Dual-band filter using composite microstrip/CPW structure

A Dual-Wideband Bandpass Filter Based on E-Shaped Microstrip Sir With Improved Upper-Stopband Performance

“…6(a), transmission zeros TZ 4 and TZ 5 are distributed in the upper-stopband region. Thus, it can be seen that spurious high-frequency bands are suppressed to be below −20 dB for the frequency up to almost 12 GHz, and this is better than other reported dual-wideband filters [14][15][16][17][18]. For comparison, Table 1 summarizes some dual-wideband BPFs performance, where the 20 dB relative upper-stopband bandwidth (RSB) is given by…”

“…The dimensions of the proposed filter are 24 mm × 15 mm if the length of the feed lines is ignored. Compared to the reported filters [14][15][16][17][18] the measured results of this proposed filter give much better upper-stopband performance. Meanwhile, the dualwideband filter shows excellent lower-stopband performance.…”

“…Chin and Yeh [15] utilized a short-circuited stepped-impedance resonator to achieve dual-wideband capability and minimum size. The composite microstrip and CPW structure were proposed in [16] to design dual-wideband filters. Ladder stub resonator (LSR) structure is also proposed to design dual-wideband filter in [17].…”

“…In [18], a dualwideband BPF is achieved by using resonators based on slotted ground structures. Nevertheless, all the dual-wideband BPFs in [14][15][16][17][18] are still embarrassed by the existence of a very narrow upper-stopband, even a poor lower-stopband. Although there are already some on the expansion of the upper-stopband reports [19][20][21], they are basically based on a single passband bandpass filter.…”

Compact dual-band bandpass filter using trisection hairpin resonator for GPS and WLAN applications

“…The measured return losses in both 1.57 and 2.40 GHz bands are higher than 16 dB while the measured insertion losses are about 1 dB in the two passbands. The circuit size of the proposed filter occupies only 26  26 mm ('0.22l g  0.22l g ).Introduction: To meet various wireless communication requirements, dual-band filters have been proposed and exploited extensively as a key circuit block in dual-band wireless communication systems [1][2][3][4][5][6]. In the literature, various types of filters such as the two-section stepped impedance resonator (SIR) and the parallel-coupled microstrip filter have been widely reported.…”