LINE QUALITY ESTIMATE CIRCUIT

• Main Author: SHIBATA KINYA
• Format: Patent
• Language: English
• Published: 02.04.1991
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

PURPOSE:To output estimate information of line quality with highly effective line quality by providing a noise level detection means or the like so as to estimate the line quality over a wide range even in the state before unique word undetection or in the case of burst transmission. CONSTITUTION:When a data burst signal is received, its intermediate frequency signal RD is fed to a base band processing circuit 30 and a line quality estimate circuit 40 via an AGC circuit 10 and a demodulation circuit 20. An HPF 41 of the circuit 40 extracts a noise component at first, a noise level is detected via a detection circuit 42 and an LPF 43 and fed to a hold circuit 46 via a level conversion circuit 44 and an A/D converter 45. The circuit 46 receives an output of the converter 45 and an output of a CR period estimate circuit 47 to detect a noise level for a carrier reproduction signal CR period in an analog demodulation signal and the level is converted into a C/N by a C/N detection circuit 48 and outputted. Thus, the line quality is estimated over a wide range and estimate information of the line quality with high validity is obtained.