CHANNEL SELECTION DEVICE FOR DOUBLE CONVERTER RECEIVER

• Main Author: OKAWA YASUHITO
• Format: Patent
• Language: English
• Published: 30.04.1993
• Subjects: BASIC ELECTRONIC CIRCUITRY; DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TOANOTHER; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION

PURPOSE:To easily realize a broad band VCO forming a local oscillator circuit, to realize the setting of a local oscillation signal with a single loop and to reduce the signal processing scale. CONSTITUTION:A mixer 1 outputs an intermediate frequency signal IF1 resulting from conversion of a desired channel from an RF signal with an applied local oscillation signal Lo1. Moreover, a mixer 2 uses a local oscillation signal Lo2 to frequency-convert the intermediate frequency signal IF1 into an intermediate frequency signal IF2. An FM detector 3 demodulates the intermediate frequency signal IF2 into original amplitude information. A control voltage to a VCO 4 is generated by a D/A converter 6 and sent. A step voltage of the VCO 4 is decided by the relation between a maximum control voltage and a quantization number of the D/A converter 6 and decided to the point of a large output frequency change with respect to a change in the control voltage, e.g. in a range of channel selection 30-50. The oscillating frequency of the VCO 4 is changed corresponding to the control voltage being an output voltage of the D/A converter 6.