T-shaped Slot Research Articles

In-Band Radar Cross-Section Reduction of Slot Antenna Using Characteristic Modes

In this letter, a methodology for achieving in-band radar cross-section (RCS) reduction of slot antennas is proposed. This method is based on the characteristic mode (CM) analysis of the slot antenna to distinguish radiation modes and scattering modes. Several CM indicators, including the modal currents, the modal significance, and the modal weighting coefficient (MWC), are calculated to provide systematic guidelines on suppressing scattering modes while keeping the radiation modes work properly. Following the specific mode characteristics, two techniques are proposed to reduce the MWC for each scattering mode. First, reactance components are placed at optimal locations over the antenna to shift the resonant frequency of a particular scattering mode out of the operation frequency band. Second, additional slots are introduced to disrupt the current path and thus reduce the bandwidth of the scattering mode. The proposed methodology is validated through the design of a low RCS T-shaped slot antenna. The experimental results show that the design has not introduced deterioration in radiation characteristic, while show remarkable RCS reduction. The proposed antenna achieves at least 5 dB reductions over the wide operation frequency band (59.6% bandwidth) of the T-shaped slot antenna.

A flexible fixture design method research for similar automotive body parts of different automobiles

This article proposes a flexible fixture system design method for similar automotive body parts, which contains structure and locating control algorithm design of a flexible fixture. This flexible fixture system is composed of a base part, some locating units, and a control system, which can finish locating adjustments of end locating blocks or pins in three coordinate axle directions. Locating units contain adjusting mechanisms which can complete one horizontal direction and one vertical direction locating adjustments, and the control system can compute locating adjustment components of locating units and drive adjusting mechanisms of locating units to realize locating adjustments and clamping parts. The other horizontal direction locating adjustment is obtained through manually moving locating units along T-shaped slots in the base part. Finally, a flexible fixture system case for automotive body roofs is provided to demonstrate the flexible fixture structure and locating adjustment processes. It shows that the roof flexible fixture system can be adjusted for similar automotive roofs by its adjusting mechanisms and manual operation and then repeating fixture construction cost will be greatly decreased when a new automotive body is manufactured. This flexible fixture system can also be applied for other automotive body parts through some changes of a base part and locating units according to locating layouts of new parts.

A microstrip UWB antenna for next generation communication system

A novel microstrip truncated ultra-wideband (UWB) antenna with T-shaped band notching is implemented for insusceptibility at 5.2 GHz to 5.8 GHz and can be used in next generation wireless communication. Agreeing to the obligation to spread the bandwidth of antenna more, the T-shaped slot is cut on the spot with a height of 1.50 mm, and T-shaped notching is designed to achieve a manifold frequency band. In this work, a dielectric material of 2.2 and lossless tangent .4 is applied. The optimal results are obtained by selecting the parameters of an antenna. The return loss and gain of the proposed structure is –46.1 dB and 5.49 dB. The proposed antenna can see its application in cellular communication, X-ray, and W-LAN.

A microstrip UWB antenna for next generation communication system

A novel microstrip truncated ultra-wideband (UWB) antenna with T-shaped band notching is implemented for insusceptibility at 5.2 GHz to 5.8 GHz and can be used in next generation wireless communication. Agreeing to the obligation to spread the bandwidth of antenna more, the T-shaped slot is cut on the spot with a height of 1.50 mm, and T-shaped notching is designed to achieve a manifold frequency band. In this work, a dielectric material of 2.2 and lossless tangent .4 is applied. The optimal results are obtained by selecting the parameters of an antenna. The return loss and gain of the proposed structure is –46.1 dB and 5.49 dB. The proposed antenna can see its application in cellular communication, X-ray, and W-LAN.

Trident-shape strip loaded dual band-notched UWB MIMO antenna for portable device applications

In this paper, a novel compact dual band-notched ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna of size 22×26×0.8mm3 is proposed for portable devices. The antenna comprises of two stepped slot UWB antennas fed by 50ohms microstrip line, T-shape slot and narrow slot. Dual band-notches from 5.4 to 5.86GHz and 7.6–8.4GHz are achieved by loading trident-shape strips on microstrip line. A T-shape slot is used on the ground plane to enhance impedance matching characteristics and to minimize mutual coupling above 4GHz. To improve isolation further at 3–4GHz, a narrow slot is used on ground. The proposed antenna is giving a good bandwidth ranging from 3.1 to 11.8GHz with |S11|>10dB and mutual coupling larger than 20dB in the entire operating band except at two rejected bands. The simulation and measurement results demonstrate that the antenna is more suitable for portable device applications.

Performances of Symmetric and Asymmetric T-slot Microstrip Antennas for Bluetooth Communication

Bluetooth is a short distance unlicensed wireless communication technology operating at 2.4 GHz band and primarily used for data transfer between portable devices. In this paper, small size microstrip patch antennas, loaded by symmetric and asymmetric T-shaped slots are designed and a comparative study of their performance at Bluetooth frequency band is presented. High frequency structure simulator (HFSS) software is used for antenna simulation. Improved bandwidth, uniform radiation pattern and good gain of the antenna are achieved using asymmetric T-slot microstrip antenna compared to symmetric T-slot microstrip antenna. The dimension of asymmetric T-slot microstrip antenna is 75% less than the symmetric T-slot microstrip antenna. Performance of the antennas, through parametric studies, related to the dimensions of the symmetric and asymmetric T-slots, is also presented. Â

Compact Planar Ultrawideband Antennas with 3.5/5.2/5.8 GHz Triple Band-Notched Characteristics for Internet of Things Applications

Ultrawideband (UWB) antennas, as core devices in high-speed wireless communication, are widely applied to mobile handsets, wireless sensor networks, and Internet of Things (IoT). A compact printed monopole antenna for UWB applications with triple band-notched characteristics is proposed in this paper. The antenna has a very compact size of 10 × 16 mm2 and is composed of a square slotted radiation patch and a narrow rectangular ground plane on the back of the substrate. First, by etching a pair of inverted T-shaped slots at the bottom of the radiation patch, one notched band at 5–6 GHz for rejecting the Wireless Local Area Network (WLAN) is generated. Then, by cutting a comb-shaped slot on the top of the radiation patch, a second notched band for rejecting 3.5 GHz Worldwide Interoperability for Microwave Access (WiMAX) is obtained. Further, by cutting a pair of rectangular slots and a C-shaped slot as well as adding a pair of small square parasitic patches at the center of the radiating patch, two separate notched bands for rejecting 5.2 GHz lower WLAN and 5.8 GHz upper WLAN are realized, respectively. Additionally, by integrating the slotted radiation patch with the narrow rectangular ground plane, an enhanced impedance bandwidth can be achieved, especially at the higher band. The antenna consists of linear symmetrical sections only and is easy for fabrication and fine-tuning. The measured results show that the designed antenna provides a wide impedance bandwidth of 150% from 2.12 to 14.80 GHz for VSWR < 2, except for three notched bands of 3.36–4.16, 4.92–5.36, and 5.68–6.0 GHz. Additionally, the antenna exhibits nearly omnidirectional radiation characteristics, low gain at the stopbands, and flat group delay over the whole UWB except at the stopbands. Simulated and experimental results show that the proposed antenna can provide good frequency-domain and time-domain performances at desired UWB frequencies and be an attractive candidate for portable IoT applications.

A Dual-Band Inverted-F MIMO Antenna With Enhanced Isolation for WLAN Applications

This letter presents a dual-band inverted-F multiple-input-multiple-output (MIMO) antenna with improved isolation, covering the 2.4/5-GHz wireless local networks (WLAN) band. The proposed MIMO antenna is composed of two symmetrical winding inverted-F antenna elements. The two antenna elements are closely spaced with about 0.115 λ 0 of the lower band. The high isolation is achieved by building two decoupling devices, a meandering resonant branch and an inverted T-shaped slot etched on the ground for the higher band and the lower band, respectively. Furthermore, two U-shaped slits achieving better impedance matching are etched on the 50-Ω feeding lines to broaden the bandwidth of the high band. The impedance bandwidth (S 11 <; -10 dB) of the proposed antenna covers 2.4-2.48 GHz in the lower band and 5.15-5.825 GHz in the upper band, and the proposed configuration obtains 15-dB isolation within the 2.4- and 5-GHz WLAN bands, which shows a significant improvement compared to the initial design of the MIMO antenna. The simulation and measurement results indicate that the proposed inverted-F MIMO antenna system is quite suitable for WLAN applications.

Compact Dual-Polarized Printed Slot Antenna

A dual-polarized printed slot antenna is constructed by inserting the open-end slot into the coplanar waveguide center conductor of T-shaped slot. In order to verify the antenna performance, an antenna prototype was fabricated. The experimental results show that its working bandwidth is about 10.5%. In the operating frequency band, the isolation between two ports is higher than 27 dB. The proposed two-port antenna has bidirectional radiation characteristics, but the gain of the T-shaped slot element is higher than that of the open-end slot element. In the maximum radiation direction, the copolarization level of the T-shaped slot is 39 dB higher than the cross polarization and 30 dB for the open-end slot. The proposed dual-polarized antenna has a compact structure.

Bandwidth Enhancement of Small Slot Antenna with a Variable Band-Stop Function

In this paper, a novel and compact design of microstrip slot antenna with band-notched characteristic for UWB application is proposed. In the proposed design, an inverted T-shaped slot at the square radiating stub is used to create an additional resonance at the higher frequencies. By obtaining this resonance, the usable upper frequency of the antenna is extended from 10.3 to 17.6 GHz which provides more than 140 % fractional bandwidth. Additionally, by cutting a pair of step-shaped slits in the ground plane, a desired frequency band-stop performance has been obtained. Experimental results obtained for this antenna show that it exhibits good gain and radiation pattern characteristics within the UWB frequency range. The proposed antenna can operate from 2.9 to 17.1 GHz for VSWR <2 with a rejection band around of 5–6 GHz to suppress any interference from wireless local area network systems. Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for UWB applications.

Compact isolation-enhanced UWB MIMO antenna with band-notch character

In this paper, a compact multiple-input multiple-output antenna with band-notched characteristic is presented for Ultra-Wideband (UWB) applications. Two orthogonally placed radiator elements excite the same open slot which consists of two connected T-shaped slots on the ground plane. Such orthogonal structure easily achieves good diversity performance. To enhance isolation of the lower band, a fork-shaped slot is notched on the ground between two radiators, and the mutual coupling reduces to −20 dB below for the entire UWB frequency band. By slitting open-ended quarter-wavelength L slots on the radiator elements, the rejection bands are achieved. The compact size of the antenna is only 30 × 30 mm2, and the antenna prototype is fabricated and measured. Measured results indicate that a wide-impedance bandwidth, which is from 2.85 to 11.9 GHz with rejection band of 5.1–6 GHz, is achieved, and the envelope correlation coefficient is below 0.008, which are competitive for portable UWB devices.

Miniaturized decoupled slotted patch RFID tag antennas for wearable health care

In this article, a couple of two-layered RFID tag antenna designs exhibiting improved performance descriptors for on-body applications are presented. The antennas are designed to operate in the microwave band (2.4–2.48 GHz) ensuring high data transmission rates ideal for real-time subject monitoring applications. The radiating element of both the antennas is a slotted patch structure provisioned with a pair of T-shaped slots realized on a commercial FR4 substrate. The augmentation of a systematic sequence of narrow comb-like etchings into the design enhances the impedance bandwidth considerably. A high permittivity silicon layer embedded with the radiating patch provides resilience from the human body dielectric losses. A modified antenna design utilizing patch miniaturization technique, resulting in an overall footprint reduction by 32%, is also proposed. The designed tag antennas offer a gain of more than 1.8 dBi and an attractive read range greater than 6.8 m in the operating band.

A Multiband Multiple-input Multiple-output Antenna System for Long Term Evolution and Wireless Local Area Networks Handsets

A novel multiband multiple-input-multiple-output (MIMO) antenna system is proposed. The MIMO antenna system consists of two antenna elements, each of which comprises of three radiators: a driven monopole, an S-shaped strip and an inverted F-shaped strip and occupies footprint of 15x18.5x0.8 mm3 only. The driven monopole acts as a quarter-wave monopole and stimulate higher mode resonance. The two strips are excited by electromagnetic coupling from the driven monopole and serve as two additional monopoles leading to a wideband performance for the lower band. The bandwidths (VSWR ≤ 2.75) achieved for the antenna element are 1.67 – 2.2 GHz for the lower band and 2.28 –2.95 GHz for the upper band which cover LTE-1, LTE- 2, LTE- 3, LTE- 7, LTE- 40 and WLAN 2.4 GHz bands. A T-shaped slot and another two slots are introduced to reduce the coupling effect between the two multiband antenna elements. The isolation achieved is higher than 18 dB over the whole band, leading to an envelope correlation coefficient of less than 0.01. Furthermore, the diversity characteristics of mean effective gains (MEGs) and diversity gain (DG) are also studied. Both the simulated and measured results are shown to illustrate the performance of the proposed multiband MIMO antenna system, and that confirms the suitability for LTE and WLAN handset applications.

Very-low-profile hybrid open-slot/closed-slot/inverted-F antenna for the LTE smartphone

A very-low-profile hybrid antenna for the LTE smartphone was presented. The antenna structure was mainly formed by a T-shaped open slot disposed on the main circuit board inside the smartphone casing and a metallic patch printed on the inner surface of the frame around the smartphone casing. The antenna with the T-shape open slot and the on-frame metallic patch had a very low profile of 3 mm. By using two feeds (low-band and high-band feeds) across the two arms of the T-shape open slot and connected to the on-frame metallic patch, hybrid resonant modes including the open-slot antenna (OSA) mode, the closed-slot antenna (CSA) mode, and the inverted-F antenna (IFA) mode could be generated to form two operating bands for the LTE operation. The low band could cover the 824–960 MHz band for the LTE band 5 and 8 operation. The high band can cover the 1710–2690 MHz band for the LTE band 10, 15, and 16 operation. The techniques on exciting the hybrid resonant modes with good impedance matching for the proposed very-low-profile antenna were addressed in this study. Experimental data of the fabricated antenna were also presented to verify the simulation results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1572–1577, 2016

An asymmetric coplanar strip-fed 7-shaped monopole antenna for miniaturized communication systems

A compact asymmetric coplanar strip (ACS)-fed monopole antenna for miniaturized communication systems is proposed. It consists of an ACS-fed 7-shaped monopole, a partial ground plane, and an FR4 substrate. The proposed antenna occupies a very compact size of only 30 × 13 mm2 which accords with the development trend toward miniaturized electronic components. The 7-shaped monopole can be considered as a combination of three parts—a rectangular strip on the top, a trapezoidal strip in the center, and a straight microstrip feed line at the bottom—which generates two separate resonant frequency bands. By introducing an open-ended T-shaped slot in the rectangular strip, a new resonant mode can be excited. Detailed descriptions of the design evolution as well as the parametric study are given to better understand the mechanisms of the proposed antenna. Experimental results demonstrate that it can provide a triple-band frequency range compatible with the 2.4/5.2/5.8 GHz WLAN (2.4–2.485, 5.15–5.35, and 5.725–5.825 GHz) and 3.5/5.5 GHz WiMAX (3.4–3.7 and 5.25–5.85 GHz) operating bands. Furthermore, stable radiation patterns with satisfactory gains make it a good candidate as an internal antenna for compact multiband communication systems. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1566–1572, 2016

Ultra-Wideband Antenna’s Design Techniques

The main objective of this paper is to understand the different methodologies which have been adopted in the recent years in design of Ultra-Wideband Antenna. Methods/Statistical analysis: The patch of the UWB antenna is etched with circular rings to obtain wider bandwidth. Rabbet structured patch can also be utilized for enhancing bandwidth. Ground plane of UWB antenna’s in some cases is parabolic and some have T or L-shape slots to enhance antenna characteristics like increasing bandwidth, band notching at certain frequencies etc. dielectric substrate FR4 is preferred in most of the UWB antenna designs due to less return loss and better bandwidth utilization. Findings: With help of circular patch, more than 160% of Bandwidth is attainable. Use of triangular slots in ground plane can help increase the bandwidth by 45%. A further alteration in ground plane such as grooved ground plane can help minimize the surface waves. Application/Improvements: Since T-shaped slots increases directivity so they are preferred in air-bore applications. L-shaped slots in ground plane helps in RADAR applications.

Novel Antenna Structure for Early Breast Cancer Detection

Low cost miniaturized efficient ultra-wideband (UWB) antenna dedicated to a non-invasive technique for early breast cancer detection is studied mathematically, designed, simulated, fabricated and tested. The new design is composed of a small sized square patch (26mm x 20mm), with three rectangular slots and a reduced ground-plane which has a T-shaped slot, fed by a 50Ω microstrip transmission line. Also, a comparative study has been made with some recent works to prove the potential of this structure. The frequency bandwidth of this antenna is 13.27GHz. In this range of operation, such a device is suited for various Ultra wideband applications.

Triple-Band MIMO Antenna for Mobile Wireless Applications

This letter presents a planar triple-band multiple- input-multiple-output (MIMO) antenna that meets GSM900/1800 and LTE2600 bands protocols. The antenna element contains three individual meander-line-type inverted-L radiators; the highest frequency band radiator is fed by a transmission line, while the other two utilize the proximity-coupling feeding mechanism driven by the highest band radiator. The MIMO antenna is incorporated with two symmetric triple-band antenna elements and two physical decoupling devices. The two antenna elements are closely spaced with 1/15 wavelength of the lowest band. The two decoupling devices, a T-shaped slot and a meandering microstrip-line resonator, are built for the highest and the lowest frequency bands, respectively. Meanwhile, a negligible mutual coupling effect in middle band is achieved by using a collinear-placed transverse meander-line pair in the MIMO antenna. The antenna prototype measurement results show good impedance matching with low mutual coupling effect. The calculated envelope correlation coefficient verifies the suitability of the proposed antenna for mobile wireless access applications.

High gain L-T slots-loaded dual-band elliptical polarized antenna

In this letter, L-T slots-loaded dual-band elliptical polarized antenna etched on a single layer substrate is proposed. This antenna is composed from four T-shaped slots near patch boundary and two pair of L-shaped slots etched at patch corner with a rectangular slot located at the center. These combination slots are found out to produce two different frequency bands for LTE and wireless local area network application. The lower band of 2.5–2.69 GHz and the upper band of 5.725–5.85 GHz are controlled by the T-shaped slots and L-shaped slots, respectively. By symmetrically slots and properly positioning the feed position, the proposed antenna exhibits high gain of 6.91 dBi and 7.22 dBi at 2.6 GHz and 5.8 GHz, respectively, even with the compact dimensions of 44 × 44 × 1.6 mm3. Due to the orthogonal surface currents at first and third resonant modes, the proposed antenna gives an elliptical polarization with axial ratios of 7.536 dB at 2.656 GHz and 5.76 dB at 5.8 GHz. The simulation and measurement results of reflection coefficient, gain, and radiation pattern are comparable. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:184–188, 2016

Wideband circularly polarized planar monopole antenna for wireless communication applications

A wideband circular polarization (CP) printed monopole antenna with coplanar-waveguide (CPW)-fed is presented for wireless communication applications. By employing T-shaped slot in the ground-plane, the impedance bandwidth of the antenna is enlarged, and its wide axial-ratio (AR) bandwidth is realized. The measured results show a −10 dB impedance bandwidth of 75.39% (3.62-8.00 GHz) and an axial ratio (AR) bandwidth of 31.38% (4.81-6.60 GHz), which agree well with the simulated results. The proposed antenna can provide a peak antenna gain of about 1.68 dBi at 5.00 GHz, with gain variations less than 0.81 dB for frequencies within the CP bandwidth.