The beauty of SMP connectors is that they are explicitly designed for board-to-board applications with substantial tolerance for misalignment. Each board has a male SMP connector, with a female-female "bullet" in between. These connectors, with the bullet in between, can tolerate substantial axial and radial misalignment (in excess of .010" - basically considerably larger than the fabrication tolerances of typical PCBs and PCB assembly) without degrading RF performance. Then one would have one multipin connector for power and digital signals that fixes the board-to-board alignment, and the SMP connectors can absorb the slack as necessary based on fabrication/assembly tolerances for their placement.
I agree that if we can get suitable performance out of an FMC or other single-connector solution, that would be better from a physical simplicity standpoint. We need to test this. I may try putting together a board to do so in the near term. > -----Original Message----- > From: Sébastien Bourdeauducq [mailto:s...@m-labs.hk] > Sent: Saturday, March 26, 2016 10:19 AM > To: Slichter, Daniel H. (Fed) <daniel.slich...@nist.gov> > Cc: Grzegorz Kasprowicz <gkasp...@elka.pw.edu.pl>; artiq@lists.m-labs.hk > Subject: Re: [ARTIQ] FW: initial specification of the project > > On Saturday, 26 March 2016 4:06:17 PM HKT Slichter, Daniel H. (Fed) wrote: > > The cost savings from using FMC, which might amount to $50 per AMC, > > are not worth if the crosstalk will make the cards not useful for > > researchers. > > It's not only about cost of the connector - the RF daughter cards will often > need some digital signals (e.g. SPI) for control. FMC provides plenty of pins > for that. Mixing two different types of board-to-board connectors will cause > mechanical problems and I think we should not do that. If two types of > connectors are needed, one of them should use cables. > > Sébastien _______________________________________________ ARTIQ mailing list https://ssl.serverraum.org/lists/listinfo/artiq
