Parabolic Reflectarray Antenna to Generate Multiple Beams in Dual-Frequency and Dual-Circular Polarization

Frequency-Selective Beam-Shaping Technique to Provide Equal Beam Coverage Using Reflectarray Antennas for Dual-Band Multispot Satellites

“…The phase distributions at 19.7 and 29.5 GHz have been analytically computed to generate a focused beam in θb = 12º, φb = 0º [20]. The antenna has been defined to provide the gain and beamwidth commonly required in communication satellites in Ka-band [13].…”

“…10). The antenna was firstly presented in [13] without additional phase corrections, providing a maximum gain of 50 and 53 dBi at 19.7 and 29.5 GHz, respectively.…”

“…The cell has been analyzed in a periodic environment by a homemade tool based on the SD-MoM under any angle of incidence [21], [25], experimentally validated in [18], [19]. The rotation of the printed elements is adjusted to split the orthogonal CP beams focused by the parabolic antenna surface, generating two beams per feed [12], [13], [19]. The arcs and dipoles provide an independent operation by VRT in Tx and Rx, respectively [23].…”

“…This condition is fulfilled by adjusting the lengths of the rotated arcs at 19.7 GHz and dipoles at 29.5 GHz. The phase ϕX' provides an additional common phase-shift for both orthogonal CP's, which was not used in [13], so the dipole lengths were optimized to introduce a constant ϕX' distribution at 29.5 GHz (ϕX' = 0°, ϕY' = −180°). Now, this degree of freedom will be used to implement the proposed technique, by randomly choosing some 180º shifted cells (ϕX' = −180°, ϕY' = 0°) at 29.5 GHz.…”

“…A hybrid solution was presented in [10], based on a parabolic reflector covered with reflectarray elements that correct the beam squint and beam shaping in Rx, without any effect in Tx frequencies, by a simultaneous optimization of all the reflectarray elements on the antenna. Some reflectarray antennas have been proposed for multispot satellites in Ka-band, replacing the four onboard reflectors by only two Tx/Rx reflectarrays [11]- [13], by generating twice the number of beams than a conventional reflector. Nevertheless, these reflectarrays also must reduce the directivity of the Rx beams.…”