An antenna device comprising: - at least two radio antennas , each comprising electrical connection ports , said electrical connection ports are arranged on one and the same substrate , - a transmitter and/or receiver electronic circuit, - electrically conductive means for connecting the ports of said at least two radio antennas to the transmitter and/or receiver electronic circuit, and wherein - each radio antenna is shaped to present, in a predetermined electromagnetic frequency band in which it operates, an impedance mismatch with the transmitter and/or receiver electronic circuit such that its input or output reflection coefficient is greater than a predetermined threshold value of -6 dB in logarithmic values in the absence of any impedance matching, this predetermined threshold value corresponding to a tolerance threshold value below which each radio antenna is considered impedance matched with the transmitter and/or receiver electronic circuit for a mobile telephony application, and - the electrically conductive connection means comprise capacitive, inductive and/or resistive electrical components for impedance matching with the transmitter and/or receiver electronic circuit, arranged to reduce said reflection coefficient to a value below the predetermined threshold value in said predetermined electromagnetic frequency band, and - said at least two radio antennas are printed antennas extending on at least one face of said same substrate , in a first radiating portion of this substrate, and - said electrically conductive connection means extend in a second portion of said same substrate , separated from the first radiating portion by a ground plane extending in a plane intersecting a main plane in which said same substrate extends. - at least two radio antennas , each comprising electrical connection ports , said electrical connection ports are arranged on one and the same substrate , - a transmitter and/or receiver electronic circuit, - electrically conductive means for connecting the ports of said at least two radio antennas to the transmitter and/or receiver electronic circuit, and wherein - each radio antenna is shaped to present, in a predetermined electromagnetic frequency band in which it operates, an impedance mismatch with the transmitter and/or receiver electronic circuit such that its input or output reflection coefficient is greater than a predetermined threshold value of -6 dB in logarithmic values in the absence of any impedance matching, this predetermined threshold value corresponding to a tolerance threshold value below which each radio antenna is considered impedance matched with the transmitter and/or receiver electronic circuit for a mobile telephony application, and - the electrically conductive connection means comprise capacitive, inductive and/or resistive electrical components for impedance matching with the transmitter and/or receiver electronic circuit, arranged to reduce said reflection coefficient to a value below the predetermined threshold value in said predetermined electromagnetic frequency band, and - said at least two radio antennas are printed antennas extending on at least one face of said same substrate , in a first radiating portion of this substrate, and - said electrically conductive connection means extend in a second portion of said same substrate , separated from the first radiating portion by a ground plane extending in a plane intersecting a main plane in which said same substrate extends. <EOS>