Showing papers on "Waveguide filter published in 2014"

An ultra-wideband surface plasmonic filter in microwave frequency

Abstract: We propose an ultra-wideband plasmonic waveguide based on designer surface plasmon polaritons (DSPPs) with double gratings. In such plasmonic metamaterials, the DSPP waves in the region of lower frequencies of the dispersion curve can be tightly confined and hence effectively broaden the operating bandwidth. Based on such features, we design and fabricate a high performance DSPP filter, in which a transducer consisting of microstrip, slotline, and gradient corrugations is employed to feed electromagnetic energies into the plasmonic waveguide with high efficiency. The simulated and measured results on reflection and transmission coefficients in the microwave frequency demonstrate the excellent filtering characteristics such as low loss, wide band, and high square ratio. The high performance DSPP waveguide and filter pave a way to develop advanced plasmonic integrated functional devices and circuits in the microwave and terahertz frequencies.

Substrate Integrated Waveguide Filter: Basic Design Rules and Fundamental Structure Features

Abstract: The electromagnetic (EM) spectrum is becoming more crowded, and it is densely populated with various wireless signals and parasitic interferers in connection with communication and sensing services. Increasingly sophisticated radio-frequency (RF), microwave, and millimeter-wave filters are required to enable the selection and/or rejection of specific frequency channels. This will occur in future generations of the wireless system, such as the current hotly debated fifth-generation communication systems, where the spectral channelization of a heterostructured wide-band signals will be critical in support of a host of coexisting bandwidths or speeds and applications. Bandpass filters have been the most useful and popular types for such applications and are the most difficult to design and develop in practice. Other types of filters such as notch (stopband) and lowpass filters have also been widely used in many systems, and their design is generally perceived less critical with respect to band-pass filters. This article will focus on the presentation and discussion of bandpass filters. Design factors or parameters of filters, such as selectivity, cost, miniaturization, sensitivity to environmental effects (temperature and humidity, for example), and power handling, combined with predefined in-band and out-of-band performance metrics, are critical specifications of the design with respect to the development of RF and microwave front ends. This is indispensable for the efficient utilization of frequency spectrum resources and the cost-effective enhancement of wireless system performances.

Substrate Integrated Waveguide Filters: Design Techniques and Structure Innovations

Abstract: Because of the inherent structural flexibility in coupling design and topological arrangement, substrate integrated waveguide (SIW) filter topologies enjoy better out-of-band frequency selectivity and/or in-band phase response with the allocation of finite transmission zeros (FTZs). In the first article in this series, basic design rules and fundamental electrical characteristics have been presented that indicate the superior performances of SIW structures and their filter applications. Advanced design techniques and innovative structure features have recently been reported in a large number of publications. They include cross couplings realized by physical and nonphysical paths and SIW filters with dual-mode or multimode techniques. Miniaturization-enabled techniques including low-temperature cofired ceramic (LTCC) technology have been developed and applied to the development of SIW filters to reduce the size for low-gigahertz applications using nontransverse electromagnetic (non-TEM) modes. Wideband SIW filters, multiband SIW filters, and reconfigurable SIW filters have also been reported by various research groups. This article reviews these advanced and innovative SIW filter technologies, and related examples are presented and discussed.

Novel Multi-Stub Loaded Resonators and Their Applications to Various Bandpass Filters

Abstract: This paper presents a new class of multi-stub loaded resonators with flexibly controlled resonance modes, which are suitable for both tunable and nontunable filter applications. The proposed resonators, modified from a basic tri-mode resonator, include two quad-mode ones and a six-mode one. One of the quad-mode resonators is utilized to design a reconfigurable dual-band filter with tunable lower passband and fixed upper passband. The other quad-mode resonator is applied to design a bandpass filter (BPF) with very high skirt selectivity. The six-mode resonator is suitable for tri-band BPFs with individually controllable passband frequencies and bandwidths. All three circuits are theoretically analyzed and experimentally demonstrated. Comparisons of the measured and simulated results are presented to verify various applications of the resonators.

Compact Triple-Mode Filter Based on Quarter-Mode Substrate Integrated Waveguide

Abstract: An isosceles right triangular waveguide with one electric wall and two magnetic walls is proposed to design a triple-mode filter implemented in a substrate integrated waveguide. The complete closed-form modal solutions are presented for both transverse electric and transverse magnetic modes in the isosceles right triangular waveguide. The resonant frequencies of a resonator made of a short isosceles right triangular waveguide can then be calculated. A structure called a quarter-mode substrate integrated waveguide (QMSIW) is introduced to realize the proposed triangular waveguide resonator in a compact and planar form. Simulated electric field distributions of modes excited in the QMSIW are in good agreement with theoretical predictions for the solid waveguide structure, demonstrating the feasibility of QMSIW resonators. Finally, a compact triple-mode filter is designed and fabricated based on the discussed QMSIW. The frequency responses and group delay of the filter are tested, and measured results agree very well with simulated ones. This demonstrates that the proposed QMSIW structure is an excellent candidate for compact triple-mode filters.

Quarter-Wavelength Stepped-Impedance Resonator Filter With Mixed Electric and Magnetic Coupling

Abstract: This letter proposes a new type of microstrip quarter-wavelength stepped-impedance resonator (SIR) filter with controllable mixed electric and magnetic coupling. A conducting pin and an open gap between two coupled SIRs are jointly used to create the mixed coupling, and the electric and magnetic coupling can be separately controlled by adjusting the spacing between the gap and the position of the conducting pin. Based on the proposed structure, a second-order filter and a third-order filter are designed and fabricated. Good agreement between the measured and simulated data is obtained.

Asymmetric band-pass plasmonic nanodisk filter with mode inhibition and spectrally splitting capabilities.

Abstract: A compact wavelength band-pass filter based on metal-insulator-metal (MIM) nanodisk cavity is proposed and numerically investigated by using Finite-Difference Time-Domain (FDTD) simulations. It is found that the transmission characteristics of the filter can be easily adjusted by changing the geometrical parameters of the radius of the nanodisk and coupling distance between the nanodisk and waveguide. By extending the length of input/output waveguides, the filter shows the resonant mode inhibition function. Basing on this characteristic, a two-port wavelength demultiplexer is designed, which can separate resonant modes inside the nanodisk with high transmission up to 70%. The waveguide filter may become a potential application for the design of devices in highly integrated optical circuits.

Microstrip Line Negative Group Delay Filters for Microwave Circuits

Abstract: This paper presents a novel approach to the design and implementation of a distributed transmission line negative group delay filter (NGDF) with a predefined negative group delay (NGD) time. The newly proposed filter is based on a simple frequency transformation from a low-pass filter to a bandstop filter. The NGD time can be purely controlled by the resistors inserted into the resonators. The performance degradation of the NGD time and signal attenuation (SA) of the proposed NGDF according to the temperature dependent resistance variation is also analyzed. From this analysis, it is shown that the NGD time and SA variations are less sensitive to the resistance variation compared to those of the conventional NGD circuit. For an experimental validation of the proposed NGDF, a two-stage distributed microstrip line NGDF is designed, simulated, and measured at an operating center frequency of 1.962 GHz. These results show a group delay time of -7.3 ns with an SA of 22.65 dB at the center frequency and have good agreement with the simulations. The cascaded response of two NGDFs operating at different center frequencies is also presented in order to obtain broader NGD bandwidth. NGDFs with good reflection characteristics at the operating frequencies are also designed and experimentally verified.

Reconfigurable Waveguide Filter with Variable Bandwidth and Center Frequency

Abstract: This paper presents a center frequency and bandwidth reconfiguration mechanism for waveguide microwave bandpass filters. The filters are designed to be used in the output section of a satellite communication system. While the center frequency of a bandpass filter can be tuned by changing the lengths of the filter resonators, the coupling irises as practical realizations of the impedance inverters cannot easily be adapted to a new value. The novel approach chosen in this paper is to replace the impedance inverters by a novel type of coupling structure. This coupling structure allows adjustment of the coupling by changing the length of a transmission line, which is equivalent to changing the resonant frequency of a coupling resonator. Design equations are presented to transform an impedance inverter into the proposed coupling structure. A synthesis procedure for bandwidth reconfigurable filters is proposed. The feasibility of coupling adaptation is proven based on a full-wave model of the coupling structure. The synthesis process is applied to a four-pole Chebyshev sidewall-coupled circular waveguide filter with 54- and 72-MHz bandwidth settings. The filter is built up and measured. The measured results prove that the filter can be tuned to both bandwidths over a center frequency range of 200 MHz with excellent return loss and insertion loss.

LTCC Multilayered Substrate-Integrated Waveguide Filter With Enhanced Frequency Selectivity for System-in-Package Applications

Abstract: This paper presents a cross-coupled bandpass filter with stacked substrate-integrated waveguide cavities on low-temperature cofired ceramic substrates. The proposed filter has a local multipoint distribution service band with a novel same-side-feed input/output structure. Conventionally, a cross-coupled structure generates only a single pair of transmission zeros. The proposed filter can generate two pairs of transmission zeros beside the passband, thereby providing an excellent cutoff rate in the stopband and improved frequency selectivity. The additional pair of transmission zeros is created by the same-side-feed structure, which constructs an additional source-load coupling path without increasing the circuit size. A multipath coupling diagram is used to illustrate the conformation of the second pair of transmission zeros and predict its behavior. The experimental filter exhibits responses centered at 27.95 GHz with an insertion loss of -2.8 dB, and a bandwidth of 9%. Two pairs of transmission zeros (at 26.3 and 29.6 GHz, and at 23.2 and 37 GHz) around the passband were obtained, achieving excellent selectivity and a wide stopband.

A Planar Bandpass Filter Implemented With a Hybrid Structure of Substrate Integrated Waveguide and Coplanar Waveguide

Abstract: In this paper, a novel planar bandpass filter is proposed, designed, and implemented with a hybrid structure of substrate integrated waveguide (SIW) and coplanar waveguide (CPW), which has the advantages of good passband and stopband performance inherited from SIW and miniaturized size accompanying with the CPW. Additional design flexibility is introduced by the hybrid structure for efficiently controlling the mixed electric and magnetic coupling, and then planar bandpass filters with controllable transmission zeros and quasi-elliptic response can be achieved. Several prototypes with single and dual SIW cavities are fabricated. The measured results verified the performance of the proposed planar bandpass filters, such as low passband insertion loss, sharp roll-off characteristics at transition band, etc.

Direct-Coupled Cavity Filter in Ridge Gap Waveguide

Abstract: This paper describes a novel design for a direct-coupled cavity filter realization using a ridge gap waveguide technology. A ridge gap waveguide transmission line with two coaxial feed connectors is designed and operated within the frequency band of 10-13 GHz. A cavity is coupled to the transmission line to achieve bandstop filter characteristic. Then, the structure of the filter is modified in a way to generate a bandpass feature. The final manufactured prototype is a fourth-order bandpass filter, operating at the center frequency of 11.59 GHz with a bandwidth of 72 MHz. The proposed design has potential applications in channeling filters for telecommunication satellites.

Dielectric waveguide filter with direct coupling and alternative cross-coupling

Abstract: A waveguide filter comprising a base block of dielectric material defining at least first and second resonators and a bridge block seated on top of the base block and defining at least a third resonator. In one embodiment, the base block comprises first and second base blocks that have been coupled together in an end to end relationship. An external transmission line or an interior RF signal transmission window or an RF signal transmission bridge provides a cross-coupling RF signal transmission path between the first and second resonators. At least first and second interior RF signal transmission windows provide a direct RF signal transmission path between the first and third resonators and the second and third resonators respectively.

Balanced Substrate Integrated Waveguide Filter

Abstract: A novel balanced filter realized in the form of substrate integrated waveguide (SIW) is proposed and studied in this paper. Based on the inherently horizontal and vertical symmetry of the SIW, this filter presents inherently high-performance balanced property with advantages of no identical pair requirement, being free from the limitation of symmetrical topology, easy and flexible design, high common-mode (CM) suppression, and robust CM suppression when comparing with conventional counterparts. Several prototypes are designed, fabricated, and measured to verify the expected properties.

Substrate Integrated Waveguide Filters: Practical Aspects and Design Considerations

Abstract: In the current literature, the majority of research work reported on substrate integrated waveguide (SIW) filters has focused on the development of physical topologies as well as design and realization techniques for filter specifications and electrical parameters. The practical and successful implementation of SIW filters requires special consideration of mechanical and thermal properties during the design and processing stages. These properties include the effects of ambient operating environment, average, and peak power-handling capabilities as well as design and production economics, including labor costs, skilled labor availability, mass-production issues, and projected production delivery rates [1]. Bandpass filters are more concerned with those practical aspects as their in-band and out-of-band performance are much more sensitive than other types of filters to those mechanical and thermal issues.

A Generalized Coupling Matrix Extraction Technique for Bandpass Filters With Uneven-Qs

Abstract: In this paper, a vector fitting (VF) based analytical extraction method, which is capable of accurately extracting the coupling matrix and the uneven unloaded Qs of each electric resonators of a filter, is presented. Having had the complex poles and residues determined using VF, the coupling matrix can be obtained by a sequence of complex orthogonal transformations. As a side product, the unloaded Qs for each resonator will be directly obtained from the complex diagonal elements of the coupling matrix. To demonstrate the effectiveness of the proposed method, an ideal demonstrative example along with two practical challenging filter tuning examples, namely, an eight-pole dual-mode dielectric filter and an eight-pole dual-mode predistortion filter, are demonstrated. An excellent match between the responses of the measured data and those from the extracted coupling matrix with actual unloaded Q factors can be seen.

Tuned to Resonance: Transfer-Function-Adaptive Filters in Evanescent-Mode Cavity-Resonator Technology

Abstract: A number of promising technologies can be found today in the marketplace of reconfigurable filter ideas. They range from sub-mm-scale acoustic filters, lumped elements, two-dimensional resonators, and full three-dimensional solutions. From a system perspective, an equally diverse pool of communication, radar, electronic warfare, and sensing systems need reconfigurable filters. Despite a strong demand for such filters though, it is not easy to identify a technology that satisfies all requirements. While it is relatively straightforward to satisfy one or two important specifications such as low loss or high selectivity, it is often quite challenging to simultaneously satisfy all of them. For instance, this is particularly true when low power consumption, small form factor, and low loss become simultaneously critical decision factors. Several combinations of such factors can result in necessary design tradeoffs with no obvious solutions. Table 1 summarizes several common deciding factors in selecting a reconfigurable filter technology.

Compact Dual-Mode Wideband Filter Based on Complementary Split-Ring Resonator

Abstract: This letter proposes a microstrip filter based on a dual-mode complementary split-ring resonator (DMCSRR). For the input/output coupling, a dual C-shaped feed structure is implemented together with the DMCSRR to acheive a wideband response. The resonator offers a wide fractional bandwidth of 62% at the central frequency of 2.23 GHz and a very compact structure with a footprint of 0.0625λg×0.18λg, where λg is the guided wavelength at the midband frequency. A comprehensive lumped element circuit analysis accompanies the simulation and measurement results.

Novel Bandpass Filters by Using Cavity-Loaded Dielectric Resonators in a Substrate Integrated Waveguide

Abstract: This paper presents novel bandpass filters by using a triple-mode dielectric resonator (DR) implemented in a substrate integrated waveguide (SIW). The resonant frequency and unloaded Q-factor of the DR were first calculated and simulated by Ansoft HFSS. The dimensions of the DR were then determined. A single triple-mode SIW loaded with a DR filter with tuning elements was designed, simulated, and measured. Spurious suppression with source and load couplings, as well as fabrication tolerance, was analyzed. A six-mode filter that uses two DRs was also proposed and measured. These filters exhibit close agreements between the simulation and measurement results and have the advantages of low insertion loss, compact configuration, and easy integration with other planar circuits. The proposed concept is very attractive for designing low cost, low insertion loss, and miniaturized filters for wireless communication systems.

Low insertion loss 61 GHz narrow-band filter implemented with Groove Gap Waveguides

Abstract: This paper presents a 61 GHz narrow-band filter, implemented with Groove Gap Waveguide (GGW) coupled resonators. This structure does not require metal contact on the side walls and, therefore, is very suitable for mm-wave applications. At these frequencies, the manufacturing process imperfections become important, and an appreciable response deterioration can be found using classical microwave waveguides, such as the rectangular waveguide. The presented filter is a 5 pole Chebyshev filter, having 2,5% relative bandwidth. An important novelty in this design is the integration of the coaxial feeding in the bottom metal piece, which allows even more manufacturing flexibility. The remarkable good results in terms of insertion losses (15 dB), and return losses (13 dB), of the fabricated prototype endorse this technology as a serious solution for the mm-wave band.

Design of compact dual-band bandpass filter using dual-mode stepped-impedance stub resonators

Abstract: A dual-band bandpass filter (BPF) using a novel stepped-impedance stub resonator (SISR) is presented. The proposed SISR is found to have the advantage that the even-mode resonant frequencies can be flexibly controlled, whereas the odd-mode resonant frequencies are fixed. Based on the proposed SISR, a dual-band filter is implemented by tuning its geometric parameters. To improve the selectivity, a filter with four transmission zeros on either side of both passbands is designed by introducing a 0° feeding structure. A prototype of a dual-band BPF centred at 1.84 and 2.65 GHz has been designed and fabricated. The measured results validate the full-wave EM simulated results.

A High-Selectivity Tunable Dual-Band Bandpass Filter Using Stub-Loaded Stepped-Impedance Resonators

Abstract: A novel varactor tunable dual-band bandpass filter (BPF) using stub-loaded stepped-impedance resonators is proposed in this letter. Compared with the traditional tunable filters, the source-load coupling and T-shape stub-loaded lines are employed in this design. The proposed BPF architecture has the advantages of high selectivity and less control voltages. In the overall tuning range, the proposed filter is designed with 5–6 transmission zeros and more than 30 dB rejection between the two passbands. Meanwhile, only one control voltage is needed for each passband. A prototype of this filter is fabricated and measured. The measurement results show great agreement with simulated results, which show that the first passband can be tuned in a frequency range from 0.8 to 1.02 GHz, and the second passband varies from 2.02 to 2.48 GHz.

A 23–35 GHz MEMS tunable all-silicon cavity filter with stability characterization up to 140 million cycles

Abstract: A connectorized RF MEMS tunable two-pole band-pass filter is demonstrated as the first all-silicon evanescent mode cavity filter operating in the K-Ka band. All filter components are fabricated with cost-effective silicon micromachining techniques. The filter's poles are controlled by two micro-corrugated MEMS diaphragms that are engineered to be independently controlled with voltages below 140 V. Advanced fabrication techniques are applied for the first time to ensure independent pole-frequency control with no additional filter loss and improved fabrication accuracy and stability. The filter's measured tuning range is from 23 GHz to 35 GHz (0-140 V) with fractional bandwidth ranging from 0.8% to 4%. The filter's measured loss varies from 4.2 to 1.5 dB including its connectors. The extracted filter quality factor varies from 530 to 750. The maximum actuation voltage of 140 V is 2× lower than previous demonstrations for similar tuning ranges. The filter's stability has been tested up to 140 million cycles (0-70 V cycling) with no failures observed. The filter exhibits a burn-in period of about 40 million cycles. The filter provides a stable behavior after the initial burn-in period.

A Linear Phase Filter in Quadruplet Topology With Frequency-Dependent Couplings

Abstract: This letter presents a design of a linear phase microwave bandpass filter. The filter is composed of four resonators arranged in the quadruplet topology. Making the cross and one direct coupling dispersive gives additional design flexibility. The first advantage of using frequency-dependent couplings is the possibility to chose an arbitrary location of a pair of complex transmission zeros (TZs) in the s-domain. The second one is the presence of an additional imaginary transmission zero that improves the filter selectivity. We provide a proof-of-concept design of a filter using substrate integrated waveguide (SIW) technology. The frequency-dependent couplings are implemented in SIW as a composition of both: an inductive part realized in a form of an H-plane iris and a capacitive part realized as a grounded coplanar waveguide (GCPW). The measured filter characteristics prove the validity of the model.

A Self-Equalized Waveguide Filter With Frequency-Dependent (Resonant) Couplings

Abstract: This letter presents a design of a fifth-order linear phase filter with frequency-dependent couplings. The filter is composed of a triplet that is directly coupled to two resonators at the input and output. To provide group delay flattening a cross-coupling in the trisection has a strongly dispersive character with a negative slope parameter. To achieve this, an E-plane stub with a septum was used. To further improve the filter selectivity, the direct couplings connecting the triplet to the outer resonators are also frequency dependent. In this particular case, these were implemented in the form of two partial-height conducting posts to provide two imaginary transmission zeros, one on each side of the stopband. With three strongly dispersive couplings, four zeros were obtained in a fifth-order topology that generates only one imaginary transmission zero in a classical design. The filter was realized in the WR-90 waveguide and the measured characteristics match the simulated ones, confirming the validity of the concept.

A Novel Dual Mode Dual Band SIW Filter

Abstract: In this article, a novel dual mode dual band substrate integrated waveguide (SIW) filter is presented. Dual band operation of the filter is realized by providing two paths for the input signal to the output port. The signals of two paths have opposite sign and equal amplitude at a frequency between two bands and hence, a transmission zero is generated in this frequency. The dual mode resonator is a square SIW cavity perturbed by corner cut. A three-cavity dual mode dual band filter is designed using coupling matrix. Frequency response of the filter obtained from the coupling matrix is in good agreement with the full wave simulation result.

Cascaded trisection substrate-integrated waveguide filter with high selectivity

Abstract: A cascaded trisection substrate-integrated waveguide bandpass filter with better frequency selectivity is presented. The proposed coupling scheme can be divided into two trisection topologies. By changing the signs of coupling coefficients between cascaded resonators, two transmission zeros can be simultaneously placed at the higher or lower stopband, or one can be located below and the other above the passband. A filter sample is designed and fabricated with standard single-layer printed circuit board technology. The measured S-parameters agree well with the simulated counterparts, and good performance of the filter is predicted.

Very compact photonic crystal resonant cavity for all optical filtering

Abstract: In this paper, an all-optical filter is proposed which employs a resonant cavity localized between input and output waveguides as wavelength selecting part of the filter. We study the impact of different parameters on the filtering of the structure using plane wave expansion and finite difference time domain methods. We also study the effect of the output waveguide position on the performance of the filter and results show that the proper position of the output waveguide is straight to the center of the resonant cavity. The initial form of filter is capable of selecting the optical waves at λ = 1,554.2 nm and the transmission efficiency of the filter is obtained about 100 %. The total footprint of the filter is <76 μm2. High transmission efficiency, simplicity of design and compact size are the most significant advantages of filter.

Design of a Compact Dual-Band Bandpass Filter Using Coupled Stepped-Impedance Resonators

Abstract: A compact dual-band bandpass filter (BPF) using coupled three-section stepped-impedance resonators (SIRs) has been proposed and analyzed in this letter. By its symmetrical merit, the even-odd mode analysis method is used to obtain the input admittance of its bisection circuits. After the Richard's transformation, each bisection circuit is derived as an equivalent LC circuit. Combining these two LC circuits, the equivalent circuit for the proposed filter is built with its design parameters as a function of even-/odd-mode impedances of the coupled SIR. The proposed circuit is then classified into two distinctive parts, a transversal structure for the first two resonances and a Π-shaped inductor network for the mutual coupling between the source/load. Thus, there are two reflection zeros appearing in each passband and five transmission zeros (TZs) generated to improve the out-of-band rejection. A prototype dual-band filter has been designed and fabricated to verify the predicted filtering performance and the accuracy of the presented design principle.

New Microstrip Bandpass Filter Designs Based on Stepped Impedance Hilbert Fractal Resonators

Abstract: The proposed microstrip bandpass filters in this paper have compact sizes and narrow band responses which are the requirements of modern wireless communication circuits. These filters are constructed from dual-edge coupled resonators; each resonator is based on applying step impedance resonator generator on first and second iteration of Hilbert fractal resonators on each segment of each iteration level. They have been designed for the industrial, scientific, and medical band (ISM) band applications at a centre frequency of 2.4 GHz using a substrate with a dielectric coefficient of 9.6 and thickness of 0.508 mm. The performance of bandpass filters has been analysed using a method of moments (MoM) based on software package, Microwave Office 2009, from Advanced Wave Research Inc., which is widely adopted in microwave research and industry. Simulation responses show that these filters possess good frequency response characteristics with second harmonics suppression. Moreover, these filters showed noti...