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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.

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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.