# Design and Analysis of Dual-Band High-Gain THz Antenna Array for THz Space Applications
###### Abstract  
In this paper, a high-gain THz antenna array is presented. The array uses a polyimide substrate with a thickness of 10 \(\upmu\)m, a relative permittivity of 3.5, and an overall volume of 2920 \(\upmu\)m \(\times\) 1055 \(\upmu\)m \(\times\) 10 \(\upmu\)m, which can be employed for THz band space communication and other interesting applications. The dual-band single-element antenna is designed in four steps, while operating at 0.714 and 0.7412 THz with \(-\)10 dB bandwidths of 4.71 and 3.13 GHz, providing gain of 5.14 and 5 dB, respectively. In order to achieve a high gain, multiple order antenna arrays are designed such as the 2 \(\times\) 1 antenna array and the 4 \(\times\) 1 antenna array, named type B and C, respectively. The gain and directivity of the proposed type THz antenna array are 12.5 and 11.23 dB, and 12.532 and 11.625 dBi at 0.714 and 0.7412 THz, with 99.76 and 96.6% radiation efficiency, respectively. For justification purposes, the simulations of the type B antenna are carried out in two simulators such as the CST microwave studio (CSTMWS) and the advance design system (ADS), and the performance of the type B antenna is compared with an equivalent circuit model on the bases of return loss, resulting in strong agreement. Furthermore, the parametric analysis for the type C antenna is done on the basis of separation among the radiating elements in the range 513 to 553 \(\upmu\)m. A 64 \(\times\) 1 antenna array is used to achieve possible gains of 23.8 and 24.1 dB, and directivity of 24.2 and 24.5 dBi with good efficiencies of about 91.66 and 90.35% at 0. Nonetheless, THz waves suffer from high attenuation due to atmospheric particles, such as water and gas molecules around the earth's surface [7; 8; 9; 10; 11]. In the case of free space communication with minimal attenuation loss and a reliable communication link, a few design contemplations are needed for the wireless communication antenna, such as a high-gain antenna with maximum data rate capacity, and high directivity [3]. In space, the THz wave antenna is a suitable candidate for any application [12]. A high-gain THz antenna is required especially for satellite communication [3], and according to ITU recommendations for satellite communication, radio astronomy, and spectroscopy, a THz antenna will require minimum directivity of 24 dBi for space communication [5]. Various antenna models were reported in the past for satellite communication (SatCom); all of them were highly directive. The most popular antennas used for these services were either a wire, or a horn antenna with a parabolic reflector, while operating at GHz bands; these THz antenna were either linear, circular, or elliptical polarized [13]. However, these models face some limitations at THz bands, such as structural complexities and getting overheated [14; 15; 16; 17; 18]. Present-day progress in super-high-speed terahertz (THz) communication systems demands low cost, a low profile, and exceptionally efficient antenna design [6] with high directivity, to overcome propagation loss at THz bands ranging from 0.1 to 10 THz [3; 4; 5]. The microstripe or planar antenna is the most suitable candidate antenna among the existing antenna models for overcoming these limitations [19] due to the easy fabrication and integration of the planar antenna with micro scale devices as compared to the millimeter scale horn antenna. The THz planar antennas are small in terms of the micrometer scale, but their operations at THz bands cause problems, such as low gain and low bandwidth [20]. Despite the fact that the planar antenna has low gain and directivity, it is still used in multiple fields because high directivity can be achieved by utilizing multiple methods, such as antenna array, PBG-based antenna, and the reflector method [21; 22]. However, the array technique is a suitable candidate that provides maximum gain and directivity as compared to other techniques [23].