| 摘要 |
PURPOSE:To improve the modulation frequency characteristics and relaize a wide band, by setting the reciprocal value of the delay time of propagation of an elastic surface wave filter used for a delay element at a double value or more of the maximum modulation frequency. CONSTITUTION:Action of oscillation is carried out by a positive feedback loop comprising an amplifier 31, a variable phase shifter 32 and a band pass filter 33, and the phase condition is varied by the shifter 32 to control the frequency of oscillation. In this case, the degree of inclination, i.e., the delay time of propagation is decided for the filter 32 so that the phase characteristics of the filter is set at pi radian or a lower change of phase with the frequency axis that is decided by the maximum modulation frequency Fmax. As a result, the delay time of propagation of the filter 33 can be set at 1/2.Fmax or less. |
