Synthesis of a Biasing circuit for a reconfigurable WiMAX Antenna (RWA) at 2.3 GHz

Abstract

This research focuses on identifying the values of capacitors and inductors of a PIN diode biasing circuit to generate an optimum performance for a 2.35 GHz WiMAX antenna. The optimization involves the testing of a new range of capacitors between 47 and 330 pF and inductors from 18 to 56 nH on a fabricated reconfigurable WIMAX antenna (RWA). Advanced Design System (ADS) software is deployed to obtain simulation results using the touchstone block implementation technique. Four sets of the capacitor—inductor values are proposed based on the reflection coefficient (S11) and transmission coefficient (S21) to possibly achieve the best performance of the RWA. The four sets are; set 1: C = 47 pF, L = 56 nH, set 2: C = 100 pF, L = 56 nH, set 3: C = 150 pF, L = 56 nH and set 4: C = 330 pF, L = 56 nH. It is discovered that by simulation, set 2 produces the optimal S11 and S21 compared to the other combination sets. The resulting S11 and S21 is -26.61 and -0.046 dB, respectively. To further verify this, a complete set of biasing circuit consisting of a PIN diode, two 56 nH inductors and two 100 pF capacitors are integrated on the fabricated RWA. It is found that the combination of these components a PIN diode, produced a maximum gain of 6.28 dBi and a reflection coefficient of -15.08 dB at 2.35 GHz. Moreover, the these lumped component values also enabled the RWA to channel WiMAX signals directionally at the broadside, depending on the user locations.