D/A Questions: interpolation factor, components features

Some D/A Questions

Hi Everybody,

I'm quite new in D/A, so I will appreciate some helps with few things:

1. Can anyone explain me please what means the D/A interpolation factor and
what is the difference between that and the max MSPS?.

2. I need to design a D/A that can output 40MHz BW signal with maximum
frequency of 160MHz , that has been sampled with 160MSPS A/D.

What are the main features that I need to pay attention when choosing D/A
component? Does anyone know a D/A that fit to this job?


Thanks!

Re: Some D/A Questions

The output of a D/A converter isn't a clean signal (you can still see the voltage steps). It still contains a lot of harmonics. Normally the output signal is filtered by an interpolation filter (LowPass). The interpolation factor is the ratio of the D/A clock speed and the bandwidth of the interpolation filter. For a realistic filter design the interpolation factor has to be at least 3 and more, depending on the harmonic levels you can tolerate in the system. MSPS (Mega Samples per Second) the maximum clock speed of the convertor.

Depending on the filter design and the harmonic levels that are acceptable, you will need a DA convertor whose clockspeed is at least three times higher than the maximum frequency = 160 x 3 = 480 MSPS.

I didn't find a suitable D/A convertor at analog devices. You may consider outputting the baseband 40 MHz signal and mix it in an analog way to higher frequencies. This will relax the demands on your convertor.

The resolution (in bits) gives you the number of quantisation noise. Notice that the effective number of bits is often less than the actual resolution.