Chris Hamilton
This is our main communication Flex Module. Bluetooth BLE will be the primary way to interact with all Flex Modules.
These boards are alpha quality, they will likely not work yet. The design is in DipTrace. The design will require some tuning. This module is an nRF51822 with balun and chip antenna. I wanted to work with normal board thicknesses instead of more common module designs around a PCB trace antenna which requires a much thinner board. I am testing with 1db, 2db, and 3dB chip antennas in a variety of layouts.
Programming is supported through SWD utilizing the 6-Pin Tag-Connect TC2030-IDC.
Design Notes:
Ground Stitching
2.45Ghz frequency has a wavelength of 12.08cm.
Recommended ground stitching distance is wavelength/20 or 6.04mm
Antenna Feedline
Johanson Technology recommends a coplanar waveguide
(Calculated using TXLine and OSHPark board specs):
4layer: dielectric constant 3.665, loss tang 0.012, copper, ~51ohm, 2.45ghz, height 6.7mil, thickness 1.4mil, gap 6mil = 11.2756mil
2layer: dielectric constant 4.6, loss tang 0.016, ~51Ohm, 2.45ghz, height 1.6mm, thickness 1,4mil, gap 6mil = 29.0102mil
The solder mask will lower the impedance slightly, so instead of 50Ohm, I calculated with 51Ohm.
I original attempted a microstrip design, but the width was around 110mil for 2 layer boards. Surrounding the trace with ground plane is much more sensible. The distance to the Antenna pad from the trace line is copied from the reference design. The balun should do most of the matching. I would recommend adding a microstrip for tuning, but until I have a chance to test with a Network Analyzer, it is pointless.
Any software related will be released under BSD or MIT license. SAAS or cloud based software will be AGPL.
Kris Winer
