Experimentally validated of defected microstrip structure to realize band stop filter based on capacitively loaded loop resonators

Millimeter‐wave substrate integrated waveguide bandpass filters based on stepped‐impedance E ‐shaped defected ground structure s

“…Recent years, the defected ground structure (DGS) 1 has attracted more and more research interest due to the wide applications at microwave, millimeter-wave, and terahertz bands. For example, it can be used to improve the electromagnetic wave manipulating performances of passive and active microwave/millimeter-wave components, including the high-performance antenna, [2][3][4][5][6][7][8][9] filter, [10][11][12][13][14][15][16][17][18][19][20][21][22] transmission line, 23 power division network, 24 wireless power transfer, 25 oscillator, 26 and low noise amplifier. 27 Specifically, for antenna application, circular dumbbell-shaped DGS is used to contribute additional resonance and miniaturize the antenna size, 2 full-length resonant-type and asymmetric DGS can reduce the cross-polarized radiation, 3,4,9 Fractal DGS can reduce the mutual coupling of coplanar spaced microstrip antenna elements 5 and also generate circularly polarized radiation, 6 S-shaped DGS is used to achieve the ultra-wideband antenna with multiple band-rejection properties, 7 and Г-shaped DGS can be used to improve the impedance matching property for the magnetoelectric dipole antenna.…”

“…12 The face-to-face Eshaped and C-shaped DGSs inserted into the, respectively, regular SIW and half-mode SIW (HMSIW) can achieve compact wideband bandpass filter. 13,14 The closed loop DGS can contribute to additional transmission zero for chip-scale bandpass filter. 16 The asymmetric Pi-shaped Koch fractal DGS and triple isosceles U-shaped DGS are used to design microstrip low-pass filter with additional transmission zeros.…”

“…12 Moreover, when the face-to-face E-shaped and C-shaped DGSs are integrated into the bottom and top layer of SIW and HMSIW, respectively, to achieve the bandpass feature above the cut-off frequency, the frequency selectivity at both low-frequency and highfrequency sides should be improved strongly. 13,14 After theoretical analysis on those previously reported DGSinspired bandpass filters, it is found the key problem is the week coupling effect within DGS structures. Most importantly, the previously reported works are hard to achieve dual-band property, especially at millimeter wave frequency band.…”

“…For example, the back‐to‐back E‐shaped DGS is used to achieve evanescent‐mode wave propagation below the cut‐off frequency of regular substrate integrated waveguide (SIW) and, therefore, realize miniaturized bandpass filter 12 . The face‐to‐face E‐shaped and C‐shaped DGSs inserted into the, respectively, regular SIW and half‐mode SIW (HMSIW) can achieve compact wideband bandpass filter 13,14 . The closed loop DGS can contribute to additional transmission zero for chip‐scale bandpass filter 16 .…”

“…Specifically, when the back‐to‐back E‐shaped DGS is used to contribute to the bandpass feature below the cut‐off frequency of a regular rectangular waveguide or SIW, the effective electric size of DGS is large, making it difficult to achieve multistage bandpass filter with wide passband and good frequency selectivity 12 . Moreover, when the face‐to‐face E‐shaped and C‐shaped DGSs are integrated into the bottom and top layer of SIW and HMSIW, respectively, to achieve the bandpass feature above the cut‐off frequency, the frequency selectivity at both low‐frequency and high‐frequency sides should be improved strongly 13,14 . After theoretical analysis on those previously reported DGS‐inspired bandpass filters, it is found the key problem is the week coupling effect within DGS structures.…”