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. 13, 1981
Filed:
Oct. 11, 1978
Andre E Desblache, Nice, FR;
International Business Machines Corporation, Armonk, NY (US);
Abstract
A method and device for measuring the slope of the envelope delay characteristic in a transmission channel. The slope is determined from a received measurement signal having a frequency spectrum that includes three rays at frequencies f.sub.o, f.sub.1 and f.sub.2, which are approximately located in the center and at the edges of the useful passband of the channel. At the output of the channel, the three components at frequencies f.sub.o, f.sub.1 and f.sub.2 are extracted from the received measurement signal, and the instantaneous phases .psi.0, .psi.1 and .psi.2 of these three components are measured. The value of the slope S of the envelope delay characteristic is obtained from the relation ##EQU1## where .phi..sub.o ', .phi..sub.1 ' and .phi..sub.2 ' are the phases of the three rays at frequencies f.sub.o, f.sub.1 and f.sub.2 of the measurement signal sent over the channel. When the data transmission system employs double sideband-quadrature carrier (DSB-QC) modulation, the measurement signal is generated by causing the carrier to undergo successive phase changes of +.pi./2 and -.pi./2 radians at the signaling rate. The receiver includes a set of fixed equalizers and the appropriate fixed equalizer is selected as a function of the measured slope.