ESP32-C3 Board Antenna Questions

[medemi68]

Good Evening Everyone,

I'm a relative noob when it comes to electrical engineering and electronic design, so please bear with me. I'm trying to design a board (that i'm going to open source) based on the ESP32-C3 with a built in RFID Reader. I'm currently trying to figure out the antenna matching circuit (Pi Matching Circuit) and I have some values that I think will work but I want to confirm them with someone who knows how to design RF Circuits.

Here is the Antenna portion of the schematic:

Screenshot 2022-12-04 at 9.33.47 PM.png (49.94 KiB) Viewed 2587 times

The <ANTENNA> tag is coming from the LNA_IN port on the ESP32-C3. I read on the forums that the Source Resistance for the ESP32-C3 is 30-40 Ohms + 10 source reactance. The antenna I am using is a Johanson Dielectrics 2450AT18A100E and it has a Load resistance of 50 ohms.

Will the capacitor and inductor values in the pi matching circuit work? I also ran this through a Smith Chart with the components' expected tolerances and got a chart looking like this:

Screenshot 2022-12-04 at 9.35.43 PM.png (960.66 KiB) Viewed 2587 times

I am well aware of the considerations needed when designing the PCB. I know that the ground plane can't be anywhere close to the antenna (at least 4mm), and that the pi matching circuit should be as close to the LNA_IN pin as possible, in a zig zag shape. I also know that I should probably put a bunch of vias connecting both ground planes, especially close to the antenna and the pi matching circuit.

Is there anything i'm missing here? Will this work?

Miguel

[ESP_Sprite]

Note that normally, you'd use the values you calculated as initial approaches, but you'd need to use a VNA on actual prototypes to get to actual usable values, as you also have parasitic capacitance which are dependent on e.g. the PCB substrate material and as such can't really be accurately modeled.

[medemi68]

Thanks for the advice. I was just wondering if I'm doing this correctly so far. Or if I'm missing something other than taking into account the parasitic capacitance. I know someone who has access to a lab so I will definitely see if they have a VNA and try and use one after I build my first prototype.

[ESP_Sprite]

I'll be the first to admit I'm not a RF expert, but it all looks sane to me.