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I’m developing a TPMS transmitter, and we initially used a chip antenna. It performed well in field tests and even had a reasonable transmission through a metal container. However, when I installed it on a truck, the transmission became terrible.
After researching, I found that wire antennas are better suited for this type of application, so I’m testing a copper wire antenna, drilling through the A1 pad and adapting the PCB for it. During my research, I noticed that many circuits use a capacitor in series between the outer antenna end (which is usually left floating) and the ground plane.
My PCB:
My questions:
After researching, I found that wire antennas are better suited for this type of application, so I’m testing a copper wire antenna, drilling through the A1 pad and adapting the PCB for it. During my research, I noticed that many circuits use a capacitor in series between the outer antenna end (which is usually left floating) and the ground plane.
My PCB:
My questions:
- What is the technical name for this capacitor (pointed by the pink arrow)? Is there a specific designation for this component in this context?
- How do I correctly determine the capacitor value?
- Should I measure S11 with a NanoVNA and adjust based on the reactance jX?
- Are there general guidelines or typical values for 434 MHz?
- The RF trace includes a choke inductor (L1) and a DC-blocking capacitor (C3) near the MCU.
- The PI circuit for the MCU has already been calculated so that the Z1 pad is at 50Ω.
- I am not an RF engineer, but I have moderate knowledge of the subject.
- I own a NanoVNA, and I know how to match impedance and tune the antenna based on measurements, but any additional help is appreciated!
- The post image shows the latest version of the PCB I designed. If the wire antenna tests are successful, I will design a new PCB version to integrate it directly.
- I’m open to any other suggestions as well!
