Browse Prior Art Database

METHOD FOR AUTOMATIC RF SWITCHING BASED ON PRESENCE OF ANTENNA

IP.com Disclosure Number: IPCOM000006835D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2002-Feb-06
Document File: 2 page(s) / 97K

Publishing Venue

Motorola

Related People

Robert Ford: AUTHOR [+2]

Abstract

This circuit allows for automatic RF path selection based on the presence of the external antenna instead of the external adapter. By sensing the external antenna instead of the adapter, the circuit assures that RF remains routed to the internal antenna if the external antenna is inadvertently not connected to the external adapter.

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INC. Technical Developments Volume 19 June 1993

METHOD FOR AUTOMATIC RF SWITCHING

BASEDONPRESENCEOFANTENNA

by Robert Ford and Joseph Patino

   This circuit allows for automatic RF path selection based on the presence of the external antenna instead of the external adapter. By sensing the external antenna instead of the adapter, the circuit assures that RF remains routed to the internal antenna if the external antenna is inadvertently not connected to the external adapter.

  Users of two-way portable radios often operate the radios within vehicles using Vehicular Chargers. The com- munication range is reduced in this application by the vehicle metal shielding the radio's antenna. Informed users prefer to attach the vehicle roof antenna to the portable radiq by using an external speaker/microphone accessory with an external RF connector. The improved communication range and functionality by using this arrangement has in the past been accompanied by dis- advantages. The abiity to quickly exit the vehicle with the portable radio has been forfeited for improved range using the vehicle antenna. The user has had to remove the external antenna cable and the external adapter horn the radio before leaving the vehicle. The reason for remov- ing the adpter was to cause the radio to switch the RP signal back to the radio antenna. A previous design approach somewhat solved this problem. It incorporated an external RF switch onto the external adapter to allow for switching between internal and external RF paths. This too had a drawback. The user could select RF path incorrectly and lose communication. The automatic switching circuit solves this problem by switching the RF signal back to the radio antemra whenever the vehi- cle antenna cable is removed from the accessory. It also elimiiates the mechanical RF switch on the accessory and enhances the ease of use of the system by eliminat- ing the need for the user to select antenna. This circuit

enables th...