Bluetooth Handsfree and Inverted F antenna
I bought a new hands-free from an online shop. Unfortunately, when I tried my first call with this device I found that the microphone is not working. I was thinking about returning the product but at the end I decided to try to fix that. As you can see in the following picture, the repair was straightforward. When I was fixing the polarity of the electret microphone, I found more interesting thing on the PCB - the invertered F antenna for bluetooth band (2.4 GHz) which is widely used in mobile devices. This particular antenna is connected to the source via coplanar waveguide with ground.