Compact Microstrip Lowpass Filter With Ultra-Wide Stopband Using Patch Resonators and Open Stubs

Abstract

A compact microstrip lowpass filter with ultra-wide stopband characteristics and high suppression level is presented. To achieve compact size and wide stopband suppression along with improved impedance matching, symmetrically loaded resonant patches, open stubs and stair shaped high impedance stub are introduced in the filter. The measurement results show good agreement with the simulations. The 3 dB cutoff frequency of the filter is 2.44 GHz. The stopband with attenuation level better than 22 dB is extended from 2.84 GHz to 16 GHz, hence an ultra-wide stopband with 6th harmonic suppression is achieved. The proposed filter has low insertion loss and high return loss in the passband, together with compact size of 0.257λ g × 0.148λ g , where λ g is the guided wavelength at cutoff frequency. The relative stop bandwidth of the proposed design is identified to be 139.5%.

Dual split resonator lowpass filter with ultra‐wide stopband and sharp roll‐off rate

“…1 b . The capacitive element ‘C SRC ’ connected to the high impedance stub with inductance L a 1 [24] in DSR‐1 is expanded into the combination of short‐circuited stub inductances and capacitances. This approach shows the effect of coupling capacitance in the circuit and also agrees with the EM simulation results even the elements within the C SRC in DSR‐1 have capacitive nature.…”

“…Physical parameters and the designed equivalent circuit element values [24] for the single DSR‐2 are given in Table 2. The EM and LC simulation is compared in Fig.…”

Poly-Resonator Lowpass Filter for 26th Order Harmonic Suppression

“…However, due to space restrictions, the highest achievable relative stopband (RSB) is limited. [2][3][4][5][6] displays a number of lowpass filter geometries, some of which are used in conjunction with other active circuits [7][8][9][10]. The bandpass filter spectrum applied in WiMAX [7] and power divider requirements [10] have been put to use the compact lowpass filter circuits working in the same band.…”

Design of a cheap compact low-pass filter with wide stopband

“…In [19], a low cost LPF (using dielectric substrate FR4) was proposed, but the suppression in stopband was unsatisfactory. In [20][21][22], resonator and open-stub was used in LPF to achieve wide stopband, but the circuit size was enhanced.…”