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Backscatter communication enables wireless communication at a power consumption orders of magnitude lower than conventional wireless communication. Instead of generating new RF-signals backscatter communication leverages ambient signals, such as WiFi-, Bluetooth- or TV-signals, and reflects them by changing the impedance of the antenna. Backscatter communication is known as a short-range communication technique achieving ranges in the order of meters. To improve the communication range, we explore the use of a tunnel diode as an amplifier of the backscattered RF-signal. We developed the amplifier on a PCB-board together with a matching network tuned to give maximum gain at 868 MHz. Our work demonstrates that the 1N3712 tunnel diode can achieve gains up to 35 dB compared to a tag without amplification while having a peak power consumption of 48 μW. With this amplifier the communication distance can be increased by up to two orders of magnitude.

Over the past three decades, agricultural machinery has made the transition from purely mechanical systems to hybrid machines, reliant on both mechanical and electronic systems. A this transformation continues, the most modern agricultural machinery uses networked systems that require a network connection to function to their full potential. In rural areas, providing this network connection has proven difficult. Obstacles, distance from access points, and incomplete coverage of cellular connection are all challenges to be overcome. “Off the shelf” commercial-grade Wi-Fi equipment, including many products from Ubiquiti like the Bullet M2 transceiver and the PowerBeam point-to-point linking system, as well as antennas by Terrawave, Crane, and Hawking, were installed in a purpose-built system which could be implemented on a production farm. This system consisted of a tower-mounted access point which used an antenna with a 65^o beamwidth, and the test included distances up to 1150 meters in an agricultural setting with corn and soybeans. Some sensors were stationary and the other platform was a tractor following a path around the farm with both 8dBi and 15dBi gain antennas. Through all tests, throughput never dropped below 5 Mb/s, and the latency of successful connections never exceeded 20ms. Packets were rarely dropped and never accounted for a significant portion of all packet transmission attempts. Environmental effects like immediate precipitation, crop heights, recent rainfall, and ambient temperature had little or no effect on wireless network characteristics. As a result, it was proven that as long as line-of-sight was maintained, reliable wireless connectivity could be achieved despite varying conditions using microwave radiation. Network throughput was marginally affected by the change in free space path loss due to increased distance between the access point and the client, as well as travel by the mobile client outside the beamwidth of the access point. By enabling this coverage, it is hoped that the implementation of new agricultural technology utilizing a live network connection will progress more rapidly.