A COMPACT AND LOW-LOSS LTCC DIPLEXER WITH HIGH-BAND SELECTIVITY AND HIGH ISOLATION FOR DUAL-BAND APPLICATIONS

This article presents a compact and low-loss diplexer for dual-band applications using a LTCC (low temperature co-fired ceramic) multilayer technology. This diplexer is composed of the high-pass filter (HPF) and low-pass filter (LPF) in order to separate GSM (global system for mobile) and CDMA (code division multiple access) band. For enhancing band selectivity of the diplexer, a shunt capacitor and inductor are designed in the HPF and LPF, respectively. In addition, a transmission zero is designed at the stopband of the LPF using a shunt inductor for improving isolation characteristics. The diplexer is realized in a 6-layer LTCC substrate with a relative dielectric constant of 7. The size or the fabricated diplexer including CPW pads is 3.45 x 4.0 x 0.7 mm(3). A measured insertion loss (IL) and return loss (RL) of the GSM band are less than -0.54 dB and -10.50 dB, respectively. In the case of CDMA band, the IL of -1.13 dB and RL of below -6.16 dB are archived. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1134-1137, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25137