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. 21, 2000
Filed:
Nov. 24, 1997
Hidenori Maruyama, Tokyo, JP;
NEC Corporation, , JP;
Abstract
Disclosed is an automatic frequency control circuit for correcting the influence of frequency offset in a radio data communication terminal of a scheme in which transmission path characteristics are obtained during the preamble period by narrow-band modulation to equalize the received signal. The automatic frequency control circuit includes, on the transmitter side, a unit for repeatedly transmitting the pattern of a predetermined pseudo noise (PN) signal serving as a preamble signal, on the receiver side, a unit for calculating the phase difference per PN cycle on the basis of the component (real and imaginary part amplitude values) of a PN signal one cycle before that is quadrature-modulated during a predetermined period of the preamble, and the component of a current PN signal, a unit for dividing the phase difference by the number of symbols of one PN cycle to obtain the phase difference (.DELTA..theta.) of the unit symbol, a unit for holding .DELTA..theta. during the burst period, a unit for integrating .DELTA..theta. in units of symbols during data demodulation, a unit for converting the integrated value into real and imaginary part amplitude values, and a unit for correcting the phase of the demodulated received signal on the basis of the obtained real and imaginary part amplitude values.