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With the rapid growth of terrestrial and mobile telecommunications, companies in this sector need highly selective equipment, lightweight with low manufacturing costs, hence the interest in miniaturizing front-end electronic components such as filters, antennas, mixers etc. In this paper, a novel structure of a passband and highly selective filter is proposed and discussed. The design involving two complementary split-ring resonator filter (CSRRF) configurations in microstrip technology operating at 6 GHz is investigated. To achieve the goal of this research the "N + 2" cross-coupling matrix method is used. The step-shaped CSRR filter that yields better electrical performance, smaller size, and low weight is realized. Its frequency responses simulated with HFSS software are compared with experimental measurements. An excellent agreement is observed in terms of bandwidth and center frequency. [ABSTRACT FROM AUTHOR]

This paper proposes a compact microstrip filtering power divider (FPD) with high selectivity and equal power division ratios based on the composite right/left-handed (CRLH) concept. The proposed equal microstrip FPD is designed by cascading two CRLH unit cells and a grounded via hole. The proposed CRLH unit cell is realized by an interdigital capacitor loaded between two transmission lines (TL) on the upper metal layer and the fractal/meander complementary split-ring resonator (FMCSRR) on the ground plane. The grounded via hole has been used to improve frequency selectivity and out-of-band rejection of the proposed microstrip FPD. The equivalent circuit model compared with full-wave simulation results of the proposed microstrip FPD has been provided. The proposed microstrip FPD has been fabricated and measured, and a good agreement has been found between the simulation and measurement results. The proposed microstrip FPD has a passband covering 2.38–2.45 GHz, and its measured 3 dB fractional bandwidth is about 2.9 %. The total size of the proposed microstrip FPD is 0.17 λg × 0.07 λg. Compared with other reported FPDs, the presented microstrip FPD has many advantages like compact size, low loss, easy fabrication, extremely sharp rejection skirts around the desired passband and high selectivity. [ABSTRACT FROM AUTHOR]

This paper presents a dual-band microstrip filter with left-handed characteristics, featuring high selectivity and miniaturization. The design achieves negative permittivity and permeability by integrating H-shaped complementary split-ring resonators (CSRRs) within a substrate integrated waveguide (SIW). To enhance out-of-band rejection performance, a defected ground structure (DGS) is introduced. By applying the Half Mode SIW (HMSIW) principle, the equivalent magnetic walls of the SIW are cut, resulting in a 50% size reduction. Dual-frequency characteristics are realized using a symmetrical H-shaped CSRR, with the filter operating in the Sub-6G frequency band. Experimental results demonstrate that the filter exhibits good selectivity and low insertion loss at 3.5 GHz and 4.8 GHz. Tuning of the second frequency band is achieved by adjusting the coupling distance between the CSRR and metal via. This work has significant application potential in the fields of wireless communication and RF technology. The study provides theoretical support and technical insights for the design of future compact multi-band filters. [ABSTRACT FROM AUTHOR]

This paper presents a direct design approach and explicit design formulas for a wideband quadruplet bandpass filter with a pair of transmission zeros. A filter can be designed based on a filter schematic composed of only transmission lines and a short‐circuited coupled‐line section. The electrical length of all lines including the coupled‐line section is 90° ${}^{\circ}$. The impedances of all lines can be calculated by explicit design formulas given in terms of the normalised coupling values in a coupling matrix of a quadruplet filter, which differentiates this work from existing design approaches. A fourth‐order filter example is illustrated for demonstrating the practicality of using the presented structure and design formulas. This paper also discusses the expansion of the presented direct design approach for higher‐order filter designs. [ABSTRACT FROM AUTHOR]

In this article, we describe the design of the substrate integrated waveguide (SIW) millimeter-wave filtering antenna for 5G communication. It comprises a Γ-shaped slot antenna integrated into a SIW resonant cavity and a bandpass filter (BPF) based on a SIW coupled resonant cavity, which are directly cascaded to form a filtering antenna. The BPF is made up of six resonant cavities, with the opening size between the fourth-order resonant cavities adjusted to achieve magnetic coupling between them. This results in the desired bandpass characteristics. The antenna’s radiation is generated by the Γ-shaped slot structure. To verify the proposed structure and design concept, the filtering antenna was manufactured and measured. The simulated and measured results showed good consistency. The −10 dB impedance fraction bandwidth of the antenna is 2% (25.2–25.7 GHz), with a flat gain of 5.9 dBi within the operating range. The proposed filtering antenna has low loss, simple structure, and low cost, and it is easy to integrate with other electromagnetic sensor systems. It is well suited for the 5G millimeter-wave band and is anticipated to remain compatible with future generations of mobile communication systems. [ABSTRACT FROM AUTHOR]

A novel balanced nonreciprocal bandpass filter based on the stepped impedance resonator and the timemodulated resonator is proposed in this paper. The balanced nonreciprocal bandpass filter is fabricated on a single PCB board, and the compact structure is achieved through the gap coupling structure of the microstrip resonators. Utilizing the quarter-wavelength transformer and gap coupling structure, good isolation between RF and modulated signals is achieved without adding lumped elements. Relying on the efficient modulation circuit and the half-wavelength stepped impedance resonator's inherent resonance characteristic, an excellent nonreciprocal characteristic of the differential signal and effective suppression of common-mode noise are achieved. A balanced microstrip nonreciprocal bandpass filter operating at the center frequency of 1.5 GHz is designed, simulated, and experimentally verified. The measured reverse isolation is greater than 20 dB with a bandwidth of 48.8 MHz. The measured forward differential-mode insertion loss is 3.7 dB at the center frequency of 1.5 GHz. In the range of 1.2-1.8 GHz, the measured common-mode noise suppression is larger than 60.4 dB. [ABSTRACT FROM AUTHOR]

Copyright of ARO: The Scientific Journal of Koya University is the property of Koya University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research article presents a novel compact cross-coupled bandpass filter (BPF) microstrip operating at 1.2 GHz. The proposed filter is designed and developed by coupling the RLC resonator and TL transmission line circuits, excited by a symmetrical microstrip feed line (MSL). The fractional bandwidth (FBW) of the filter is found to be 12.83%. The equivalent lumped circuit model of the filter is obtained from AWR Designer. By decomposing the filter into separate entities for individual electromagnetic (EM) simulation via the High Frequency Structure Simulator (HFSS) and the equivalent lumped circuit model of the filter is obtained in AWR designer, this approach achieves computational efficiency, facilitating the extraction of key parameters aligned to specified general coupling matrix (CM). All these parameters from the overall response of the filter are used in the Chebychev approximation method models at the second and fourth order. The transmission zeros are close to the bandpass edge. The proposed filter has a reflection loss(|S11|) less than -25 dB and an insertion loss (-|S21|) less than 0.21dB. Besides, the filter has strong and varying group delay response over the entire bandwidth from 1.15 GHz to 1.3 GHz. The proposed bandpass filter also shows good stopband rejection (being greater than 25 dB) and |S11|< -0.1 dB from 1.35 GHz to 1.75 GHz and sharp decrease in bandwidth at the hard shoulder. All simulated results are extracted via the HFSS simulator method based on finite element, FEM. All results produced by AWR design software have a close similarity with the results simulated and optimized by HFSS. [ABSTRACT FROM AUTHOR]

In this letter, a miniaturized U-shaped microstrip filter based on a load-coupled open line is proposed. It is composed of a step impedance resonator and parallel coupled open stub line. Interfinger feed is used to enhance coupling. This configuration and coupled open stub lines form four transmission zeros between two passbands as part of open coupled stub lines to increased out-of-band rejection. The analysis of formation reason of transmission zero is conducted using lossless transmission line theory and even-odd mode analysis techniques. A filter operating at 2.53 GHz and 5.53 GHz is simulated and fabricated. The insertion loss of first passband is 1.30 dB, and return loss is -18.60 dB. The insertion loss of the second passband is 0.70 dB, and return loss is 22.89 dB. The out-of-band rejection is maintained below -20.00 dB. The final model size is 0.20λg × 0.23λg. The final physical measurement results confirm theoretical results. [ABSTRACT FROM AUTHOR]

Integration of compact, tunable, low-cost monolithic microwave integrated circuit-based bandpass filters on a semiconductor substrate has been a persistent requirement in the communication industry. In the present investigation, a compact reconfigurable bandpass filter is fabricated using a double T-transducer based on the phenomena of magnetostatic surface spin waves (MSSWs). The Ce-doped Bi0.1YIG 500 μm thick disks with cerium concentration in the range of 0.2–1.0 provide the path for the propagation of MSSWs. The operating frequency for this device extends from S to X band Rogers RT/duroid® substrate, which is used for planar microstrip filter design, fabrication, and testing for practical applications. The effect of the coupling gap between the two transducers was optimized using appropriate choice of lumped components to improve the performance of the filter. The best coupling was observed for 1.2 mm coupling gap. The simulated and experimental results confirm the lowest insertion loss of −1.24 dB. The operating frequency shows a large tunability of 132.3% with a relatively small bias field of 0.3–2.1 kOe. The promising characteristics of bandpass filters such as low passband insertion loss, narrow bandwidth, high bandpass reflection coefficient, and high band-stop rejection were achieved by varying the Ce concentration in YIG samples. [ABSTRACT FROM AUTHOR]

A novel and simple design method of wide‐passband filters with wide stopband based on half‐wavelength (λ/2) resonators coupled by a short connected line (SCL) is proposed and analysed in this paper. Different from the traditional parallel‐coupled structure filters, SCL is proposed to realize a strong coupling between two adjacent resonators and suppress the parasitic passbands simultaneously. And the eigenmode analysis method and impedance ratio characteristics are both used to reveal the mechanism of wide‐stopband implementation. To further expand the stopband, filters based on step‐impedance resonators (SIRs) with SCL are proposed and analysed in detail. To verify the proposed design method and wide‐stopband filtering structures, three 4‐pole filters with uniform‐impedance resonators (UIRs), SIRs with same impedance ratio, and SIRs with different impedance ratios are designed, fabricated, and measured. The proposed filters can realize a wide stopband up to 5.8f0 with rejection level better than 20 dB. Moreover, the proposed filters can easily realize a wide bandwidth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Broadband couplers consist usually of multiple coupled lines that are each a quarter wave‐length long. Herein, in contrast to conventional methods, a short length of a microstrip line is coupled to a coaxial line. The length of the coupled microstrip line is small compared to the wavelength at the lowest operating frequency. The coupling is weak and the microstrip line is λ/8 at the highest operating frequency. The proposed structure resembles a pair of coupled lines with a linear coupling response. The coupling exhibits a slope of 6 dB/octave over multi‐octave bandwidth. The microstrip line is connected to a lumped element compensating network at the coupled port. The compensating network is a low‐pass circuit with a slope of −6 dB/octave. The power handling of the coupler is high due to the coaxial line and the weakly coupled microstrip line. Electromagnetic simulations and analytical formulations are presented. The broadband coupler handles nearly 1 kW of input power. Due to the weak coupling of the microstrip‐coaxial coupler, the lumped element circuit needs to handle <1.5 W. A high‐power coupler has been fabricated for the frequency range of 30 to 500 MHz. It exhibits a coupling response of 56 ± 0.4 dB. [ABSTRACT FROM AUTHOR]

A quad-band microstrip bandpass filter (BPF) based on a 13-mode resonator is proposed in this article with compact size, high band‐to‐band isolation, and multiple transmission zeros (TZs). The proposed filter is constructed by two transmission paths from the input to the output port, which employs the transversal cancellation mechanism of two transition paths to introduce extra nine TZs. Therefore, a total of 12 TZs are located at 0.2, 1.8, 2, 3.88, 4.61, 5.24, 5.9, 9.26, 9.51, 12.32, 12.75, and 13.27 GHz, respectively, realizing high selectivity. Moreover, the designed filter can achieve quad passbands with centered frequency at 0.95, 2.78, 7.32, and 10.63 GHz for the requirement of multi-service in modern communication systems, with wide bandwidth of 235, 790, 2200, and 1540 MHz, respectively. The measured results agree well with the simulation results, which proves the feasibility of the design method. [ABSTRACT FROM AUTHOR]

In this letter, a method of designing quasi‐elliptic bandpass filter with ultrabroad reflectionless bandwidth and high selectivity is proposed. It is implemented on the basis of a quasi‐elliptic absorptive lowpass filter (ALPF) prototype that features both a low‐reflection response over all normalized frequencies and two controllable transmission zeros near the passband. A distributed‐element absorptive bandpass filter (ABPF) scheme using coupled‐line units is derived from this quasi‐elliptic ALPF prototype. With this distributed‐element ABPF scheme, both ultrabroad reflectionless bandwidth and compact size can be realized. Equations for closed‐form design are derived. A microstrip ABPF operating at 2.0 GHz (i.e., f0) is designed for validation. The measured roll‐off rates of the upper and lower transition bands are 116.44 and 157.41 dBc/GHz, respectively. The return loss is better than 10 dB from direct current to 6.25f0. The size of the overall circuit is 0.12λg2. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, a broadband high‐efficiency power amplifier (PA) with filtering characteristics is proposed. This PA is designed using a series of inverse continuous modes (SICMs) and adds a novel coupled microstrip line filter structure. The terminal of this structure is composed of microstrip lines cascaded to improve the out‐of‐band suppression effect. This filter can achieve low in‐band insertion loss, high passband selectivity, as well as deep stopband rejection performance simultaneously. A PA was designed and implemented using a 10 W GaN HEMT device, verifying its wideband characteristics. The measurement result shows that the 39.6–41.6 dBm output power (Pout), 61.6%–73.7% drain efficiency (DE), and 8.6–10.8 dB gain are achieved at 2.2–2.9 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to microwave lowpass filter design that addresses several challenges in modern microwave systems, including size, performance, and cost. With that in mind, we propose using monic Chebyshev polynomials as the characteristic function for the filter to achieve a low passband insertion loss and maximum cutoff slope. The half-power cutoff frequency characterizes these filters, and the ripple factor is not considered a design parameter. To demonstrate the effectiveness of the monic Chebyshev approximation, a comparison is made with chained function (CF) filters designed for microwave applications. It has been shown that the monic Chebyshev filter outperforms CF filters in all applications, including microwaves. [ABSTRACT FROM AUTHOR]

In this letter, the working mechanism of suggested bandpass filters with connected symmetric short‐circuit stub multimode resonators is described. Because of the design flexibility, the suggested bandpass filters' centre frequencies may be modified based on the design approach. Meanwhile, the suggested bandpass filters have reduced insertion losses and compact sizes. A prototype is built and tested with six passbands centred at 1.57/2.38/3.55/5.14/5.83/6.78 GHz to confirm the design and analysis. Good agreement between the simulated, and measured results is observed, indicating that the proposed structure can be applied in the field of communication, information, and automation. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel planar balanced-to-balanced (BTB) microstrip filtering crossover with high isolation and common-mode (CM) suppression is proposed in this paper. The circuit structure is based on microstrip transmission lines without coupling sections, which can reduce insertion loss and enhance isolation. Specific theoretical analysis of the BTB filtering crossover configuration using transfer matrix and mixed-mode scattering parameters is performed. In order to verify the validity of the theory analysis and design, a microstrip BTB filtering crossover prototype at the center frequency of 2.45 GHz is fabricated and measured with high isolation and excellent CM suppression. [ABSTRACT FROM AUTHOR]

This contribution is an extended in-depth study of our previously initial research work about the compact Log-periodic microstrip DGS lowpass filters. The improved filters proposed use a log-periodic zig-zag structure defected on the ground plane under a compensated microstrip line for microwave filter applications. More importantly, a comprehensive index called figure-of-merit (FoM) is introduced in this paper to characterize the achieved performance of this kind of filters. Results show that high FoMs can be realized for this contribution. The developed filters B and C have dimensions 30.307 mm × 31.17 mm and 22.35 mm × 31.524 mm, while the achieved FoMs for the two demonstrators are approximately 3.5×104 and 3.1×104, respectively. [ABSTRACT FROM AUTHOR]

In this article, a dual-band bandpass microstrip filter (DBBPF) is suggested and studied for RF/microwave applications. Our filter design method is based on two basic concepts; the use of metamaterial resonators in C-shaped split rings (C-SRR) to have the left-handed behavior (LH) with minimized losses and the feed by a microstrip line of significant length folded for the desired miniaturization. The two C-SRRs are optimized for a size of 6 × 3 mm² to cover the desired frequency bands and the two feed lines have a length of 37.1 mm to ensure the necessary adaptation. The search of a strong electromagnetic coupling between the two C-SRRs and the feed lines allowed us to choose the best position to place our resonators in the filter. The simulation of the filter parameters for two different proposed configurations shows two different qualities. According to the simulation outcomes for the two proposed filter configurations, two kinds of frequency response were obtained with different characteristics. For the first configuration where the two C-SRRs are separated by the folded arms of the two feed lines, the filter response is not clear. Contrary to that, the frequency response of the filter is desirable for the second configuration. The suggested filter which is represented by the second configuration has covered both bands (5.88 to 6.39 GHz and 10.75 to 11.16 GHz) for band-pass behavior. In addition, the analysis of the dispersion diagram allowed us to select the electromagnetic behavior associated with each band. [ABSTRACT FROM AUTHOR]

Copyright of SDU Journal of Engineering Sciences & Design / Mühendislik Bilimleri ve Tasarım Dergisi is the property of Journal of Engineering Sciences & Design and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this article, a low loss and compact microstrip ultra-wideband bandpass filter (UWB-BPF) with a narrow-notched band is recommended for suitable applications in ultra-wideband wireless communication systems. The design methodology is presented to develop the microstrip structure of the UWB-BPF pursued by a single notched band (NB) in the passband of the UWB filter. An array of I-shaped defected ground structures and L-shaped defected microstrip structures based lowpass filters is cascaded with a shorted stub based highpass filter to achieve a UWB-BPF response. The two identically folded open stubs are loaded to obtain the narrow NB. The center frequency of the UWB-BPF without the NB is 3.5 GHz, and the stopband is suppressed up to 14.5 GHz. The fractional bandwidth achieved is 160%, with a circuit area of 0.11 ${\rm{\lambda }}_{\rm{g}}^{\rm{2}}$ λ g 2 . Furthermore, the single NB is attained at 5.7 GHz to reject interferences of signal from the 5G network with an attenuation level of 59 dB. The electromagnetic simulated and experimental responses of the designed structures demonstrate a well-matched behavior among them. The NB at 5.7 GHz in the UWB-BPF passband region suppresses the signal interference from the 5G network (5500 MHz), WLAN (5900 MHz), and WiMAX (5800 MHz). [ABSTRACT FROM AUTHOR]

In this communication, a compact absorptive bandpass filter (ABPF) characterized by adjustable bandwidth and phase, low group delay (GD), a high absorptive ratio and low insertion loss (IL) is proposed. The presented ABPF consists of a bandpass section that is made of a quarter-wavelength coupled line and four stubs that are basically a lumped resistor in series with a short-circuited quarter-wavelength transmission line. The stubs not only perform the function of absorption but also have the advantage of adjustable bandwidth and phase. To verify the design concept and analysis formulas, an ABPF operating at 2.4 GHz is fabricated and measured; its simulated and measured results are in good agreement. [ABSTRACT FROM AUTHOR]

Due to its potential harm to space payload, microwave corona breakdown of microstrip circuits has attracted much attention. This work describes an efficient way to suppress corona breakdown. Since the corona breakdown threshold is determined by the highest electric field intensity at the surface of microstrip circuits, lacquer coating with a thickness of tens of microns is sprayed on top of microstrip circuits. The applied dielectric coating is used to move the discharge location away from the circuit's surface, which is equivalent to reducing the highest electric field intensity on the interface of solid/air of the circuit and thus results in a higher breakdown threshold. Two designs of a classic coupled-line bandpass filter were used for verification. Corona experimental results at 2.5 GHz show that in the low-pressure range of interest (100 to 4500 Pa), a 5.3 dB improvement of the microwave corona breakdown threshold can be achieved for a filter with a narrowest gap of 0.2 mm, while its electrical performances like insertion loss and Q-factor are still acceptable. A threshold improvement prediction method is also presented and validated. [ABSTRACT FROM AUTHOR]

This article presents a novel concept for a tiny stepped impedance resonator (SIR) to ease the application of bandpass filters. In recent years, its significance has expanded due to the growing availability of ground plane windows and a floating conductor in the substrate. We propose a small BPF that utilizes a folded SIR transmission line to achieve high performance at low size. The suggested BPF replaces the λg/4 transmission line present in traditional stub BPFs with a T-shaped SIR coupled to a J-inverter structure (transmission line). In addition to the short stubs included in regular stub BPFs, a folded SIR is included here. With this method, we are able to drastically cut the BPF's footprint. The benefits of a BPF are its compact size, negligible insertion loss, and high bandwidth. Because of the ground plane window, the characteristic impedance of the microstrip line is enhanced. This new value is then applied to the calculation that determines the inductive area of the quasi-lumped stepped impedance resonator. This resulted in a slightly smaller device than it would have been otherwise. In addition, a floating conducting microstrip patch is placed directly below the capacitive zone, pushing the filter's initial spurious band even higher. After this, the out-of-band rejection of the gadget sees a significant improvement. By strengthening the coupling between nearby resonators, achieving a wider spectrum of bandwidths within the range conceivable is also feasible. This article aims to compare several filter designs that incorporate newly developed resonator and regular resonators that are already in use. The proposed filter has the centre frequency response at 3.6GHz having insertion loss of 2.5dB and bandwidth increment of 115%, reduction in size dimension of 0.527×0.25mm2. The suggested BPF is flat, making it amenable to semiconductor fabrication at scale. The potential for this design's application in fields as diverse as defense, healthcare, and industry is high. [ABSTRACT FROM AUTHOR]

Machine learning‐assisted electromagnetic simulation has become an effective acceleration tool for designing microwave components by introducing high‐precision models and optimization algorithms, featuring fast design and high efficiency. However, enormous amount of data generated from the blind preliminary and computationally expensive simulation is required to predict the accuracy response. An efficient geometric parameter optimization method for microstrip bandpass filter (BPF) based on a one‐dimensional convolutional neural network is proposed. Nonlinear convergence factor, adaptive weight, and Gaussian difference mutation strategies are integrated using the whale optimization algorithm to avoid the local optimum and improve optimization accuracy. Computational efficiency is improved significantly with small‐scale training data. The validity and efficiency of the proposed method are confirmed by fifth‐order microstrip BPFs, and the performance of the predicted structure parameters is significantly improved, which shows great promise for application in optimization and performance improvement in microwave electromagnetic simulation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A highly selective planar microstrip filtering antenna for point-to-point communication is proposed in this paper. The bandpass filter is composed of a rectangular split-ring coupling resonator, and a portion of the filter is equivalent to a microstrip monopole antenna. Two rectangular split-ring structures with their openings aligned generate resonant characteristics, and U-shaped microstrip coupling structures are wrapped outside to optimize the passband characteristics. One of the U-shaped microstrip structures is transformed into a one-side bent structure as a radiation unit and serves as the resonant structure of the final stage of the filter, reducing the connection loss between the filter and the antenna. The operating frequency band of the filtering antenna is from 6.38 to 6.63 GHz with a reflection coefficient of less than -10 dB, a fractional bandwidth of 3.8%, and a peak gain of 4.46 dBi. The filtering antenna has excellent frequency selectivity, good out-of-band suppression, high gain, and small device size, in addition to its low cost after system integration. The simulation results are consistent with the experimental test results. The filtering antenna as a novel radio frequency sensor can be applied to the point-to-point communication of automated guided vehicles in the logistics field. [ABSTRACT FROM AUTHOR]

Laser sensing has a wide range of applications. In this paper, we propose a pH sensing laser with an ultra-low threshold and low sample consumption based on a whispering-gallery-mode microbubble resonator. Rhodamine 6G aqueous solutions with different pH values are injected through microfluidic channels as the lasing gain media and interact with a high-quality factor microbubble cavity with a sample consumption of only 550 pL to achieve lasing. Subtle pH changes of the aqueous solution lead to changes in lasing intensity in real time, and the threshold reaches a minimum of 0.091 μ J/mm2. The low pump energy density effectively avoids the self-aggregation and photobleaching effects of dye molecules present in high-concentration rhodamine 6G solutions. The lasing characteristics under different pH conditions were determined experimentally and theoretically, and the results are in good agreement. Due to the deprotonation of amino groups in highly alkaline environments, the lasing threshold is highly dependent on the pH of rhodamine 6G aqueous solutions. In the pH range of 10.16–13.14, the lasing intensity changes considerably with the increasing pH. The proposed pH-sensing laser exhibits a fast response time, low toxicity, and a high signal-to-noise ratio, making it promising for highly sensitive alkaline detection in biological applications. [ABSTRACT FROM AUTHOR]

This paper simulates and measures a compact broadband rectifier for voltage doubler Schottky diode. Among them, a two‐stage microstrip line impedance matching network for voltage doubling circuits is used. The imaginary part of the diode impedance is limited by the short‐circuit branch. The impedance conversion transmission line matches the impedance to 50 Ω. The impedance matching in the circuit is only realized by two‐stage microstrip lines, which reduces the physical size of the rectifier and makes the rectifier more compact. Judging the measurement results from 0.8 to 2.5 GHz, the conversion efficiency is greater than 30% at 0 dBm, the bandwidth is 103%, and the maximum conversion efficiency reaches 66.3% at 8 dBm. In addition, the compact size of the rectifier is 23 × 20 mm2. [ABSTRACT FROM AUTHOR]

This paper proposes a microstrip filter with controllable transmission zeros based on the λ/4 stepped impedance resonator. This filter utilizes hybrid electric-magnetic coupling to generate transmission zeros, which can improve selectivity and stop-band performance. A fifth-order filter is designed and manufactured on a ceramic substrate with a center frequency of 26 GHz, bandwidth of 2 GHz and the signal suppression level is better than 42.51 dB from 10 to 22.8 GHz and 48.23 dB from 29.1 to 40 GHz. Furthermore, the proposed filter has a compact size of 2.074 × 1.071 mm (0.566λg × 0.292λg). [ABSTRACT FROM AUTHOR]

Background. Bandpass filters are an integral part of any radio engineering systems and modern communication systems. Research and development of new passive components is due to growing need for such elements for modernization and creation of new modern communication systems. Aim. A brief overview of passive bandpass filters. Their classification according to the type of implementation is given. Methods. Results of experimental research and design of different passive bandpass filters are considered. Results. Lumped elements filters, microstrip filters, filters on high-temperature superconductor films, filter on dielectric resonators, surface acoustic wave filters, bulk acoustic wave filters are considered. At a qualitative level, the main advantages and disadvantages are considered from point of view of electrical parameters and size indicators. Examples of topological and constructive implementation are given. Conclusion. The passive bandpass filters considered in the paper make it possible to implement frequency selection devices at operating frequencies up to 6 GHz and higher, taking into account modern system trends and requirements for devices of this type.

A novel wideband dual‐band bandstop filter with multi‐transmission zeros and multi‐reflection zeros is presented. It consists of two pairs of symmetric open‐ended coupled lines at two sides and (2N − 1) pairs of coupled‐line sections with an open‐circuited stub in the middle. Through even‐ and odd‐mode analyses, general simultaneous equations for characteristic impedances are derived with the proposed algorithm. By suitably selecting all the design parameters, the proposed topology could not only provide a controllable equal‐ripple response in the passband but also control the stopband rejection, bandwidth (BW), and centre frequency ratio in the stopband flexibly. For verification, one prototype circuit is finally fabricated and measured in the experiment. Good agreement between the measured and simulated results is attained so as to successfully validate the correctness of the proposed design method. [ABSTRACT FROM AUTHOR]

This research paper presents a compact dual-band polyester-based wearable bandpass microstrip filter using stepped impedance resonator. In the proposed wearable filter, pass band of 1.85 GHz to 2.66 GHz is useful for ISM band and 3.74 GHz to 7.42 GHz is appropriate to Wi-Fi, WLAN and Wi-Max frequency band applications respectively. In this filter, insertion loss of 0.147 dB and return loss of 32.6 dB at 2.38 GHz insertion loss of 0.469 dB and return loss of 32.3 dB at 4.54 GHz with fractional bandwidth of 34% and 81% is respectively achieved. The proposed wearable filter is fabricated using polyester cloth substrate and selfadhesive copper tape. The Agilent vector network analyzer is used to test the fabricated polyester filter. Good agreement is obtained between the simulated as well as measured insertion loss and return loss of the proposed wearable filter. Equivalent circuit and SAR analysis of this filter is also presented in this paper. Novelty of this research paper is fabrication of high bandwidth dual band wearable filter that can be integrated with wearable antenna to be a wearable Filtenna. Modified equivalent circuit of SIR is prepared and validated. Simulated and measured results are found to be in good agreement. [ABSTRACT FROM AUTHOR]

There has been a lot of interest in microstrip diplexers lately due to their potential use in numerous wireless and computer communication technologies, including radio broadcasts, mobile phones, broadband wireless, and satellite-based communication systems. It can do this because it has a communication channel that can combine two distinct filters into one. This article presents a narrow-band microstrip diplexer that uses a stepped impedance resonator, a uniform impedance resonator, tiny square patches, and a meander line resonator. The projected diplexer might be made smaller than its initial dimensions by utilizing the winding construction. To model the microstrip diplexer topology for WiMAX and WIFI/WLAN at 1.66 GHz and 2.52 GHz, the Advanced Wave Research (AWR) solver was employed. It exhibited an insertion loss of 3.2 dB and a return loss of 16 dB for the first channel, while the insertion loss and return loss were 2.88 dB and 21 dB, respectively, for the second channel. When both filters were simulated, the band isolation was 31 dB. The projected microstrip diplexer has been fabricated using an FR4 epoxy laminate with dimensions of 32 × 26 mm2. The simulated S-parameters phase and group delay closely matched the measurements. [ABSTRACT FROM AUTHOR]

In the field of electronics, technological advancements bring about alterations in electronic devices. With the fast-paced advancements in the era of communication, the frequency bands are becoming congested. One of the frequencies utilized by Wi-Fi-6, 6 GHz, has garnered its share of attention in these changes. This study proposes the design of a Butterworth Bandpass Filter that can be utilized in the IEEE C Band, employing both lumped elements and microstrip transmission lines. The methodology for determining the length and width of the transmission lines, as well as the considerations taken into account during their modification, is provided. A composite filter comprising of both elements and lines is also presented. The combined filter design is aimed at resolving issues arising from the increasing frequency. During the design process, an 8th-order lowpass filter is generated using the Butterworth normalized table, and a bandpass filter with a 200 MHz bandwidth and a 6 GHz center frequency is obtained through the use of a resonant circuit. The dimensions of the transmission lines are determined using theoretical formulas and verified through Matlab files and the MWO-AWR optimization tool. The voltage gain graphs generated demonstrate that the designs created on an FR4 substrate are suitable for use in the IEEE C Band for Wi-Fi-6. [ABSTRACT FROM AUTHOR]

In this paper, two band-pass filters based on the high-order mode of spoof surface plasmon polaritons (SSPPs) are introduced. A novel compact bowfolded strip is proposed as a cell, which exhibits perfect band-pass characteristics. By adjusting the width and groove of the bow-folded strips, high-order mode can be obtained to support the design of band-pass filters. Compared to the conventional single-side rectangular groove SSPPs cell, our proposed bow-folded strip structure cells reduce the electrical size by 59% and 70% at the same cut-off frequency. In addition, the transmission lines of the two proposed band-pass filters are microstrip lines and their over-conversion structures are simple trapezoidal over. A single-band and a dual-band band-pass filters using the proposed SSPPs cell are fabricated and measured, both having almost the same size. The measured results are in good agreement with simulated results, which verify the feasibility of our design. [ABSTRACT FROM AUTHOR]

Context. Microwave stub filters are widely used in radio engineering and telecommunication systems, as well as in technical information protection systems due to simplicity of design, possibility of realization in microstrip design and manufacturability in mass production. For synthesis of stub filters nowadays traditional methods based on transformation of low-frequency prototype filters on LC-elements into filtering structures on elements with distributed parameters are used. The transformations used are approximate and provide satisfactory results for narrowband stub filters. In this connection there is a necessity in development of direct synthesis methods for stub filters, excluding various approximations and providing obtaining of amplitude-frequency characteristics with optimal shape for any bandwidths. Objective. The purpose of the study is to develop a method for direct synthesis of stub band-pass filters and low-pass filters with Chebyshev amplitude-frequency response in the passband. Method. The procedure of direct synthesis includes the formulation of relations for filter functions of plume structures, selection of approximating functions of Chebyshev type for filter functions and formation of a system of nonlinear equations for calculation of parameters of filter elements. Results. A method for the direct synthesis of stub bandpass and lowpass filters with Chebyshev response is developed. Conclusions. Scientific novelty of the work consists in the development of a new method of direct synthesis of l stub filters. The method, in contrast to approximate traditional methods of synthesis of microwave filters, is exact, and the obtained solutions of synthesis problems are optimal. The experiments confirmed the performance of the proposed method and the optimality of the obtained solutions. Prospects for further research suggest adapting the method to the synthesis of filter structures with more complex resonators compared to stubs. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid technique‐based compact narrow band stop filter design for broadband applications. It provides the rejection of 60 dB at the centre frequency of 2.25 GHz without any stop band harmonics over the required frequency band of operation, i.e. 1–10 GHz. This filter is highly appropriated for the rejection of undesired bands for RADAR, electronic warfare, and military communications. [ABSTRACT FROM AUTHOR]

In this paper, a compact and simple structure of an elliptic microstrip lowpass filter (LPF) is designed for harmonic suppression in microwave quadrature hybrid coupler (QHC) applications. A radial resonator and a rectangular resonator are used to produce an elliptic LPF. The proposed LPF is used on the outer sides of the branch line coupler, which has improved the coupler harmonic suppression. Furthermore, artificial neural networks (ANNs) are incorporated to improve the LPF design process. The LPF best structure is obtained using the proposed ANN model. The proposed LPF has a compact size, which only occupies 16.4 mm × 7.3 mm equals to 0.164 λg × 0.073 λg, has a cut frequency of 2.2 GHz, and shows a sharp transmission band with a roll-off rate of 158.3 dB/GHz. Finally, the deigned QHC operates correctly at 1 GHz, which shows high harmonic suppression ability. The proposed QHC provides wide suppression band from 2.25 GHz up to more than 14 GHz, which can effectively suppress 3rd, to 14th harmonics. The proposed coupler features desirable parameters of S11, S21, S31, and S41, with magnitude of −21 dB, −3.4 dB, −3.3 dB, and −22.5 dB, at the operating frequency. The proposed approach mitigates the complexity of the circuit fabrication, compared with the previous methods while achieved desirable performances for the proposed QHC. [ABSTRACT FROM AUTHOR]

In this paper, a novel Ultra-Wideband (UWB) Bandstop Filter (BSF) with five Transmission Zeros (TZ) and three Transmission Poles (TP) is presented. This filter is designed with a new type of resonator. Validation of the proposed filter with the lumped model is also investigated. Further, the transmission line circuit model of the filter is proposed, and consequently even and odd mode impedance is calculated analytically. Furthermore, a compact size of 16.8 mm × 14.98 mm (0.2λg × 0.18λg) is achieved by employing folded stubs. The proposed filter offers an Ultra-wide bandwidth of 7.5 GHz (2.9 –10.4 GHz) with a rejection depth of greater than 20 dB over the entire stopband. Moreover, the upper and lower skirt factors of 70 dB per GHz are achieved. A prototype of the proposed UWB BSF is fabricated and measured. Simulated and measured results are in good agreement, which validates the proposed design. [ABSTRACT FROM AUTHOR]

In this paper, a high-efficiency class-F power amplifier with a harmonic control circuit is proposed. The harmonic control circuit is realised by loading microstrip branch lines to achieve a short-circuit state for the second harmonic. The double spiral defected ground units are loaded on the ground of the microstrip line of the drain bias circuit to produce a low-pass filtering and stopband suppression effect outside the passband, so as to suppress the third harmonic. Meanwhile, it would provide an open-circuit state for the third harmonic, and finally meet the harmonic impedance tuning demands of class-F power amplifier. Through theoretical analysis and simulation, a high-efficiency class-F power amplifier operating at 2.5 GHz ~2.7 GHz is designed. The measured results show that in the working frequency band, the drain efficiency is 66.3%~71.1%, the output power is 40.9 dBm ~42.1 dBm and the gain is 10.9 dB ~11.8 dB. [ABSTRACT FROM AUTHOR]

In this study, designs of dual-band microstrip absorptive (reflectionless) bandstop filters are represented by simulation and experimental studies. Absorptive bandstop filter responses are obtained by adding resistors to the third order bandstop filter designed by loading open circuit meandered stubs to the transmission line connected to the input and output ports. The designed absorptive bandstop filters have low reflection loss at the input port. Reflectionless bandstop filter design can be realized by adding a resistor to the open circuit stub near the input port. In this type of filter, depending on the position of the resistor, bandstop filter with only first or only second absorptive stopband can be designed. The dual-band bandstop filter response having two absorptive stopbands can be obtained by adding two resistors to the stub located near the input port and to the open circuit stub located in the middle. Three dual-band bandstop filters having first absorptive stopband, second absorptive stopband and two absorptive stopbands were fabricated and measured. The center frequencies of the stopbands were measured at 1.18 GHz and 3.5 GHz. The measured results have been obtained in a very good agreement with the simulations. [ABSTRACT FROM AUTHOR]

In this work, an ultra-wide stopband low-pass filter (LPF) is proposed using tapered step impedance resonators. The distributed equivalent of the proposed step impedance LPF is extracted, analyzed, and legitimated with simulated and fabricated results. The fabricated prototype has a 3 dB cut-off frequency (fc) of 2.92 GHz and an ultra-wide stop band extended up to 25.7 GHz (8.8fc) with an attenuation level of >20 dB. The transition bandwidth (from 3 to 20 dB) is 0.20 GHz and the roll-off factor is 112 dB/GHz (a reference to 30 dB). The passband insertion loss is 0.32 dB at 1.5 GHz and the normalized circuit size of the filter is 0.055. [ABSTRACT FROM AUTHOR]

A new design approach to achieve compact size and high common‐mode (CM) suppression of balanced filters is proposed with two back‐to‐back microstrip semi‐circular patch resonators. In feeding structures, metalized via holes are adopted to vertically feed patches by differential pairs. Then, TM11 mode is excited and TM31 mode can be rejected, resulting in wideband differential‐mode (DM) harmonic rejection. Besides, with a slotline etched in the common ground plane, desired coupling strength can be achieved for a target bandwidth. Meanwhile, by virtue of the stacked structure, source‐load coupling can be easily introduced to generate transmission zeros close to the passband. With theory guidance, two balanced filter prototypes centered at 2.4 GHz are designed. Simulation and measurement results both indicate that proposed balanced filters exhibit high DM and CM performances as well as a compact size about 0.26λg × 0.53λg. [ABSTRACT FROM AUTHOR]

A self‐equalized linear‐phase microstrip bandpass filter (BPF) utilizing negative group delay (NGD) parallel‐coupled three‐line (PCTL) units is presented in this letter. The NGD PCTL unit possesses an NGD valley in its frequency response of group delay (GD). By a combination of two or more NGD valleys, the sharp positive GD peaks at passband edges of a conventional coupled‐line BPF are counterbalanced, resulting in a linear phase response over the entire passband. A prototype of linear‐phase BPF in S‐band is designed by replacing two coupled‐line units in a three‐pole conventional BPF with the proposed NGD PCTL units. Measured passband GD fluctuation of the BPF utilizing NGD PCTL units is 0.5 ns while that of the BPF using conventional coupled‐line units is 1.7 ns, a considerable improvement of 70.5% is achieved with no increase in overall time delay. The out‐of‐band suppression is well retained, and the circuit size is 0.18 λg2. [ABSTRACT FROM AUTHOR]

Low loss and compact wideband filtering power dividers (WB‐FPDs) with/without notch band are proposed. The WB‐FPDs are designed using wideband bandpass filter based on asymmetric stepped‐impedance resonator (SIR). Parallel coupled microstrip lines are used to create both wideband filtering characteristic and two additional transmission poles. A notch band can be generated at upper passband edge by using open‐circuited stubs on the SIRs. The WB‐FPDs with/without notch band are successfully designed, fabricated, and tested. The wide passband is centered at 4 GHz with the fractional bandwidth (FBW) of 51.1%, while the notch band is at 5.56 GHz with the FBW of 3.1%. Good agreement between the simulated and measured results is observed. [ABSTRACT FROM AUTHOR]