FRONT END CIRCUIT OF RECEIVER

PURPOSE:To form easily an signal input to a balanced mixer by constituting an RF tuning circuit of a pi type tuning circuit consisting of a coil with an intermediate tap, and two capacitors, and applying a local oscillating signal (LO signal) to the intermediate tap. CONSTITUTION:An RF tuning circuit is constituted of a pi type circuit consisting of a coil 9' having an intermediate tap, and two capacitors 10', 10'' having an equal capacity each other. An RF signal applied to an input terminal 1 is amplified by an ampliier 7, and thereafter, its frequency is selected by said tuning circuit. On the other hand, an LO signal is applied to the intermediate tap of the tuning coil 9'. Accordingly, in case of seeing both ends of the coil 9', the RF signal and the LO signal are outputted in an added shape to one end, and the inversion RF signal and the LO signal are outputted in an added shape to the other end. These signals are inputted to the gates of balanced mixer use FETs14, 14' of the pose-stage, respectively.