Negative Coupling Structure Research Articles

A high-performance, temperature-stable Mg1.99Ga0.01Si0.99Al0.01O4-CaTiO3 microwave dielectric ceramic and its 5 G/6 G waveguide filter

New ultra-low loss, temperature-stable composite ceramics, (1-x) Mg1.99Ga0.01Si0.99Al0.01O4-xCaTiO3, have been developed with a view to expanding the portfolio of low-cost, MW dielectrics available for 5 G/6 G telecommunications, currently dominated by 95 wt%MgTiO3-5 wt%CaTiO3, (Mg,Ca)TiO3 (relative permittivity, εr ∼ 21, quality factor, Q×f ∼ 56,000 GHz and temperature coefficient of resonant frequency, τf ∼ 0 ppm/°C). Compared with (Mg,Ca)TiO3, 89 wt%Mg1.99Ga0.01Si0.99Al0.01O4-11 wt%CaTiO3 ceramics are also temperature stable (τf = −2.72 ppm/°C) but have lower εr (∼8.55) and a higher Q×f (∼ 72,900 GHz @ 12 GHz and 80,900 GHz @ 26 GHz), better suited to the higher frequencies earmarked for 6 G millimeter-wave (mm-wave) applications. To demonstrate its potential for 5 G/6 G telecommunications, a waveguide filter with novel negative coupling structure was fabricated based on simulated results. The filter had low insertion loss (0.43 dB) at the center frequency (4.8 GHz) and high selectivity with a roll-off rate of 576/375 dB/GHz. The S-parameters matched well at 25 °C and 85 °C, demonstrating that the filter had excellent temperature stability and was therefore suitable for future 5 G/6 G microwave and mm-wave communication devices.

Design of a microwave filter based on a novel negative coupling structure with conical through-hole

This article introduces the design theory of ceramic waveguide filter and proposes a new type of negative coupling structure with a conical through-hole, which has fine-adjustment of negative coupling without significantly increasing the insertion loss of the filter. Based on this, the article proposes an eight-cavity ceramic waveguide filter design for 5G base stations. It also presents a detailed discussion on the influence of the cross-coupling slot lengths L2 and L4 on the transmission zeros positions during the filter optimization process and the relevant change rules. For the proposed optimized filter, the observed performance indicators include the center frequency of 3.5 GHz, working bandwidth of 200 MHz, an insertion loss of ≤ 2.0 dB, return loss of ≥ 19 dB, and out-of-band near-end suppression and out-of-band far-end suppression of ≥ 39 dB and ≥ 63 dB, respectively. The test performance results obtained for the sample, with structural parameters as per the simulation model, were in good agreement with the simulation results.

Negative Interresonator Coupling Structure Enclosed in Waveguide Resonator Filter

This work presents a new negative interresonator coupling structure that can be applied to circular waveguide resonators, such as substrate-integrated waveguide (SIW) resonators and metallic cavity resonators utilizing the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">011</sub> mode. The negative coupling is obtained by using the fact that the magnetic field in the resonator circulates in the opposite directions in the upper and lower half parts. As it can be entirely enclosed within a filter structure, it does not produce radiation loss. For verifying the proposed negative coupling structure, we have designed and fabricated a fourth-order bandpsss filter having a pair of transmission zeros using SIW resonators. In addition, the proposed negative coupling structure can be applied to the metallic waveguide cavity resonator filters. Hence, we also have designed, fabricated, and measured a fourth-order metallic cavity bandpass filter having a pair of transmission zeros by adopting the proposed negative coupling structure.

Compact substrate integrated waveguide rat‐race filtering couplers with arbitrary angular interval between ports

A new type of compact filtering rat-race couplers with arbitrary port direction based on different shape substrate integrated waveguide (SIW) cavity are first proposed in this paper. Different shaped SIW resonators can be combined together to achieve better performance and flexible topology. Resonant frequencies of fan-shaped SIW cavity with various central angles have been derived to construct the resonant cells and obtain different topological structures. Moreover, interdigital capacitor SIW unit loaded on the common wall between cavities is used to achieve negative coupling structure. The detailed analysis and the design method have been introduced to realize a filtering rat-race coupler based on substrate integrated fan-shaped cavity (SIFC) and rectangular cavity. In particular, the combination of different shaped resonators can be selected according to the requirement of port angle interval. In order to further verify the method, the other filtering rat-race coupler is fabricated using four SIFCs to achieve more available port angle intervals. Compared with other filtering couplers, the proposed designs exhibit good filtering responses, high Q factor, amplitude balance, as well as 0° and 180° phase differences. Furthermore, various angular intervals for input/output ports are convenience to meet the requirement of system topology and interconnect.

New negative coupling structure and its application on substrate integrated waveguide bandpass filters

To design cross-coupled substrate integrated waveguide (SIW) bandpass filters (BPFs) with high performance, a new negative coupling structure is proposed, which is constructed by two coupled lines with shorted ends. The negative coupling structure is analyzed in detail. The stracture which can realize both relatively weak and strong negative coupling strength. The optimization method based on characteristic polynomials and reference zeros and poles of scattering parameters is realized for the filter design. To verify the proposed negative coupling structure, two fourth-order cross-coupled SIW BPFs with the center frequency of 10 GHz based on the optimized coupling matrixes are designed. The first one has a normalized bandwidth of 3% with a negative coupling in one cross-coupling path to illustrate the realization of weak negative coupling strength, and the second one has a normalized bandwidth of 8% with a negative coupling in one main coupling path to illustrate the realization of strong negative coupling strength. Finally, the two BPFs are fabricated and measured. Simulation and measurement results are in good agreement, which demonstrates the feasibility of the proposed negative coupling structure and its application on cross-coupled SIW filters with high performance. The influence of weak disperse cross coupling on locations of transmission zeros is also discussed.

Miniaturized bandpass filter design using substrate integrated waveguide cavities with enhanced signal selectivity

AbstractWe propose a miniaturized bandpass filter (BPF) design with enhanced signal selectivity performance. The proposed structure is composed of four square substrate integrated waveguide cavities (SIWCs). To miniaturize its circuit size, the applied cavities are under the evanescent mode resonance which is accomplished by loaded itself with a large capacitance. As a result, a 93.4% size reduction is achieved. The negative coupling structure is employed in the filter design to create two transmission zeroes by the pass band's two edges for enhancing the signal selectivity. Experiment is conducted to verify this compact SIWC BPF design.

New Negative Coupling Structure for ${K}$ -Band Substrate-Integrated Waveguide Resonator Filter With a Pair of Transmission Zeros

In this letter, we present a new negative coupling structure applicable to a substrate-integrated waveguide (SIW) resonator filter structure. Unlike conventional negative coupling structure, the proposed coupling structure can achieve a negative coupling value without employing an additional substrate or slots on ground planes. To demonstrate the new negative coupling structure, we designed, fabricated, and measured a fourth-order ${K}$ -band SIW resonator filter with a pair of transmission zeros.

Design and Multiphysics Analysis of Direct and Cross-Coupled SIW Combline Filters Using Electric and Magnetic Couplings

In this paper, combline substrate integrated waveguide (SIW) filters using electric and magnetic couplings are thoroughly studied. Thus, a negative coupling scheme consisting on an open-ended coplanar probe is proposed and analyzed in detail. Several in-line 3-pole filters at C-band are designed, manufactured and measured showing how the presented approach can be used for implementing direct couplings while enabling an important size reduction and improved spurious-free band compared to conventional magnetic irises. A fully-packaged quasi-elliptic 4-pole filter is also designed at 5.75 GHz showing how the negative coupling structure can be used for introducing transmission zeros by means of cross-couplings between non-adjacent resonators. Finally, average and peak power handling capabilities of these filters have been also analyzed from a multiphysics point of view. Measured results validate the theoretical predictions confirming that combline SIW filters can handle significant levels of continuous and peak power, providing at the same time easy integration, compact size and advanced filtering responses.

V-band cross-coupled SIW band-pass filter with an antisymmetric U-slot negative coupling structure

This study presents an low-temperature cofired ceramic (LTCC) V-band cross-coupled band-pass filter using substrate-integrated waveguide cavities. Two antisymmetric U-shaped slots connected by via is proposed to construct the negative coupling structure, which is simple and especially useful for 60 GHz applications. Moreover, the U-slot structure possesses a wide range of realizable coupling coefficients from −0.008 to −0.075. An experimental LTCC fourth-order filter was fabricated for demonstration, achieving a bandwidth of 12% (7.2 GHz) at 59.6 GHz with superior frequency selectivity.

NEW NEGATIVE COUPLING STRUCTURE FOR SUBSTRATE-INTEGRATED CAVITY RESONATORS AND ITS APPLICATION TO DESIGN OF AN ELLIPTIC RESPONSE FILTER

This paper presents a new type of a negative coupling structure for designing elliptic-response fllters with cross-coupling. The proposed coupling structure consists of short-circuited coupled transmission lines. Using the fact that insertion phase of the coupled line structure is difierent from that of an inductive iris, it is shown that the proposed coupling structure can be used as the negative coupling structure. In order to verify the proposed coupling structure, we designed a 4th-order cross-coupled elliptic-response bandpass fllter with substrate integrated waveguide resonators. A pair of transmission zeros in measurement and simulation results validates that the proposed structure can be used as the negative coupling structure.

Folded substrate integrated waveguide cross‐coupled filters with negative coupling structure for wireless systems

AbstractIn this article, a compact multilayer substrate integrated filter with pseudoelliptic power transfer function is presented. The fourth‐order bandpass filter designed by optimization has a central frequency of 10 GHz with a bandwidth of 800 MHz. It possesses two transmission zeros and exhibits return loss of −30 dB. Miniaturization is achieved using folded waveguide technology. Novel negative coupling structure based on upside–down‐folded iris‐coupled resonators is introduced and investigated. Design procedure is briefly explained, coupling matrix is derived, and investigation of coupling elements is carried out to match calculated coupling coefficients. Results of full‐wave simulation of the filter are in good agreement with the prototype. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2521–2526, 2011; Published online in View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26341

Substrate Integrated Waveguide Cross-Coupled Filter With Negative Coupling Structure

Substrate integrated waveguide (SIW) technology provides an attractive solution to the integration of planar and nonplanar circuits by using a planar circuit fabrication process. However, it is usually difficult to implement the negative coupling structure required for the design of compact canonical folded elliptic or quasi-elliptic cross-coupled bandpass filter on the basis of a single-layer SIW. In this paper, a special planar negative coupling scheme including a magnetic coupling post-wall iris and a balanced microstrip line with a pair of metallic via-holes is studied in detail. Two -band fourth-degree cross-coupled bandpass filters without and with source-load coupling using the negative coupling structures are then proposed and designed. The two novel SIW filters having the same center frequency of 20.5 GHz and respective passband width of 700 and 800 MHz are implemented on a single-layer Rogers RT/Duroid 5880 substrate with thickness of 0.508 mm. Measured results of those filters, which exhibit a high selectivity, and a minimum in-band insertion loss of approximately 0.9 and 1.0 dB, respectively, agree well with simulated results.