Integrated impedance-matching coupler for smart building and other power-line communications applications

Abstract: Power-line communications is a promising technology to help automate buildings, as it utilizes the in-situ power cabling as a communications channel. However, couplers are required to inject and extract the communication signal from the power grid. Most power-line communications couplers make use of a small transformer to adapt impedance levels while also providing galvanic isolation. The cost and size of these transformers have been hindrances in the quest for compact, economic couplers. Previous attempts to eliminate this coupling transformer, while maintaining impedance adaptation, have not been successful in reducing component cost nor physical size. In this paper, a novel approach is followed: (1) a suitable dualfunction band-pass matching circuit is designed as for ordinary electronics, whereafter (2) the specifications of this band-pass matching circuit is upgraded to function safely in the power-grid environment as a coupler. Therefore a matching circuit is transformed into a compact power-line coupler, which further exhibits band-pass filtering and excellent impedance-adapting performance. Simulations as well as laboratory measurements are shown which confirm the accuracy of the design. Finally, practical 220-V measurements in an office block are presented, which prove the versatility of this novel coupler when power-grid conditions fluctuate

A novel PLC impedance conditioning technique for quasi-common mode power-line antenna injection

Preethichandra, DM ORCiD: 0000-0001-6802-2212In recent years, there has been a growing interest in the utilisation of in-situ power cabling for its antenna properties. Common-mode injection of signals further holds promise to facilitate effective low-power radiation from powerline antennas (PLAs) throughout a building. However, common-mode power-line communication (PLC) injection is illegal in many countries, for fears of interfering with the residual current device (RCD) protection. This paper reports on a novel impedance conditioning technique which makes use of a mains-rated 'Y-cap' and resistor to balance impedance levels in the Live and Earth conductors for improved PLC injection. The technique further improves power-line radiation by facilitating the flow of PLC current through the earth wire - in line with regulations. In general, earth return paths are asymmetrical to the other conductors and improved radiation is thus obtained when currents return through earth. Simulation results as well as experimental results are presented which confirm improved PLC injection as well as quasi-common mode earth current. © 2018 IEEE

Is resistive coupling feasible for the reception of power-line communications data?

Historically, two classes of coupling circuits have been used for power-line communications (PLC), being capacitive couplers and inductive couplers. In this paper, resistive coupling as a radical and novel approach is investigated specifically for the reception of PLC data. The main goal of this new approach, is to reduce costs associated with traditional capacitive and inductive couplers, seeing that resistors are the cheapest electronic components available. Only two resistors are required to implement a voltage-divider setup which reduces the harmful ac power waveform to a safe level, after which (cheaper) low-spec components can be used to filter and process the scaled down,sampled waveform. Simulation results as well as off-line and live experimental results are shown to confirm that the superimposed PLC signal can be extracted successfully with resistive PLC coupling

A preliminary investigation of the UHF properties of LV cable for WiFi over power line communications

In pursuit of a wireless (contactless) power line communications (W-PLC) system for low voltage (LV) power distribution networks, a commonly utilized bundled low voltage electrical cable called Cabtyre, was energized with a range of frequencies up to 3 GHz. The intention was to characterize the cable from a radio frequency radiation perspective for the utilization of standard low voltage distribution cables as antennas in ultra high frequency (UHF) PLC systems. The range of test frequencies extends 550 MHz beyond the present IEEE 802.11g protocol which has a centre frequency of 2.45 GHz and a 80 MHz total bandwidth. The applied tests therefore allow adequately for the maximum bandwidth required with 40 MHz modulation on either side of the 2.45 GHz centre frequency, [1]

An electrothermally actuated MEMS braille dot

Albermani, F ORCiD: 0000-0001-8540-1724; Preethichandra, DM ORCiD: 0000-0001-6802-2212; Sul, J ORCiD: 0000-0003-0982-0921With some recent attempts on development of micro tactile displays, the realization of portable Braille is becoming more feasible. Such tactile displays can help visually impaired individuals to read and comprehend patterns by using the sense of touch. The current proposed designs for such tactile displays mainly use fluid expansion to enhance the out of plane displacements of the Braille dots. These methods render some challenge in terms of fabrication and size. In this work, we propose a design based on electrothermal actuation of a micro Braille dot. The ultimate goal of the research is to work towards a wearable system that can be connected to a computer for reading text files. The proposed design can generate out of plane displacements of 250 µm at a 58 ℃ rise from ambient. The dot can be actuated by low input voltage of 1.36 V and can apply a force of 5 mN. Physical displacement and temperature can reinforce a valid dot detection

A preliminary investigation of the UHF properties of LV cable for WiFi over power line communications

In pursuit of a wireless (contactless) power line communications (W-PLC) system for low voltage (LV) power distribution networks, a commonly utilized bundled low voltage electrical cable called Cabtyre, was energized with a range of frequencies up to 3 GHz. The intention was to characterize the cable from a radio frequency radiation perspective for the utilization of standard low voltage distribution cables as antennas in ultra high frequency (UHF) PLC systems. The range of test frequencies extends 550 MHz beyond the present IEEE 802.11g protocol which has a centre frequency of 2.45 GHz and a 80 MHz total bandwidth. The applied tests therefore allow adequately for the maximum bandwidth required with 40 MHz modulation on either side of the 2.45 GHz centre frequency, [1]

FHIT RNA and protein expression in oral squamous cell carcinomas

BACKGROUND: To investigate the possible role of FHIT, a possible tumour suppressor gene, in oral carcinogenesis, we examined 17 oral squamous cell carcinomas (OSCCs) for genetic alterations. MATERIALS AND METHODS: Fresh tissue was obtained during surgery, snap-frozen in liquid nitrogen and stored at -70 degrees C. Nested PCR amplification to examine the integrity of FHIT mRNA was performed on the reverse transcribed complementary DNA obtained from the frozen normal and tumour tissue. Immunohistochemistry was done on formal in-fixed paraffin-embedded tissue protein from the same cases using a polyclonal antiserum against the full length FHIT. RESULTS: Twelve out of 17 (71%) OSCCs showed reduced or absent FHIT protein and half of the cases with reduced FHIT protein exhibited aberrant RT-PCR products. CONCLUSION: Immunohistochemical detection of FHIT protein expression in OSCCs is the more sensitive method to determine the status of FHIT in these tumours, in agreement with previous studies of other tumour types.This article was co-written by Prof Janse van Rensburg before she joined the University of Pretoria