Biotelemetric device integrable within a biocompatible capsule and intended for use in a biological environment after ingestion or in vivo implantation, to be used in conjunction with an external device, the biotelemetric device comprising: - a microcontroller configured to generate an electrical setpoint signal (CS); - a radio antenna configured to transmit at least an electromagnetic wave (EMS) by converting an incident electrical signal (IS), in order to transmit data to said external device via a radio connection with said external device; - a radio frequency circuit , interconnected between the microcontroller and the radio antenna , the radio antenna being configured to, when the biotelemetric device is placed in the biological environment , be impedance mismatched with respect to the radio frequency circuit so as to generate a reflected electrical signal (RS) by reflection of a fraction of the incident electrical signal while the radio antenna emits the electromagnetic wave (EMS); in which the radiofrequency circuit is configured to take a first fraction (CS2) of the electrical setpoint signal, transmit to the radio antenna a second (CS1) fraction of the electrical setpoint signal forming the incident electrical signal (IS) and take the electrical signal (RS) reflected by the radio antenna ; in which the microcontroller is configured to determine, relative to the first fraction (CS2) of the electrical setpoint signal, a reflection coefficient (S 11 ) corresponding to the fraction of the electrical signal reflected (RS) by the radio antenna . - a microcontroller configured to generate an electrical setpoint signal (CS); - a radio antenna configured to transmit at least an electromagnetic wave (EMS) by converting an incident electrical signal (IS), in order to transmit data to said external device via a radio connection with said external device; - a radio frequency circuit , interconnected between the microcontroller and the radio antenna , the radio antenna being configured to, when the biotelemetric device is placed in the biological environment , be impedance mismatched with respect to the radio frequency circuit so as to generate a reflected electrical signal (RS) by reflection of a fraction of the incident electrical signal while the radio antenna emits the electromagnetic wave (EMS); in which the radiofrequency circuit is configured to take a first fraction (CS2) of the electrical setpoint signal, transmit to the radio antenna a second (CS1) fraction of the electrical setpoint signal forming the incident electrical signal (IS) and take the electrical signal (RS) reflected by the radio antenna ; in which the microcontroller is configured to determine, relative to the first fraction (CS2) of the electrical setpoint signal, a reflection coefficient (S 11 ) corresponding to the fraction of the electrical signal reflected (RS) by the radio antenna . the radio antenna being configured to, when the biotelemetric device is placed in the biological environment , be impedance mismatched with respect to the radio frequency circuit so as to generate a reflected electrical signal (RS) by reflection of a fraction of the incident electrical signal while the radio antenna emits the electromagnetic wave (EMS); in which the radiofrequency circuit is configured to take a first fraction (CS2) of the electrical setpoint signal, transmit to the radio antenna a second (CS1) fraction of the electrical setpoint signal forming the incident electrical signal (IS) and take the electrical signal (RS) reflected by the radio antenna ; in which the microcontroller is configured to determine, relative to the first fraction (CS2) of the electrical setpoint signal, a reflection coefficient (S 11 ) corresponding to the fraction of the electrical signal reflected (RS) by the radio antenna . <EOS>