Optical Filters

EmiClare windows provide exceptional optical performance without sacrificing the characteristics of EMI shielding.

The unique EmiClare mesh configuration eliminates the complexity of wire types, mesh counts and plated finishes found in conventional windows.

This data sheet provides the components to estimate the Emi/rfi shielding performance of an EmiClare window. The data is based on an extensive development program followed by testing in accredited test houses in the USA and England.

The attenuation properties of the emi/rfi shielding medium

Three factors determine the EMI shielding effectiveness of a window:

1. The attenuation properties of the shielding medium
2. The shadow effect of the aperture
3. The efficiency of the termination

Termination Efficiency

The most efficient termination is the direct contact of the mesh to the bezel / enclosure via a mesh extension. Data for two standard EmiClare terminations are listed below:

Silver busbar	100 MHz - 10 GHz	10dB loss
Silver busbar and	100 MHz - 3 GHz	10 dB loss
conductive gasket	4 GHz - 10 GHz	0 dB loss

(Conductive fabric over foam gasket)

Between 10 and 100 MHz, Optical Filters has found that traditional terminations with a silver busbar contacting the cross section of the wire are ineffective. We advise that the window uses one of the extended mesh terminations.

Aperture Shadow Effect

In cases where the emission levels are known, the shadow effect of the aperture can be estimated from the nomograph and added to the mesh attenuation with allowance for the termination:

 

Example

Opening Size:	250 x 200 mm
Max. dimension is diagonal	320 mm

Frequency MHz	1.0	5.0	10	50	100	500	1000
Aperture Attn dB	53	39	33	19	13	0	0
Mesh Attn dB	70	70	70	58	73	60	53
Silver Busbar dB	-10	-10	10	-10	-10	-10	-10
Overall Attn dB	113	99	93	67	76	50	43