Comments on Frequency Diverse Array Antenna Using Time-Modulated Optimized Frequency Offset to Obtain Time-Invariant Spatial Fine Focusing Beampattern

TL;DR

This paper critiques recent time-modulated frequency diverse array (FDA) designs for spatial focusing, clarifying the correct equations and definitions to achieve true time-invariant and focused beampatterns.

Contribution

It provides a corrected and extended equation system for time-modulated FDA designs, addressing inaccuracies in previous definitions of time.

Findings

Identifies errors in previous FDA time definitions

Provides corrected equations for time-invariant focusing

Clarifies the conditions for achieving focused beampatterns

Abstract

In the recent papers [1-4] including above paper time modulated frequency diverse arrays (FDAs) have been presented to obtain time invariant spatial patterns. The presented FDAs in [1-3] have the feature of time-invariant spatial focusing which means they have a constant maximum in a time duration, T, at a point with desired range, r, and angle, {\theta}. In [4] the pattern is time invariant, yet, not focused. However, in this communication it is indicated that the patterns are obtained using incorrect definition of time in some equations. The equation system of [3] is explained here that can be extended to [1, 2, 4], explicitly.