As shown in FIG. 6B, target device 650 comprises a substrate 652 having a receive antenna 654 and transmit antenna 656 disposed thereon. The target device 650 further comprises a semiconductor die 658 having signal transformation circuitry integrated thereon. The signal transformation circuitry integrated with the semiconductor die 658 is differentially coupled to antenna receive 654 via lines 659a and 659b. The signal transformation circuitry on the semiconductor die 658 is differentially coupled to transmit antenna 656 via lines 660a and 660b. Substrate 652 may be of any suitable type described herein including with reference to substrate 505 of FIG. 5A and, for example, may comprise a printed circuit board (PCB) and/or be manufactured from any suitable printed circuit board materials or other materials capable of supporting propagation of RF signals in a desired range of frequencies. In some embodiments, the substrate 652 may include a frequency selective surface and/or absorbent coating to reduce harmonic coupling between the receive antenna 654 and the transmit antenna 656. Examples of frequency selective surfaces and absorbent coatings are described herein. In the illustrative embodiment of FIG. 6B, the substrate 652 may be 4 mm×3.5 mm.
