Abstract |
A new class of a dual mode microstrip fractal resonator is proposed and
developed for miniaturization of the dual band bandpass filter. The perimeter of
the proposed resonator is increased by employing fourth iteration T-square
fractal shape. Consequently the lower resonant frequency of the filter is
decreased without increasing the usable space. The self similarity of the usable
structure enables it to produce the two degenerate modes which are coupled using
the proper perturbation technique. The shorting pin is placed at the null in the
surface current distribution at the center of the resonator. This shorting pin
is coactively coupled to the resonant circuit of the resonator, effectively
coupled to the lower degenerate mode and reduces the lower edge band resonant
frequency. By adjusting the resonator dimensions and the size of the shorting
pin, the resonant frequency and the out-of band rejection around the
transmission bands can be controlled to meet the design requirements. The
simulated response of the designed filter has two transmission bands; the first
band is from 2.34-3.65 GHz with resonant frequencies at 2.47 GHz and 3.55 GHz,
the second band is from 4.37-5.324 GHz with resonant frequencies at 4.5 GHz and
5.13 GHz. In the pass bands, the group delay is less than 0.65 ns. The proposed
filter can be applied to WLAN (2.4 GHz and 5.2 GHz) and WiMAX (3.5 GHz) and
Bluetooth and ZigBee (4.9 GHz). |