An antenna for emitting radiation from at least one electromagnetic traveling wave which propagates along a guide path determined by a structure of the antenna, the antenna comprising at least one spiral segment and a common feed input located at a starting point of each spiral segment, said guide path forming a transmission line dedicated to the traveling wave and having a path portion following each spiral segment (11, 12) to a terminal end of said spiral segment, and, when the spiral segments (11, 12) are two or more, each spiral segment alternately intersecting centrifugal radial directions originating from the location of the feed input of said antenna, the guide path further comprising a continuous loop which surrounds each spiral segment (11, 12), and the terminal end of each spiral segment is connected to the loop at a connection point (PR1, PR2) of said spiral segment, whereby the antenna is configured so that an electrical signal that is transmitted to the feed input of the antenna produces a traveling wave which propagates along each spiral segment, then is transmitted to the loop at the connection point of said spiral segment, the loop thus constituting at least a portion of a radiative zone of the antenna, the antenna further comprises, for each spiral segment (11, 12), a bridging structure (SP1, SP2) which is arranged to connect, for the transmission of the traveling wave and in addition to the connection point (PR1, PR2), said spiral segment to the loop upstream of said connection point relative to the propagation direction of the traveling wave along the spiral segment, and, for said spiral segment (11, 12), two lengths of the guide path between the bridging structure (SP1, SP2) and the connection point (PR1, PR2), respectively measured along the spiral segment and along the loop, are each equal to one-fourth, within +/- 20%, of a same effective wavelength value of the traveling wave, which corresponds to a frequency value belonging to a transmission band of the antenna. the antenna comprising at least one spiral segment and a common feed input located at a starting point of each spiral segment, said guide path forming a transmission line dedicated to the traveling wave and having a path portion following each spiral segment (11, 12) to a terminal end of said spiral segment, and, when the spiral segments (11, 12) are two or more, each spiral segment alternately intersecting centrifugal radial directions originating from the location of the feed input of said antenna, the guide path further comprising a continuous loop which surrounds each spiral segment (11, 12), and the terminal end of each spiral segment is connected to the loop at a connection point (PR1, PR2) of said spiral segment, whereby the antenna is configured so that an electrical signal that is transmitted to the feed input of the antenna produces a traveling wave which propagates along each spiral segment, then is transmitted to the loop at the connection point of said spiral segment, the loop thus constituting at least a portion of a radiative zone of the antenna, the antenna further comprises, for each spiral segment (11, 12), a bridging structure (SP1, SP2) which is arranged to connect, for the transmission of the traveling wave and in addition to the connection point (PR1, PR2), said spiral segment to the loop upstream of said connection point relative to the propagation direction of the traveling wave along the spiral segment, and, for said spiral segment (11, 12), two lengths of the guide path between the bridging structure (SP1, SP2) and the connection point (PR1, PR2), respectively measured along the spiral segment and along the loop, are each equal to one-fourth, within +/- 20%, of a same effective wavelength value of the traveling wave, which corresponds to a frequency value belonging to a transmission band of the antenna.