Stub Resonator Research Articles

A MULTIBAND COMPACT LOW-PROFILE PLANAR ANTENNA BASED ON MULTIPLE RESONANT STUBS

A MULTIBAND COMPACT LOW-PROFILE PLANAR ANTENNA BASED ON MULTIPLE RESONANT STUBS

Analytical Solution of Amplifier-Antenna System’s Impedance Matching Requirement for Reliable Microwave Transmitter

In this paper, the integration of push-pull class B amplifier and antenna module have been proposed. The high efficiency and low distortion of push-pull class B due to its differential feeding technique makes it a viable candidate as a power amplifier. The aperture-coupled antenna structure is used in this work as it offers the designer various methods to effectively adjust the variables thereby making way for more efficient configuration which can be fabricated on system-on-chip. Moreover, this enables a wide range of values that can be chosen on the Smith Chart thus allowing the conditions needed for odd-mode matching to be satisfied. This matching requirement is specific for only a given transistor and in this work by incorporating bandstop filters made of resonant stubs it has been possible to filter harmonic power up to 3rd harmonic. The frequency of operation of the integrated push-pull transmitting amplifier during simulation is at 2.06 GHz. The Wilkinson power divider, power coupler, phase shifter and bias decoupling circuits have been employed so as to efficiently integrate the push-pull class B power amplifier with the differentially fed aperture coupled antenna. Two types of antenna were studied whereby one was designed with the conventional $50~\Omega $ environment while the other makes use of the complex value impedance. Parametric study was also performed on both types of antennas so as to investigate the effects it has on the impedance matching requirements. Finally, the prototype was realized through fabrication and measurements were performed at fundamental frequencies and up to 3rd harmonics to show gain at fundamental component and filtering of 2nd and 3rd harmonic.

A Highly Selective Rasorber Based on Second-Order Resonance

A novel frequency-selective rasorber with one highly selective passband between two absorption bands is presented. Based on the equivalent circuit analysis, the approach of using a second-order band-pass response in the lossless layer is adopted to improve the selectivity of the passband. A two-layered structure consisting of one lossy and one lossless layer is then used for implementation. The lossy layer is constructed using stub resonators, while an aperture-coupled resonator is used to realize lossless layer and achieve the highly selective passband. Under normal incidence, the operating bandwidth of the proposed rasorber is 110.6%. One passband with sharp roll-off edge and small insertion loss (0.08 dB) is achieved at 4.3 GHz. For demonstration, one prototype was fabricated and measured, and a good agreement is observed accordingly.

Miniaturized Ring Resonator Wideband Bandpass Filter with Wide Stop Band

In this paper miniaturized quarter wavelength rectangular shaped multimode ring resonator bandpass filter with extended diagonal corners and internally located high impedance perturbation stubs, is proposed. Input/output open stubs are tightly coupled to the extended diagonal corners running parallel to the two sides of the ring resonator, implemented to generate wide passband and wide stop-band. Cut-off frequencies can be shifted to the higher side by increasing the length of the sides of resonator. By inserting the perturbation stubs, rectangular ring resonator produces three degenerate modes out of which first two form a wide passband. Small square patch is attached to the opposite interior corners of the ring resonator and T-shaped stub attached to the opposite longer side of the resonator are tightly coupled with feeder line to improve the return loss, insertion loss and skirt-characteristics. Shorter sides of the rectangular ring resonator are bent in U-shaped to increase the effective length of the resonator eventually the bandwidth is widened. Filter is designed and simulated for the center frequency of 3.2 GHz, bandwidth from 2.0 GHz to 4.0 GHz, on dielectric constant 3.38 and thickness 0.508 mm. Electromagnetic simulator Ansoft HFSS is used to optimize the filter dimensions.

Miniaturized Ring Resonator Wideband Bandpass Filter with Wide Stop Band

In this paper miniaturized quarter wavelength rectangular shaped multimode ring resonator bandpass filter with extended diagonal corners and internally located high impedance perturbation stubs, is proposed. Input/output open stubs are tightly coupled to the extended diagonal corners running parallel to the two sides of the ring resonator, implemented to generate wide passband and wide stop-band. Cut-off frequencies can be shifted to the higher side by increasing the length of the sides of resonator. By inserting the perturbation stubs, rectangular ring resonator produces three degenerate modes out of which first two form a wide passband. Small square patch is attached to the opposite interior corners of the ring resonator and T-shaped stub attached to the opposite longer side of the resonator are tightly coupled with feeder line to improve the return loss, insertion loss and skirt-characteristics. Shorter sides of the rectangular ring resonator are bent in U-shaped to increase the effective length of the resonator eventually the bandwidth is widened. Filter is designed and simulated for the center frequency of 3.2 GHz, bandwidth from 2.0 GHz to 4.0 GHz, on dielectric constant 3.38 and thickness 0.508 mm. Electromagnetic simulator Ansoft HFSS is used to optimize the filter dimensions.

Miniaturized Chipless RFID Tags Based on Periodically Loaded Microstrip Structure

A compact chipless radio frequency identification (RFID) tag-based on slow-wave technology is introduced in this paper. The tag consists of a resonant circuit based on open stub resonators periodically loaded by shunt stubs allowing a coding capacity of 9 bits and operating in a frequency range from 2 to 4GHz. The receiving and transmitting antennas of the tag are particularly designed to minimize the tag size as much as possible. The proposed tag presents a robust bit pattern with a compact and fully printable structure using FR4 substrate for a low-cost tag.

Phase-coupled plasmon-induced transparency and slow light in graphene stub detuning structures

Tunable phase-coupled plasmon-induced transparency (PIT) and slow light are investigated theoretically and numerically by cascading two stub resonators with a certain distance along the graphene bus waveguide. The theoretical model is analyzed by the coupled mode theory and transfer matrix method. The transmission and slow light effects in the transparent window can be tailored not only by changing the detuning of the two stub resonators but also by adjusting the separation distance L or chemical potential between the two stubs. In addition, multiple PITs and slow light are proposed and simulated with a triple-stub structure. By the numerical simulation, a conclusion is drawn that the added phase coupling can trap the SPPs in the waveguide with longer time, resulting in the slow wave effect more obviously than that with only the detuning coupled method. The proposed slow light structure will pave another way towards dynamic controlling slow light in the terahertz and mid-infrared regimes.

Quad-band bandpass filter based on sextuple-mode and dual-mode stub-loaded resonators

A quad-band bandpass filter (BPF) employing a sextuple-mode and a dual-mode stub loaded resonator are presented in this paper. The proposed sextuple-mode resonator generates the first, second and the fourth passband while the third passband is achieved by the dual-mode open stub-loaded resonator. The proposed sextuple-mode resonator modified from quintuple-mode resonator produces five resonant modes while the sixth-mode is generated by the coupling of the open ends of two stub resonators. Based on the odd- and even-mode analysis of the sextuple-mode resonator, the odd- and even-mode resonant frequencies can be flexibly controlled by tuning the corresponding resonator dimensions. Subsequently, the proposed sextuple resonator is combined with dual-mode open stub loaded resonator to achieve the quad-band BPF, centered at 1.75/2.45/3.50/5.25 GHz. The size of filter is about 0.13λg×0.22λg, where λg is guided wavelength on the substrate at 1.75 GHz. The measured results agree well with the simulated results.

Fork shaped with inverted L-stub resonator UWB antenna for WiMAX/WLAN rejection band

A compact beveled fed inverted L-stub dual-band rejection, ultra-wideband (UWB) radiating antenna is proposed. The antenna consists of the dual fork-shaped radiating elements and inverted L-shaped stub resonators. The fork-shaped radiating elements together with stub resonator occupies a size of 20 × 14 mm2. This antenna accepts an impedance bandwidth (VSWR ≤ 2) of 9 GHz and rejects two narrow interfering WiMAX (3.1 GHz)/WLAN (5.1 GHz) bands. The rejecting frequencies are attained by using an inverted L-shaped stub resonator. The two rejecting frequencies of WiMAX/WLAN bands have an acceptable gain reduction and weak radiation in UWB communication. Therefore, the design is appropriate for WiMAX/WLAN dense environments. Meanwhile, the measured results of the fabricated prototype exhibit a good matching with the simulated results.

Tunable plasmonic-induced transparency based on stub-coupled cascade ring resonator with electro-optical material

The electrical control of plasmonic-induced transparency (PIT) via a resonator waveguide system is presented. The proposed structure is composed of a stub and cascade ring resonator. The ring and the stub resonator are filled with electro-optical material which can control the resonance frequency by the external voltage. Two-dimensional finite difference time domain (2D FDTD) method is used to calculate the transmission and field distribution. Single PIT is investigated both by FDTD and Coupled Mode Theory (CMT). The proposed PIT can be tuned by changing the external voltage or the geometric parameters. Double and triple PIT can be obtained by introducing more ring resonators and can be tuned by external voltage. The proposed plasmonic structure may have application in slow light device, nanoscale filter, all-optical switch and refractive index sensor.

Fano resonance in MDM plasmonic waveguides coupled with split ring resonator

Fano resonance results from the coherent interference between a narrow discrete state and a wide continuous spectrum, which is useful for the integrated optical devices. In this paper, Fano resonance in some ultra compact metal-dielectric-metal (MDM) plasmonic waveguides is studied in detail. The structures are composed of a bus waveguide, a stub resonator, a split ring resonator (SRR), or an SRR connected to a tooth resonator (TSRR). The simulation results indicate that the two Fano resonances FR1 and FR2 can be excited, which are sensitive to some of the structural parameters and the refractive index of the dielectric medium in SRR and TSRR. A novel and interesting result is that, for the TSRR, when the rotation angle of its connected tooth cavity is 90° or 45°, the independent tunability of the resonant wavelength of the two Fano resonances can be achieved. In addition, as for the application of refractive index sensor, the sensitivity and the figure of merit (FOM) are both higher. Due to the sharp change of transmission phase shift, larger dispersion will accompany with the Fano resonance. It is shown that the maximum group index can be larger than 14 with optical delay time of about 0.1ps. So the proposed waveguide structures may be suitable for the applications of nanoscale filters, refractive index sensors, and slow-light devices and so on.

Double Fano resonances based on different mechanisms in a MIM plasmonic system

In this paper, a metal-insulator-metal (MIM) waveguide structure consisting of two identical stub resonators and a rectangular cavity is designed. Two-dimensional finite-difference time-domain (FDTD) method is used to study the performances of the proposed structures. According to the simulation results, the transmission spectrum exhibits two typical sharp Fano peaks. One of them originates from the interaction between the strong trapped resonance in the Fabry-Perot (FP) resonator and the weak resonance in the stub resonators, while the other results from the interference between the narrowband spectrum generated by the rectangular cavity and the broadband spectrum provided by the stub resonators. Based on the different mechanisms, the two Fano resonances can be adjusted independently through changing the parameters of the structure. Besides, multiple Fano peaks are also achieved by adding an extra rectangular cavity. An analytic model based on scattering matrix theory is provided to explain the phenomenon. The results reveal potential applications of the coupled system in the field of sensors.

Investigation of integrated solid state nano‐ionic metal–insulator–metal switches for electronically reconfigurable band‐stop filter applications

A proof of concept of application of Nano-Ionic Conductive-Bridging Metal-Insulator-Metal (MIM) switches in electronically reconfigurable band stop filters, through design, and experimental results are presented in this article. Two similar designs of band stop filters with different mechanism of operation are proposed herewith. One is a microstrip, resonant open stub based band stop filter and the other is a microstrip tuned shorted stub based band stop filter. Electrical length of the stubs in both these devices are tuned by an integrated MIM switch forcing them to resonate at different frequencies and thus achieving electronically switchable band stop filtering characteristics. Working mechanism of the devices is validated with the help of developed electrical equivalent circuit models. Analysis on time stability of switch states for 1000 minutes with affirmative results is also presented herewith. These devices are fabricated without any soldered electrical components and without the use of any clean room technologies, using proven low cost method, and are promising to work at very-low power and have the potential to be directly printed on low cost flexible substrates like paper, for potential disposable applications.

Frequency- and Bandwidth-Tunable Absorptive Bandpass Filter

In this paper, an analytic design method for a frequency- and bandwidth-tunable absorptive bandpass filter is introduced. The presented design method relies on the transformation from the normalized absorptive low-pass filter prototype to a bandpass filter structure with parallel resonators and admittance inverters. The inverter values for producing a predefined frequency response are given in closed-form expressions so that a filter design needs no heuristic approach and can be carried out in an analytic manner. This work also presents a new tunable stub resonator structure capable of changing not only its resonant frequency but also the slope parameter. As the slope parameter can be adjusted, it is allowed to use static inverters in designing a filter whose bandwidth can be tuned. For demonstrating our design method for a reconfigurable absorptive bandpass filter, a third-order filter having the target to have the frequency tuning range from 1.35 to 1.65 GHz and the bandwidth tuning range from 5% to 10% has been designed and measured.

A high capacity tunable retransmission type frequency coded chipless radio frequency identification system

This article presents a 12-bit frequency coded chipless RFID system in the frequency range of 3 to 6 GHz. The system consists of a fully printable chipless tag and a pair of high-gain reader antennas. The tag also incorporates its own antennas to improve the read range. Information is encoded into frequency spectrum using a multi-resonant circuit. The circuit consists of multiple microstrip U and L-shaped open stub resonators patterned in a unique configuration. The proposed configuration aids in capturing more data in a reduced space as well as tunable frequency operation. Tag and reader antennas utilize techniques such as stepped impedance feeding line, defective partial ground plane, and stair-step patch structure to achieve wide-band impedance bandwidth in miniature size. The results of the wireless measurements in the non-anechoic environment show that the proposed system has a reading range of more than 20 cm. The presented system possesses great potential for low-cost short-range inventory tracking.

Novel Absorptive Balanced Bandpass Filters Using Resistive Loaded Transmission Lines

This paper reports on design of novel balanced bandpass filters (BPFs) using quarter-wavelength stub resonators. For the design purposes, differential-mode (DM) and common-mode (CM) half-equivalent circuits are established and analyzed carefully. In this paper, CM noise is introduced into the filter and dissipated on the resistors on periodic bands. First, a balanced BPF topology based on conventional quarter-wavelength stub filter is presented. By symmetrically introducing series matching resistors to the ground at the center of the stub, CM noise can be rejected either reflectively or reflectionlessly without affecting DM performance. The harmonic property of stubs provides periodic CM suppressing response as long as the resistor has no serious parasitic reactance. By doing so, CM noise can be suppressed under a certain level at all frequencies. However, the harmonic property also leads to some spurious passbands. This defect can be avoided by an improved filter topology with two additional capacitors. To reserve the CM feature, the corresponding DM and CM half equivalent circuits are developed as well. The proposed layouts are fabricated on a two-layer printed circuit board. The resulting experimental circuits exhibit the expected electrical performance, forming balanced BPFs with CM noise suppression level over 12 dB at all frequencies, and show an agreement with the simulated results.

Terahertz multi-band unidirectional reflectionless phenomenon in a MIM plasmonic waveguide system based on near-field coupling

Dual-band unidirectional reflectionlessness is investigated in a system consisting of three stub resonators side-coupled to a metal-insulator-metal plasmonic waveguide based on near-field coupling in terahertz domain. Reflectivities of [Formula: see text] and [Formula: see text], respectively, at two exceptional points 4.11[Formula: see text]THz and 4.695[Formula: see text]THz are obtained for forward (backward) direction. More than that multi-band unidirectional reflectionlessness is demonstrated based on multi-stub resonators side-coupled to an MIM plasmonic waveguide.

Wide Stopband Bandpass Filter Implemented by Stepped Impedance Resonator and Multiple In-Resonator Open Stubs

Stepped impedance resonator (SIR) has been widely used for applications in wide stopband bandpass filters. However, the reported SIR wide stopband bandpass filters are limited in either stopband performance or design complexity. Here we propose an approach to improve the stopband performance and reduce the design complexity simultaneously. Two in-resonator open stubs are adopted in a SIR (with tap-feeding) to stagger the frequencies of higher-order modes (compared with other SIR) and produce two adjustable transmission zeros without affecting the fundamental properties. For a SIR filter employing such a structure, the spurious passbands are doubly deteriorated by the staggering and up to four transmission zeros. At the same time, the fundamental passband is not affected, which significantly reduces the design complexity. As a result, not only wide stopband but also high-suppression stopband can be obtained in a simple design. A prototype based on the substrate integrated coaxial line (SICL) is experimented showing an impressive stopband performance. Agreeing with the simulation well, the measured stopband is extended up to about 12 f 0 with the suppression of 40 - 50 dB (f 0 is the center frequency). The proposed technique could be very useful to design a bandpass filter with a wide and high-suppression stopband efficiently.

Compact left-handed dual-band filters based on shundted stub resonators

In this paper, super-compact microstrip dual-band resonator is presented, designed using the superposition of two simple left-handed (LH) resonators with single shunt stub. The proposed resonator exhibits spurious response in wide frequency range and therefore allows construction of dual-band filters using the superposition principle. The equivalent circuit model of the proposed resonator is crated and the influence of different geometrical parameters to the performances of the resonator are analyzed in details. As an examples, two dual-band filters that operate simultaneously at the WiMAX frequency bands are designed.

A Novel Wide, Dual-and Triple-Band Frequency Reconfigurable Butler Matrix Based on Transmission Line Resonators

In this paper, a novel reconfigurable Butler matrix based on transmission line resonators is presented and implemented. This matrix is built from embedding a reconfigurable multilayer directional coupler with an open stub resonator and p-i-n diodes to operate over three different states, such as dual band, triple band, and wideband. The coupler reconfigurability allows creating bandstop filters in the UWB band by controlling the p-i-n diode states in the quarter wave ( $\lambda $ /4) of the open stub resonator length. To demonstrate the design approach, two prototypes of coupler and Butler matrix are fabricated and tested. Good agreement between the measured and simulated results is obtained. The proposed designs show good results in terms of compactness, low insertion loss, and high isolation with a minimal number of RF p-i-n diodes used for all states.