A new electrically short pyramidal horn antenna is proposed. The proposed structure combines a pyramidal horn and a linearly tapered slot antenna (LTSA) to improve a front-to-back ratio (FBR). The LTSA inside a pyramidal horn is fed by a waveguide-to-finline transition. As most of the E-fields are guided through the LTSA, the horn may act as a reflector. With an optimized horn size, the backward radiation is significantly reduced. The simulated results show a gain of 10 dBi and a FBR of 25 dB in the frequency range from 690 MHz to 960 MHz. The FBR of the proposed antenna is enhanced over that of the pyramidal horn without a LTSA by a factor of 8 dB in the whole operation band. The total size of the proposed antenna is 450 (W) mm × 400 (H) mm × 120 (L2) mm.