Hi Jared,
Firstly, thanks for all your great work and generosity in sharing all of your hard work with the greater community.
I have a couple of questions regarding the LTE antenna and associated matching circuit on the nRF9160 Feather that I hope you can help me with.
Reading through your original Feather build blog, I noted a section where you highlighted that the RF circuitry design for the feather was “not straight forward” and you included a reference to the Nordic Thingy91 RF schematic. In that circuit Nordic used a switched multiplexing arrangement to cater for all the supported operating bands. You mentioned that you forwent this design arrangement due to space limitations on the Feather.
Given this, what specific LTE Band was the PY matching circuit components selected for on the Feather? As I can’t see how the capacitor and inductor values selected compare against those shown on the Thingy91 circuit (In particular for Band28 which I am specifically interested in).
My IoT application sees the Feather installed in an unfavorable LTE comms location (low to the ground or in cable pits), and with the supplied Unictron WC12H0 antenna I’m ending up with a weak signal with RSRP around -112dBm just testing indoors in my office. However, I happened to noticed that the nRF9160DK on its internal antenna (ethertronics PB22601) connects with a stronger signal that is on average around 20dB better connecting with an RSRP of around -92dBm.
I am now trying to work out what I may be able to do improve my connection strength. I’ve tried a few different antennas that had different gain values and radiation patterns. I’ve tried to select ones with higher gains shown on the datasheet for the 700Mhz band (B28) that I am interested in. But so far, I have been unable to close the signal strength gap in comparison to the DK. I’m by no means an antenna expert, and am now reaching for straws and looking for circuit differences that may be the cause of my observation, and that lead me to the matching circuit and the questions above.
Thanks for any time and guidance and help you can provide on the above.