Single-Sideband Time-Modulated Phased Array

Abstract

A new in-phase/quadrature (I/Q) complex modulation technique to realize single-sideband time-modulated phaseonly weighting on an array antenna is proposed. Based on modulating rectangular pulses and trapezoidal pulses, the theories of generating a scanning beam at the single positive sideband are presented. It was found that using trapezoidal pulse modulation can obtain excellent performance in power efficiency and undesired sideband level than using rectangular pulse modulation. Unlike conventional time-modulated antenna array where each array element is connected to a RF switch, in the proposed scheme, each element is connected to an I/Q channel modulator which is composed of two Wilkinson power dividers, two RF switches, two 0/π phase shifters in RF channels, and one π/2 fixed-phase shifter in the control circuit. By properly controlling both the phase shifters and the switches in time domain, the single-sideband modulation can be realized with the uniform amplitude and variable phase in frequency domain. The I/Q modulator acts as a phase shifter and can be used to form a phased array. In this paper, the main efforts have been paid to find the pulse sequences to suppress the spurious bands. To validate the proposed technique, simulated results of an eight-element single-sideband time-modulated linear array obtained from the array factor and full-wave analysis are reported. In the case of using rectangular pulses, the power efficiency of the scanning beam is 91.47% and the peak level of the highest undesired harmonic is −13.98 dB. In the case of using trapezoidal pulses, the best values can reach 99.79% and −27.98 dB.Index Terms-In-phase/quadrature (I/Q) complex modulation, phased array, single-sideband time-modulated phase-only weighting, time-modulation (TM) technique.

Target Localization Based on Intermodulation Feedback for Multisine Wireless Power Transmission Using a Time-Modulated Array

“…The TMA can be classified as one kind of unconventional phased array by adding a group of RF modulators in antenna channels. Traditionally, the modulator is chosen as the RF switch [26]- [28], the variable gain attenuator (VGA) [29], [30], or complex modulation circuits to achieve specific function [20], [31]. From the reported researches, the rectangular pulse modulated TMA using RF switches has been adopted a lot in practical applications compared with the others thanks to its simple realization and easyto-control.…”

A multibeam subarrayed time-modulated linear array

“…The sideband radiations derived from the periodic time modulation need to be edited for beneficial purposes. Toward this aim, the effectiveness of the proposed method has been compared with the existing studies in the literature in terms of the beam scanning, SLL, SBL, and signal bandwidth limitations in the Table. To determine phase-only weights, the single-sideband (SSB) TMA using the rectangular and trapezoidal pulses was proposed in [33]. The beam radiation on the fundamental harmonic component with about -13 dB SLL has been obtained.…”

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

“…In this way, time modulation was applied —together with in-phase and quadrature (I/Q) modulation— to phased arrays in order to generate a scanning beam at the single positive sideband [55]. Time modulation was considered, jointly with retrodirective techniques, to synthesize coaperture antenna arrays [56] and also to obtain time-invariant spatial-fine-focusing beampatterns in frequency diverse arrays [57].…”