{'fraction_non_alphanumeric': 0.015395894428152493, 'fraction_numerical': 0.0036656891495601175, 'mean_word_length': 5.594202898550725, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
An additional S-shaped structure for sensitivity improvement of coaxial probe for permittivity determination of low loss materials

Permittivity measurement of materials is important in microwave chemistry, microwave material processing and microwave heating. The open-ended coaxial line method is one of the most popular and effective means for permittivity measurement. However, the conventional coaxial probe has difficulty in distinguishing small permittivity variations for low loss media. In this paper an additional S-shaped structure is proposed for sensitivity improvement of a coaxial probe for permittivity determination of low loss materials at 2.45 GHz. The small permittivity variation can be distinguished due to field enhancement generated by the additional S-shaped structure. We studied the variation of reflection coefficient amplitude for three kinds of samples with different moisture content, within the probe at different insertion depths. We find that the conventional coaxial probe cannot distinguish small permittivity variations until the moisture content of materials reaches 3%. Meanwhile, the probe with the S-shaped structure can detect such small permittivity variations when the moisture content of samples changes by only 1%. The experimental results demonstrate that the new probe proposed in this paper is reliable and feasible.