Discussion on the functions of Hadamard phase pattern in millimeter wave imaging

Coherent imaging always suffers from speckle noise, which makes it challenging to extract useful information from the image. The Hadamard technique, based on statistical optics, is expected to deal with speckle at millimeter wave frequencies. In this paper, we will discuss three possible functions of Hadamard phase pattern from the wave point of view. It will be applied to the practical example of active millimeter wave imaging. The aim is to give an appropriate evaluation of this technique, and especially to explore the possibility to move it down to millimeter wave frequencies. It will be shown that Hadamard phase pattern may work as a spatial filter, transfer intensity more accurately and decrease speckles.