Stepped Impedance Research Articles

Planar dual-band bandpass filter with regular harmonic suppression

Abstract This paper presents a dual-band bandpass filter with regular harmonic suppression. The proposed third-order filter consists of two microstrip stepped impedance resonators and single substrate integrated waveguide resonator. The mismatches in their higher order resonant frequencies are utilized to suppress the regular harmonics. The passbands are centered at f1 = 2.4 GHz and f2 = 3.5 GHz with fractional bandwidths of 5% and 7.5%, respectively. The measured midband insertion and return losses are better than 2.55 and 14.5 dB for the first, whereas for the second band, they are better than 1.95 and 14 dB. The filter offers at least 33 dB suppression of first three higher order regular harmonics of f1 and f2.

Meander Line Loaded 2- Port Stepped Impedance Feed Slotted MIMO Antenna For C and Lower X-Band Communication

Meander Line Loaded 2- Port Stepped Impedance Feed Slotted MIMO Antenna For C and Lower X-Band Communication

A microstrip bandpass filter using coupled lines loaded by open stubs

A compact simple structure bandpass filter based on terminated three coupled line structures with high selectivity is introduced through odd and even-mode analysis. The proposed filter consists of three coupled lines loaded by open and short circuit stubs. The parallel-coupled lines structure is used to obtain high selectivity with transmission zeros near the passband. Meanwhile, simultaneously tuning on bandwidth and center frequency are introduced by coupled line. One type of bandpass filter based on terminated coupled line structure is theoretically analyzed, simulated, and measured. The stepped impedance structures at the input and output ports have been used to improve the attenuation level at the stopband region and create the multiple attenuation poles. The center frequency of 1.3 GHz, the fractional bandwidth (FBW) of about 65%, the low insertion loss of 0.25 dB, and the high return loss of 30 dB are obtained. Also, a flat group delay lower than 1.4 ns is achieved. Experimental and simulated results are presented, which are in good agreement.

Ultrawideband Flexible and Intensity-Tunable Metamaterial Absorber Based on Lossy Stepped Impedance Resonator

Ultrawideband Flexible and Intensity-Tunable Metamaterial Absorber Based on Lossy Stepped Impedance Resonator

A dongle-sized bandwidth-reconfigurable filtenna for UWB/5G-n77 band applications

ABSTRACT This paper presents a frequency reconfigurable filtenna for efficiently switching between ultra-wideband (UWB) and 5G-n77 band. The filter section with the UWB state of operation is realised by a stepped impedance open stub loaded at the middle of a stepped impedance resonator. Switching to 5G-n77 band is accomplished by appending two open-circuited uniform impedance stubs to the UWB filter section through PIN diodes. The antenna section is coplanar waveguide (CPW) fed and is based on a quasi-self-complementary design with a half- hexagonal-shaped radiator. The microstrip to CPW transition is realised by connecting the ground planes through vias. The overall size of the filtering antenna is 18.5 mm × 57 mm. The filtering antenna has stable radiation patterns with good agreement between simulated and measured results. The peak gain in 5G-n77 band and UWB band is 4 dBi.

Design of dual-band filtering patch antenna based on SIR multimode resonator

Abstract With the development of the communication field, more and more communication devices need multiple single-frequency antennas to work simultaneously. However, using multiple single-frequency antennas results in larger sizes. The miniaturized and dual-band communication system has become a new development trend. This paper designs a dual-band filtering patch antenna based on a multimode resonator, which is cascaded. The filter resonator part adopts step impedance resonance for branch shunt design, which can flexibly control the center frequency of two frequency bands. The filtering antenna utilizes a dual-layer substrate structure and achieves an integrated design through coupling probe feeding. This reduces the horizontal dimensions and improves miniaturization. Multiple radiation nulls are introduced outside the two-passband, and roll-off characteristics are evident. In addition, this design realizes high selectivity in the operating band. The antenna has large gains of 1.71 dBi and 6.25 dBi. It has good filtering and radiation characteristics.

Quad Band Filter with Controllable Transmission Zeros using Vertical and Diagonal Coupling of Triple and Dual Step Impedance Resonators

Quad Band Filter with Controllable Transmission Zeros using Vertical and Diagonal Coupling of Triple and Dual Step Impedance Resonators

Highly selective tri-wideband bandpass filter with adjustable passbands for high-performance space-based assets applications

A straightforward approach to designing a tri-wideband bandpass filter employing an E-shaped stepped impedance resonator loaded by an open-circuited tri-section stepped impedance stub (OSLTSIR) is explored in this paper. Upon analysis, it is ascertained that this resonator offers a distinct advantage by providing increased degrees of freedom for adjusting resonant frequencies, and the strength to generate transmission zeros at lower/upper stopbands. Capitalizing on these attributes, a tri-band bandpass filter is examined by combining this OSLTSIR with a half-wavelength resonator. The incorporation between the OSLTSIRs gives rise to creating a dual-wide band, while the introduced λ/2 resonators led to split the second passband into two, yielding in tri-band performance. The resultant filter operates at 8.25 GHz, 11.1 GHz, and 15.35 GHz with wide fractional bandwidths of 25.57 %, 18.45 %, and 24.6 %, respectively. Resonant frequencies and bandwidth can be controlled with substantial flexibility. The Experimental assessments confirm the existence of seven transmission zeros, showcasing high selectivity and good isolation. Besides, the fabricated structure maintains a compact size of (6.2 × 8.4) mm, about 0.12 λg2. The close agreement between the simulated and measured findings verifies its applicability for space-based asset applications.

A compact dual‐band bandpass filter based on coupled stub‐loaded square ring resonators by using transversal signal‐interaction concepts

AbstractIn this paper, a novel dual‐band wideband bandpass filter (BPF) based on transversal signal‐interaction concepts with a wide upper stopband is proposed and investigated. The designed specification of two passbands can be managed and satisfied based on the independent controllable fractional bandwidth of the two passbands and the centered frequencies. The centered frequencies of dual‐band BPF are, respectively, 0.79 GHz (ƒ1) and 1.24 GHz (ƒ2) with 3 dB fraction bandwidths of 26.54% and 11.3%. Two transmission paths consisting of coupled stub‐loaded square ring resonators and anti‐coupled shorted lines are used to realize signal cancellation of multiple transmission path signal transmission from Port 1 to Port 2. Eleven transmission zeros (TZs) modify harmonic suppression up to 10 ƒ1 with stopband rejection higher than 15 dB. Butterworth lumped notch network and step impedance resonator (SIR) are also utilized to improve the selectivity and harmonic suppression. A compact filter with a circuit size of 0.08λg × 0.08λg is implemented and tested. Good agreement between simulation and measured results verifies the reliability of the designing scheme.

Highly miniaturized dual-band bandpass filter with wide bandwidth and large center frequency ratio

The design of a miniaturized dual-band bandpass filter featuring a broad bandwidth and a high center frequency ratio is demonstrated in this article. A novel symmetrically loaded shunt coupled line with dual stepped impedance stubs has been investigated for the first time and it is utilized to realize a dual-band bandpass filter with seven transmission zeros. The transmission zeros frequencies of the filter response have been theoretically verified using even-odd mode analysis. For experimental validation purposes, a dual-band filter with a center frequency ratio of 4.06 covering 5G applications is implemented using Rogers RT/duroid 5870 substrate and tested. The tested filter has wide 3 dB fractional bandwidths of 53.8% and 17.9% in the first and second passbands, respectively, and has a compact topology of 0.20 × 0.09 λg 2. The full-wave simulated and tested magnitude and group delay responses of the proposed filter are in good congruence.

Design of a miniaturized multi resonance resonator based highly selective dual wideband bandpass filter

This paper presents the design of a highly selective dual-wideband bandpass filter. The filter is designed by using multi-resonance resonator consisting of two stub-loaded step impedance resonators separated by an inter-digital capacitor. The inter-digital capacitor generates capacitive coupling, resulting in multiple resonating modes. The proposed filter generates two passband frequencies centered at 5.75 GHz and 11.5 GHz. Experimental measurements show that the maximum insertion loss in the passbands is 0.83 dB and 0.87 dB, while the reflection losses are better than 10.8 dB and 12.6 dB, respectively. The resonant frequencies can be adjusted by changing the length of the loaded stubs. The proposed dual-wideband bandpass filter offers improved out-of-band rejection and selectivity by generating seven transmission poles and seven transmission zeros around both passbands. The experimental results confirm the effectiveness of the proposed filter. Furthermore, the filter has a compact size of (0.61×0.66)λg, making it suitable for integration into microwave sensing devices.

Dual-Band Matching Networks Using a Combination of Microstrip Lines and Active Switching Components

Active switching components are employed to propose a novel compact dual-band matching network (MN) with an adapted frequency in this paper. The design method involves the integration of active switching devices, stepped impedance resonator (SIR), and microstrip transmission line into the frequency response of a dual-band MNs. The PIN diode is employed as an active switching device in the proposed structure to increase the bandwidth of the MNs and attain the desired frequency. The dual-band MNs that are being proposed are fabricated and designed on the Rogers RO4350B substrate for use in Wireless Local Area Networks (WLANs). The simulation results demonstrate a high degree of congruence with the measurements. The maximal insertion losses and return losses in the first band are -1.3 and -24 dB, respectively. In the second band, they are -2.2 and -20.69 dB. The primary benefits of the proposed dual-band MNs are their high attenuation between two passbands, frequency matching capability, suitable return loss, and low insertion loss.

Performance analysis of optimum Chebyshev filters at microwave frequencies

The paper suggests that optimum Chebyshev filters present an excellent choice for microwave filter design, as this approximation offers minimum return loss in the half-power passband, provides a maximum cutoff slope, and maintains low sensitivity in the passband. A comparative analysis is conducted with the chained-function filters to demonstrate the efficacy of this approximation, since chained-function filters also utilize Chebyshev polynomials to shape the filter’s characteristic function. The optimum Chebyshev filter, along with two chained-function filters, each of the sixth-degree, are realized, simulated, and compared as lowpass stepped impedance filters with a half-power passband of 1 GHz. After a detailed comparison, it is concluded that the optimum Chebyshev filter outperforms, or at least matches, the performance of the chained-function filters. This suggests that the optimum Chebyshev filter can effectively replace chained-function filters in all applications, offering a superior solution.

Modified Inverted CSRR and Stepped Impedance Stub based Bandstop Filter with wide passband

Modified Inverted CSRR and Stepped Impedance Stub based Bandstop Filter with wide passband

Compact microstrip lowpass filter with wide stopband and sharp transition band using radial stub resonator

This study introduces a compact microstrip lowpass filter that offers a wide stopband and a low transition band. The couple radial stubs are designed for having sharp roll-off. The filter has a −3 dB cut off frequency of 1.6 GHz, with a transition band ranging from 1.6 to 1.7 GHz with attenuation levels of −3 dB and −20 dB, respectively. To ensure a wide stopband, the filter utilizes bended transmission lines with stepped impedance suppressing cells, resulting in a stopband attenuation of 20 dB from 1.7 to 28 GHz. The insertion loss in the passband is less than 0.1 dB, and the overall size of the filter is 0.127 × 0.087 λg2.

High-Sensitivity Differential Sensor for Characterizing Complex Permittivity of Liquids Based on LC Resonators.

This paper proposes a high-sensitivity microstrip differential sensor for measuring the complex permittivity of liquids. The prototype of the differential sensor was formed by cascading two LC resonators on a microstrip transmission line based on stepped impedance. A strong electric field was found to be distributed in the circular patch of the LC resonator; therefore, a cylindrical micropore was set in the center of the circular LC resonator to measure the dielectric sample, which maximized the disturbance of the dielectric sample on the sensor. By optimizing the size of the circular LC resonator, a high-sensitivity sensor circuit was designed and manufactured. The complex permittivity of the test sample was calculated by measuring the transmission coefficient of different molar concentrations of ethanol-water solutions. The experimental results show that the designed differential sensor can accurately measure the complex permittivity of liquid materials with an average sensitivity of 0.76%.

Super compact and ultra-wideband bandpass filter with three band notches using triple-mode stepped impedance resonator and defected ground structure

A super-compact ultra-wideband (UWB) microstrip band-pass filter (BPF) with triple-notched bands and wide stopband is proposed in this paper. The super-compactness of the proposed filter is achieved by integrating the modified SCRLH-TL UWB-BPF and backbone-shaped defected ground structure (DGS). The equivalent LC circuit models of the DGS and the modified SCRLH-TL UWB-BPF with the DGS are analyzed to validate their numerical simulation results. To introduce the triple notched-bands to mitigate the interference the two triple-mode SIRs are designed and loaded on the modified UWB-BPF without increasing the circuit size. The proposed filter was fabricated by using a conventional PCB process with the substrate of FR4. The measured 3-dB passband ranges from 2.8 through 10.2 GHz with the fractional bandwidth (FBW) of about 114%. The triple-notched bands with attenuation of more than 15 dB are measured at 4.4, 5.3 and 8.2 GHz, respectively. The filter exhibits a high selectivity with steep skirt property and has a wide upper stopband with an out-of-band rejection of −10 dB at 11.8−20 GHz. Its total dimension, including the rectangular substrate with feed lines, occupies only 16mm × 8 mm.

Quarter-Wavelength and Open-End Half-Wavelength Four-Section Coaxial Stepped Impedance Resonators for High-Power Space Bandpass Filters

Quarter-Wavelength and Open-End Half-Wavelength Four-Section Coaxial Stepped Impedance Resonators for High-Power Space Bandpass Filters

Derivation of Generalized Design Formulas for Modified Branch-Line Coupler with the Second Harmonic Suppression Characteristics

We propose a modified branch-line coupler composed of the open stubs and stepped impedance lines. This structure allows the second harmonic suppression and size reduction. We present the steps to transform from a conventional branch-line coupler to the proposed structure using equivalent circuits and derive the generalized design formulas. From the results analysis of the design sample, we demonstrate the validity of the derived formulas. The fabricated branch-line coupler provides more than 30 dB the second harmonic suppression and about 30 % size reduction compared to a conventional branch-line coupler.

General rotationally symmetric coupled feeding structure and its application to single- and dual-band balanced filters

This paper proposes a new general rotationally symmetric coupled feeding structure and its applications to the design of single- and dual-band balanced filters for high common-mode (CM) suppression. The balanced feeder consists of two coupling lines coupled with a ring resonator, which can be either a uniform impedance ring resonator or a stepped impedance ring resonator. Under differential-mode (DM) excitation, the voltage distributions of the coupling-line and resonator are both rotationally even-symmetric and the total coupling coefficient adds up, which indicates that the proposed feeding structure can achieve DM transmission characteristic. Under CM excitation, their voltage distributions are rotationally even- and odd-symmetric, respectively, so the total coupling coefficient cancels out to zero and CM suppression property is achieved. For demonstration, four single- and dual-band balanced filters with wide range of CM and harmonic suppression are designed, fabricated, and measured, and the simulation and measured results match well.