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:
Apr. 04, 2000
Filed:
Jul. 29, 1997
Roger L Paulsen, Glendale, AZ (US);
Colin Semwayo, Phoenix, AZ (US);
William C Gilbert, Scottsdale, AZ (US);
Honeywell Inc., Minneapolis, MN (US);
Abstract
An improved squelch circuit which utilizes a phase-locked-loop (PLL) arrangement to track the carrier signal and identify when audio communication should be curtailed. The lock detect circuit of the PLL is used for a signal-to-noise monitor. As the loop locks and unlocks, the lock detect line pulses. These pulses are integrated to give a direct current (DC) level. This DC level is proportional to the signal-to-noise ratio of the carrier signal. The signal-to-noise level is monitored by the squelch gate until a threshold is passed. Falling below the threshold results in a squelching of the audio, when the ratio exceeds the threshold, then audio is commenced. The circuit is enhanced by the ability to automatically adjust the threshold level once the PLL has locked onto the signal. Further, in some embodiments of the invention, the PLL also adjusts its bandwidth if the receiver's bandwidth is changed, thereby allowing the PLL to monitor the signal and not open and close the squelch intermittently when the signal strength is only marginal.