SBIR-STTR Award

A large area absorbing screen is proposed to measure the power density of millimeter wave signals. The screen has metalization that is 188ohms/square so that at least 50% of the incident millmeter wave power is absorbed by the screen. The power density that is absorbed by the screen is read via an infrared camera. It is expected that the time constant of the absorbing screen will be much faster than the previously used cabon loaded teflon screens so that near real time measurements can be carried out. Calibration of the power density as it relates to the infrared image is acomplished via a millimeter wave radiometer. The radiometer can calibrate both CW and pulsed sources. The absorbing screen is novel and is based upon work carried out on frequency selective surfaces. The approach achieves a wide bandwidth that extends from 26GHz to 100GHz. The sensitivity of the approach is anticpated to be better than 1mw per square centimeter. RADIOMETER, MILLIMETER WAVES, LARGE AREA ABORBING SCREEN, MILLIMETER WAVE DOSIMETRY, FREQUENCY SELECTIVE SURFACE

RCA Consultants, Inc. and our team mate the Mission Research Division is proposing a 24 month program to design, fabricate and test a large area (~ 8X8 square meter) absorbing screen to accurately measure the incident millimeter wave power density (w/cm2) over the 25 to 100GHz frequency region. The design will be suitable for both laboratory and field measurement. The approach can easily be extended to frequencies as high as 1000GHz The dosimetry measurements will be carried out in near real time (~1.5sec). The sensitivity of the measurment is better than 1mw per square centimeter with a linear dynamic rang of 30dB (1W per square centimeter) befor the induced temperature begins to saturate with increasing power density. Accrate dosimetry above 40dB dynamic range is possible via calibration. The screen has been designed with little or no difussion and the incident power density profile will be the same as the induced temperature profile. The design is modular and dosimetry screens as small as 2x2feet and as large as 8x8feet are possible. Larger screen areas are possible by adding mor basic modules. The sensitivity of thescreen is beetr than 1mw per square centimeter

Keywords:
near real time dosimetry, millimeter waves, antenna patterns, time constant, diffusion, IR imaging, Mylar absorber