Radio frequency signal transmission method for electromagnetic transponder system, involves controlling gain of transmitter amplifier by microcontroller to control modulation factor of transmission signal

摘要

#CMT# #/CMT# The method involves measuring information representative of current in an inductive unit (L2) of an oscillating circuit by a current transformer (35) to find a present value of a magnitude representative of a modulation factor of a transmission signal. Gain of a transmitter amplifier (32) is controlled by a microcontroller (31) to control the factor for controlling amplitude of modulation. #CMT# : #/CMT# An independent claim is also included for a radiofrequency transmitter. #CMT#USE : #/CMT# Used in an electromagnetic transponder system for radiofrequency signal transmission (claimed). #CMT#ADVANTAGE : #/CMT# The microcontroller controls the gain of the transmitter amplifier to control the modulation factor of the transmission signal for controlling amplitude of modulation, thus improving reliability of detection of signal by a receiver. The method eliminates any necessity of modifying the transponders. The method allows to detect a lack of modulation factor independently of the receiver. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The drawing shows a schematic view of a radiofrequency transmission terminal such as read-write terminal of an electromagnetic transponder system. L2 : Inductive unit 31 : Microcontroller 32 : Transmitter amplifier 35 : Current transformer 38 : Digital to analog converter.