High throughput S-band transmitter for Earth observation applications

The high throughput S-band transmitter (HSTX), designed for establishing a high data rate downlink to the Ground Station (GS), is part of ALMASat-EO payload for Earth observation. The equipment operates in the 2.4 GHz free license frequency band. It has been designed and optimized to meet the requirements of small satellite platforms for which small volume, low mass, low power consumption and low cost are basic parameters. Moreover, the overall design follows the Software Defined Radio (SDR) paradigm, that is the capability to adapt link parameters (modulation, final data rate, channel coding) to the channel condition during the mission. In this way a maximization of the downlink throughput is obtained, offering a key advantage for data transmission from satellite in Low Earth Orbit (LEO), generally limited by the geometry of the link and the short duration of the contact passes. The main advantage arising from this architecture is the link reconfigurability. The presented architecture is based on two different module: an analogue back-end (TXBE) designed for 2.4 frequency band, and a digital processing unit (DPU), based on an FPGA platform, that could easily be re-used at higher frequencies (X- and Ka-band