DDS Design

if i need to design DDS with output clock of 200MHz, is DDS with 300MSPS enough to produce this? or I need a DDS with 400MSPS?

what chip do i need from ANALOG?

Is there any manufacacturer of DDS?

β:D

you can click here :
http://www.analog.com/en/subCat/0,28...0%255F,00.html

i already read most of the data sheets of DDS from analog.

Just want to know some opinions which DDS is much applicable for 200MHZ operation..


β

Nyquist says you need more than 2 X 200, so maybe 450 MHz clock. That way you will get in-specification performance, and the electrons will be happy.

I some applications, especially if you do not care too much about spurious performance, you can deliberately underclock a DDS. For example, if you had a 300 MHz clock and programmed the DDS for 100 MHz output, you would also get an aliased 200 MHz output. You would have to bandpass filter it to use it, and it would be lower in amplitude than the specified output, but you might get by. Need to empirically test it, and you might get some variation in performance from lot to lot.

hi,

i already used the AD9954 from Analog devices and tested up to 180 MHz (clock speed 400 MSPS). It works without any problems. as far as i can remember, they also have DDS components even with higher clock frequencies, so please look at the website.

Output clock? A DDS has an input clock and an output sinewave. Please clarify.

You program the output sinewave to be less than one half of the input clock. How much less depends mostly on your external low-pass filter.

to be specific, this are my design requirements:

A clock source (square wave) that has an output frequncy of 0 to 200MHz with a resolution of 1KHz.

im now considering using a DDS from analog having a master clock frequency of 1GHz.

the problem was that i cant find as of now, a clock source for this device, unlike other chip that has internal frequency multiplier.

AD9858 has no internal frequency multiplier. im still searching how can i create this reference clock. (1GHz)

still learning about DDS...

any suggestion?

:D β

You can buy 1GHz oscillators. A couple examples:
http://www.rfx.co.uk/
http://www.foxonline.com/rfxoseries2.htm

Maybe find more here:
http://www.rfcafe.com/vendors/compon...ator_links.htm