Design of Compact Microstrip Low-Pass Filter With Ultra-Wide Stopband Using Sirs

Abstract

Abstract-A novel low-pass filter (LPF) is designed and fabricated based on stepped-impedance resonator (SIR). Semi-circles are used to reduce the size of the filter. The open-circuited stubs are used in the filter, and its simplified equivalent circuit is also proposed. The measured 3 dB cutoff frequency is 5.2 GHz with no more than 0.3 dB ripple level in the pass-band. From 5.5 to 14 GHz, the investigated LPF has a rejection level better than 20 dB. Measured results show good agreement with simulated ones.

A 2.4 GHZ Bandpass Filter with Harmonic Suppression using Hook-Shaped Resonators

“…Recently, the wireless area networks (WLAN) systems have expanded rapidly, which demands much more applications, thus numerous filters have been researched [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, because of the distributed characteristics of the transmission lines, these filters suffer from spurious passbands, which may reduce rejection levels in the upper stopband.…”

Design of Compact Lowpass Filter With Ultra-Wide Stopband Using Thin Slots

“…Some planar LPFs were reported in [1][2][3][4][5][6]. In [1], the spurious passband of a conventional stepped-impedance LPF can be suppressed by using asymmetrical microstrip step discontinuity.…”

“…To achieve wider stopband, stepped-impedance resonators (SIRs) are usually employed or loaded in the circuit designs. In [5], the compact LPF with ultra-wide stopband is designed with SIRs and open-circuited stubs. A circular hairpin resonator integrated with SIR was proposed in [6].…”

Microstrip Low Pass Filter Designs Using Defected Ground Structure

“…The cut-off frequency of the low-pass filter can be adjusted by setting proper values of the lumped elements of the filter [8][9][10][11][12] can be adjusted as per the requirement. Based on the characteristic impedance Z o , effective dielectric constant  eff and the dielectric constant  r which is 4.4 for the FR-4 substrate, the capacitor and inductance values of the filter elements by the stubs of the high/low impedance transmission lines are calculated.…”