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Most existing dichroic metasurfaces have limitations such as single operating band, single functionality, fixed dichroic performance or only adjustable in a single dimension, as well as complex structure. Here, we propose a terahertz dichroic device based on patterned graphene layer and gold layer to address these limitations. By utilizing the anisotropy endowed by the patterned graphene layer and the gold layer, the proposed device can achieve both dual-band circular dichroism (CD) and linear dichroism (LD), with maximum CD values of 0.866 at 1.09 THz and −0.614 at 1.76 THz, and maximum LD values of 0.779 at 0.51 THz and −0.633 at 0.76 THz. Meanwhile, the dichroism of the device can be regulated through multiple dimensions, i.e., the rotation angle of the top patterned graphene layer, the Fermi level of graphene and the incident angle. The proposed dichroic device offers multi-functionality, multi-band operation and multi-dimensional adjustability with a relatively simple structure, and is expected to be widely used in the fields of terahertz imaging, polarization detection, optical sensing and biological spectroscopy. • A multifunctional THz device which can realize both circular dichroism and linear dichroism is proposed. • The THz dichroism device can operate in multiple frequency bands. • Its performance is dynamically tunable by multiple ways. • This multifunctional device may have great potential in miniaturized THz systems. [ABSTRACT FROM AUTHOR]

This paper proposes a novel reconfigurable frequency selective surface (FSS) structure for ultra-wide band (UWB) and multi-band applications. The proposed structure is a simple single layer FSS printed on 10 mm × 10 mm × 1.6 mm FR4 substrate. This structure embraces a simple square loop on the front side of the substrate whereas; another one along with two vertical arms is incorporated on the backside. Innovatively, a wise combination of diodes is embedded on the substrate's backside which are handled through a DC feed line circuit. By an effective diodes switching, three operating modes are attained. In the context of UWB filtering, the proposed FSS contributes in remarkable rejection of UWB frequencies through the “ON” state of all diodes. However, assigning a specific set of diodes in “ON” state provokes multi-band operating mode in which WiMAX, WLAN, and Ku bands are rejected. Moreover, setting all the diodes at “OFF” state extends the rejection capabilities by dismissing an additional frequency range. Furthermore, a remarkable notice relates to higher attenuation in shielding effectiveness (SE) acquired for rejection bands. Extensive numerical and experimental studies are devised to found a suitable comparison platform. The close agreements between the obtained results are acknowledging the suitable performance of the proposed FSS. [ABSTRACT FROM AUTHOR]

The analysis of multi-band operation of printed co-planar waveguide (CPW) feed monopole antenna was presented in this paper. The ground-strip of the CPW structure was regarded as a low impedance path for returning currents with constant potential across its area, but it is not a perfect-ground, it has significant reactance to act a radiator for the related frequency. Therefore, based on the Gaussian Filter Model (GFM), the quantitative values of inductance and capacitance of the proposed antenna will be derived from the decomposed CPW structure. Measured and Ansoft HFSS simulation results are presented to confirm the results which are obtained by using decomposed GFM. Moreover, the asymmetric ground-strip of CPW is also experimentally investigated. Experimental results are shown to verify the validity of theoretical work. [ABSTRACT FROM AUTHOR]

A novel chip antenna for dual-/tri-band operation is presented in this article.The design consists of a pair of forked metal strips with different lengths. The longer strip is folded onto an FR4 base to simultaneously introduce the quarter- and half-wavelength modes as the first two operating bands. By varying the included angle between the sections of strip on the opposite base layers, the frequency ratio of the first two operating modes is adjusted over a large range of 1.34–2.29. In addition, the shorter excited strip introduces the quarter-wavelength mode as the third operating band. The tri-band operation with a small dimension of 13 × 5 × 0.8 mm3 for 2.5/3.5/5.5 GHz WiMAX applications is implemented. Experimental results show that the proposed antenna has good omnidirectional radiation patterns and steady antenna gains over all operating bands. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1286–1290, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25211 [ABSTRACT FROM AUTHOR]

Novel designs for compact multi-band single feed triangular microstrip antenna are presented. Shorting wall is introduced for 50% size reduction while inserted slits are added for tri-band operation. Triangular shorting capacitive plate is inserted to reach 75% size reduction from conventional λ0/2 triangular microstrip antenna. Gain greater than 8 dBi is achieved. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 487–491, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22143 [ABSTRACT FROM AUTHOR]

A folded and bent internal loop antenna (FABILA) suitable for multiband operation is presented. The proposed antenna consists of a radiating element of the folded and bent loop structure with a rectangular stub, feeding post, shorting post, and dielectric supporter on the experimental PCB. A shorted half-wavelength loop element resonates at the lower-frequency band, and higher-band operation is achieved by two adjacent higher modes. Especially at the second higher-order mode, the rectangular stub compensates the strong imaginary part of the input impedance of the antenna efficiently, so that the antenna can provide enough bandwidth to cover the GSM (880–960 MHz), DCS (1710–1850 MHz), and PCS (1850–1990 MHz) bands. An IE3D simulator is employed to analyze the proposed antenna in the design process and to compare it with the experimental results. The measured peak gains of the proposed antenna are -0.2, 1.5, and 1.1 dBi for GSM, DCS, and PCS, respectively. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 463–467, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21379 [ABSTRACT FROM AUTHOR]

This paper presents a design for stacked triangular patch antennas with two feeds for achieving dual-polarized operations. The top radiating element of the stacked structure is a single-feed, triangular, planar inverted-F antenna (PIFA) with a V-shaped slot, which can radiate an omnidirectional dipole-like pattern with linear polarization at two separated frequencies. The bottom radiating element is an equilateral-triangular microstrip patch with two shorting pins, which provides circularly polarized broadside radiation patterns. The proposed stacked structure can not only provide a compact design, but can also be easily installed. In addition, an isolation of better than -20 dB between the feed ports was obtained. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 502–505, 2003 [ABSTRACT FROM AUTHOR]

In this study, a new design of a tri-band multiple-input–multiple-output (MIMO) antenna array is proposed for fifth-generation (5G) cellular systems. Its structure is composed of eight identical planar-inverted F antenna (PIFA) elements placed at different edge corners of the handset mainboard with overall dimensions of 150 × 75 mm2. The PIFA elements and ground plane of the MIMO antenna system are arranged on the back layer of the platform, which makes the design easy to integrate with the handset circuit. For S11 ≤ −10 dB, the radiation elements of the MIMO design operate at the frequency ranges of 2.5–2.7 GHz, 3.4–3.75 GHz, and 5.6–6 GHz covering the long-term evolution (LTE) 41, 42/43, and 47 operation bands, respectively. The array achieves better than 15 dB return loss results across the three operating bands. The presented antenna array not only exhibits multi-band operation but also generates the polarization diversity characteristic, which makes it suitable for multi-mode operation. The proposed antenna array was simulated and experimentally tested. Fundamental characteristics of the proposed design are investigated. It offers three band S-parameters with acceptable isolation and dual-polarized radiation with quite good efficiency and gain results. Besides this, the total active reflection coefficient (TARC) and envelope correlation coefficient (ECC) results of the PIFAs are very low over the bands. In addition, the radiation characteristics of the MIMO antenna in the presence of the user and handset components are studied. Moreover, a new and compact phased array millimeter-wave (MM-Wave) antenna with broad bandwidth and end-fire radiation is introduced which can be easily integrated into the smartphone antenna system. Due to its good performance and simple structures, the proposed smartphone antenna array design is a good candidate for future multi-mode 5G cellular applications. [ABSTRACT FROM AUTHOR]