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Broadband dual sine wave synthesis in a 625 square mm area

Question asked by EA4FRB on Jan 20, 2011
Latest reply on Jan 21, 2011 by JLKeip

My design requires the generation of two programmable sine wave signals in the range of about 1Mhz to 200Mhz (or wider). The frequency difference between the two sine waves shall be around 1Khz. Regarding the the frequency step size the smaller is the better, but it is acceptable having 1 or 10Khz steps (I would said that it is not necessary having 1Hz or sub Hertz step size as in common DDS based solutions). There are no special requirements about phase noise.


The critical requirement is the board space size. The synthesizer has to fit in a 625 square mm area and around 2-3mm maximum height, which is about the footprint of the AD9958 and glue components.


My primary choice is the AD9958 DDS which fits very well to these requirements (notice that the reconstrucion filter is outside the 626 sq mm area). However this component is somehow expensive and I'm wondering if cheaper alternative design options exist. I was looking to several design options based on PLL synthetisers but in order to achieve the near DC range it is necessary downconvert the high-frequency VCO signal and any of the solutions I found so far exceed the expected board size and they are rather complex. In the other hand I found complete PLL based synthesizers but only for square waves.


Do you think if there is a practical alternative? I'll appreciate any hint or suggestion to progress on the investigation of a solution.