Efficient and Effective Full-Wave Analysis of the Instantaneous and Average Behaviors of Time-Modulated Arrays

Abstract

An efficient and effective full-wave analysis of the instantaneous and average behaviors of time-modulated arrays (TMAs) in the presence of mutual coupling effects is proposed. It has high computation efficiency for the optimization design of TMAs, especially for non-uniformly spaced TMAs. The proposed approach, using the in-array mutual impedance to describe the effect of mutual coupling, is based on a closed-form mutual impedance expression and a correcting procedure. The closed-form is used to calculate the mutual impedance between two isolated elements in which the effect of the parasitic elements is ignored. Then the correcting procedure which only requires the knowledge of the isolated element input impedance and the mutual impedance of two isolated elements is used to obtain a corrected in-array mutual impedance, in which the interactions between the antennas in the array configuration is involved. Because it makes use of the surface mode currents to calculate the mutual coupling effects, the currents induced on the parasitic elements are naturally involved. Therefore, the corrected in-array mutual impedance is a good approximation of the real one. In addition, the impedance variations can occur in phase-scanned TMAs due to mutual coupling effects, resulting in a significant fraction of the incident power being reflected known as mismatch losses. Based on the proposed approach, an introduced phase-scanned TMA makes use of SP3T switches and optimized time sequences for the element feed to reduce the mismatch losses in comparison with a conventional phase-scanned TMA. To validate the accuracy and efficiency of the proposed approach, examples of the optimization design of uniformly and non-uniformly spaced time-modulated patch arrays for different scenarios are presented. All the results obtained from the proposed approach are given and compared with those from the commercial software.

Time Modulated Arrays: From their Origin to Their Utilization in Wireless Communication Systems

“…In this sense, and in order to evaluate rigorously some nonlinear performance aspects of TMA as a radiating system (e.g., the effects of mutual coupling between elements), a full-wave computation of the radiated far field was addressed by Masotti et al in [38] by properly developing a multi-domain computer aided design platform. Aligned with this research topic, a full-wave analysis of the instantaneous and average behaviors of TMA is available in [39]. …”

A general look on time-modulated antenna array

“…In addition, it is also found that there is no closed-form available for the design of TM arrays in which the mutual coupling effects are completely involved. Recently the full-wave analysis based on a closed-form mutual impedance expression and a correcting procedure, focusing on the optimization design of practical uniformly and non-uniformly spaced TM patch arrays was proposed [32]. Based on the proposed full-wave analysis, performance in instantaneous scan reflection coefficient of a conventional phase-scanned TM array can be obtained.…”

“…The comparison shows that the computational efficiency of the proposed method is very high. The full-wave analysis presented in [32] is applicable not only for TM patch arrays but also for any other type of TM arrays and it will be much more useful for dealing with the large linear or planar TM arrays, especially for large non-uniformly spaced TM arrays. Full-wave analysis for many practical TM related systems is underway.…”

A review of microwave electronically scanned array: Concepts and applications

“…The most common methods are to change the phase, frequency and working time of the signals, which can realize phased arrays, 12 frequency scanning arrays, 13 focused aperture arrays, 14 and timemodulated arrays. 15 For conventional phased arrays, phase shifters are key components to tune the phase to realize electronic scanning, but they are still the most complex and expensive parts of systems. There have been some alternatives to phase shifters to achieve phase changes in the array, such as passive beamforming network, 16 series-fed arrays, 17 steerable parasitic arrays, and so forth.…”

“…Different parameters of the operation signal can be set to realize various types of electronically scanned arrays. The most common methods are to change the phase, frequency and working time of the signals, which can realize phased arrays, 12 frequency scanning arrays, 13 focused aperture arrays, 14 and time‐modulated arrays 15 …”