Abstract

The paper presents design of monopole arm microstrip spiral antenna that operates in the range of 2.93 to 7.25 GHz. The antenna is fed by an SMA connector from side, which is connected to a monopole i.e. main arm of spiral antenna. This monopole has a width of #x1D740;#x1D740;#x1D488;#x1D488;/4, which provide impedance matching thereby avoiding the need of balun for spiral antenna. To achieve enhancement in multiple band response, two designs have been proposed. The effect of increasing the number of turns of a spiral antenna is demonstrated here. The antenna is fabricated on FR-4 substrate with dielectric constant of 4.3 and loss tangent of #x1D739;#x1D739;=0.025. The designed antenna when tested, is working in 8 frequency bands ranging from 2 to 8 GHz providing the total bandwidth of 1.4 GHz. This multiple band antenna is suitable for upcoming cognitive radio systems.