Multipath Coupling Research Articles

A Simple Single‐Layer Wideband Filtenna With Multiple Controllable Radiation Nulls

ABSTRACTIn this letter, a single‐layer wideband filtenna with multiple controllable radiation nulls is presented. The developed filtenna has a very simple structure and is composed with a square substrate integrated waveguide (SIW) cavity, a square patch, and a pair of U‐shaped slots. Notably, the filtenna possesses three radiation nulls that can be tuned by adjusting specific geometrical parameters. To achieve a wide bandwidth and better frequency selectivity, the TM10 mode of the square patch is utilized to couple with the TE210 mode of the square SIW cavity. And a radiation null at upper and lower edge of the passband can be simultaneously obtained because of the effective multipath coupling and the impact of TE110 mode in SIW cavity. An extra in‐band resonance and out‐of‐band radiation null are concurrently introduced by etching a pair of U‐shaped slots at the metal ground plane so as to further expand the bandwidth and enhance the frequency selectivity. To validate the design method, a prototype of the filtenna operating at center frequency of 4.76 GHz was fabricated and measured. The measurement results show an impedance fractional bandwidth of 15.8% (4.38‐5.13 GHz) and a peak realized gain of 6.1dBi.

A Novel Dual-Polarized Filtering Dipole Antenna Based on Multipath Coupling

A Novel Dual-Polarized Filtering Dipole Antenna Based on Multipath Coupling

Isogeometric flutter analysis of a heated laminated plate with and without cutout

Understanding the flutter characteristics of heated laminated plates, both with and without cutout, is crucial. This study presents the first exploration of flutter analysis in a thermal environment for a laminated plate featuring a cutout. To facilitate this study, the motion equations of the heated laminated plate with a cutout are derived using the first-order shear deformation theory (FSDT), incorporating a nonlinear term. Employing the isogeometric method combined with multi-path coupling technology, we establish accurate geometric and solution domains for the laminated plate. The effects of the thermal stresses and the aerodynamics calculated by the linear piston theory are considered. The accuracy and effectiveness of the proposed model are validated through several comparisons with ANSYS results and existing solutions. Additionally, the study examines the impact of key parameters on flutter characteristics, including thermal conditions, number of layers, lay-up angles, inflow angles, and cutout dimensions. The insights gained from this research will serve as a valuable benchmark for future analyses and design concerning flutter characteristics.

A dual‐band reconfigurable filtering antenna using PIN diodes for WiMAX and WLAN applications

The realization of a compact dual band reconfigurable filtering antenna is described for WiMAX and WLAN application through this communication. First and foremost, a dual band filter is offered employing four open ended half wavelength Stepped Impedance Resonators (SIRs) to resonate at 3.2 GHz and 5.35 GHz. PIN diodes have been connected to the edges of the innermost resonators to switch the operation from dual passband to two different single passbands and to all stop configuration. Multipath coupling helps to create transmission zeroes on either side of passband enriching the selectivity. In order to implement the filtering antenna, a compact monopole antenna is presented using two triangular radiating patches radiating at 3.2 GHz and 5.35 GHz. Finally, the filter and the antenna structures are combined to accomplish the proposed dual band reconfigurable filtering antenna. The results with reference to return loss and radiation pattern are provided and good performances are obtained. The suggested filtering antenna has the reflection coefficient lower than −16 dB for all the desired operating bands. As well, it offers gain of about 3.21 dBi and 5.08 dBi at the two radiating bands. The developed prototype is fabricated and measured to examine the anticipated and simulated results where a close agreement is established between them.

Blueprint for a High-Performance Fluxonium Quantum Processor

The technological development of hardware heading toward universal fault-tolerant quantum computation requires a large-scale processing unit with high performance. While fluxonium qubits are promising with high coherence and large anharmonicity, their scalability has not been systematically explored. In this work, we propose a superconducting quantum information processor based on compact high-coherence fluxoniums with suppressed crosstalk, reduced design complexity, improved operational efficiency, high-fidelity gates, and resistance to parameter fluctuations. In this architecture, the qubits are readout dispersively using individual resonators connected to a common bus and manipulated via combined on-chip RF and DC control lines, both of which can be designed to have low crosstalk. A multi-path coupling approach enables exchange interactions between the high-coherence computational states and at the same time suppresses the spurious static ZZ rate, leading to fast and high-fidelity entangling gates. We numerically investigate the cross resonance controlled-NOT and the differential AC-Stark controlled-Z operations, revealing low gate error for qubit-qubit detuning bandwidth of up to 1 GHz. Our study on frequency crowding indicates high fabrication yield for quantum processors consisting of over thousands of qubits. In addition, we estimate low resource overhead to suppress logical error rate using the XZZX surface code. These results promise a scalable quantum architecture with high performance for the pursuit of universal quantum computation.

A compact single‐layer wideband filtering antenna with capacitively loaded short‐circuited parasitic patches

AbstractA compact single‐layer wideband filtering antenna with a simple structure is presented in this letter. It consists of a rectangular driven patch, a pair of short‐circuited parasitic patches, and two pairs of rectangular slots. A short‐circuited parasitic patch is employed to capacitively load at each radiating edge of the driven patch to enhance the impedance bandwidth and facilitate filtering response. Based on this arrangement, a radiation null at the upper stopband is generated due to the effect of multipath coupling so as to improve the upper stopband frequency selectivity. Moreover, two pairs of slots are etched into the driven patch to produce an in‐band resonance and a radiation null at the lower‐band edge to further broaden the impedance bandwidth and enhance the lower stopband frequency selectivity. A prototype of the developed filtering antenna with a center frequency of 4.96 GHz is fabricated and tested for validation. The measured values are consistent with the simulated ones, indicating a wide impedance bandwidth of 16.5% (4.55–5.37 GHz), and a maximum realized gain of 6.3 dBi. Compared with the previously reported filtering antenna, the developed filtering antenna can achieve a wideband filtering response even with a low profile of 0.026λ0 and a small antenna size of 0.19λ02.

A Tunable Microstrip Bandpass Filter with Two Concurrently Tuned Transmission Zeros

In this paper, an electrically small tunable microstrip bandpass filter with two concurrently tuned transmission zeros (TZs) is presented. The filter consists of two coupled resonators and varactors as tuning elements. An application of a multipath coupling network results in TZs on both sides of the passband. The filter controlled by a single voltage has a wide tuning range from 370 MHz to 800 MHz and a low insertion loss ranging from 1.9 dB to 3.4 dB. To achieve high attenuation in the stopband, two sections of the designed filter were cascaded. Both one-section and two-section filters were validated by measurements. The obtained results are in a very good agreement with simulations.

A Novel Active Control Strategy with Decentralized Decoupling and Wavelet Packet Transformation: Design and Verification

Active vibration control (AVC) can solve many vibration problems. However, structural vibration in underwater vehicles often involves other factors such as complex excitation and path coupling, etc. At present, the traditional algorithm (e.g., multi Filtered-x Least Mean Square, M-FxLMS) usually cannot effectively process the multi-frequency excitation and the coupling effects of the multi-secondary path, which will affect its convergence and stability to a certain extent. Consequently, a novel strategy is presented in this paper, namely, the wavelet packet transformation decentralized decoupling M-FxLMS algorithm (WPTDDM-FxLMS), which can solve the structural vibration problems mentioned above. The multi-frequency control is converted into a single-frequency line spectrum control, and the feedback compensation factor is introduced in the identification of the secondary path, both of which can simplify the multi-path control system to the parallel single-path systems. Furthermore, the WPTDDM-FxLMS algorithm is applied to the AVC in a multi-input and multi-output system (MIMO) vibration platform. Finally, the simulation and experiments show that the wavelet packet can decompose the multi-frequency excitation into a line spectrum signal, and the improvement of the decentralized decoupling and the variable step-size can effectively reduce the computation amount and increase the convergence speed and accuracy. Overall, the novel algorithm is significant for multi-path coupling vibration control. It will have certain engineering application value in underwater vehicles.

Balanced Dual-Band Superconducting Filter Using Stepped-Impedance Resonators With High Band-to-Band Isolation and Wide Stopband

A balanced dual-band and wide-stopband high-temperature superconducting (HTS) bandpass filter (BPF) with deep stopband rejection is designed using modified stepped impedance resonators (SIRs) in this brief. The center frequencies of the two differential-mode (DM) passbands can be controlled by adjusting two electrical length ratios of the proposed SIR, while keeping the third spurious frequency far away for wide-stopband design. An inherent common-mode (CM) suppression can also be obtained due to the discriminating CM resonant frequencies different from the DM ones. Multiple transmission zeros (TZs) are achieved to realize high passband selectivity and enhanced DM stopband by multipath coupling and shunt stubs loaded on the I/O ports. The proposed balanced dual-band filter operating at 1.78/4.0 GHz is eventually fabricated using HTS YBCO thin films on a MgO substrate, which can significantly lower the insertion losses. The circuit was measured at the temperature of 77 K, which shows maximum insertion losses of 0.42/0.37 dB and a DM stopband of 5.0f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sup> with 40-dB attenuation, respectively.

Compact tunable dual/Tri‐band bandpass filters with multiple zeros

Here, compact dual/tri-band bandpass filters (BPFs) with tunable passbands are proposed. The multiband BPFs are designed by combining a BPF with tunable passband and a BPF with fixed passband using a common external coupling line. The former consists of a dual-mode resonator loaded with varactors (DMVLR) and the latter is composed of a quad-mode resonator (QMR). The classical analysis method of odd/even mode is employed to analyse the characteristics of the resonators. The centre frequency (CF) of the tunable passband can be easily tuned by varying the voltage imposed on the varactors. A constant absolute bandwidth (CABW) is obtained over the whole tuning range of frequency by properly adjusting loading positions of the varactors. The single and dual-passband BPFs with fixed passband are obtained by designing the parameters of QMR appropriately. Simulation and measurement results show that the proposed BPFs are of high selectivity, and the resultant filters are of compact size. In addition, the proposed multiband BPFs have four transmission zeroes (TZs). There are two self-adaptive TZs on both sides of the tunable passbands, which are generated by the multipath coupling structure.

Suppression of multi-path couplings in scaled-down experiment for cross-borehole pulse radar

A scaled-down experiment using cross-borehole pulse radar was performed in a laboratory to extract a more precise decision rule for detecting an intrusive manmade tunnel in Korea. To minimize the total size, a scaled-down model of an air-filled tunnel in underground rock was replaced by a cylindrical ceramic rod in pure water. When the upper arm of a sleeve-dipole antenna of the scaled-down cross-borehole pulse radar was directly connected to a coaxial cable, the measured B-scan data were contaminated by unwanted striped patterns that were generated by multipath coupling. Such multipath coupling between the sleeve-antenna pair was generated by the glass-tube-guided waves. To suppress the glass-tube-guided waves, the coaxial cable was clad in ferrite cores. As the total length of the ferrite-core cladding was increased up to 150 mm, the unwanted multipath couplings were gradually suppressed, and the target signature could be more clearly recognized.

COMPACT TRI-BAND BANDPASS FILTER BASED ON HYBRID RESONATOR WITH IMPROVED SELECTIVITY PERFORMANCES

A novel microstrip tri-band bandpass filter is proposed and implemented using hybrid resonator with independently controllable center frequencies and good in-between isolation. This hybrid resonator is constructed by a stepped-impedance stub resonator and a single end shorted resonator. The stepped-impedance stub resonators are applied to achieve the first and second passband, while the third passband is implemented by single end shorted resonators. By applying the even-odd mode approach, the resonance frequency ratio between even mode and odd mode inside the stepped-impedance stub resonators is attained. Furthermore, the filter with multi-path coupling structure can generate the transmission zeros at the edge of the passband, which can effectively improve the filter passband selectivity. Finally, a tri-band filter operating at 1.91, 2.73, and 3.45 GHz is designed and fabricated. The measurement results accord well with the full-wave electromagnetic designed responses.

Compact High-Temperature Superconducting Filter Using Multimode Stub-Loaded Resonator

A simple multimode resonator loaded by open- and short-end stubs is proposed in this paper. Its transmission characteristics and equivalent circuit models are investigated by even-odd mode analysis. In addition, the multiband filter design theory using the proposed resonator is explained, and the desired passbands can be conveniently allocated by properly choosing the dimension parameters of the stub-loaded resonator. For demonstration purposes, a compact high-temperature superconducting (HTS) filter operating at 1.57, 2.6, and 3.50 GHz is designed and fabricated. To sharpen the passband skirts of the filter, a source-load coupling configuration with interdigital structure is arranged to produce several transmission zeros. Then, multipath coupling diagrams are constructed, and the relative phase shifts of each path are studied to explain the responses of the triple-band filter. Furthermore, a grounding technique of the short-end stub is realized by subtly connecting with the metal wall packaging instead of via holes in the substrate. In consideration of the inaccuracy in HTS fabricating and packaging, an optimization scheme is proposed. The results of the sensitivity analysis revealed that the optimization scheme is viable. Finally, measurements are in good agreement with the electromagnetic simulations and verify the circuit design methodology.

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

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.

Analysis and Design of Superharmonic Injection-Locked Multipath Ring Oscillators

Frequency dividers can be modeled as superharmonic injection-locked oscillators. We propose a general model for ring-oscillator based dividers. Theoretically, the maximum division frequency of a frequency divider can be decoupled from the number of phases at its output when multipath coupling of ring oscillators is used. Accurate expressions for the locking range are derived that are used to find the optimum structure to maximize the division frequency. The results of the model are incorporated into a design procedure that can rapidly explore various coupling and sizing of the multipath structure. A design of a divider chain for a 48-Gb/s serializing transmitter is used as a demonstration.

On the Efficiency of Load Modulation in RFID Systems Operating in Real Environment

The performance of UHF-RFID systems are particularly exposed to environmental effects, such as multipath propagation and electromagnetic coupling. This sensitivity to the electromagnetic properties of the environment is peculiar of systems operating in the UHF band and therefore has not been completely investigated, since many RFID systems still work at HF frequencies. In this letter, the possible impairments due to the most usual environmental effects are considered, with particular reference to the impact on the bit error rate (BER) at the reader side in the Uplink stage of the RFID system.

Design and Development of Advanced Cavity-Based Dual-Mode Filters Using Low-Temperature Co-Fired Ceramic Technology for $V$-Band Gigabit Wireless Systems

In this paper, a novel concept of 3-D integrated -band dual-mode cavity filters, which permit the realization of a variety of quasi-elliptic responses by creating transmission zeros, has been demonstrated using multilayer low-temperature co-fired ceramic (LTCC) technology. A single-cavity resonator is designed to generate a degenerate resonance of two orthogonal modes ( and ), enabling dual-mode operation. The appearance and elimination of transmission zeros have been analyzed through the multipath coupling diagrams and lumped-element models. The quasi-elliptic dual-mode filters with the appropriate locations of the transmission zeros are then developed for receiver and transmitter channels of a -band transceiver module. Two pre-synthesized, dual-mode cavity filters are vertically stacked with two types of inter-coupling slots (1: rectangular, 2: cross) to realize the multipole filters for 60-GHz wireless local area network narrowband applications. These proposed filters are the first to be reported and have great potential to be integrated into miniaturized -band LTCC transceiver modules.

Critique of the Multipath Model for 1J(C,C) Nuclear Spin-Spin Coupling via Electron Current Induced by 13C Nuclear Magnetic Dipoles

Maps of ab initio electronic current density induced by the permanent magnetic dipole moment of 13 C are reported for three saturated hydrocarbons: ethane, cyclopropane, and bicyclobutane. The plots are interpreted via the Biot-Savart law of classical electromagnetic theory by analysing the effects of the magnetic field induced by the current distribution at the site of spin-coupled carbon nuclei. It is shown that, within the proposed model, the significant variation in magnitude and sign of 1 J(C,C) characterising these three molecules can be related to different topological features of the current density vector field. The general pattern can be rationalised in terms of orbital hybridisation of the coupled carbon atoms: 1 J(C,C) does not appear to be significantly affected by the multipath coupling processes usually suggested in the literature.

Compact microstrip narrowband bandpass filter using multipath coupling configuration

A novel compact microstrip narrowband bandpass filter (BPF) with a multipath coupling configuration is presented. Using the proposed topology, the filter has two transmission zeros on both sides of the passband and has low insertion loss. The simulated results agree well with the measured results. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 543–544, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21043

Non-empirical calculations of NMR indirect carbon-carbon coupling constants. Part 8--monocycloalkanes.

Carbon-carbon and carbon-hydrogen spin-spin coupling constants were calculated in the series of the first six monocycloalkanes using SOPPA and SOPPA(CCSD) methods, and very good agreement with the available experimental data was achieved, with the latter method showing slightly better results in most cases, at least in those involving calculations of J(C,C). Benchmark calculations of all possible 21 coupling constants J(C,C), J(C,H) and J(H,H) in chair cyclohexane revealed the importance of using the appropriate level of theory and adequate quality of the basis sets. Many unknown couplings in this series were predicted with high confidence and several interesting structural trends (hybridization effects, multipath coupling transmission mechanisms, hyperconjugative interactions) were elucidated and are discussed based on the present calculations of spin-spin couplings.