Showing papers on "Slot antenna published in 2019"
TL;DR: A novel balanced open-slot antenna is designed as an array antenna element, in which this antenna design can yield a balanced slot mode that can enhance the isolation between two adjacent input ports and further mitigates the coupling between antenna elements.
Abstract: A high-isolation eight-antenna multi-input multi-output (MIMO) array operating in the 3.5 GHz band (3.4–3.6 GHz) for future smartphones is proposed. Here, a novel balanced open-slot antenna is designed as an array antenna element, in which this antenna design can yield a balanced slot mode (with reduced ground effects) that can enhance the isolation between two adjacent input ports. Furthermore, by meticulously arranging the positions of the eight antenna elements, desirable polarization diversity can also be successfully achieved, which further mitigates the coupling between antenna elements. A prototype was manufactured to validate the simulation. A good impedance matching (return loss > 10 dB), high isolation (>17.5 dB), high total efficiency (>62%), and low envelope correlation coefficient (ECC, <0.05) were measured across the desired operation bandwidth. To verify the MIMO performance, ergodic channel capacity using the Kronecker channel model was calculated. The effects of hand phantom were also studied.
201 citations
TL;DR: The proposed MIMO antenna offers good S-parameters, high-gain radiation patterns, and sufficient total efficiencies, even though it is arranged on a high-loss FR-4 dielectric.
Abstract: In this paper, we propose an eight-port/four-resonator slot antenna array with a dual-polarized function for multiple-input-multiple-output (MIMO) 5G mobile terminals. The design is composed of four dual-polarized square-ring slot radiators fed by pairs of microstrip-line structures. The radiation elements are designed to operate at 3.6 GHz and are located on the corners of the smartphone PCB. The square-ring slot radiators provide good dual-polarization characteristic with similar performances in terms of fundamental radiation characteristics. In order to improve the isolation and also reduce the mutual coupling characteristic between the adjunct microstrip-line feeding ports of the dual-polarized radiators, a pair of circular-ring/open-ended parasitic structures is embedded across each square-ring slot radiator. The −10-dB impedance bandwidth of each antenna-element is 3.4–3.8 GHz. However, for −6-dB impedance bandwidth, this value is 600 MHz (3.3–3.9 GHz). The proposed MIMO antenna offers good S-parameters, high-gain radiation patterns, and sufficient total efficiencies, even though it is arranged on a high-loss FR-4 dielectric. The SAR function and the radiation characteristics of the proposed design in the vicinity of user-hand/user-head are studied. A prototype of the proposed smartphone antenna is fabricated, and good measurements are provided. The antenna provides good features with a potential application for use in the 5G mobile terminals.
156 citations
TL;DR: Due to the advantages such as multiband operation, MIMO configuration for 5G communications, high isolation, and compact structure, the proposed antenna design is attractive for 4G/5G smartphones.
Abstract: In this paper, multiband antennas based on a single ring slot are proposed for 4G/5G smartphone applications. The basic structure of the antenna is consisted of a large metal ground and an unbroken metal rim, in which a single 2 mm-wide ring slots is realized between the metal ground and rim. Here, a reconfigurable 4G antenna (820–960 and 1710–2690 MHz) is initially devised by loading multiple grounded stubs and a simple dc controlling circuit with varactor diode into the upper section of the ring slot. To further cover the sub-6 GHz spectrum (3400–3600 MHz) for future 5G communications, a four-element multi-input multi-output (MIMO) slot antennas configuration is designed by utilizing the lower section of the ring slot. A prototype antenna was fabricated, and good agreement is shown between the measured and simulated results. Due to the advantages such as multiband operation, MIMO configuration for 5G communications, high isolation, and compact structure, the proposed antenna design is attractive for 4G/5G smartphones.
120 citations
TL;DR: A new, portable, and low-cost microwave imaging (MWI) system using an iterative enhancing technique for breast imaging that has been able to perform the detection of tumorous cells in breast phantom that can pave the way to saving lives.
Abstract: Globally, breast cancer is a major reason for female mortality. Due to the limitations of current clinical imaging, the researchers are encouraged to explore alternative and complementary tools to available techniques to detect the breast tumor in an earlier stage. This article outlines a new, portable, and low-cost microwave imaging (MWI) system using an iterative enhancing technique for breast imaging. A compact side slotted tapered slot antenna is designed for microwave imaging. The radiating fins of tapered slot antenna are modified by etching nine rectangular side slots. The irregular slots on the radiating fins enhance the electrical length as well as produce strong directive radiation due to the suppression of induced surface currents that radiate vertically at the outer edges of the radiating arms with end-fire direction. It has remarkable effects on efficiency and gain. With the addition of slots, the side-lobe levels are reduced, the gain of the main-lobe is increased and corrects the squint effects simultaneously, thus improving the characteristics of the radiation. For experimental validation, a heterogeneous breast phantom was developed that contains dielectric properties identical to real breast tissues with the inclusion of tumors. An alternative PC controlled and microcontroller-based mechanical MWI system is designed and developed to collect the antenna scattering signal. The radiated backscattered signals from the targeted area of the human body are analyzed to reveal the changes in dielectric properties in tissues. The dielectric constants of tumorous cells are higher than that of normal tissues due to their higher water content. The remarkable deviation of the scattered field is processed by using newly proposed Iteratively Corrected Delay and Sum (IC-DAS) algorithm and the reconstruction of the image of the phantom interior is done. The developed UWB (Ultra-Wideband) antenna based MWI has been able to perform the detection of tumorous cells in breast phantom that can pave the way to saving lives.
111 citations
TL;DR: In this article, a dual-function slot antenna at microwave and millimeter-wave (mm-wave) band is proposed, which consists of a slot printed on the edge of the structure ground plane.
Abstract: A dual-function slot antenna at microwave and millimeter-wave (mm-wave) band is proposed. The design consists of a slot printed on the edge of the structure ground plane. A short-circuited varactor diode (VAR) is used to achieve the frequency tunability from 2.05 to 2.7 GHz (4G, WLAN) with a maximum realized gain of 4.5 dBi. For mm-waveband, the slot works as a connected slot antenna array (CSAA) by using eight periodic feeders with a wide bandwidth of 23–29 GHz (5G) and a maximum realized gain of 12.5 dBi. To enhance the functionality, two slots are orthogonally arranged for multiple-input multiple-output (MIMO) application. The whole structure is implemented using Rogers 5880 substrate with a board size of $70\times 60\times 0.381$ mm3. The envelope correlation coefficient (ECC) and isolation are calculated, showing satisfactory MIMO characteristics. The minimum ECC value is 0.01, while the isolation is more than 20 dB among different feeding ports. Due to the integration of 4G and 5G operations into a single narrow slot, the proposed antenna system is compact, simple, and planar in structure and, thus, attractive for future mobile handheld devices.
93 citations
TL;DR: In this article, a dual-band substrate-integrated waveguide (SIW) antenna array topology is proposed for operation in the 28 and 38 GHz frequency bands, where four miniaturized quartermode SIW cavities are tightly coupled, causing mode bifurcation, and yielding an antenna topology with four distinct resonance frequencies.
Abstract: A novel dual-band substrate-integrated waveguide (SIW) antenna array topology is proposed for operation in the 28 and 38 GHz frequency bands. Four miniaturized quarter-mode SIW cavities are tightly coupled, causing mode bifurcation, and yielding an antenna topology with four distinct resonance frequencies. A pair of resonances is assigned to both the 28 and 38 GHz band, achieving wideband operation in both frequency ranges. Moreover, owing to the exploited miniaturization technique, an extremely compact array topology is obtained, facilitating easy and straightforward integration. The computer-aided design process yields a four-element antenna array that entirely covers the 28 GHz band (27.5–29.5 GHz) and 38 GHz band (37.0–38.6 GHz) with a measured impedance bandwidth of 3.65 and 2.19 GHz, respectively. A measured broadside gain of 10.1 dBi, a radiation efficiency of 75.75% and a 3 dB beamwidth of 25° are achieved in the 28 GHz band. Moreover, in the 38 GHz band, the measured broadside gain amounts to 10.2 dBi, a radiation efficiency of 70.65% is achieved, and the 3 dB beamwidth is 20°.
80 citations
TL;DR: A systematic design of high performance eight element antenna array for a 5G mobile terminal operating at 2.6/3.5 GHz bands and can be easily implemented for the future smartphones as it utilizes the conductive sheet or chassis and the middle vertically mounted antenna do not use the additional space of the chassis or ground.
Abstract: This work presents a systematic design of high performance eight element antenna array for a 5G mobile terminal operating at 2.6/3.5 GHz bands. The proposed eight element slot antenna array based on unit monopole slot antenna embedded in the metal casing or ground resonates at fundamental mode at 2.6 GHz. The antenna array is developed from four antennas (open-end slot antenna) etched near to the corner edges of the printed circuited board with supported pairs of vertically mounted slot antennas in middle section of the long edge ground plane. This combination of the antenna elements provided pattern diversity and enabled the smartphone in the reception of the signal in a different direction. The impedance bandwidth based on -10 dB return loss criteria cover from 2.4 GHz to 3.6 GHz includes the two allocated bands of (2400 MHz to 2600 MHz) and (3400 MHz to 3600 MHz) for 5G cellular communication systems. The vital MIMO performance measures as envelope correlation coefficient or ECC is less than 0.2 for any two antenna array meeting the required standard of less than 0.5 alongside the mean effective gain or MEG ratio of any two antenna meeting the required standard of less than 3 dB for power balance and optimal diversity performance. As modern smartphone demand desires slim handsets, the after mentioned compact multiple antenna structure can be easily implemented for the future smartphones as it utilizes the conductive sheet or chassis and the middle vertically mounted antenna do not use the additional space of the chassis or ground. The customer hand or human hand effect on the multiple antenna array to mimic the use of mobile phone customer is also studied. The maximum MIMO Channel capacity based on measured result is 34.25bps/Hz and is about 3 times of 2 × 2 MIMO operations.
78 citations
TL;DR: In this article, a broadband mm-wave multiple-input-multiple-output (MIMO) antenna system for upcoming 5G networks is presented, where an electromagnetic band-gap (EBG) reflector is placed behind the antenna structure toward the feeding network to decrease the backward radiation and improve the front-to-back (F/B) ratio.
Abstract: In this work, a broadband millimeter-wave (mm-wave) multiple-input–multiple-output (MIMO) antenna system for upcoming fifth generation (5G) networks is presented. The MIMO antenna system is two ports and realized using two antenna arrays, aligned in opposite directions. Each array consist of three elements in each, as each element is a simple recognized printed wide-slot antenna proximity excited by microstrip line with a widened tuning stub; manipulated for operating in the Ka-band, which includes the 28 and 38 GHz bands, as potential candidates for 5G communications. An electromagnetic band-gap (EBG) reflector is placed behind the antenna structure toward the feeding network to decrease the backward radiation and improve the front-to-back (F/B) ratio. Results show that the proposed MIMO antenna system with EBG reflector provides wideband impedance bandwidth >27 GHz (from 22.5 to >50 GHz) and good radiation characteristics with a total realized gain up to 11.5 and 10.9 dBi at the two frequencies of interest, respectively. The envelope correlation coefficient (ECC) and diversity gain (DG) were evaluated and showed good MIMO performance. These remarkable features with the benefits of design simplicity and easily expansion to large-scale antenna system make the proposed design suitable for mm-wave communications.
73 citations
TL;DR: In this paper, a dual-band four-element monopole MIMO antenna system is presented for future wireless devices operating at WLAN (2.45 GHz, 5.2 GHz), 4G LTE (2,6 GHz) and 5G (24 GHz, 28 GHz) bands.
Abstract: A single-layered multiple-input multiple-output (MIMO) antenna system is presented for future wireless devices operating at WLAN (2.45 GHz, 5.2 GHz), 4G LTE (2.6 GHz) and 5G (24 GHz, 28 GHz) bands. The design consists of a dual-band four-element monopole MIMO antenna system that covers the 2.45 GHz and 5.2 GHz bands. A decoupling mechanism is designed in the ground plane based on a tapered slot. This tapered slot has a dual function, working both as a decoupling structure ( $\lambda _{0}/4$ long) at 2.45 GHz and as a tapered slot antenna ( $3\lambda _{0}$ long) at 28 GHz when excited by a proper feeder. The proposed MIMO antenna system is designed on an RO-5880 substrate with overall dimensions of $104$ mm $\times 104$ mm $\times 0.51$ mm. The measured results show that the presented design covers two low-frequency bands (from 2.40 GHz to 5.1 GHz, from 5.1 GHz to 5.6 GHz) with a peak gain of 5 dBi and one high-frequency band (from 23 GHz to 30 GHz) with a peak gain of 11 dBi. The minimum measured isolation between the two antennas is more than 16 dB, while the maximum envelope correlation coefficient value is less than 0.16 showing good MIMO characteristics.
67 citations
TL;DR: A multiple-input multiple-output (MIMO) antenna system is proposed for fifth generation (5G) and fourth generation (4G) mobile communication that meets all of the requirements of both 5G and 4G antennas using only a single structure.
Abstract: A multiple-input multiple-output (MIMO) antenna system is proposed for fifth generation (5G) and fourth generation (4G) mobile communication. The design meets all of the requirements of both 5G and 4G antennas using only a single structure. Since 5G will work at millimeter-wave (mm-Wave), the proposed design serves triple bands at mm-Wave (28, 37 and 39 GHz) for 5G in addition to 2 GHz band (1.8–2.6) for 4G. Each MIMO element consists of a slot-based antenna, fed by two microstrip feeders for the 5G and 4G bands. The design works as a tapered slot antenna at mm-Wave offering end-fire radiation for 5G and works as an open-ended slot antenna for a 2 GHz band offering omni-direction radiation for 4G. The slot antenna type used in the proposed design produces wide bandwidths for the 5G and 4G. The overall volume of each MIMO antenna element is $0.21\times 0.10 \times 0.003\,\,\lambda ^{3}$ , where $\lambda $ is the wavelength of the lowest operating frequency. As a proof of concept, a prototype is developed and tested. The measured results show a wide impedance bandwidth of $|S_{11}| −10 dB covering the band 27.5–40 GHz for 5G, and impedance bandwidth of $|S_{11}| −6 dB covering the band 1.8–2.6 GHz for 4G.
66 citations
TL;DR: A novel diplexer-based fully passive transponder, with enhanced bandwidth and gain performance, is presented in this paper, which targets sub-6-GHz 5G-compatible internet-of-things applications.
Abstract: A novel diplexer-based fully passive transponder is presented in this paper, which targets sub-6-GHz 5G-compatible internet-of-things applications. To alleviate the antenna design restrictions of traditional transponder with two separate antennas, a new architecture has been proposed with the introduction of a diplexer, which allows transponder to simply employ a dual-band antenna. In this paper, a dual-band circularly polarized omnidirectional spiral slot antenna, with enhanced bandwidth and gain performance, is designed as the transponder Tx/Rx antenna. Besides the new architecture, a diode selection criterion is proposed as well. Analytical models are derived, showing relationships between the diode’s SPICE parameters and the conversion efficiency or conversion loss (CL) of such diode-based transponders. With help of the analysis, transponder designers can easily identify diodes to implement transponders with better performance. Under the guidance of the criterion, low-barrier diode SMS7630 is chosen for verification. Measured CL results of the transponder circuitry part show a noticeable improvement over the state-of-the-art works. The complete prototype was tested with radar’s transmitting power of 25 dBm, and it presents a maximum read-out distance up to 7 m when the operating fundamental frequency is 3.5 GHz.
TL;DR: The measured results confirm that the proposed MIMO array is a good candidate for 5G terminals and exhibits good isolation without any external decoupling structure.
Abstract: In this paper, a compact building block composed of a slot antenna and a loop antenna is proposed. The slot antenna and the loop antenna share a rectangular clearance, which improves the compactness of the building block effectively. Although the slot and the loop have overlapped completely, the proposed building block exhibits good isolation (better than 19 dB) without any external decoupling structure. Four such building blocks are used to implement a compact eight-port multiple-input multiple-output (MIMO) array operating at 3.5 GHz band (3.4–3.6 GHz) for fifth-generation (5G) metal-rimmed smartphone applications. The proposed eight-antenna MIMO array exhibits good isolation of better than 16 dB across the whole operating band. The measured efficiencies of the proposed MIMO array were between 59% and 73%, and its corresponding measured envelope correlation coefficients (ECCs) were better than 0.05. Furthermore, the calculated channel capacity of the proposed MIMO array with 20 dB signal-to-noise ratio (SNR) was about 38.2–39.8 bps/Hz across the desired bands (3.4–3.6 GHz). The measured results confirm that the proposed MIMO array is a good candidate for 5G terminals.
TL;DR: In this paper, a cavity-backed modified dumbbell-shaped slot antenna based on a substrate integrated waveguide technology is proposed, which not only introduces several new resonant points, but also makes the antenna obtain a higher gain.
Abstract: A cavity-backed modified dumbbell-shaped slot antenna based on a substrate integrated waveguide technology is proposed in this letter. Compared with the traditional dumbbell-shaped slot, the modified dumbbell-shaped slot not only introduces several new resonant points, but also makes the antenna obtain a higher gain. In addition, the high-order resonant modes (TE102, TE301, TE302) inside the subcavity are excited by the ground coplanar waveguide feeding structure, and the broadband impedance bandwidth can be achieved by making the high-order modes close to each other. The measured results show that the proposed antenna achieves an impedance bandwidth of 26.7% from 18.2 to 23.8 GHz and a peak gain of 9.5 dBi at 20.4 GHz. The cross-polarization levels of the antenna are around –40 dB at three measured frequencies.
TL;DR: In this paper, the authors proposed a multiple antenna system for 5G smartphones operating at 3.5 GHz for multiple-input multiple-output (MIMO) operation in smartphones, which adopted the unit open-end slot antenna fed by Inverted-L microstrip with tuning stub.
Abstract: In this paper, the systematic design of a multiple antenna system for 5G smartphone operating at 3.5 GHz for multiple-input multiple-output (MIMO) operation in smartphones is proposed. The smartphone is preferred to be lightweight, thin, and attractive, and as a result metal casings have become popular. Using conventional antennas, such as a patch antenna, Inverted-F antennas, or monopole, in proximity to metal casing leads to decreasing its total efficiency and bandwidth. Therefore, a slot antenna embedded in the metal casing can be helpful, with good performance regarding bandwidth and total efficiency. The proposed multiple antenna system adopted the unit open-end slot antenna fed by Inverted-L microstrip with tuning stub. The measured S-parameters results agree fairly with the numerical results. It attains 200 MHz bandwidth at 3.5 GHz with ports isolation of (≤−13 dB) for any two antennas of the system. The influence of the customer’s hand for the proposed multiple antenna system is also considered, and the MIMO channel capacity is computed. The maximum achievable MIMO channel capacity based on the measured result is 31.25 bps/Hz and is about 2.7 times of 2 × 2 MIMO operation.
TL;DR: The proposed multiple-input multiple-output (MIMO) antenna is designed to meet the requirements of 4G and 5G mobile terminals with essential bandwidth for higher data rate applications and provides good properties including S-parameters, efficiency, and radiation pattern coverage.
Abstract: In this study, we propose a design of a multi-band slot antenna array applicable for fourth-generation (4G) and fifth-generation (5G) smartphones. The design is composed of double-element square-ring slot radiators fed by microstrip-line structures for easy integration with radio frequency (RF)/microwave circuitry. The slot radiators are located on the corners of the smartphone printed circuit board (PCB) with an overall dimension of 75 × 150 mm2. The proposed multiple-input multiple-output (MIMO) antenna is designed to meet the requirements of 4G and 5G mobile terminals with essential bandwidth for higher data rate applications. For −10 dB impedance bandwidth, each single-element of the proposed MIMO design can cover the frequency ranges of 2.5–2.7 GHz (long-term evolution (LTE) 2600), 3.45–3.8 GHz (LTE bands 42/43), and 5.00–5.45 GHz (LTE band 46). However, for −6 dB impedance bandwidth, the radiation elements cover the frequency ranges of 2.45–2.82 GHz, 3.35–4.00 GHz, and 4.93–5.73 GHz. By employing the microstrip feed lines at the four different sides of smartphone PCB, the isolation of the radiators has been enhanced and shows better than 17 dB isolation levels over all operational bands. The MIMO antenna is implemented on an FR-4 dielectric and provides good properties including S-parameters, efficiency, and radiation pattern coverage. The performance of the antenna is validated by measurements of the prototype. The simulation results for user-hand/user-head impacts and specific absorption rate (SAR) levels of the antenna are discussed, and good results are achieved. In addition, the antenna elements have the potential to be used as 8-element/dual-polarized resonators.
TL;DR: In this paper, a design of mobile-phone antenna array with diamond-ring slot elements for 5G massive MIMO systems is proposed, where the antenna elements are fed by 50-Ohm L-shaped microstrip-lines.
Abstract: A design of mobile-phone antenna array with diamond-ring slot elements is proposed for fifth generation (5G) massive multiple-input/multiple-output (MIMO) systems. The configuration of the design consists of four double-fed diamond-ring slot antenna elements placed at different corners of the mobile-phone printed circuit board (PCB). A low-cost FR-4 dielectric with an overall dimension of 75 × 150 mm2 is used as the design substrate. The antenna elements are fed by 50-Ohm L-shaped microstrip-lines. Due to the orthogonal placement of microstrip feed lines, the diamond-ring slot elements can exhibit the polarization and radiation pattern diversity characteristic. A good impedance bandwidth (S11 ≤ −10 dB) of 3.2–4 GHz has been achieved for each antenna radiator. However, for S11 ≤ −6 dB, this value is 3–4.2 GHz. The proposed design provides the required radiation coverage of 5G smartphones. The performance of the proposed MIMO antenna design is examined using both simulation and experiment. High isolation, high efficiency and sufficient gain-level characteristics have been obtained for the proposed MIMO smartphone antenna. In addition, the calculated total active reflection coefficient (TARC) and envelope correlation coefficient (ECC) of the antenna elements are very low over the whole band of interest which verify the capability of the proposed multi-antenna systems for massive MIMO and diversity applications. Furthermore, the properties of the design in Data-mode/Talk-mode are investigated and presented.
TL;DR: In this article, an innovative beam-scanning leaky-wave antenna (LWA) is proposed, which enables scanning over a wide angle from - 35° to + 34.5° between 57 and 62 GHz, with broadside radiation centred at 60 GHz.
Abstract: This paper presents empirical results of an innovative beam-scanning leaky-wave antenna (LWA), which enables scanning over a wide angle from - 35° to + 34.5° between 57 and 62 GHz, with broadside radiation centred at 60 GHz. The proposed LWA design is based on composite right/left-handed transmission-line (CRLH-TL) concept. The single-layer antenna structure includes a matrix of 3 × 9 square slots that is printed on top of the dielectric substrate; and printed on the bottom ground-plane are Π- and T-shaped slots that enhance the impedance bandwidth and radiation properties of the antenna. The proposed antenna structure exhibits metamaterial property. The slot matrix provides beam scanning as a function of frequency. Physical and electrical size of the antenna is 18.7 × 6 × 1.6 mm
3
and 3.43λ
0
× 1.1λ
0
× 0.29λ
0
, respectively, where λ
0
is free space wavelength at 55 GHz. The antenna has a measured impedance bandwidth of 10 GHz (55-65 GHz) or fractional bandwidth of 16.7%. Its optimum gain and efficiency are 7.8 dBi and 84.2% at 62 GHz.
TL;DR: A flexible antenna with a simple structure, small size, and light weight for medical wearable applications is proposed, which can cover the whole ISM 5.8GHz band and perform good wearable radiation characteristics.
Abstract: In this paper, a flexible antenna with a simple structure, small size (15mm×17mm×1mm), and light weight for medical wearable applications is proposed. The antenna consists of slot radiation elements fed by a coplanar waveguide structure and a floating ground. Flexible conductive cloth MKKTN260 is used to fabricate the antenna, while felt with good insulation is used as the substrate. The measured impedance matching bandwidth (|S
11
|less than -10dB) of the antenna is from 5.578 to 5.898GHz, which can cover the whole ISM 5.8GHz band (5.725-5.825GHz) and perform good wearable radiation characteristics. The floating ground structure and the interaction between slots make the antenna radiated efficiently (the measured peak realized gain is 4.85dBi at 5.8GHz) to the +Z direction, which is away from the human body. Meanwhile, without any specially designed reflecting structures, the specific absorption rate value is below the criterion set by the FCC and ICNIPR. The bending configurations are also studied for this antenna.
TL;DR: In this article, a dual-band circularly polarized slot antenna with p-i-n diodes is presented. But the antenna can be switched electronically between left-hand and right-hand circular polarization.
Abstract: This letter presents a novel dual-band circularly polarized slot antenna. The far-field polarization of the antenna can be switched electronically between left-hand circular polarization and right-hand circular polarization. A 50 Ω microstrip feed line is divided into four arms those excite a ground plane slot. The p-i-n diodes are introduced in the arms for polarization switching. A prototype dual-band dual-sense antenna with f 01 = 2.4 GHz and f 02 = 5.2 GHz is fabricated using a 1.6 mm thick FR4 substrate. The measured 3 dB axial ratio bandwidths are more than 16.6% and 5.7% at the lower and upper bands, respectively. The measured return loss is more than 10 dB over the wireless local area network (LAN) bands.
TL;DR: In this paper, a new wideband and enhanced gain Fabry-Perot cavity antenna is presented, which consists of printed and etched square rings on both sides of the superstrate.
Abstract: A new wideband and enhanced gain Fabry–Perot cavity antenna is presented in this letter. The Fabry–Perot cavity is established between a single-layer metamaterial-based partially reflective surface (PRS) and a simple feeding slot antenna. The unit cell of the PRS consists of printed and etched square rings on both sides of the superstrate. A 6 × 6 array of the unit cells is optimized to produce a positive reflection phase gradient required for the gain enhancement. Simulated results of the designed Ku-band antenna demonstrate an impedance bandwidth of 13.1–15.3 GHz (15.5%) with a gain enhancement up to 8.2 dB (i.e., 150% gain increase above the feeding antenna) and a 3 dB radiation bandwidth of 18.7%. Experimentally observed reflection and radiation responses of the fabricated prototype validate the simulated results.
TL;DR: In this article, a low profile differentially fed dual-polarized slot antenna is proposed for base station application, its radiator is an octagon patch etched with two normal H-shaped slots.
Abstract: In this letter, a low-profile differentially fed dual-polarized slot antenna is proposed for base station application. Its radiator is an octagon patch etched with two normal H-shaped slots. The folded feeding line is introduced to accommodate the differentially fed scheme and tune impedance matching. Both high isolation and stable radiation patterns are realized by using the differential feeding technique. Measured results demonstrate that the impedance bandwidths (VSWR < 1.5) of the two polarizations are 19.3% (3.14–3.81 GHz) and 20.3% (3.10–3.80 GHz), respectively. The proposed antenna has a high isolation of larger than 43 dB over the entire operation band. The measured gain is higher than 8.1 dBi within the operating frequency.
TL;DR: In this paper, a cavity-backed slot antenna is proposed using substrate-integrated waveguide (SIW) technology for Wi-Fi/Industrial, Scientific, and Medical Radio band applications.
Abstract: In this communication, a cavity-backed slot antenna is proposed using substrate-integrated waveguide (SIW) technology for Wi-Fi/Industrial, Scientific, and Medical Radio band applications. This antenna comprises two SIW cavities, a rectangular and circular with a circular ring slot on the top of each cavity for radiation. The circular cavity is designed such that it is nested inside the rectangular cavity, and each one is excited by separate feedlines (microstrip and coaxial probe). By properly optimizing the antenna dimensions, it produces two frequency bands at 5.2 and 5.8 GHz with a small frequency ratio of 1.12. Finally, the design is fabricated and the results are experimentally verified. The experimental results show that the proposed antenna exhibits a −10 dB impedance bandwidth of 6% (5.04–5.35 GHz) in the lower frequency band and 3.4% (5.73–5.92 GHz) in the higher frequency band with maintaining the input port isolation better than 28 dB. Due to the SIW cavity-backing structure, the antenna shows unidirectional radiation patterns at both resonant frequencies of 5.2 and 5.8 GHz with the gain of 6.97 and 6.2 dBi, respectively. Moreover, the antenna possesses the advantages of lightweight, planar configuration, and ease of fabrication.
TL;DR: Novel methods of improving directivity and decreasing sidelobe radiation via the addition of an elliptical pseudoelement and irregularly spaced notches in the tapered slot antenna are presented in this paper.
Abstract: Novel methods of improving directivity and decreasing sidelobe radiation via the addition of an elliptical pseudoelement and irregularly spaced notches in the tapered slot antenna are presented in this paper. This antenna has been shown to be functional over the C, X, $\text{K}_{\mathrm {u}}$ , K, $\text{K}_{\mathrm {a}}$ , and portions of the $S$ - and $V$ -bands covering (2.5 to 57) GHz (22.8:1 bandwidth, defined where VSWR < 3). Minimum and maximum realized gains of 4 and 16 dB were achieved at 2.7 GHz and 29.8 GHz, respectively. The antenna offers directive radiation patterns with a half-power beamwidth under 40° for frequencies above 6 GHz and under 30° for frequencies above 32 GHz. As compared with other Vivaldi antennas reported in the past, the proposed design offers a larger bandwidth while providing higher peak gain and average gain. Good agreement was observed between simulation and measurements.
TL;DR: A groove-based wideband bow-tie slot antenna array is designed at 30 GHz based on printed ridge gap waveguide technology (PRGW), which achieves a high gain of 15.5 dBi and a radiation efficiency higher than 80% over the operating frequency bandwidth.
Abstract: The development of wireless and satellite communication has led to a demand for high-performance microwaves and mm-wave components in terms of cost, losses, and fabrication complexity. Gap waveguide is one of the emerging technologies in 5G and mm-wave applications due to their low cost, low losses, and high power handling capability. In this paper, a groove-based wideband bow-tie slot antenna array is designed at 30 GHz based on printed ridge gap waveguide technology (PRGW). A two-section T-shaped ridge is designed to feed a bow tie slot placed on the upper ground of the PRGW. The gain of the proposed slot antenna is enhanced by using a horn-like groove. Then, the proposed high gain element is deployed to build up a 1 bow-tie slot antenna array loaded with three-layer groove antenna. The proposed antenna array is fabricated and measured, where the measured results show a −10-dB impedance bandwidth from 29.5 to 37 GHz (22%). The fabricated prototype achieves a high gain of 15.5 dBi and a radiation efficiency higher than 80% over the operating frequency bandwidth.
TL;DR: The feasibility of detecting early-stage skin tumors in three dimensions is experimentally verified by employing the sub-band antennas in a synthetic ultra-wideband imaging system with a bandwidth of 98 GHz.
Abstract: This work introduces, for the first time, a millimeter-wave imaging system with a “synthetic” ultra-wide imaging bandwidth of 98 GHz to provide the ultra-high resolutions required for early-stage skin cancer detection. The proposed approach consists of splitting the required ultra-wide imaging bandwidth into four sub-bands, and assigning each sub-band to a separate imaging element, i.e., an antenna radiator. Each of the sub-band antennas transmits and receives signals only at its corresponding sub-band. The captured signals are then combined and processed to form the image of the target. For each sub-band, a Vivaldi tapered slot antenna fed with a combination of substrate-integrated waveguide and coplanar waveguide is designed and microfabricated. Design techniques are also provided for the four similarly-shaped sub-band antennas for achieving excellent impedance matches ( $S_{11}$ < –10 dB) and nearly constant gains of 10 dBi over the entire 12–110 GHz bandwidth. The design procedure is validated by comparing the simulated results with measurements performed on the fabricated prototypes. Excellent agreements are obtained between simulations and measurements. Finally, the feasibility of detecting early-stage skin tumors in three dimensions is experimentally verified by employing the sub-band antennas in a synthetic ultra-wideband imaging system with a bandwidth of 98 GHz. Two separate setups, each comprising a dispersive skin-mimicking phantom as well as two dispersive spherical tumors, are constructed for imaging experiments. Lateral and axial resolutions of 200 μm are confirmed, and a successful reconstruction of the spherical tumors is achieved in both cases.
TL;DR: In this paper, the authors presented a methodology to reduce mutual coupling in a planar slot antenna array by using electric metamaterials, which is based on resisting and steering the propagation of surface wave.
Abstract: In this communication, we present a methodology to reduce mutual coupling in a planar slot antenna array by using electric metamaterial. The proposed methodology is based on resisting and steering the propagation of surface wave. Initially, an array of complementary split-ring resonator (CSRR) is designed between the two slots for suppressing the surface wave propagation. Afterward, to steer the surface wave propagation, complementary fishnet structures are designed on the two sides of the slot array. Finally, for a better level of isolation improvement, both CSRR and complementary fishnet structures are simultaneously used. The final design has achieved at least 14 dB improvements in isolation level throughout the wide operating bandwidth of around 2 GHz, even if the gap between the slots is only 3.4 mm. The efficiency and the realized gain of the proposed antenna have also been studied. Because of the use of both metamaterial structures as a complementary, the overall configuration becomes fully planar and easy to realize.
TL;DR: In this article, a waveguide slot filtering antenna with an embedded metamaterial is presented, where the metasurface replaces the conventional metal plane in the form of a bed of nails.
Abstract: A novel waveguide slot filtering antenna with an embedded metamaterial is presented. This filtering antenna consists of a common waveguide slot antenna with longitudinal slots cut on the top broad wall of its rectangular waveguide and a metamaterial surface embedded in the bottom broad wall. The metasurface replaces the conventional metal plane in the form of a bed of nails. In the operating frequency band, the metasurface works as a perfect electric conductor, so the antenna radiates as the traditional waveguide slot antennas. While in the stopband, the metasurface performs as a perfect magnetic conductor to suppress the propagation of electromagnetic wave in the waveguide cavity, so the interference signal is rejected and a filter function is achieved. To show the design process and verify its feasibility, a filtering antenna prototype working in the $C$ -band and having a stopband in the $X$ -band is designed, fabricated, and tested. A good agreement between simulation and measurement is obtained, demonstrating efficient radiations in the working band and a strong suppression of more than 35 dB in the stopband.
TL;DR: This paper presents a fully digital beamforming receiver (FDBR) using a method that calibrates the signals of all chains in real time, and is targeted for 5G mobile communication.
Abstract: This paper presents a fully digital beamforming receiver (FDBR) using a method that calibrates the signals of all chains in real time, and is targeted for 5G mobile communication. In the real-time calibration method, the received signals of all chains are adjusted to correct the errors of phase and amplitude using the in-band signal other than operating frequency for calibration. The proposed FDBR with real-time calibration is designed and fabricated. The FDBR consists of eight chains of the tapered slot antenna (TSA) element, low noise block (LNB), and software defined radios (SDRs). The $1 \times 8$ array TSA with the directional coupler and the 1:8 divider is designed to send eight uniform calibration signals along with the received signal of all the chains. In SDR, the digital phase shifter and the real-time calibration blocks are implemented to realize digital beamforming. The digital phase shifter has an extremely high resolution of 0.72°. After using the real-time calibration method, the average of measured phase and amplitude error between each chain is less than 0.9° and 0.5 dB, respectively. To verify the beamforming performance of the FDBR, the simulation radiation pattern and the measurement radiation pattern are compared for 0°, ±15°, ±30°, and ±45° beam angles. The simulation results are in good agreement with the measured results. An excellent beamforming performance is achieved in the $1 \times 8$ array FDBR using the real-time calibration.
TL;DR: Two kinds of metasurface modulators for dynamically controlling the wavefront of terahertz (THz) radiation based on the temperature-induced insulator-to-metal phase transition of vanadium dioxide (VO2) are designed and fabricated.
Abstract: Active use of phase transition phenomena for reversibly tuning the properties of functional materials in devices currently is an attractive research area of materials science. We designed and fabricated two kinds of metasurface modulators for dynamically controlling the wavefront of terahertz (THz) radiation based on the temperature-induced insulator-to-metal phase transition of vanadium dioxide (VO2). The modulators designed are based on the C-shaped slot antenna array. The slot antennas are made of the VO2 films on c-sapphire substrates. The C-shaped slot antennas are active only when the VO2 is in its metallic phase, i.e. at temperatures T > TC ∼68 °C. At T > TC, the first kind acts as a THz multi-focus lens which converges an incident THz plane wave into four focal spots and the second kind as an Airy beam generator. We characterized the function of two THz wavefront modulators over a broad frequency range, i.e. from 0.3 to 1.2 THz. Such thermally switchable THz wavefront metasurface modulators with a capability of dynamically steering THz fields will be of great significance for the future development of THz active devices.
TL;DR: In this article, an effective methodology to design a compact four-element multiple-input-multiple-output (MIMO) antenna with high performance over ultra-wide bandwidth (BW) is presented and discussed.
Abstract: In this study, an effective methodology to design a compact four-element multiple-input-multiple-output (MIMO) antenna with high performance over ultra-wide bandwidth (BW) is presented and discussed. Taking the advantages of symmetry of most planar ultra-wideband (UWB) antennas, an asymmetric feeding scheme technique is utilised to chop a previously developed UWB slot antenna with overall dimensions of 30 mm × 30 mm into two halves to yield a more compact structure while retaining its overall frequency- and time-domain performances. Benefiting from orthogonal orientation, a compact UWB MIMO antenna system is arranged using four half-sized elements. The proposed MIMO antenna has an overall size of 40 mm × 40 mm and exhibits impedance BW from 2.94 to more than 14 GHz (10 dB return loss) with port isolation better than 17 dB over the entire operating band without using any decoupling structures. This is achieved via the inherent directional radiation properties of slot antenna elements and their asymmetrical placements. Envelope correlation coefficient is computed, and it is within the acceptable limit, which validates the design concept for building a compact MIMO antenna system with good performance.