An Unpowered Sensor Node for Real-Time Water Quality Assessment (Humic Acid Detection)

A zero-power microwave sensor is reported for the real-time assessment of water quality. The proposed structure is able to transmit sensed data directly to a base-station without additional data processing at the wireless sensor node (WSN) which results in less power consumption. The base-station propagates a single tone signal at the frequency of f0/2. At the sensing node, an antenna absorbs that signal and a passive frequency doubler makes its frequency twice, i.e., f0, which will be used as the carrier signal. Two pairs of open-ended coaxial probes are used as liquid sensors; one inside a known reference sample and the other one inside the water under test. A combination of both sensors’ data will be sent to the base-station. A special six-port structure is used for modulation of sensed data over the carrier. At the base-station, a receiver will demodulate the received signal for extracting the sensed data. As an example, the system has been evaluated at f0 = 2.45 GHz for the detection of Humic-Acid levels as a common contaminant of river waters

A Survey on Battery-Less RFID-Based Wireless Sensors

We present a survey on battery-less Radio Frequency Identification (RFID-based wireless sensors that have emerged in the past several years. We discuss the evolution of RFID turning into wireless sensors. Moreover, we talk about different components of these battery-less RFID-based wireless sensors, five main topologies that transform a simple RFID chip into a battery-less wireless sensor, and state-of-the-art implementations of these topologies. In battery-less wireless sensors, the read range is of key importance. Hence, we discuss how each component of the sensor plays its role in determining the read range and how each topology exploits these components to optimize read range, complexity, and/or cost. Additionally, we discuss potential future directions that can help provide improvements in RFID-based wireless sensor technology

Miniaturized Antipodal Vivaldi Antenna with Improved Bandwidth Using Exponential Strip Arms

In this paper, a miniaturized ultra-wideband antipodal tapered slot antenna with exponential strip arms is presented. Two exponential arms with designed equations are optimized to reduce the lower edge cut-off frequency of the impedance bandwidth from 1480 MHz to 720 MHz, resulting in antenna miniaturization by 51%. This approach also improves antenna bandwidth without compromising the radiation characteristics. The dimension of the proposed antenna structure including the feeding line and transition is 158 × 125 × 1 mm3. The results show that a peak gain more than 1 dBi is achieved all over the impedance bandwidth (0.72–17 GHz), which is an improvement to what have been reported for antipodal tapered slot and Vivaldi antennas with similar size

A single feed dual-band circularly polarized millimeter-wave antenna for 5G communication

In this paper, one simple dual-band (28 and 38 GHz) circularly polarized slotted patch antenna, suitable for future millimeter wave mobile communication, is presented. The proposed monolayer circularly polarized patch antenna is considered without any 90\ub0 phase shifter and is excited by a single-feed microstrip line, which is very desirable for high gain antenna array implementation in millimeter wave band in order to compensate the link loss. From EM simulation, it has been found that the dimensions of the L-shaped slots significantly affect the performance of the antenna. The antenna has been prototyped and the measured results show that the antenna can simultaneously provide circular polarization in the two suggested millimeter-wave bands for the upcoming 5G mobile communications

Fence Shaping of Substrate Integrated Fan-Beam Electric Dipole for High-Band 5G

This work presents fence shaping for dipole antenna operating at 5G high-band frequencies. A via fence is employed around the dipole to suppress back radiation. By varying the geometric shape of the fence, the dipole’s radiation characteristics can be controlled, which adds an additional degree of freedom to the design. This was investigated by studying different fence shapes, namely rectangular-, U-, and V-shaped fences. The wide bandwidth (higher than 6.5 GHz) centered around 28 GHz, and the stable radiation performance from 24 GHz to 32 GHz made the proposed structure capable of supporting multiple 5G frequency bands and the fence shaping help modulate the gain and HPBW of the dipole. All fabricated prototypes attained front-to-back radiation ratio (F/B) higher than 36 dB, with good gain/HPBW performances of 14.1 dBi/103.7°, 13.5dBi/118°, and 12.6 dBi/133° from the V-fence, U-fence, and rectangular fence 4 × 1 arrays, respectively

Dual-Band/Dual-Mode Rat-Race/Branch-Line Coupler Using Split Ring Resonators

A novel dual-band/dual-mode compact hybrid coupler which acts as a dual-band branch-line coupler at the lower band and as a rat-race coupler at the higher band is presented in this paper. One of the most interesting features of the proposed structure is that outputs of the proposed coupler in each mode of operation are on the same side. This unique design is implemented using artificial transmission lines (ATLs) based on open split ring resonators (OSRR). The low-cost miniaturized coupler could be operated as a dual-band 90° branch-line coupler at 3.3 and 3.85 GHz and 180° rat-race coupler at 5.3 GHz. The proposed coupler could be utilized in the antenna array feeding circuit to form the antenna beam. The structure’s analytical circuit design based on its equivalent circuit model is provided and verified by measurement results