Electromagnetic Interference

In summary, you can usually reduce the interference of 60Hz on 1MHz by using simple signal frequency discrimination.
  • #1
Michael Lin
11
0
Dear all,
If I have a strong magnetic field present (an oscillating field at say 60Hz), how can I eliminate its interference effect on a neighboring circuitry that has a transmitter operating at say 1 MHz? Would simple filtering at the receiver be enough? I just want to check the feasibility of a functional transmitter without getting into using magnetic shielding.

Thanks,
Mike
 
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  • #2
Well because 60Hz is so different than 1MHz you could
often use simple signal frequency based discrimination
to reduce the interference of the 60Hz on the 1MHz.

the frequency ratio is 1.66*10^4, or 14 octaves,
so even a 6dB/octave roll-off filter would give
6*14 = 84dB of rejection of 60Hz relative to a cut-off
frequency of 1MHz.

The interesting question is to ask HOW AND WHY the
60Hz couples into the transmitter circuitry.

One way would involve the 60Hz ripple appearing as
a differential signal on the power supply leads of
circuitry in the transmitter. In that case you'd look at
how well the differential 60Hz power supply signal variance
is amplified or attenuated by your transmitter circuitry.
This kind of power supply ripple noise based interference
is commonly due to inadequate filtration of 60Hz variance
in a linear 60 Hz mains operated power supply.

Another way 60Hz interference can form is magnetic
field coupling from the magnetic field of a wire or
coil / transformer carrying 60Hz signals through mutual
inductance with wires, coils, transformers that carry
other signals. Using geometric means of distancing and
orienting the circuits to minimize their mutual inductance
can be helpful. Using thick high permeability magnetic
materials to enclose the 60Hz noise inductors and/or
the susceptable inductors that can pick up the noise
can help.

Electric field pickup can happen if there were 60Hz
voltage sources that capacitively coupled to parts of
the sensitive circuit, but this is usually less dominant of
a mechanism than others.

Finally, common mode coupling can occur where a
common mode 60Hz noise voltage can appear on
your equipment or various cables running into the
equipment. Generally devices are insensitive to common
mode voltages, but the common mode noise present can
be turned into differential (unbalanced) noise by any
unbalance of part of the circuit so that a differential
noise voltage or current can be present between the
common mode potential and Earth or whatever.

Usually it's best to design the system so that it has both
low EMI generation capability as well as low EMI
noise susceptability for whatever EMI is present in
the environmental space, in the power supply, coupled
in through cables/wires/signals, et. al.
 
  • #3


I understand your concern about electromagnetic interference and the potential impact it can have on circuits and transmissions. In order to eliminate the interference effect of a strong magnetic field on a neighboring circuitry, there are a few steps that can be taken.

Firstly, it is important to analyze the source of the magnetic field and determine if there are any ways to reduce its strength or alter its frequency. For example, if the magnetic field is being produced by an electrical device, it may be possible to shield the device or use alternative materials to reduce the field's strength.

In terms of the neighboring circuitry, filtering at the receiver can certainly help to reduce the interference, but it may not completely eliminate it. It is also important to consider the design and layout of the circuitry to minimize the effects of the magnetic field. This can include using twisted pair wiring, proper grounding techniques, and avoiding placing sensitive components near the source of the interference.

If these measures are not enough, magnetic shielding may be necessary. This involves using materials that can redirect or absorb the magnetic field, preventing it from reaching the neighboring circuitry. While this may seem like a complicated solution, there are many companies that specialize in creating custom magnetic shielding solutions for various industries.

In conclusion, while simple filtering at the receiver may help to reduce electromagnetic interference, it may not be enough to completely eliminate it. It is important to consider all possible solutions, such as altering the source of the magnetic field or implementing shielding techniques, in order to ensure the successful operation of your transmitter.
 

1. What is electromagnetic interference (EMI)?

Electromagnetic interference (EMI) is the disruption of electronic devices or systems caused by electromagnetic radiation or induction from external sources. This interference can affect the performance of electronic devices and can lead to errors or malfunctions.

2. What are the sources of electromagnetic interference?

EMI can come from a variety of sources, including power lines, electronic devices, radio waves, and lightning strikes. It can also be caused by natural phenomena, such as solar flares or geomagnetic storms.

3. How does electromagnetic interference affect electronic devices?

EMI can affect electronic devices in a number of ways. It can cause disruptions in communication signals, data loss, or even damage to the device itself. In extreme cases, EMI can lead to complete system failure.

4. How can electromagnetic interference be prevented?

There are several methods for preventing EMI, including shielding electronic devices, using filters or ferrite beads on cables and wires, and implementing grounding techniques. It is also important to ensure that electronic devices are properly designed and constructed to minimize their susceptibility to EMI.

5. How is electromagnetic interference measured?

EMI is typically measured using specialized equipment, such as spectrum analyzers, which detect and analyze electromagnetic radiation in a specific frequency range. The measurement of EMI is important in identifying potential sources of interference and determining the effectiveness of EMI prevention measures.

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