Browse Prior Art Database

IMPROVED CLOCK FAILURE DETECTOR FOR USE ON GSM DIGITAL BOARDS

IP.com Disclosure Number: IPCOM000007085D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2002-Feb-25
Document File: 3 page(s) / 114K

Publishing Venue

Motorola

Related People

Barry Michael King: AUTHOR [+2]

Abstract

In general all clocks used in a GSM base station To improve system reliability it is desirable for should be derived from a single 16.384 MHz clock. each module to have the,capability to detect amiss- If the base station is implemented using multiple ing clock. For this reason all modules should have a modules then it is normal practice to distribute a missing clock detector. common clock to all modules.

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MO-LA Technical Developments Volume 21 February 1994

IMPROVED CLOCK FAILURE DETECTOR FOR USE ON GSM DIGITAL BOARDS

by Barry Michael King and Ian Charles Cox

  In general all clocks used in a GSM base station To improve system reliability it is desirable for should be derived from a single 16.384 MHz clock. each module to have the,capability to detect amiss- If the base station is implemented using multiple ing clock. For this reason all modules should have a modules then it is normal practice to distribute a missing clock detector.
common clock to all modules.

PRIOR ART

Reference Alarm

Figure I Current Missing Clock Detector.

Figure 1 shows a current method employed on GSM digital boards to detect a missing clock on a
16.384 MHz reference signal.

  The circuit makes use ofa positive edge triggered monostable. A positive clock edge on input A trig- gers Monostable B. This causes Output C to change state from logic zero to logic one.

  The Monostable time constant (D) is chosen such that the timeout period is greater than the time between successive positive edges on the 16.384 MHz reference clock. Thus the monostable output C

remains at logic one. If a clock edge is missed then the monostable times out, output C changes state to logic zero. This signal is used to generate the
16.384 MHz Reference alarm.

  Note that the existing circuit may not detect a 'noisy' clock, i.e. a clock with extra positive edges or distorted waveform.

NEW ART

  From the prior art, 'we have seen the method usually employed to detect clock failures on GSM digital boards. However ,to improve the method we need to solve the following.

20 0 Motorola. 0°C. 1994

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0 M MO-LA

Technical Developments Volume 21 February 1994

1) How to eliminate the requirements for a time- base stations, they may equally be valid for any Base out period. Station where digital speech compression is used
2) How to detect a 'noisy' or distorted waveform. e.g. private mobile radio, PC...