Numerical simulations on beam and/or null forming performance of ESPAR antennas

Abstract

SUMMARYThe radiation pattern of the ESPAR antenna is controlled by variable reactances loaded to its passive elements. In this paper, the effects of the number of elements and the variable range of the reactance value on the beam and null forming capability are studied by simulation using the method of moments. It is found that a beam with a directivity of more than 8 dBi and a null of less than -40 dBi can be scanned independently in all directions when the number of elements is more than 5 and the reactance value range is ±50 Ω. The reactance range of ±50 Ω is needed for simultaneous forming of a single beam of more than 5 dBi and a single null of less than -30 dBi, while ±100 Ω is needed for simultaneous forming of a single beam of more than 5 dBi and multiple nulls of less than -15 dBi. The direction of the beam and null can be close as the number of elements is increased. The input impedance of the feed element is also studied and the standard return loss of a seven-element antenna is found to be 15.8 dBi.

Electronically steerable parasitic array radiator antenna

“…The number of possible candidate combinations of the reactance values increases exponentially with the number K. It is not realistic to derive the values of the objective functional for all combinations. A method of reducing the required time for searching an optimum solution is the Monte Carlo approach [39,40]. This algorithm requires simple programming.…”

“…In the calculations, a half-wave dipole model [40] is used with the following structural parameters. …”

Beam‐adjustable planar arrays composed of microstrip antennas

“…However, in adaptive antennas and DBF, the received signal processing system is so complex that the system cost is generally very high. On the other hand, ESPAR antennas have variable radiation characteristics with low cost and low power consumption [1,2,5]. But their profile nature is not sufficiently low due to the use of wire antennas as array elements.…”

“…As wireless communications systems become more sophisticated, the demand for antenna systems controlling the radiation pattern electronically is increasing [1,2].…”

Basic studies on aperture for adaptive antenna with switched loads of parasitic elements

“…A similar approach is the adaptive null scanning antenna, called the electronically steerable passive array radiator (ESPAR), where the reactive loads connected to the parasitic elements are continuously varied [5,6]. In the ESPAR antenna, the objective function is the coefficient of correlation between the received signal and the reference signal.…”