A Polarization Switched, Narrowband, RF Probe System Using a VCSEL Optical Feed

Microwave detection techniques requiring high penetration are often reliant on the use of centimeter wavelengths. Systems such as these can also potentially be capable of being highly portable as well as being suitable for use in harsh and demanding environments. Further advantages of these systems are that they can also be cost effective, offer low levels of RF exposure, and are of potential use in short range nondestructive evaluation applications. Lack of resolution is overcome by the use of a phase contrast technique. Using antennas specifically developed for this purpose, the use of polarization adds a further measurement plane. The 5-GHz crossed patch design described here utilizes commercially available RF switches for ease of implementation and exhibits typically 22-dB isolation between each orthogonal-linearly polarized plane. This allows independent E-plane measurements to be conducted from a common point. Phase sensitive information is preserved by a low power optical bidirectional transmission system based around directly modulated vertical cavity surface emitting lasers. The use of these techniques in combination enables a high resolution, dual plane scanning system capable of remote operation in demanding environments.