Synchronous detector and methods for synchronous detection

• Main Author: LEO MONTREUIL
• Format: Patent
• Language: English
• Published: 11.12.1997
• Edition: 6
• Subjects: BASIC ELECTRONIC CIRCUITRY; DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TOANOTHER; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; MODULATION; PICTORIAL COMMUNICATION, e.g. TELEVISION; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

A synchronous detector has first and second mixer circuits and a voltage controlled oscillator. The voltage controlled oscillator provides a local oscillator signal directly to the second mixer circuit and indirectly to the first mixer circuit through a phase transformer. The output of the first and second mixer circuits are combined in combiner circuitry to produce a jitter cancelled output signal. The jitter cancelled output signal is filtered in a loop filter and applied to the voltage controlled oscillator to control the frequency and phase of the local oscillator signal. The combiner circuitry includes a summer and a jitter cancellation filter. The jitter cancellation filter is preferably a high pass filter matched to spectrum of the signal detected. The output of the first mixer circuit is passed through the high pass filter into one input of the summer while the output of the second mixer circuit is passed to the second input of the summer. The output of the summer is passed to the loop filter.