| 摘要 |
PROBLEM TO BE SOLVED: To reduce phase noise and to widen a dynamic range by alternately shifting the frequency of second local oscillation signals by the width of the 1/2 of a prescribed step in the frequency tuning device of a double superheterodyne system for varying and tuning the frequency of first local oscillation signals outputted from a first local oscillator by the prescribed step. SOLUTION: This frequency tuning device for which the first local oscillator 12 is constituted of a PLL synthesizer varies the frequency of the first local oscillation signals outputted from the first local oscillator 12 by the step of 200 kHz. Since the reception of the step of 100 kHz cannot be performed as it is, the frequency of the second local oscillation signals outputted from a second local oscillator 15 is alternately shifted by the width of 100 kHz, the multiplication number of a reference clock performed in the PLL synthesizer for constituting the first local oscillator 12 is reduced and the phase noise is reduced though it is the frequency tuning device of a wide dynamic range.
|
