The use of RF and digital systems has greatly improved the physical compactness of integrated circuits (ICs) and data handling rates. Given these developments, problems associated with electromagnetic interference (EMI) have grown; these include degradation of signal integrity (SI). To realize high compact and high-speed the systems, the size of components should be reduced, and EMI issues should be solved, therefore, we will discuss the following topics.
Firstly, to realize high physical compactness, studies to reduce the size of RF system components are presented. To miniaturize bandstop filters (BSFs) and bandpass filters (BPFs) for RF system, a vertical split ring resonator (VSRR) is used. A VSRR based on a coupled coplanar waveguide (CCPW) is proposed to reduce the longitudinal length of a VSRR. The proposed design to miniaturize the resonator was fabricated and measured and it is verified that the effective longitudinal length of the proposed VSRR based on CCPW is reduced by 50 % compared with the previous VSRR. Also, BPFs are proposed using mixed electromagnetic coupling paths (MEMCPs) that comprise two coupled VSRRs and present the equivalent circuit models of the coupled VSRRs. BPFs with narrow and wide bandwidths were designed and validated, and we verified that the proposed BPFs have high selectivity with a small circuit footprint.
Secondly, studies to reduce crosstalk noise generated in RF and digital systems due to improved physical compactness are presented. Microstrip signal lines covered with a dielectric layer are used to reduce far-end crosstalk (FEXT) noise from adjacent lines. When minimizing FEXT noise, the permittivity of the dielectric layer should be higher than that of the substrate. When the permittivity is close to that of the substrate, the thickness of the covering dielectric layer is much larger than that of the substrate. We here present a novel means of reducing FEXT noise in microstrip lines covered with a dielectric layer using a rectangular (R)-shaped groove. When an R-shaped groove is created in the covering dielectric layer or substrate of the microstrip lines, FEXT noise is suppressed in the absence of the above conditions.
Finally, we present common-mode (CM) noise mitigation methods; an enhanced broadband CM noise filter is introduced using mushroom-like resonator for high speed RF and digital systems. The unit-cell of the proposed filter is composed of a mushroom-like resonator and transmission lines. We developed a lumped circuit model with transmission lines to enable analysis of the unit-cell using the Bloch–Floquet theorem. We then built a prototype of the proposed CM noise filter and measured its performance.
Also, novel asymmetric coupled lines are proposed to suppress CM noise in bent differential lines. Based on the concept of the relative permittivity of a single microstrip line, the width of the outer line is made smaller than that of the inner line in bent differential lines to reduce the time skew and the other design parameters are adjusted to account for the differential impedance. Based on the proposed method, a minimized structure to suppress CM noise in bent differential lines was designed and fabricated.