Research on Unbalanced to Balanced Band-pass Filter with Tapped Capacitor for Selectivity Improvement Using LTCC and Balanced Input-Output Band-pass Filter

• Main Authors: Nen-Yen Wu, 吳能炎
• Other Authors: Shyh-Jong Chung
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/35484397106282302520

碩士 === 國立交通大學 === 電機學院碩士在職專班電信組 === 96 === This study proposes an unbalanced to balanced band-pass filter and a balanced input-output band-pass filter. Firstly, an unbalanced to balanced band-pass filter which is composed from a Marchand balun circuitry using Low Temperature Co-fired Ceramic (LTCC) technology is proposed and designed. Based on the Marchand balun, this work uses a shunt capacitor connecting the input port to ground, and then lets the open end of the input transmission line be short to ground, thus can derive a resonator. Besides, a capacitor is connected between the two balanced output ports of the Marchand balun, and remaining the other end of each output transmission line connected to ground. Therefore, it can form another resonator. For improving the performance of selectivity, tapped-C is used to enhance the circuit Q of the resonator and to couple the signal to the next stage. The proposed unbalance to balance band-pass filter which has low insertion loss at pass band and good attenuation at suppression area can be applied in Bluetooth or IEEE 802.11b/g WLAN (Wireless Local Area Network). Secondly, a balanced to balanced band-pass filter is proposed. Also based on the Marchand balun mentioned above, a capacitor is connected between the two balanced output ports, and thus forms a parallel-LC resonator by co-operating the grounded transmission line. After duplicating the same balanced ports with back-to-back structure, a balanced to balanced band-pass filter is derived. In order to verify the circuit simulation, we used low loss R/T Duroid/5880 substrate and high-Q discrete ceramic capacitors to implement the experiment circuit. The proposed balanced to balanced band-pass filter can also be applied in Bluetooth or IEEE 802.11b/g WLAN (Wireless Local Area Network).