Common-mode Suppression Level Research Articles

Balanced Filtering Power Divider based on Odd-mode Hybrid Microstrip and Slotline Spoof Surface Plasmon Polaritons

In this paper, an ultra-wideband balanced filtering power divider (B-FPD) with high common mode (CM) suppression level is proposed. The B-FPD is designed based on the odd mode spoof surface plasmon polaritons (SSPPs), which are constructed by the hybrid folded microstrip and slotline (HFMS) structure. Firstly, the dispersion characteristic and electric field distribution of the HFMS SSPP unit cell are investigated, which can decrease the upper cut-off frequency for size reduction of nearly 50%. Next, an equal balanced power divider with low cut-off frequency is proposed based on the microstrip-to-slotline transition structure and slotline Y-junction. Then, the balanced power divider is used to excite the odd mode of HFMS SSPP structure. An equal B-FPD with center frequency of 4.0 GHz is implemented, and the 3-dB bandwidth covers 0.9 to 7.0 GHz. Finally, the B-FPD with advantages of high CM suppression level and compact size is fabricated and measured.

A Low-Cost SISL Differentially Fed Dual-Polarized Stacked Patch Antenna With Enhanced Common-Mode Suppression Using Characteristic Mode Analysis

A wideband differentially fed dual-polarized stacked patch antenna with high common-mode (CM) suppression is proposed in this article using the characteristic mode analysis (CMA) and the substrate integrated suspended line (SISL) technology. Based on the CMA, orthogonal slots are loaded within the stacked patch to enhance the directivity of the second-order degenerate modes and reallocate the resonating frequency of the fundamental degenerate modes. A crossed dipole is introduced within the driven patch to ensure polarization uniformity between the two paired degeneracies. The CM suppression level ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{\mathrm {CC}}11$ </tex-math></inline-formula> ) is enhanced from–10 to–1.30 dB within the frequency range of 4.0–7.0 GHz by embedding circular slots embedded within the stacked patch and controlling the slot radius. Measured results demonstrate a–10 dB differential impedance bandwidth of 28.4% (4.62–6.18 GHz) and high isolation of better than–39.5 dB between the differential ports. The antenna depicts stable measured radiation patterns with low cross-polarization (<–30 dB). The measured average antenna gain and efficiency are 9.55 dBi and 85.5% within the DM passband. In addition, a high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{\mathrm {CC}}11$ </tex-math></inline-formula> better than–1.05 dB is measured within the desired DM band.

Balanced Dual-Band HTS BPF With Controllable Frequency Ratio and Transmission Zeros Using Mixed Cross-Coupling

In this brief, a fourth-order balanced dual-band high temperature superconducting (HTS) bandpass filter (BPF) is presented based on modified stub-loaded resonators (SLRs). Firstly, the differential mode (DM) and common mode (CM) resonant characteristics of the modified SLRs are analyzed. Under DM operation, two types of mixed cross-coupling topologies are constructed by placing the spiral modified SLRs and their DM equivalent structures in an appropriate way. Then, a dual-band response with controllable center frequencies, bandwidths, and transmission zeros (TZs) is achieved. Under CM operation, an effective CM suppression circuit is proposed for improving the in-band CM suppression level. Finally, for verification, a fourth-order balanced dual-band HTS BPF with center frequencies of 3.494/4.797 GHz and insertion loss of 0.26/0.21 dB is designed and fabricated on MgO substrate with double-sided YBCO thin films. The measured results agree well with the simulated ones, and the BPF shows the attractive features of low insertion loss and good out-of-band rejection.

High-Order Balanced Dual-Band HTS BPF With Flexible Frequency Ratio and Sharp Rejection Skirts

In this article, a new class of high-order balanced dual-band high-temperature superconducting (HTS) bandpass filter (BPF) based on modified multimode stub-loaded resonators (SLRs) is presented. First, a detailed theoretical analysis of the multimode SLRs is provided to obtain insight into their frequency response characteristics under the differential-mode (DM) and common-mode (CM) operations. Specifically, the SLRs under the DM operation are designed to generate their second and third resonant modes in the two specified passbands, and they are sequentially cascaded by alternate <inline-formula> <tex-math notation="LaTeX">$J$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> inverters for sharp rejection skirts. Following that, the working mechanism of the CM rejection of the resonator is investigated for achieving good CM suppression performance for this filter. Finally, for experimental validation, an eighth-order prototype filter is designed and fabricated on the MgO substrate with double-sided YBa2Cu3Oy (YBCO) thin films. Good agreement between measured and simulated results is obtained, and the filter is at the same time with low insertion loss, flexible frequency ratio, sharp rejection skirts, and good CM suppression level.

High-Performance Common- and Differential-Mode Reflectionless Balanced Band-Pass Filter Using Coupled Ring Resonator

In this brief, for the first time, we propose common-mode (CM) and differential-mode (DM) reflectionless balanced bandpass filters (BPFs) using half-wavelength ring resonator. By loading absorptive stubs at input/output ports and the ends of the coupled-lines (CLs), the BPFs can realize input-/two-port wideband CM and DM reflectionless performance from dc, as well as wide filtering band and all-stop CM suppression. As for the input-reflectionless type, two extra transmission zeros (TZs) can be obtained by loading <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda /2$ </tex-math></inline-formula> stubs between the CLs. Besides, the impedances of the CLs can determine the CM suppression level, and the absorption performance can be independently adjusted. The operational foundations and explicit equations are discussed and derived. Good agreements between the simulated and measured results verify the design theory.

Balanced-to-Single-Ended Four-Way Out-of-Phase Power Divider and Its Application to Broadband Balanced Quasi-Yagi Antenna Array

A broadband balanced-to-single-ended (BTSE) four- way power divider (PD) with out-of-phase is designed in this letter. The proposed four-way PD composed of three-series T-junction PDs, a balanced U-type microstrip-slotline transition structure, and multiple cross-junction microstrip-slotline transitions. The series T-junction PD achieves equal amplitude and out-of-phase power distribution at the output ports over a wide frequency band. Meanwhile, the balanced U-type structure as the feed of the BTSE PD can realize a great broadband common-mode (CM) rejection without affecting the differential-mode (DM) responses. In addition, the proposed BTSE PD is employed with four quasi-Yagi antennas to realize a balanced quasi-Yagi antenna array. The proposed antenna array keeps the merits of wide DM transmission and high CM suppression level and achieves low cross-polarization level and high gain in the endfire direction. Finally, a prototype antenna array is fabricated and measured, and the experimental results show that it exhibits 10 dB return loss bandwidth of 5.7-8.9 GHz, peak gain of 12.5 dBi, and maximum cross-polarization levels of -25.6/-34.6 dB in E-/H-planes at 5.8 GHz, respectively.

A High-Performance Common-Mode Noise Absorption Circuit Based on Phase Modification Technique

In this article, a high-performance common-mode noise absorption circuit (CMNAC) is proposed for solving electromagnetic interference (EMI) or radio-frequency interference (RFI) problems in high-speed differential digital systems. Instead of reflecting common-mode noises by conventional common-mode filters (CMFs), the common-mode noises can be absorbed in the proposed circuit. In addition, the phase modification technique is utilized to enhance the common-mode noise absorption rate and the differential-mode eye diagram in this CMNAC. In the common-mode half circuit (CMHC), the phase inversion of the subnetwork adds a destructive combination of the stopband energy, resulting in higher stopband attenuation. In the differential-mode half circuit (DMHC), the phase linearization leads to flat group delay, reducing the distortion in high-speed digital signal transmission in the lumped circuit. Using a standard integrated passive device (IPD) process, this CMNAC is implemented for the demonstration. The circuit occupies an area of only 1.138 mm $\times0.822$ mm. From the measured results, the proposed circuit exhibits the common-mode suppression level larger than 15 dB from 4 to 20 GHz and the absorption rate over 90% from 3.8 to 17.4 GHz with a fractional bandwidth 128%. In addition, the measured eye diagram shows that the proposed circuit can support high-speed transmission up to 10 Gb/s.

Design of Compact Balanced-to-Balanced Diplexer Using Dual-Mode CRLH Resonator for RFID and 5G Applications

A compact balanced-to-balanced diplexer based on composite right/left-handed (CRLH) resonator is presented in this paper. The proposed compact CRLH resonator is used to design two balanced channels, which are connected by T-junction to construct the balanced-to-balanced diplexer. Under differential-mode (DM) operation, the proposed CRLH resonator can provide two adjacent DM resonant modes to produce one passband of the balanced-to-balanced diplexer. Under common-mode (CM) operation, the CRLH resonator also generate two CM resonant modes, whose locations are far away from DM resonant modes, resulting in a perfect CM suppression level. To verify the design methodology, a compact balanced-to-balanced diplexer operated at 2.45 GHz and 3.47 GHz is designed and fabricated for multi-service system integrated with microwave RFID and 5G applications. The proposed balanced-to-balanced diplexer shows high CM suppression level and channel-to-channel isolation performance. The measured results are agree well with the simulated ones.

Compact and Wideband Differentially Fed Dual-Polarized Antenna With High Common-Mode Suppression

A compact and wideband differentially fed dual-polarized antenna with high common-mode suppression is investigated in this paper. A square patch with crossed-slot consisting of four slant funnel-shaped slots is used as the radiator, generating slant ±45° linear polarizations. Two orthogonal placed baluns, each connected with two open-end stubs, act as the feeding network. Under differential-mode (DM) excitation, the resonating mode of the square patch and quarter-wavelength mode of the funnel-shaped slots can be excited at low and high frequency band, respectively, which enhances the operation bandwidth of the designed antenna. By using differential excitation, a high level of common-mode (CM) suppression can be realized. To verify the design, the prototype of the designed antenna and an antenna array consisting of four elements are fabricated and measured. The experimental results indicate that a DM reflection coefficient better than -15 dB and a CM suppression level better than 1 dB are achieved within a wide impedance bandwidth of 55.3% (1.66 to 2.93 GHz). A high isolation and a stable radiation pattern can be observed within the operating band. Besides, the proposed antenna maintains a small aperture size of 0.36λ 0 × 0.36λ 0 , where λ 0 is the free-space wavelength at the center frequency of operation band.

A new microstrip coupling system for realization of a differential dual-band bandpass filter

In this paper, a new Differential Dual-Band Wide-Bandpass Filter (DDWBF) using a new coupling system is presented. The adjustable coupling system composed of Two Coupled U-Shaped Structures (TCUSs) which create and control two initial passbands. Four TCUSs are then placed in four ports and connected through a defected fractal-based low impedance transmission line. Third order of Sierpinski fractal is applied on the transmission line to improve the out of band rejection of the differential mode along with common mode suppression. An analytical analysis is also presented to calculate the transmission zeros and poles of the DDWBF which verifies the authenticity of the design procedure. A prototype of the filter has been fabricated and tested which shows a very good agreement with the predicted results. According to the measured results, two wide passbands with fractional bandwidths of 45% and 13.5% at central frequencies of 4.32 and 8.61 GHz, respectively, have been achieved. The differential mode return loss is higher than 15 dB in both bands and the common mode suppression level is better than 14.85 dB.

Analysis of Coupled Cross-Shaped Resonator and Its Application to Differential Bandpass Filters Design

Analysis and applications of coupled cross-shaped resonator (CCSR) for fixed and fully reconfigurable differential bandpass filters (BPFs) design are focused in this paper. CCSRs with open and capacitive terminations are presented and discussed. One differential BPF named Filter I centered at 4.5 GHz with fixed differential-mode (DM) and common-mode (CM) responses using CCSR with open termination; and another one named Filter II using capacitive termination and loaded lumped capacitors offers fully reconfigurable DM center frequency, bandwidth and intuitive CM suppression control are proposed with very compact size (0.01λ0 2 ). Such that ultra-wide DM center frequency tuning range of 82% fractional tuning range with both constant absolute bandwidth (ABW) and constant fractional bandwidth (FBW), easy control of CM suppression level and rejected range are achieved, respectively. Their experimental characterizations are in good agreement with theoretical analysis validating a simple approach of fixed and fully reconfigurable differential BPFs design.

Microstrip Balanced Bandpass Filter With Compact Size, Extended-Stopband and Common-Mode Noise Suppression

In this letter, a novel balanced bandpass filter (BPF) with its simple design procedure are proposed. The filter is based on a novel balanced resonator which is composed by two closed-loop transmission lines of characteristic impedance ZCL = 50 Ω and electrical length of 53.13° and one transmission line of characteristic impedance ZHI = 100 Ω and electrical length of 53.13°. Also the differential-mode (DM) and common-mode (CM) equivalent circuits of the resonator are given for design purposes. A prototype with measured DM passband at 1.029 GHz and fractional bandwidth (FBW) of 9.833% is presented. The prototype exhibits compact size (0.149 λg × 0.228 λg), DM stopband with a 40 dB suppression level broadened up to 5.633 f0d and CM suppression level better than -40 dB from 0 to over 3.7 f0d and better than -30 dB from 0 to 5.91 f0d.

Design of Balanced Dual-Band Bandpass Filters Using Asymmetrical Coupled Lines

In this paper, we present balanced dual-band bandpass filters (BPFs) using asymmetrical coupled lines. The proposed dual-band BPF has an enhanced common-mode suppression level because the proposed asymmetrical coupled line inherently has the bandstop characteristic on common-mode signals without either additional stubs or lumped elements. The proposed asymmetrical coupled line has dual-band performance on differential-mode signals. The common- and differential-mode equivalent circuits of the proposed filter are given and analyzed to demonstrate the common- and differential-mode responses. Two passbands of the differential-mode response are designed based on a lumped equivalent circuit of the proposed filter. Therefore, two bandwidths can be easily controlled. Two second-order balanced dual-band BPFs are designed and tested at center frequencies of 2.4 and 3.57 GHz with fractional bandwidths (FBWs) of 7.5% and 5% and with FBWs of 7.5% and 6.16%, respectively.

Dual-Band and Wide-Stopband Single-Band Balanced Bandpass Filters With High Selectivity and Common-Mode Suppression

Novel dual-band and wide-stopband single-band balanced bandpass filters with high selectivity and common-mode suppression are presented in this paper. Stepped-impedance resonators (SIRs) are usually used for designing dual-band bandpass filters; however, they have a strong common-mode response when designing a balanced filter. To suppress the common-mode signal, a half-wavelength SIR loaded by a capacitor or a resistor has been introduced and theoretically analyzed. It is found that the capacitor can minimize the common-mode external quality factor, and the resistor can reduce the common-mode unloaded quality factor. With the use of this property, the common-mode response can be suppressed, whereas the differential-mode response is almost unaffected. This property can be easily verified by comparing the results of the balanced bandpass filters with and without loaded elements. To demonstrate the design idea, one balanced dual-band bandpass filter operating at 2.4 and 5 GHz and another balanced single-band bandpass filter with a wide stopband are designed. It was found that the common-mode suppression level of both filters can be greatly improved, and high selectivity is obtained by giving two differential-mode coupling paths.

Novel Balanced Dual-Band Bandpass Filter Using Coupled Stepped-Impedance Resonators

A novel balanced dual-band bandpass filter, using coupled stepped-impedance resonators (SIRs), is proposed in this letter. The differential- and common-mode equivalent half circuits are given. By properly designing the resonators, associated with the filter composed of eight SIRs, dual-band differential-mode bandpass response can be obtained. To improve the common-mode suppression level, two open stubs with different lengths are added to the connection point of two resonators. A prototype balanced filter operating at 2.4 and 5 GHz has been realized to validate the proposed concept and theory.