This paper presents a novel frequency coded chipless RFID tag, which exploits the backscattered co-polarized and cross-polarized responses from a tag illuminated with a linear polarized wave. Consequently, the tag-ID is configured in two orthogonal planes. The frequency notches are encoded in the co-polarization plane and the re-radiation peaks are encoded in the cross-polarization plane. Therefore, the co/cross-polarizing Notch/Peak modulation scheme presents a novel criterion for maximizing the coding capacity of the chipless RFID systems. Moreover, the cross-polarized response enhances the tag detection in a real environment. The proposed tag and the associated physical modulation scheme are validated using EM simulations and measurements.