Efficient Three-Element Binomial Array Antenna

Abstract

The three-element uniform linear binomial array is one of the simplest array antennas. They do not have good selectivity due to the low number of the elements and the simple amplitude coefficients distribution: 1-2-1. The three-element binomial uniform array factor pattern has no side lobes when the inter-element distance is less than or equal to the half of the wavelength. In this paper, an approach for improvement of the binomial array antenna selectivity is studied. In this regard, a space-phase function with S-shaped graph is offered. The proposed function is not periodic that leads to array factor pattern without side lobes. Function's parameter changes the gradient of the function graph and the array factor selectivity, respectively. An appropriate approach to eliminate the dependence between the array factor selectivity and inter-element distance is applied. As a result, a linear array of three elements with binomial coefficients is obtained. The array antenna possesses the following properties: The elements can be located at any distance which is greater or equal to half of the wavelength without changing the array factor pattern; the array factor has no azimuthal side lobes; the array factor main lobe may be arbitrarily narrow; the direction of the main lobe can be changed without selectivity deterioration or side lobes occurrence. Analytical expressions for the phase function, array factor and array antenna parameters are proposed. The described array antenna properties are examined with two Matlab® simulations.