In the High Frequency and RF(Radio Frequency) circuit, PCB traces basically start to act as antennas;

You know, in order to reduce volume and improve the stability of the system in the above circuit, the designer tends to adopt a certain special way, such as routing with unique design which is used as antenna.

After all,the frequency of this circuit is quite high and the size of antenna is not too huge so that the antenna can be realized via PCB traces. Furthermore, PCB traces are made at the time of PCB fabrication, then which is also called printed antennas.