Abstract
Electromagnetic signatures of a low observable aircraft have been studied in VHF band. First of all, a three-dimensional model of the aircraft has been established for numerical computation. Then, monostatic and bistatic radar cross sections (RCS) have been calculated. The model of the aircraft is made by a curved surface, and commercial as well as in-house three-dimensional electromagnetic code which is based on the method of moments (MoM) is utilized to calculate the RCS. A characteristic basis function method (CBFM) and a multilevel fast multipole algorithm (MLFMA) have been applied to analyze electrically large objects. The change of the monostatic RCS is very large depending on the direction of the incident wave. The maximum value is about 42 dBsm at the top and bottom of the aircraft, and the minimum value is about −10 dBsm at the front and back of the aircraft. It is found that the bistatic RCS also changes dramatically depending on the direction of the incident wave. The direction of maximum RCS occurs around specular reflection, and the value of maximum RCS ranges from 27 dBsm to 43 dBsm. On the other hand, the direction of the minimum RCS occurs irregularly, and the value is in the level of −30 dBsm.
Highlights
Various low observable technologies for an aircraft have been utilized to reduce radar cross section (RCS) to avoid detection by radars and have become a vital design goal of a tactical aircraft
A characteristic basis function method (CBFM) [5,6,7] is applied to in-house MoM code, while a multilevel fast multipole algorithm (MLFMA) [8] which is built in the commercial software [9] is utilized
The range of monostatic RCS is very wide according to the direction of the incident wave
Summary
Various low observable technologies for an aircraft have been utilized to reduce radar cross section (RCS) to avoid detection by radars and have become a vital design goal of a tactical aircraft. The shape of the aircraft is the most important factor, and in general, low observable performance is targeted at a high frequency region, such as the X band [1]. It is clear that using lower frequency is an effective way of detecting long range target or low RCS objects if the RCS is theoretically known at that frequency region. The size of a modern low observable aircraft is comparable to the wavelength in VHF and UHF regions and the RCS will be in the resonant region, rendering effective detection of objects in the far distance. RCS of a low observable aircraft in the VHF band is calculated using rigorous numerical techniques, and variation of RCS depending on the polarization and direction of the incident wave is analyzed. After bistatic RCS is obtained as a function of the angle of incidence and polarization of the incident wave, the direction of the maximum as well as the minimum RCS has been found
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