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:
Nov. 15, 1994
Filed:
Jul. 18, 1991
David L Roberson, Forest, VA (US);
Pulse Electronics, Inc., Rockville, MD (US);
Abstract
A direct sequence digital spread spectrum receiver acquires and maintains synchronization in a reliable, yet simple manner, even under severe multipath and interference conditions. A sliding correlator and a voltage controlled crystal oscillator (VCXO) cooperate to acquire initial synchronization, and once synchronization is acquired, the VCXO is linearly frequency modulated (FM) for accurate tracking. The difficult problem of keeping the receiver code clock synchronized to that of the transmitter under severe multipath and interference conditions is solved by virtue of a dual switched bandwidth low pass filter section of the tracking circuit, allowing a wide bandwidth for initial acquisition and tracking but once the clocks are aligned, a narrow loop takes over that follows the transmitter closely. A commercially available intermediate frequency (IF) integrated circuit (IC) is used as an amplitude modulated (AM) detector to achieve the large dynamic range required. The IF IC has an internal received signal strength indicator (RSSI) output which is used to demodulate the amplitude variations generated by the tracking circuit.