go that way. The graphs in Excel look like very acceptable sinewaves.

If you used a large enough EPROM, you could program it to give smaller steps in phase by storing alternative sets of data.

 

[Jdo300]

Hi vk6kro,

That's an interesting approach, I have thought about that myself, but honestly, if I end up making something like that, I'd probably use DDS ICs controlled by a microcontroller. I know that Analog Devices makes some nice ones that would probably work fine. I was just hoping to find an off the shelf solution before looking into developing such a thing myself.

Thanks,
Jason O