Fiber-remoted 96-GHz radar system

High-precision imaging technology and its application are highly demanded for the enhancement of civil security. They are used to help prevent major incidents in railways or airports. In these applications, both small object detection and high-range resolution are key features. As far as the detectable target size is concerned, a high-frequency carrier is indispensable in radar systems. However, a radio signal with millimeter-wave (high frequency) suffers from large atmospheric attenuation. For example, the attenuation coefficient at 90 GHz is estimated to be 1 dB/km, while it is less than 0.1 dB/km in microwave bands [1]. Thus, the radar signal will have to originate from an area close to the target. Setting up a radar system with a synthesizer close to the target might not be desirable because a high-precision electrical synthesizer is generally large and consumes high energy. Radio-over-fiber (RoF) technology, used to transport the signal over optical fibers, is a promising candidate to deliver the millimeter-wave signal to the suitable point over a low-loss optical fiber cable. Radars utilizing the RoF technology have already been reported; however, digital signal processing in remote radar heads was required to reduce large transmission data [2, 3].