Proximal-field sensing is introduced as an integrated sensing scheme for the in situ characterization of far-field radi- ation properties of integrated radiators, and the proximal-field radiation sensors (PFRSs) are proposed as the tools to enable this capability. These sensors are integrated on the same dielectric substrate as the transmitting antennas and extract the existing information in the excited substrate modes and use it to predict the far-field radiation properties in real time based on in situ field measurements in the close proximity of the transmitting antennas, without any need to use additional test equipment, remove the antenna from its operating environment, or interrupt its operation in a wireless system. The functionality of this sensing scheme is verified on both PCB and IC platforms through the implementation of two proof-of-concept prototypes, and different aspects of the electromagnetic and electronic design of the PFRS integration with integrated radiators are investigated.