| 摘要 |
PURPOSE:To achieve a frequency modulator having an excellent group delay characteristic with low cost, by adding a varactor diode having the same characteristic as a varactor diode varying the oscillating frequency in a base band zone. CONSTITUTION:In a frequency modulator varying an oscillating frequency with a modulation signal applied across a varactor diode X1, a varactor diode X2 having almost the same characteristic as a diode X1 and a bias voltage E2 giving a reverse bias to the X2 are provided at a base band input terminal 1. Taking a voltage giving reverse bias to the diode X1 of the frequency modulating circuit as E1, AC voltage applied to the diode X1 as v, and an AC signal voltage at the base band input as v', when E2 is set so that v/v'=E1/E2 is satisfied, the group delay characteristics caused by this frequency modulation can be made to zero. |
