Design of On-Chip Dual-Band Bandpass Filter Using Lumped Elements in LTCC Technology

In this brief, a novel on-chip dual-band bandpass filter (D-BPF) with two independently controllable transmission zeros (TZs) is proposed. Based on resonators transformation, the schematic and design procedure of the filter are presented. Using even-/odd-mode analysis, analytical equations are used for demonstration of the theory. As an example, a 3.32/5.17-GHz D-BPF with 3-dB fractional bandwidth (3-dB FBW) of 25.45%/14.20% for 5G applications is designed, fabricated, and measured. The size of the filter in low-temperature cofired ceramic (LTCC) is only 11.4 mm * 6 mm * 0.94 mm. The filter has been successfully measured with the minimum insertion loss of 1.38/1.53-dB and high return loss of 28/23-dB at the center frequency.