## 3 Design and Geometry of the Proposed Antenna
### S-Band Antenna Design
* The antenna must be mechanically robust and capable of withstanding both random vibrations and shocks during launch. The thermal design of the antennas must be meticulously evaluated, with the antennas themselves designed to function over a wide temperature range, from \(-50\)\({}^{\circ}\)C to \(+90\)\({}^{\circ}\)C.
* Furthermore, the selection of materials for the antenna must be made with great care, taking into account the effects of vacuum and micro-gravity without compromising considerations of EMC and mutual coupling amongst the payloads, circuits, and other antennas when fitted within a confined space. * A significant aspect of antenna design is the interaction between antennas and the modern CubeSat structures, as the spacecraft's structure can induce electromagnetic scattering and result in blockage effects on the antenna's radiation patterns. The interaction of this scattering with the antenna's radiation patterns can lead to significant degradation in gain performance and sidelobes, which, in turn, can have a substantial impact on the performance of the communication-link system. Consequently, a study was conducted to ascertain the most optimal positioning of the antenna, taking into account the link budget and coverage (see Figure 2). The design, development, integration, and measurement of a multilayer microstrip antenna has been undertaken, taking all these factors into account. The selection of microstrip technology is based on the advantages of being lightweight, low-profile, cost-effective, and flexible for integration, which is particularly crucial in space applications. Microstrip antennas can be used either as single elements when the gain requirements are low or in an array configuration such as microstrip patch antenna arrays, phased arrays, or reflect arrays in order to boost their gain, beamforming, and beam scanning performance [12]. However, the main limitation of microstrip patch antennas (MPAs) is their narrowband characteristics due to their high Q nature [14; 16]. A number of wideband approaches have been proposed to enhance the impedance bandwidth of microstrip patch antennas, such as the use of shorting pins or walls [17; 18], parasitic elements attached either to the radiating  
Figure 2: S-Band antenna model placed on ANSER cubeSats: (**a**) ANSER; (**b**) ANSER—AT (final position marked with a red circle). or non-radiating edge of the patch [19; 20], stacked multiple patches on different substrate layers [21], aperture-coupled feeding techniques [22; 23; 24], metamaterial-based antennas and increasing the substrate thickness relative to the free space wavelength or using substrates with dielectric constants close to unity. However, when employing any of the aforementioned techniques, a trade-off must be maintained between the bandwidth performance of the antenna and its radiating characteristics [9; 14; 16; 25; 26]. Notwithstanding this, in the present work, a wideband S-band multi-layer antenna has been developed, qualified, and integrated for Leader-S satellite, maintaining optimal radiation characteristics. Furthermore, the compact antenna design, with dimensions of 80 mm \(\times\) 80 mm \(\times\) 6.53 mm and a weight of 30 g, features dual circular polarization, a highly recommended characteristic in satellite communications. This provides increased mobility and freedom in the orientation angle between a transmitter and a receiver in comparison with a linearly polarized antenna [25]. The antenna's flat and compact design, facilitated by a single feed rather than multiple feeding points with phase-shifting networks, enables dual circular polarization without the need for additional components. This approach simplifies the antenna's design, reduces its weight and complexity, minimizes loss, and enhances aperture efficiency, making it particularly well-suited for space applications. However, it should be noted that the challenge of achieving dual circular polarization over a wide bandwidth remains significant despite the advantages offered by single-point feeding.