An Ultra Miniaturized Dielectric Band Pass Filter For 800 Mhz Band Cordless Telephone System

Abstract

&SQUSX A new miniaturized dielectric band pass filter for 800MHz band cordless telephone terminal is developcd. This filter is surface mount device (SMD). Its construction is dielectric monoblock having plural coaxial extending holes, it resonates with a quarter wavelength TEM mode. This monoblock resonator has high dielectric constant (K=90) and its surfaces are covared with copper plating electrode except one surface. The volume has reduced to 60 percents of conventional type. One end of each resonator has stray capacitance (Cs)i, which create comb-line coupling between each resonator. As its open end of resonator is provided in the holes, RF leakage is suppressed. The input and output terminals of this filter are formed as the electrodes on both side surfaces of the monoblock that are isolated from outer conductor. Thus, it is able to apply for surface mount technology without metallic pin terminals. As compared with conventional filter, the number of parts of the filter is reduced from seven to one. Consequently the productivity of this filter is improved. Asthe new dielectric filteroccupiesso small area to mount, it is suitable to high density mount for a cordless telephone terminal.