Microwave Imaging Using Noise Signals

A new method of active incoherent microwave imaging is presented that uses noise signals and spatial frequency sampling. Building on interferometric spatial frequency sampling arrays developed in radio astronomy, active incoherent microwave imaging utilizes the transmission of noise signals to implement the first active imaging method that samples in the spatial frequency domain. In comparison to passive microwave imaging systems, active incoherent imaging requires receivers with far less sensitivity, and thus less overall cost. We present the theory behind the imaging technique and show experimental results from a 5.85-GHz system imaging in one and two dimensions. For 1-D images, the transmitter consisted of two noise generators, while the receive array was a synthesized linear array with elements placed in 1λ increments with the widest spacing of 15λ. For 2-D images, the transmitter consisted of three noise generators, while the receive array was a synthesized T-array with elements placed in 0.5λ increments. We demonstrate the reconstruction of 1-D and 2-D scenes consisting of spherical reflecting targets, using only 25 MHz of signal bandwidth and 10 μs of integration time, both of which are an order of magnitude less than passive microwave and millimeter-wave imaging systems.