IMPROVED POWER DURABILITY OF SURFACE-ACOUSTIC-WAVE FILTERS FOR AN ANTENNA DUPLEXERS

For portable telephone applications, we improved the power durability of ladder-type filters composed of one-port surface acoustic wave (SAW) resonators. In these ladder-type filters, the chip temperature was raised and power durability was weak around both cut-off frequencies in transmission characteristics. Power durability tests of a duplexer composed of ladder-type filters showed that the receiver filter (Rx) in which the power was leaked from the transmitter one (Tx) was weaker than the Tx. We therefore studied Rx in this work. In filter design, reducing the resonator resistance to suppress the rise in chip temperature improved power durability. The lifetime of electrode material was improved to up to 10,000 times longer than that of an Al-Cu single-layer film by use of a 3-layered film of Al-Cu/Cu/Al-Cu.