The Design And Research Of Digitial Control Electrically Tunable Microstrip Combine Filter

Following the fast development of Microwave communication and Radar system, Microwave filter used widely, the best future filter become the hot topic .This thesis design a new digital contrl of microwave combline tunable passband filter , This filter enjoy such merits: range of tunable centrofrequency is big, its structure is compact and almost changeless bandwith and filter characteristics. In the thesis ,firstly,design the circuit structruct and the approximate equivalent model of combline filter, varactors were used for tuning components,Secondly , the digital-controlled electrically tunable filter has been manufactured, its center frequencies can be tuned in 900~1200 MHz, each was controlled by 8-digit binaries. Thirdly , simulation process by software, and test the filter. Finally, by analyzing to find the factor which affact the filter. And the experimental result is fairly consistent with the above theoretical analysis.