Common-Mode Filters With Interdigital Fingers for Harmonics Suppression and Lossy Materials for Broadband Suppression

Abstract

Common-mode (CM) noise on differential microstrip lines can be suppressed by PCB-embedded filters. These filters use resonating or broadband structures such that only the field from the CM signal couples to them. Based on a quarter-wavelength resonator, a new PCB filter is designed having an electrical size of only 0.15 λ × 0.065 λ, where λ is the effective wavelength in the CM filter. Its interdigital structure is also capable of suppressing higher order harmonics of the CM signal and can be used for USB 3.0 to mitigate electromagnetic interference. Further, a novel broadband suppression structure is described that uses magnetically lossy material to suppress the CM signal from 4.6 to 20 GHz without strongly affecting the intended differential signal.Index Terms-Broadband filter, common-mode filter, differential signal, quarter-wavelength, narrowband filter.

A Common-Mode Noise Suppression Filter for Gigahertz Differential Signals Based on Substrate Integrated Waveguide Resonators

“…In the same way, a simple CMF using quarter-wavelength open stub resonator is investigated comprehensively in literature [1], and the ultra-wideband common-mode noise rejection can be obtained using cascaded quarter-wavelength resonators with different size. Furthermore, [24] and [25] proposed the CMFs with periodically corrugated reference plane (PCRP) and interdigital fingers for the common-mode noise rejection in highspeed differential signals, respectively. Common-mode noise rejection is realized for balanced bandpass filters in multilayer liquid crystal polymer technology by using folded stepped impedance resonator (SIR) and the proposed 4-cell common-mode rejection structure in [30].…”

Common-Mode Suppression in Broadside Coupled Coplanar Waveguides

“…Past work to suppress common-mode propagation in microstrip or stripline differential transmission lines has included patterned ground structures [1][2][3][4][5], electromagnetic bandgap structures [6][7][8], periodic structures [9], and metamaterial inspired structures such as complementary split-ring resonators [5,[10][11][12][13]. Less effort has been directed toward investigating common-mode suppression in differential coplanar waveguides.…”

Microstrip differential passband filter with high common‐mode suppression using periodically loaded stubs and coupled resonators

“…Varieties of methods have been introduced for suppressing CM noise at GHz ranges. These methods are predominantly based on using defected ground structures (DGS) [1–7], CM resonators [8, 9], hybrid multimode resonator and multilayer transitions [10, 11], balance coupled resonators [12–15], stepped impedance resonator (SIR) [16–19], split ring resonator or other metamaterial structures [20–24] and coupled transmission line and stubs [25–30]. On one hand, the efforts are to widen the stopband of CM while decreasing the implementation costs and miniaturising the structures.…”