Passively Modulating Reflective Tags for Tracking Insects

Advances in animal tracking have revolutionised ecology in a large number of fields, but usually require the animal under study to wear a radio transmitter.

Due to the amount of energy required to transmit data wirelessly even over a short distance for any length of time, these are too large and heavy for smaller animals and insects to carry.

This is a challenge, as understanding insect behaviour is a major requirement for maintaining good ecology and crop production in agriculture and broader landscapes. The only previously demonstrated approach is to use harmonic radar. The advantage is only the tag will produce this doubled frequency, meaning other clutter in the environment is ignored.

However, it suffers from very poor conversion efficiency with lower power, between -20dB to -50dB, meaning a transmitting radar must produce signals with powers over 10kW to cover a range of around 100m. Due to prohibitive costs, there are no harmonic radar systems in use today.

This project will utilise the emerging technology of reconfigurable metamaterials, combined with spread spectrum techniques. to overcome this problem.

First, the tag will be designed to scatter energy very efficiently in all directions using metamaterial technology, increasing its visibility to radar.

Second, instead of converting the incoming signal to a new frequency, a tag will modulate the signal in phase using a pseudorandom sequence.

The receiving radar signal will then look for this reflected signal and correlate with the sequence, making the signal appear stronger than a simple reflection and allowing the receiver to discern between background clutter and the insect tag.

The switching signal will consume very little power, meaning the tag can be lightweight while still operating for the lengths of time required. This will enable low cost radar to be used to study insect behaviour, allowing vital ecological work to be undertaken.