Browse Prior Art Database

PREVENTION OF TONE-CONTROL SIGNALING FALSE DETECT IN THE PRESENCE OF CONTINUOUS DIGITAL-CONTROLLED-SQUELCH-SYSTEM (CDCSS) SIGNALING

IP.com Disclosure Number: IPCOM000007795D
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2002-Apr-24
Document File: 1 page(s) / 71K

Publishing Venue

Motorola

Related People

James Gehrke: AUTHOR [+3]

Abstract

Modern wireless communications base stations often need to have the ability to detect Tone-Control signals and "Continuous Digital-Controlled-Squelch- System" (CDCSS) signals simultaneously. The prob- lem caused due to the simultaneous use of both sig- naling methods is that the CDCSS signals have frequency components which fall in the Tone-Control signal detection bandwidth. This results in a false indication of the presence of the Tone-Control sig- nal. The design approach outlined prevents the false detection of the Tone-Control signaling while CDCSS signaling is also present.

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Technical Developments

PREVENTION OF TONE-CONTROL SIGNALING FALSE DETECT IN THE PRESENCE OF CONTINUOUS DIGITAL-CONTROLLED-SQUELCH-SYSTEM (CDCSS) SIGNALING

by James Gehrke, Pete Biancalana and Terry Mansfield

BACKGROUND:

  Modern wireless communications base stations often need to have the ability to detect Tone-Control signals and "Continuous Digital-Controlled-Squelch- System" (CDCSS) signals simultaneously. The prob- lem caused due to the simultaneous use of both sig- naling methods is that the CDCSS signals have frequency components which fall in the Tone-Control signal detection bandwidth. This results in a false indication of the presence of the Tone-Control sig- nal. The design approach outlined prevents the false detection of the Tone-Control signaling while CDCSS signaling is also present.

PRINCIPLE OF OPERATION:

  The existing Tone-Control signaling detect algo- rithm relies on detecting energy at a particular he- quency by utilizing DSP based Discrete Fourier Transform techniques. The technique relies on the fact that Tone-Control signaling energy peaks in a frequency band that is lower than all the other mod- ulation frequencies. This detection of modulation energy in the sub-audible frequency band has a prob- lem if it does not take into account the fact that CDCSS signaling is also present. The CDCSS mod- ulation will have spectrum components that could fall in the Tone-Control detection bandwidth. CDCSS and other types of sub-audible signaling can gener...