The design of the 8/16 elts filter mobo has been completed. Now, we can launch a proto and see if what’s on the paper will work as advertised.
I still have to finish the “BCD command board” (this one was not urgent and mandatory for Alex’s project) and a fully new switching board for the high power version of the filter.
Anyway, here is the full and final production of the different elements of the filter.
THE COMMAND BOARD :
This card decodes an I2C bandswitching command comming from Alex’s microcontroler, and sends the corresponding signal to one of the multiple input of an ULN2803 (relay driver)
Each I2C interface has a selectable adress, determined by a matrix of 2×3 0 Ohms pullup resistors.
Quite a lot of “invisible changes” have been made in the position of the traces, tuning of each component size and position and so on… Enough space has been preserved to solder a “U” shaped shielding located all over the central bus. This will probably enhance input/output isolation and minimize all RF re-injection risks.
The FILTER DAUGHTER CARD remains unchanged…
… excepted some angle stripline to try to keep the input impedance as close as possible to 50 ohm. But the angle connectors binding this daughter board to the mobo will certainly destroy the quality of the line. Anyhow, it’s not a reason to have “ugly traces”. I hope the next “filter” bloging wil have some real picture to illustrate the story.