Improved Estimation of Impulse Response of Reflector based IRAs using Conjugate Gradient Method

Abstract—Impulse response of an ultra wide band (UWB) antenna is one of the most important parameters, which in turn helps in deriving other important antenna parameters like gain, antenna factor etc. The excitation input pulse to the antenna is a Gaussian pulse of finite width, hence to get antenna impulse response, far zone electric field data needs to be deconvolve with the input excitation of the antenna. There are no pure closed form deconvolution methods that are widely accepted and numerically stable. Reflector based half impulse radiating antenna (HIRA) is analyzed using finite difference time domain (FDTD) method. Estimation of impulse response is done on both the analysis and measured input output data using both time domain as well as frequency domain methods. This paper focuses on the improvement of the timing characteristics of impulse response like late time ringing and group delay. Time domain technique like conjugate gradient method shows clear advantage over the Fourier transform method, especially for measured data. The estimated impulse response using conjugate gradient method removes imperfections of input signal and the late time ringing is reduced to significantly low level.