Equalizing of group delay for feed forward amplifier using dielectric filters

In recent years, development of new network systems and base stations are strongly required as users for W-CDMA, CDMA 1X of 3G cellular phones increased enormously. A feedforward (FF) amplifier is one of the leading mainstreams for base station system. Electrical delay lines are very important devices to improve the performance of the FF amplifiers. The FF amplifier use a number of delay filters which is the key device to attain good characteristics. Nevertheless, delay filters have a characteristic of large delay deviation though temperature characteristic is stable and low loss. In this study, a small delay deviation by 4-pole type filter using double coupling is realized. This delay filter using dielectric resonator shows stable characteristic to the changing of temperature, reduction of delay deviation and low loss.