Abstract-This paper presents the analysis and design of a two-probe excited circular ring antenna. The analysis is conducted by using induced emf method and transmission line model. The design process is to choose a suitable radius of the ring for a single probe antenna. Then, the suitable probe length and ring length are determined for the twoprobe antenna. Finally, isolation between the two probes is enhanced by insertion of an inductor coil between the probes. The operational characteristics of the prototype antenna at the frequency of 5.2 GHz are measured and compared with calculation results. It is evident that these results are in good agreement. The antenna achieved isolation in excess of 20 dB and VSWR less than 2 : 1 over the desired bandwidth and a bidirectional radiation pattern with 4 dBi gain. This antenna is suitable for Multiple-Input Multiple-Output (MIMO) system covering a long and narrow environment.
This research has proposed a dual polarized suspended square plate rectenna for RF-to-DC conversion at the 2.40-2.50 GHz frequency band. The proposed dual polarized antenna yields improved isolation with an annular rectangular ring slot etched in the square radiating plate. The proposed antenna could achieve >40.00 dB isolation and >8.00 dBi gain with unidirectional radiation. The proposed SMS7630-based rectifying circuits were measured and could realize the maximum conversion efficiency of 25.98% (1.57 V) with a 3.00 kX resistor and 2.00 mW input RF power of a signal generator. On integration, the experimental vertical polarization rectenna was capable of achieving the maximum conversion efficiency of 21.86% (14.20 mV) at the 0.5 m distance and 0.00015.00 mW/cm 2 input power density. The proposed dual polarized rectenna can receive the input RF power density of arbitrary polarization with obtained average conversion efficiency of 14.97% (10.50 mV) at the 0.5 m distance of wireless local area network (WLAN) system. V C 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:164-173, 2016.
This research presents a frequency reconfigurable antenna scheme for wireless communications [worldwide interoperability for microwave access (WiMAX), mobile WiMAX and wireless local area network], in which a PIN diode is utilised for the discrete tuning and a varactor diode for the subsequent fine‐tuning. A microcontroller‐controlled embedded biasing network (EBN) is integrated into the antenna to regulate the PIN and varactor diodes for the simultaneous wideband and multiband operations. Specifically, two clusters constitute the proposed antenna scheme: the antenna and EBN clusters. The simulation and experimental results revealed that the antenna scheme could achieve the multiple frequency bands in the range of 2.4–5.8 GHz, with negligible changes in the antenna physical dimensions. Due to its compactness, the antenna scheme is ideal for small modern wireless communications devices.
This research proposes a system board of integrated antenna scheme of near-field communication (NFC) and dual band ultra-high frequency (UHF, 920-925 MHz)/2.45 GHz radio frequency identification (RFID) reader antennas for Internet of Things (IoT) applications. The integrated antenna scheme is capable of simultaneous execution of NFC and UHF RFID functions whereby the NFC and UHF RFID modules, which are serially connected to a microcontroller with Wi-Fi module (NodeMCU), read the universal identification (UID) of NFC and UHF RFID tags. The data are then forwarded to a cloud server via Internet of Things (IoT) and are viewable on smartphones using Blynk mobile application via IoT. To realize the optimal antenna design, simulations were carried out using CST Studio Suite. Prototype antennas were subsequently fabricated and integrated into the system board for IoT-linked near-and farfield communication. The simulation and measured results are in good agreement. The NFC reader antenna resonates at 13.56 MHz, and the dual band UHF/2.45 GHz RFID reader antenna achieves the 920-925 MHz and microwave (MW) bands with high isolation. The novelty of the proposed integrated NFC and UHF RFID antenna scheme lies in the use of cloud technology to store real-time and archival data, in place of traditional servers. The integrated antenna scheme could achieve the NFC, UHF, and MW frequency bands, rendering it ideal for IoT applications.INDEX TERMS Near field communication (NFC), radio frequency identification (RFID), NFC antenna, ultra-high frequency (UHF) reader antenna, dual band antenna, Internet of Things (IoT).
This research proposed an S-shaped metasurface (MTS)-based wideband circularly polarized (CP) patch antenna for C-band uplink frequency spectrum. The proposed MTS-based CP patch antenna was of low profile and fabricated on three substrate layers: upper, middle, and lower. The upper substrate contained 4 × 4 periodic S-shaped MTS elements, the middle substrate functioned as ground plane with a rectangular-shaped slot at the center, and the lower substrate contained a coplanar waveguide with microstrip and ground. The S-shaped MTS elements converted linearly polarized (LP) into CP wave. Simulations were performed, and an antenna prototype was fabricated and experiments carried out. The measured impedance bandwidth and axial ratio bandwidth (ARBW) at the center frequency of 5.9 GHz were 43.22% (4.05 -6.6 GHz) and 22% (5.3 -6.6 GHz), respectively, rendering the proposed antenna suitable for satellite communication applications. The proposed antenna achieved the maximum gain of 6.16 dBic at 5.6 GHz. The novelty of this research lies in the use of S-shaped MTS elements to efficiently convert LP into CP wave and achieve wider ARBW for the C-band uplink spectrum.
This research presents a triband compact printed antenna for WLAN and WiMAX applications. The antenna structure consists of a folded open stub, long and short L-shaped strips, and asymmetric trapezoid ground plane. Besides, it is of simple structure and operable in 2.4 GHz and 5 GHz (5.2/5.8 GHz) WLAN and 3.5/5.5 GHz WiMAX bands. The folded open stub and long and short L-shaped strips realize impedance matching at 2.4, 3.5, 5.2, and 5.8 GHz, and the asymmetric trapezoid ground plane fine-tunes impedance matching at 5.2, 5.5, and 5.8 GHz. In addition, the equivalent circuit model consolidated into lumped elements is also presented to explain its impedance matching characteristics. In this study, simulations were carried out, and a prototype antenna was fabricated and experimented. The simulation and experimental results are in good agreement. Specifically, the simulated and experimental radiation patterns are omnidirectional at 2.4, 3.5, and 5.2 GHz and near-omnidirectional at 5.5 and 5.8 GHz. Furthermore, the simulated and measured antenna gains are 1.269–3.074 dBi and 1.10–2.80 dBi, respectively. Essentially, the triband compact printed antenna covers 2.4 GHz and 5 GHz (5.2/5.8 GHz) WLAN and 3.5/5.5 GHz WiMAX frequency bands and thereby is a good candidate for WLAN/WiMAX applications.
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