Millimeter-wave radiometer based on electro-optic modulation

A millimeter-wave radiometer using electro-optic modulation and photo-detection is presented. The millimeter-wave energy collected by the antenna is transferred to the sidebands of the optical carrier by an electro-optic modulator, and then transmitted through the optical fiber. Fiber Bragg grating filters are subsequently used to suppress the optical carrier and a photo-detector is used to detect the energy in the remaining sideband. The output signal of the photo-detector is detected by a lock-in amplifier to improve the sensitivity. The energy conversion efficiency and noise characteristics in the millimeter-wave signal processing are discussed. The millimeter-wave detection experiment based on this technique was implemented using a 50 GHz millimeter-wave source. The conversion efficiency and the noise equivalent power were measured. The methods for improving the sensitivity were proposed. A millimeter-wave radiometric detection system was designed. The detection experimental results show that this millimeter-wave signal processing method is effective for millimeter-wave radiometer.