Wilson_yu_chen
Advanced Member level 4
FM headset resonance
Hi All,
I use USB type FM headset with USB shield as antenna, and USB shield and PCB ground is connected by a big inductor (0.1uH or 1uH) to provide FM RF match.
Other than this inductor, I have match network outside the FM chip(Silabs).
I met a issue that poor FM wireless Sens by using a new headset where headset ground connect to a bead (EMI) before going to PCB ground. For the old headset with good performance, the bead is replaced by a 10pF cap and there is a bead putting on the serial path of shield of the headset to mobile phone.
Regarding the FM resonance, besides the the length of wireline and the PCB side matching facotors, could the passive components on headphone get resonance on FM band?? I doubt EMI bead with 1000ohm on 100MHz act as resistor and get resonance with capacitor/0.1uH.
Or if any tool to emulate the circuit resonance??
Thanks
Hi All,
I use USB type FM headset with USB shield as antenna, and USB shield and PCB ground is connected by a big inductor (0.1uH or 1uH) to provide FM RF match.
Other than this inductor, I have match network outside the FM chip(Silabs).
I met a issue that poor FM wireless Sens by using a new headset where headset ground connect to a bead (EMI) before going to PCB ground. For the old headset with good performance, the bead is replaced by a 10pF cap and there is a bead putting on the serial path of shield of the headset to mobile phone.
Regarding the FM resonance, besides the the length of wireline and the PCB side matching facotors, could the passive components on headphone get resonance on FM band?? I doubt EMI bead with 1000ohm on 100MHz act as resistor and get resonance with capacitor/0.1uH.
Or if any tool to emulate the circuit resonance??
Thanks