High Impedance Microstrip Line Research Articles

Method to Improve the Roll-Off and Stopband Response in Low Pass Filter Using Patch Resonators for Modern Wireless Communication

In this paper, several types of patch resonators design procedure are proposed and analysed to improve the roll-off and stopband response in low pass filter. The proposed patch resonators consist of T-shaped patch resonator (TS-PR) that provides instant sharp roll-off and also dual folded T-shaped resonator (DFTS-PR) that improves the roll-off of the previous TS-PR. The transmission zeros of the resonators can be adjusted by varying length and width of high and low impedance microstrip lines. It has been shown that the final design of the patch resonators provides sharp roll-off and acceptable stopband bandwidth by adopting both TS-PR and DFTS-PR. The proposed low pass filter with 3-dB cut-off frequency (fc ) of 5.26 GHz exhibits excellent roll-off rate of 82.2 dB/GHz from 5.5 GHz to 11.7 GHz. Moreover, the transition of the proposed filter is 0.45 GHz which contributes to a sharper transition band from passband to stopband.

Ultra-wide stopband HTS LPF with closed-loop cross-coupled microstrip structure

A compact high-temperature superconducting (HTS) low-pass filter (LPF) with an ultra-wide stopband and a sharp transition band is designed by integrating the fifth-order low-pass filter branch and closed loop cross-coupled (CLCC) microstrip structure. The fifth-order low-pass filter consists of two radial-stubs (RSs), one butterfly-shaped stub (BSs), and two T-shaped stubs (TSs), which can introduce five transmission zeros (TZs) with independently controllable frequency and position, so as to obtain good sideband suppression or upper stopband characteristics. The CCLC microstrip circuit is composed of cascaded high and low impedance microstrip lines, which can widen the width of the upper stopband and realize the ultra-wide stopband characteristic. The operating mechanism of the fifth-order LPF resonator and the CLCC microstrip structure are analyzed by theLCequivalent circuit models. The implemented LPF on a 0.5-mm thick MgO wafer with double-sided YBCO films demonstrates 1-dB cut-off frequency (fc) at 2 GHz and 0.12 GHz narrow transition bandwidth from −1dB to −40 dB. The measured results show a 30-dB harmonic suppression from 1.08fc to 11.7fc i.e., above 23 GHz, a steep roll-off rate of 326 dB/GHz, an in-band insertion loss (IL) <0.10 dB, and a miniaturized size of 0.24λgc × 0.08λgc (λgc is the guided wavelength at the cut-off frequency).

Rectifier Circuit using High-Impedance Feedback Line for Microwave Wireless Power Transfer Systems

Research on wireless power transmission technology is being actively conducted, and studies on spatial transmission methods such as SSPS are currently underway for applications such as power transfer to the upper part of steel towers and power transfer to flying objects such as drones. To enable such applications, it is necessary to examine the configuration of the power-transfer and power-receiving antennas and to improve the RF-DC conversion efficiency (hereinafter referred to as conversion efficiency) of the rectifier circuit on the power-receiving antenna. To improve the conversion efficiency, various methods that utilize full-wave rectification rather than half-wave rectification have been proposed. However, these come with problems such as a complicated circuit structure, the need for additional capacitors, the selection of components at high frequencies, and a reduction in mounting yield. In this paper, we propose a method to improve the conversion efficiency by loading a high-impedance microstrip line as a feedback line in part of the rectifier circuit. We analyzed a class-F rectifier circuit using circuit analysis software and found that the conversion efficiency of the conventional configuration was 54.2%, but the proposed configuration was 69.3%. We also analyzed a measuring circuit made with a discrete configuration in the 5.8-GHz band and found that the conversion efficiency was 74.7% at 24dBm input.

Coding DGS resonator sensor for ultra-high Q-factor dielectric thickness detection

In this paper, a high Q-factor-based defective ground structure (DGS) etched microwave resonator is demonstrated to identify the unknown thickness of non-destructive monolayer dielectric material. The proposed structure consists of coupled sharp-edged split-square resonator (CS-SSR), a high-impedance microstrip line, and symmetrically coded DGS optimized by adaptive genetic algorithm (AGA), which is evaluated through simulation and experiment assessment. AGA is applied to obtain ultra-high quality factor (Q-factor) using a robust calculation model with rapid convergence speed. The high Q-factor leads to high sensitivity, better accuracy, and enhanced resolution of the microwave sensor. Furthermore, the comparison of the results between the codeless, asymmetrical, and symmetrical DGS resonator illustrates that the symmetrical coding DGS resonator with higher sensitivity and better performance for dielectric material thickness detection sensors.

Микрополосковые фильтры с широкими полосами пропускания

New microstrip designs of bandpass filters based on a low-pass filter was developed. Several or all the sections of high-impedance microstrip lines of the designed filters were connected to the ground by stubs. The filters have high frequency-selective properties, and their fractional bandwidths are in the range of 30 % –150 %. An experimental sample of a filter with a 2 GHz central frequency of the passband and 70% fractional bandwidth was made on an alumina substrate 1 mm thick. The filter has a substrate area of 46 × 21 mm2. Good agreement of the measured frequency response of the filter with the characteristics calculated by the numerical electrodynamic analysis of its 3D model was shown.

A quintuple mode resonator based bandpass filter for ultra-wideband applications

This paper presents a new configuration of quintuple mode resonator for designing a bandpass filter for ultra-wideband applications. The multiple-mode resonator is constituted by two capacitive ended rectangular stubs and connected with a high impedance microstrip line. Inter-digital coupled feed lines are designed to excite the resonator. Standard analytical approach based on odd-/even-mode analysis is applied to examine the resonant characteristics of the multi-mode resonator. The proposed filter has the characteristics of low insertion loss, wide stopband along with compact size. The bandwidth (|S11| ≤ − 10 dB) of the proposed filter has been observed to vary from 3.11 to 10.63 GHz with low insertion loss value uniform around − 0.8 dB. A wide stopband with attenuation of more than 15 dB (11.27–20 GHz) is observed for the proposed design. The filter occupies a compact area equal to 23.4 mm × 10 mm (about 0.43λg × 0.09λg, where λg is the guided wavelength at 6.85 GHz). The simulated results agree well with the measured results validating the effectiveness of the work.

A Compact and Sharp Rejection Ultra-Wideband Bandpass Filter Based on Short and Open Stub-Loaded Multiple Mode Resonators

A compact and high-rejection ultra-wideband (UWB) microstrip band-pass filter is proposed by using the multi-mode resonator (MMR) technique. The proposed MMR structure is realized by three open stubs-loaded and two short stubs-loaded and a high impedance microstrip line. Five modes, including two odd modes and three even modes could be designed within the UWB band. By resizing the dimensions of the stubs, the resonant modes of the MMR structure are arranged wider bandpass which the passband selectivity with this configuration significantly improved. By this configuration, the even modes can be flexibly controlled, while the odd modes remain the same. The proposed filter has a passband covers 4.1–10.6 GHz and its measured 3 dB fractional bandwidth is about 89%. In order to validate the performance of the proposed technique, the designed UWB band-pass filter is fabricated and the experimental verification is provided. A good agreement has been found between simulation and measurement’s results. To our knowledge, the size of the proposed UWB filter is small in comparison with known similar filters.

Super-Wide Impedance Bandwidth Planar Antenna for Microwave and Millimeter-Wave Applications.

A feasibility study of a novel configuration for a super-wide impedance planar antenna is presented based on a 2 × 2 microstrip patch antenna (MPA) using CST Microwave Studio. The antenna comprises a symmetrical arrangement of four-square patches that are interconnected to each other with cross-shaped high impedance microstrip lines. The antenna array is excited through a single feedline connected to one of the patches. The proposed antenna array configuration overcomes the main drawback of conventional MPA with a narrow bandwidth that is typically <5%. The antenna exhibits a super-wide frequency bandwidth from 20 GHz to 120 GHz for S11 < −15 dB, which corresponds to a fractional bandwidth of 142.85%. The antenna’s performance of bandwidth, impedance match, and radiation gain were enhanced by etching slots on the patches. With the inclusion of the slot, the maximum radiation gain and efficiency of the MPA increased to 15.11 dBi and 85.79% at 80 GHz, which showed an improvement of 2.58 dBi and 12.54%, respectively. The dimension of each patch antenna was 4.3 × 5.3 mm2. The results showed that the proposed MPA is useful for various existing and emerging communication systems such as ultra-wideband (UWB) communications, RFID systems, massive multiple-output multiple-input (MIMO) for 5G, and radar systems.

Bandwidth Improvement of Center-Fed Series Antenna Array Targeting for Base Stations in Offshore 5G Communications

A $1\times 12$ center-fed series antenna array, with a novel probe feeding structure to broaden the bandwidth, is designed for 5G base stations deployed in the land for offshore maritime communications. The improvement of the bandwidth is achieved through a combination of folding and replacing the center feed line to a lower layer away from patch radiators. By moving the center feed line to the lower layer beneath radiators, serious mutual-coupling and corresponding parasitic effect between the feed and radiators are reduced, facilitating better transmission and also resulting in better matching to the 50- $\Omega $ coaxial probe. Moreover, a vertically folded-U structure is proposed to be inserted in part of the feed line, to provide a section of a high impedance microstrip line and further broaden the impedance bandwidth. A simulation study is performed on the geometry of the center feed line to investigate how the antenna performance can be controlled. The antenna array design procedure is outlined and a prototype with over 20% bandwidth, which can fully cover the 4.8–4.99 GHz 5G spectrum band, is fabricated and measured for impedance matching, radiation pattern, and broadside gain. For both S-parameter and far-field results, good correspondence is achieved between simulation and measurement. The proposed series-fed antenna array with coaxial feed is very suitable to be deployed in base stations with 1-D beam steering capability.

Improved Methanol Detection Using Carbon Nanotube-Coated Carbon Fibers Integrated with a Split-Ring Resonator-Based Microwave Sensor

A novel microwave sensor based on the electrically small split ring resonator (SRR) integrated with the hierarchal carbon nanotube coated carbon fiber (CNTCF) for gas-sensing applications is proposed. The CNTCF is synthesized via catalytic chemical vapor deposition process and investigated by scanning electron microscopy and transmission electron microscopy for their structural information. The CNTCF integrated SRR is excited by the electromagnetic field through high impedance microstrip line. The use of highly conductive CNTCF as sensing material facilitated extremely large surface area causing a substantial change in the inherent resonant frequency as a sensor response at room temperature (25 °C) for methanol, nitrogen dioxide (NO2), ethanol, and chloroform gases. This change in resonant frequency facilitates the detection and sensing of the analyte gases under controlled environment and constant relative humidity of 32%. The CNTCF-SRR sensor exhibited high selectivity and sensitivity toward the methano...

High-sensitive nitrogen dioxide and ethanol gas sensor using a reduced graphene oxide-loaded double split ring resonator

A reduced graphene oxide (rGO) incorporated double split ring resonator (DSRR) portable microwave gas sensor is proposed in this work. The sensor is fabricated using two major steps: the DSRR is fabricated on the FR-4 substrate, which is excited by a high impedance microstrip line. The rGO is synthesized via a chemical route and coated inside the smaller ring of the DSRR. The SEM micrographs reveal crumpled sheets of rGO that provide a large surface area, and the XRD patterns of the as-synthesized rGO reveal the two-dimensional structure of the rGO nanosheets. The sensor performance is measured at room temperature using 100–400 ppm of ethanol and NO2 target gases. At 400 ppm, the sensor reveals a shift of 420 and 390 MHz in the S21 frequency for NO2 and ethanol gases, respectively. The frequency shifts of 130 and 120 MHz in the S21 resonance frequency are obtained for NO2 and ethanol gases, respectively, at a very low concentration of 100 ppm. The high sensitivity of the proposed rGO gas sensor is achieved due to the combined effect of the large surface area of the rGO responsible for accommodating more gas molecules, and its increased conductivity due to the transfer of the electron from the rGO. Moreover, an exceedingly short response time is observed for NO2 in comparison to ethanol, which allows the proposed sensor to be used for the selective detection of NO2 in a harsh environment. The overall approach used in this study is quite simple, and has great potential to enhance the gas detection behaviour of rGO.

Compact semi‐lumped dual‐ and tri‐wideband bandpass filters

This study presents a novel design approach of semi-lumped dual-wideband bandpass filters (DWB-BPF) and tri-wideband-BPF (TWB-BPF). One or two pairs of λ/4 uniform-impedance open stubs first generate the desired transmission zeros (TZs) to divide the lowpass frequency response based on radial stub loaded high-impedance microstrip line (RSHIML) into a dual- or tri-band lowpass-bandpass frequency response. Then, a pair of lumped-element capacitors are series to the input and output ports to suppress the direct current signal, so as to transform the lowpass passband to the bandpass passband. Moreover, the other RSHIML is also introduced not only to produce a TZ located at the lower transition band of the first passband to improve its passband selectivity, but also to enhance the passband flatness. As examples, a semi-lumped DWB-BPF and a semi-lumped TWB-BPF are designed and fabricated, which exhibit the merits of wide passbands, low insertion loss and compact size.

Biosensing using an asymmetric split-ring resonator at microwave frequency

ABSTRACTIn this paper, an asymmetric split-ring resonator (aSRR) is proposed and experimentally demonstrated for a biosensing device at microwave. Compared with the transitional sensor, the proposed biosensor has a single aSRR-assisted transducer and is excited by a time varying magnetic field component of a high-impedance microstrip line to realize strong and localized field enhancement in the sensing region and achieve high quality factor (Q-factor). The measured and simulated results show that the aSRR structure is a compact configuration, and can achieve narrow resonance with a higher Q-factor than the symmetric one. Moreover, the resulting biosensor device exhibits that the frequency shifting is observed when the sensor is loaded with different glucose concentrations, i.e., 0.25%, 1.25%, and 5%, and the corresponding shifting are 170MHz, 280MHz, and 340MHz, respectively. Therefore, the proposed biosensor offers advantages of label-free detection, a simple and direct scheme, and cost-efficient fabrication.

Compact continuous tunable low-pass filter with high selectivity and wide stopband

This letter presented a novel compact continuously tunable low-pass filter (LPF) using varactor-loaded coupled rhombic stubs. The proposed LPF demonstrated excellent roll-off selectivity, wide stopband range as well as good cut-off frequency tunability. This LPF consisted of three varactor-tuned coupled rhombic stubs loaded on a section of high-impedance microstrip line symmetrically and two coupled line LPFs which could further improve the stopband performance. A detailed explanation of the tuning mechanism was illustrated by adopting lumped-element equivalent circuit model. The measured results showed not only a wide cut-off frequency tuning range of 56% from 350 to 800 MHz, but also an excellent steepness factor of less than 1.14. Additionally, a rejection level of greater than 20 dB up to 8 GHz (>10 fc) was observed in the stopband. The proposed ideas were verified by the measured results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1641–1644, 2016

Design of Phased Arrays of Series-Fed Patch Antennas With Reduced Number of the Controllers for 28-GHz mm-Wave Applications

New modified 2 × 2 and 3 × 3 series-fed patch antenna arrays with beam-steering capability are designed and fabricated for 28-GHz millimeter-wave applications. In the designs, the patches are connected to each other continuously and in symmetric 2-D format using the high-impedance microstrip lines. In the first design, 3-D beam-scanning range of ± 25° and good radiation and impedance characteristics were attained by using only one phase shifter. In the second one, a new mechanism is introduced to reduce the number of the feed ports and the related phase shifters (from default number 2 N to the reduced number N + 1 in the serial feed (here N = 3) and then the cost, complexity, and size of the design. Here, good scanning performance of a range of ± 20°, acceptable sidelobe level, and gain of 15.6 dB are obtained. These features allow to use additional integrated circuits to improve the gain and performance. A comparison to the conventional array without modification is done. The measured and simulated results and discussions are presented.

Common‐mode suppression for balanced bandpass filters in multilayer liquid crystal polymer technology

A new multilayer differential transmission line for common-mode suppression fabricated using an organic liquid crystal polymer multilayer substrate is proposed and analysed. The structure consists of a pair of parallel strip lines printed on the top layer of the substrate that are capacitively coupled to conductor patches periodically etched in an intermediate interface. These patches are symmetrically connected to a solid ground plane by means of short-circuited high-impedance microstrip line sections and metalised via holes. The differential signal supported by the coupled strips is not significantly affected by the presence of the middle layer layout, whereas the common-mode signal propagation is strongly suppressed within a certain frequency band. When this structure is cascaded with a simple differential bandpass filter exhibiting poor common mode rejection, a good common mode response is achieved within the unperturbed differential passband. The measurements confirm a significant enhancement of common-mode rejection thanks to the use of the proposed differential lines.

Compact microstrip tri‐band lowpass‐bandpass filter

A compact microstrip tri-band lowpass-bandpass filter is described. Two different sets of λ/4 uniform-impedance open stubs generate the desired transmission zeros (TZs) to divide a lowpass frequency response based on a radial stub loaded high-impedance microstrip line into a tri-band lowpass-bandpass frequency response. A lowpass passband with a 3 dB cutoff frequency of 0.66 GHz, and two bandpass passbands centred at 1.57 and 2.45 GHz for global positioning system and wireless local area network applications are obtained in this design. The fabricated tri-band lowpass-bandpass filter occupies a compact circuit area of 0.065 λgc × 0.085 λgc. Seven TZs around the three passbands result in high band-to-band isolation, good passband selectivity and a wide upper stopband.

Millimeter wave broadband high sensitivity detectors with zero-bias Schottky diodes

Two broadband detectors at W-band and D-band are analyzed and designed with low barrier Schottky diodes. The input circuit of the detectors is realized by low and high impedance microstrip lines, and their output circuit is composed of a radio frequency (RF) bandstop filter and a tuning line for optimum reflection phase of the RF signal. S-parameters of the complete circuit are exported to a circuit simulator for voltage sensitivity analysis. For the W band detectors, the highest measured voltage sensitivity is 11800 mV/mW at 100 GHz, and the sensitivity is higher than 2000 mV/mW in 80–104 GHz. Measured tangential sensitivity (TSS) is higher than —38 dBm, and its linearity is superior than 0.99992 at 95 GHz. For the D band detector, the highest measured voltage sensitivity is 1600 mV/mW, and the typical sensitivity is 600 mV/mW in 110–170 GHz. TSS is higher than −29 dBm, and its linearity is superior than 0.99961 at 150 GHz.

Compact wideband microstrip bandpass filter with wide upper stopband based on coupled-stub loaded resonator

A novel wideband microstrip bandpass filter BPF based on a coupled-stub loaded resonator CSLR is presented in this article. The CSLR is constructed by attaching one short-circuited parallel coupled microstrip line PCML in shunt to a high impedance microstrip line. The filter bandwidth can be conveniently controlled via reasonable adjusting of the impedance of PCML. Moreover, new defected microstrip structures DMSs introduced in the PCML functions as a means of adjusting the positions of transmission zeros, created by the PCML. The resonant mode and transmission zero chart are given, indicating that the higher modes could be suppressed by the transmission zeros. Finally, to validate the proposed method, two wideband BPF filters with and without DMSs centered at 3 GHz with 3 dB fractional bandwidth of 87% are designed and fabricated. The measured results show that both the return losses are better than 15.8 dB, while the BPF with DMSs has a -19.4 dB isolation wideband from 1.57 f0 to 4.23 f0. The measured results are in excellent agreement with full-wave electromagnetic simulation results. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:122-128, 2015.

Design of Miniaturized Microstrip LPF and Wideband BPF With Ultra-Wide Stopband

This letter presents a novel lowpass filter (LPF) structure which consists of a section of high-impedance microstrip line (HIML) with a pair of radial stubs (RSs) loaded at its center and a pair of stepped-impedance open stubs (SIOSs) loaded on both ends of HIML. The RSs loaded HIML exhibits a lowpass property and has a wide stopband. The loaded SIOSs not only can improve the roll-off rate of LPF significantly but also is able to extend the stopband. Based on such a LPF structure, a pair of highpass shorted HIMLs are paralleled on both sides of LPF to construct a wideband bandpass filter (BPF) with wide stopband. To validate the proposed method, two filters, i.e., a LPF with cutoff frequency fc at 1.07 GHz and a BPF centered at f0 = 0.89 GHz with -3 dB fractional bandwidth of 87%, are designed and fabricated. The measured results show the fabricated LPF has a -20 dB isolation bandwidth from 1.27 fc to 13.7fc while the fabricated BPF has a -20 dB isolation bandwidth from 1.56 f0 to 15 f0. Moreover, the fabricated LPF and BPF also have the compact size of 0.107 λgc ×0.083 λgc and 0.123 λg0 ×0.073 λg0, respectively. Good agreement can be observed between the simulation and measurement.