Browse Prior Art Database

MICROPROCESSOR CONTROLLED SQUELCH HYSTERESIS

IP.com Disclosure Number: IPCOM000007439D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2002-Mar-26
Document File: 1 page(s) / 44K

Publishing Venue

Motorola

Related People

Klaus Peter PAI: AUTHOR [+2]

Abstract

As soon as the squelch switches the audio elf, the software increases the squelch attenuator (e.g. in the ASFIC chip) by some steps. This keeps the audio switched off.

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MOTOROLA Technical Developments

MICROPROCESSOR CONTROLLED SQUELCH HYSTERESIS

by Klaus Peter PAI and Bernhard Hammes

  As soon as the squelch switches the audio elf, the software increases the squelch attenuator (e.g. in the ASFIC chip) by some steps. This keeps the audio switched off.

  If the carrier increases and the squelch switches the audio on again, the original attenuator value is loaded into the squelch attenuator which keeps the audio switched on.

PROBLEM:

  The squelch hysteresis usually depends on the bandwidth and filter characteristic ofthe radios inter- mediate Frequency amplifier, the ambient tempera- ture and the squelch setting.

  A stable and accurate squelch hysteresis is desir- able for all portables, mobiles and base stations in order to optimize the operation comfort and the read- ability. For some systems or customers e.g. Radiocom 2000 a certain squelch hysteresis and squelch sensi- tivity is specified.

ADVANTAGE:

SOLUTION:

  Change squelch attenuator, which is controlled via the microprocessor, in dependancy on the audio noise in the following way:

  With the help of the described routine it is pos- sible to determine the squelch hysteresis in depend- ency on the temperature, IF bandwidth and filter characteristic, Rffrontend/IF gain, and squelch set- tings. This results in a very accurate squelch hyster- esis under all conditions and in turn a very stable squelch behaviour.

55 July 1995

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