Help needed with impendence of PCB trace

Thread Starter

netfoxuser

Joined Feb 6, 2024
3
Hello Forum,

I'm reaching out for the first time here, hoping to gain some insight. I've designed a PCB featuring an ESP32-S3-MINI-1U-N8 with an ipex connector. My goal is to connect this to a 50 Ohm SMA connector on the same board. To bridge these components, I'm using a 3cm ipex-to-ipex cable from the ESP32's ipex to another ipex connector soldered onto the PCB, which then has a trace leading to the SMA connector.

Although my initial prototype worked, I observed inconsistent signal quality across different units. This makes me wonder if the trace from the PCB-mounted ipex to the SMA might be the problem. The trace is 0.8 mm wide and 5mm long, surrounded by a ground plane.

Screenshot 2024-02-06 at 16.40.51.png
I'd appreciate any advice on whether this setup is a good idea anyway and if there are any improvements I could make, especially considering the importance of impedance matching in antenna design.
 

drjohsmith

Joined Dec 13, 2021
852
How do the grounds connect
What frequency you looking at
What is the ground plane and stack up
What have you calculated the track impedance to be , if in doubt use one of the many on line calculators,
 

Thread Starter

netfoxuser

Joined Feb 6, 2024
3
Hi, thanks for your response. Both the SMA and IPEX connectors' grounds are linked to the device's battery ground, with a surrounding copper area serving as Ground, hence the absence of visible traces. The frequency in use is 2.4GHz for Bluetooth. I tried using an impedance calculator but feel I lack some fundamental understanding, especially regarding "Isolation height," which the calculator at https://www.pcbway.com/pcb_prototype/impedance_calculator.html asked for.
 

drjohsmith

Joined Dec 13, 2021
852
Hi, thanks for your response. Both the SMA and IPEX connectors' grounds are linked to the device's battery ground, with a surrounding copper area serving as Ground, hence the absence of visible traces. The frequency in use is 2.4GHz for Bluetooth. I tried using an impedance calculator but feel I lack some fundamental understanding, especially regarding "Isolation height," which the calculator at https://www.pcbway.com/pcb_prototype/impedance_calculator.html asked for.
What are yiu not understanding in the calculator ?
Are these strip line designs then ?
Why are the gnd pads not joined to anything in the picture ?
 

Thread Starter

netfoxuser

Joined Feb 6, 2024
3
I'd like to take a step back and ask for assistance in optimizing the trace for signal integrity in my EasyPCB project, ideally for a 2-layer FR-4 PCB. The volume of information is overwhelming for what seems to be a one-off task. I'm open to discussing some form of compensation for the help.
 

Janis59

Joined Aug 21, 2017
1,855
Practical observation. Even with best available impedance calculation there is one variable having no any strict reglamenting. That is PCB dielectric constant. Thus, calculate a bit but not spend for that too much a time, then etch the pcb that part, measure it with VNA and make a corrections according to VNA results. Only so You may design the nice impedance matching.
 
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