| 摘要 |
PURPOSE:To obtain a local oscillator for a radar equipment with low noise in which its frequency is selected for a wide band. CONSTITUTION:A noise suppressing circuit (composed of circuit components 25-31) is added to a PLL circuit (composed of circuit components 13-17). A discriminator (composed of circuit components 25-28) detects FM noise with the sensitivity of 2piupsilondkd when a phase difference between a signal whose frequency is fd resulting from delaying an output signal of a VCO 16 by a prescribed time upsilond and a signal whose freqyency is fR while it sphase is shifted by a prescribed phase angle theta is 90 deg.. A superimposing circuit (composed of circuit components 29-31) superimposes a detected noise signal onto the output control voltage of a loop filter 15. The FM noise appearing at the output of the VCO 16 is suppressed by the gain of 2piupsilondkdG.kv. A switching step is 1/upsilond, that is equal to or the integer multiple of a comparison frequency and the relation of fL=fCOmP(N+ or -n)=fLo+ or -n/upsilond is satisfied. Since the PLL circuit is not concerned with noise suppression, the broad band processing is attained. |
