Passive device for increasing the transmission efficiency of radio-frequency systems

A transmission device for performing an electromagnetic transmission between a sensor located on a rim of a wheel, the sensor rotating with said wheel, and processing means not rotating with said wheel, said transmission device comprising:

• a first antenna connected to said sensor and extending next to said sensor;
• a second antenna connected to said processing means and extending next to an extremity of a spindle supporting said wheel;
• a wheel cover attached to said wheel for covering said extremity of said axle, so that said first antenna extends outside said cover and said second antenna extends inside said cover;
• and
• at least one passive resonant circuit fixed on said cover, each passive resonant circuit including a first radiator element extending outside said cover so as to be in electromagnetic relation with said first antenna, a second radiator element extending inside said cover so as to be in electromagnetic relation with said second antenna, and a conductor that traverses said cover for electrically connecting said first radiator element and said second radiator element.