Millimeter wave and/or microwave imaging systems and methods including examples of partitioned inverse and enhanced resolution modes and imaging devices

A method of detecting changes in a parcel or package, the method comprising:

• calculating first image data of one or more items inside the parcel or package at a first time and place using a first array of millimeter wave transmitting and receiving antennas located externally of the parcel or package, the first image data based at least in part on scattered signals responsive to interrogation by at least one of the first array of millimeter wave transmitting antennas;
• calculating second image data of the one or more items inside parcel or package at a second time and place using a second array of millimeter wave transmitting and receiving antennas located externally of the parcel or package, the second image data based at least in part on scattered signals responsive to interrogation by at least one of the second array of millimeter wave transmitting antennas;
• processing the first image data and the second image data;
• and
• indicating whether the one or more items inside the parcel or package has or have changed at least in part in response to the difference between the first image data and the second image data.