Review my schematic

RE: Review my schematic

Newbie — Sun, 19 Mar 2017 05:28:47 GMT

Please review my updated schematic in case number 35225. Thanks

RE: Review my schematic

Newbie — Sat, 18 Mar 2017 04:22:40 GMT

Hello Jay, Thanks for your answer and suggestions. I have made changes in the schematic and have uploaded new schematic in case number 35225. Please let me know if it us good to go. Thanks Shailav

RE: Review my schematic

Jay Tyzzer — Fri, 17 Mar 2017 22:19:05 GMT

Greetings. Changing the antenna will not constitute a change in the radio impedance / harmonic network consisting of the 7 passive components as that is the 50 ohm feed point. However changing the antenna shape, size, type, etc may (will) constitute a change in the Antenna matching network as described in my previous post and shows in the prior PI network diagram.

RE: Review my schematic

Jørn — Thu, 16 Mar 2017 08:08:27 GMT

I have withdrawn my answer as Jay has pointed out several things I was currently unaware of. One note though, Nordics reference schematic is designed for a PCB trace monopole with 50 ohm input impedance. If a different antenna is used, the matching network will need to be changed.

RE: Review my schematic

Jay Tyzzer — Wed, 15 Mar 2017 16:59:32 GMT

Hello,

There are a few items that are incorrect in the schematic that will cause this design not to transmit or receive very far. Also harmonic content is also questionable.

The Nordic reference schematic has not been followed as it relates to the output matching / harmonic filter. This needs to be changed. I suggest just copying the standard design. It works.. Also copy the layout as shown in the datasheet. This design has been tested against the FCC and ETSI guide lines. You can use either the design files that are shown in the datasheet or you can use the Development Kit design files. (nRF51-DK)
Included in the matching network is a line called VDD_PA. This is currently floating in the submitted design. This VDD_PA line that goes "High" to 1.8vdc 50us before the radio transmits and stays high until the radio stops transmitting. It supplies power to the internal PA of the device. Without this there will be no appreciable output power.
In addition to the 7 components needed in the matching network, an additional PI network is needed near the antenna for proper tuning. Usually not all three are used and that is determined at time of antenna tuning.

Johanson makes a balun for the nRF51 in the QFN package. It is a single device that replaces 6 of the 7 components in the matching network. The single price is a bit more then the 6 components it replaces but maybe a good choice for this design?
The part number is 2450BM14E0003
www.johansontechnology.com/.../JTI_AN030.pdf

NOTE: The antenna matching PI network is still required.

The rest of the radio circuit looks ok. Be sure that the CL values of the crystals are 8pf for the 16mhz and 9pf for the 32Khz. If the CL values are changed then the load cap values will need to be recalculated as well.

If you like you can repost your reworked design here in the open forum or you can use our secure support portal located under the MYPAGE section in the upper right side of the Nordic Semiconductor web site. Only Nordic Employees can see those posts.

Good luck with the design..

Best regards,

Jay Tyzzer