Browse Prior Art Database

GROUP TRUNKING RECEIVER DESENSE PROTECTION

IP.com Disclosure Number: IPCOM000009741D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2002-Sep-16
Document File: 1 page(s) / 73K

Publishing Venue

Motorola

Related People

Dave Mills: AUTHOR [+2]

Abstract

In normal operation of private subscriber radios it is not uncommon to find the radio physically located very close to each other. This situation is common at a fire, or an accident where several pub- lic safety vehicles are all together at the scene of the event. When one of these units transmits, its trans- mit power is received into the front of all the other receiving radios at the scene. In the UHF and VHF public safety bands there may only be a few kilo- hertz separating the transmit frequency from the receive frequency. In this situation it is very com- mon for the receiving radio to receive so much power from the transmitting radio that it can no longer receive the signal from the fixed network equipment. This situation is called desense. When trunked subscriber radios are involved this situation is even worse as the radios may try to roam to another site, or may go out of range completely while the close by radio is transmitting.

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0 M M-LA Technical Developments

GROUP TRUNKING RECEIVER DESENSE PROTECTION

by Dave Mills and Marc Cassidy

  In normal operation of private subscriber radios it is not uncommon to find the radio physically located very close to each other. This situation is common at a fire, or an accident where several pub- lic safety vehicles are all together at the scene of the event. When one of these units transmits, its trans- mit power is received into the front of all the other receiving radios at the scene. In the UHF and VHF public safety bands there may only be a few kilo- hertz separating the transmit frequency from the receive frequency. In this situation it is very com- mon for the receiving radio to receive so much power from the transmitting radio that it can no longer receive the signal from the fixed network equipment. This situation is called desense. When trunked subscriber radios are involved this situation is even worse as the radios may try to roam to another site, or may go out of range completely while the close by radio is transmitting.

  One possible solution to this problem is the use of narrow front ends, or preselectors in the front end of the radio to eliminate this undesired signal. Due to the broad band nature of the radios, and the fact that the user can program the radios to any frequen- cy in the band these hardware solutions are not suf- ficient to solve the problem.

  If the transmitting radio and the receiving radio have the same talkgroup selected, or if the transrnit- ting radio is private calling the receiving radio then the following solution may be used to allow the desensed r...