Search

This article proposes a low‐profile ultra‐wideband (UWB) antenna for breast tumor detection using the monostatic radar‐based microwave imaging (RBMI) technique. The proposed UWB antenna consists of a circular patch and ground plane along with a modified tapered feed line having a total size of 13 × 9 × 1.6 mm3. The designed antenna operates from 4 to 11 GHz based on a −10 dB reflection coefficient with a peak gain of 9.5 dBi at 4.8 GHz. Experimental validation is carried out after fabricating the prototype of the UWB antenna and the breast mimic. The measured backscattered signals are captured using the vector network analyzer (E‐5063A) by keeping the antenna at 10 mm from the breast phantom. After that, post‐processing of the measured data is done to detect the exact depth and location of the malignant tissue. The proposed antenna uses UWB band frequency of operation because it has some unique features, that is, it provides immunity to multipath fading, has a simple design, has a low cost of fabrication, and has biological friendliness. Moreover, due to the proposed antenna's resonance at a lower resonant frequency better depth of penetration is achieved in human body phantoms and the proposed antenna provides specific absorption rates (SAR) of 0.877 W/kg over 1 g of tissue at 4.8 GHz, which is an acceptable limit for SAR as per FCC guidelines. Therefore, the proposed antenna and monostatic RBMI technique are good candidates for breast tumor detection. [ABSTRACT FROM AUTHOR]

The proposed work contains a quasi-self-complementary (QSC) half-cut flower-shaped ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with dual-band-notch characteristics. The overall size of the antenna is 27 × 39 mm2, which offers impedance bandwidth from 2.67 GHz to 11.7 GHz. The inter-port isolation is more than 15 dB over the FCC defined UWB range of frequencies. A reverse 2-shaped slit is etched off from a flower-shaped patch to reject the interfering WiMAX/C-band (3.28–4.19 GHz), whereas an inverse P-shaped stub is placed near the feed arm a notch at the WLAN band (5.1–6.15 GHz). Further, the performance of the proposed antenna is analysed by comparing the simulated results with the fabricated ones. Moreover, diversity parameters such as envelope correlation coefficient (ECC), channel capacity loss (CLL), mean effective gain (MEG), effective diversity gain (EDG) and total active reflection coefficient (TARC) are computed, which makes the proposed QSC UWB-MIMO antenna a suitable candidate for high-speed wireless applications. [ABSTRACT FROM AUTHOR]

This paper presented a compact quad-element flower-shaped (FS) multiple-input multiple-output (MIMO) antenna for ultra-wideband (UWB) communication. The designed antenna exhibits ultra wideband characteristics whose impedance bandwidth (for S11 ≤ − 10 dB) ranges from 3.1 to 11.7 GHz and the inter-port isolation is better than − 14 dB over operating frequency without any decoupling structure. The proposed electrically small (32 × 32 mm2) FS quad-element MIMO antenna is printed on a low-cost FR4 substrate. An FS radiating element is formed by merging four same dimension ellipses at 45° to each other. The top layer of the proposed structure comprises four FS radiating elements, which are positioned orthogonal to each other. The bottom layer consists of asymmetrical ground structures which offer good impedance matching and low mutual coupling between radiating elements at the desired operating frequency band. Besides, the proposed quad-element MIMO antenna with the shared ground is also designed and tested. Its simulated results show satisfactory inter-port isolation of around − 10 dB over frequencies 3.08–11.48 GHz. The antenna provides a low envelope correlation coefficient (ECC < 0.03) and appreciable other diversity parameters. Moreover, the measured 2D radiation patterns confirm the pattern diversity, which will help to mitigate the multipath fading. Also, the simulation study of the MIMO antenna in the actual environment is carried out. Finally, the numerical result of both proposed antennas with the isolated and shared ground is verified experimentally and found suitable for UWB-MIMO applications. [ABSTRACT FROM AUTHOR]

In this article, a compact dual‐element quasi‐self‐complementary (QSC) multiple‐input multiple‐output (MIMO) antenna for ultra‐wideband (UWB) communication is presented. The overall area of the antenna is 32 × 39 mm2 (0.26 λl × 0.31 λl, where, λl is at lowest cutoff frequency) which is designed on low cost FR‐4 substrate. It has two half‐cut flower shaped (HCFS) radiators on its top which is formed by merging four ellipses of same eccentricity and then splitted in two halves at the center. On the other side, quasi‐self‐complementary phenomenon is introduced via etching slots which are complement to the radiator's shape. Also, a rectangular slit on the ground plane just below the feed line improves impedance matching. The proposed antenna operates in the range of frequencies 2.43GHz to 11.2GHz with high inter‐port isolation of greater than ‐19 dB over entire frequency of interest. Moreover, the stability of the design is validated in terms of diversity parameters [envelop correlation coefficients (ECC), channel capacity loss (CCL), mean effective gain (MEG), and Effective diversity gain (EDG)] and radiation parameters which makes it suitable for UWB‐MIMO wireless application. [ABSTRACT FROM AUTHOR]

ABSTRACT A triple band polarization insensitive compact artificial magnetic conductor (PI-AMC) structure is investigated as a back plane of a compact ultrawideband (UWB) antenna in low profile configuration for the performance analysis. The AMC bands observed about 4, 7.2, and 10.5 GHz. The AMC bands can be tuned independently with the help of the PI-AMC shape parameters. With the use of the PI-AMC as a back plane for an UWB monopole antenna, the lower operating frequency decreased compared to the PEC back plane. Further, radiation in the forward direction and gain improvement over the UWB is observed due to AMC back plane. The details of the design, simulation, and measurement of the proposed PI-AMC structure and UWB antenna with PI-AMC structure are presented. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1900-1906, 2016 [ABSTRACT FROM AUTHOR]

This manuscript presents, a compact dual band notched Ψ-shaped ultrawideband (UWB) monopole antenna. The antenna consists of a Ψ-shaped radiating patch loaded with the ω-shaped and inverted C-shaped slots. By properly optimizing the shape parameters of the ω-shaped slot and the inverted C-shaped slot along with the rectangular stub, dual band notched characteristics for Worldwide Interoperability for Microwave Access (3.3-3.8 GHz) and Wireless Local Area Network (5.15-5.825 GHz) is achieved, respectively. An equivalent RLC resonant circuit is proposed for the dual band notched characteristics of the antenna which is based on the current distribution and the input impedance characteristics of the antenna. The simulated and measured values of the VSWR and the input impedance characteristics are also compared with the values obtained from the equivalent circuit analysis. The simulated and measured results show that the proposed antenna has 2.5-11.5 GHz (about 129 % fractional bandwidth) operational impedance bandwidth (VSWR < 2) with dual band notched characteristics, stable radiation patterns, and good time domain characteristics which are essential for the UWB applications. [ABSTRACT FROM AUTHOR]

ABSTRACT A low profile (≈0.09λ2.6 GHz) platform tolerant antenna system having a monopole antenna placed over a multiband artificial magnetic conductor (AMC) is presented for ultrawideband (UWB) applications. The AMC structure is a simple triple band structure having planar array of unit cells. The AMC behavior i.e., zero reflection phase point observed about 4.0, 7.2, and 10.3 GHz, respectively. The simulated and measured results of the antenna when placed in free space, on large metal plate, and over numeric body model/human hand are also compared. The results show that the proposed UWB antenna with AMC structure having platform tolerant properties when placed on large metallic plate and body model for on body applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1052-1059, 2016 [ABSTRACT FROM AUTHOR]

An inhomogeneous anisotropic (IA) artificial material (AM) is proposed having epsilon-near-zero (ENZ) characteristics and effective refractive index >1, simultaneously, in the same direction. Further, the proposed IA-AM is utilized for the gain enhancement of Vivaldi antenna for ultra-wideband (UWB) applications. The IA-AM consists of two types of compact meandered line-based anisotropic artificial material with ENZ characteristics in two adjacent narrow bands of 5.5-8.5 and 8-11.5 GHz. However, the non-resonant behavior of the artificial material in other direction appears with high refractive index property in broadband region. The combination of both the unit cells with broadband ENZ and high refractive index property is used to improve the gain of the Vivaldi antenna in broadband. The proposed IA-AM-loaded Vivaldi antenna exhibits a gain enhancement of up to 2 dBi compared to the original antenna in the operating frequency band of 3.1-12 GHz with | S| < −10 dB. The proposed antenna shows nearly stable unidirectional radiation patterns with high directivity and nearly flat group delay. [ABSTRACT FROM AUTHOR]

ABSTRACT To mitigate the interference with coexisting wireless systems operating over 3.3-3.6 GHz, 5.15-5.825 GHz, and 7.725-8.5 GHz bands, a novel triple band notched coplanar waveguide fed pitcher-shaped planar monopole antenna is presented for ultrawideband applications. Bands notched characteristics are achieved using a novel mushroom type electromagnetic band gap structure like resonator and a split ring slot. A conceptual equivalent RLC (Resistor-Inductor-Capacitor)-resonant circuit is presented for the band notched characteristics . Furthermore, the input impedance and VSWR (voltage standing wave ratio) obtained from the equivalent circuit are validated with simulated and measured results. Performances of the antennas in both, the frequency domain and the time domain are investigated. The simulated and measured results demonstrate that the proposed antennas have wide impedance bandwidth, nearly stable radiation patterns, and suppression of gain and total radiation efficiency at notched bands. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:795-806, 2015. [ABSTRACT FROM AUTHOR]

In this manuscript, a compact UWB with dual band‐notched planar monopole antenna is investigated. The band notched characteristics at WiMAX and WLAN is obtained by connecting two pairs of stubs to the modified ground plane. The size of proposed antenna is 25(W) × 30(L) × 1.6(H) mm3 which consists of a fork shaped structure as a main radiating element and excited with a 50‐Ω microstrip line. The proposed antenna covers Bluetooth frequency band (2.4‐2.48 GHz) along with UWB spectrum without increasing the size of the antenna. The measured operating frequency of the proposed antenna is from 2.4 to 12.8 GHz along with WiMAX and WLAN band‐notched. Moreover, the measured gain of the proposed antenna varies between 2 and 6 dBi except notched band. At notched frequencies, it is −1 and −6 dBi at WiMAX and WLAN, respectively. The total antenna efficiency varies from 80% to 95% except notched frequency bands. The radiation patterns and time domain characteristics are also analyzed and found suitable for the modern UWB applications. Finally, a prototype of dual band‐notched antenna is manufactured and its characteristics are measured using network analyzer. The simulated and measured results are found in close agreement. [ABSTRACT FROM AUTHOR]