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1IntroductionNowadays, Earth observation satellites which observe climate change, land-surface change, and so on are required to transmit high-capacity observation data in a short time in addition to expanding the observation area and enhanc-ing the observation resolution, because immediate emer-gency observation has come to be considered important when natural disasters occur. JAXA plans to apply the frequency of the Ka band to a transmission system between Earth observation satellites and ground stations to fulll the demand for high-capacity data transmission[1]. e allocable bandwidth of Ka band (25.5-27 GHz) is four times wider than that of X band (8.025-8.4 GHz), which has never been used in the JAXA Earth observation satel-lites, and the Ka band can be expected to improve transmis-sion speed dramatically. However, the Ka band radio waves largely decay due to rainfall. erefore, it is required to improve satellite transmission performance (Eective Isotropically Radiated Power: EIRP) to always keep the RF link quality. On the other hand, the Earth observation satellite needs to control the antenna pointing direction to the ground station as time advances, so it is hard to adopt a large antenna which improves the EIRP, because antenna pointing control is restricted by simultaneous data trans-mission. For this reason, it is essential to adopt a high-power amplier which contributes to the EIRP improvement. However, the power consumption and heating value of on-board devices are strictly limited, so the devices must operate in a non-linear region with high power eciency. erefore, if using the higher-order modulation scheme which has high spectral eciency, the transmission quality may deteriorate. Accordingly, we have studied the applica-tion of a signal distortion compensation technique which linearizes the non-linearity of the amplier in advance on the satellite side.is paper reports the experimental conrmatory result that the signal distortion compensation technique on the premise of satellite on-board can control the non-linearity existing in a satellite communication path and improve the transmission quality.2Types of non-linear compensation circuitse distortion compensation methods are divided into two main groups: feedback systems and feedforward sys-tem. Feedback systems are not suitable for Ka band com-munication systems handling a wideband signal, because the operating bandwidth is limited due to the eect of the group delay characteristic for the feedback loop. On the other hand, feedforward systems have superior wideband performance. To materialize a feedforward system by ana-log circuits has the disadvantages that the amplier for compensation requires linear operation to avoid degrada-tion of transmission characteristics due to the distortion 3-9 Experiment of Non-Linear Compensation on Satellite ChannelMitsuhiro NAKADAI and Masanobu YAJIMA JAXA plans to use the Ka band (communication system) in order to increase the amount of data transmission between low earth orbit satellites and ground stations. In this paper, we report on the experimental result that the transmission characteristic can be improved by removing the nonlinearity existing in the satellite communication path by Digital Pre-Distortion (DPD) technology based on satellite installation. Moreover, by applying the DPD technique, we report the result that the difference between the degradation amount of the return channel in the ground station during 1.8 Gbps transmission and the degradation amount of the satellite return channel in the 28 GHz band can be reduced to about 0.4 dB. As a result of these experiments, we show that it is possible to estimate the distortion characteristics on the communication path from the receiving constellation and to correct the DPD parameters.1453 Ultra-High-Speed Satellite Communication Technology