Abstract: A frequency modulation (FM) circuit, built in an electronic device, comprises an antenna circuit for signal receiving, an FM module connected with the antenna circuit for transforming FM signals of incoming signals into respective audio signals, and a controller connected with the FM module for forwarding the audio signals. The antenna circuit further includes an antenna, a low noise amplifier (LNA) and its matching circuit, a support structure, and a feed line. By providing the LNA and its matching circuit, the receiving sensitivity of the antenna circuit can be improved and the whole antenna circuit can be reduced to a size that is easily accommodated inside the electronic device. Also, an antenna circuit for the FM system circuit is provided as well.