Magnetic Induction IC for Wireless Communication in RF-Impenetrable Media

Abstract

Demands on fresh water and energy are ever increasing. An coil, from which the data is extracted. The communication underground network of low cost, low power soil properties range for magneto-inductive systems is short. Therefore, one sensors gathering valuable information such as soil salinity, sensor may transmit its data to a nearby sensor, which in turn nitrogen levels, and volumetric water content over a large transmits this received data, along with additional data, to a region would allow for precise and efficient automated soil sensor near to it but unreachable by the first sensor. The and water management. Using current technology, sensors network data is relayed in a multi-hop fashion until it reaches a are buried at a desired depth and relay soil information to the desired destination for further processing. surface by means of a physical link such as a cable, antenna, or the protruding embodiment of the probe itself. This physical Unlike RF, MI transmission will not be affected by soil type, link to the surface is easily damaged by agricultural composition, compaction, or moisture content, and will require equipment, which prevents or inhibits sensor deployment in less power and lower operating frequencies than RF the middle of a field. This physical surface link is also transmission. This novel technology will enable the unsightly and obtrusive, making use of these sensors in athletic large-scale deployment of underground wireless soil sensor fields or home lawns undesirable. In order to create an networks. This technology may also be used in medical, underground network of sensors, they must be connected military, underwater, or other RF-impenetrable environments, together via multiple cables, or wirelessly on the surface via where large scale sensor deployment would be advantageous. expensive RF transmitters. A prototype of a MI transmitter has been constructed using The authors are developing a novel method for underground commercially available parts. A receiver is currently under communication in wireless sensor networks using magnetic construction. The red line in Figure 1 shows the predicted induction (MI). Each soil properties sensor in the network voltage induced on a receiving coil according to prototype will be equipped with a MI transmitter, using a small parameters. The blue line shows the induced voltage ferromagnetic coil or an embedded RFID-type coil as an measured across a stand alone receiving coil (no amplification antenna. The soil information, superimposed upon a carrier or demodulation circuitry attached) due to the field established frequency, excites the coil, establishing a quasi-static by the prototype transmitter. The authors will integrate this electromagnetic field. This field induces a voltage in a technology into a low power, low cost, single chip solution to nearby MI receiver, similarly equipped with a ferromagnetic be interfaced with soil or other sensors.