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Abstract
A sensitive microwave detector based on carrier wave zero-balance technique for abstracting human microwave cardio-graph (MCG) is established. More than eight hundred MCGs under various conditions are collected with this apparatus. It is shown that all the MCGs present a strong dependence on those conditions, such as the position of the receiving antenna, persons under testing, and their postures. Careful analyses of the experimental results show that the operation mechanism of this type of detector should be attributed to both the Amplitude Modulation (AM) and Phase Modulation (PM) of the heartbeat to the scattering field, instead of well-known Doppler effect, even though almost a similar apparatus is used.