The feasibility of developing a photonics-based real-time high-power-microwave (HPM) near-field mapping system is to be investigated. The system is intended to contain multiple non-intrusive near-field sensors so that it can simultaneously detect undistorted versions of broadband HPM electric- and magnetic-field transients over a desired field-mapping area. The system will be able to take advantage of existing photonic and instrumentation technologies in order to have a measurement bandwidth that extends up to current-day limitations of around 100 GHz. The field sensors, their supporting structure, and their signal-transmission paths will be designed to introduce negligible distortion on the radiators and HPM fields being measured.
Benefits: The R&D undertaken as a result of this program will dramatically impact the state-of-the-art of photonics-based electromagnetic-field sensors, not only from the standpoint of technological specifications such as the real-time detection bandwidth and dynamic range, but also from the perspective of the cost-effective implementation of a large number of simultaneously interrogated field sensors. Information obtained from a nonintrusive, photonics-based, microwave-transient mapping system will identify, for the first time, the undistorted characteristics of pulses of high power microwave radiation in the near field of antennas and in real time. As serious consequences can arise due to the fact that the electromagnetic fields have not yet diverged in this region, and thus the strength of the radiation can be extremely high, precise knowledge of the microwave-transient temporal characteristics, magnitudes, and spatial distributions will significantly aid the study of the human effects of these fields. Commercially, products resulting from the development of a photonics-based, real-time, high-power-microwave near-field mapping system will address numerous military and civilian applications. They will assist in research applications, for instance through measurements of strong electromagnetic fields that could appear both at the surface of humans positioned in the near field of radiators, as well as at the interior of human surrogates (i.e., phantoms). For development applications, nonintrusive fiber-based sensors may be used in a small-area substitute for the very large areas required for far-field-beam measurements for example by placing a sensor array in the near field of prototype antennas in order to extract the amplitude and phase of the emerging radiation before computing the propagation into the far field. As a diagnostic instrument, the photonic-sensor array could be used to periodically calibrate antenna arrays, since the noninvasive probes can be placed close enough to individual array elements that they can quantify deficiencies in magnitudes and/or undesired phase shifts in the field outputs of distinct unit cells without disturbing their operation.
Keywords: Antenna, radiation, human effects, electromagnetics, optics, sensor array, noninvasive sensing
