On Thu, Aug 17, 2023, 3:21 PM Pawe? H <pawel@...> wrote:
John,
I would say that conversion from MHz range to tens of kHz range makes no difference to having 0 IF.? For me the important is that the circuit have correct impedance for the particular band frequency. We are calculating all of these filters for 50 Ohms in and out, right?
The matching resistors are these 100 Ohms. There is always connected two to the signal path, so in parallel it gives 50. Zero resistors are another option for the matching, but for some unknown to me reasons the designer choose another option and left them just in case. I assume 1nF caps also take part in some kind of filtering. I also saw the solutions with single series 33 Ohm resistor directly in front of the mixer splitter transformer.
