<title>ROSCAM: a 95-GHz radiometric one-second camera</title>

Abstract

The ability to obtain millimeter wave images under a variety of environmental conditions, such as rain, snow, fog, smoke, dust, etc., has numerous DoD as well as commercial applications. The demonstrated ability to look through doors, walls and clothing has recently extended potential millimeter wave applications to contraband detection and surveillance within buildings. Though the phenomenology supports the generation of high quality millimeter wave images, present-day frame time capabilities limit the use of millimeter wave cameras. Several solutions to frame time reduction are currently being investigated within government and industry. Two popular approaches include: (1) Electronic scanning focal plane arrays (FPA); (2) Mechanical raster scanning of a single antenna beam. One significant difference between the two approaches noted above is the number of receiving channels required. This is important because camera cost is driven by the number of receiver channels used in a camera, as well as the added complexities associated with inter-channel gain stability. There are a number of applications that do not require a motion picture capability. Images obtained sequentially at a nominal rate of one per second would satisfy the needs of a wide range of applications. It is evident, however, that the motion picture quality of a starring FPA may ultimately reduce the market for one-second cameras. In the interim, the one-second camera fills an important need. The goal of the Radiometric One Second Camera (ROSCAM) investigation is to demonstrate a practical millimeter-wave imaging (MMWI) camera, with a frame time of approximately one second. The approach combines a high-speed mechanical raster scanning antenna system with a single-channel radiometric receiving system. For baseline comparison, it is assumed that the scene is comprised of 1,000 pixels, each sampled for one millisecond, to generate a single frame in one second. The ROSCAM is based on combining a state-of-the-art radiometric receiver with a high-speed mechanical antenna scanning mechanism. One purpose of the initial measurement program described here, was to determine the ability of an existing high-speed raster scanning antenna to meet ROSCAM antenna requirements, specifically, a Field of View (FOV) consisting of 1,000 pixels scanned in a frame time of one second. A by- product of this investigation was the determination of the number of radiometer channels needed to generate a motion picture with a similar FOV. This paper includes: (1) Description of the ROSCAM Breadboard; (2) ROSCAM Performance Capabilities; (3) Measurement Results; (4) Conclusions.