I. Introduction
Sign language is currently a primary communication manner in deaf-and-mute communities worldwide, more than 460 million. Translating varieties of signs into the patterns acknowledged by computers can be significant in improving access to the latest electronic products for the deaf-and-mute community. As a visual language, sign language contains hand gestures, body movements, and even signers’ facial expressions. The state-of-the-art work of sign language translation has been extensively investigated by using wearable devices like gloves and mechanomyogram signals [1] . These methods focus on capturing the features of the movement but are less user comfort for signers. Computer vision based [2] sign translation is touchless and could recognize both statistic signs and dynamic signs by image and video. However, the accuracy is heavily impacted in a low light environment. Therefore, our motivation in this paper is to allow deaf-and-mute community to have a new touchless way of translating their sign language into the compatible text form of the current electronic devices. To our knowledge, electromagnetic (EM) wave extensively investigated in touchless hand gesture recognition can overcome the drawback of low light and reduce the risk of privacy leakage. A Doppler radar sensor can emit EM wave into space and receive echo signals reflected by the target. The representation of signs can be achieved by processing the micro-Doppler signatures from the radar echo signals to characterize different sign motions. Therefore, this paper discusses the feasibility of representing sign language based on a new pattern, EM wave.