Can I get antenna design for STEVAL-ALOCKCB PCB trace antenna?

[smithderek2000]

Hello,

   I'm updating an ST25R3916B project to use the ST25R300 due to the obsolescence of the Murata variable capacitor. This project is read/write of ISO15693 tags only, no card emulation or anything fancy. It uses one IC which is then multiplexed with relays to 20 different antennae, each about 2cm square. The tag that we're reading is about 2cm by 1cm, and has been working reliably. So for this update I start by finding all the reference designs, and I saw this little gem, the STEVAL-ALOCKCB. It looks like it has an antenna the same size - how do I get more information about it? Can you please post the dimensions, or even better just send me the Altium files and I can get it out of there cleanly. Reference designator on there is ANT700.

Also one question on that design - on PDF page 8 of the schematic it has the filter and antenna match but it looks like it's duplicated on both sides of the connector - why? Is that in case someone wants to use a different antenna at the connector? If I wasn't going through the connector, then which set of values would be best to use with this trace antenna?
https://www.st.com/resource/en/data_brief/steval-alockcb.pdf

Thanks
Derek

PS @Travis Palmer I saw the app note on multiplexing antennas and will try it out on a future board to compare with the relays.

[Travis Palmer]

Hello Smithderek,

I really appreciate your feedback regarding the multiplexer circuit and its application note. 

I will get in touch with the responsible of the STEVAL-ALOCKCB to answer your questions.

br Travis

[Travis Palmer]

Hello Smithderek,

below the answers to your question.

I will share the Gerber files with you via PM.

BR Travis

The NFC antenna on the STEVAL-ALOCKCB has been designed to provide maximum flexibility to the user. It can be:

1. used in its original configuration, as supplied on the board;
2. moved to a remote position with respect to the main board;
3. replaced by a different antenna, better suitable for the customer’s needs or application requirements.

To support cases 2 and 3, the schematic includes components that allow the antenna to be disconnected from the main board and, if needed, reconnected afterwards by using connectors or a cable for displacement.

To detach the antenna from the main board, it is necessary to:

• desolder resistors from R700 to R708;
• then, by applying a light mechanical force, the PCB breakaway tabs holding the antenna to the main board can be separated.

If you want to reconnect the antenna to the main board later on, you need to solder the following connectors:

• J600 on the main board;
• J700 on the antenna section.

The corresponding part numbers (PNs) are reported in the schematic.

About the question about PDF page 8. The antenna stage, I mean the passive components between the ST25R300 device and the NFC antenna, is made of two parts:

• the EMC filter, which is placed on the main board (L600, L601, C612, C613, C616, C617);
• the matching network, which is located on the detachable PCB section of the NFC antenna (capacitors from C700 to C711).

The capacitors C611 and C618 should only be populated if card emulation operation is required. For more details, please refer to application note AN6092.

This architecture was specifically designed to give users the flexibility to experiment with different antenna configurations. For example, the STEVAL-ALOCKCB can also be fitted with some of the antennas included in the STEVAL-25R200A kit. For more details, please refer to user manual UM3199.