A microstrip second-iteration square Koch dipole fractal antenna is presented. This meandered antenna has a total length of 56.56 cm including its feed gap and was printed on the diagonal of a 100 mm × 100 mm PCB card that acts as CubeSat face. The antenna that was designed to optimize space shows acceptable performance at its resonance frequency of 455 MHz within the 70-centimeter band, a band that is commonly used for TTC CubeSat subsystems. The designed fractal antenna shows a reflection coefficient below −20 dB, a VSWR below 1.2, a −10 dB bandwidth of 50 MHz, and impedance magnitude of 56 Ω, while the average maximum gain around its resonance frequency is 2.14 dBi. All these parameters make this designed antenna suitable for small satellite applications at a band where a linear λ/2 dipolar antenna working at 455 MHz would be about 32.97 cm long, which does not fit within the largest dimension of a CubeSat face corresponding to 14.14 cm.
In this work, a comparison of the microwave absorption properties of Opuntia ficus-indica cladodes, Agave atrovirens branches, and Cocos nucifera L. husk samples was performed. The study was carried out by inserting dry and powdered samples of these organic materials transversely and in the middle of a rectangular waveguide, for which scattering parameters S21 and S11 were measured to estimate the absorption coefficient. These measurements were compared to determine the material that behaves the best as a microwave absorber with a view to develop future low-cost and eco-friendly products by reusing agricultural waste. Specifically, Agave atrovirens sample showed the best performance, having an average value of absorption coefficient of 0.4218, while its maximum was 0.5792 at 9.706 GHz within the range from 8.005 to 13 GHz.
As in any satellite, onboard antennas for CubeSats are crucial to establish communication with ground stations or other satellites. According to its application, antennas must comply with standardized requirements related to size, bandwidth, operating frequency, polarization, and gain. This paper presents an ultrawideband circularly polarized two-layer crossed-dipole microstrip antenna for S-band CubeSat applications using genetic algorithms optimization tools included in the 3D electromagnetic simulation software Ansys HFSS. The antenna is constructed on a 10 × 10 cm Cuclad-250 substrate with a back copper flat plane, located at λ/4 at 2.25 GHz operating frequency. The backplane with the exact substrate dimensions improves gain and reduces inside satellite radiation. Measured bandwidth defined by S11 at a −10 dB was higher than 1835 MHz with S11 = −24.68 dB at the central frequency of 2.25 GHz, while measured VSWR at the same frequency was 1.124. At 2.25 GHz, the maximum measured gain and the minimum measured axial ratio in the broadside direction were found to be 6 dBi and 0.22 dB, respectively. There are antenna simulations and measurements, as long as its fabrication guarantees application requirements that make it ready for prespace testing.
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