A low-frequency emission electronic unit (20′) includes two low-frequency antennas (B1, B2). The second antenna (B2) is passive and resonant, oriented along the main axis (Y) of the first low-frequency antenna (B1) and is adapted to generate two low-frequency fields (D2, D2′) at right angles to the field (D1) emitted by the first antenna (B1). The low-frequency emission electronic unit (20′) makes it possible to reduce the zones of rupture of reception of the low-frequency signals by the wheel unit (13) situated in proximity in which the low-frequency signals emitted by the low-frequency emission electronic unit are not received by the closest wheel unit (13). A low-frequency signal transmission method alternating the emissions of waves by the two antennas (B1, B2) is also described.