Communication Systems and Electromagnetic Compatibility - Research Proposal Example

Communication Systems and Electromagnetic Compatibility Introduction Electromagnetic Compatibility (EMC) makes it necessary for systems and equipment to be able to endure certain level of interference, while not forming more than a specified level of disturbance (Redouté and Steyaert, 5). It is the capacity of a system to function adequately within an electromagnetic environment without generating excruciating electromagnetic disturbances to anything inside that environment, or be self-compatible. Every electromagnetic occurrence in the factory control room not connected to intend operation of the equipments is considered a disturbance emission. A key rule in fulfilling the criteria of an EMC directive in such a complex environment, involves dividing the extensive system into dissimilar sub-systems. Therefore, the electronic system can be separated into sub-systems, whereby each subsystem is handled independently. Each system will need different method and practices in designing so as to have a system which is in compliance with EMC directive. Discussion Safety Critical Systems The complexity of the manufacturing factory control room is due to the closeness of safety critical systems together with systems carrying out safety related roles, coupled with electromagnetic disturbances. The Electromagnetic interference, both intentional and deliberate can result in a wide range of problems, such as momentary trivial inconvenience, and system failures inside electronic and electrical equipments. In considering Electromagnetic interference risks, it may be necessary to bear in mind the structural factors within the control room concerning architecture, materials plus topography. This is because such factors play a considerable function in the protection plan. The disturbances are conducted via wiring or by induction through radiation. The identification as well as measurement of the sources will be crucial, since the nature of source determine which measures to take. Such measures include restricting disturbances generated on contactor through installing interference repressing RC unit in parallel with A.C. coil. Secondly, steering clear of cross-coupling and this is achieved by physically separating two highly incompatible components, or desensitizing potential fatalities through shielding (Montrose and Nakauchi, 3). Firstly, it is essential to identify all noise sources, and this should be performed as close as possible to the source and furthest from sensitive parts of the control room circuit. Given that most equipment s is used within close proximity and under nonexistence of EMC directives, there is an elevated chance that emissions from segments of such devices lead to escalating temperature (Tooley, 426). The best means of making certain that every noisy path has a return-path with small loops, is to add entire ground plane on the board. Since the circuit comprises digital plus analog circuits, ground plane should be divided into analog ground-plane as well as a digital ground-plane, so as to lessen interference involving analog and digital sections. System zoning can be used on single PCB, while noisy sections the system such as switch mode power-supply, needs to be completed as undersized as possible, in order to lessen volume of current loops which will be active as emitting antennas (Leferink, 3). Likewise, sensitive sections of system, such as analog-measurement circuit needs to be made small, in order to trim down size of current loops acting as receiving antennas. Noisy sections of system need to be placed as far away as possible from sensitive sections. For that reason, thermal management system needs to be activated more often, since the continuous transformation in heat plus thermal radiation can lead to a degraded performance of the arrangement. It is therefore necessary for noise transmitted and established on system inputs as well as on power cables to be dealt with (ATMEL, 8). Routing should be avoided on ground planes when trying to save space, unless systematic analysis reveals ground return-paths of other signals are not affected. Shield can be utilized since they are easier to apply. The shield can cover only the sections of the system which need it most, especially when zone system is applied during design, as it is unproblematic to decide which zones require shielding. Nevertheless, the shield needs to be completely closed particularly every line entering or departing from a particular zone should be filtered. This is because any single line which is not filtered, will operate similar to a solitary hole inside a bucket full of water, and will result in leak. However, semi-closed shield attached to ground can reduce noise, as it acts like a ground plane, thus minimizing loop antennas size (Ott, 70). Within system level, principal entrance plus exit points for unconnected electrical noise can be due to bare wire bundles that interconnect electrical equipment. In order to decrease intra-system, wire to wire noise cross-coupling, wire shielding together with shield termination is necessary. This entails separation, as well as routing through EMC grouping. This will cut off sensitive circuits from loud circuits physically through metallic shields, and as such, cross-coupling will be reduced. However, powerful enforcement of shield-termination needs to be part of the EMC plan, as this is normally sufficient to attain requisite safety margins when it comes to wire-to-wire coupled noises. Nevertheless, circuits acknowledged as EMC-critical, needs to be evaluated for any wire-to-wire coupling, pedestal on real physical routing of circuit wires. Evaluation should also involve frequency along with impedance distinctiveness of routed circuits, and as such, exact attention needs to be placed on circuits-sharing connectors. Characteristically, separation from shielding plus physical separation is reduced when circuits go through connectors jointly. The requirement for safety margins should be 6 dB or otherwise 20 dB when it comes to electro-explosive devices (Ott, 90). Such margin values are sufficient for systems safety as well as performance, and furthermore, they are technically attainable through familiarity with lots of systems. Another decision step is Function Implemented on the control room electrical circuits. This is because it will identify critical functions that are implemented via electrical circuits, with the objective being to classify a list of circuits which can be regarded as entrant EMC-critical circuits. Thus, any function that is established to be put into practice by simply mechanical means needs to be done away with from additional consideration. Critical functions that rely on electrical circuitry in some measure needs to be evaluated to resolve whether failure of circuit can result in function failing critically. Thus, when critical failure is propagated via the circuit, then the circuit is significant. Circuits which are impervious to EMI needs to be removed from additional consideration, such as power circuit which drive simple power relay, as they are probably affected by drift electromagnetic energy. Careful documentation must be done since some have integrated sensitive circuit controls, and as such, every candidate circuits need to be documented when deciding rationale for the EMC-critical reception or rejection. Since wire bundles can be active as antennas, they need to be evaluated for field to wire coupling. The procedure is generic, but not restricted in function to critical circuits. Still the approach should build on standard EMC system-level design observance including wire routing. However, this should be based on RF environment within the circuits, coupling towards circuit wiring and generic receptiveness of integrated circuit (ATMEL, 10). Control and Data Connectivity Issues Since wired and wireless communication components are linked via an internet protocol network, it brings out the danger of unintentional electromagnetic disturbances emitted from different forms of equipment in the control room. In this case, the sensitive sensors, transducers and camera streaming arrangement is not equipped with any retransmit-ask-for capabilities, that is why noise forced on the line is apparent as disturbances (Montrose and Nakauchi, 275). Given that there is the impact of electromagnetic waves escaping from power-line communication to amateur radio, or shortwave broadcasting, or even other wireless systems, then there needs to be clarity between EMC setting and service quality environment. This is adversely impacted by electromagnetic noise arising from electrical components linked to power line and low input-impedance tools. When low input-impedance appliances, are plugged into sockets near line communication, the current streams to lower impedance, while incoming signal streams to chargers. This then degrades data rate. In order to deal with EMC connected issues, EMC filters in form of common-mode filter are used to minimize the outcome of electromagnetic noise with connected low input-impedance appliance. This minimizes electromagnetic noise without attenuating communication signals. Blocking filter will help to reduce adverse interference from power-line communication signals picked from other buildings, as it is extremely compact (Fette and et al, 418). Wireless transmission of data with no cables can be done through generation of wireless-management data signals from management data and configured in such a way so as to be conveyed within frequencies corresponding to electromagnetic noise generated. This comprises a program, processor and a memory for storing. Thus, the processor should be receptive to computer-executable commands while the processor will get hold of management data, in addition to creating wireless-management data signals. Furthermore, other component to be incorporated includes routers, switches, or even servers intended for solitary use in the control room. In terms of data connectivity Tier IV Data management can be used, since it allows planned goings-on to be conducted without disruption. Its fault-tolerant functionality offers capacity to continue the system without load shock, even in the existence of unplanned failure. This is because it uses parallel power-distribution-paths having two UPS with N+1 redundancy. This compatibility with redundancy conception helps to attain reliability, ease of use, in addition to easy maintenance. Stand-alone Backup-to disk systems, such as virtual-tape library and network attacked storage, will remove redundant data from backups, in addition to giving high performance reduplication of data (EMC Corporation, 7). UPS Power System For off-line UPS, their load is powered straight from mains, with only the battery charge current going via the charger. Maximum interference phases, come about due to mains failure, in particular when every one of the load power goes via ac inverter. load often acquires power from inverter output in on-line UPS, and which is power-driven from mains-impelled rectifier, and when there is a mains breakdown, it is powered from a battery. Therefore, maximum interference phase should occur within the usual mode, especially when the inverter together with rectifier is functioning. The objective of EMC standards is to uphold a reasonable electromagnetic environment and as such, wiring in UPS should not be rerouted, and connector types should not be changed. When it comes to power system, one of the main sources of disturbance can be voltage, more than current transients. Thus, the voltages vary by let say hundreds of volts within a matter of nanoseconds, and this gives rise to dV/dts over and above 109 V/s (Tooley, 10). Rapid voltage shifts are sources of numerous disturbances, such as creation of currents flowing via stray capacitances. Thus, any stray capacitance can cause currents of more than a few hundred milliamperes, and such disturbance current flow via zero-reference conductor, which then modify signals, data or even commands. Furthermore, they can be superimposed within sensitive measurements, thus perturb other equipment through injection of disturbance into the distribution network. Therefore, one means of tackling this and ensure EMC compliance, involves minimizing common-mode currents by increasing common-mode impedance, in particular, when installing electronic power elements by leaving heat-sinks floating with no electric link. Also, this can be done through minimizing the stray capacitance involving the equipments and heat –sink, through utilizing an insulator having low dielectric-constant. In terms of UPS systems, the low-level electronics inside static inverter should be sheltered against disturbances formed by its power circuits (Lattarulo, 93). With the aim of increasing availability of power supply, the use of redundant components will be necessary, since such components supply requested task independently and this will not permit downtime or any interruptions. The redundant components should be autonomous of each other. The probable configurations of the electrical power distribution arrangement can be the dual-radial scheme. This comprises a combination of two sole radial systems that broaden from upstream towards downstream, but in union with each other. Furthermore, the duplication of such an arrangement components is expanded, in so far as individual user, or one or more of the distribution nodes. Thus, redundancy needs to be supplied when it comes to power components and the command plus control system. A backup power source is necessary when power supply scheme relies mainly on public distribution system. The essential feature of the IT components loads outfitted with switching power-supplies comprises current waveform plus phase. Given that such power supplies take up current nearer to utmost voltage, characteristic waveform away from being sinusoidal, it is rather an abridged base-line with vertex in association with voltage peak. A phase line is incessantly short-circuited to the ground, so as to finish a running. A solitary high-ohmic link is allowable and a useful EMC filter sets up such a connection to ground because of Y capacitors (Lattarulo, 94). Also, implementation of a solitary RCD upstream in a static system helps to protect against circuitous contact, in addition to guaranteeing incessant power to every loads when a component trips, especially load impacted by fault division of electrical circuits. Separating energy sources will help to shun interference in sensitive components arising from conducted disturbances from other systems linked to similar power source. The rationale is to form two distinct power sources that are secluded by impedances, and which are elevated within frequency of disturbances. Individual components, such as inductors, or capacitors should have RF distinctiveness specified by defining impedance as a function of frequency. EMC filters and components should have utmost line voltage such that VN +10% should not be exceeded, however, small voltage surges are allowed ( Tooley, 10). System Design Issues Given that the electronic circuit contains signals which adjust in levels, it tends to radiate some power since interconnections and the wires behave as radiating antennas, though short they are. Moreover, the circuits tend to pick up radiated signals from any other transmitter whether sources are conveyed intentionally or not. Thus, Electromagnetic Interference issues can halt adjacent segments of electronics equipment functioning alongside each other. The main area which needs to be considered in ensuring EMC compliance is RF radiated emissions which comes about from the connecting cables, as they are susceptible to picking up interference. They create most significant coupling path in terms of interference, as these cables carry elevated frequency signals and data (Gonschorek and Vick, 5). The cable seems to pick and radiate signals, when they reach quarter wavelength, and as such, they form a resonant circuit, and electromagnetic compatibility can be an issue. A key alternative is to filter the cables coming in and departing from the unit, while considering that a careful balance needs to be maintained involving the filter between equipment performance and electromagnetic-compatibility requirements. This will not only help to minimize the level of EMI, but also enhance the performance of circuit, since high speed data is carried and any sharp edges will not be easily eliminated by filters. Moreover, the signal will not be attenuated to levels which can make the system not to work, as the signal can be transmitted in differential format. Signal cables should be made as twisted pairs and screened, so that elevated frequency signal can be transmitted, in addition to reducing its vulnerability to radiation or reception (ATMEL, 10). Another option is to introduce EMC filters especially for those lines transmitting low frequency signals. Hence, power input cables which convey status voltages will be useful for filtering, as the EMC filters will eliminate any elevated frequency components, while leaving low frequency components on lines which will not radiate considerably. Notably, EMC filters need to be positioned on entry points and tightly bonded to unit chassis, so that no signal is able to enter or radiate into it before being eliminated by filter (Montrose and Nakauchi, 10). Circuit partitioning circuit designing, will be critical in making certain that circuit passes EMC test. This needs to be done during the earliest phases of designing, given that it administers the entire topology of circuit plus mechanical construction. The initial phase of partitioning procedure involves partitioning the circuit to an EMC critical plus non-critical field. Electromagnetic compatibility critical fields will be those which are susceptible to radiation or sources of radiation, and they comprise circuits comprising elevated frequency circuitry, high-speed logic, such as microprocessor circuits, together with low-level analogue circuits. Non-critical EMC fields should contain regions which are not going to easily radiate signals, or otherwise be vulnerable to radiation. Hence, they comprise circuits with linear power-supplies, but not switch-mode power sources or slow-speed circuits. Therefore, critical and sensitive areas needs to be screened and filtered within the interfaces, so as to halt EMI from being radiated, in addition to safeguarding the circuits from actions of EMI (Ott, 20). Thus, by isolating EMC critical regions, it is easier place relevant measures during initial phase of design. The interface offers the likelihood for maximizing entire performance in order to fulfill EMC test and even facilitate cost reductions. Cables should be screened, in order to thwart any radiation of signals from being picked up by external signals. Since the cables are required for electromagnetic compatibility applications, then the screen should be bonded to the ground to equipment signal when they enter the unit. If not, redundant signals can be radiated, thus compromising EMC compliance. A common basis for EMC issues under microcontroller equipments is power supply not being good enough. Thus, accurate and adequate decoupling of power lines is very essential for steady microcontroller performance, and in minimizing emitted noise from such devices. In particular, digital circuits have supply current of average value, as the current is being drawn in incredibly smaller spikes on clock edges, and when I/O lines are switching the spikes becomes even higher. That is why current pulses inside power supply lines attain several hundred mA when all I/O lines within I/O port adjusts value simultaneously, and when I/O lines are not weighed down, this pulse can attain a small amount of ns, and which cannot be conveyed over extended power supply lines. The major source should be decoupling capacitor (Lattarulo, 95) Conclusion EMC design risk assessment technique allows a quantified technical appraisal of design changes when it comes to compliance status. EMC problem solving procedure entails troubleshooting as a critical aspect, and this entails gathering and evaluating present system information. Secondly, there should be preliminary diagnosis, since majority of elevated frequency issues are linked emission, invulnerability and self-compatibility. Thus, a ground-return plane is to be applied given that wires along with traces possess high impedance. It is important to design the entire system into zones or else sub-systems, in order to come up with ground cabling, towards eliminating the possibility that emissions arising from one sub-system upset another sub-system. Thus, current needs to be diverted rear to shielded field or blocked with elevated impedance. Also, there needs to be appropriate shielding integrity for the UPS, sensitive sensors, computers and transducers. Therefore, appropriate shielding tests needs to be applied, so as to prevail over poor shielding reliability through assessing and measuring crystal-oscillator harmonics, considering that switching appliances can give out radiations such as ESD or LCD emissions. Moreover, cross talk is happening due to self-compatibility issues from noisy-source current, and this can be avoided by not allowing them to be placed closely to sensitive sensors, transducers or thermal management structures. Thus, emissions, power-disturbances, as well as cross talk can be avoided by controlling current path through RF immunity careful cabling. Works Cited ATMEL. "AVR040: EMC Design Considerations." 2011. 4 December 2012 . EMC Corporation. "Data Domain For EMc Networker." 2012. 4 December 2012 . Fette, Bruce A and et al. RF & Wireless Technologies: Know It All: Know It All. Newnes, 2007. Gonschorek, Karl-Heinz and Ralf Vick. Electromagnetic Compatibility for Device Design and System Integration. Springer, 2009. Lattarulo, Francesco. Electromagnetic Compatibility in Power Systems. Elsevier, 2006. Leferink, Frank. "Gaps in the Application of the EMC Directive Due to Inadequate Harmonized Product Standards." 2010. 4 December 2012 . Montrose, Mark I and Edward M Nakauchi. Testing for EMC Compliance: Approaches and Techniques. John Wiley & Sons, 2004. Ott, Henry W. Electromagnetic Compatibility Engineering. John Wiley & Sons, 2011. Redouté, Jean-Michel and Michiel Steyaert. EMC of Analog Integrated Circuits. Springer, 2010. Tooley, Michael. Electronic Circuits: Fundamentals and Applications. New York: Routledge, 2006. Tooley, Mike. Design Engineering Manual. Elsevier, 2009. Read More