The invention provides an electrically tunable filter, relating to the technical field of
electrocommunication, aiming at solving the technical problems of narrow tunable bandwidth, the frequency being less than 1G, bad reliability, big
insertion loss, limited
signal receiving range and the like existing in the prior electrically tunable filter products. N series inductances are connected in series between the
radio frequency input end and the
radio frequency output end in the invention; N-1 parallel inductances and N-1 three-terminal circuits are connected in parallel between N series inductances; one end of each parallel
inductance is connected between the above two adjacent series inductances and the other end thereof is connected to the ground; one of the three-terminal circuits is a variable
capacitance diode, the input end thereof is connected between the input ends of the above adjacent parallel inductances and the input ends of the parallel inductances, and the output end thereof is connected with the other circuit of
capacitance of the three-terminal circuit and then is connected to the ground; and the input end of the filter
inductance is connected between the output endof the variable
capacitance diode and the input end of the capacitance, and the output end thereof is connected with a
voltage control end. The invention is applicable to the fields of
microwave communication,
ultra wideband receivers, electronic devices and the like.