The K-PCS and W-CDMA dual band dielectric duplexer and bandpass filters have been designed and fabricated. The dual band duplexer consists of the separate monoblock K-PCS and W-CDMA duplexers using common antenna port. The coupling capacitance and I/O impedance matching have been designed to minimize the cross interference between the bands. Isolations of crosspoint between Tx and Rx in K-PCS and W-CDMA dualband were about 47 dB and 100 dB, respectively. On the other hand, isolations of Tx and Rx in K-PCS and W-CDMA were about 66 dB and 65 dB, respectively. The difference between 47 dB and 100 dB originated from the different center frequencies in Tx and Rx of K-PCS and W-CDMA bands. The coupling capacitance of the bandwidth, I/O capacitance of I/O matching and impedance matching, and various capacitances were important role to fabricate the dielectric duplexer and bandpass filters.

This paper focuses on thermal properties of a newly prepared composite material by nano-silica and micro-silica mixture. Nano-silica and micro-silica mixture composites were made by dispersing surface treated nano-silica (average radius: 10 nm) and micro-size silica in epoxy resin. To investigate the effects of nano-silica and micro-size silica mixture(ENMC), the glass transition temperature (Tg), coefficients of thermal expansion(CTE) and elastic modulus of DMA properties by DSC, TMA and DMA devices were measured for the ENMC according to increase nano-silica addition contents and EMC. All properties of the neat epoxy were improved by the addition of micro-silica, which was improved much further by the addition of surface treated nano-silica to the EMC system.