Passivity limitations on absorption properties of low-scattering objects

We analyze the constraints governing absorption and scattering of arbitrary sensors or receiving antennas. Our findings bring forward interesting physical limitations on the amount of accessible absorption in a low-scattering sensor and suggest practical ways to achieve efficient designs for noninvasive sensors, based on the application needs. A subwavelength dipole antenna is studied as a numerical demonstration of our theory in the subwavelength limit.