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. 24, 1985
Filed:
Apr. 15, 1983
Jean-Edgar Picquendar, Saint Remy les Chevreuse, FR;
Jeannine Henaff, Clamart, FR;
Michel Feldmann, Paris, FR;
L'Etat Francais, Issy les Moulineaux, FR;
Abstract
The invention relates to a filter for demodulating signals modulated in frequency in binary manner by the switching of two frequencies F.sub.a and F.sub.b. On a piezoelectric crystal, is produced two surface wave filtering units, each comprising a transmitting transducer and a receiving transducer with interdigitated electrodes. The number of electrodes of the receiving transducer of the first unit is substantially equal to twice (2F.sub.a -F.sub.b)/2(F.sub.b -F.sub.a ) with a spacing of v/(2F.sub.a -F.sub.b), in which v is the propagation rate. In the case of the second unit, this number is approximately twice (2F.sub.b -F.sub.a)/2(F.sub.b -F.sub.a) with a spacing of v/(2F.sub.b -F.sub.a). The receiving transducers are preferably subdivided in each case into two juxtaposed transducers, whereof one is set back with respect to the other by a distance of approximately v/4F.sub.a for the first unit and v/4F.sub.b for the second.