1/17/2024 0 Comments Emc research bias![]() ![]() NTT Environment and Energy Systems Laboratories is taking up various challenges toward solutions of EMC problems. ![]() Accordingly, new EMC (electromagnetic compatibility) problems are arising with the development of this new communication technology, and research and development of technology for solving those problems is becoming more important. For that reason, the communication environment is becoming more complex, and at the same time the electromagnetic environment is also increasing in complexity. Thus, the communication environment is changing dramatically, and at the same time the circumstances surrounding communication systems are also changing greatly. Furthermore, rising concern about environmental problems is leading to the introduction of inverter technology and other such measures to reduce electric power consumption in homes. On the other hand, short-range wireless communication techniques have been developed toward the ubiquitous society, and technology that uses even higher frequency bands is appearing. For that purpose, various kinds of high-speed communication techniques that use metallic wires have been developed and the signals transmitted over them have higher and higher frequencies. That trend is bringing about the connection of various electrical and electronic devices known as household appliances to networks and the distribution of various kinds of data via the Internet. The proliferation of broadband services has made access to the Internet easy for ordinary households as well as businesses. Electromagnetic environment surrounding communications facilities You'll want to simulate this with the rest of your circuit to nail down the details and make final part selections.1. You may want to search out a lower-resistance coil to reduce the minimum impedance and increase the impedance at your 130 kHz rf frequency. Of course the impedance minimum is given by the series resistance. That was enough to broaden the response of this filter out to give relatively low impedance from 10 to 200 Hz. That leaves a shunt filter configuration:įrom a quick search I found a 10 mH inductor available at reasonable cost with 19 Ohm series resistance. The series filter solution is probably a bad idea because its inductor will need to be oversized to deal with your 4 A DC currents. So you need the filter to either act like an open in series with the inductor at resonance, or a short in parallel to prevent the interference signal from reaching the rest of the circuit. ![]() ![]() If the inductor picks up magentic signals, it will act like a current source. If you do have a problem, then stuff the components to add the filter. Initially, build the device without any filter, and measure the performance. I've never seen this in real life, but then again I've never worked with such a low rf frequency and the corresponding big inductor you'll need for the choke.īut I can at least make a suggestion: Add locations on board for a filter to catch the mains frequency in whatever location you'll install the circuit. You might be especially concerned about your choke inductor picking up magnetic fields from nearby mains wiring. Good rf design to suppress radiation will also give good susceptibility performance, so I won't say more about that. That said, maybe you're concerned about signals being picked up by your circuit and transmitting down the line to the connected equipment. The regulations on susceptibility generally say something like, "operation of your system should not be disrupted by conforming radiators in its environment." Since the circuit you're designing is composed entirely of passive components, its unlikely to be disrupted, even by quite strong nearby radiators. Your edited question asks about electromagnetic susceptibility. Unfortunately I can't really give you a rule of thumb for how much leakage is too much - only an idea about what issues you need to think about. Make sure you know what is the inter-winding capacitance for your inductor and make an estimate of how much rf will leak out before you proceed. The main way this can happen is through inter-winding capacitance of the choke inductor. I'd say the best way to reduce this risk is to be sure you won't leak rf power into the dc circuit. Mainly because that portion of the circuit is probably not designed so well to minimize EMI. On the other hand, if some of your RF leaks in to the DC portion of the circuit (in this case, basically the traces/wires back to the 24 V battery), then it you could have a problem. I'll assume that the RF portion of the circuit is laid out with the normal considerations for EMC in RF, and you're asking about any special considerations related to the fact this circuit is a bias-tee.Īn added DC voltage/current on an RF circuit doesn't add any particular extra EMC risks to the RF circuit. ![]()
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