Pulsive noise removing apparatus for an FM receiver

An apparatus for removing noise in a composite signal including an information signal and a reference signal of a predetermined frequency, said apparatus comprising:

• means for providing said composite signal,
• means responsive to said composite signal providing means for detecting a noise signal included in said composite signal,
• means responsive to said noise detecting means for providing an enabling signal of a predetermined time period upon occurence of said noise signal,
• gate means responsive to said composite signal providing means and said enabling signal providing means for being opened when said enabling signal is provided from said enabling signal providing means for interrupting transmission of said composite signal and for being closed when said enabling signal is not provided from said enabling signal providing means for allowing transmission of said composite signal,
• amplifying means coupled to the output of said gate means for selectively amplifying a signal component of a frequency commensurate with said predetermined frequency of said reference signal,
• attenuating means coupled to the output of said amplifying means for attenuating the output from said amplifying means, and
• storing means coupled to the output of said gate means and cooperative with said attenuating means for holding, when said gate means is opened, the signal level at the output of said gate means substantially to the value immediately before said gate means is opened,
• said amplifying means, said attenuating means and said storing means constituting a closed loop, said closed loop forming a positive feedback circuit with respect to said reference signal frequency which serves as an oscillator of said reference signal frequency when said gate means is opened, thereby to provide a pseudo reference signal of said predetermined frequency.