This paper investigates the maximum read range which can be achieved by linear time-variant chipless sensor based on polarization modulation. Analytical expression of the differential RCS is derived as a function of the polarization scattering parameters of the transponder. Expressions are valid for all scatterers and allow to determine the maximum read range considering polarization modulation. From the derived expressions, a linear time-variant sensor based on a dipole array is designed to maximize the read range. Simulation and measurement confirm the approach and achieve a read range of 20 m in real environment. This read range can outperform by a factor of 50 the one classically obtained with chipless RFID.