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A new technique for suppressing the sideband levels in time-modulated linear arrays (TMLAs) is presented. The technique utilises the fixed bandwidth of the radiating elements of the array to act as bandpass filters to suppress the out-of-band harmonics generated by the time-modulation process. The approach is combined with a new element switching sequence that can be designed to redistribute the dominant harmonic components of the TMLA to predetermined frequencies that are outside the bandwidth of the array elements. The proposed technique does not require the use of complicated optimisation procedures to generate the TMLA switching sequences and is applicable to a TMLA configured to synthesise arbitrary low sidelobe patterns. Numerical results are presented to illustrate the proposed approach by considering a 16-element array of patch antenna elements designed to provide a - 30 dB Chebyshev sidelobe level radiation pattern.
Introduction: Conventional approaches to array pattern synthesis generally involve applying a set of amplitude weights to the elements of the array. Such an approach can be used to successfully realise low sidelobe radiation patterns conforming to a prescribed function, for example a Chebyshev or discrete Taylor weighting function. However, it is also possible to apply an equivalent, time-average weighting function to the elements of an array by simply switching the elements of the array 'on' and 'off' in a predetermined and controlled manner. Such an approach was first proposed by Shanks and Bickmore in the late 1950s [1] and later developed by Kummer et al. [2]. Time-modulation has several advantages over conventional amplitude weighting techniques. First, it provides an adaptive system in that the time switching sequence applied to the elements of the array is under software control and can be changed in 'real-time' to provide control of the array radiation pattern. Secondly, recent work...