The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 12, 2006
Filed:
Jul. 01, 2003
John F. Kennedy, Dearborn, MI (US);
Edmund J. Tillo, Belleville, MI (US);
John F. Kennedy, Dearborn, MI (US);
Edmund J. Tillo, Belleville, MI (US);
Visteon Global Technologies, Inc., Van Buren Township, MI (US);
Abstract
The present invention provides a system and a method to prevent undesired sounds during FM modulator turn on. The system includes an RF attenuator circuit, a delay switch circuit, an RF ramp up circuit, and audio ramp up circuit. The RF attenuator circuit significantly reduces the RF signal from the FM modulator when the FM modulator is initially turned on, which significantly reduce whistle caused by the RF signal from the modulator beating with the local oscillator in the radio receiver. After allowing time for the PLL to lock onto the RF signal, the time delay switch circuit becomes active and charges the RF ramp up circuit. The RF ramp up circuit gradually increases the RF signal by gradually deactivating the RF attenuator circuit. The gradual increase of the RF signal is slower than the response time of the radio AGC, thereby preventing any pop as the RF signal is provided to the radio receiver.