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THRU WALL, SHIELDED FILTERED SIGNAL PROPAGATION ON TWO-SIDED CIRCUIT BOARDS

IP.com Disclosure Number: IPCOM000008077D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-16
Document File: 2 page(s) / 92K

Publishing Venue

Motorola

Related People

Peter P. Walter: AUTHOR [+2]

Abstract

Electromagnetic compatibility (EMC) require- ments and standards for two way radios have con- tinued to become a greater concern and more strin- gent. Fulfilling these requirements usually demands the use of some type of shielded enclosure. An often overlooked aspect of the shielded enclosure is the method used to pass signals into and out from the enclosure. If these lines are not shielded or properly filtered, the shielding effectiveness of the enclosure is reduced. For example, signals within the enclo- sure will couple onto the lines exiting the enclosure. These signals will be conducted out of the enclosure and then be radiated. This radiation could cause the system to fail the EMC requirements. An effective means to reduce the level of the conducted energy is to use a feedthru capacitor or some other filter at the point where the signal lines leave or enter the enclo- sure.

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MOTOROLA Technical Developments

THRU WALL, SHIELDED FILTERED SIGNAL PROPAGATION ON TWO-SIDED CIRCUIT BOARDS

by Peter P. Walter and Robert B. Widmayer

BACKGROUND

  Electromagnetic compatibility (EMC) require- ments and standards for two way radios have con- tinued to become a greater concern and more strin- gent. Fulfilling these requirements usually demands the use of some type of shielded enclosure. An often overlooked aspect of the shielded enclosure is the method used to pass signals into and out from the enclosure. If these lines are not shielded or properly filtered, the shielding effectiveness of the enclosure is reduced. For example, signals within the enclo- sure will couple onto the lines exiting the enclosure. These signals will be conducted out of the enclosure and then be radiated. This radiation could cause the system to fail the EMC requirements. An effective means to reduce the level of the conducted energy is to use a feedthru capacitor or some other filter at the point where the signal lines leave or enter the enclo- sure.

PROBLEM

  Although feedthru capacitors will generally pro- vide the greatest filtering, they can be expensive and they require mechanical assembly, hand solder- ing or additional connector assemblies. In today's

cost conscious markets a less expensive yet more manufacturable and reliable alternative is necessary. The problem becomes how to implement the filter- ing and shielding entirely by using the two primary components of a module: the enclosure and printed circuit board (PCB).

SOLUTION

  This invention incorporates two s...