A compact and low‐loss LTCC diplexer with high‐band selectivity and high isolation for dual‐band applications

Abstract

AbstractThis 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 of the fabricated diplexer including CPW pads is 3.45 × 4.0 × 0.7 mm3. 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. © 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