Assessment of a low-profile planar antenna for a wireless sensor network monitoring the local water distribution network

This study presents an assessment on the suitability of a low-profile planar antenna for a wireless sensor network (WSN) application monitoring the water supply at fire hydrants (FHs). The antenna must have a low profile so that it can be mounted on the FH lid; it must have an omnidirectional radiation pattern so that it can communicate with base stations at low elevations; and it must operate in the 2.4 GHz industrial, scientific and medical (ISM) band. Measurements show that for the majority of the 2.4 GHz ISM band, the antenna has a return loss of at least -10 dB and efficiency greater than 60%. For the FH WSN assessment, the antenna was deployed as a transmitter mounted on the FH lid above the underground FH chamber and a vertically polarised monopole antenna mounted on a mast at various specified heights above ground level was used to measure the received power as a function of distance. The path loss results were compared with those from a previous deployment, where the FH antenna was located in the FH chamber, and it is found that using the low-profile antenna reduced the path loss by at least 10 dB over the measured transmitter and receiver separation.