Time‐variant focused range‐angle dependent beampattern synthesis by frequency diverse array radar

Abstract

The frequency diverse array (FDA) radar has been extensively studied due to its unique range-angle dependent beampattern. Time-invariant spatial patterns have been reported for FDAs proposed so far. However, some recent studies indicate that the patterns obtained by using these methodologies neglect the time-range or frequency-phase relationship, and the definition of time in some equations are misinterpreted which results in erroneous conclusions. Taking the time-variant property of FDA beampatterns into consideration, in this study, the authors propose a short range FDA radar to generate a timevariant focused range-angle dependent transmit beampattern, where chirp waveform with multi-carrier FDA architecture is used. Both the fixed and time-modulated frequency offsets are considered to analyse the proposed FDA radar. The frequency offset employed across each element is generated by chaos sequence and sine function. By compensating the propagation delays of signals, the transmitted signals sum up constructively to focus on the desired range-angle sector only at a specific instant of time. Numerical results are implemented to verify the validity of the proposed schemes.

Accurate Theoretical Models for Frequency Diverse Array Based Wireless Power Transmission

“…The authors in [30][31][32] applied different frequency offsets and complex weighting factors to design time-invariant range-angle dependent beampattern for the FDA-WPT. However, as highlighted in [39][40][41][42][43], it is theoretically impossible to achieve a time-invariant beam focusing with FDAs. Therefore, the FDA-WPT systems designed in [30][31][32] are actually inappropriate in practice.…”

Frequency diverse array radar with non-uniform array spacing based on sigmoid function

“…In addition to the abovementioned numerical limits, random frequency offsets should be employed to realize a beampattern with a single maximum at the target location. The non-uniform frequency offsets alter the synchronization between linear increasing frequency offsets and element spacing to avoid range-angle coupling in the FDA beampattern [7,22].…”

“…where w m denotes the complex weight associated with the m-th element, and T represents the transmitted pulse duration. The overall signal arriving at an arbitrary point P (r, θ) in the far-field can be expressed as [1][2][3][4][5][6][7][8][9];…”

“…The concept of FDA radar with progressive incremental frequency offsets was first proposed by Antonik et al in 2006 [6]. This progressive frequency shift in radiated signals enable the FDA radar to realize rangeangular beamforming and auto-scanning feature without using the expensive phase-shifters [7]. However, the beampattern of a conventional FDA radar is coupled in range and angle dimensions.…”

“…However, the beampattern of a conventional FDA radar is coupled in range and angle dimensions. As such, employing non-uniform array or random frequency offsets can decouple the FDA beampattern into range and angle dimensions [7][8][9].…”