Browse Prior Art Database

MULTI-PURPOSE CONTACT AND RF SHIELD

IP.com Disclosure Number: IPCOM000006710D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2002-Jan-24
Document File: 4 page(s) / 183K

Publishing Venue

Motorola

Related People

Michael P. Goldenberg: AUTHOR

Abstract

Selective call receivers, including pagers, generally comprise a receiver and decoder board, each having a plurality of electrical components placed primarily on one side. The receiver and decoder board typically require RF shielding to protect the electrical components from RF interference. This RF shielding is commonly pro- vided by a stamped piece of sheet metal or something similar and placed in-between the receiver and decoder board. The positioning of the receiver/decoder board and RF shield has not been critical due to the relatively large size ofthe typical selective call receiver.

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MO'IY)ROLA INC. Technical Developments Volume 17 December 1992

MULTI-PURPOSE CONTACT AND RF SHIELD

by Michael F! Goldenberg

   Selective call receivers, including pagers, generally comprise a receiver and decoder board, each having a plurality of electrical components placed primarily on one side. The receiver and decoder board typically require RF shielding to protect the electrical components from RF interference. This RF shielding is commonly pro- vided by a stamped piece of sheet metal or something similar and placed in-between the receiver and decoder board. The positioning of the receiver/decoder board and RF shield has not been critical due to the relatively large size ofthe typical selective call receiver.

  As electronic circuits have become miniaturized, it has become possible to package a selective call receiver in a housing suitable to be comfortably worn on the wrist (e.g., wristwatch pager). The wristwatch pager has similar RF shielding problems as a conventional selec- tive call receiver, however, the size constraints are differ- ent. In the past, the non-component sides of the receiver and decoder board have been placed back-to-back, allowing a flat, stamped sheet metal shield to be placed in-between at relatively low cost. However, this has not provided optimal usage of the space within the housing.

  Another component of the conventional selective call receiver is the use of switches to activate the selec- tive call receiver's functions. These switches may comprise a variety of configurations without impacting the final shape of the selective call receiver, due to its relatively large size when compared to the wristwtch pager. There- fore, the switches on a selective call receiver have typi- cally been independent of the RF shield.

  A conventional wristwatch also requires switches to activate its functions. These switches have generally been formed from a stamped piece of sheet metal but do not function as an RF shield due to a lack of a receiver. Therefore, this contact plate serves no other purpose than to activate the wristwatches functions. Thus, a need exists for a wristwatch pager having a grounded RF shield having contact switching cpabilities.

Referring to Figures 1 and 2, a wristwatch pager 10

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includes a frame 12, comprising a substantially flat plate 14 having switch contacts 16,18,20 and 22. The frame 12 is disposed between two circuit supporting substrates
(e.g., integrated circuit boards or the like) for providing radio frequency (RF) shielding between the two circuit supporting substrates, as will be more fully discussed below. Specifically, the frame 12 has two primary sur- faces 36, 38 and is positioned between a frst integrated circuit board 24 (e.g., receiver board) and a second integrated circuit board 26 (e.g., decoder board). The receiver and decoder boards, 24 and 26, include a first and second plurality of electrical components 28 (not shown) and 30, placed on surfaces 56 an...