| 摘要 |
An AFC (Automatic Frequency Control) device and a method of controlling reception frequency in a dual-mode terminal. When a dual-mode terminal uses one or two AFC circuits (151), time required for acquiring tracking synchronization in a PLL circuit (117, 137) for a frequency can be reduced using a test augmentation frequency being an integer multiple of a tracking synchronization acquiring residual frequency of a PLL (117, 137) circuit for another frequency to which the first frequency transits for reliable synchronization acquisition. Errors with respect to an output dynamic range caused by use of two AFCs are reduced and thus the demodulation performance of a receiver is ensured by varying quantization bits of an A/D clock based on the dynamic range of residual errors in a frequency area. The demodulation performance can also be ensured by operating an ACPE circuit for an AFC circuit having many residual frequency errors. In this method, the frequency characteristics of the dual-mode terminal are stabilized and the stability of a demodulator is increased due to a frequency offset. As a result, the stable demodulator performance is ensured. |
