| 摘要 |
To generate a fixed frequency offset in a direct conversion receiver (200) a phase ramp representing the frequency offset if generated. This phase ramp is combined with the demodulated phase component of a received signal. A phase wrap detection and compensation circuit (224) is capable of detecting and compensating for phase wrap that occur in the phase ramp by differentiating the input and detecting when a phase wrap is about to occur and causes a switch (316) to flip between two conditions. A first condition couples the phase ramp to the output. A second condition compensates when a wrap around has been detected. As such, a VCO (218) produces a local oscillator having a fixed frequency offset that is immune from locking problems that occur when a phase wrap is introduced.
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