Meander Slot Research Articles

Symmetrical In‐Band Full‐Duplex Antenna With Broad Bandwidth Using Stacked Patch Array

ABSTRACTThis article proposes a novel symmetrical design for a Broadband Bidirectional In‐band Full‐duplex (IBFD) co‐radiator antenna with high isolation. The distinctive double differential feed network, constructed using orthogonally arranged meander slot baluns, is connected to a pair of co‐radiating patches with the metallic visa, resulting in structural symmetry and offering bidirectional radiation patterns. The null‐coupling features of the balun, that is, the differential potentials and differential filtering, generate good isolation in the antenna with a narrow bandwidth. The limitation of narrow bandwidth has been overcome by employing a stacked patch array above the radiating patch. The installed stacked patch array generates additional resonating modes due to the induced surface waves and enhances the operational bandwidth of the antenna. The multiple techniques of polarization diversity, double differential feed, and stacked patch array in the antenna offer a minimum isolation of 62 dB over a wide operational band of (1.8–2.9) GHz. It offers bidirectional broadside radiation having a lower cross‐polar of dB. Moreover, the structural symmetry of the antenna produces identical S‐parameters, gain, and radiation patterns for both antenna ports. The fabricated prototype of the proposed antenna with overall dimensions of ( is the free space wavelength referring to the lowest operational frequency) shows a good correlation between the simulated and measured results.

A dual-band microwave sensor for liquid permittivity characterization based on multiple complementary split-ring resonators

Abstract This article presents a dual-band planar microwave sensor to characterize the permittivity of liquid samples. The sensor utilizes a splitter–combiner microstrip segment loaded with two pairs of triangular-shaped complementary split-ring resonators (CSRRs). By integrating a meander slot into the CSRRs and incorporating inter-resonator coupling between the CSRRs, the proposed sensor achieves enhanced frequency shifts, resulting in improved sensitivity. An adulteration detection experiment is conducted to validate the sensor’s performance by mixing mineral oil into castor oil with a polydimethylsiloxane container placed on the sensing area. The variations in resonant frequency and peak attenuation are employed to extract the permittivity of the loaded liquid sample. The peak sensitivities in determining the real permittivity are measured to be 6.34% and 5.7% for the first and second frequency bands, respectively. The measured errors for extracting the real and imaginary parts of the complex permittivity are approximately 3.95% and 7.47% for the first frequency band and 3.67% and 6.28% for the second frequency band, respectively. The proposed dual-band microwave sensor, with its high sensitivity, compact size, small sample volume, and low cost, demonstrates great potential for applications in the quality monitoring of agricultural and industrial products.

An in‐band full‐duplex antenna for 2.4 GHz WLAN using differential‐feed based neutral coupling for isolation enhancement

AbstractThis article introduces a unique design approach for a compact in‐band full‐duplex (IBFD) antenna with good isolation in a wider bandwidth at the 2.4 GHz WLAN. The meander slot baluns are innovatively constructed in the feeding network, one balun on the top substrate layer and the other on the bottom substrate layer of the ground, to realize double differential feeding and polarization diversity. The metallic vias that connect one of the baluns in the feeding network with the co‐radiating patch further reduce the antenna's overall size. The balun's neutral coupling characteristics of differential potentials, which reduce the leakage currents by creating null potential, and differential filtering, which suppresses the leakage currents by non‐coupling fields, generate high isolation in the antenna. The designed balun offers a stable differential feed with a trivial magnitude and phase imbalances of (0.04–0.06) dB and , respectively. The antenna offers a minimum isolation of 78 dB with a wider bandwidth of 130 MHz. The far‐field measurement shows broadside radiation with low cross‐polar levels of less than −32 dB. A prototype is fabricated on FR‐4 substrate layers with an overall size of (0.8 × 0.8 × 0.012) ( is the free space wavelength of the frequency GHz) to validate the proposed design performance. The measured results of the prototype properly correlate with the simulated results.

Wideband meander-line-antipodal-vivaldi slot-antenna for millimeter-wave applications

An antipodal Vivaldi monopole radiator is employed in an innovative wideband planar slotted meander antenna. A quarter-wave microstrip feed is coupled to the antenna for a ground reflector plane over a meander line with five right and left antipodal Vivaldi (RLAV) slots on either side and a series of Z, inverted U and inverted Z-shaped turns. The FR4 substrate with a relative permittivity of 4.4 and modest dimensions of 50 × 20 × 1.6 mm3 is used to implement the proposed antenna. A 17.39% fractional bandwidth of -29.10dB (S11 <-10dB), an average radiation efficiency of 73%, and a gain of 6.7dBi at the central frequency of 28GHz. The outcomes of using RLAV arms at the centre of the meander structure enhance the antenna’s performance validated using the high-frequency structural software Ansys 2022R1, which is a finite element method (FEM) tool. The measured results indicate that the bandwidth enhancement has been fine-tuned for use in the 5G millimetre wave band in the Frequency Range 2 (FR2) n261 frequencies, the 3rd generation partnership project (3GPP) band n257, and the Federal Communications Commission’s (5G) high-band spectrum (25-30GHz).

Miniaturization of a Fully Metallic Bandpass Frequency Selective Surface for Millimeter-Wave Band Applications

This article presents a miniaturized all-metallic bandpass frequency selective surface (FSS) for millimeter-wave (mmWave) applications. The designed FSS is realized as a slot-type element that can be easily incorporated into all-metallic device architectures. The miniaturization is achieved by a convoluted or meander slot structure, i.e., a miniaturization technique borrowed from conventional substrate-based FSS design. It is demonstrated that the proposed FSS element provides a stable and wide bandpass performance from 24.9 to 31.4 GHz for both the transverse electric (TE) and the transverse magnetic (TM) polarizations at the broadside direction ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta = 0^{\circ }$</tex-math></inline-formula> ). Adequate performance is maintained at oblique incidence angles up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta = \pm \,45^{\circ }$</tex-math></inline-formula> . A 25 × 25-elements FSS array prototype has been manufactured using the cost-effective chemical etching technique and experimentally characterized utilizing a free-space measurement setup. The results demonstrate a remarkably good correlation between simulations and measurements. Hence, the proposed miniaturized FSS represents an excellent potential to realize an all-metallic FSS with low insertion loss, low profile, and wideband performance at low fabrication costs for mmWave applications.

Design of compact dual‐band shared‐aperture antenna system based on frequency selective surface

AbstractA miniaturized dual‐band dual‐polarization base station antenna array operating at 2.4–2.8 and 4.6–5.0 GHz is proposed in this paper. The upper‐band unit is embedded in the lower‐band unit to miniature the array size. The size of the proposed shared‐aperture antenna element is 0.28 × 0.28 . To ensure the normal radiation of dual‐band under the small frequency ratio, a meander slot frequency selective surface structure is introduced, which is electromagnetically transparent to the lower‐band unit and function as metal ground for the upper‐band unit to ensure the normal radiation of the upper and lower‐band units, respectively. Simulation and measured results show that the antenna array meets the following design specifications: dual‐band operating (voltage standing wave ratio [VSWR] &lt; 2), mutual coupling less than −20 dB basically, satisfactory gain and radiation characteristics.

전후방비 개선 설계 기법을 이용한 ISM 대역 방향 탐지 안테나

In this study, a direction-finding array antenna with an improved front-to-back ratio was developed by inserting meander slots into the ground plane of an electrically small antenna. The proposed ground slot structure improves direction-finding capabilities while maintaining the electrically compact structure of the antenna. The overall size of the antenna is 58 mm×58 mm×40 mm, with each array element measuring 40 mm×22 mm×1.6 mm. The antenna consists of eight elements attached to a vertical column, forming an octagonal structure that affords omnidirectional detection. The measured S11 bandwidth (≤−10 dB) is between 2.37 and 2.48 GHz. At 2.44 GHz, the maximum gain is −2.71 dBi, the 3-dB beamwidth occurs at an elevation angle of 74.2° and azimuth angle of 84.4°, and the front-to-back ratio is 8.89 dB.

A dual-mode microstrip sensor for simultaneously extracting complex permittivity and permeability of magnetodielectric samples

This paper proposes a dual-mode microstrip sensor for simultaneously retrieving the electromagnetic parameters of magnetodielectric (MD) materials. The microwave microstrip sensor consists of a 50Ω standard microstrip line and a modified magnetic-LC resonator. In the MLC structure, the center arm is replaced with a meander slot to improve the electric filed confinement, with interdigital capacitor structures inserted into the opening of the split ring to enhance magnetic field density. The complex permittivity ( ε r ) and permeability ( μ r ) of the MD samples are simultaneously retrieved by measuring S-parameters of odd- and even-modes. The frequency compensation and artificial neural network are employed to improve the retrieval accuracy. The proposed sensor is fabricated and tested, and the sensitivities for retrieving permeability and permittivity reach 10.78% and 4.71%, respectively. • A dual-mode microstrip sensor is proposed to fully characterize magneto-dielectric materials, with the measurement steps reduced to be one step in comparison with previously proposed sensors. • The meander slot and interdigital capacitors are adopted to improve field confinement, and the frequency compensation and artificial neural network model are introduced to improve the retrieval accuracy. • The even-mode and odd-mode are employed to retrieve complex permeability and permittivity, respectively, and the proposed sensor exhibits enhanced capability than previous designs.

A Low-Profile Dual-Polarized Magneto-Electric Dipole Antenna for 5G Applications

A low-profile dual-polarized magneto-electric dipole (MED) is presented in this communication. The low profile was achieved using meander slots on the vertical magneto dipole, reducing the antenna height to 0.15λ0, where λ0 is the wavelength of the center frequency. Relatively, the proposed MED structure is easier to process and more stable than the traditional low-profile MED structure. The broadband performance for 5G Applications was realized based on MED structure, and the dual-polarization structure has wider coverage area and lower multipath transmission losses. Moreover, the orthogonal feeding structure provides a satisfying isolation between two ports. To verify the simulation results, a prototype of the proposed antenna was fabricated and measured. The results show that the overlapped operating frequency bandwidth with |S11| ≤ −10 dB, |S12| ≤ −20 dB was 36.8% from 3.1 GHz to 4.5 GHz, the peak gain reached 10.2 dBi, and the average gain exceeded 8.5 dBi. The measured 3 dB beamwidth with more than 44 degrees beamwidth was realized in both E-plane and H-plane. In addition, cross-polarization levels below −22 dB that covered the above frequency band were achieved. Compared with other MED antennas, in addition to broadband and high gain, the proposed antenna has the advantages of a low profile, easy processing, and low cost, which make it a competitive candidate for 5G applications.

A Dielectric Sensor Based on Differential Microstrip Lines Coupled With Multiple Magnetic-LC Resonators

A differential microstrip lines-based microwave microstrip sensor loaded with multiple magnetic-LC (MLC) resonators is proposed in this manuscript. The proposed microstrip sensor is evolved from a traditional microstrip sensor, which has a single resonator unit excited by a single microstrip line. Based on the traditional one, the differential microstrip lines are added, which can improve the level of common-mode (CM) suppression. In the MLC resonator structure, a meander slot is embedded into the resonator to enhance the electrical field intensity. Three MLC resonators are etched on the bottom layer of the substrate, which can produce three transmission zeros (TZs) of differential mode (DM) due to the mutual coupling between these resonators and their own RLC equivalent circuit models. The three TZs can be regarded as three modes, the TZ in low-frequency band is the first odd-mode, the middle frequency TZ is even-mode, and the high-frequency TZ is the second odd-mode. As the resonance strength of the second odd-mode is relatively low; thus, it is ignored and the first odd-mode and even-mode are considered. Odd- and even-modes can be utilized to retrieve the permittivity of material under test (MUT). In the measurement, the error removal model is established to guarantee the experimental accuracy of MUT. The proposed microstrip sensor has average sensitivities of about 5.53% and 4.55% for odd- and even-modes, respectively. The proposed sensor has some superiorities to previous designs in terms of design structure, CM suppression, and multimode detection.

Dual composite right/left‐handed unit with improved spurious performance and its application in wide‐stopband bandpass filter

AbstractA compact dual composite right/left‐handed (D‐CRLH) unit with improved spurious performance is presented in this study. The proposed D‐CRLH unit consists of an interdigital capacitance (IDC) and a microstrip section inductor (MSI). Compared with the traditional IDC, the proposed IDC is improved by connecting the ends of the alternate fingers through the metallic paths on the back of the substrate. Thus, the spurious resonance at low frequency is eliminated and the usable bandwidth of the IDC is extended. The meander slots are also exploited in each finger of the IDC to increase the series capacitance, which contributes to reducing the circuit size. Furthermore, the proposed D‐CRLH unit is applied in the wide stopband bandpass filter (BPF) design to demonstrate its practicability. The BPF is fabricated and measured for demonstration. The measured results are in good agreement with the simulated results.

Design of Broadband Aperture-Coupled Stacked Microstrip Antennas Using Second-Order Filter Theory

In this article, the authors propose a lumped circuit methodology for the design of broadband stacked microstrip patch antennas fed through an aperture. First, an equivalent circuit (EC) is introduced for the antenna. The EC consists of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LC$ </tex-math></inline-formula> series resonator modeling the feed plus two capacitively coupled <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LC$ </tex-math></inline-formula> parallel resonators accounting for the radiating patches. Then, a deembedding procedure based on total least squares method is introduced to determine all the parameters of the antenna EC. Second, the circuit stage modeling the patches is designed as a second-order Chebyshev filter based on coupled resonators. Since the standard Chebyshev approach leads to circuit parameters that cannot be physically obtained in practice, a modified second-order quasi-Chebyshev design is presented, which can be physically implemented by stacking one conventional rectangular patch above one rectangular patch with both inner and meandering slots. The proposed methodology is used to design an antenna with over 30% bandwidth at a center frequency of 5.57 GHz. A prototype has been fabricated and measured, and good agreement has been found between simulations and experiments.

Equal/unequal half mode substrate integrated waveguide filtering power dividers using an ultra-compact metamaterial unit-cell

Abstract In this paper, a novel ultra-compact metamaterial unit-cell is introduced. The proposed unit-cell consists of one modified rings which has been designed based on the fractal technique and meander technique. These techniques are used to reduce the physical size of the conventional complementary split ring resonators (CSRRs). In the proposed metamaterial unit-cell which is called the fractal/meander CSRR (FMCSRR), the slot lines in the conventional CSRRs are replaced by the fractal and meander slots, simultaneously. The FMCSRR unit-cell is a planar metamaterial element which exhibits negative permittivity and is considered as electric dipole when excited by an axial electric field. Thus, the FMCSRR unit-cell is modeled as a shunt resonator tank. Therefore, by using the proposed FMCSRR configuration, all of the interior space of the ring has been used and the slot lines have been increased. Consequently, the higher inductance has been achieved and the resonance frequency of the proposed FMCSRR unit-cell becomes lower compared with the conventional CSRR. That’s mean the electrical size of the introduced unit-cell FMCSRR unit-cell is smaller than the conventional CSRR with the same physical sizes. A microstrip notch band filter, a microstrip band-pass filter, a half mode substrate integrated waveguide (HMSIW) band-pass filter and three HMSIW filtering power dividers (FPDs) with different power division ratios of 1:1, 1:4, and 1:8 have been designed to illustrate the ability of the proposed FMCSRR unit-cell in the size reduction. All of the designed devices operated at 2.4 GHz which are suitable for WLAN applications. For verification the performance of the utilized techniques in miniaturization of the dimension, the designed equal/unequal HMSIW FPDs have been fabricated and tested. A reasonable agreement between simulated and measured results has been achieved. The results confirmation that a miniaturization about 79% has been obtained. The total size of the proposed HMSIW FPDs are about 0.09λ g × 0.09λ g. The proposed HMSIW FPDs have many advantages in terms of compact size, low insertion loss, high selectivity, easy integration with the other planar circuits, and controllable bandwidth.

Compact reconfigurable antenna system for spectrum interweaved cognitive radio

This article discusses the design of a compact antenna system for spectrum interweaved cognitive radio (CR). The system consists of a sensing filtenna and three communicating antennas. The sensing ultra-wideband (UWB) antenna is a coplanar-waveguide (CPW)-fed monopole (2.2–11 GHz). The narrowband communicating patch antennas are reconfigurable through a switching mechanism, operating in six different frequency bands (5.54, 6.12, 7.60, 8.25, 9.64, and 10.29 GHz). To block the Wi-MAX and WLAN bands, the proposed design uses a meandering slot and a stepped U-slot in the monopole. Analysis of communicating antennas using the theory of characteristic mode analysis indicates good radiation in the desired frequencies. Isolation among these antennas is better than −18 dB. A constant group delay and linear phase response indicate a good time-domain performance of the proposed UWB antenna. Simulated results match closely with those from measurements on the prototype. The proposed antenna system can find applications in various sectors adopting CR like internet of things.

Design of a novel ultra‐wideband dual‐polarized printed planar antenna

A novel antenna, which has a simple one-layer printed planar structure with dual-polarization and ultra-wideband (UWB) properties, is proposed in this article. The proposed antenna consists of a pair of crossed dipoles, two stacked square loops, four meander slots, and a hornlike reflecting cavity. The stacked loops positioned around the crossed dipoles are utilized to introduce a new resonant mode in the lower frequency band, which essentially widens the impedance bandwidth and realizes the miniaturization design. To further enhance the impedance bandwidth, the four meander slots are cut from the crossed dipoles to generate a new resonant mode in the higher frequency band. Therefore, the impedance bandwidth is greatly expanded. A hornlike reflecting cavity is used to enhance the unidirectional radiation pattern over the operating frequency band. A prototype is designed, fabricated, and measured. Measured results show that the proposed antenna achieves a voltage standing wave ratio (VSWR) < 2, impedance bandwidth up to 92% (from 1.05 to 2.85 GHz). The isolation between two linear orthogonal polarizations >25 dB, and stable unidirectional radiation patterns over the entire working frequency band with gain >8 dBi. Furthermore, the proposed antenna has a compact planar size of 0.25 λ L × 0.25 λ L ( λ L is the longest operating wavelength).

Asymmetric microstrip fed meander line slot antenna for 5.6 GHz applications

This paper presents the design of a meander line slot antenna. The designed antenna operates at the frequency range of 5.45 GHz to 5.7 GHz covering wireless local area network applications. The proposed antenna comprises a circular patch design with a meander slot embedded within the patch. Besides to meander line slot structure, asymmetric microstrip feed is provided to the antenna. To achieve better antenna performance, parametric studies are carried out. The antenna's total size is 15 × 14 × 1.57 mm3. For the designed antenna, the −10 dB impedance bandwidth is 4.48 %, the gain is 1.3 dBi with a radiation efficiency of 84.43 %. The current distribution and radiation pattern of the proposed meander slot antenna have been observed and simulated.

Dual-Band On-Body Near Field Antenna for Measuring Deep Core Temperature With a Microwave Radiometer

Deep core temperature is the most basic and important information about health conditions. The non-contact infrared thermometer is widely used to measure the temperature of the human body. However, the infrared thermometer cannot measure the deep core temperature. To overcome this limitation, measuring deep core temperature with a microwave radiometer is gaining attention. In this study, we propose a dual-band on-body near-field antenna for measuring deep core temperature with a microwave radiometer application. The proposed antenna has a compact size of 20 mm &#x00D7; 30 mm &#x00D7; 1.52 mm. The negative (-) radiator is located at the top of the substrate and the positive (+) radiator is located at the bottom of the substrate. The dual-band is proposed for high temperature resolution and is achieved by a meander slot on the radiator. The antenna is fabricated on a high dielectric substrate and the stubs are proposed to reduce the size of the proposed antenna so that it can be used on various human body parts.

A Temperature-Compensated Differential Microstrip Sensor for Microfluidic Applications

The paper proposes a temperature-compensated sensor for microfluidic application. The sensor consists of a splitter/combiner section with two symmetrical complementary split-ring resonators (CSRR). A polydimethylsiloxane substrate is attached with the microfluidic channel aligned to the meander slot of the CSRR. A split-ring resonator (SRR) with peripheral circuit is added to detect environmental temperature. The water-methanol mixtures with various water fractions are measured at temperature ranging from 20°C to 50°C. The environmental temperature is firstly measured by the resonant frequency shift produced by SRR. Then, the variations in the resonant frequency and quality factor of the differential splitter/combiner section, as well as the temperature, are used as the input data for training the neural network. In comparison with previous designs, the proposed sensor is capable of not only suppressing the influences of environmental factors, but also retrieving the permittivity and loss tangent of liquid sample at specific temperature, thereby identifying the liquid accurately.

BOX: an efficient benchmark facility for the study and mitigation of interface-induced training in accelerator type high-field superconducting magnets

For 30 years, training and unpredictable degradation in accelerator type high-field Nb3Sn magnets have seriously hampered Nb3Sn application. Training and deterioration have to be solved or at least better controlled. The global picture shows that most of the R&D and short model magnets start to train at some 40%–70% of the critical current and then creep up to almost the critical current within some 10–50 training steps. A typical class of failures leading to quenches is largely characterized by cracking and debonding at the interfaces between cable and glass-resin insulation, as well as between insulation and coil former. The study of training by means of testing demonstrator coils is rather expensive and time consuming. However, advances in magnet design and fabrication can also be assessed and benchmarked using BOX, the bonding experiment presented here, that produces maximum uniaxial Lorentz forces at some 7.5 T in a controlled experiment performed in 11 T solenoid facility at the University of Twente. BOX samples use only one meter of Nb3Sn cable inserted in a three-wave meandering slot in a flat metallic sample holder, reproducing magnet-relevant interactions between cable, insulation, impregnated materials and coil former. The meander shape exposes seven straight cable sections to a transverse magnetic field, thereby generating a representative level of shear stress at the interfaces. In this way, characteristic training curves of magnets can be mimicked and solutions studied. We aim to demonstrate with various samples failure mechanisms of high-field Nb3Sn magnets without the need to manufacture complete magnets. BOX may thus be expected to allow for quick and affordable testing of novel insulations, impregnation materials, coatings and interfaces for Nb3Sn magnets achieved by investigating various resins, fillers and more.

Ultrahigh-Sensitivity Microwave Microfluidic Sensors Based on Modified Complementary Electric-LC and Split-Ring Resonator Structures

The paper proposes an ultrahigh sensitivity microwave sensor for retrieving the complex permittivity of the liquid sample. The proposed sensor originally evolves from the complementary split-ring resonator-based sensor, which confines the electric field in the slot of the resonator. A complementary electric-LC resonator structure is applied to substitute the CSRR due to its excellent ability of concentrating the electric field. To further improve the field confinement, a meander slot is embedded in the central arm of the resonator. Then, two etched complementary split-ring resonators are added on both sides of the central meander arm of the modified complementary electric-LC resonator. A polydimethylsiloxane microfluidic channel substrate is placed on the meander arm, and a mixture of water-ethanol is injected. The variations in the resonant frequency and peak attenuation are used to retrieve the complex permittivity of the injected liquid sample. The developed sensors are fabricated and tested, and a good agreement is observed between measured data and reference values. The peak sensitivities in retrieving the relative permittivity achieve 2.5% and 2.71% with the proposed sensors, which are much higher than previously reported designs.