A microwave radiometer with additional pulse-width modulation of the reference signal is described. The pulse-width modulation is performed in the low-frequency unit using resistive attenuators with different division factors of the reference signal. The radiometer implements a modification of the null measurement method when the automatic control is attained by varying duration of a pulsed signal. Changing the radiometer low-frequency circuit to the null-balance mode allows us to use high-frequency units of any chopper radiometer with symmetric modulation.
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