Title:
MODULATION INDEX DETECTING METHOD FOR NONLINEAR DIGITAL MODULATION SYSTEM AND CIRCUIT THEREOF
Document Type and Number:
Japanese Patent JP3509076
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To provide a modulation index detecting method for solving the problem of conventional method being unable to estimate the modulation index of a nonlinear digital modulation system, including the GMSK(Gaussian-filtered minimum shift keying) system having inter-code interference, with high accuracy.
SOLUTION: A symbol clock synchronization processing 1 is executed for a received signal, after I-Q detection processing in the nonlinear digital modulation system with an inter-code interference, such as the GMSK system on the basis of a preset modulation speed to obtain symbol components In, Qn. An inter-symbol phase difference processing 3 is applied to phase information, obtained by applying symbol detection processing 2 to the symbol components to obtain an inter-symbol phase difference. When the modulation index is obtained from the inter-symbol phase difference, only the inter-symbol phase difference of a particular code sequence having little inter-code interference is extracted from among a plurality of inter-symbol phase differences continuously received from a symbol transition discrimination processing 5, after only the inter-symbol phase difference information is subjected to absolute value processing, integration/averaging processing is conducted for a plurality of pieces of phase difference information and the result is given to a modulation index detection processing 4. The modulation index detection processing 4 obtains the modulation index, from only the inter-symbol phase difference of one and the same consecutive code sequence.
Inventors:
Ishii, Hiroyuki
Application Number:
JP2001205611A
Publication Date:
March 22, 2004
Filing Date:
July 06, 2001
Export Citation:
Assignee:
NEC CORP
MINISTRY OF PUBLIC MANAGEMENT HOME AFFAIRS POSTS & TELECOMMUNICATIONS
MINISTRY OF PUBLIC MANAGEMENT HOME AFFAIRS POSTS & TELECOMMUNICATIONS
International Classes:
G01R29/06; H04L27/10; H04L27/14; (IPC1-7): H04L27/10; G01R29/06; H04L27/14
Attorney, Agent or Firm:
後藤 洋介 （外２名）