| 摘要 |
PROBLEM TO BE SOLVED: To reduce spurious and phase noises.SOLUTION: A local oscillator comprises a digital control oscillator, a frequency multiplier, a phase data generator, a subtractor, a moving average filter and a loop filter. The frequency multiplier multiplies a frequency of a reference signal by N (N is an integer equal to or greater than 2) to generate a multiplied reference signal. The phase data generator outputs phase data of an oscillation signal synchronously with the multiplied reference signal. The subtractor subtracts the phase data from reference phase data for setting an oscillation frequency and outputs a subtraction result as first phase error data. The moving average filter outputs a moving average of the latest (N-1) pieces of the first phase error data as second phase error data synchronously with the multiplied reference signal. The loop filter filters the second phase error data and outputs an oscillator control value.SELECTED DRAWING: Figure 1 |
