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Summary: This article presents a novel wearable frequency selective surface (FSS) for shielding the communication link of implantable devices with the external environment. The proposed shield blocks a dual‐band frequency operating at 404 MHz and 2.45 GHz in the medical implant communication service (MICS) and industrial, scientific, and medical (ISM) bands. The two distinct stop bands provide a high‐frequency band ratio of 6.02 in an ultra‐miniaturized physical form factor of 0.024λo × 0.024λo, with at least 76.96% miniaturization when compared to the existing art. Each of the unit cells is imprinted on a conformal 50 μm polyester substrate in a symmetrical configuration. The polyester adheres with jean to realize its compatibility with wearable applications. The designed shield system offers a low profile of only 0.00146λo. By suppressing the grating lobe, the proposed shield achieves a high angular stability of 80° and polarization insensitivity of 90° in both transverse electric (TE) and transverse magnetic (TM) modes. The FSS is fabricated and measured results validate its performance. To evaluate the physical insight, an equivalent circuit model (ECM) analysis is done. To ensure durability, the proposed shield system is tested with Amitech SDR04. [ABSTRACT FROM AUTHOR]

Summary: A novel single‐layer ultra‐miniaturized multi‐band Frequency Selective Surface (FSS) with a circular vent is designed for shielding LTE and ISM bands. The top layer of the proposed FSS unit cell incorporates a circular patch along with convoluted arms. The designed FSS unit cell exhibits band‐rejection characteristics with a resonance of 800 MHz, 2.45 GHz, and 5 GHz and bandwidths of 523 MHz, 687 MHz, and 725 MHz, respectively. The periodicity of an ultra‐miniaturized FSS unit cell is 0.024λօ x 0.024λօ, encompassing a spatial vent hole of 0.01λօ, where λօ corresponds to the lowest operating frequency. Moreover, the proposed FSS unit cell remains unaltered angular stability up to 75° with less than 1% frequency deviation in TE and TM modes. Good polarization insensitivity for the designed four‐fold symmetrical FSS unit cell is achieved. Further, an Equivalent Circuit Model (ECM) analysis is developed to infer the physical insight of the proposed FSS unit cell. The FSS prototype is measured for the assertion, and the good agreement between the findings from simulation and measurement is validated. For real‐time assertion, the FSS prototype is verified using the Amitech SDR04. Thus, FSS is a promising candidate with good ventilation for shielding the LTE, Bluetooth, and Wi‐Fi application bands. [ABSTRACT FROM AUTHOR]

This paper presents a novel ultraminiaturized frequency selective surface (FSS) for L-band electromagnetic shielding applications. A basic square loop incorporated with folded arms in the top layer constructs the single-layer FSS design. Band-stop characteristics for the entire L-band operating frequency ranging from 1 GHz to 2 GHz are offered by the proposed design. An ultraminiaturized profile of 0.028λο × 0.028λο is achieved by the designed FSS, where λο corresponds to the lowest operating frequency, achieving at least 32.1% miniaturization when compared to the state-of-the-art FSS designs in the literature. Polarization insensitivity with a peak shielding effectiveness of 45.4 dB is manifested by the rotational symmetry of the proposed design. The proposed FSS exhibits excellent angular stability performance up to 80° with a frequency deviation of less than 1%. The equivalent circuit model helps to understand the working principle of the proposed FSS. The experimental results of the designed FSS prototype agree well with the simulation results. Hence, the proposed spatial filter is a suitable candidate for enhancing security in wireless communication at the carrier frequencies of GPS systems. [ABSTRACT FROM AUTHOR]

Purpose: The design, fabrication and experimental validation of defected microstrip structure (DMS) are proposed to address the problem of near-end crosstalk (NEXT) and far-end crosstalk (FEXT) between the microstrip transmission lines in a printed circuit board. Design/methodology/approach: The proposed DMS evolved with the combination of spur line (L-shaped DMS) and U-shaped DMS topologies. This technique reduces the strength of electromagnetic coupling and suppresses crosstalk by optimizing the capacitive and inductive coupling ratio between the linked microstrip lines. The practical inductance value is much more significant in DMS than in defected ground structures (DGS), but the capacitance value remains the same. Findings: A DMS unit is etched on the aggressor microstrip line instead of the DGS circuit. Because there is no leakage via the ground plane and the circuit size is far smaller than with DGS, the enclosure issue is disregarded. DMS structures have a larger effective inductance and are resistant to electromagnetic interference. A tightly coupled transmission line structure with minimal separation between the coupled microstrip line is designed using DMS. Further research must be conducted to improve the NEXT, FEXT and spacing between the transmission lines. Originality/value: Simulation and actual measurement results show that the proposed DMS structure can effectively suppress crosstalk by analysing the S-parameters, namely, S_12, S_13 and S_14, with measured values of 1.48 dB, 20.65 dB and 21.099 dB, respectively. The data rate is measured to be 1.34 Gbps as per the eye diagram characterization. The results show that the NEXT and FEXT are reduced by approximately 20 dB in the frequency range of 1–11 GHz for mixed signals. The substantial measured results in the vector network analyser coincide with the computer simulation technology microwave studio suite simulation results. [ABSTRACT FROM AUTHOR]

The demand for vehicular antennas increases in tandem with the need for multiple features in automobiles. The development of optically transparent antenna (OTA) has made it possible to deploy antennas on delicate surfaces such as glass. Earlier studies on OTA demonstrated its viability using materials such as transparent conducting oxides (TCO) and conductive polymers. A tri-band OTA is proposed in this paper for vehicular applications. The antenna operates at 1.8 GHz, 2.4 GHz and 3.39–12 GHz bands, covering automotive/wireless applications such as GSM, Bluetooth, Wi-Fi, vehicular communication and electronic toll collection. The proposed OTA is developed on soda lime glass, and the material TCO is used for the radiator and the ground plane. The antenna prototype is tested on windshield and in an anechoic chamber, the gain and efficiency are found to be greater than 1 dBi and 80%, respectively. Furthermore, a machine learning technique for vehicle classification is proposed, which could help in electronic toll collection, automatic vehicle identifier, and parking management applications. The presented algorithm achieves 80% classification accuracy with a minimum window size. [ABSTRACT FROM AUTHOR]

Currently, the inspection and verification of vehicle-related information are done by police inspectors using camera-based systems or manually. Though integrating video technology is more advantageous than manual operation, they do not perform accurately due to bad weather or driving styles. This paper presents the design of a compact, durable, battery-free, UHF RFID tag with enough memory to carry necessary information for automatic identification of traffic law enforcement applications. The vehicle owner can also be alerted when the tag is detected due to the visual indication facility. This tag’s novel feature includes adapting a modified T-match structure to match the highly capacitive impedance of the chosen RFID sensor chip, i.e., Farsens Rocky100. In contrast to existing designs, the proposed tag contains no extra lumped components that necessitate an external impedance matching circuit. Instead, the input impedance was matched using an advanced T-match topology and by optimizing the antenna’s geometrical features. Simulations were done in Ansys HFSS (High-Frequency Structure Simulator) whereas the dimensions of all the printed elements were fine-tuned using parametric optimization. The tag was fabricated on a low-cost FR4 substrate and measured. The tag with an overall size of 110 × 25 × 2.4 mm³ can be detected by a conventional UHF RFID reader within a range of about 0.2 m–1 m. Due to the loop configuration, the tag exhibits a confined detection range while operating well within short ranges. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to design a suitable guard trace to reduce the electromagentic interference between two closely spaced high frequency transmission lines. A novel cross-shaped resonator combined via fence is passed down to alleviate far-end and near-end crosstalk (NEXT) in tightly coupled high-speed transmission lines. The distance between the adjacent transmission lines is increased stepwise as a function of trace width. Design/methodology/approach: A rectangular-shaped resonator via fence is connected by a guard trace has been proposed to overcome the coupling between the traces that is separated by 2 W. Similarly, by creating a cross-shaped resonator via fence connected by guard trace that reduces the spacing further by 1.5 W. Findings: A tightly coupled transmission line structure that needs separation by a designed unit cell structure. Further research needs to be conducted to improve the NEXT, far-end crosstalk (FEXT) and spacing between the transmission lines. Originality/value: This study portrays a novel method that combines the resonators via fence with a minimum spacing between the tightly coupled transmission lines which reduce the NEXT and FEXT; thereby reducing the size of the routing area. The resultant test structures are characterized at high frequencies using time domain and frequency domain analysis. The following scattering parameters such as insertion loss, NEXT and FEXT of the proposed method are measured as 1.504 dB, >30 dB and >20 dB, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a quad-port multiple-input multiple-output (MIMO) semitransparent antenna is designed for automotive applications. The transparent soda lime glass substrate is used in the prototype antenna for windshield applications, and the radiator is nontransparent copper metal. The unit cell radiator of the MIMO antenna is similar to the "NISSAN automobile-like" logo. The proposed MIMO antenna has a −10 dB impedance bandwidth of 3.4 to 11 GHz. The edge-to-edge distance between the elements in the MIMO configuration is 6 mm. The antenna elements are perpendicularly oriented to offer dual (horizontal and vertical) polarization, which aids in providing better isolation and good signal reception in all directions. The isolation between the resonating elements is greater than 15 dB without the use of any decoupling structure. The diversity metrics are examined in order to gain a better understanding of the MIMO antenna performance. The envelope correlation coefficient (ECC) is less than 0.01, diversity gain (DG) is greater than 9.98 dB, and the total active reflection coefficient (TARC) and channel capacity loss (CCL) are less than −10 dB and 0.07 bits/s/Hz, respectively. The quad-port MIMO antenna offers transparency of 52.26% over the entire area. The proposed antenna could be suitable for automotive applications such as intelligent transportation systems (ITS), vehicular communications, and the automatic vehicle identifier (AVI). [ABSTRACT FROM AUTHOR]

In this paper, a quad-port multiple-input multiple-output (MIMO) semitransparent antenna is designed for automotive applications. The transparent soda lime glass substrate is used in the prototype antenna for windshield applications, and the radiator is nontransparent copper metal. The unit cell radiator of the MIMO antenna is similar to the "NISSAN automobile-like" logo. The proposed MIMO antenna has a −10 dB impedance bandwidth of 3.4 to 11 GHz. The edge-to-edge distance between the elements in the MIMO configuration is 6 mm. The antenna elements are perpendicularly oriented to offer dual (horizontal and vertical) polarization, which aids in providing better isolation and good signal reception in all directions. The isolation between the resonating elements is greater than 15 dB without the use of any decoupling structure. The diversity metrics are examined in order to gain a better understanding of the MIMO antenna performance. The envelope correlation coefficient (ECC) is less than 0.01, diversity gain (DG) is greater than 9.98 dB, and the total active reflection coefficient (TARC) and channel capacity loss (CCL) are less than −10 dB and 0.07 bits/s/Hz, respectively. The quad-port MIMO antenna offers transparency of 52.26% over the entire area. The proposed antenna could be suitable for automotive applications such as intelligent transportation systems (ITS), vehicular communications, and the automatic vehicle identifier (AVI). [ABSTRACT FROM AUTHOR]

A low-profile multi-polarized MIMO ultra-wideband antenna suitable for body-centric communications is reported. MIMO configuration is achieved using the symmetric heptagonal monopole (SHM) antenna, a mirrored SHM antenna, an asymmetric ruby-shaped monopole (ARSM) antenna, and a mirrored ARSM antenna placed over the modified C-shaped ground plane (MCGP). The proposed antenna elements are designed to achieve resonance for the entire ultra-wideband frequency range. The SHM antenna is coupled with a co-planar waveguide to produce linear polarization. An ARSM antenna generates circular polarization utilizing an asymmetric geometry both in the radiator and a truncated ground plane. Both the SHM antenna and an ARSM antenna are aligned face-to-face over an MCGP plane and good isolation >15 dB is realized between the antenna elements. The gain and total efficiency for linear polarized and the circularly polarized antennas are 3.05–4.8 dBi/48–66% and from 2.8 to 5 dBic/52 to 70.5%, respectively. The specific absorption rate values are evaluated to understand their suitability for WBAN communications. [ABSTRACT FROM AUTHOR]

There is a strong demand for compact and multiband antennas as wireless technologies become more integrated into automobiles. These antennas must be able to serve multiple services without compromising the size and installation space. In addition, the antenna incorporated should not affect the aesthetic appearance of the vehicle. This paper presents a compact multiple-input-multiple-output (MIMO) antenna working at 2.45 GHz (Wi-Fi/Bluetooth/RFID) and ultra-wideband (UWB) frequencies. A basic rectangular monopole with a self-complementary structure is used to design the antenna element. The size of the antenna element is 20 × 22 mm2. The proposed MIMO cube is developed with four antenna elements in cubical orientation to achieve compactness and better isolation. The overall dimension of the MIMO antenna is 35 × 22 mm2. The diversity antenna shows impedance bandwidth of 2.4–11.5 GHz and isolation of more than 20 dB. The envelope correlation coefficient (ECC) of the MIMO antenna is less than 0.2, diversity gain (DG) is greater than 9 dB, and total active reflection coefficient (TARC) and channel capacity loss (CCL) are less than −10 dB and 0.4 bits/s/Hz, respectively. The gain and efficiency are found to be greater than 1 dBi and 72%, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a pattern diversity UWB antenna for Wireless Body Area Network (WBAN) communications. Pattern diversity antenna comprises two antenna elements with directional and omnidirectional patterns suitable for off-body and on-body communications respectively. Several broad-banding techniques such as Co-Planar waveguide, parasitic patches, and cavity resonant techniques are incorporated in microstrip antenna to achieve an ultra-wideband of 7.5 GHz (3.1 to 10.6 GHz) with a directional pattern. Monopole radiator topology is utilized to achieve a UWB frequency range of 2.6–10.6 GHz with an omnidirectional pattern. Pattern diversity is achieved using an orthogonal arrangement of the antenna elements in a compact size of 40 mm × 34 mm, maintaining the isolation >20 dB between the antennas. Gain varies from 2.2 to 4.6 dBi and 2.5 to 7.5 dBi for omnidirectional and directional antenna respectively. The simulated radiation efficiency for the directional antenna and the omnidirectional antenna are 74–86% and 52–66.5% respectively. The proposed design provides a good diversity performance in the entire UWB bandwidth with ECC<0.1 and a diversity gain of approximately 10 dB. SAR impact evaluated under various conditions is found to be <1.6 W/Kg for 1 gram of tissue. [ABSTRACT FROM AUTHOR]

The demand for vehicular antennas increases in tandem with the need for multiple features in automobiles. The development of optically transparent antenna (OTA) has made it possible to deploy antennas on delicate surfaces such as glass. Earlier studies on OTA demonstrated its viability using materials such as transparent conducting oxides (TCO) and conductive polymers. A tri-band OTA is proposed in this paper for vehicular applications. The antenna operates at 1.8 GHz, 2.4 GHz and 3.39–12 GHz bands, covering automotive/wireless applications such as GSM, Bluetooth, Wi-Fi, vehicular communication and electronic toll collection. The proposed OTA is developed on soda lime glass, and the material TCO is used for the radiator and the ground plane. The antenna prototype is tested on windshield and in an anechoic chamber, the gain and efficiency are found to be greater than 1 dBi and 80%, respectively. Furthermore, a machine learning technique for vehicle classification is proposed, which could help in electronic toll collection, automatic vehicle identifier, and parking management applications. The presented algorithm achieves 80% classification accuracy with a minimum window size. [ABSTRACT FROM AUTHOR]

This paper presents the design and development of a semitransparent antenna that can be used in automotive applications to support multiple wireless services. The proposed quad-port multiple input multiple output (MIMO) antenna is comprised of four orthogonally arranged identical semitransparent antenna elements on a transparent substrate. The MIMO antenna covers the 2.4 GHz band and 3.2–15 GHz band, supporting automotive/wireless applications such as Bluetooth, Wi-Fi, intelligent transport system (ITS), advanced driver assistance systems (ADASs), vehicle to infrastructure (V2I), vehicle to vehicle (V2V), vehicle to network (V2N), and vehicle to device (V2D). The parameters such as envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and channel capacity loss (CCL) are studied to evaluate antenna diversity performance. The antenna has an ECC of less than 0.15, DG of more than 9.85 dB, TARC of less than −10 dB, and CCL of less than 0.2 bits/s/Hz. The developed antenna can be easily installed on the mirror and windshield of the vehicles. Also, the housing effect and on-vehicle performance of the antenna at various positions in a car are investigated. [ABSTRACT FROM AUTHOR]

This paper presents a flexible multiple-input, multiple-output (MIMO) antenna with ultrawideband (UWB) performance for smart clothing applications. The MIMO antenna is comprised of four octagonal-shaped radiators with several slots loaded into them, and it offers a frequency range of 2.9–12 GHz. The unit cell has a size of 0.26λ0 × 0.164λ0 × 0.014λ0 and the MIMO antenna has a size of 0.48λ0 × 0.48λ0 × 0.014λ0, where λ0 corresponds to the lowest operating frequency. The radiation and diversity performances of the antenna are evaluated, and the obtained metrics are envelope correlation coefficient (ECC) <0.045, diversity gain (DG) >9.9 dB, total active reflection coefficient (TARC) <−14 dB, and channel capacity loss (CCL) <0.13 bits/s/Hz. The bending analysis of the MIMO antenna is performed. The specific absorption rate (SAR) of the MIMO antenna is also investigated, and the obtained values are 0.229 W/Kg (4 GHz), 0.253 W/Kg (7 GHz), and 0.463 W/Kg (10 GHz). [ABSTRACT FROM AUTHOR]

This paper presents the design and development of a quad-port smart textile antenna for bio-healthcare applications. The antenna is designed to operate in the ultra-wideband (UWB) spectrum (3.1–12 GHz) with an impedance bandwidth of 8.9 GHz. The size of the unit cell and multiple-input multiple-output (MIMO) antenna are 0.25 λ 0 × 0.2 λ 0 × 0.015 λ 0 and 0.52 λ 0 × 0.52 λ 0 × 0.015 λ 0 , respectively. The antenna has a maximum efficiency of 93% and a peak gain of 4.62 dBi. The investigation of diversity metrics is performed and the results obtained are found to be ECC < 0.08 and DG < 9.99 dB. The computed CCL and TARC values are <0.13 bits/s/Hz and <−12 dB, respectively. The SAR analysis of the antenna shows a value of 0.471 Watt/Kg at 4 GHz, 0.39 Watt/Kg at 7 GHz, and 0.22 Watt/Kg at 10 GHz. [ABSTRACT FROM AUTHOR]

This paper presents the design of an Ultra‐wide band‐stop Frequency Selective Surface (FSS), the building block of which makes use of a modified Jerusalem cross loop structure. The proposed FSS unit cell has a coupled configuration with a modified Jerusalem cross loop on the top and a square loop on the rear side to operate over an ultra‐wide bandwidth. The proposed FSS design offers band‐stop characteristics over the entire UWB operating bandwidth extending from 2.95 to 12 GHz with a reference transmission loss of 10 dB. The proposed FSS unit cell has a miniaturized profile of 0.05λ˳ × 0.05λ˳ where the λ˳ corresponds to the free space wavelength at the lowest operating frequency. The rotational symmetry of the proposed FSS makes it polarization‐independent under both TE and TM modes of operation. Also, the proposed FSS exhibits a good angular stability response up to 60°. The prototype FSS is fabricated and the simulated results are validated using experimental measurements. Thus, the proposed FSS is a promising candidate for a multitude of applications such as spatial filtering (Bayatpur & Sarabandi, 2010, https://doi.org/10.1109/LMWC.2009.2038517), antenna gain enhancement (Chatterjee & Parui, 2016, https://doi.org/10.1109/TAP.2016.2552543), and electromagnetic shields (Chiu et al., 2008, https://doi.org/10.1109/TEMC.2008.2004560) operating over the UWB spectrum. Key Points: This paper presents the design of an Ultra‐wide band‐stop Frequency Selective Surface (FSS)The proposed FSS design offers band‐stop characteristics over the entire UWB operating bandwidthThe proposed FSS is a promising candidate for a multitude of applications such as spatial filtering, antenna gain enhancement [ABSTRACT FROM AUTHOR]

The proposed work is a novel low-profile 5G MIMO antenna configuration to exhibit dual-band frequencies for 5G NR-n2 band (1.9 GHz) and safety band (ITS-5.9 GHz) in vehicular communication. In the proposed antenna, it is quite difficult to achieve the lowest resonance frequency in a comparatively miniaturized dimension concerning its operating wavelength. The designed antenna is a modified square patch with the dual-band resonance achieved by the incorporation of slots for increasing the electrical length within the dimension. Hence, the design comprises ring and loop slots exhibiting resonance at 1.9 GHz and the loop U, and modified-W slots for 5.9 GHz. The antenna achieves 1.9% and 0.64% impedance bandwidth and a peak gain of 1.944dBi and 6.06dBi at the resonant frequencies of 1.9 GHz and 5.9 GHz, respectively, with dimensions of 0.114λo × 0.114λo × 0.0016λo, where λo is the wavelength of the lowest operating frequency. The MIMO configuration is presented to assess the antenna's suitability for large-scale applications. The MIMO antenna presented here is deployed with the edge-to-edge distance between the single element radiators being 0.01λo by parametric sweep. The presented MIMO antenna provides an isolation value greater than 19 dB because of reduced mutual coupling between the single element radiators in that MIMO structure due to the presence of a ground slot. The ECC values are 1.659 × 10−9 and 0.000601 for frequencies of 1.9 GHz and 5.9 GHz, respectively, and the diversity gain is relatively near 10 dB, which is the acceptable value for MIMO antennas. This modified square single-element and MIMO antenna provides a relatively higher gain and better performance in vehicular communication for GSM and safety applications. The MIMO configurations' on-vehicle analysis is performed to check the reliability of the designed antenna in a vehicular environment. [ABSTRACT FROM AUTHOR]

With the promising developments in wearable communication technology, attention towards flexible electronics is increasing day-by-day. This study presents flexible low-profile ultra-wideband (UWB) antennas for wearable applications. The antenna comprised of a modified dewdrop-inspired radiator and a defected ground plane and has an impedance bandwidth of 3.1–10.6 GHz. The antenna flexibility is investigated using four different substrates (polyester, polyamide, denim, and Teslin) and tested on a cotton shirt and a high-end Res-Q jacket to evaluate their performance stability for body-worn applications. The fabricated planar dewdrop-shaped radiator (PDSR) antennas have a radiation efficiency of >90%, a gain of >4 dBi, and a group delay variation of fewer than 0.5 ns. The antenna conformability is measured by placing the fabricated antennas on various curved and nonplanar parts of the human body. The aforementioned antennas offer better flexibility for different bent conditions. The specific absorption rate (SAR) of the designed antennas is investigated to determine their wearability, and values are found to be less than 0.2 W/Kg. Also, the received signal strength (RSS) is discussed in order to analyze signal attenuation, and the performance analysis of the antennas is compared. [ABSTRACT FROM AUTHOR]

This paper presents a low-profile, wideband antenna that can operate in four millimeter-wave frequency bands for 5G communication. The proposed antenna has composite geometry with extended blocks from a simple rectangular patch. Here the full ground plane is used to avoid the radiation losses by back lobes and to enhance the antenna performance. The proposed radiating element covers the wideband from 23.812 GHz to 48.253 GHz enclosing operating frequencies k band (26 GHz-F1) and Ka-band (28 GHz-F2, 32 GHz-F3, and 39 GHz-F4). The gains achieved in the designed single element antenna are 5.46 dBi, 5.6 dBi, 6.48 dBi, and 5.56 dBi respectively. Whereas the total efficiencies are 95.33%, 97.23%, 97.75%, and 97.9% for the respective operating frequencies. The proposed antenna is analyzed for Multiple Input Multiple Output (MIMO) communication, providing the isolation value greater than 20 dB. The diversity gain, Envelope Correlation Coefficient, and isolation are all well within their respective limits making the proposed antenna suitable for MIMO communications. Here, to check the versatility of the antenna design different configurations such as 2 × 2, 1 × 2, and port positionings are simulated. Furthermore, the designed single element and MIMO antenna is placed on the vehicle and the far-field results are analyzed. [ABSTRACT FROM AUTHOR]

An optically transparent circularly polarized (CP) radio frequency identification (RFID) antenna is presented in this paper. The RFID antenna consists of a coplanar‐fed waveguide inverted L‐shaped monopole with a dual feeding structure. The CP wave with a bidirectional radiation pattern is obtained by feeding the radiator at both ends. The transparency of the antenna is obtained by using fluorine tin oxide (FTO) coated soda‐lime glass substrate. The proposed antenna operates at a Universal RFID frequency (800–1100 MHz) with circular polarization. The antenna has an impedance bandwidth of 300 MHz and an overlapped 3‐dB axial ratio (AR) bandwidth of 110 MHz (860–970 MHz, 12% centered at 915 MHz). It has a peak realized gain of 1.4 dBic. The antenna with the size of 100 × 100 mm2 is designed for ultrahigh‐frequency RFID reader applications. [ABSTRACT FROM AUTHOR]

This paper presents a twelve-port ultra-wideband multiple-input-multiple-output (MIMO)/diversity antenna integrated with GSM and Bluetooth bands. The twelve-port antenna is constructed by arranging four elements in the horizontal plane and eight elements in the vertical plane. The antenna element, which is created using a simple rectangular monopole, exhibits a frequency range of 3.1 to 12 GHz. The additional Bluetooth and GSM bands are achieved by introducing stubs into the ground plane. The size of the MIMO antenna is 100 × 100 mm2. The antenna offers polarization diversity, with vertical and horizontal polarization in each plane. The diversity antenna has a bandwidth of 1.7–1.9 GHz, 2.35–2.55 GHz, and 3–12 GHz, the radiation efficiency of 90%, and peak gain of 2.19 dBi. The proposed antenna offers an envelope correlation coefficient of < 0.12, apparent diversity gain of > 9.9 dB, effective diversity gain of > 8.9 dB, mean effective gain of < 1 dB, and channel capacity loss of < 0.35 bits/s/Hz. Also, the MIMO antenna is tested for housing effects in order to determine its suitability for automotive applications. [ABSTRACT FROM AUTHOR]

A compact body-worn circular polarized textile monopole antenna for wearable applications is reported. The proposed antenna is fabricated on a jean fabric providing flexibility, lightweight, and easy integration into human clothes. The overall size of the proposed antenna is $25\times 30\times1.4$ mm3. Circular polarization (CP) is advantageous for on-body communication as it provides features, such as multipath immunity, suppressing interferences, and enables better link connectivity between the sensor nodes. The proposed antenna achieves the CP using an asymmetric stepped L-shaped ground plane and through the incorporation of a cross-shaped stub in the radiator. The single-fed octagonal strip monopole antenna provides good impedance matching over the entire ultrawide frequency range from 3.09 to 11 GHz. Simulation results are in good correlation with the measured results. The axial ratio bandwidth <3 dB is achieved in the frequency range of 3.4–10 GHz. Gain and efficiency obtained are about 2.3-4.4 dBi and 65%–82% at the said frequency range, respectively. Structural deformation is performed to analyze the flexibility of the proposed antenna. The simulated SAR values follow the FCC limit making it most suitable for wearable applications. [ABSTRACT FROM AUTHOR]

A conformal four-port multiple-input-multiple-output (MIMO) antenna operating at 2.4 GHz and ultrawideband (UWB) is presented for wearable applications. The unit element of the MIMO antenna is a simple rectangular monopole with an impedance bandwidth of 8.9 GHz (3.1–12 GHz). In the monopole radiator, stubs are introduced to achieve 2.4 GHz resonance. Also, a defect is introduced in the ground plane to reduce backside radiation. The efficiency of the proposed antenna is greater than 95%, and its peak gain is 3.1 dBi. The MIMO antenna has an isolation of >20 dB, and the estimated specific absorption rate (SAR) values for 1 gm of tissue are below 1.6 W/Kg. The size of the four-port MIMO antenna is 1.38λ0 × 0.08λ0 × 0.014λ0. [ABSTRACT FROM AUTHOR]

The design of a silicone rubber-based wristband wearable antenna exploiting pattern diversity is presented in this paper. The wristband diversity antenna consists of four identical antenna elements with an inter-element spacing of 0.68λ0, where λ0 is the lower cut-off wavelength. A modified trapezoidal-shaped radiator with a rectangular ground structure is used to achieve ultra-wide bandwidth. The proposed multiple-input-multiple-output (MIMO)/diversity antenna covers a frequency range of 2.75–12 GHz. The antenna element offers a radiation efficiency of 89.3% and a gain of 3.41 dBi. The size of the wristband diversity antenna is 1.1λ0 × 18.4λ0 × 0.18λ0. The diversity performance characteristics of the prototype antenna are examined, with the envelope correlation coefficient (ECC) < 0.18, apparent diversity gain (ADG) > 9.5, effective diversity gain (EDG) > 9.5, mean effective gain (MEG) < 1 dB, total active reflection coefficient (TARC) < − 10 dB, and channel capacity loss (CCL) < 0.1 bits/s/Hz over the entire operating band. The specific absorption rate (SAR) of the proposed wristband antenna is analyzed to determine its radiation exposure on the human body, and the results show that the values are less than 0.02 W/kg. [ABSTRACT FROM AUTHOR]

In this communication, a compact dual‐element MIMO antenna with decoupling structure has been proposed for handheld devices. The proposed decoupling structure acts as a resonator and as a decoupling structure. The proposed antenna consists of nested slots in the radiator and it supports the application such as LTE, WLAN, Wi‐Fi, and WiMAX. The total size of the antenna is 30 mm × 10 mm. The impedance bandwidth of the antenna is 300/400/700 MHz, respectively. The decoupling structure consists of a feed line printed on one side of the substrate and swastika‐shaped array on another side. The power fed to the feed line coupled to the swastika‐shaped array for achieving the operating bands at 0.9 GHz and (8‐10) GHz. Meanwhile, the decoupling array provides isolation more than 20 dB at (2.3‐2.6) GHz, (3.4‐3.8) GHz, and (5.15‐5.85) GHz. The edge to edge spacing between the antennas is 10 mm. The percentage bandwidth of the antenna is 12.2/11.1/12.7/22.2%. The MIMO performance metrics such as envelope correlation coefficient, effective diversity gain, apparent diversity gain, and mean effective gain are evaluated. The proposed antenna is fabricated and tested. The measured results correlate with the simulated results. [ABSTRACT FROM AUTHOR]

This paper presents a reconfigurable loop-based filter performing compound reconfiguration. The designed filter is capable of functioning as a bandstop or bandpass filter by a simple approach of cascading the resonator to the transmission line connecting source and load. Shifting of operating frequencies is characterised by switching between a loop and a C-shaped resonator. To demonstrate the working of the proposed concept, a compound reconfigurable filter operating at 1.5 GHz and 1.6 GHz is developed. The filter is developed on a compact layout of size 0.27 × 0.12 λg2. The proposed prototype is fabricated and measured for real-time validation. [ABSTRACT FROM AUTHOR]

The design, development, fabrication, and testing of a wideband reflectarray antenna with a novel concentric ring element operating over Ku/K band frequencies is presented in this paper. The element characterization is performed using the infinite array approach and is inferred that the proposed unit cell offers a higher phase variation of 643° by changing the size of the concentric rings. The proposed reflectarray antenna has a circular geometry and is constructed using 437 elements with an element separation of 0.43λ0. The proposed reflectarray offers a 3 dB gain bandwidth of 35% (15–21 GHz). The aperture efficiency is estimated to be 58.78% at 16.5 GHz. The prototype reflectarray is fabricated and tested to validate the simulation results. The measured peak gain of the reflectarray is 28.4 dBi with a side lobe level of −17.6 dB. The measured cross‐polarization level is less than −32 dB. Furthermore, it is inferred that the proposed unit cell has a reduced maximum phase sensitivity of 246°/mm with a gain selectivity of 6 dB at the lowest operating frequency. The proposed broadband reflectarray with enhanced performance characteristics is suitable for application in satellite communication and aeronautical radio navigation. [ABSTRACT FROM AUTHOR]

This article presents a compact reconfigurable filter performing bandwidth reconfiguration covering the entire L‐band frequency range. The reconfigurable filter is developed using a C‐shaped resonator coupled to the source and load through varactor diodes. To reverse bias the diodes symmetrically both the diodes are fed with a common bias voltage. Hence the DC bias voltage is administered evenly to the diodes resulting is equi‐proportional coupling between the resonator and the nodes. This results in reconfiguring the bandwidth of the operating frequency. The designed filter is capable of tuning 3‐dB bandwidth from 0.613 to 1.353 GHz with the center frequency as 1.5 GHz. The percentage bandwidth of the filter is varied from 44.5% to 91.76%. The insertion loss offered by the filter is very less with the minimum value of 0.42 dB. The proposed filter is simple, compact and finds it application in power agile systems operating with different transmission power levels at different time instances. [ABSTRACT FROM AUTHOR]

A low profile, a multifrequency microstrip patch antenna with pattern reconfiguration is reported in this paper. The proposed antenna provides both omnidirectional and directional radiation characteristics suitable for Wireless Body Area Network (WBAN). Pattern switching is achieved using PIN diodes. The antenna is designed to operate at multiple frequencies, viz. 0.915 GHz (Industrial Scientific & Medical band), 2.38 GHz (Medical body area network), 3.5 GHz (Wireless Interoperability for Microwave Access), and 5.8 GHz (Wireless Local Area Network/Industrial Scientific & Medical band). The percentage bandwidths obtained are 2.89, 1.68, 2.85, 2.16 at the operating frequencies 0.915, 2.38, 3.5, 5.8 GHz, respectively. The peak gain and total efficiencies obtained for OFF mode are 3.22/4.27/4.65/4.82 dBi, 82/85/87/89%, and in ON mode are 1.12/1.80/2.44/2.68 dBi, 65/67/71/74% at the said operating bands, respectively. The path loss model is evaluated by measuring the transmission link between the antennas on the human body. The LOS path ranges from 30 to 45 dB and the NLOS ranges from 50 to 80 dB ensuring it satisfactory for WBAN application. Then human body loading characteristics are also studied. The SAR analysis is performed and it is found to be less than 1.6 W/Kg. [ABSTRACT FROM AUTHOR]

This paper details the construction and working of a compound reconfigurable filter capable of frequency and bandwidth reconfiguration in the frequency range from 2 to 3 GHz. The switching between frequency and bandwidth reconfiguration is inherited by two PIN diodes. Bandwidth tuning is facilitated by tuning two transmission zeros individually using varactor diodes, giving flexibility in reconfiguring the upper and lower pass edges. The two transmission zeros are obtained using simple concentric square loop resonators. The maximum bandwidth obtained is 1.5 times the minimum bandwidth offered by the filter. Hence the filter can be used for dynamic bandwidth allocation. This prototype is fabricated and validated in real-time. The simulated and measured results are analogous to each other. [ABSTRACT FROM AUTHOR]

Contemplating the advancements in communication technology, the analysis of the features of reflectarray, transmitarray, and transmit‐reflectarray becomes essential for future adaptability. This article presents a thorough review of such high‐gain antennas, presenting some of the most relevant solutions published by the scientific society in the field of antennas and wave propagation. Several examples of unit cells for array implementation and complete array designs discussed in various literatures are analyzed. The analysis is focused in identifying the unit cell layouts, such as those developed using microstrip patches, frequency selective surfaces, or metamaterials. The analysis is extended to the ways of improving bandwidth, for example, true time delay elements, phase delay lines, meander lines, and so on, and the various methods used to enable reconfiguration, for example, p‐i‐n diodes, varactor diodes, or microelectromechanical systems. In addition, some antennas, which produce bidirectional beams simultaneously, are also discussed. Finally, all the models are compared against each other in order to highlight their benefits and limitations, summarizing their main characteristics, such as the frequency of operation, bandwidth, phase range, gain, aperture efficiency, sidelobe levels, cross polarization levels, and maximum beam‐steering range. [ABSTRACT FROM AUTHOR]

A compact, low-profile button antenna for off-body communication is reported. The proposed antenna is composed of coupled circular strips, Y-shaped and L-shaped slots. This configuration covers the application bands such as 0.867 GHz (industrial, scientific, and medical bands), 2.38 GHz (medical body area network), and 5.8 GHz (wireless local area network/industrial, scientific, and medical bands). The percentage bandwidth obtained at the said operating bands is 4.37, 2.10, and 2.56, respectively. The directional radiation pattern obtained from the developed antenna ensures the low backward radiation to the body tissue, thereby, making it more suitable for WBAN applications. The simulated gain and efficiency obtained at the operating bands are 2.5/3.52/4.8 dBi and 78%/85%/89%, respectively. To validate the simulation results, the antenna is fabricated and some experimental results on the body tissue are performed. The SAR value obtained follows the Federal Communication Commission (FCC) limit. [ABSTRACT FROM AUTHOR]

A novel compact monopole antenna with integrated services for 4G/5G application has been proposed in this manuscript. The 4G services such as Long Term Evolution (LTE) and GSM 850/900 is provided by the primary antenna of size 45 × 15 mm. The 5G communication services are supported by the auxiliary antenna of size 19 × 15 mm. The monopole radiator with the combination of multi-branch stubs and meandered structures in the primary radiator introduces the resonance at the desired operating frequency. The impedance bandwidth of the primary antenna is 170 MHz (0.8–0.97 GHz) and 900 MHz (1.8–2.7 GHz) for LTE and GSM applications. The impedance bandwidth of the auxiliary antenna is 7 GHz (13–20 GHz) for 5G application bands. To achieve the desired operating bands, the length and width of the stubs are used as the tuning parameters. The large ground plane of size 200 × 150 mm is used as the mock-up system for the proposed antenna structure. To enhance the coverage of the handheld devices, the primary and auxiliary antenna is integrated in the mock-up system. The efficiency and gain of the antenna are in the range of 3–5 dBi and 70–96%. The simulated and measured results are correlated with each other. [ABSTRACT FROM AUTHOR]

This communication presents the design of a compact loop antenna with independent frequency tuning. The proposed antenna consists of a feed line fed by a $50~\Omega $ coaxial probe and four resonating arms on the adjacent sides of the feed line. The two outer resonating arms are directly coupled to the feed line and the other two inner resonating arms are coupled to the outer arms. The proposed antenna has a footprint of 25 mm $\times 10$ mm $\times0.2$ mm. The designed antenna operates at 0.9, 2.4, 3.5, and 5.5 GHz. Each of these bands is individually tuned using varactor diodes. Thus, the aggregation of these tunable bands provides wide bandwidth. The impedance bandwidth and percentage bandwidth of the antenna are 270/1000/400/700 MHz and 33%/47.6%/11%/12.7%, respectively. Furthermore, the gain and efficiency of the antenna are 1.7/1.3/2.1/2 dBi and 60%/63%/65%/69%, respectively. The prototype antenna is fabricated and tested. The measured impedance and radiation characteristics of the antenna are in good correlation with the simulation results. [ABSTRACT FROM AUTHOR]

A compact, low-profile ultrawideband directional antenna for a wireless body area network (WBAN) is reported in this letter. The directional antenna is designed using a monopole backed with an electromagnetic bandgap (EBG) structure, which acts as a reflector. The beveled Y-shaped monopole antenna covers the ultrawide bandwidth from 3.1 to 10.6 GHz. The monopole antenna backed with a fork-slotted EBG is designed with a size of 8 × 8 mm2. The 2 × 1 EBG array is printed on the same plane above the partial ground. This integrated structure provides band-stop characteristics from 3.1 to 10.6 GHz with a directional radiation pattern intended for wearable applications. It also acts as a protective shield against the electromagnetic radiation emerging from the monopole antenna toward the body tissue. The proposed directional antenna provides a peak gain of 6.25 dBi with high radiation and total efficiency. The calculated specific absorption rate value is 0.695 W/Kg, which is well below the desired 1.6 W/kg. [ABSTRACT FROM AUTHOR]

This manuscript presents the design of a size reduced microstrip rat-race (RR) coupler with improved spurious passband suppression performance. The coupler operates at 0.95 GHz, corresponding to 5G applications (sub-1 GHz 5G applications). The combined effect of coupled microstrip lines, slant connected split ring structure and the ring shaped defects offer deep suppression of harmonic signals beyond the passband till 4 GHz. The proposed coupler also offers 47.2% size reduction compared to a conventional RR coupler model. [ABSTRACT FROM AUTHOR]

A novel ellipsoid slot array integrated with the compact MIMO antenna accomplishes the increasing demand of customers with 4G and 5G application bands. The proposed antenna incorporates a front FR4 layer holding a planar radiator, ground plane etched with ellipsoid slot array and back FR4 layer with the corporate feed network. The corporate feed network delivers power to the framework of 2 × 4 matrix ellipsoid slot array in the ground plane. The front and the back FR4 layer are detached by the ground plane, which acts as both radiator as well as isolator. The ground plane containing ellipsoid slot array antenna resonates at 17 GHz. It also provides 25 dB isolation in the LTE application bands. This antenna arrangement achieves the impedance bandwidth of 600 MHz (2–2.6) GHz for LTE 2300 MHz, LTE 2500 MHz and 2 GHz (15–17) GHz for 17 GHz 5G application band. Apart from this, the simulated gain of 3.33/4.67/7.5 dBi and measured gain of 3.01/4.58/7.3 dBi is achieved for resonating frequencies such as 2.3/2.5/17 GHz. High efficiency of 84/91/90% is obtained for microwave and millimeter wave frequencies. Envelope correlation coefficient evaluated from the radiation pattern is found to be < 0.5. [ABSTRACT FROM AUTHOR]

This communication presents the design, fabrication, and testing of a tunable band-notched UWB filtering antenna. The proposed filtering antenna comprises a semiellipsoid radiator and a microstrip transmission line to cover the UWB communication bandwidth from 3.1 to 10.6 GHz. It also comprises two J-shaped open-ended stubs and an asymmetric T-shaped open-ended stub to create notch bands at 3.5 GHz (WiMAX), 5.2 GHz, and 5.8 GHz (WLAN) in the UWB spectrum. The center frequencies of the notch band are tuned continuously using varactors with percentage tuning of 7.5%, 5.38%, and 3.54%. The prototype is fabricated and experimentally validated. [ABSTRACT FROM AUTHOR]

A microstrip bandwidth reconfigurable filtering antenna is implemented by simply tuning the transmission zeroes. The proposed filtering antenna is developed by integrating the filter characteristics into the 50 Ω microstrip feed line of the antenna through two independent coupled resonators. The energy coupling between the transmission line and the planar loop resonator and dual F shaped resonator generates the transmission zeroes. These transmission zeroes at specified lower frequencies are generated in order to provide better selectivity over the edges of the pass band to promote high suppression of interferences. The varactor diodes are explicitly loaded at distinct locations in the resonators to achieve bandwidth reconfiguration. The two transmission zeros are tuned between 1.6-1.9 GHz and 2.1-2.42 GHz respectively by varying the capacitance of the two varactor diodes with percentage bandwidth of 17.1% and 14.1% respectively to support mobile and wireless short range applications. The proposed filtenna provides insertion loss less than 3 dB with good impedance matching below 15 dB. [ABSTRACT FROM AUTHOR]

In this paper, a portable system for noninvasive detection of fractures in human bones is presented. A planar microwave ring resonator is used as the sensor. The proposed planar microwave sensor is designed using the finite integration-based CST Microwave Studio and tested on a human bone covered by porcine tissues. Fracture induced in the bone was detected by monitoring the transmission characteristics of the sensor as it scans the affected region. The resonant frequency of the ring resonator has been observed at every scan point, and the values are plotted using iterative curvature-based interpolation, improved new edge directed interpolation, and Lanczos imaging technique. The extent of fracture is then derived from the image. The average accuracy of the detected fracture for Lanczos method of resampling was 98.86%. The specific absorption rate was below the minimum level of 1.6 W/Kg at every point of scanning. Portable noninvasive monitoring of fractures in the tibial bone will help in immobilizing the affected part at an earlier stage, thereby reducing the recovery time for patients. [ABSTRACT FROM AUTHOR]

In this paper, a compact, single-section, Ultra-wideband (UWB) coupled-line coupler designed using concentric loop in the signal plane and defect in the ground plane is presented. Bandwidth enhancement is achieved with low coupling at the X-band satellite downlink range to improve the signal strength for defence applications. Return loss greater than 15 dB and isolation greater than 20 dB is achieved over the entire UWB band. The prototype is fabricated and tested to validate the simulation results. Further to detect the quality of the output signal, signal integrity analysis is performed and metrics such as error vector magnitude (EVM), magnitude and phase error, eye pattern, constellation plots and signal to noise ratio are presented for the proposed UWB coupled-line coupler. [ABSTRACT FROM AUTHOR]

For the first time, paper-based SWB fractal monopole antenna is presented. A miniaturized SWB monopole, which deploys a fractal radiator, is the smallest reported paper-based SWB monopole antenna to date. It is shown that fractal made of iterations of a flower shaped slot inside a circular metallic patch provides a successful method of reducing size while retaining or enhancing antenna performance. This paper presents the design of SWB monopole antenna for flexible applications and is validated for UWB applications. The proposed antenna has a wide impedance bandwidth (-10 dB bandwidth) from 3.3 GHz to frequency over 30 GHz. The aforementioned antenna with a compact size 18 mm × 24 mm is designed and fabricated on a paper substrate of 0.5 mm thickness. The main features like environment friendly, flexibility, green electronics applications and low cost of fabrication are the key factors for this proposed antenna. The proposed antenna has a 14-dB bandwidth from 3.9 GHz to 13.1 GHz, which is suitable for UWB outdoor propagation. Bending measurements have been performed to validate the flexibility of the prototype under extremely bent condition of bent radius 10 mm. The possible applications cover WLAN, C-band, Ku-band, K-band operations, WiMAX and ISM band. [ABSTRACT FROM AUTHOR]

A compact frequency-agile multiband filtenna is presented in this letter. The proposed reconfigurable filtering antenna performs independent switching between four operating bands viz. 1.8 GHz (GSM), 2.4 GHz (Bluetooth), 3.5 GHz (WiMAX), and 5.2 GHz (WLAN). This switching allows the unused bands to be utilized by the secondary user, making the antenna suitable for cognitive radio applications. An elliptical wideband monopole antenna is excited through a reconfigurable bandpass filter (BPF) integrated onto the 50 Ω transmission line. The BPF comprises four distinct structures to tune to four different frequencies using p-i-n diodes. The proposed filtenna has the reflection coefficient less than −20 dB for all the desired operating bands. Furthermore, this multiband filtenna offers gain of about 1.1, 2.6, 3, and 3.4 dBi at the four frequency bands. The prototype filtenna is fabricated, and the simulation results are verified experimentally. [ABSTRACT FROM AUTHOR]

Abstract: This article presents the design and testing of a novel frequency reconfigurable microwave filter. The filter structure is composed of an all stop resonator coupled with C‐ and E‐shaped parasitic resonators. PIN diodes are located at suitable positions to achieve multi‐band reconfiguration from 1.2 to 3.2 GHz making the filter suitable for multiple wireless communication systems. The frequency and bandwidth of the filter are governed by the length of the resonators and coupling between the resonators and the transmission line, respectively. A sharp rejection of −30 dB is observed between the passbands. The proposed filter offers 56% size reduction with flat group delay performance. The prototype filter is fabricated and the simulation results are validated using experimental measurements. The measurement results show good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

In this manuscript, a novel uniplanar monopole antenna for Tablet computer application is proposed. Multiband resonance is obtained by introducing multiple radiating branches and meandered stubs connected to the main monopole. Further, the impedance bandwidth of the operating bands is enhanced by introducing coupled parasitic stubs in the ground plane. The antenna has impedance bandwidth of 20 MHz (0.45-0.47 GHz), 270 MHz (0.69-0.96 GHz), 2370 MHz (1.43-3.8 GHz), 1600 MHz (4.9-6.5 GHz) for LTE 450/700/2300/2500 MHz, GPS, WLAN, Bluetooth applications, WiMAX and Wi-Fi applications. The size reduction of the proposed antenna is 60% compared to existing antenna solutions for tablet devices. The percentage bandwidth of the antenna is 4.35/34.2/90.6/23.2% for the four operating bands, respectively. Furthermore, the obtained gain of the antenna is greater than 1.8 dBi with peak gain of 5.65 dBi, and the efficiency is greater than 75%. The proposed antenna is tested on the mock-up system consisting of large ground plane of dimension 200 × 150 mm. The antenna is fabricated, and the measured results are compared with simulated results. The SAR is computed and found to be less than 1.6 W/Kg. [ABSTRACT FROM AUTHOR]

The design, fabrication, and testing of an integrated polarization diversity antenna array for maximizing the wireless channel link in vehicular networks are presented in this paper. The diversity antenna is constructed using unit cell radiators that provide two operating modes. The mode transition is achieved using a pair of PIN diodes. In one state, the antenna provides multiband operation centered at 2.4, 3.5, and 5.8 GHz. In the other state, the antenna covers the entire ultra-wideband (UWB) spectrum. The unit cell radiators are distributed in the horizontal and vertical plane to achieve polarization diversity. Apart from offering a polarization diversity antenna, the orientation of antennas offers a reliable link with the communication devices. The prototype antenna array is fabricated and tested for diversity performance. The performance metrics such as envelope correlation coefficient, diversity gain, and mean effective gain under isotropic, indoor, and outdoor conditions are evaluated and presented. [ABSTRACT FROM AUTHOR]

This letter presents the design of a novel compound reconfigurable antenna array for WiMAX and WLAN application. The proposed array consists of a unit-cell antenna composed of a truncated circular radiator, C-shaped parasitic elements, and perturbed rhombic slot element. A compound reconfigurable unit-cell antenna element loaded with p-i-n diodes is investigated, and using the inference made, a 1 × 2 array is designed to increase the gain and efficiency of the dynamic antenna. In the first case, slot antenna alone gets excited with the feedlines of 0° and 90° phase difference to achieve pattern and polarization reconfiguration for WiMAX applications. In the other case, the patch is excited at the WLAN band and, with the help of parasitic elements, pattern tilting at 0° and ±30° is obtained. The proposed antenna array is fabricated, and the simulation results are verified using experimental measurements. [ABSTRACT FROM AUTHOR]

A reconfigurable frequency-selective surface (RFSS) for electromagnetic shielding applications is presented in this letter. The unit cell of the proposed RFSS contains a pair of shorted square loops separated by a uniform distance. Wideband RFSS with the frequency tuning ratio of 1:2.34 achieved by varying the horizontal spacing is proposed. The RFSS covers the frequencies 3.5, 5, and 5.8 GHz shielding the WiMAX, WLAN, and ISM/WiMAX bands, respectively. The prototype of the proposed RFSS is fabricated and loaded on to the mechanical tuning setup. The tuning setup has a box frame with rotating shafts attached to the bevel gears to control the horizontal spacing. The use of collapsible linkage mechanism ensures uniform spacing during reconfigurable operation. The simulated results are validated with measurements. The proposed FSS offers wideband frequency tuning for electromagnetic shielding applications. [ABSTRACT FROM AUTHOR]

In this paper, a novel planar microwave sensor for nondestructive measurement of strain during testing of printed circuit board (PCBs) is proposed. Planar microstrip patch bridged on both sides with squared split ring resonator is used to measure strain. Measurement of stress of isotropic dielectric materials in their linear elastic region that are uses as PCB substrates is also done using the proposed method. The designed microwave probe works at a frequency of 2.45 GHz. The feasibility of the use of time-domain reflectometry method to monitor strain in materials is presented here. The proposed sensor exhibits a sensitivity of about 333 ps for every 1% change in strain. Finite integration technique and real-time measurements have been done to corroborate the relation derived between the transmit time and the strain experienced by the material. The correlation between the simulated and measured strain is about 99.3%. The proposed sensor can be used for faster and accurate testing of PCB substrates without requiring complex calibrations. [ABSTRACT FROM PUBLISHER]