Mil-Std-461 Emi Filter Design How To Design An
Mil-Std-461 Emi Filter Design Upgrade Your Browser

It is beneficial to translate the limits to millivolts in addition to the standard dBV.

Mil-Std-461 Emi Filter Design Upgrade Your Browser

Please upgrade your browser to improve your experience and security.

Each of the standards encompasses multiple revisions, any one of which may be enforced by the application.

Additionally, each standard features subsections that apply as dictated by the end installation.

To satisfy the standard, designers need to introduce EMI filters.

Mil-Std-461 Emi Filter Design How To Design An

Lets take a closer look at how to design an effective filter to ensure compliance.

The standard addresses a number of characteristics including conducted emissions, conducted susceptibility, radiated emissions, and radiated susceptibility.

Emission refers to the noise a device generates as it impacts the source to which it is connected.

Susceptibility is the vulnerability of a system to incoming noise.

Frequently, manufacturers will also reference CE101 because the frequency band of interest (30 Hz to 10 kHz) is well below the switching frequencies of most DC-DC converters.

Conducted emission and susceptibility requirements, not radiated requirements, are quoted because radiated sections are significantly dependent upon the physical layout, external output circuitry, and the enclosure in which the power supply resides.

With a valid filter design and good PCB layout, most components can easily meet conducted requirements.

There is not much difference between revision E and the earlier revision D; in fact, of sections CE101, CE102, CS101, CS114, and CS116, only CS101 and CS114 differ as follows.

Conducted measurements are measurements of either voltages or currents flowing in the leads of the device under test, as dictated by the standard.

Common-mode conducted noise current is the unidirectional (in phase) component in both the positive and negative inputs to the module.

This current circulates from the converter via the power input leads to the DC source and returns to the converter via the output lead connections.

This represents a potentially large loop cross-sectional area that, if not effectively controlled, can generate magnetic fields.

Common-mode noise is a function of the rate of change of voltage (dvdt) across the main switch in the converter and the effective input to output capacitance of the converter.

If we can greatly reduce the conducted emissions then we will reduce the radiated emissions, as well.

The enclosure of the device under test, lead geometry, and other devices running within the device under test will affect the emissions.

Radiated emissions due to B-fields are best addressed by shielding with a suitable material and proper layout.

Given the limits, we will need to understand the source of the noise to determine the amount of attenuation required to stay below the limits.