[SOLVED] DDS vs PLL RF Link Budget

Hello all,

I am wondering whats the difference between DDS generated chirp and PLL generated chirp's phase noise characteristics in Radar Link budget analysis? It seems many papers reference DDS as a suitable option to PLL but I would have assumed digital signals having more phase noise due to clock jitter etc. when compared to a Colpitt Oscillator.

I am trying to do a RF Budget analysis to determine my receiver noise floor, DDS solutions are confusing me; in most cases a frequency multiplier is needed to get the carrier frequency up to C or X band (ISM) levels for proper operation; but should not that get away from using a Digital Generator principle?

Reference: Understanding Millimetre Wave FMCW Radars, Graham Brooker
Reference2 : Tx Leakage Cancellation of K-band Radar with Balanced Topology, Jeong-Geun Kim

Regards,

ktr

back in the day, people used analog ramp generators and a PLL-like tracking system to make a linear chirp. BUT it had serious linearity problems, and had a reset issue too.
SO although a DDS might have a little worse noise, making the chirp absolutely linear to within the bit look up table's accuracy is a big help for things like subclutter visability.