## 3 Antennas with General Aspects Utilized for CubeSat
### Planar Phased Patch Antennas and Their Arrays
The research includes constructing and testing the prototype in an anechoic chamber, demonstrating its potential to significantly enhance CubeSat communication performance. In Ref. [9], CubeSats, which are a type of nano-satellite, offer a cost-effective platform for space missions that now support applications involved in Earth observation, remote sensing, deep space exploration, and intersatellite communication. Advancements in antenna technology have driven their development to meet diverse mission requirements. Despite their potential, CubeSats face challenges such as limited data rates. Transceivers with elevated gain and data rates are currently being developed to address these challenges. Circularly polarized (CP) antennas are essential for reliable communication, mitigating issues like antenna misalignment and atmospheric Faraday rotation. Among the various antenna types, microstrip patch antennas are the most versatile for CubeSat missions because of their low profile, light weight, cost-effectiveness, and integration issues. Microstrip patch arrays deliver high gain and are CP, which are crucial for high-data-rate downlinks. Designing CP microstrip arrays involves techniques like sequential feeding with a 90\({}^{\circ}\) phase shift between elements. While practical, this method adds design complexity and potentially leads to signal loss. The SPORT is a CubeSat mission jointly developed by Brazil and the United States to study space weather. The SPORT CubeSat uses an X-band radio for downlink communications, featuring a custom-designed circularly polarized antenna positioned on the nadir side to face Earth consistently. This low-cost antenna meets specific size and reliability requirements for consistent communication as the CubeSat rises from the horizon. In the communication link, transmitted power experiences losses due to device imperfections, atmospheric attenuation, antenna polarization mismatches, and path losses, which are calculated using the Friis transmission equation. The receiver antenna also introduces noise due to environmental interference and heat generated by resistance and internal components. The SNR, the proportion of received power to noise, must exceed a threshold for reliable communication. A link margin above 0 dB indicates a successful signal reception, with an ideal margin exceeding 3 dB. The SNR maximum depends on the required BER and the modulation technique employed [10]. Reference [11] presents a compact UHF multi-band RHCP quadrifilar antenna devised for CubeSat communications, operating in the LoRa bands. The antenna employs two FR4-epoxy substrates linked by shorting pins, with a ceramic insertion in between and screws for mechanical robustness against launch vibrations. By utilizing parasitic elements, it achieves a multi-band functionality, while its quadrifilar structure ensures effective RHCP radiation, mitigating alignment issues with terrestrial stations. Measurements in the anechoic chambers showed a 2.3 dBic gain at 870 MHz and 1.1 dBic at 920 MHz, featuring an AR \(<\) 3 dB across a 120\({}^{\circ}\) aperture beamwidth. The antenna demonstrated successful real-world application in a 3U CubeSat launched with validated ground-to-space communications. However, the challenges included reduced gain when integrated into the CubeSat due to chassis-induced vertical currents, a modest fractional bandwidth of 7.8%, and a suboptimal RF performance by the FR4 material despite its mechanical advantages. Overall, the design offers a robust solution for CubeSat communications, with potential areas for improvement including the material and integration effects. Reference [12] presents a transparent microstrip GPS antenna designed for CubeSat applications, utilizing transparent conductive materials to maintain optical transparency while ensuring RF functionality.