An antenna device comprising: - at least two radio antennas (20, 22), each comprising electrical connection ports (20A, 20B, 22A, 22B), said electrical connection ports (20A, 20B, 22A, 22B) are arranged on one and the same substrate, - a transmitter and/or receiver electronic circuit, - electrically conductive means (24, 26, 28) for connecting the ports (20A, 20B, 22A, 22B) of said at least two radio antennas (20, 22) to the transmitter and/or receiver electronic circuit, and wherein - each radio antenna (20, 22) 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 (20, 22) is considered impedance matched with the transmitter and/or receiver electronic circuit for a mobile telephony application, and - the electrically conductive connection means (24, 26, 28) comprise capacitive, inductive and/or resistive electrical components (40, 42, 46) 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 (20, 22) 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 (24, 26, 28) 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 (20, 22), each comprising electrical connection ports (20A, 20B, 22A, 22B), said electrical connection ports (20A, 20B, 22A, 22B) are arranged on one and the same substrate, - a transmitter and/or receiver electronic circuit, - electrically conductive means (24, 26, 28) for connecting the ports (20A, 20B, 22A, 22B) of said at least two radio antennas (20, 22) to the transmitter and/or receiver electronic circuit, and wherein - each radio antenna (20, 22) 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 (20, 22) is considered impedance matched with the transmitter and/or receiver electronic circuit for a mobile telephony application, and - the electrically conductive connection means (24, 26, 28) comprise capacitive, inductive and/or resistive electrical components (40, 42, 46) 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 (20, 22) 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 (24, 26, 28) 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.