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DC1048A - LT5575

Question asked by parado on Aug 10, 2018
Latest reply on Aug 14, 2018 by parado

Hello!!! I have a evalutation board of demodulator LT5575 at hand. I saw a strange problem with this board: when I use this, with the same frequency for LO and RF input (using a directional coupler like in figure) the amplitude of I and Q is incorrect, as if there were a same value add for each output I and Q indeed the phase is correct (arctg(Q/I)) but the amplitude is not correct ....

Instead, if the LO frequency is a littel bit different to RF frequency the board works how the range from datasheet....

It's strange because in the datasheet it is written that I and Q can also be in DC (Frf-Flo=0Hz)


Thank you.