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Automatic Shielding Degradation Detector

IP.com Disclosure Number: IPCOM000060517D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Price, LA: AUTHOR

Abstract

A method of automatically detecting when the shielding effectiveness of an RF enclosure has been degraded permits corrective action. An FM modulated RF source and its associated antenna are placed inside an equipment rack for protection from interference. The source is crystal controlled to ensure stability of the signal. Modulation is provided by a continuous coded tone squelch (CCTS) encoder to reduce the possibility of an extraneous RF signal causing a false alarm. The field intensity of the radiated signal is closely controlled to maintain a constant level at the receiver. The RF receiver is located outside an enclosure for protection. The receiver is also crystal controlled for stability.

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Automatic Shielding Degradation Detector

A method of automatically detecting when the shielding effectiveness of an RF enclosure has been degraded permits corrective action. An FM modulated RF source and its associated antenna are placed inside an equipment rack for protection from interference. The source is crystal controlled to ensure stability of the signal. Modulation is provided by a continuous coded tone squelch (CCTS) encoder to reduce the possibility of an extraneous RF signal causing a false alarm. The field intensity of the radiated signal is closely controlled to maintain a constant level at the receiver. The RF receiver is located outside an enclosure for protection. The receiver is also crystal controlled for stability. The receiver incorporates a window detector and CCTS decoder to detect degradation of the shielding of the enclosure and/or loss of signal, indicating detector malfunctions. Fig. 1 shows the source portion, which is located inside the RF enclosure. Crystal X1 determines the operating frequency. Encoder E1 provides low frequency FM modulation to the RF exciter E2. The exciter provides a modulated RF source for the driver D1, which in turn provides the rf input for the power amplifier (PA). The output of the power amplifier is connected to a radiating element ANT-1. The feedback circuit (FB) is used to maintain a constant field strength from the antenna by controlling the gain of the driver. Fig. 2 is a block diagram of the receiver-de...