A Design of Analog Complex Correlator for Millimeter- Wave Temperature Measurement

A high-sensitivity multiplicative analog complex correlator is designed to meet the medical requirement of measuring the human body temperature by adopting millimeterwave radiometer technology. The analog complex correlator adopts phase shifter to calibrate the phase deviation of the two input signals in order to improve the precision of temperature measurement. Compared with the traditional scheme of the diode square law detector, this paper tries to adopt quadrature demodulator to accomplish the detecting function. The result indicates that the detection sensitivity improves 3.478 times and the bandwidth increases to 5.5 GHz, in addition, the structure of the circuit is simplified. The experimental results show that the sensitivity of the analog complex correlator can reach 173 mV / dBm when the input power is in the range of 7dBm to 8dBm. When the human body temperature is in the range of 330ºC to 43º C, the precision can reach ± 0.331 º C. Having the phase error, offset error and gain error calibrated by software algorithm, the analog complex correlator can reach the level of medical measurement.