In some embodiments, each of transmit antenna 114 and receive antenna 116 may be a patch antenna, a planar spiral antenna, an antenna comprising a first linearly polarized antenna and a second linearly polarized antenna orthogonally disposed to the first linearly polarized antenna, a MEMS antenna, a dipole antenna, or any other suitable type of antenna configured to transmit or receive RF signals. Each of transmit antenna 114 and receive antenna 116 may be directional or isotropic (omnidirectional). Transmit antenna 114 and receive antenna 116 may the same type or different types of antennas.
In some embodiments, transmit antenna 114 may be configured to radiate RF signals circularly polarized in one rotational direction (e.g., clockwise) and the receive antenna 116 may be configured to receive RF signals circularly polarized in another rotational direction (e.g., counter-clockwise). In some embodiments, transmit antenna 114 may be configured to radiate RF signals having a first center frequency (e.g., RF signal 111 transmitted to target device 104) and the receive antenna may be configured to receive RF signals having a second center frequency different from (e.g., a harmonic of) the first center frequency (e.g., RF signal 113 received from target device 104 and generated by target device 104 in response to receiving the RF signal 111).
In some embodiments, transmit antenna 114 and receive antenna 116 are physically separate antennas. In other embodiments, however, the interrogator 102 may include a dual mode antenna configured to operate as a transmit antenna in one mode and as a receive antenna in another mode.