Stepped-impedance Filter Research Articles

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.

A Miniaturized Dual-Band Dual-Polarized Base Station Antenna Loaded With Duplex Baluns

A novel miniaturized dual-band and dual-polarized base station antenna loaded with duplex baluns is proposed in this letter. The duplex balun consists of a lower-band filter structure (LFS) and an upper-band filter structure (UFS). The LFS contains a stepped-impedance filter, an open-circuited stub, and an impedance matching section. The UFS contains a highpass filter and an impedance matching section. The proposed antenna has two independent current paths, which enables it to operate in dual bands, and the two paths are bent to achieve its small overall size. By miniaturizing the antenna and loading LFS&UFS, the operating bands of 1.71-2.17 GHz and 3.22-3.7 GHz, the compact size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.24 \times 0.24 \times 0.18\lambda _{LL}^3$</tex-math></inline-formula> (λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_LL</i> is the wavelength at the lowest frequency of the lower band), the lower coupling coefficients(<-20dB), the normal in-band radiation characteristics, and good out-of-band suppression characteristics(>20dB at the lower-band ports as well as >23dB at the upper-band ports) are obtained. It represents an excellent scheme for 5G applications.

Perencanaan Rancang Bangun Microstrip Band Pass Filter dengan Struktur Tapped Input Hairpin pada Aplikasi Jaringan Mid-band 5G Telkomsel

Microstrip filter is a type of Radio Frequency (RF) filter that uses a thin electrical conductor separated from the ground plane by using a dielectric called the substrate. Microstrip filters are generally printed on Printed Circuit Boards or PCBs where high-frequency signals are directed from one part of the system to another with high efficiency. There are several types that can be applied to the operation of microstrip filters, one of which is a band pass filter. Band pass filter is a filter that can pass a signal with a certain frequency that is limited by a low cut-off frequency and a high cut-off frequency, and is able to dampen signals that are below the cut-off frequency and above the high cut-off frequency. There are several types of resonator designs that can be used for reference in the manufacture of microstrip filters, such as tapped line input hairpin filters, stub loaded filters, stepped impedance filters, and combline filters. By using the reference form of the tapped line input hairpin, this journal is intended for planning the manufacture of microstrip filters in the application of Telkomsel's 5G technology.

Design of a Wide-Beamwidth Pixelated Dielectric Resonator Antenna Using a Modified Stepped-Impedance Filter to Suppress Harmonics

This study designed a wide-beamwidth pixelated dielectric resonator antenna (DRA) combined with a low-pass filter (LPF) to suppress harmonics. The DRA was designed to create a wide-beam pattern with a pixelated structure. The pixelated DRA was optimized by a genetic-learning particle swarm optimization algorithm. To prevent significant higher-mode radiation and harmonics from occurring in the DRA, an LPF was included in its feeding line. The filter had a seventh-order Chebyshev design, and a hybrid step-impedance filter was proposed by modifying the step-impedance filter for use in narrow spaces behind the ground.

Integrating multiple stubs in stepped‐impedance filter aiming for high selectivity

A design technique to include multiple and fully-controlled transmission zeros (TZs) in the frequency response of rectangular waveguide commensurate-line stepped-impedance filters is presented in this letter. These bandpass filters (BPFs) are known for having reduced sensitivities against manufacturing inaccuracies and are composed of multiple waveguide sections. In order to improve their selectivity, 3λg/4 and λg/4-stubs are included to create multiple TZs around the passband. The proposed technique allows us to add multiple stubs in a single section and, therefore, only minor adjustments in the affected part of the filter are required, which simplifies the overall design process. The technique has been verified with a design example with four TZs (two on each side) near the passband.

Implementation of Microwave Circuits Using Stereolithography.

In this work, the use of additive manufacturing techniques through stereolithography for the manufacture of high-frequency circuits and devices is presented. Both the resin and the 3D printer used in this research are general-purpose commercial materials, not specifically intended for the implementation of microwave networks. The manufacturing and metallization procedures used to produce substrates for the design of planar microwave circuits are described, introducing the characterization process carried out to determine the electrical properties of the resin used. The ultrasonic techniques that allow the structural analysis of the manufactured substrates are also described. The electrical characterization provides a relative dielectric permittivity of 3.25 and a loss tangent of 0.03 for the resin used. In addition, the structural analysis shows a homogeneity and a finish of the manufactured parts that is not achievable using fused deposition modeling techniques. Finally, as a proof of concept, the design and manufacture of a complex geometry stepped impedance filter on a multi-height substrate using stereolithography techniques is presented, which allows for reducing the size of the traditional implementation of the same filter while maintaining its high-frequency response performance.

System modelling and synthesis of stepped impedance resonators and filters

This study presents system-based models of stepped impedance resonators (SIRs) based on the singularity expansion method. Analytical expressions of the transfer function and the impulse response for two types of dual-band step resonators are derived (open-circuited λ/2 and short-circuited λ/4) for general impedance ratio (K). The accurate physical poles of the structures are acquired using a pole-energy-based refined matrix pencil scheme. Then, the frequency domain expression is used to develop a precise equivalent lumped element circuit model for the dual-band SIRs. Based on that, a direct pole-zero placement synthesis method is applied to design a three-stage dual band-pass filter. Very good matching between the transfer function of the system model and the frequency response data of the synthesised SIR filter is observed. The explored system-based modelling and synthesis procedures can be generalised systematically to design more complex filter structures.

Analysis of Microwave Passive Circuits Designed Using 3D Printing Techniques

This work presents the results of a preliminary study conducted to assess the viability of using 3D printing techniques for the manufacturing of microwave passive circuits based on microstrip techniques, both for prototyping new low-cost devices and for fast and costless testing of new circuits designs. The study was aimed to test two crucial factors in the viability of these procedures: the performance of the circuit in terms of its functionality and the structural integrity of the resulting structure. A low-cost 3D printer is proposed for the dielectric substrate design of microstrip circuits. Standard PolyLactic Acid (PLA) material has been characterized in the microwaves frequencies for different substrate sizes and densities. To verify the proposed method, a low-pass stepped impedance filter was designed, simulated, and measured. Finally, a structural analysis using Non-Destructive Testing (NDT) ultrasonic techniques has been carried out based on deconvolution and resonant spectroscopy. Both, electronic and structural results, have shown the feasibility of using low-cost additive techniques in the design of microwave circuits. DOI: 10.5755/j01.eie.25.2.23202

Bending Limit Tests for Ultra-Thin Liquid Crystal Polymer Substrate Based on Flexible Microwave Components.

In this paper, bending limit tests for one ultra-thin liquid crystal polymer (LCP) substrate (Rogers 3850) based on the mechanical properties of flexible microwave microstrip components are presented. First, a set of 50 Ω microstrip lines, a band-pass filter, and a stepped impedance filter in X-band, are designed by using double clapped LCPs with 50 μm thickness of substrate and 18 μm thickness of copper, which is fabricated by conventional photolithography. Then, the limit tests of the flexibility of the LCP microwave microstrip components are presented, and the range of the bending limit radius, from 1 mm to 0.75 mm, is demonstrated from the testing results. It is found that the cause for component failure is fracture of the copper (18 μm thickness) laminate, according to the bending limit test experiments. Finally, the analysis of the reasons for the collapse of the microwave components, under bending situations, is explored. The results from this work would be useful for further designs of the flexible microwave devices and systems on LCP substrates, with compact sizes and good performance.

RF Test Article Experiment on the Impact of Non-Hexavalent Chromium-Based Conversion Coatings on Electrical Assemblies

Abstract Conversion coatings are treatments applied to aluminum structures to inhibit corrosion while maintaining electrical conductivity. In aerospace applications, the most common type of conversion coatings (MIL-DTL-5541 Type I) contain hexavalent chromium compounds as the corrosion-inhibiting agent. These Type I conversion coatings have a long pedigree and are highly effective in preventing corrosion; however, the hexavalent chromium compounds in these coatings are carcinogenic and water-soluble. Therefore, the use of these compounds is highly regulated in order to protect both workers and the public, leading to high cost in both use and disposal. Regulations are also beginning to restrict outright use, where new designs for the DOD are prohibited from using Type I coatings by DFARS 48 CFR Parts 223 and 252 and all use has been prohibited by Europe by REACH regulations since September 2017. In response, more environmentally friendly non-hexavalent chromium-based processes, referred to as MIL-DTL-5541 Type II conversion coatings, have become available. However, the long term reliability and performance impacts resulting from the use of these coatings are not fully understood and there is an ongoing effort in the aerospace industry organized by NASA to fully define these impacts while hardware is still in the design stage. While significant work has been performed to define the corrosion performance of various type-II conversion coatings, there has been minimal work performed to quantify the impact a type-II conversion coating would have on RF electrical assemblies. The standard methodologies defined by MIL-DTL-81706B have significant limitations and cannot fully capture the impact at microwave frequencies. For this reason, an investigation is underway at Northrop Grumman to quantify the impact these coatings may have on the quality, reliability, and performance of our electronic systems. At IMAPS 2017, Northrop Grumman introduced a RF test article designed to assess the longitudinal impact a Type II conversion coating would have on RF electrical assemblies where plated printed wiring boards (PWBs) and aluminum structures come in intimate contact. The test article features a specialized suspended stripline/microstrip stepped impedance filter designed to de-tune in the presence of galvanic corrosion. This talk follows the work presented in IMAPS 2017 by discussing an experiment where three different populations of test articles, each coated with a different type of conversion coating, are subjected to environmental testing. This talk also discusses how an initial measurement of these test articles before environmental exposure showed little difference between these populations. Finally, this talk reviews the initial results of this experiment, discussing environmental testing and the RF measurements captured during these tests.

RF Test Article to Assess the Impact of Non-Hexavalent Chromium-Based Conversion Coatings on Electrical Assemblies

Abstract Conversion coatings are used to inhibit corrosion on aluminum structures while maintaining electrical conductivity. The most common type of conversion coatings in aerospace applications (MIL-DTL-5541 Type I), contain hexavalent chromium compounds as the corrosion-inhibiting additive. These Type I conversion coatings have a long pedigree and are highly effective in preventing corrosion; however, the hexavalent chromium compounds in these coatings are carcinogenic and water-soluble. Therefore, the use of these compounds is highly regulated in order to protect both workers and the public leading to high cost in both use and disposal. In addition to these regulations, use of these materials on new designs for DOD is prohibited by DFARS 48 CFR Parts 223 and 252, and is scheduled to be prohibited in Europe in September 2017 by REACH regulations. In response, new more environmentally friendly non-hexavalent chromium-based processes are becoming available. Coatings resulting from these types of processes are referred to as MIL-DTL-5541 Type II conversion coatings. The long term reliability and performance impacts resulting from the use of these coatings are not fully understood and there currently is an effort in the U. S. aerospace industry organized by NASA to fully define these impacts while hardware is still in the design stage. While significant work has been performed to define the corrosion performance of various Type II conversion coatings, there has been minimal work performed to quantify the impact a Type II conversion coating would have on RF electrical assemblies where plated printed wiring boards (PWBs) and aluminum structures come in intimate contact. The primary concern for these assemblies is that these junctions are inherently susceptible to galvanic corrosion; PWBs are clad with copper, which is highly cathodic while aluminum is highly anodic. In order to reduce the potential for galvanic corrosion, PWBs in DOD applications are typically plated with SnPb coating which is less cathodic than the copper. In addition, an immersion bath is used to coat the aluminum with a conversion coating that is less anodic. Changes to the conversion coating could increase the galvanic corrosion occurring at this junction. In addition, RF signals may also be negatively impacted by changes to the electrical resistivity and parasitic capacitances caused by changes to this junction. For this reason, it is highly desirable to create a RF test article that is highly sensitive to the impacts of galvanic corrosion at the junctions of passivated aluminum and plated printed wiring boards. This talk discusses a RF test article that is designed to assess the longitudinal impact of galvanic corrosion on electrical assemblies. The test article features a specialized suspended stripline/microstrip stepped impedance filter that is designed to de-tune in the presence of galvanic corrosion. The design of this filter uses a pair of machined aluminum housings to sandwich a thin two sided printed wiring board. The high-impedance sections of the filter employ cavities above and below the thin PWB to create an effective airstripline transmission line. The low-impedance sections of the filter employ a PWB ground plane to create a microstrip mode. Small aluminum feet are machined in the bottom aluminum housing to create an electrical contact between the aluminum housing and PWB ground plane. These feet are designed to function as sacrificial elements that corrode away in the presence of galvanic corrosion, creating series capacitance in the ground signal path. This talk reviews recent test results that show how the response of this specially designed filter changes in the presence of galvanic corrosion and compares these results with electrical simulations. This talk also discusses how information gained from the filter response can be used to assess the electrical impact of Type II conversion coatings. Finally, this talk will discuss the experimental design needed to quantify the impact of Type II conversion coatings with respect to the current baseline processes.

Compact low‐pass stepped impedance filters with enhanced out of band response

AbstractThis article presents slow‐wave microstrip transmission lines based on a double‐layer PCB substrate for miniaturized and high‐rejection low‐pass filters design. The slow‐wave effect is obtained by inserting metallic via rows within the lower substrate layer. Realized slow‐wave microstrip transmission lines exhibit a high effective dielectric constant of 7.4 instead of 3 for classical microstrip transmission lines. Based on this concept, miniaturized high‐rejection 7th‐order low‐pass stepped‐impedance filters with a cut‐off frequency of 2.45 GHz were designed, fabricated and measured. Measurement results are in good agreement with simulations. Thanks to the slow‐wave microstrip lines, the size of the realized filters is reduced by 65% as compared to a classical filter prototype, without degrading electrical performances.

Dual Band High Directivity Microstrip Patch Antenna RotatedStepped-Impedance Array Loaded with CSRRs for WLAN Applications

A suspended dual band planar antenna based on a stepped-impedance structure modified to an array, loaded with Complementary Split-Ring Resonators (CSRRs), possessing good directivity pertaining point to point backhaul communication is acquainted. The presented antenna radiates at 2.4-2.5 GHz (4.4%) and 5.3-5.9 GHz (12%) with |S11| < −10 dB, accompanying directivity of 11.6 dBi and 11.3 dBi respectively. The antenna is loaded with CSRRs which works as a L-C tank resonator, to obtain better coupling, and to lower the frequency of radiation in 2.4 GHz band along with decreasing the return loss for both the bands of WLAN. The Suspended antenna, symmetrical across vertical axis, has four branches, each of which are obtained from Maximally Stepped-Impedance filter. A stable radiation pattern with high directivity in both the WLAN bands is achieved.

A novel band‐pass filter based on a periodically drilled SIW structure

AbstractThe design and fabrication of a band‐pass step impedance filter based on high and low dielectric constant sections has been realized on substrate integrated waveguide (SIW) technology. The overall process includes the design of the ideal band‐pass prototype filter, where the implementation of the impedance inverters has been carried out by means of waveguide sections of lower permittivity. This can be practically achieved by implementing arrays of air holes along the waveguide. Several SIW structures with and without arrays of air holes have been simulated and fabricated in order to experimentally evaluate their relative permittivity. Additionally, the equivalent filter in SIW technology has been designed and optimized. Finally, a prototype of the designed filter has been fabricated and measured, showing a good agreement between measurements and simulations, which demonstrates the validity of the proposed design approach.

High-Performance On-Chip Low-Pass Filters Using CPW and Slow-Wave-CPW Transmission Lines on Porous Silicon

We report on the design, fabrication, and characterization of high-performance stepped-impedance filters (SIFs) on a locally formed porous Si layer on the CMOS Si wafer. This technology provides the appropriate platform to reduce the high losses within the Si substrate, along with the possibility to tune the substrate permittivity in order to achieve high characteristic impedance ( $Z_{C}$ ) transmission lines, which are important for the specific filters and other passive circuits, e.g., power dividers. By combining high- $Z_{C}$ coplanar waveguides (CPWs) and low- $Z_{C}$ slow-wave CPWs (S-CPWs), high-quality SIFs were achieved, with cutoff frequencies at 30 and 60 GHz. These SIFs were characterized in the frequency range of 0–100 GHz and demonstrated an insertion loss lower than 2 dB in the whole passband and a rejection higher than 30 dB in the stopband. The achieved performance is better than that exhibited by SIFs using only S-CPWs.

Application of Stepped-Impedance Technique for Bandwidth Control of Dual-Band Filters

This paper demonstrates application of the popular stepped-impedance technique to control the bandwidths of dual-band filters independently. Unlike previous dual-band stepped-impedance filters, the role of the stepped-impedance technique is to control the bandwidths of the two bands rather than to provide dual-band performance. The exact relationship between stepped-impedance ratios and the ratio of the two absolute bandwidths is obtained through rigorous analysis. Moreover, since the proposed filters can be synthesized with popular transmission lines and coupled lines that are very-well characterized, time-consuming full-wave simulation can be minimized. Along with the complete set of design equations, experimental results for transmission-line and coupled-line dual-band filters are provided that verify the proposed approach.

Modeling and analysis of a conventional and localized electromagnetic bandgap structures for suppression of simultaneous switching noise

The transmission line method (TLM) is applied for the analysis of a conventional electromagnetic bandgap (EBG) and enhanced moat structures with an arbitrary shaped power/ground plane. Fast and accurate modeling by TLM reveals computationally efficient results as compared to 3D full-wave electromagnetic analysis. Moreover, it is shown that the suppression bandwidth of an EBG structure can be easily analyzed with stepped impedance filter approach, and the calculated bandwidth is identical to the measured bandwidth. In general, the conventional EBG structure provides highly efficient suppression of simultaneous switching noise (SSN) over the broadband range; however, it is difficult to apply this concept to real PCB design for high-speed digital circuits due to degeneration of the signal integrity (SI) performance. In this work, an enhanced localized EBG structure is suggested to enlarge the suppression bandwidth by modifying the EBG pattern without causing any SI problem. The number of bridges for each pattern is minimized, and a meander-shaped bridge is used to increase the inductance of the bridge. As a result, good suppression of SSN is achieved from 0.8 to 6.5 GHz with a −25 dB suppression level. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1571–1577, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26910

Impedance matching and spurious-response suppression in stepped-impedance low pass filters

In this article, the method of least squares is used to design a stepped-impedance low pass filter with arbitrary specifications on the pass, transition, and stop bands, having different input and output impedances.The equivalent circuits of the line sections and step discontinuities are used (with appropriate dispersion relations) to determine the filter transmission matrix and the scattering parameters, which are then used to construct an error function. Its minimization is performed by the combination of particle swarm optimization and conjugate gradient methods. The conversion of lumped filter designs, by Butterworth, Chebyshev, and elliptic methods to the equivalent microstrip filters (namely conversion of L and C components to strip lines) may be difficult to realize. The proposed method of least squares procedure leads to the design characteristics having sharper transition bands and a wider pass band. The rectangular split ring resonators, as patterned ground plane, will remove the spurious responses in the stop band and actually increase the stop bandwidth. The results obtained by full-wave simulation softwares, fabrication, and measurements verify the proposed method for low pass stepped-impedance filter design. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26184

A Planar Dualband Antenna Array

A planar dual-band antenna array for point-to-point communication is presented. The proposed compact antenna array operates at 2.4-2.5 GHz (4%) and 5.1-5.5 GHz (7.5%) with |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB, and corresponding gains of 11-13.3 dBi and 10.6-14.5 dBi respectively. It consists of four branches suspended at a height of 5 mm above a 250 × 250 mm ground plane. Each quarter consists of a series-fed meandered step-impedance filter connected to a L-shaped radiator, and they transverse horizon tally away from the epicenter. The insertion loss method with non-redundant synthesis for filter design is applied to control the radiation aperture of the antenna array, allowing both the 2.4 GHz and 5.5 GHz radiators to co-exist and operate independently. A stable broadside radiation pattern and gain are achieved.

A Novel Narrow Passband Millimeter Filter Using Suspended Improved Compact Microstrip Resonant Cell

A novel millimeter wave narrowband bandpass filter using improved suspended compact microstrip resonant cell is proposed in this paper. Compared to the traditional high/low step-impedance filter, the improved CMRC structure possesses good lowpass filter characteristics. Besides, it can shorten the circuit size over 50%. And a suspended CMRC has better filter characteristics of low return loss and sharper stopband rejection than a traditional CMRC. Based on the improved suspended CMRC, a novel millimeter wave narrowband BPF operating at center frequency of 40 GHz is designed and tested. The investigation results show that the BPF has low insertion loss below 1 dB in the narrow passband with a bandwidth of 10% and sharp rejection in the stopband.