Microwave ground level detection sensor

This paper describes the design and testing of a microwave sensor developed to detect ground level through growing sugar cane. The ultimate purpose of this sensor is to automate the height adjustment of the base-cutter on mechanical sugar cane harvesters. A transmission type sensor that measures the amplitude of an electromagnetic wave propagating from one side of the row of cane to the other, is shown to be best suited to this application. The optimum operating frequency range is found to be C-band between 2.6 and 4 GHz. This frequency range is found to offer a good compromise between the need to use frequencies lower enough to be reasonably insensitive to the growing cane while still allowing the antennas to be physically small enough to be easily mounted on a cane harvester.