aaron_do
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Hi all,
I would like some opinions on which is better: voltage-mode or current-mode passive mixers. For voltage-mode passive mixers, the switching core is followed by a high impedance, while for a current-mode passive mixer, the switching core is followed by a low impedance. I will start with a few.
voltage mode ========= 1) Smaller devices means less driving strength needed by frequency synthesizers. 2) Higher gain before baseband amplification. Potentially less noisy? 3) Easily coupled with Gm-C type filtering for low noise, low power, and wide bandwidth.
current-mode -========= 1) Better linearity due to low voltage across the switches and the LNA. 2) Easier to get a well defined gain as the load impedance is easier to define at baseband. 3) Smaller resistance in series with the signal path. Potentially less noisy? 4) Easily coupled with op-amp based filtering for high linearity.
Overall, my opinion is that a current-mode passive mixer will get you a more robust system, however, I believe potentially the voltage-mode passive mixer has better NF. I have been assured by a very experienced designer that all real systems use current-mode passive mixing. What are your thoughts?
thanks, Aaron
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