Investigation on Frequency Reconfigurability of a Microstrip Patch Antenna Using a Ni-Ti Shape Memory Alloy for an Automatic Fire Sprinkler System

This paper presents frequency reconfigurability of a microstrip patch antenna using a nickel-titanium (Ni-Ti) shape memory alloy (SMA). It comprises a radiating patch made up of Ni-Ti SMA. It is characterized by differential scanning calorimetry, four-probe method and x-ray diffraction in order to evaluate transformation temperatures, electrical resistivity and different phases present in the material, respectively. Currently, a fire sprinkler system consists of a “wet alloy” which will expand when heated initially and then breaks allowing water to sprinkle onto the fire. The present work uses a two-way Ni-Ti SMA which is used to actuate the fire sprinkler system, triggers a sound alarm and is also able to send a message via SMS to the administrator. A microstrip patch antenna is designed, fabricated and measured for reflection coefficient, radiation pattern, and antenna gain at flat and bent configurations. The antenna operates at 2.4 GHz in the flat condition and 3.8 GHz in the bent configuration. This patch antenna can be used in fire alarms which actuate at 66°C and stop the fire without causing much damage. Unlike a conventional fire alarm system, proposed fire sprinkler designed with a Ni-Ti SMA can be reused several times.