Modulated Antenna Array Research Articles

SIMULATION OF TIME MODULATED LINEAR ANTENNA ARRAYS USING THE FDTD METHOD

Time modulated linear antenna arrays consisting of printed dipoles above a ground plane are simulated using the flnite- difierence time-domain (FDTD) method. The FDTD method brings great convenience to the investigation of the time domain responses of the time modulated arrays. In conjunction with the near-to-far fleld transformation in time domain, the far-fleld transient response can be computed to explain the physical essence of difierent time sequences. By employing the discrete Fourier Transform (DFT) and the frequency domain near-to-far fleld transformation, the radiation patterns at the frequencies of interest are obtained and are compared with the measured results. Simulation results show that the FDTD method is an efiective and accurate approach for the full-wave simulation of time modulated antenna arrays.

Comparative Study of Low Sidelobe Time Modulated Linear Arrays with Different Time Schemes

Low sidelobe antenna arrays usually require tapered excitations with very high dynamic-range ratios, which is often one of the difficulties encountered in practical implementation. By introducing an additional degree of freedom – time – in the design, time modulated antenna arrays have very low excitation dynamic-range ratios, even in the case of uniform excitations. In this paper, the feasibility of using different types of time modulation schemes to design low sidelobe time modulated linear arrays is discussed. The time modulation schemes examined in this study include variable aperture sizes (VAS), unidirectional phase center motion (UPCM), and bidirectional phase center motion (BPCM). It is shown that all three types of time modulation schemes can be used to synthesize a specific low sidelobe patterns, despite different array characteristics such as sideband levels and reduction in gain. Experimental results of a prototype 16-element printed dipole linear array confirmed the theoretical results.

Modulating retro-reflector as a passive radar transponder

A novel retro-reflecting transponder is described. The structure is a modulated antenna array which reflects an interrogating signal back towards its source. It may be realised as a printed circuit and has low power requirements because an RF transmitter is not employed, unlike conventional transponders.