LTCC Vertically-Stacked Cross-Coupled Bandpass Filter for LMDS Band Applications

Abstract

This study develops a compact 28 GHz bandpass filter on a low-temperature co-fired ceramic substrate for applications in LMDS (Local Multipoint Distribution Service) bands. The filter comprises two pairs of verticallystacked cross-coupled open loops with vertical interconnection structures, achieving compactness, high integration, and superior frequency selectivity. Attaining selective response with two transmission zeros requires adjusting the couplings of adjacent resonators and external quality factor. The open loops are fed by using the three-via vertical interconnections to prevent any electrical effect on the filter. Measurements correlate closely with the simulation results: this study achieved a bandwidth of 2.1 GHz (27.6-29.7 GHz) with two zeros located at 25.8 GHz and 31.1 GHz, and a compact size of 2.69 × 2.66 × 0.4 mm 3 .

Design of Compact Dual-Band Filter in Multilayer LTCC With Cross Coupling

“…Dual-band 4 4.8 dB 0.93λ g × 0.88λ g This work Dual-band 6 2.4 dB 1.29λ g × 0.57λ g the size is comparable to those in [7] and [10]. The proposed filter has two passbands, while with the insertion loss and size comparable to those in [8] and [9].…”

“…Order Insertion loss Circuit size [6] Single-band 3 5 dB 5λ g × 2λ g [7] Single-band 4 3.2 dB 0.57λ g × 0.56λ g [8] Single-band 2 2.09 dB 1.27λ g × 0.71λ g [9] Single-band 4 2.4 dB 1.44λ g × 0.79λ g [10] 1st Dual-band 3 4.5 dB 1.12λ g × 0.9λ g [10] 2nd…”

“…These filters usually occupy a large circuit area because of the planar arrangement of the resonators. As multimedia satellite communication requires components with low weight, small size and high reliability, multilayer low-temperature cofired ceramic (LTCC) technology has been considered as an attractive solution [5][6][7][8][9][10][11][12][13][14][15]. LTCC band-pass filters were introduced in [5][6][7][8][9] while dual band filters implemented in LTCC technology were proposed in [10,11].…”