Widely Tunable Highly Linear Power Transfer Filter

With the rapid development of several areas such as radar communication, electronic counter measure, data acquisition and frequency modulation, the system needs filter to have the advantage of wide bandwidth, small volume and narrow relative bandwidth. But the traditional module filter can not meet these demands, and the electrically tunable filter can do it.This dissertation focused its research on electrically tunable filter with the bandwidth from 1.5MHz to 1000MHz. First, in order to realize the wide bandwidth, the circuit structure is research, and it includes capacitive coupling and inductive coupling which is primary studied.Because of the effect of elements to the linearity, inductance and capacitance are researched to meet the demand of high linearity. The choice of permeability of magnetic core is important, and the way of connecting for varactor diodes is studied. Two projects which are inductance direct coupling and inductance indirect coupling are designed. With the help of software simulation and actual debugging, inductance direct coupling is chosen as the last project. Cavity is divided into many different parts to reduce the interference and integrated switch is used to realize miniaturization. The 1.5-1000MHz electrically tunable filter can achieve less than 7dB insertion loss and 6%-8% relative bandwidth.