Dual-mode Resonator Research Articles

Compact 60-GHz On-Chip Bandpass Filter With Low Insertion Loss

In this letter, a compact 60-GHz on-chip bandpass filter is presented using an integrated passive devices technology on a GaAs substrate. An E-shaped dual-mode resonator and stepped impedance resonator were adopted in this design for a compact size and sharp cut-off response. Two controllable transmission zeros are obtained on the both sides of the passband achieving a good frequency selectivity. The main size of the filter is only $0.58 \times 0.4$ mm2. The presented filter has a center frequency of 60 GHz, with a 3 dB fractional bandwidth of 14.8 GHz from 52.6 to 67.4 GHz. The insertion loss of the filter is only 1.2 dB, and the return loss is lower than −10 dB within the passband. Good agreement is achieved between the measured results and the simulated ones.

A Compact Coupled-Fed Loop Antenna for Mobile LTE Smartphones

A coupled-fed loop antenna with Octa-bands operation for long-term evolution (LTE) smartphones is proposed in this paper. The antenna occupies a nonground space of only 6.5 mm × 72 mm, and two wide-band operations can be achieved by exploiting the multimode characteristics of loop antenna and using high-pass matching circuits. In low band, the LTE700/GSM850/900 operation is achieved by the loop mode of 0.5 λ and matching chip capacitor which generates a dual-resonance mode at 0.74 GHz and 0.9 GHz. In high band, the 1 λ mode, the 1.5 λ mode, and the 2 λ mode of the entire loop are combined with the 0.5 λ mode of the left-side coupling loop to cover the DCS1800/PCS1900/UMTS 2100/LTE 2300/2500 operation bands. The measured average realized gains and efficiencies are approximately 1.56 dBi/2.38 dBi and 55.3%/63.6% in the two bands, and a good radiation pattern is achieved as well.

Electronically switchable compact quad-band microstrip bandpass filter using varactor perturbed dual-mode resonators

In this paper, an electronically switchable quad-band microstrip bandpass filter is designed using varactor perturbed dual-mode resonators. For this purpose, four meandered dual-mode square loop resonators (DMSLRs) having reference patches are nested and varactor diodes are used to serve as perturbation elements. The designed resonator is analyzed by deriving even/odd mode resonance conditions. S-parameters are also calculated according to the even and odd mode input impedances. Stub loaded feedlines are used to couple the DMSLRs to Input/Output (I/O) ports. According to the capacitances of varactor diodes, each passband can be independently turned on and off. Coupling scheme and coupling matrix of the designed filter are introduced to realize the coupling descriptions. Switching operations are also investigated over the frequency responses obtained from coupling matrix. Passbands of the filter are adjusted to 1.4, 1.7, 2.25, and 2.7 GHz. The designed filter was also fabricated and measured results show a good agreement with the simulated and theoretical results.

Single mode to dual mode switch through a THz reconfigurable metamaterial

Metamaterials interact with incident electromagnetic waves through their consisting subwavelength metamolecules. In this paper, we reported a reconfigurable metamaterial which tunes its THz response experimentally from a single mode resonance at 2.99 THz to a dual mode resonance at 2.94 THz and 2.99 THz. The reconfiguration is realized through a micromachined actuator, and the tunability is achieved by breaking the symmetry of the metamolecule. An abrupt change in the transmission is experimentally observed when the gap between two metallic structures is closed, and a decrease in transmission from 40% to 5% at 2.94 THz is obtained. Such a tunable metamaterial promises widespread applications in optical switches, filters, and THz detectors.

A Microwave Microfluidic Sensor Based on a Dual-Mode Resonator for Dual-Sensing Applications.

In this paper, we propose a novel microwave microfluidic sensor with dual-sensing capability. The sensor is based on a dual-mode resonator that consists of a folded microstrip line loaded with interdigital lines and a stub at the plane of symmetry. Due to the specific configuration, the resonator exhibits two entirely independent resonant modes, which allows simultaneous sensing of two fluids using a resonance shift method. The sensor is designed in a multilayer configuration with the proposed resonator and two separated microfluidic channels—one intertwined with the interdigital lines and the other positioned below the stub. The circuit has been fabricated using low-temperature co-fired ceramics technology and its performance was verified through the measurement of its responses for different fluids in the microfluidic channels. The results confirm the dual-sensing capability with zero mutual influence as well as good overall performance. Besides an excellent potential for dual-sensing applications, the proposed sensor is a good candidate for application in mixing fluids and cell counting.

Biomineral Nano-Theranostic agent for Magnetic Resonance Image Guided, Augmented Radiofrequency Ablation of Liver Tumor

Theranostic nanoparticles based on biocompatible mineral compositions can significantly improve the translational potential of image guided cancer nano-therapy. Here, we report development of a single-phase calcium phosphate biomineral nanoparticle (nCP) with dual-mode magnetic resonance contrast (T1-T2) together with radiofrequency (RF) mediated thermal response suitable for image-guided RF ablation of cancer. The nanoparticles (NP) are engineered to provide dual MR contrast by an optimized doping concentration (4.1 at%) of paramagnetic ion, Fe3+, which also renders lossy dielectric character for nCP leading to thermal response under RF exposure. In vivo compatibility and dual-mode MR contrast are demonstrated in healthy rat models. MRI and T2 mapping suggest hepatobiliary clearance by ~96 hours. MRI guided intratumoral injection in subcutaneous rat glioma and orthotopic liver tumor models provide clear visualization of NP in MRI which also helps in quantifying NP distribution within tumor. Furthermore, by utilising RF mediated thermal response, NP treated tumor could be ablated using clinically approved RF ablation system (10 W,13.3 GHz). Real-time in vivo thermal imaging exhibits 119 ± 10% increase in temperature change (ΔT) for NP treated orthotopic liver tumor (ΔT = 51.5 ± 2 °C), compared to untreated healthy liver control (ΔT = 21.5 ± 2 °C). In effect, we demonstrate a promising nano-biomineral theranostic agent for dual-mode MRI combined with radiofrequency ablation of solid tumors.

Multilayered stepped impedance loaded-resonator for compact dual-band rejection filter design

ABSTRACTA new compact dual-band rejection filter using multilayered stepped impedance loaded-resonator (SILR) is proposed in this article. The stepped impedance loaded-resonator is a dual-mode resonator. The filter structure is compose of two circuits patterned on three layers using two substrates. On the bottom double layer substrate, two SILRs are designed and coupled to generate and control the bandwidths of the first and second bandstops. To achieve the frequency response of the desired filter, a signal path transmission line is realized on a top single layer substrate and vertically coupled to the bottom substrate circuit. To validate the developed approach, a dual-band rejection filter is designed and fabricated to reject the frequencies of 2.4 GHz WLAN and 3.5 GHz WiMax systems. The simulated and measured responses are in good agreement. The resulted filter offers small size, good isolation passband and high selectivity performance with favourite transmission poles around the desired rejection bands.

A Simple Frequency-Agile Bandpass Filter With Predefined Bandwidth and Stopband Using Synchronously Tuned Dual-Mode Resonator

This letter proposes a novel and simple synchronously tuned dual-mode resonator (STDR) to achieve a frequency-agile bandpass filter (FA-BPF) with predefined bandwidth (BW) location, BW variation, and stopband characteristics. This solution overcomes the difficulty with predefining the BW of previous tunable filter designs. The proposed STDR is controlled by two varactors and a single bias. The two resonant frequencies’ separation of the resonator can be adjusted by changing the varactor loading position and the shorted stub length. Meanwhile, the transmission zero location can be predefined by specifying the corresponding dimensions. Based on the predefined STDR, the FA-BPF can be achieved easily. An FA-BPF with a constant BW is realized to demonstrate such a unique feature. The measurement results of the FA-BPF verify the theory, and also exhibit high selectivity, wide frequency tuning range, and simple design/ control procedure.

Compact superconducting single- and dual-band filter design using multimode stepped-impedance resonator**Project supported by the National Natural Science Foundation of China (Grant No. 61371009) and the Fund from the Chinese Ministry of Science and Technology (Grant No. 2014AA032703).

This study presents two multimode stepped-impedance structures to design single- and dual-band filters. Transmission zeroes are introduced for the single-band filter by using dual-mode stepped-impedance resonators. The single-band filter with high selectivity is centered at 6.02 GHz and has a fractional bandwidth (FBW) of 25.6%. Four stubs (two low frequency and two high frequency ones) are connected to the rectangular patch in the center to construct a quadruplemode resonator. The independent conditions of the center frequencies of the high and low bands of the resonator are analyzed. A dual-band filter, which operates at 1.53 GHz and 2.44 GHz with FWBs of 12.1% and 14.1%, respectively is designed. The single- and dual-band filters are both fabricated with double-sided YBCO films and they can be used in mobile and satellite communications.

Design of Dual-Mode Dual-Band Superconducting Filters

This paper presents a synthesis design method for superconducting dual-mode dual-band filters. A low-pass to dual-band bandpass frequency transformation is proposed based on lossless lumped-element dual-mode resonator circuits. Formulas for extracting the coupling coefficient $k$ and external quality factor $Q_e$ of dual-mode microstrip resonators are derived using the coupling matrix theory and the proposed frequency transformation formula. This makes the design process of dual-mode dual-band filters similar to that of the single bandpass filter. For the demonstration, four dual-band superconducting filters with different dual-mode resonator structures, such as stepped-impedance, stub-loaded, and embedded resonators are designed and fabricated. The measured results match well with the simulations.

8-order filter based on 2-D photonic crystal with dual-mode microstrip resonators

The design of 8-order band-pass filter based on 2-D photonic crystal is suggested. Strip conductors in all dual-mode resonators are in the form of «irregular» rectangular frame with a gap and are connected at certain points with the ground. At optimal placement of such resonators on a substrate attenuation pole is observed on the amplitude-frequency characteristic of the filter, near low and high bandwidth slope that significantly improves its frequency-selective properties. The change of gap between input and output resonators allows to control the frequency of these poles.

A Low-Profile Wide-Bandwidth Planar Inverted-F Antenna Under Dual Resonances: Principle and Design Approach

A low-profile planar inverted-F antenna (PIFA) under the operation of TM0,1/2 and TM2,1/2 modes in a single patch resonator for bandwidth enhancement is proposed. Initially, our study demonstrates that all of the even-order modes can effectively be suppressed by employing a rectangular PIFA instead of the conventional microstrip patch antenna. Then, a pair of shorting pins is appropriately loaded underneath the side-shorted radiating patch to investigate the variation of their odd-mode resonant frequencies. The results indicate that the resonant frequency of TM0,1/2 mode ( $f_{0,1/2}$ ) is dramatically increased up while almost maintaining that of TM2,1/2 mode ( $f_{2,1/2}$ ). After that, the width of the radiating patch is progressively enlarged in order to move the $f_{2,1/2}$ more closely to the $f_{0,1/2}$ . By using this approach, the dual radiative resonant modes can be reallocated in proximity to each other. Additionally, a narrow slot is etched out on the radiating patch so as to counteract the equivalent inductance caused by the shorting pins and probe. As such, a wide-bandwidth with stable radiation pattern is achieved for the PIFA under the operation of these dual-resonant modes. After the extensive analysis is executed, the proposed antenna is fabricated and tested. Simulated and measured results are found in good agreement with each other, demonstrating that its impedance bandwidth is tremendously widened to about 15.3% with appearance of two in-band attenuation poles. In particular, a low-profile property with the height of 0.036 free-space wavelength is achieved.

High-Order Dual-Band Superconducting Bandpass Filter With Controllable Bandwidths and Multitransmission Zeros

In this paper, a compact dual-mode hairpin ring resonator (HRR) with two controllable resonances is proposed to design high-order dual-band high-temperature superconducting (HTS) bandpass filters. Its noncoupled dual-mode resonant characteristics and the mechanism for inherent transmission zero (TZ) production are studied. Moreover, a general dual-path coupling scheme is introduced for high-order coupling realization and applied to the third-order and eighth-order dual-band filter design. Also, two coupling structures for the adjacent HRRs with different orientations are proposed to excite TZs between the passbands for high selectivity. Besides, dual-parallel input–output feeding structure is adopted to tune the external quality factors of the dual-mode HRR individually so that the two passband are realized easily using high-order structure. For demonstration, an eighth-order dual-band HTS filter both operating at 1.9 and 2.6 GHz for mobile communications application are designed and analyzed. Compared with the third-order one, the selectivity of the eighth-order filter has at least 4.2 times improvement and five TZs are produced for high band-edge selectivity. Finally, the eighth-order dual-band filter is fabricated on MgO substrate with YBCO thin films. Measured results agree well with the simulations and show the excellent performance with 0.12-dB minimum insertion loss and better than −75-dB rejection level up to 5 GHz. In addition, the nonlinear characteristics of the fabricated HTS filter is observed by experiment, which shows the temperature dependence of filter center frequency performance and microwave insertion loss.

Design of a filtering power divider with microstrip‐to‐slotline transition structures

A filtering power divider (FPD) with high selectivity is presented. Initially, by elaborately introducing two different types of microstrip-to-slotline transition structures and a pair of dual-mode stub-loaded resonators, dual-mode bandpass response is attained in this design. Afterwards, the resistor R is utilised to achieve high in-band isolation between two output ports of the FPD. Moreover, four transmission zeros are generated outside the passband for high selectivity performance. To validate the feasibility of the new approach, a prototype FPD operating at 3.62 GHz (f 0) is designed, fabricated and measured. Both simulated and measured results are provided in good agreement indicating that the proposed FPD exhibits a better than 20 dB isolation inside the passband and extended upper stopband up to 10 GHz.

Miniaturised highly selective wide‐band bandpass filter using dual‐mode resonators and inter digital capacitors

A wide-band bandpass filter with high selectivity, compact size and wide stopband is presented in this Letter. This proposed filter uses dual-mode resonators (DMRs) as its basic tool. Stepped impedance technique is adopted in designing the DMRs for miniaturising its size. In the construction of filter design, three types of inter digital capacitors (IDCs) are employed; one is used for coupling between DMRs and other two are used at feed lines. The IDCs and open stub resonators are infused in the filter for curbing the harmonics and providing wide stopband. Input–output cross coupling is introduced by making use of hook-shaped feed lines for achieving good selectivity. A miniaturised size of 0.089λg × 0.10λg (29.2 × 33 mm2) with wide stopband up to 10.1f 0 (f 0 is the operating frequency of filter) with 21.5 dB harmonic suppression level is achieved with this design.

Self-coupled dual-mode ring resonator with turning transmission zeros in microwave bandpass filter for planar metamaterial: analysis and design

An H-shape dual-mode closed resonator with self-coupled segments is reported. The self-coupling between ring segments renders an equivalent mode perturbation effect as the normal ways of adding stub, cutting notch, or varying line impedance to the ring resonator. The mode perturbation and transmission-zero generation from the self-coupling effect and step-impedance were analyzed using the even–odd mode theory. By regulating the impedance ratio and coupling coefficients of self-coupled sections, the self-coupled ring resonator can produce either the capacitive or inductive perturbation. The input and output positions affect the number and locations of transmission zero. The positions of input and output ports are properly selected. In the capacitive perturbation case, when the two transmission zeros are located on both sides of the passband, and bring about a pseudo-elliptic bandpass response. The analysis of finding optimized taping positions of input and output ports is proposed. Comparing to the regular uniform ring resonator, the H-shaped self-coupled ring resonator has shorter ring length, is easily to be folded and does not destroy the dual-mode characteristics. The feature of compact size is favorable in the design of a bandpass filter. A 2.45-GHz bandpass filter based on the H-shaped self-coupled ring resonator was performed to verify the proposed theory. A schematic bandpass filter was implemented with a compact size which is only 20% of the conventional dual-mode bandpass filter.

In brief

PAGE 1192 Researchers in Korea have developed a bi-directional deformable block-based motion-estimation algorithm for accurate motion prediction in 360-degree videos. A significant improvement in visual quality is demonstrated with this approach in comparison to conventional motion estimation techniques. The proposed algorithm can be used for virtual reality applications, motion estimation and frame-rate up conversion. PAGE 1180 Researchers in Australia have fabricated a non-invasive optical sensor for measuring knee movement in 3D space. The triangular sensor works by measuring the angle-of-arrival of optical signals and is integrated with a 2D image processing procedure. The reported sensor is shown to measure knee movement with a high precision that is within the clinically acceptable limit. Improved visual quality in 360-degree videos using a new motion-estimation algorithm. PAGE 1200 The development of sensors for rapid detection of hydrogen gas is currently a hot topic in renewable fuel research. Work from Korea proposes a Pt-functionalised hydrogen sensor developed on an AlGaN/GaN-on-Si heterostructure platform. The sensor was demonstrated to have high sensitivity and a rapid detection response time of 3 seconds in 4% hydrogen concentration. A novel non-invasive sensor design for measuring knee movement. PAGE 1203 A Decoupled Empty-Substrate Integrated Waveguide (DESIW) has been made by researchers in Spain. The DESIW design is a continuous conductive metal structure that enables AC/DC decoupling with integrated devices, reducing unwanted power losses. Measured scattering and transmission parameters show that the design is highly competitive with alternative technologies. The authors present a new hydrogen sensor with rapid detection response time. PAGE 1226 Lens-based millimeter-wave massive MIMO is a key technique for improving data transfer rates and efficiencies in 5G wireless communications. Work from China introduces an adaptive neighbourhood search algorithm for beam selection, which reduces the energy consumption and hardware costs in mm wave MIMO based systems. The proposed beam selection approach achieves near optimal performance with low complexity. A novel DESIW has been designed and manufactured to improve AC/DC decoupling efficiencies. PAGE 1178 The ability to control a wheelchair's movement through the act of thinking has been achieved by researchers in China. The design is controlled by a wireless dry EEG headset acquisition system and has five steering behaviours controlled by the brain-computer interface. A new adaptive neighbourhood search algorithm for efficient beam selection in 5G wireless technology is proposed. PAGE 1169 Work from China proposes a new approach to providing an antenna for slim electronic devices. Using the existing infrastructure of a laptop computer, the design integrates ground-planes and metal hinges to achieve high radiation efficiency without the physical presence of an antenna structure. The proposed design reduces the physical space taken up by an antenna with reduced manufacturing costs. Five steering behaviours are reported in a newly designed brain-controlled wheelchair. PAGE 1196 The reconstruction of images using compressive sensing can produce restoration precision errors resulting in blurring and low resolution. Researchers in China have developed a compressive sensing algorithm that uses a vector quantisation error to suppress the described precision errors. Experimental results demonstrate the algorithm outperforms previously reported compressive sensing methods in aspects of perception and peak signal-to-noise ratios. Designing an antenna within the hinges of slim electronic devices. PAGE 1209 The miniaturisation of a wideband bandpass filter is achieved using stepped impedance by researchers in India. The device also incorporates dual-mode resonators and three types of inter digital capacitors to achieve frequency selectivity. The authors demonstrate the device to display wide stopband properties suitable for terrestrial trunked radio applications. Vector quantisation error parameters are used to remove precision errors in compressive sensing methods. PAGE 1174 Work from Turkey presents a novel design of C-band Fabry-Perot resonator antenna with improved impedance and bandwidth gaining radiation characteristics. The active element of the antenna is a square patch with four crossing points. The antenna is reported to be suitable for a broad range of applications including satellite communication. A miniaturised wideband bandpass filter has been designed with functional frequency selectivity. A new Fabry-Perot resonator antenna design is proposed for satellite communication applications.

100 GHz waveguide band-pass filter employing UV-LIGA micromachining process

In this paper, a 100GHz rectangular waveguide band-pass filter with two transmission zeros symmetrically located at both ends of pass-band is presented. The four-pole filter with two transmission zeros is composed of two dual-mode resonators with unequal width, two WR-10 standard waveguide interfaces, and three groups of round corner inductive irises in series. The filter is designed and analyzed based on the Synthesis and Simplification Theory of coupling matrix, simulated by using commercial full-wave simulation software HFSS, and fabricated using UV Lithography Technology with SU-8 photo-resist. The specifications of the filter are as follows: 100GHz center frequency with 3.7% fractional bandwidth, the transmission zeros at frequency of 97.75GHz and 102.75GHz respectively to improve the out of band rejection, and return loss which is better than −18dB across the whole pass-band. Results from measurement are in good agreement with simulations considering the inaccuracy of fabrication and measurement. Therefore, the availability of design, analysis, and fabrication methods mentioned in this paper is confirmed.

Dual-Mode Filtering Power Divider With High Passband Selectivity and Wide Upper Stopband

A novel microstrip dual-mode filtering power divider (FPD) is presented in this letter. Stemming from the distinctive voltage distribution along an open-ended one-wavelength ( $\lambda$ ) microstrip line, the dual-mode FPD is initially constructed by utilizing proper coupling topologies between the open-ended transmission line and two dual-mode resonators. Meanwhile, its good isolation performance is attained by introducing an isolation resistor between the two dual-mode resonators. Next, the explicit synthesis method is described to design the proposed FPD with prescribed performance. A prototype FPD at 2.4 GHz is in final implemented and measured. As theoretically expected, this proposed FPD exhibits better than 22-dB isolation within the entire operation band along with 17-dB harmonic suppression up to 7.5 GHz (3.1f0).

Simultaneous Generation of Microwave, Millimeter-Wave, and Terahertz Photonic Signal Based on Two-Color Semiconductor Laser Subject to Single-Beam Optical Injection

In this paper, dual-mode semiconductor laser is presented and demonstrated experimentally based on multimode Fabry–Perot laser diode with a built-in cavity. The spacing of both emission modes can be tuned by adjusting the bias current and operating temperature of active region. The generated dual-mode resonance can give rise to terahertz (THz) photonic signal with more than 300 GHz frequency. Under an external injection mode launched into the two-color semiconductor laser condition, it is possible to simultaneously generate photonic signals with various frequencies, ranging from less than 10 GHz to several THz, by selecting a proper resonance mode as the reference mode of injection beam. In this study, photonic signal including microwave (MW), millimeter-wave (mm-wave), and THz wave whose frequency range is from a few gigahertz to more than 0.5 THz are given, and the corresponding optical spectrum and electrical spectrum for low-frequency MW signal as well as simulated electrical spectrum for high-frequency mm-wave and THz wave signal are presented and discussed in detail.