To demonstrate the applications of the studies in the previous sections, several second-order Butterworth filters using coupled lines with capacitive loads at one end were designed. This is because the tunability of the transmission zero of this type of circuits is better than the one with one end opened or shorted to ground. Moreover, since the capacitive loads can be realized byopen stubs, the fabrication of these kinds of circuits is easier than the one with inductive loads. Fig. 6 shows the circuit configuration of these filters. It is well known that a section of transmission line opened at both ends behaves like a resonator when it
đang được dịch, vui lòng đợi..
