In some embodiments, receive antenna 122 may be configured to receive RF signals having a first center frequency. The received RF signals may be transformed by signal transformation circuitry 124 to obtained transformed RF signals having a second center frequency different from (e.g., a harmonic of) the first center frequency. Such processing and associated and other architectures of the signal transformation circuitry 124 are described herein including with reference to 
In some embodiments, each of the transmit and/or the receive antennas on an interrogator may be directional antennas. This may be useful in applications where some information is known about the region of space in which the target device is located (e.g., the target device is located in front of the interrogator, to the front left of the interrogator, etc.). Even if the target device is attached to a moving object (e.g., an arm of an industrial robot, a game controller), the movement of the target device may be constrained so that the target device is always within a certain region of space relative to the interrogator so that using directional antennas to focus on that region of space increases the sensitivity of the interrogator to signals generated by the target device. In turn, this increases the distance between the interrogator and target device at which the micro-localization system may operate with high accuracy. However, it should be appreciated that in some embodiments, the antennas on an interrogator may be isotropic (omnidirectional), as aspects of the technology describe herein are not limited in this respect.