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The present work demonstrates a frequency reconfigurable planar antenna with narrowband and ultra-wideband (UWB) characteristics for cognitive radio systems. The designed antenna has a dimension of $60\times 58\times1.6$ mm3 with a ground plane made of nickel–titanium (Ni–Ti) shape memory alloy (SMA). The antenna operates at a flat condition with frequency 1.46 GHz. Bending the SMA ground plane at an angle of 200° with a transformation temperature of 66 °C. The same antenna operates over 3.4–10.2-GHz UWB range. This is due to the SMA phase transformation between martensite and austenite via resistive heating/cooling. The insertion of rectangular slits in the antenna creates dual band-notched characteristics 4.7–5.1 and 5.3–6.0 GHz with VSWR $S_{{11 {}}} dB. This creates a different working frequency leading to frequency reconfiguration. Details about the proposed antenna have been discussed along with measured and simulation results.

A simple realization method for pattern reconfigurable antenna structures based on a shape memory alloy (SMA) is presented here. The proposed antenna is designed for automobile applications for safety, comfort, and commercial usage purposes. It is capable of communicating with neighbouring automobiles and also with roadside units. The patch of the antenna is made up of two-way SMA which comprises of two rectangular patches (patch 1 and patch 2) with antenna dimensions of 74 × 58 mm2. Upon exciting patch 1 through resistive heating, the antenna generates a tilted beam at an angle of 330°, and similarly for patch 2 at an angle of 30°, thus realizing pattern reconfigurability in the antenna. The operating frequency of the proposed pattern reconfigurable antenna is 2.68 GHz and it radiates with a reflection coefficient (S11) below − 10 dB. The desired pattern is achieved by training the SMA for the two-way effect. The prototype of the proposed antenna has been designed, fabricated, tested, to validate the experimental results and finally performance have been studied.

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.