NEGATIVE FEEDBACK TRACKING FILTER DEMODULATOR

• Format: Patent
• Language: English
• Published: 12.05.1981
• Subjects: BASIC ELECTRONIC CIRCUITRY; DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TOANOTHER; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; PICTORIAL COMMUNICATION, e.g. TELEVISION; RESONATORS; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

PURPOSE:To obtain a demodulator with high sensitivity, which has little distortion, by forming the negative feedback loop by a tracking filter and a phase detector. CONSTITUTION:An FM signal 3 is split into two and is supplied to both the tracking filter 2 and the phase detector (PSD)5 at the same time. A signal which has passed through the tracking filter 2 is subject to phase deviation by the phase characteristic which the filter 2 has, the signal 4 is compared as to the phase with the FM signal 3 by the phase detector 5, and the phase deviation generated by the tracking filter 2 is detected. This detection signal passes the loop filter 6, becomes a signal which is equivalent to a base band signal, and is fed back to the tracking filter 2. This loop is formed so that the center frequency of the tracking filter 2 always tracks the instantaneous frequency of the FM signal 3, and the negative feedback loop is formed. In this way, a demodulation output 4 which has little distortion can be obtained by absorbing a drift, etc.