Capacity and Spatial Correlation Measurements of Compact MIMO Antennas

The dual-port compact multiple-input multiple-output(MIMO)dipole antennas with close spacing d of 0.5λand 0.3λare designed,and some electromagnetic band gap(EBG)structures are inserted between them to reduce mutual coupling.Those MIMO antennas with d=0.5λand 0.3λ,and with different mutual couplings are fabricated and measured,the channel capacity and correlation coefficient(CC)are analyzed and compared in a rich multipath reverberation chamber(RC),an office and a conference room.Results show that if d is reduced from 0.5λto 0.3λ,in the RCs,channel capacities of all the antennas are very close to that of the i.i.d.Rayleigh channel,although the average CCs are increased from 0.168 in the nonlossy RC to 0.269 in the lossy RC.In the office and conference rooms,compared with the RC,the average capacities of those antennas get a slight reduction,however,in most cases,the capacity of d=0.5λis larger than that of d=0.3λ,and the antennas with EBG have a larger capacity compared with the antennas without EBG,with a corresponding reduction of CC.A non-line-of-sight(NLOS)scenario of through-the-wall is also investigated.

A Compact Self-Isolated MIMO Antenna System for 5G Mobile Terminals

A compact self-isolated Multi Input Multi Output (MIMO) antennaarray is presented for 5G mobile phone devices. The proposed antenna systemis operating at the 3.5 GHz band (3400–3600 MHz) and consists of eight antennaelements placed along two side edges of a mobile device, which meets the currenttrend requirements of full-screen smartphone devices. Each antenna element isdivided into two parts, a front part and back part. The front part consists of anI-shaped feeding line and a modified Hilbert fractal monopole antenna, whereasthe back part is an L-shaped element shorted to the system ground by a0.5 mm short stub. A desirable compactness can be obtained by utilizing the Hilbert space-filling property where the antenna element’s overall planar size printedon the side-edge frame is just (9.57 mm × 5.99 mm). The proposed MIMO antenna system has been simulated, analyzed, fabricated and tested. Based on the selfisolated property, good isolation (better than 15 dB) is attained without employingadditional decoupling elements and/or isolation techniques, which increases system complexity and reduces the antenna efficiency. The scattering parameters,antenna efficiencies, antenna gains, and antenna radiation characteristics areinvestigated to assess the proposed antenna performance. For evaluating the proposed antenna array system performance, the Envelope Correlation Coefficients(ECCs), Mean Effective Gains (MEGs) and channel capacity are calculated.Desirable antenna and MIMO performances are evaluated to confirm the suitability of the proposed MIMO antenna system for 5G mobile terminals.

Metamaterial-Based Compact Antenna with Defected Ground Structure for 5G and Beyond

In this paper,a unit cell of a single-negative metamaterial structure loaded with a meander line and defected ground structure(DGS)is investigated as the principle radiating element of an antenna.The unit cell antenna causes even or odd mode resonances similar to the unit cell structure depending on the orientation of the microstrip feed used to excite the unit cell.However,the orientation which gives low-frequency resonance is considered here.The unit cell antenna is then loaded with a meander line which is parallel to the split bearing side and connects the other two sides orthogonal to the split bearing side.This modified structure excites another mode of resonance at high frequency when a meander line defect is loaded on the metallic ground plane.Specific parameters of the meander line structure,the DGS shape,and the unit cell are optimized to place these two resonances at different frequencies with proper frequency intervals to enhance the bandwidth.Finally,the feed is placed in an offset position for better impedance matching without affecting the bandwidth The compact dimension of the antenna is 0.25λL×0.23λL×0.02λL,whereλL is the free space wavelength with respect to the center frequency of the impedance bandwidth.The proposed antenna is fabricated and measured.Experimental results reveal that the modified design gives monopole like radiation patterns which achieves a fractional operating bandwidth of 26.6%,from 3.26 to 4.26 GHz for|S11|<−10 dB and a pick gain of 1.26 dBi is realized.In addition,the simulated and measured crosspolarization levels are both less than−15 dB in the horizontal plane.

A Compact Tri-Band Antenna Based on Inverted-L Stubs for Smart Devices

We designed and constructed a novel,compact tri-band monopole antenna for intelligent devices.Multiband behavior was achieved by placing inverted-L shaped stubs of various lengths in a triangular monopole antenna fed by a coplanar waveguide.The resonance frequency of each band can be controlled by varying the length of the corresponding stub.Three bands,at 2.4(2.37-2.51),3.5(3.34-3.71),and 5.5(4.6-6.4)GHz,were easily obtained using three stubs of different lengths.For miniaturization,a portion of the longest stub(at 2.4 GHz)was printed on the opposite side of the substrate,and connected to the main stub via a shorting pin.To validate the concept,the antenna was fabricated on a low-cost 1.6-mm-thick FR-4 substrate with dimensions of 20×15×1.6 mm^(3).The antenna exhibited a moderate average gain of 2.9 dBi with an omnidirectional radiations over the bandwidths required for RFID,Bluetooth,ISM,WiMAX,andWLAN-band applications.These features make the antenna suitable for compact smart devices.

Super Compact UWB Monopole Antenna for Small IoT Devices

This article introduces a novel,ultrawideband(UWB)planar monopole antenna printed on Roger RT/5880 substrate in a compact size for small Internet of Things(IoT)applications.The total electrical dimensions of the proposed compact UWB antenna are 0.19λo×0.215λo×0.0196λo with the overall physical sizes of 15 mm×17 mm×1.548 mm at the lower resonance frequency of 3.8 GHz.The planar monopole antenna is fed through the linearly tapered microstrip line on a partially structured ground plane to achieve optimum impedance matching for UWB operation.The proposed compact UWB antenna has an operation bandwidth of 9.53 GHz from 3.026 GHz up to 12.556 GHz at−10 dB return loss with a fractional bandwidth(FBW)of about 122%.The numerically computed and experimentally measured results agree well in between.A detailed time-domain analysis is additionally accomplished to verify the radiation efficiency of the proposed antenna design for the ultra-wideband signal propagation.The fabricated prototype of a compact UWB antenna exhibits an omnidirectional radiation pattern with the low peak measured gain required of 2.55 dBi at 10 GHz and promising radiation efficiency of 90%.The proposed compact planar antenna has technical potential to be utilized in UWB and IoT applications.

Comparative Design and Study of A 60 GHz Antenna for Body-Centric Wireless Communications

In this paper performance of three different designs of a 60 GHz highgain antenna for body-centric communication has been evaluated. The basic structure of the antenna is a slotted patch consisting of a rectangular ring radiator withpassive radiators inside. The variation of the design was done by changing theshape of these passive radiators. For free space performance, two types of excitations were used—waveguide port and a coaxial probe. The coaxial probe signifi-cantly improved both the bandwidth and radiation efficiency. The centerfrequency of all the designs was close to 60 GHz with a bandwidth of more than5 GHz. These designs achieved a maximum gain of 8.47 dB, 10 dB, and 9.73 dBwhile the radiation efficiency was around 94%. For body-centric applications,these antennas were simulated at two different distances from a human torsophantom using a coaxial probe. The torso phantom was modeled by taking threelayers of the human body—skin, fat, and muscle. Millimeter waves have lowpenetration depth in the human body as a result antenna performance is lessaffected. A negligible shift of return loss curves was observed. Radiation efficiencies dropped at the closest distance to the phantom and at the furthest distance, theefficiencies increased to free space values. On the three layers human body phantom, all three different antenna designs show directive radiation patterns towards offthe body. All three designs exhibited similar results in terms of center frequency andefficiency but varied slightly by either having better bandwidth or maximum gain.

A Modified Split⁃Ring Resonator Antenna for Radio Frequency Identification Tag

A compact antenna formed by three concentric split rings for ultra-high frequency(UHF)radio frequency identification(RFID)tag is proposed in this paper.The antenna is composed of two parts,an outer short-circuited ring modified from a traditional split-ring resonator(SRR)antenna and an inner SRR load,so the antenna can be regarded as a short-circuited ring loaded with SRR.According to the transmission line theory,to conjugate match with the capacitive input-impedance of a tag chip,the length of the short-circuited ring isλg/4 shorter than that of an open-circuited dipole of a traditional SRR antenna,whereλg is the wavelengh of the operating frequency.Hence,the size of the proposed antenna is more compact than that of the traditional SRR antenna.Thereafter,the proposed antenna is simulated and optimized by ANSYS high-frequency structure simulator(HFSS).The impedance,efficiency,and mutual coupling of the fabricated antenna are tested in a reverberation chamber(RC).The results show that the size of the presented antenna is 83%smaller than that of the traditional SRR antenna and the proposed antenna can cover the whole UHF RFID operating frequency band worldwide(840—960 MHz).The measured read range of the tag exhibits maximum values of 45 cm in free space and 37 cm under dense tag environment.

Helix Inspired 28 GHz Broadband Antenna with End-Fire Radiation Pattern

This paper presents the design and characterization of a via free planar single turn helix for 28 GHz broadband applications.The proposed antenna is designed using ROGERS RO4003 material,having a simple structure and end-fire radiation pattern.The antenna comprises of a compact dimension of 1.36λ_(0)×0.9λ_(0) with a thickness of 0.0189λ_(0)(whereλ_(0) is the free-space wavelength at the central frequency of 28 GHz).Parametric study has been carried out to investigate the impact of key design parameters and to achieve an optimum design.Results show a good agreement between the simulated and measured results.A single turn helical inspired antenna covers−10 dB impedance bandwidth of 26.25-30.14 GHz having a peak gain of 5.83 dB and radiation efficiency up to 85%.Moreover,linear array configurations with 2 and 4 elements have been analyzed for applications with higher gain and space constraints.Presented array configurations are suitable for applications having space constraints in one dimension.Results show that peak gain up to 8.2 dB and 11.1 dB can be achieved with 2 and 4 elements,respectively.Due to its simple planar and via free structure,this antenna is suitable for 5G communications and for sensing,imaging,IoT and tracking applications at 28 GHz band spectrum.

Optical true time-delay for two-dimensional phased array antennas using compact fiber grating prism

A two-dimensional(2D) optical true-time delay(TTD) beam-forming system using a compact fiber grating prism(FGP) for a planar phased array antenna(PAA) is proposed. The optical beam-forming system mainly consists of a TTD unit based on the same compact FGP, one tunable laser for elevation beam steering, and a controlled wavelength converter for azimuth beam steering. A planar PAA using such 2D optical TTD unit has advantages such as compactness, low bandwidth requirement for tunable laser sources, and potential for large-scale system implementations. The proof-of-concept experiment results demonstrate the feasibility of the proposed scheme.

Dual-band LTCC antenna based on 0.95Zn_2SiO_4-0.05CaTiO_3 ceramics for GPS/UMTS applications

In this paper, we present a compact low-temperature co-fired ceramic（LTCC） dual-band antenna by using the electromagnetic coupling effect concept for global positioning system（GPS） and universal mobile telecommunication system（UMTS） applications. The overall dimension of the antenna is 8.6 mm × 13.0 mm × 1.1 mm. It consists of double meander lines and a via hole line. The top meander line operates at the upper band, and the bottom radiating patch is designed for the lower band. The via-hole line is employed to connect the double meander lines. Because of the effect of the coupled line,total dimension of the proposed antenna is greatly reduced. With the 2.5： voltage standing wave ratio（VSWR） impedance bandwidth definition, the lower and upper bands have the bandwidths of 110 MHz and 150 MHz, respectively. The proposed antenna is successfully designed, simulated, and analyzed by a high frequency structure simulator（HFSS）. And the antenna is manufactured by using the 0.95Zn2SiO4-0.05 CaTiO3ceramics（εr = 7.1, tanδ = 0.00038） that is prepared by ourselves. The results show that the antenna is compact, efficient, and of near omnidirectional radiation pattern.

Design and study of a compact planar ultra-wideband antenna

In this paper,a novel,small,and compact planar antenna for ultra-wideband(UWB)applications is proposed.The antenna is an extension of microstrip slot antenna technology.To achieve ultra-wideband characteristics,a tapered microstrip fork-shaped stub has been employed.A symmetric polygon wide slot has been placed on the antenna ground.The design was investigated numerically to obtain proper dimensions for the antenna and a prototype was constructed.The return loss,pattern and gain of the prototype antenna have been measured.The transient pulse signal fidelity has also been investigated by finite-difference time-domain(FDTD)method.Experimental results show that the proposed antenna design has promising characteristics for UWB applications.