capacity enhancement of ad hoc networks using a new beamforming scheme based on espar

this paper proposes a new smart antenna beamforming scheme based on electronically steerable parasitic array radiator (espar). the proposed method is capable of providing better capacity compared to the conventional espar. the termination of each antenna element in this structure comprises a pin diode in addition to a varactor. using pin diode besides the varactor provides more degrees of freedom which lead to better interference suppression. moreover, in the proposed method the required tunable impedance range of the varactors is dramatically reduced. the optimal values of the tunable loads in each simulation scenario repetition are attained iteratively using steepest descent method with a maximum cross correlation coefficient criterion. simulation results show that the proposed scheme outperforms the conventional espar technique with respect to interference suppression and capacity enhancement. to further validate the beamforming ability of the proposed method, a testbed was fabricated. measurement results confirm that the proposed method can provide an acceptable beamforming capability close to the simulated beam.