Shape Memory Alloy-Based Frequency Reconfigurable Ultrawideband Antenna for Cognitive Radio Systems

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 x 58 x1.6 mm(3) 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 degrees with a transformation temperature of 66 degrees 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 < 2 and S-11 < -10 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.