Summary
International Symposium on Antennas and Propagation
2009
Session Number:3B4
Session:
Number:3B4-4
Microstrip BPF using SIRs with Wide and Deep Harmonics Suppression Band
S. Theerawisitpong, T. Suzuki, N. Morita, Y. Utsumi,
pp.899-902
Publication Date:2009/10/21
Online ISSN:2188-5079
Summary:
Microstrip bandpass filters are recently fashionable with various well known features, including low cost, compactness, light weight, easy fabrication, and affordability in active circuit extension. In practice, it needs to be designed with basic characteristics of low passband attenuation, high selectivity, and harmonics suppression. In particular, harmonics suppression characteristic is significantly required for wireless communication systems. Although several harmonics suppression techniques [1]-[3] were presented in recent years, wide and deep harmonics suppression band should be more enhanced with minimized step filters. In our research, 2-step and 3-step bandpass filters were designed and fabricated. The centre frequency was 1950 GHz for WCDMA-FDD up-link band with bandwidth of 60 MHz based on IMT-2000 standard. In measurement, the harmonics suppression band was greater than 30 dB from 2.3 to 9.4 GHz for a 2-step filter, and greater than 40 dB from 2.3 to 9.1 GHz for a 3-step filter. The designed folded and straight stepped impedance resonators (SIRs) used for this were designed its physical characteristic based on off-band design while passband design charts were also newly plotted based on various 3-dB bandwidths (maximally flat) [4]. Those passband design charts were used to design any step filter and any bandwidth for any Tchebycheff or maximally flat. In addition, the high selectivity of two transmission zeros on passband was obtained by two open-ended stubs [4]. The harmonics suppression technique was proposed and described in here with even-mode interruption technique for the 2-step and 3-step filters, accordingly, 3-step filter size reduction by using a conventional quarter-wavelength SIR [5]. In the content, designed resonators and filters are described in Sec. 2. The prototype filters and measurement results are shown in Sec. 3 and conclusion is given in Sec. 4.