| 摘要 |
PROBLEM TO BE SOLVED: To always execute A/D conversion with an optimum dynamic range, even if high-speed phasing exits and to provide sufficient quantization precision. SOLUTION: An I-component and a Q-component, which are obtained by making orthogonal detection output signals pass through LPFs 8 and 9, are amplified to values fitted to the dynamic ranges of A/D converters 10 and 11 according to the control voltage of the output of a control voltage generating circuit 20 and are inputted to the A/D converters 10 and 11. The values of amplitude in the output signals of the circuit 18 and 19 are detected by a necessary amplitude detector 21. The values of the amplitude are compared with the dynamic ranges of the A/D converters 10 and 11, the control voltage is generated according to a compared result, and the gains of the variable gain control amplifier circuits 18 and 19 are controlled. When necessary amplitude is larger than the dynamic range, the gain becomes small and when amplitude is smaller, it becomes large. |
