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Precast segmental bridge construction in seismic zones
Published in Fabio Biondini, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Resilience and Sustainability, 2012
Fabio Biondini, Dan M. Frangopol
A folded patch antenna, as part of the RFID tag, is designed to function as a wireless strain sensor (Yi et al. 2011a). Fig. 2 shows the design drawing and a photo of the manufactured tag. To provide good radiation performance on metallic structures, a patch form is adopted for the antenna. Furthermore, the patch antenna is folded to reduce overall footprint. Vias are used to connect the top copper layer with bottom copper layer (i.e. ground plane) to achieve the “folding”. The substrate sandwiched between the top and bottom copper layers is made of Rogers RT/duroid®5880 material, a glass microfiber reinforced poly-tetra-fluoro-ethylene (PTFE) composite. The substrate thickness is 31 mils. The adopted RFID chip is the SL3ICS1002 model from NXP Semiconductors. Excluding soldering pads, physical size of the RFID chip is about 1mmx1mm, as shown in Fig. 2(b). The chip impedance is 13.3-/122 Q (“j” is the imaginary unit) at 915 MHz, which is low and relatively easy to match during the tag antenna design. Meanwhile, impedance of the tag antenna can be tuned by adjusting the dimensions of the antenna design. When the impedance of the RFID chip equals the complex conjugate of the antenna impedance, the tag is matched and reaches its resonance frequency. The resonance frequency, fR0, of the antenna can be estimated as:
High-Performance Analog Circuits
Published in Wai-Kai Chen, Analog and VLSI Circuits, 2018
Chris Toumazou, Alison Payne, John Lidgey, Alicja Konczakowska, Bogdan M. Wilamowski
Ground planes. The purpose of a ground plane is to provide a low-impedance path for currents flowing to ground, since any series impedance in the ground connections will mean that not all ground nodes are at the same potential. In addition, the inductance of a printed circuit track is approximately inversely proportional to the track width, and so the use of thin tracks can result in inductive ground loops, leading to ringing or even oscillations. The use of an unbroken ground plane on one side of the circuit board can minimize the likelihood of inductive loops within the circuit. However, any particularly sensitive ground-connected nodes in the circuit should be grounded as physically close together as is possible.
Shielding and Grounding
Published in Christos Christopoulos, Principles and Techniques of Electromagnetic Compatibility, 2022
This situation is typically encountered in data processing rooms with several physically separate but interconnected units. Mains connection is to different wall-mounted sockets, sometimes supplied by different power phases, whereas these different units are interconnected via data cables. It is difficult in this environment to maintain any kind of control of grounding arrangements. It is recommended that ground potential variations between communicating devices should not exceed 0.25 V.32 It is difficult to ensure this, especially if lightning currents are induced into the facility. The general grounding principles already discussed still apply, although changes to the working environment are necessary. Ideally, the equivalent of a ground plane should be established to provide a low-impedance path for grounding currents. Depending on the nature and extent of the installation, this plane could be the floor and or work bench and may involve already existing structural parts of the building, e.g., steel reinforcement bars. Equipment cabinets and any conducting penetrations, such as pipe work, should be bonded by the shortest possible route to the ground plane. Any external connections such as power and data cables should preferably be brought into a single distribution location and their respective ground connections bonded to the ground plane. Filtering and nonlinear protective devices may also be connected at this location to suppress external overvoltages and equalize ground potential fluctuations on various incoming connections. The objective must be to avoid making connections to equipment from outlets of an uncertain ground potential. Although difficulties may still arise, it is important that a well-thought-out grounding methodology exists and that it is documented and explained to all personnel likely to interfere with these arrangements. This applies not only to electrical contractors but also those responsible for other building services.
Design, development and characterization of wide incidence angle and polarization insensitive metasurface absorber based on resistive-ink for X and Ku band RCS reduction
Published in Waves in Random and Complex Media, 2021
Priyanka Tiwari, Surya Kumar Pathak, V. P. Anitha
The geometry of the proposed unit cell for absorbing structure along with the direction of the electric field, magnetic field and direction of propagation of Electromagnetic (EM) wave has been illustrated in Figure 1. A periodic pattern of resistive ink has been deposited on the top of the FR-4 dielectric substrate (ϵr = 4.3 and tan δ = 0.025) with thickness (td) 0.2 mm. Optimized dimensions of proposed unit cell are p = 10.6 mm, a = 8.25 mm, w = 1 mm and c = 2.54 mm. Surface resistance has been chosen as Rs = 70 Ω/sq for top resistive ink pattern. Air spacer with thickness (ta) 5 mm has been incorporated in-between FR-4 dielectric substrate deposited with resistive ink and metallic ground plane. Copper has been used for the metallic ground plane with thickness (tm) 0.035 mm and conductivity of 5.8 × 107 S/m.
A triple band rectenna for RF energy harvesting in smart city applications
Published in International Journal of Electronics, 2023
Daasari Surender, Ahsan Halimi, Taimoor Khan, Fazal A. Talukdar, Yahia M.M. Antar
The ground plane acts as a reflecting surface for EM radiation, which helps in increasing the radiation in one direction by blocking it in the reverse direction. With the support of this phenomenon, analysis has been made on the behaviour of the antenna with different ground planes (G), and the corresponding results are shown in Figure 5. From observations that have been made on the gain, the number of resonances, and their corresponding reflection coefficients. An improvement in the reflection coefficient is observed at various resonances with an increase in ‘G’ from 52 mm to 56 mm but suffers from low gain. It is noted that the enhancement in both reflection coefficient and gain is observed by increasing ‘G’ from 56 mm to 58 mm.
Design and development of T-Shaped antenna structure for wireless communication
Published in Waves in Random and Complex Media, 2022
Figure 5 displays the charts of realized gain and radiation efficiency together. The suggested 4G LTE antenna is a conformal, electrically compact, and has a reasonably good gain, VSWR and reflection coefficient, as shown in Table 3. The geometry is 8.22 mm × 4.46 mm with a dielectric constant of 4.2 and a loss tangent of 0.0058 mm on an FR-4 epoxy substrate. The ground plane is formed of conducting material, such as copper, and is fed via a microstrip transmission line. The patch has a width and length of 8.22 mm × 4.46 mm, with two rectangular slots of 0.4 mm × 2.8 mm and a square feed slot of 0.4 mm × 0.6 mm to increase resonance.