Quad-Element Implantable MIMO Antenna for Wireless Capsule Endoscopy.

This letter presents a design of four-element wideband multiple-input-multiple-output (MIMO) antenna with improved isolation that covering 1.9GHz-5.2GHz for 5G smartphone application. The basic structure of the proposed MIMO antenna is meandering monopole; a dual-band is generated by involving meandering L-shape strip and inverted-F strip, then coupling with a parasitic strip to generate wideband. By etching two H-shape slots and two split-ring resonator slots at the ground can enhance the isolation between two adj acent input ports. Antenna elements are rotated symmetrically and vertically distributed around the dielectric plate, the overall dimension of the MIMO array is 54x120x13mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . A good impedance matching (return loss < -10dB), high isolation (<-16 dB), high total efficiency (>65 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup> ), and low envelope correlation coefficient (ECC, <0.05) were obtained across the operation bandwidth, the gain of the antenna is 6.1dB at 3.6GHz. Both wide bandwidth and high isolation are successfully achieved and can be well applied in 5G communication.

A novel compact multiple-input-multiple-output (MIMO) antenna with a wide impedance bandwidth and high port isolation is proposed for vehicular base stations. The design consists of four identical vertically-polarized monopole-based antenna elements, which are symmetrical about the central axis and are placed 90 degrees apart from each other. The wideband and decoupling features are theoretically analyzed and experimentally demonstrated. Four resonant frequencies are created by the F-shaped radiator, independent reflector and cross-π-shaped structure, which increase the MIMO antenna bandwidth. Parasitic stubs further improve the impedance matching in the high-frequency band. The cross-π-shaped structure acts as a decoupling function and reduces the mutual coupling, which is realized by using two metal strips shorted to the ground plane, perpendicular to each other. The etched slots further improve port isolation. The effects of imitated perfect vehicle metallic surface are also analyzed. The proposed MIMO antenna prototype is fabricated and measured to verify the concept of design. The operating frequency band is from 1.95 GHz to 6.25 GHz with a reflection coefficient of better than -10 dB, where the realized gain is higher than 3.3 dBi, and the maximum value is 6.16 dBi at 2.6 GHz. High isolation of >16.5 dB and low envelop correlation coefficient of <; 0.028 among designed MIMO antenna elements are also achieved.

Due to recent advancements in complementary metal-oxide-semiconductor (CMOS) cameras, transferring high resolution images and videos are possible in wireless capsule endoscopy. High-data-rates communication is required for such data, which is possible using multiple-input-multiple-output (MIMO) antennas. In this paper, a low-sized, compact, high-data-rate, highly isolated two-element MIMO antenna with a large bandwidth has been proposed at 2.45 GHz for wireless capsule endoscopy. The geometry of the antenna (5times 4.2 times 0.12,hbox {mm}^{3}) is kept small using meandered geometry, defected ground structure, and high permittivity of the substrate. A wider bandwidth of 620 MHz (2.15–2.77 GHz) is achieved by exciting dual-modes of the antenna using defected ground structure. Furthermore, a lower mutual coupling between the antennas (30.1 dB at 2.45 GHz) is realized, despite the small edge-to-edge gap of 0.5 mm, using combination of defected ground structure and I-shaped stub. Keeping in mind of system level configuration, this antenna is simulated and measured inside a capsule device by considering effects of the other components and the device itself. The practical measurements are performed by inserting the capsule device (containing the MIMO antenna) inside minced meat. To check the safety and effectiveness of the proposed MIMO antenna, it’s specific absorption rate (SAR) and link budget are calculated and validated. In addition, the 2times 2 channel specifications are verified which shows satisfactory performance. This antenna has high channel capacity (approx 8.2 ,hbox {bps/Hz} at hbox {SNR} = 20 ,hbox {dB}) than single-input-single-output (SISO) antennas, thus, is a suitable choice for high-data-rate capsule endoscopic devices. To the best of the authors’ knowledge, this is the first implantable MIMO antenna reported so far with such lower dimension and wider bandwidth.

The wireless communication system is steered towards the millimeter wave spectrum to achieve low latency and high-speed data rate. The MIMO antennas aid in attaining a higher data rate. The prominent spectrum at millimeter wave is Ka-band, suitable for short-range communication. The |S-parameter| response and radiation pattern of the existing MIMO antenna at this band are relatively unstable. Hence it encouraged to design and develop a four-element MIMO antenna operating at Ka-band. The antenna is a circular ring shape with two concentric rings with a plus-shape stub overlayed on circular rings. The structure is developed in four-stage with the comprehension of characteristic mode theory (CMA). The proposed structure generated Mode 2 as an efficient mode, with minor Modes 3 and 5 contributing for resonance out of five modes. The overall antenna profile is 3.27λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 3.74λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength at a resonance frequency of 28 GHz). The novel decoupling structure has improved the isolation to 30 dB and increased the bandwidth. The antenna has an operating bandwidth of 24.1-30.9 GHz, with a maximum gain of 6.5 dBi. The |S-parameter| from all the ports has an exact and stable response. The proposed antenna has resulted in bidirectional radiation tilted at an angle of 334° and 210° in the XZ plane. In the YZ plane, it has a triple beam. The radiation pattern is also stable throughout the bandwidth. The proposed MIMO antenna has a symmetrical design, demonstrating the possibility of expansion to n-element MIMO through a six-element MIMO antenna design. The article also presents the channel capacity, path loss, and link margin calculation for designed antenna line-of-sight (LOS) communication. The antenna has been evaluated with diversity parameters such as ECC, DC, CCL, TARC, and MEG.

A miniaturized ultra-wideband multiple-input multiple-output (UWB MIMO) two-port antenna with high isolation based on FR4 is designed in this article. The size of the antenna is only 18 × 28 × 1.6 mm3. The MIMO antenna consists of two identical antenna elements symmetrically placed on the same dielectric substrate in opposite directions. By loading three crossed X-shaped stubs between two unconnected ground planes, high isolation and good impedance matching are achieved. The working frequency band measured by this UWB MIMO antenna is 1.9–14 GHz, and the isolation is kept above 20.2 dB in the whole analysis frequency band. Good radiation characteristics as well as envelope correlation coefficient (ECC, &lt;0.09), mean effective gain (MEG), and channel capacity loss (CCL) in the passband meet the requirements of the application, which can be applied to the UWB wireless communication system. To verify the applicability of the proposed method for enhancing the isolation between antenna elements, the two-port antenna structure was extended to a four-port antenna structure. In the case of loading the X-shaped stubs to connect to the ground plane, the isolation of the antenna is maintained above 15.5 dB within 1.7–14 GHz.

Researchers from the Samsung Electronics Network R&D Center in Shenzhen, China, have fabricated and tested a prototype compact substrate-integrated-waveguide (SIW) cavity multiple-input-multiple-output (MIMO) antenna with potential applications in 5G communications. The triangular half mode design achieves an enhanced bandwidth by merging together two coupled modes in the required operating band and boasts high isolation and radiation efficiency. Since it was first introduced a decade ago, SIW technology has drawn significant attention from researchers, with particular appeal in the antenna community. It can be fabricated in planar form using periodic metallic vias and has the advantages of high-Q factor and high-power capacity. In addition to this, cavity antennas resonating at cavity modes and radiating energy through opened cavity edges or etched slots are well-known for good radiation performance. The SIW cavity antenna is an antenna type created by introducing SIW technology into a cavity antenna design. Antennas transmitting and receiving wireless signals are important components in communication systems. The SIW cavity antenna can not only combine the attractive characteristics of conventional cavity antennas, such as good radiation performance and unidirectional radiation pattern, and but also offers the advantages of planar SIW technology, such as low profile, convenient fabrication, and easy integration with planar circuits. Author Bing-Jian Niu in anechoic chamber holding the proposed antenna. Analytical model of the proposed SIW cavity antenna. The SIW cavity antenna reported in the teams published Letter is designed for MIMO applications. By etching three slots, a half-mode SIW cavity was divided into four eighth-mode sub-cavities. Two large sub-cavities are excited by two coaxial ports to construct two antenna elements and cavity energy is coupled from the excited sub-cavities to the unexcited sub-cavities to enhance bandwidth. Thus, a compact two-element MIMO antenna with enhanced bandwidth can be designed and achieved. As is well-known, MIMO antennas have been widely adopted in modern wireless systems. Co-author Bing-Jing Niu, however, notes that: “Two major challenges faced in the design are narrow bandwidth and poor isolation among antenna elements. In our proposed design, three slots are etched in the half-mode SIW cavity. The width, length, and position of these slots are carefully selected in our Letter.” To meet the stringent requirements on antenna fabrication for wearable and portable devices, antenna designs are becoming more and more complex. Compact two-element MIMO antennas with enhanced bandwidth and high isolation are in great demand. With an enhanced bandwidth of 160 MHz, high isolation of 19.5 dB, antenna gain of 4.9 dBi, and radiation efficiency of 72.8%, the proposed SIW cavity MIMO antenna has good specifications and properties, making it suitable for potential applications for forthcoming fifth-generation wireless communications. Etched slots in the antenna provide new perspectives and opportunities for designing SIW cavity antennas, which not only radiate cavity energy into free space but also control the coupling between adjacent sub-cavities. The challenges the group overcome were the ideal selection of slot width, length, and position to optimise their prototype for its intended applications. In the proposed design, a wide rectangle slot is considered as the de-coupler to enhance the antenna isolation while two narrow T-shaped slot are utilised as the coupler to enhance the impedance bandwidth. The novel design makes it possible to increase the channel capacity and link reliability in wireless communication channels. In the short term, this work is expected to be utilised in the sub-6 GHz band. In the longer term, massive MIMO antenna based on SIW cavities will likely be successfully developed and integrated successfully into communication networks. Mr Niu discusses the groups upcoming work and views on the future of the field: “To improve the conformal performance of planar antennas, we are considering liquid crystal polymers (LCP) as a manufacturing substrate. It has the ability to support 3D integration and low tangents up to and including millimetre-wave (MMW) applications. In addition, to improve the MIMO performance, multiple-element MIMO antennas such as four-element and eight-element, have been developed in our own research group. As one of the most pervasive core technologies, massive MIMO antennas will lead to an accelerated pace of research and development in wireless communication with the promise of significant new breakthroughs over the next decade. An unprecedented number of antennas result in major technical challenges as well as new opportunities in antenna design, channel propagation, electronic components and circuit design, and communication theory. We hope the SIW cavity antenna is a good candidate to address this issue.”

MIMO antennas are playing crucial role in satisfying high demand of wide bandwidth, high channel capacity and high data rate in wireless communication. MIMO antennas are one of the best solution to solve the problem of multipath propagation. The level of performance of the MIMO antenna is very high and steep if represented graphically but due to the use of many antennas the issue of mutual coupling occurs which deteriorates the MIMO antenna's performance. Here, the various types of monopole, fractal and hybrid antennas which can be chosen to make a MIMO system are discussed.

To meet the 5G communication requirements for smartphone terminal antennas regarding element count and isolation, this paper proposes a 12 -element MIMO antenna with shared radiators for 5G smartphones. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$12 \times 12$</tex> MIMO antenna consists of six shared-radiator antenna pairs symmetrically distributed on both sides of the substrate. Each radiator is directly excited by two feeding ports and comprises a rectangular radiating strip on the inner side of the side frame along with two L-shaped grounded radiating strips printed on the outer side. The overall dimensions of the 12-element MIMO antenna system on the side frame are <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$30 \text{mm} \times 3.2 \text{mm} \times 12$</tex>, demonstrating a compact structure. The L-shaped radiating strips printed on the outer side enhance impedance matching performance and extend bandwidth. Simultaneously, a rectangular grounding strip printed between the rectangular radiating strip and the ground plane improves common-mode currents. Assisted by this grounding strip, the antenna pair achieves self-decoupling through mode cancellation based on common-mode and differential-mode synthesis. The proposed shared-radiator antenna pair exhibits excellent isolation exceeding 11.9 dB within the operating bandwidth (3.95-5.25 GHz) and features radiation pattern diversity. Moreover, the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$12 \times 12$</tex> MIMO antenna formed by these antenna pairs achieves high channel capacity and operates within the 3.95-5 GHz bandwidth (below −10 dB in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$S_{11})$</tex>, covering the n79 band. Based on the shared-radiator antenna pair design, this architecture achieves self-decoupling and constructs a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$12 \times 12$</tex> MIMO antenna system. This MIMO system demonstrates high channel capacity while featuring a novel structure, straightforward architecture, and wide bandwidth. The proposed design exhibits significant application potential for highly integrated MIMO antennas in future 5G smartphones.

SummaryAn ultrawideband multiple‐input‐multiple‐output (MIMO) slot antenna with a small size and high isolation is introduced. Two multi‐stepped microstrip lines are used to feed the MIMO antenna and the ground plane is designed in a defective structure for achieving good impedance matching in an ultrawide frequency range. A 3T‐shaped strip is utilized to diminish the coupling between the two microstrip feed lines for isolation improvement over the operating band. Two open‐end rectangular slots are attached in the ground plane of the MIMO antenna to generate anti‐phase current for further enhancing the isolation. By using this novel method, a compact ultrawideband MIMO slot antenna is designed and measured. It obtains an ultrawide bandwidth of 162.0%, ranging from 0.63 to 6 GHz, and excellent isolation of beyond 20 dB. Additionally, our MIMO antenna achieves a very low envelope correlation coefficient (ECC) of below 0.005, indicating its good diversity performance.

This research article has proposed a compact coplanar waveguide fed four-element ultra-wide-band (UWB) multi-input-multi-output (MIMO) antenna accompanying high isolation (S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf> < −17dB) and good return loss characteristics (S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> < −10dB). The proposed antenna operates in the entire UWB range (3.1–10.6 GHz) and is also useful for 3.5/5 GHz WLAN and Wi-MAX applications. The proposed antenna comprises four identical radiating elements, a unique asymmetric staircase ground structure, and an L-shaped stub are stacked to achieve good return loss characteristics and also good impedance matching in the entire UWB band. The proposed antenna is incorporated an orthogonal arrangement to achieve the required isolation among the four radiating elements. As a result, the overall size of the intended UWB-MIMO antenna acquired 50 × 50 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> dimensions which are printed on the highly available FR-4 substrate (ε <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> = 4.4) with a thickness of 1.6 mm. The performance of the proposed MIMO antenna is thoroughly studied in terms of diversity parameters, where it has been found that ECC < 0.02 with an acceptable channel capacity loss < 0.6 bps/Hz and the other parameters DG, MEG, TARC have been evaluated and presented as well.

This letter presents a design of four-element wideband multiple-input-multiple-output (MIMO) antenna with improved isolation that covering 1.9–5.2 GHz for 5G application. The basic structure of the proposed MIMO antenna is meandering monopole; a dual-band is generated by involving meandering L-shape strip and inverted-F strip, then coupling with a parasitic strip to generate wideband. By etching two H-shape slots and two split-ring resonator slots at the ground can enhance the isolation between two adjacent input ports. Antenna elements are rotated symmetrically and vertically distributed around the dielectric plate, the overall dimension of the MIMO array is 54 mm × 120 mm × 13 mm. Reasonable layout can reduce the user's influence on the antenna performance, so that each antenna element can work normally. The prototype is simulated, fabricated and measured. A good impedance matching (return loss <− 10 dB), high isolation (<−16 dB), high total efficiency (>65%), and low envelope correlation coefficient (ECC < 0.05) were obtained across the operation bandwidth, the gain of the antenna is 6.1 dB at 3.6 GHz. Through measurement, it is found that the results are basically consistent with the simulation results, indicating that both wide bandwidth and high isolation are successfully achieved and can be well applied in 5G communication.

As discussed in the previous chapter, Low Power Communication is the key to realization of a low power sensor node. Since sensor nodes require only low data rate communication, it might sound intuitively clear that they should also naturally be low power. After all, if a node does less work, it should also consume lesser power. But somehow this doesn’t seem to fit the behavior for low data rate communication, short range radios. If we look at existing radio designs at various data rates and ranges, we see that the design space occupied is very wide. There are designs that operate at very high (~100 Mbps) data rates and designs that operate at low data rates (~100 Kbps). There are designs that take wall supply, consuming a few watts of power, while some work on batteries. If one looks at energy per bit requirements of these designs, while some designs operate at hundreds of nJ/bit, some other designs exist consuming only 0.1 nJ/bit (Fig. 2.1). Now if we plot the range over these designs and examine how they should scale according to the energy/bit requirements we should see radios working at low data rates while consuming few microwatts of power, as required by sensor networks. These designs do not exist. The reasons there aren’t any designs in this space requires us to consider the consequences of scaling traditional design as we go for lower and lower data rate. Since Shannon’s law governs the limit on the energy efficiency of radio communication and link margin vis-à-vis the channel capacity, it makes sense to have a closer look at it and then see what constraints typical radio architectures have that prevent power from scaling in low data rate applications.KeywordsSensor NodeSpectral EfficiencyLeakage PowerGain StageImpulse RadioThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

This paper proposes a high-order MIMO antenna operating at 3.5 GHz for a 5G new radio. Using an eighth-mode substrate integrated waveguide (EMSIW) cavity and considering a typical smartphone scenario, a two-element MIMO antenna is developed and extended to a twelve-element MIMO. These MIMO elements are closely spaced, and by employing multiple diversity techniques, high isolation is achieved without using a decoupling network. The asymmetric EMSIW structures resulted in radiation pattern diversity, and their orthogonal placement provides polarization diversity. The radiation characteristics and diversity performance are parametrically optimized for a two-element MIMO antenna. The experimental results exhibited 6.0 dB and 10.0 dB bandwidths of 250 and 100 MHz, respectively. The measured and simulated radiation patterns are closely matched with a peak gain of 3.4 dBi and isolation ≥36 dB. Encouraged with these results, higher-order MIMO, namely, four- and twelve-element MIMO are investigated, and isolation ≥35 and ≥22 dB are achieved, respectively. The channel capacity is found equal to 56.37 bps/Hz for twelve-element MIMO, which is nearly 6.25 times higher than the two-element counterpart. The hand and head proximity analysis reveal that the proposed antenna performances are within the acceptable limit. A detailed comparison with the previous works demonstrates that the proposed antenna offers a simple, low-cost, and compact MIMO antenna design solution with a high diversity performance.

In this article, a novel metasurface absorber is designed for RCS reduction as well as high isolation in a 4-elements MIMO antenna. A unit cell of metasurface absorber is amalgamated by concentric circular and elliptical-shaped rings with four 300 ohms lumped resistances. Absorbance at the intended frequency band (i.e. 8.75 GHz-9.00 GHz) of metasurface absorber is more than 90.0% and its reflectivity is tending to zero. Therefore, the isolation between antennas due to this absorbance is improved by 12 dB, and the total isolation of the antenna is achieved less than 23 dB. Similarly, the Radar cross-section (RCS) of the antenna is also significantly reduced by 10dBm2. This MIMO antenna with an absorbing structure is fabricated on a richly existing FR4 substrate with dimensions of 55 × 40 × 1 mm3. The performance of the designed MIMO antenna is also judged by diversity parameters similar to Envelope correlation coefficient (ECC), Directive gain (DG), Mean effective gain (MEG), Channel capacity loss (CCL), Total Active Reflection Coefficient (TARC), and channel capacity, etc. for the proposed frequency band. The simulated and measured ECC of the proposed MIMO is less than 0.073 which exhibits that this antenna is suitable for military application in radiolocation and navigation.

Four-element reconfigurable multiple-input-multiple-output (MIMO) antennas for dual band applications are proposed. The frequency reconfigurability of the proposed antennas is achieved by incorporation of three PIN diodes within the single element. The antenna covers multiple switchable operating bands for Worldwide Interoperability for Microwave Access (Wi-MAX)/Wireless Local Area Network (WLAN) applications (3.4-3.6GHz, 3.8-3.86GHz, 5.18-5.27GHz, 5.35-5.5GHz and 5.67-5.8GHz). The proposed MIMO antenna consists of 2x2 elements on a single FR4 substrate.The combinations of MIMO and reconfigurable antenna provide improved performance in terms of envelope correlation coefficient (ECC) and channel capacity loss (CCL) in multiple-frequency bands. The MIMO antenna system performance including the isolation, ECC, CCL, and the diversity gain (DG) are simulated and measured. High isolation (≥ 25dB) is achieved between reconfigurable MIMO antenna ports without any internal and external decoupling network. The proposed antenna has sufficient performance that makes it suitable for indoor access points (IAPs).