Wideband Near-Zone Radiative System for Exploring the Existence of Electromagnetic Emission From Biological Samples

This article reports on a wideband near-zone radiative system operating from 1 to 50 GHz for examining the possibility of electromagnetic emission from a community of bacteria in a petri dish or any other distributed sources confined in a small focusing area. The system includes a dual-polarized signal collector, a Dicke switch, broadband low-noise amplifiers (LNAs), and a precision spectrum analyzer. The signal collector is composed of a quadruple-ridged horn-type structure of dimensions {\lambda }_{L} \times {\lambda }_{L} \times 1.6\,\,\lambda _{L} (where {\lambda }_{L} is the wavelength at the lowest frequency) having two orthogonal probes. The provision of a dielectric cone along the horn central axis allows for collimating the waves in the focusing area over the entire bandwidth. Therefore, the signal collector acts as a field concentrator to provide a uniform field distribution across the focusing area (source location). The entire structure is designed to be EM-shielded and free from resonance. It can effectively exclude outside interference while maintaining a uniform collection of the electromagnetic spectrum.