Low Profile Harmonic Radar Transponder for Tracking Small Endangered Species

Abstract

Fragmentation of threatened species' habitat attributable to anthropogenic activity is a major concern. Understanding these animals' dispersal ecology and range utilization can greatly aid in designing preserves for their conservation, but this data is extremely difficult to obtain for populations of small animals. Presented here is a study miniature passive harmonic radar tags which allow the tracking of an endangered snail species without adversely affecting the tagged subjects. Whip antennas were found to be problematic through snagging and interference with snail activity. Alternative low-profile planar antennas were also tested, with bow-tie related antenna forms providing reasonable (up to 7 ft) detection range.

Transponder Designs for Harmonic Radar Applications

“…Direct matching based designs have also found many other implementations for harmonic transponders, and some of these are illustrated in Figure 4. For instance, the transponders designed in [19,20,30,31,41,42] are based on this technique. The complexity of the implemented antennas varies from simple loop or dipole geometries ( [19] and [30], resp.)…”

Signal processing for harmonic pulse radar based on spread spectrum technology

“…Harmonic radars have been used in behaviour study of small insects [1–8]. In the articles [5, 7–9], the harmonic radars were used to track the flight path of bees and investigate behaviours of insects at low altitude.…”

“…Several methods are used to range the distance between the radar and targets. In [2, 4], the distance is obtained through measuring the received signal strength corresponding the transmitted power. This approach is simple, but with low ranging accuracy, since the strength of received signal is easily affected by environment and system loss.…”

Respiratory monitoring using a doppler radar with passive harmonic tags to reduce interference from environmental clutter

“…Harmonic tags have been successfully used earlier for uniquely separating a target from the environment [1], [2]. A harmonic tag consists of a tag antenna with a strongly non linear element at its port.…”