On 18/09/2023 06:11, Marcus Müller wrote:
Hi Oğuzhan,
we of course haven't run any matching tests on what happens in that
bypass mode; it would still seem to me that if you bypass U805, you'd
want to remove the in- and output capacitors, indeed. I'd strongly
advise against doing this modification, for the following technical
reason:
24 to 27 dB isolation is indeed what the datasheet of the
SKY13335-381LF says, but don't forget that you have another 24 to 27
dB of isolation between TX and RX in U807, adding up to 48 to 54 dB of
isolation. That's in the same ballpark as crosstalk through the board,
power supply, adjacent traces etc. The B2xx was designed by RF
engineers who kind of knew what they were doing :D
So, don't expect to win much by removing U805. Especially paired with
the fact that we have no characterization of matching in the bypassed
mode, I'd assume you really won't end with a cleaner RX, but just more
problems
Best,
Marcus
On 18.09.23 08:11, ouzan...@hotmail.com wrote:
Hello, in my case, the function performed by the "SKY13335−381LF" IC
switch is not working for me. And as far as I can see, the isolation
of this component is low (24dB-27dB). The card I have is B200.
Schematic B210 given in the link
"https://files.ettus.com/schematics/b200/b210.pdf";. I want to bypass
this component. As far as I can see, there are pads for this on the
card. I think it is bypassed by activating C847 and C849 in the
relevant part of the B210 schematic that I sent you in attachment.
The main question I want to ask is, should I connect the 220pF
capacity seen in C810 to C847, and the 470pF capacity seen in C814 to
C849? Or should I short circuit directly?
I am aware of all the risks. I'll be happy if you can help me. Have a
nice day.
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I think I'm missing some context here. What is the goal?
IF the goal is really really high TX/RX isolation, you're not going to
achieve that with this design. Since the TX and RX signals
go through the AD9361 RF chip, which is tiny, very high isolation
will never be achieved.
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