In the development of antennas in the 300GHz sub-terahertz band, low-loss antenna configurations are essential. We have developed low-loss, high-gain lens antennas, multi-beam antennas, and phased arrays using planar antennas that can be integrated into substrates with integrated circuits. Additionally, we have developed transmission-line transition circuits necessary for feeding these antennas. Compared to our exhibition two years ago, the development of low-loss substrates has significantly advanced, leading to greatly improved performance and increased options. We will introduce these design and development technologies.