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:
Jan. 31, 1989
Filed:
Feb. 26, 1987
Joseph P McGeehan, Corsham, GB;
Andrew Bateman, Bath, GB;
National Research Development Corporation, London, GB;
Abstract
In previous transparent tone-in band systems the notch has been removed from the frequency spectrum before a carrier signal carrying data has been demodulated. The present specification describes an arrangement in which data is recovered by first and second mixers from a signal having a spectrum containing a notch. Phase and frequency locking is obtained: either by using a third mixer fed from the inputs to the first and second mixers to provide, indirectly, one signal for a fourth mixer which also receives the carrier signals and provides demodulating signals for the first and second mixers; or by a correction system coupled to the outputs of the first and second mixers for correcting demodulating signals supplied to these mixers.