In this article, a common-mode noise filter with a wideband suppressing and dual-band high absorbing common mode filter, which is called absorptive common-mode filter, is proposed. The filter is constructed by a reflective-type common-mode filter, a phase matching, and an absorber. It is composed of three layers with 14.98 mm × 9.585 mm. The broadband common-mode noise suppression can be achieved by positioning multiple transmission zeros. By using dual-band phase matching and an absorber, the dual-band absorption can be realized. The frequencies are in the range of 2.4 to 2.5 GHz and 5.17 to 5.33 GHz, respectively. The positioning of transmission zeros and absorption points at those frequencies leads to a high absorption efficiency. The simulation result shows that the common-mode suppression, which is below −10 dB, is from 2 to 11 GHz. The fractional bandwidth is 138%. The differential-mode signal keeps integrity in the range from DC to 12 GHz. The absorption efficiencies in the two frequency sections are 97% and 96%, respectively. The experiment results show only slight differences from the simulation results.

In this article, we present a novel equivalent circuit model for a dual-band unified absorptive common-mode filter (A-CMF). While existing single-band A-CMFs effectively address electromagnetic interference (EMI) issues in the 2.4–2.48 GHz frequency range, they fall short in covering the 5.17–5.33 GHz band. This study designs a dual-band A-CMF that covers both frequency bands, suppressing common-mode noise while maintaining a compact size suitable for modern electronic devices. The new design includes a wideband suppression reflective common-mode filter and a dual-band common-mode noise absorption circuit. By adjusting the electrical length of transmission lines, this method can rapidly adapt to various manufacturing processes and achieve efficient absorption within the 2.4–2.48 GHz and 5.17–5.33 GHz frequency ranges. Finally, the proposed equivalent circuit is validated using circuit-level and full-wave simulations, as well as a fabricated test sample. The experimental results show that the equivalent circuit model aligns well with both simulation and measurement results, significantly reducing the size of the matching stage and the overall structure.

In the PCB process, overcoming common-mode noise radiation is critical. In past years, most studies have focused on a common-mode noise filter (CMNF) that can solve electromagnetic interference in high-speed digital systems by blocking and absorbing common-mode noise radiation. Unfortunately, connecting with any reflective common-mode noise filter (R-CMNF) and reducing the area of an absorptive common-mode noise filter (A-CMNF) are the most troublesome tasks in the PCB process. A novel equivalent circuit is proposed in this research to minimize the complexity of the design and improve accuracy. Detailed analyses of this proposed approach are entirely depicted in this article. The experiment result shows that 9% of fractional bandwidth centered at 2.25 Hz can achieve at least 90% absorption efficiency. With our proposed method, the area of A-CMNF is smaller than in state-of-the-art research.

Four types of CSRR DGS RCMF (Complementary Split Ring Resonator Defected Ground Structure Reflective Common-Mode Filter) simulations are presented. Their equivalent circuits are also presented. Their performance results are also shown and analyzed. ANSYS HFSS is used to verify these performances. The dimension of the proposed filters is 11.0 mm x 11.0 mm. The best result is achieved by D _ CSRR DGS RCMF with the resonance frequency of the transmission zero at 2.44 GHz, the transmission zero depth is -26.0 dB, the -5 dB bandwidth is 1.8 GHz, and the -10 dB bandwidth is 500 MHz.

A Single-band Series Absorptive Common Mode Noise Filter (ACMF) is proposed. The ACMF is embedded in a four-layer printed circuit board (PCB) and consists of three parts: a Reflective Common Mode Noise Filter (RCMF), a matching circuit, and an absorber. The RCMF is designed using mushroom-type resonators. The matching circuit is designed using meander lines to reduce the size of the filter dimensions. The absorber of the Common Mode noise (CM) is a series resistor. The designed operating frequency is 2.45 GHz. The simulation results are as follows: the insertion loss of CM (Scc21) is -22.49 dB at the frequency of 2.61 GHz, the return loss of CM (Scc21) is -18.62 dB at the frequency of 2.5 GHz, while the integrity of the Differential Mode signals (DM) can be maintained with a very small insertion loss (Sdd21) of -1 dB at the frequency range of 0-8 GHz, and the achieved Absorption Efficiency (AE) is 93% at the frequency of 2.54 GHz. The proposed ACMF dimension is 10.3 x4.6 mm. The fractional bandwidth is 19%. The measurement results of the fabricated ACMF do not deviate significantly the simulation results. They are as follows: Scc21 is -17.87 dB at the frequency of 2.31 GHz, Scc11 is -20.87 dB at the frequency of 2.38 GHz, Sdd21 is -2.8 dB at the frequency range of 0–8 GHz, the Absorption Efficiency is 97% at the frequency of 2.32 GHz, and the fractional bandwidth is 17%. Therefore, the results of the ACMF design carried out by simulation can be implemented into a fabricated ACMF with measurement results similar to the calculation results in the design.