Antenna Theory And Design

This paper presents a compact and low cost MIMO (Multiple-Input-Multiple-Output) Bowtie dielectric resonator antennas for two, four and eight elements for public safety entities (4.94–4.99 GHz) and indoor WLAN (5.15–5.35 GHz) applications. The fractional impedance bandwidth (4.72 GHz – 5.44 GHz) is 14.17% for all ports and strengthens the targeted frequency range gain. Two bubbled I-shape embedded inside the rectangular box defective ground structure to enhance the separation between ports by etching therefore over the operating frequency band, isolation between ports exceeds 25 dB and maximum ECC (envelope correlation coefficient) of 0.04. The designed compact unit cell antenna has a dimension of 30 × 25.6 mm2 (i.e. 0.5λ0 × 0.4 λ0 where λ0 is calculated at 5.2 GHz in the free space) and finally proposed 8-element antenna having a size of only 120 × 51.2 mm2 (2.07 λ0 × 0.88 λ0). Within their finest values, MIMO diversity performance parameters are obtained. The gain of the antenna unit cell, two, four and eight elements are 5.24 dBi, 5.49 dBi, 5.68 dBi and 6.2 dBi respectively and these gain values are most suitable for WLAN applications. To show the simulated performance, a prototype of all radiators would be manufactured and tested experimentally and measured results are good agreement with simulation result.

Compact symmetrical slot coupled linearly polarized two/four/eight element MIMO bowtie DRA for WLAN applications

The triangular microstrip patch antenna is frequently accustomed to wireless intelligence. Sundry substrates such as FR4 epoxy, Bakelite, Galas, FerrA6S have accustomed to layout the patch antenna. This paper exhibits a current layout with a photonic crystal (PhC). By accustoming this photonic crystal we diminish the signal drop by governing and employing the incandescence discharge. Here, we are accustoming to Roger ro4350 substrate material, which has a limited signal drop due to PCB concrete using the signal. The return drop is diminished and gain is upgraded by applying photonic crystal when correlated with the conventional antenna. Terahertz (THz) frequency is applied which perforates through ingredients opaque to an alternative fragment of the electromagnetic spectrum. In this paper, the investigation on the designed antenna is performed with different triangular lattice of various outer radius (OTR) and inner radius (INR). Microstrip antenna is designed by CST software. High gain and decreased return loss is obtained in the triangular lattice of OTR 0.4µm and INR 0.2 µm. Additionally these triangular lattice structures are accustomed to improve gain and reduce the return loss.

Investigation of Equilateral Triangular Microstrip Patch Antenna using Photonic Crystal

Marine radars are used to measure the bearing and distance of ships, to navigate and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. The asymmetrical sum patterns are very useful for marine radars when the ships sail in turbulent waters, the ships are subject to roll and pitch. Under these circumstances the communication is disturbed and sometimes it totally fails. In the applications, where the main beam is to point in desired direction and the sidelobes are to be suppressed to the desirable extent to reduce the ground clutter, the sum patterns with symmetric sidelobes are not suitable. The modified Elliott pattern is an excellent low-sidelobe distribution and has good efficiency. The modified Elliott pattern is itself a convenient illumination, that it can produce asymmetric patterns on both sides of the main beam. In the present work suitable amplitude and phase distributions are derived by using Fourier Transform technique to produce asymmetrical sum patterns. The weights of the each element are estimated at the source position. The source positions are found out according to Ishimuru spacing. These patterns are computed for small and large arrays. These patterns are useful in high resolution radars in point to point communication and also used in the marine radars.

Investigations on the Generation of Patterns for Marine Radar Applications

An ultra-wideband (UWB) antenna with butterfly-like coupling slot for 4-element multiple-input multiple-output (MIMO) applications is introduced in this letter. In the design of the UWB antenna unit, the proposed butterfly-like slot is adopted to improve the impedance matching and achieves the operating bandwidth of 3-12GHz. At the same time, a symmetrical T-shaped meandering strip etched on the ground and connecting with the patch through via produces a notch at 5.1-5.37GHz, which suppresses the signal interference in WLAN band simultaneously. The results show that the proposed antenna array consisting of four orthogonal elements realized good isolation of lower than -15dB without any additional decoupled structures. Also, the proposed 2×2 MIMO design exhibited good diversity performance in terms of envelop correction coefficient (ECC<0.015), diversity gain (DG>9.92dB). The gain reaches a maximum value of 6.8dBi. Simulated and Measured results are in good accordance. All of this reveals the effectiveness of the proposed antenna in MIMO system and it can be suggested as a suitable candidate for UWB applications. 

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A butterfly-like slot UWB antenna with WLAN band-notch characteristics for MIMO applications

Comparison between Rectangular and Triangular Patch Antennas

Array antennas are popular in radar and communication applications. It is possible to control the pattern characteristics from array antennas very effectively and easily. Array designers used different techniques to produce narrow beams. But it is essential to produce not only narrow beams but also other beam shapes like Square and Cosecant beams. These shaped beams are extremely useful in search, track radars and also for ground mapping. The difference patterns are often produced from sum patterns with additional phase, but in the case of marine radars either sum or difference patterns are asymmetrical in their sidelobe structure. In view of the above facts intensive investigations are carried out in the present work to generate asymmetrical difference patterns form Cosecant patterns with Fourier series, Fourier Transform and Woodward-Lawson methodologies.

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Studies on Difference Patterns from Cosecant Patterns

In this communication, a low-cost four/eight-element MIMO antenna is proposed for Wi-MAX (IEEE 802.16d) and 5G applications band. A reverse U-shaped slot is introduced in the radiated structure to resonate the antenna in lower resonating bands. The Antenna covers the measured frequency range from 3.45 GHz to 3.55 GHz. An Electromagnetic coupling among the four/eight MIMO elements affects the overall MIMO system. To minimize the coupling between antenna elements, a multiple dumb-bell shaped parasitic element is inserted between the MIMO radiating elements. Due to that, the inter isolation is achieved by nearly −18 dB. Apart from the isolation, the other MIMO performance is widely investigated using Ansys HFSS and CST Microwave studio electromagnetic software. The MIMO antenna diversity parameters like ECC and D.G. of the proposed eight-element is calculated using radiation parameter method and found   9.5 respectively. The proposed four-element and eight-element of MIMO antenna occupies a place of 70 × 75.5 mm2 and 69 × 144 mm2, respectively. The prototype is fabricated on low-cost FR-4 substrate using MITS eleven lab and measured using Rohde & Schwarz ZVL vector network analyzer. The simulated and measured results show good matching between them.

K. Srinivasa Naik

Papers

Compact symmetrical slot coupled linearly polarized two/four/eight element MIMO bowtie DRA for WLAN applications

Investigations on the Generation of Patterns for Marine Radar Applications

Comparison between Rectangular and Triangular Patch Antennas

Studies on Difference Patterns from Cosecant Patterns

Eight Element Low-Cost Microstrip MIMO Antenna for Wi-MAX and 5G Applications