Monopulse time-modulated antenna array using iterative Fourier technique

The iterative Fourier technique (IFT) is applied to design monopulse radar tracking system using time-modulated linear antenna array (TMLA). IFT is used to modify the time sequences of the radio-frequency switches connected to the antennas to generate sum and difference patterns with suppressed interference-plus-noise signal while constraining the power losses associated with side-band radiation (SBR). The time modulation allows quick and precise control of the excitation distribution, which increases the tracking accuracy. To obtain best angle sensitivity, the article computes the tradeoff among side-lobe level (SLL), half power beam width, directivity, and dynamic efficiency. The approach is proved successful to handle several design constraints through adaption in radiation domain as well as in aperture domain. Authors illustrate additional representative TMLA examples where the time sequences of the selected elements are prefixed to enhance the dynamic efficiency and directivity for different SLL and side-band level (SBL). Application of IFT saves the computational cost significantly with respect to existing state-of-the-art optimization techniques. Introduction of the symmetric switching sequences simplifies the feed network greatly. The proposed design solution is validated with a fabricated TMLA prototype consisting of two time-switched printed dipoles with microstrip via-hole balun at 2.45GHz. Copyright (c) 2016 John Wiley & Sons, Ltd.