For the limited power capacity of single dipole antenna, the lens antenna and photoconductive antenna array were designed to improve the radiation performance. At first, the lens antennas with radius of 0.5 mm, 1.0 mm and 1.5mm were designed, and the influence of the radius and extension length of the lens on the antenna performance was studied. The results indicated that when the ratio of extension length to radius was 0.28, the directivity of the lens antenna was better, and the peak gain of the 0.5 mm lens antenna reached 26.1 dB. Further, a 2×2 photoconductive antenna array was designed. The radiated power of the array element was about 10 μW, and the signal-to-noise ratio of the array element was about 50 dB. The experimental results showed that experimental results show that the combination efficiency of terahertz signals was close to 90%, which improved the output power of terahertz. It provided basis for the design and manufacture of miniaturized antenna arrays with more array elements. The factor affecting the noise generated by the terahertz photoconductive antenna was also studied.