 high SNR, innova- tive antenna geometry designs, are proposed which help in the terahertz research area. The 3D schematic diagram of the interdigitated PCA electrode structure is given in Figure 12.6. The interdigitated photoconductive antenna (IPCA) geometry helps in overcoming the drawbacks of other antenna designs. There are interdigitated photo mixers for continuous THz radiation and interdigitated photoconductive antennas to emit the pulsed terahertz. In this structure, finger like electrodes are added to the photoconductive active area gap (like dipole PCA) on the top of semiconductor sub- strate material. The large gap and small gap antenna have their own pros and cons. The IPCAs combine the advantages of both large aperture and small aperture antennas. The advantages of having a large area between the dipole electrodes are high carrier density, high power, less laser repetition rate, reduction of diffraction and the fact that the use of a silicon lens can be avoided. But due to the large gap, many unpaired carriers cause a screening effect which affects the PCA performance. This can be mitigated by placing inter-weaved fingers in the antenna gap area which reduces the gap between the electrodes and also reduces the carrier drift time. Because of this small gap due to the placement of interdigitated electrodes, the antenna is driven with less input power and leads to high terahertz electric fields, high SNR compared to the large gap antennas such as dipoles, bow-tie antennas, and the like. To make the 300um Tolum 300um FIGURE 12.6 Schematic diagram of slot IPCA 3D view. 5G Wireless Communication System in Healthcare Informatics FIGURE 12.7 Top view of (a) 2-elements interdigitated PCA (b) 5-elements interdigitated PCA (c) 13-elements interdigitated PCA. electric field distribution uniform and to accelerate the carriers, several techniques, such as having a second metallization layer, binary phase masking, a micro lens array, can be employed in the interdigitated structures. This leads to further improveme