Portal de Periódicos da CAPES

Compact LTCC balanced bandpass filter using distributed‐element resonator

2013; Institution of Engineering and Technology; Volume: 49; Issue: 5 Linguagem: Inglês

10.1049/el.2012.4071

1350-911X

Jianxin Chen, Chuan Shao, Qing‐Yuan Lu, Hongjun Tang, Zhi‐Hua Bao,

Photonic Crystals and Applications

Electronics LettersVolume 49, Issue 5 p. 354-356 Microwave technologyFree Access Compact LTCC balanced bandpass filter using distributed-element resonator J.-X. Chen, Corresponding Author J.-X. Chen [email protected] School of Electronics and Information, Nantong University, 9 Seyuan Road, Nan Tong, 226019 Jiangsu Province, People's Republic of ChinaSearch for more papers by this authorC. Shao, C. ShaoSearch for more papers by this authorQ.-Y. Lu, Q.-Y. Lu School of Electronics and Information, Nantong University, 9 Seyuan Road, Nan Tong, 226019 Jiangsu Province, People's Republic of ChinaSearch for more papers by this authorH. Tang, H. TangSearch for more papers by this authorZ.-H. Bao, Z.-H. Bao School of Electronics and Information, Nantong University, 9 Seyuan Road, Nan Tong, 226019 Jiangsu Province, People's Republic of ChinaSearch for more papers by this author J.-X. Chen, Corresponding Author J.-X. Chen [email protected] School of Electronics and Information, Nantong University, 9 Seyuan Road, Nan Tong, 226019 Jiangsu Province, People's Republic of ChinaSearch for more papers by this authorC. Shao, C. ShaoSearch for more papers by this authorQ.-Y. Lu, Q.-Y. Lu School of Electronics and Information, Nantong University, 9 Seyuan Road, Nan Tong, 226019 Jiangsu Province, People's Republic of ChinaSearch for more papers by this authorH. Tang, H. TangSearch for more papers by this authorZ.-H. Bao, Z.-H. Bao School of Electronics and Information, Nantong University, 9 Seyuan Road, Nan Tong, 226019 Jiangsu Province, People's Republic of ChinaSearch for more papers by this author First published: 01 February 2013 https://doi.org/10.1049/el.2012.4071Citations: 33AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract Presented is a vertically and horizontally folded half-wavelength resonator in a three-dimension (3D) environment and its application to a balanced bandpass filter (BPF). Benefiting from the multilayered resonator based on the transmission line theory and low temperature co-fired ceramic (LTCC) technology, the proposed balanced BPF can obtain compact size and good performance. For demonstration, a LTCC balanced BPF centred at 2.45GHz has been designed using the proposed resonator, and the size of the circuit is 6.0 × 5.0 × 1.6 mm3. Introduction With the rapid development of modern wireless communication systems, increasing demands for balanced circuits are arising. The balanced bandpass filter (BPF), as an essential passive component, usually occupies a very large area of the printed circuit board (PCB). As a result, it is very important to reduce the filter's size. In the developed balanced BPFs, planar topologies are in the majority [1, 2]. They all have good performance, but they may suffer from bulky size, which would be an obstacle in practical applications. Recently, low temperature co-fired ceramic (LTCC) technology has attracted much attention as it can reduce the circuit's size significantly. Accordingly, many lumped-element or semi-lumped-element LTCC BPFs with compact size and good performance have been demonstrated [3, 4]. However, as the frequency increases, the parasitic effect and unwanted coupling may influence the original characteristic of the lumped element. Therefore, the values of the lumped element cannot be accurately predicted and controlled. The distributed resonator and filter do not have the same problem except the relatively large sizes [5, 6]. Hence, size reduction is a challenge in designing the LTCC distributed resonator and filter. In this Letter, a vertically and horizontally folded half-wavelength (λg/2, λg is the guided wavelength at the centre frequency) resonator based on the transmission line theory is proposed. Accordingly, a balanced BPF constructed by a pair of the multilayered resonators has been designed and fabricated in LTCC technology. In this way, the proposed distributed-element LTCC balanced BPF can obtain the same performance and compact size as the LTCC balanced BPF based on lumped elements [4]. Fig 1Open in figure viewerPowerPoint Proposed distributed-element resonator a 3D view (actual ground not shown) b Cross-section view and four layer configurations Folded resonator and filter design The three-dimensional (3D) configuration of the proposed distributed-element resonator is presented in Fig. 1a. The conventional open-ended λg/2 resonator has been divided into six parts (asymmetrical strip lines) illustrated in Fig. 1b. They are assigned on to four different layers which are connected by via holes. As the odd mode resonant frequency corresponds to the fundamental resonating frequency [7] and according to the normalised voltage wave along the open-ended λg/2 resonator shown in Fig. 2, the symmetrical plane can be treated as a virtual ground plane [8]. As a result, each part of the multilayered resonator has its corresponding actual/virtual ground to form the signal return path, then the basic characteristic of the strip line can be maintained. Fig 2Open in figure viewerPowerPoint Normalised voltage wave along open-ended λg/2 resonator Fig. 3 shows the structure of the proposed LTCC balanced BPF, which is composed of a pair of the proposed 3D λg/2 resonators mentioned above and two pairs of shunt-coupled lines for balanced input and output. The length (L) of the shunt-coupled line and the feeding position (t) of the feed line can be tuned to achieve the desirable external quality (Qe) of differential bandpass response and suppress the common-mode signal [1]. The balanced BPF centred at 2.45GHz has been fabricated on LTCC Ferro A6-M substrate with a dielectric constant of 5.9. The size of this filter is 6.0 × 5.0 × 1.6mm3, corresponding to an electrical size 0.119λg × 0.099λg at 2.45GHz. Fig 3Open in figure viewerPowerPoint Structure of LTCC balanced BPF (actual ground not shown) Fig 4Open in figure viewerPowerPoint Photograph of LTCC balanced BPF mounted on PCB Measured results The proposed LTCC balanced BPF has been mounted on the PCB for measurement, as shown in Fig. 4. The measurement was carried out by an Agilent N5230A network analyser, which can test differential-mode and common-mode S-parameters directly. Simulated and measured results are illustrated in Fig. 5. The proposed balanced BPF has a 3dB bandwidth of 170MHz (7% fractional bandwidth). The minimum insertion loss (|Sdd21|) of the differential-mode passband is 2.4 dB. The common-mode suppression (|Scc21|) is more than 38 dB across the band from 1 to 4 GHz without using a loaded resistor or a stub at the centre of the resonator [2]. Comparisons with other balanced BPFs reported recently are listed in Table 1. Obviously, the proposed filter shows evident size reduction compared with the designs fabricated on the PCB [1, 2]. Remarkably, the proposed distributed-element balanced BPF shows comparable performance to its counterpart based on lumped elements in [3], such as circuit size reduction and common-mode suppression. Fig 5Open in figure viewerPowerPoint Simulated and measured results of LTCC balanced BPF Table 1. Performance comparisons with previous work Ref. f0 (GHz) |Sdd21| (dB) Common-mode suppression (dB) Electrical size (λg × λg at f0) [1] 1.02 − 3.51 > 34.46 0.215 × 0.22 [2] 0.9 − 2 > 35 0.125 × 0.186 [3] 3.42 − 2.5 > 30 0.113 × 0.109 This work 2.45 − 2.4 > 38 0.119 × 0.099 Conclusion In this Letter, a miniaturised LTCC balanced BPF based on transmission line theory is presented. This filter possesses several advantages, such as compact size, good differetial-mode selectivity, high common-mode suppression without using loaded elements, and a simple design procedure. Owing to these merits, the proposed LTCC balanced BPF would be applicable for many wireless communication systems. Acknowledgments The work was supported by the National Natural Science Foundation of China under grants 61101002 and 61271136, and by the Program for New Century Excellent Talents in University (NCET-11-0993), and in part by the Natural Science Foundation of Jiangsu Province, China (grant BK2010272). References 1Wu, C.H., Wang, C.H., Chen, C.H.: 'Stopband-extended balanced bandpass filter using coupled stepped-impedance resonators', IEEE Microw. Wirel. Compon. Lett., 2007, 17, (7), pp. 507– 509 2Shi, J., Xue, Q.:'Dual-band and wide-stopband single-band balanced bandpass filters with high selectivity and common-mode suppression', IEEE Trans. Microw. Theory Tech., 2010, 58, (8), pp. 2204– 2212 3Chen, H.C., Tsai, C.H., Wu, T.L.: 'A compact and embedded balanced bandpass filter with wideband common-mode suppression on wireless SiP', IEEE Trans. Compon. Packag. Technol., 2012, 2, (6), pp. 1030– 1038 4Yang, T., Tamura, M., Itoh, T.: 'Super compact low-temperature co-fired ceramic bandpass filters using the hybrid resonator', IEEE Trans. Microw. Theory Tech., 2010, 58, (11), pp. 2896– 2907 5Chin, K.S., Hung, J.L., Huang, C.W., Fu, J.S., Chen, B.G., Chen, T.J.: 'LTCC dual-band stepped-impedance-stub filter constructed with vertically folded structure', Electron. Lett., 2010, 46, (23), pp. 1554– 1556 6Zhang, X.J., Zhang, H.H., Ma, X.P.: 'Design of compact wideband LTCC filter using pentagonal-shaped SIR', Electron. Lett., 2011, 47, (5), pp. 327– 328 7Bao, Z.H., Chen, J.X., Lim, E.H., Xue, Q.: 'Compact microstrip diplexer with differential outputs', Electron. Lett., 2010, 46, (11), pp. 766– 768 8Tamura, M., Ishizaki, T., Höft, M.: 'Design and analysis of vertical split ring resonator and its application to unbalanced–balanced filter', IEEE Trans. Microw. Theory Tech., 2010, 58, (1), pp. 157– 164 Citing Literature Volume49, Issue5February 2013Pages 354-356 FiguresReferencesRelatedInformation