Digital Predistortion in High Throughput Satellites: Architectures and Performance

Abstract

The future of satellites lies in the deployment of high throughput satellites (HTS). Moreover, HTS will also play an important role in the up coming 5G mobile networks where HTS will provide services like disaster relief, remote automation, maritime services etc. However, the distortions caused by the on-board transponder filters and high power amplifiers (HPAs) reduce the overall performance of HTS. To increase the power and bandwidth efficiency, the transponder HPAs are often operated close to saturation and in multicarrier mode. In addition, the transponder filters are built with tighter guard bands to minimize the out-of-band (OOB) radiations. Such operation conditions introduce severe linear and non-linear distortions in the transponder’s output in terms of inter-modulation (IMD) noise, spectral regrowth, and memory effects. Digital predistortion (DPD) can effectively mitigate these distortions. This article proposes an on-board implementation of a ground-based state-of-the-art bandlimited memory polynomial (MP) DPD method to mitigate the aforementioned distortions. The authors stress on the fact that the on-board application of the proposed ground-based DPD makes it the most suitable DPD method for HTS. However, the focus of this article lies in the identification of the system parameters which effect the predistortion performance. To this end, the performance of the considered state-of-the-art DPD is thoroughly analyzed for varying uplink-signal, transponder and DPD specific parameters.

Keywords

• Bandlimited predistortion
• digital predistortion (DPD)
• high power amplifiers (HPAs)
• high throughput satellites (HTS)
• non-linear distortions
• on-board processors (OBPs)