The adaptive control die Hilbert converter null in the FM

摘要

PURPOSE:To reduce the distortion of amplitude without increasing the number of shift registers by detecting input frequency from an FM demodulation output and controlling a tap factor for an output signal corresponding to an orthogonal component in accordance with the detecting signal. CONSTITUTION:The Hilbert converter 2 has a digital filter and is constituted so that the 1st output signal is extracted from the center tap of a shift register in the filter, the 2nd signal is extracted by multiplying prescribed tap factors from respective taps of the shift register and the 2nd output signal is orthogonal to the 1st output signal. The input frequency is detected from the FM modulation output and the tap factor of the 2nd output signal is controlled in accordance with the detecting output. Namely, a tap factor adaptive control part 6 has a frequency detecting part 7, a delay circuit 8 and a tap factor generating part 9. Consequently, the distortion of amplitude is not generated at the time of modulating an FM modulation signal having a large frequency deviation.