Abstract-This paper presents a rhombic patch monopole antenna applied with a technique of fractal geometry. The antenna has multiband operation in which the generator model, which is an initial model to create a fractal rhombic patch monopole, is inserted at each center side of a rhombic patch monopole antenna. Especially, a modified ground plane has been employed to improve input impedance bandwidth and high frequency radiation performance. The proposed antenna is designed and implemented to effectively support personal communication system (PCS 1.85-1.99 GHz), universal mobile telecommunication system (UMTS 1.92-2.17 GHz), wireless local area network (WLAN), which usually operate in the 2.4 GHz (2.4-2.484 GHz) and 5.2/5.8 GHz (5.15-5.35 GHz/5.725-5.825 GHz) bands, mobile worldwide interoperability for microwave access (Mobile WiMAX), and WiMAX, which operate in the 2.3/2.5 GHz (2.305-2.360 GHz/2.5-2.69 GHz) and 5.5 GHz (5.25-5.85 GHz) bands. The radiation patterns of the proposed antennas are similar to an omnidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement.Corresponding author: C. Mahatthanajatuphat (cmp@kmutnb.ac.th). 58Mahatthanajatuphat et al.

Abstract-This paper presents a multiband slot antenna with modifying fractal geometry fed by coplanar waveguide (CPW) transmission line.The presented antenna has been designed by modifying an inner fractal patch of the antenna to operate at multiple resonant frequencies, which effectively supports the digital communication system (DCS 1.71-1.88 GHz), worldwide interoperability for microwave access (WiMAX 3.30-3.80 GHz), IMT advanced system or forth generation mobile communication system (3.40-4.2 GHz), and wireless local area network (WLAN 5.15-5.35 GHz). Manifestly, it has been found that the radiation patterns of the presented antenna are still similarly to the bidirectional radiation pattern at all operating frequencies. The properties of the antennas, for instance, return losses, radiation patterns and gain are determined via numerical simulation and measurement.Corresponding author: C. Mahatthanajatuphat (cmp@kmutnb.ac.th). 60Mahatthanajatuphat et al.

Abstract-In this paper, the design and measurement of a 3D-printed low-loss asymptotically single-mode hollow-core terahertz Bragg fiber is reported, operating across the frequency range from 0.246 to 0.276 THz. The HE11 mode is employed as it is the lowest loss propagating mode, with the electromagnetic field concentrated within the air core as a result of the photonic crystal bandgap behavior. The HE11 mode also has large loss discrimination compared to its main competing HE12 mode. This results in asymptotically single-mode operation of the Bragg fiber, which is verified by extensive simulations based on the actual fabricated Bragg fiber dimensions and measured material parameters. The measured average propagation loss of the Bragg fiber is lower than 5 dB/m over the frequency range from 0.246 to 0.276 THz, which is, to the best of our knowledge, the lowest loss asymptotically single-mode all-dielectric microstructured fiber yet reported in this frequency range, with a minimum loss of 3 dB/m at 0.265 THz.Index Terms-Bragg fiber, electromagnetic propagation, millimeter wave technology, photonic crystals, three-dimensional printing.

This article presents a bandwidth enhancing technique using a modified ground plane with diagonal edges, rectangular slot, and T-shape cut for the design of compact antennas. The proposed low-cost, compact-size circular patch antenna on 3 cm 5.1 cm printed circuit board (FR-4) is designed and validated through simulations and experiments. Results show that the T-shaped ground plane with the presence of the diagonal cuts at the top corners and the rectangular slots can increase the bandwidth. Return losses of 19 and 26 dB for the first and second resonant frequencies, respectively, can be achieved when the depth of the diagonal cut is 5 mm, the dimension of each rectangular slot is  mm, and the T-shaped size is  mm, providing a 28.67% wider bandwidth than FCC standard.

Abstract-This paper proposes a metamaterial reflective surface (MRS) as a superstrate for a single-feed circularly polarized microstrip patch antenna (SFCP-MPA). It illustrates a simultaneous enhancement on antenna gain, impedance bandwidth (ZBW) and axial-ratio bandwidth (ARBW) by adding the MRS atop the SFCP-MPA. The MRS can enhance the ZBW and ARBW by 3.5 and 9.9 times, respectively, compared to the circularly polarized patch source. Moreover, the gain of the CP-MPA with the MRS is 7 dB higher than that of the conventional CP-MPA. The small spacing between the MRS and patch source is another merit in the present design, which is as low as λ • /16, as it results in a low-profile antenna design that well suits modern wireless communications.

Cube Satellite (CubeSat) technology is an attractive emerging alternative to conventional satellites in radio astronomy, earth observation, weather forecasting, space research, and communications. Its size, however, poses a more challenging restriction on the circuitry and components as they are expected to be closely spaced and very power efficient. One of the main components that will require careful design for CubeSats is their antennas, as they are needed to be lightweight, small in size, and compact or deployable for larger antennas. This paper presents a review of antennas suitable for picosatellite applications. An overview of the applications of picosatellites will first be explained, prior to a discussion on their antenna requirements. Material and antenna topologies which have been used will be subsequently discussed prior to the presentation of several deployable configurations. Finally, a perspective and future research work on CubeSat antennas will be discussed in the conclusion.

In this paper, resin-based photocurable polymer materials for stereolithography, digitallight-processing (DLP), and polymer-jetting additive manufacturing techniques were characterized from 0.2 to 1.4 terahertz (THz) for their comprehensive dielectric properties, e.g., refractive index, absorption coefficient, dielectric constant, and loss tangent, by using laser-based THz time-domain spectroscopy. A total of 14 photocurable 3D-printing polymers were chosen, owing to their suitability, in terms of printing resolution, material characteristics, and so on, for millimeter-wave (mm-wave) and THz applications. The measurement results from 0.2 to 1.4THz, the dielectric constants of all photopolymer samples under test are between 2.00-3.10, while the loss tangents are from 0.008 to 0.102, which are quite useful for many applications, e.g., 3D printed antennas and THz transmission lines, which were demonstrated by an asymptotically quasi-single-mode Bragg fiber microfabricated by DLP micromanufacturing technique using HTM140-V2 photopolymer, which is previously reported at the nominal frequencies from 0.246 to 0.276 THz.

SUMMARYBandwidth and gain enhancement of microstrip patch antennas (MPAs) is proposed using reflective metasurface (RMS) as a superstrate. Two different types of the RMS, namely-the double split-ring resonator (DSR) and double closed-ring resonator (DCR) are separately investigated. The two antenna prototypes were manufactured, measured and compared. The experimental results confirm that the RMS loaded MPAs achieve high-gain as well as bandwidth improvement. The desinged antenna using the RMS as a superstrate has a high-gain of over 9.0 dBi and a wide impedance bandwidth of over 13%. The RMS is also utilized to achieve a thin antenna with a cavity height of 6 mm, which is equivalent to λ/21 at the center frequency of 2.45 GHz. At the same time, the cross polarization level and front-to-back ratio of these antennas are also examined.