We have developed an antipodal linearly tapered slot antenna (LTSA) with corrugation for a 94-GHz band passive millimeter-wave (PMMW) imaging system. We propose a compact microstrip-slot transition for the antenna interface. Transmission loss of the transition is about 1.7 dB @94 GHz. We also present a design procedure for a circular radiation pattern for the antipodal LTSA which is well suited to our lens-coupled PMMW imaging. Using this design technique, we fabricated an antipodal LTSA. The measured 10-dB beam widths of the E- and H-plane radiation pattern @94 GHz are 50 deg and 54 deg, respectively. The size of the antenna is 16 × 3.7 mm2.