Microwave sensing for nondestructive detection, diagnosis, and imaging has been of great interest for many decades. Sensing methods are commonly classified as either probe-based or antenna-based according to near-field or far-field applications, respectively.

Various resonant probe-based approaches have been reported previously and these have promoted the capabilities of single-probe detectors. However, most of these existing approaches still require raster scanning for information acquisition, so it is impossible to achieve large-scale sensing in one shot. Alternatively, leaky-wave antennas with high-scanning-rate beam steering can be utilized for sensing applications, but drawbacks still exist and limit their utility. Firstly, as traveling-wave structures, leaky-wave antennas feature...[ Read more ]

Microwave sensing for nondestructive detection, diagnosis, and imaging has been of great interest for many decades. Sensing methods are commonly classified as either probe-based or antenna-based according to near-field or far-field applications, respectively.

Various resonant probe-based approaches have been reported previously and these have promoted the capabilities of single-probe detectors. However, most of these existing approaches still require raster scanning for information acquisition, so it is impossible to achieve large-scale sensing in one shot. Alternatively, leaky-wave antennas with high-scanning-rate beam steering can be utilized for sensing applications, but drawbacks still exist and limit their utility. Firstly, as traveling-wave structures, leaky-wave antennas feature large working bandwidth and cannot be applied to narrow-band scenarios. Secondly, in most of the literature, leaky-wave antennas can achieve high-scanning-rate beam steering at the cost of large structure loss, which significantly reduces the radiation efficiency of the antenna and hence lowers signal-to-noise ratio (SNR) and sensing quality. To address the challenges of using single resonant probes or leaky-wave antennas, probe arrays and antenna arrays based on coupled-resonator networks are proposed in this thesis.

For the first contribution, multiple-probe sensors based on coupled resonators are pro-posed. Both the extraction approach based on coupling matrix theory and the design principle minimizing condition number have been illustrated. The two-port and one-port sensor have been designed and numerical examples together with experimental results have been provided to validate the technique. Compared with existing single probe designs, the multiple-probe structure has the advantage of significantly reducing scanning time by enabling the one shot approach.

For the second contribution, a new approach to design extremely high scanning rate beam steering antennas is proposed. The feeding structure for the frequency-steering antenna based on coupled resonators has been demonstrated. Two examples with 50 MHz and 100 MHz bandwidths are designed to illustrate the proposed technique. Experimental validation was also provided for the 50 MHz bandwidth example, which significantly enhance the scanning rate without sacrificing radiation efficiency.

For the third contribution, conventional coupling matrix theory is introduced into the sensing application. Modifications to the coupling theory and its subsequent integration with formulations for sensing and imaging provide new approaches to the design of sensing arrays.