Thermal detector for detecting electromagnetic radiation at a main wavelength λ c comprised in a predefined spectral range, comprising: ∘ a readout substrate, comprising a readout circuit, and having a main plane; ∘ a membrane suspended above and thermally insulated from the readout substrate, comprising: a thermometric transducer electrically connected to the readout circuit; and a resistive load making thermal contact with the thermometric transducer and suitable for converting into heat electromagnetic power received from a collecting antenna; ∘ the collecting antenna, which is suitable for collecting the electromagnetic radiation to be detected, is located away from the suspended membrane and is coupled to the resistive load with a view to transmitting thereto an electromagnetic power, the collecting antenna comprising - a track, referred to as the coupling track (16.1), which is located plumb with the resistive load; - a collecting lateral portion (16.2), which is connected to the coupling track (16.1) and extends therefrom into a region not overhung by the suspended membrane; ∘ characterized in that: • the resistive load is formed from a track that extends longitudinally to form a closed continuous loop; • the track referred to as the coupling track (16.1) extends longitudinally to form an open continuous loop, thus permitting inductive coupling between the coupling track (16.1) and the resistive load; • the collecting antenna has maximum outside dimensions (D a,x, D a,y) along two orthogonal axes in the main plane, each of the maximum outside dimensions (D a,x, D a,y) of the collecting antenna being smaller than or equal to λ c /8; • the coupling track (16.1) has maximum outside dimensions (D pc,x, D pc,y) along said orthogonal axes, each of the maximum outside dimensions (D pc,x, D pc,y) of the coupling track (16.1) being larger than or equal to 35% of the corresponding maximum outside dimension (D a,x, D a,y) of the collecting antenna. ∘ a readout substrate, comprising a readout circuit, and having a main plane; ∘ a membrane suspended above and thermally insulated from the readout substrate, comprising: a thermometric transducer electrically connected to the readout circuit; and a resistive load making thermal contact with the thermometric transducer and suitable for converting into heat electromagnetic power received from a collecting antenna; ∘ the collecting antenna, which is suitable for collecting the electromagnetic radiation to be detected, is located away from the suspended membrane and is coupled to the resistive load with a view to transmitting thereto an electromagnetic power, the collecting antenna comprising - a track, referred to as the coupling track (16.1), which is located plumb with the resistive load; - a collecting lateral portion (16.2), which is connected to the coupling track (16.1) and extends therefrom into a region not overhung by the suspended membrane; - a track, referred to as the coupling track (16.1), which is located plumb with the resistive load; - a collecting lateral portion (16.2), which is connected to the coupling track (16.1) and extends therefrom into a region not overhung by the suspended membrane; ∘ characterized in that: • the resistive load is formed from a track that extends longitudinally to form a closed continuous loop; • the track referred to as the coupling track (16.1) extends longitudinally to form an open continuous loop, thus permitting inductive coupling between the coupling track (16.1) and the resistive load; • the collecting antenna has maximum outside dimensions (D a,x, D a,y) along two orthogonal axes in the main plane, each of the maximum outside dimensions (D a,x, D a,y) of the collecting antenna being smaller than or equal to λ c /8; • the coupling track (16.1) has maximum outside dimensions (D pc,x, D pc,y) along said orthogonal axes, each of the maximum outside dimensions (D pc,x, D pc,y) of the coupling track (16.1) being larger than or equal to 35% of the corresponding maximum outside dimension (D a,x, D a,y) of the collecting antenna. • the resistive load is formed from a track that extends longitudinally to form a closed continuous loop; • the track referred to as the coupling track (16.1) extends longitudinally to form an open continuous loop, thus permitting inductive coupling between the coupling track (16.1) and the resistive load; • the collecting antenna has maximum outside dimensions (D a,x, D a,y) along two orthogonal axes in the main plane, each of the maximum outside dimensions (D a,x, D a,y) of the collecting antenna being smaller than or equal to λ c /8; • the coupling track (16.1) has maximum outside dimensions (D pc,x, D pc,y) along said orthogonal axes, each of the maximum outside dimensions (D pc,x, D pc,y) of the coupling track (16.1) being larger than or equal to 35% of the corresponding maximum outside dimension (D a,x, D a,y) of the collecting antenna.