Reflectarray to Generate Four Adjacent Beams per Feed for Multispot Satellite Antennas

This contribution describes a design concept of a reflectarray antenna to produce four adjacent beams per feed through the simultaneous use of polarization and frequency discrimination. The feed position is computed to produce two adjacent beams in different frequencies accounting for the beam squint effect, which ensures a minimum phase variation between the phase distributions at the two frequencies. The other two beams in orthogonal polarization are generated by implementing in the reflectarray a different phase shift for each polarization. This contribution presents the design, manufacturing, and measurement of a 43 cm demonstrator that operates at transmit frequencies in the Ka-band. The proposed concept can be suitable for multiple spot-beam satellites in the Ka-band, enabling a reduction in the number of antennas and feeds needed to provide the multispot coverage.

I. Introduction

The existing high throughput satellites (HTS) in the Ka-band produce between 50 and 100 overlapping spot beams with a four-color frequency and polarization reuse scheme [1]. The conventional reflectors employed on board the satellite cannot provide closely spaced beams (around 0.56° separation), and typically, four reflectors operating in transmission (Tx) and reception (Rx) are required to generate a four-color coverage (using two frequencies and two polarizations) with overlapping spots, one reflector per color.