Return loss reduction of the metamaterial CRLH antenna using short-ended reactive stubs

Compact and wideband bandpass filters with analysis of the CRLH-TL characteristics based on stepped impedance resonator

“…Therefore, wideband (WB) devices like filters in C-band (4-8 GHz) play a significant role in modern wireless local area networks (WLANs) and Bluetooth transceivers [1]. Since the federal communication commission (FCC) authorized the unlicensed use of ultra-WB (UWB) in 2002 [2], several surveys have been performed to develop wideband BPFs with different methods and structures [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Researches have proposed many different topologies for designing UWB filters such as stub-loaded resonators [3], cascaded ring resonators filters that suffer from physical size but have good frequency response [4][5][6][7][8], UWB BPF with a notched band that suffers from poor skirt selectivity at both passband edges [7], TETRA band filters [11] and stepped-impedance slotline resonators [12].…”

“…Recently, electromagnetic metamaterials have been used to design high performance filters [13][14][15][16][17][18][19][20]. The resonant-types of metamaterial structures that consist of split ring resonators (SRRs) and complementary split ring resonators (CSRRs) have been more used for the design of microwave filters [16,17].…”

“…The resonant-types of metamaterial structures that consist of split ring resonators (SRRs) and complementary split ring resonators (CSRRs) have been more used for the design of microwave filters [16,17]. Left-handed transmission lines (LH-TLs) with representing an abrupt transition pole at the lower or upper edge of the passband can improve the sharp attenuations near the passband and increase the bandwidth simultaneously [17][18][19][20].…”

“…The review of these articles [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] summarizes and mentions three main advantages in design of a filter. 1) Dimension: the size of the filter should be small enough so that the proposed filter is able to operate as a compact WB filter.…”

“…Hence, it has been suggested to utilize composite right/left handed transmission line (CRLH-TL) and highlow-high stepped-impedance resonator (SIR). It is worth to note that one of the specific features of the CRLH-TL is reduction of the loss [19,20].…”