On 7/27/22 5:25 PM, Donald S Brant Jr wrote:
At a glance I noticed the wide traces at the connector pins, which are excess capacitance. Unless there is a compelling reason to do otherwise I tend to select a dielectric material whose 50¦¸ width is slightly larger than the connector pins and component pads I plan on using. It is only necessary to use thin boards such as you are using for very high frequency (>20+GHz perhaps), work, to avoid resonances and radiation. 0.8mm board (or thicker) might be more appropriate.
As I recall, 50 ohms on 1 ounce copper on an 0.031" board with epsilon=2.5 as microstripline was 0.1" wide. There's countless calculators out there. If you pick the board correctly, a 4 pin SMA solders on very nicely. (the gap between corner pin and center pin is about 1 mm, which is close to 0.039")
I also like to pull the solder mask away from the RF traces ideally 2 line widths wide, again to avoid excess capacitance; solder mask has a higher dielectric constant than air. This excess capacitance is particularly problematic in the gaps between RF line and ground of your .
I like to chamfer the corners of the transmission lines and leave a small gap at the connector pin, again to avoid excess capacitance.
Finally, many board houses charge per hole drilled ("hits") and if so, you can drastically reduce the number of vias to a single line on each side of the RF line, with a cluster of vias, or better yet, wraparound grounds (could be copper foil added at assembly), for the connector grounds.
Best regards, Don Brant.
