SIGNAL COUPLING CIRCUIT

PURPOSE:To prevent a signal from being changed by connecting a filter passing through the signal frequency band of one transmission line of two signal transmission lines in parallel with another filter passing through the signal frequency band of the other transmission line. CONSTITUTION:The 1st signal transmission line connected to a terminal A is connected to a hybrid circuit 1 via an amplifier 3 and a resistor 4. Furthermore, the 2nd signal transmission line connected to a terminal B is connected to the circuit 1 via a transformer 2 and a filter 5 taking a signal B of the 2nd signal transmission line as the pass band. The filter 6 taking a signal A as the pass band is connected in parallel with the filter 5 and a termination resistor 7 having approximated characteristic impedance is connected to the filter 6. Then the impedance characteristic in each direction of the circuit 1 is close to the characteristic impedance thereby avoiding the amplitude and phase change of the signal.