T-shaped Resonator Research Articles

Compact microstrip lowpass filter with very sharp roll-off using meandered line resonators

In this paper, a new compact size microstrip lowpass filter (LPF) with a very sharp roll-off is presented to apply in the modern wireless networks. The proposed LPF is designed using the series main resonators with meandered lines based on inductor-capacitor (LC) equivalent circuit analysis. The main goal is to achieve maximum-sharp roll-off by maintaining a wide stopband bandwidth and high return loss (RL). The main resonator of the proposed filter is consisted of two meandered line hairpin resonators (MLHR), and a meandered line T-shaped resonator (MLTR). The designed suppressor is composed of two coupled radial stubs to create a wide stopband. Low return loss in the passband, which has been created by the main resonator, is resolved by the suppressor structure with high return loss. The measured results show a − 3 dB cut-off frequency of 1.93 GHz. The very sharp transition band starts at 1.93 to 1.97 GHz (from − 3 to − 20 dB). The stopband is from 1.97 to 19.9 GHz (with the suppression level of − 20 dB). Also, the total size of the proposed LPF is only 13.3 × 10.1 mm2.

A Design of a Dual-Band Bandpass Filter Based on Modal Analysis for Modern Communication Systems

A dual-band bandpass filter (BPF) composed of a coupling structure and a bent T-shaped resonator loaded by small L-shaped stubs is presented in this paper. The first band of the proposed BPF covers 4.6 to 10.6 GHz, showing 78.9% fractional bandwidth (FBW) at 7.6 GHz, and the second passband is cantered at 11.5 GHz with a FBW of 2.34%. The bent T-shaped resonator generates two transmission zeros (TZs) near the wide passband edges, which are used to tune the bandwidth of the first band, and the L-shaped stubs are used to create and control the narrow passband. The selectivity performance of the BPF is analyzed using the transfer function extracted from the lumped circuit model verified by a detailed even/odd mode analysis. The BPF presents a flat group delay (GD) of 0.45 ns and an insertion loss (IL) less than 0.6 dB in the wide passband and a 0.92 IL in the narrow passband. A prototype of the proposed BPF is fabricated and tested, showing very good agreement between the numerically predicted and measured results.

Design of wideband bandpass filter with high and wide stopband rejection using asymmetrical‐loaded stepped ‐impedance resonator

This study presents a wideband bandpass filter (WBBPF) with wide and high stopband suppression by loading a stepped-impedance resonator (SIR). The prototype of WBBPF is composed of an inverted π-shaped resonator with T-shaped resonator and open stub loaded, centrally. Odd-/even-mode analysis technique is employed to characterize the resonant properties of this prototype. Then, a SIR is loaded to this filter, asymmetrically, to improve the out-of-band performance. For experimental validation, a WBBPF is designed, fabricated, and tested. The measurement results show that the center frequency of WBBPF is located at 5.095 GHz, and the 3-dB fraction bandwidth is about 71%. Plus, the out-of-band suppression with 30-dB rejection level can be extended to 18.17 GHz.

Measurement of water content in heavy oil with cavity resonator

The study of optical microcavity sensors in current micro optical electromechanical systems (MOEMS) devices is an important research direction in this field. In this study, a surface plasmon optical waveguide structure with MIM (Metal Insulator Metal), semi-circular resonator, and T-shaped resonator was examined. The effects of the coupling distance, the geometrical size of the T-shaped cavity and its asymmetry, and the radius of the semi-circular cavity on the Fano resonance spectrum were analyzed numerically. The sensitivity of the refractive index sensor was up to1066.67nm/RIU. The detection of the water content of the heavy oil found that the Fano resonance line shifted to the short-wave direction as the volume percentage of the contained water increased. The volume percentage resolution of the sensor's heavy oil water content could be as low as2.05×10-9. The proposed structure can overcome the shortcomings of common refractive index sensors and therefore has great application prospects in chemical and biological sensing.

Synthesis Design of Chebyshev Wideband Band-Pass Filters With Independently Reconfigurable Lower Passband Edge

In this brief, a new and planar topology is presented for the synthesis design of Chebyshev wideband bandpass filters (WB BPFs) with independently reconfigurable lower passband edge. The proposed design is based on a new T-shaped resonator, whose topology and parameters can be directly derived from a 5th-order Chebyshev LC circuit. Then, a varactor is employed as the tuning element. By controlling the supplied voltage on the varactor, the lower passband edge of the proposed filter can be independently tunable in continue manners, while the upper one is maintained fixed. For verification, a reconfigurable prototype is designed and measured. As the measured and simulated results agree well with each other, a simple and high-efficiency design of reconfigurable-bandwidth WB BPFs is verified.

Compact wide stopband microstrip lowpass filter using polygon patches and meandered lines

In this paper, a low pass filter based on T-Shaped resonator is presented. The T-Shaped resonator consists of meandered lines and rectangular patches. Also, the LC model and transfer function of the proposed resonator is presented. For suppression of spurious harmonics, a bandstop structure consists of hexangular patches and open stubs has been utilized. Finally, the wide stopband microstrip lowpass filter with cutoff frequency 2.72 GHz has been simulated, fabricated and measured. The LPF has good characteristics such as wide stopband and insertion loss lower than 0.18 dB in the passband region. The rejection level is less than -20 dB from 2.98 up to 21.3 GHz. The filter size is 10.5 mm×12.7 mm, or 0.131 λ<sub>g</sub>× 0.158 λ<sub>g</sub>, where λ<sub>g</sub> is the guided wavelength. The measured and simulated results of the filter is in good agreement with each other, which show the merits of low insertion loss and wide stopband.

Synthesis Design of Equal-Ripple and Quasi-Elliptic Wideband BPFs With Independently Reconfigurable Lower Passband Edge

This paper presents a new synthesis design of equal-ripple and quasi-elliptic wideband band-pass filters (WB BPFs) with independently reconfigurable lower passband edge. The synthesis design starts from a 5th-order LC circuit. By using optimum multipole concept, a T-shaped resonator for the design of Chebyshev BPF without redundant elements can be directly derived, which is formed by a pair of parallel-coupled lines and short-ended stub. To sharpen the selectivity and maintain equal-ripple response, a pair of transmission zeros are introduced through replacing the short-ended stub by its multi-section counterparts. Thus, two prototypes, whose equivalent LC circuits can be directly derived, are presented for the synthesis of equal-ripple and quasi-elliptic BPFs. To realize the desired reconfigurable response, a capacitor is used. By controlling the capacitance value, the lower passband edge can be independently tunable in continue manners while the upper one is fixed. For validation, two prototypes with fixed and reconfigurable band-width are fabricated and measured. As the measured and simulated results agree well with each other, a high-efficiency design of reconfigurable-bandwidth WB BPFs is validated.

A neuro‐based approach to designing a Wilkinson power divider

In this paper, a new neuro-based approach using a feed-forward neural network is presented to design a Wilkinson power divider. The proposed power divider is composed of symmetrical modified T-shaped resonators, which are a replacement for quarter-wave transmission lines in the conventional structure. The proposed technique reduces the size of the power divider by 45% and suppresses unwanted bands up to the fifth harmonics. To verify the concept, a prototype of the power divider has been fabricated and tested, exhibiting good agreement between the predicted and measured results. The results show that the insertion loss and the isolation at the center frequency are about 3.3 ± 0.1 dB and 23 dB, respectively.

Terahertz Selective Emission Enhancement from a Metasurface-Coupled Photoconductive Emitter in Quasi-Near-Field Zone

We present a THz emission enhancement of 41 times at 0.92 THz from a metasurface made of T-shaped resonators excited in a quasi-near-field zone. Such a metasurface has an intrinsic transmission minimum with Q factor of 4 at 1.25 THz under far-field excitation. When this metasurface is coupled onto the backside of a 625-μm-thick photoconductive emitter, the metasurface is below the Fraunhofer distance to the excitation source. As such, one broad enhancement around 0.47 THz and another extremely narrow enhancement at 0.92 THz in the emission spectrum are observed owing to a quasi-near-field excitation. Theoretically, the Q factor of the latter is up to 307, which is limited by the spectral resolution in experiment. The numerical simulations indicate that the T-shaped resonators serve as an array of plasmonic antennas resulting in the aforementioned emission enhancement of THz radiation.

Broadband and wide-angle reflective linear polarization converter for terahertz waves

Polarization control of electromagnetic waves has wide applications in the field of communications, imaging, and remote sensing. Recent designs of periodic two-dimensional devices or metasurfaces employed for polarization control are limited in efficiency, bandwidth, and allowable incidence angle. This is attributed to high dissipation in the dielectric material used and to less-optimal device configuration. We propose and experimentally validate a reflective linear polarization converter metasurface with high efficiency, wide bandwidth, and wide acceptance angle in the terahertz regime. Our device is composed of three layers: an array of oriented metallic T-shaped resonators, cyclic olefin copolymer (COC) as a low loss dielectric layer, and a ground plane. For the normal and 45° incidence angles, a fabricated sample shows a bandwidth of 95% and 100%, with the average polarization conversion ratio above 80%, covering a frequency range of 0.38–1.07 and 0.36–1.08 THz, respectively. The wide-angle stability is attributed to a phase difference between a single resonance along the T-shaped resonator and a smooth phase response in the low-loss COC dielectric layer. For broad bandwidth performance, a resonator arm extending to adjacent unit cells introduces the fundamental resonance at a lower frequency, while the packed unit cell size shifts the grating lobe onset to a higher frequency. These design aspects can significantly improve the performance of other metasurfaces operating in any frequency range.

Dual Band Reconfigurable Compact Circular Slot Antenna for WiMAX and X-Band Applications

A circular slotted reconfigurable antenna for WIMAX and X-band wireless communication applications is presented. The aim of this article is to design an antenna, which can operate at dual band with high gain. The designed antenna is compact in size with dimensions 32–24 mm.CPWfeeding is used in the design of frequency reconfigurable antenna, and BAR-64-20V PIN diodes are installed for frequency tuning operation. By employing a T-shaped resonator inside the circular slot and a parallel resonator in transmission line, the dual band operation is realized. The antenna covers WiMAX (3.1–4.5 GHz) and X-band (10.3–11.7 GHz) for such applications as space research and mobile radio astronomy. Frequency switching is attained by the proper positioning of PIN diodes at the circular slot. The proposed compact antenna shows good radiation characteristics and good impedance bandwidth.

Design of compact microstrip low pass filter using triangular and rectangular shaped resonator with ultra-wide stopband and sharp roll-off

In this paper a new microstrip lowpass filter (LPF) is designed and fabricated with sharp roll-off and ultra-wide stop-band. To obtain these features, triangular and T-shaped resonators are utilized. The main resonator is created by two triangular and rectangular shaped structures. LC equivalent circuit and transfer function of the main resonator is extracted to compute transmission zeros of the main resonator. The proposed LPF has a 3 dB cut-off frequency of 1.663 GHz. The occupied size of the designed filter is 209.33 mm2 (17.3 mm × 12.1 mm). The ultra-wide stopband is achieved from 1.81 to 29.4 GHz with better than 20 dB attenuation. The achieved figure-of-merit of the proposed LPF is 33,813, which shows good specifications of the filter.

A compact Gysel power divider design using U-shaped and T-shaped resonators with harmonics suppression

ABSTRACTIn this paper, design process of a new compact microstrip Gysel power divider (GPD) with harmonics elimination is proposed. In the designed GPD structure, two types of resonators are applied to make transmission zeros (TZs). T-shaped resonator makes one TZ at lower frequency and U-shaped resonator makes two TZs at higher frequencies. These three created transmission zeroes by applied resonators result in the good harmonics suppressing in the Gysel divider. The LC-equivalent circuit (LCEC) of the resonators is extracted and the locations of these three transmission zeroes are calculated analytically. The proposed GPD creates three transmission zeros at near 3 GHz, 4.9 GHz, and 9.1 GHz. The proposed Gysel power divider (GPD) with applied resonators reduces the circuit size more than 66% (occupied 34% size) compared with the conventional GPD with λ/4 transmission lines. Moreover, the fractional bandwidth of the proposed divider is 50% and also suppresses up to seventh harmonic.

T-Shaped Compact Dielectric Resonator Antenna for UWB Application

In this article, a novel T-shaped compact dielectric resonator antenna for ultra-wideband (UWB) application is presented and studied. The proposed DRA structure consists of T-shaped dielectric resonator fed by stepped microstrip monopole printed antenna, partial ground plane and an inverted L-shaped stub. The inverted L-shaped stub and parasitic strip are utilized to improve impedance bandwidth. A comprehensive parametric study is carried out using HFSS software to achieve the optimum antenna performance and optimize the bandwidth of the proposed antenna. From the simulation results, it is found that the proposed antenna structure operates over a frequency range of 3.45 to more than 28 GHz with a fractional bandwidth over 156.12%, which covers UWB application, and having better gain and radiation characteristics.

Center Frequency and Bandwidth Reconfigurable Spoof Surface Plasmonic Metamaterial Band-Pass Filter

In this study, we report a design concept to obtain center frequency and bandwidth reconfigurable spoof surface plasmon polaritons (SSPP) band-pass filter using T-shaped spoof SPP resonator. The design, analysis, and implementation of the proposed filter have been given with detailed mathematical analysis. Tuning has been performed using varactor diode which is introduced at different positons in the T-shaped resonator. Since spoof SPP has high field confinement and enhancement, hence it offers low crosstalk and mutual coupling as compared with conventional microstrip which is desirable to make low-loss system. The filter has been fabricated using a 1.52-mm-thick microwave laminate and characterization has been done using Keysight Field-Fox analyzer N9918A. The fabricated filter has a reconfigurable center frequency from 4.2 to 4.4GHz with insertion loss ~4.2 dB and bandwidth reconfigurable from 4.12 to 4.52GHz with ~3.8 dB insertion loss in the tuning range. The proposed reconfigurable band-pass filter will pave an important role in the designing and developing of the flexible plasmonic circuits and systems.

Microstrip Lowpass Filter with Ultra-Wide Stopband Using Folded Structures

Abstract In this article, a new microstrip lowpass filter with ultra-wide stopband using T-shaped resonators and folded structures is described. The structure of this filter is very simple, so that only a T-shaped resonator is used as main resonator without any particular changes in these resonators. The designed T-shaped main resonator has a −3 dB cut-off frequency of 1.4 GHz. On the other hand, T-shaped resonators with low base length are utilized as suppressing cells. To provide an ultra-wide stopband, two pair of T-shaped resonator and two high frequency suppressing cells are employed. The structure of this filter is folded to have compact size. The measured results shows −3 dB cut-off frequency of 1.4 GHz. The transition band is equal to 0.25 GHz from 1.4 to 1.65 GHz, with corresponding attenuation levels of −3 to −20 dB. The ultra-wide stopband with −22 dB suppression level is from 1.68 to 40 GHz. Also, the total size of the proposed lowpass filter is 16.8×11.3 mm2.

Spoof Surface Plasmon Polaritons Based Reconfigurable Band-Pass Filter

This letter reports the design and analysis of the bandwidth (BW) reconfigurable band-pass filter using spoof surface plasmon polaritons at THz/microwave frequency. The designed filter consists of a spoof SPP T-shape resonator in which tuning has been introduced using variable capacitor device (having a cutoff frequency in THz regimes). Even and odd mode analysis has been carried out for a better understanding of the phenomenon. The proposed concept of variable bandwidth at a THz frequency in the SSPP structure has been demonstrated through Co-EM simulation. For the experimental validation of the proposed approach, the filter has been designed at microwave frequency, developed on a 60 mil (1.52 mm) thick microwave laminate, and characterized using a Keysight Field-Fox analyzer N9918A . In THz and microwave frequency regime, the designed filter has 3-dB BW reconfigurability of 20 GHz (0.41–0.43 THz) and 300 MHz (100–400 MHz) with the insertion loss of ~3 dB and ~1.7 dB–3.2 dB, respectively. The proposed reconfigurable bandpass filter will have an important role in the design and development of plasmonic circuits and systems.

Lowpass Filter with Wide Stopband Based on T-Shaped Resonator Loaded Step-Impedance Hairpin Resonator

A lowpass filter with wide stopband based on stepped impedance hairpin resonator is proposed. Multiple transmission zeros are created in the stopband region by different size T-shaped resonator to achieve wide stopband. A lowpass filter with 3dB cutoff frequency (fc) at 3.2GHz is designed, simulated and fabricated. Experimental results indicate that stopband can be extended to more than 7fc with a rejection level of 20dB after loading T-shaped resonator. The insertion loss is lower than 0.4dB and return loss is better than 16dB in the passband. Excluding the feed lines, the size of the filter is less than 0.26λg X 0.06λg. The modified filter is of good value in engineering application for its small size, sharp cutoff frequency response and wide stopband.

Compact Microstrip NWB/DWB BPFs With Controllable Isolation Bandwidth for Interference Rejection

In this paper, a novel and planar topology, which can be used to design notched-/dual-wideband bandpass filters (NWB/DWB BPFs) with controllable isolation bandwidth, is presented for interference rejection. Here, the isolation band is referred to notch band for NWB BPFs, while stopband between two passbands for DWB BPFs. The proposed topology is started from a novel T-shaped resonator with two poles and three zeros. Then, a pair of parallel-coupled lines and two open-ended stubs is added. With the help of the added parts, the extra four poles are introduced, and another two zeros are suppressed or excited according to whether it is required to realize a notched- or dual-band response. Due to the existence of multiple transmission poles and zeros, the excellent filtering responses, i.e., high isolation level, sharp selectivity, and good passband flatness, can be achieved. Besides, it is found that the isolation bandwidth of BPFs based on the proposed topology can be continuously varied from a narrow notch band to a wide stopband while the outer two passband edges are maintained unchanged by using suitable para-meters. To validate this, two prototypes are designed and measured, including a six-mode NWB BPF with 3-dB passband fractional bandwidth (FBW) of 94.1% and 20-dB notch FBW of 2.39%, and a three-mode DWB BPF with 3-dB passband FBWs of 36.2% and 22.6% and 20-dB stopband FBW of 14.5%.

Microwave Sensor for Detection of Solid Material Permittivity in Single/Multilayer Samples With High Quality Factor

In this paper, a planar microstrip sensor based on a band-stop filter for determining relative permittivity of solid materials is presented. The proposed sensor has been composed of the structure of meandered microstrip line with a T-shaped resonator and an interdigital structure that is connected ground by via. Interaction between the T-shaped resonator and the interdigital structure is caused to increase electric field intensity and the high field increase the sensor sensitivity and resolution. The microwave sensor by using single layer technology is fabricated on the substrate RO4003. The samples of FR4 and RO4350 in single and double layer forms as multilayer are placed on the sensor, and the sensor is demonstrating different resonance frequencies. The relationship between changing the resonance frequency and variation of the relative permittivity is linear, and it determines unknown materials’ dielectric characterizations. The permittivity of samples changes from 3 to 11; therefore, the resonance frequency varies from 3.7 to 5.65 GHz linearly. The proposed sensor shows improvement relative to other similar works in the fields of sensitivity and quality factor.