PURPOSE: To provide the correcting circuit, which equivalently corrects the differential gain characteristic of a modulator, and the modulator and the radar equipment which use this circuit.

CONSTITUTION: A correcting circuit 1 is connected to the preceding stage of a voltage controlled oscillator 2, which has the oscillation frequency controlled by a control voltage, and corrects the differential gain of this voltage controlled oscillator 2. This correcting circuit 1 includes a first resistor R1, which is connected in series to the input side of the voltage controlled oscillator 2, and the series connection of a second resistor R2 and a first diode D1 which is connected in parallel to the input side of the voltage controlled oscillator 2. A first bias power source E1 which gives a bias in the forward direction is connected to the first diode D1.