A novel parallel-series feeding network of microstrip patch arrays with composite right/left-handed transmission line (CRLH-TL) for millimeter wave applications is proposed. Since there is no inserting phase shift in the patch elements with CRLH-TL feeding structure, the inherent pattern shift resulting from the traditional parallel-series feeding network is removed. Besides, because of the simpler structure and the shorter length of the CRLH-TL feeding network, the antenna array is of higher gain than that with the conventional parallel feed network. The integral feeding networks of 2-dimensional microstrip patch arrays with may be divided into arrays fed by parallel or parallel-series feeding networks. Commonly, parallel-series fed arrays are more efficient than only parallel fed arrays, because the length of feed transmission line and the number of discontinuities in the feeding network can be minimized [1]. Nevertheless, the parallel fed arrays have a well controlled aperture distribution, and the parallel-series fed arrays have an inherent radiation pattern shift. In this paper, a new CRLH-TL unit with microstrip structure is presented [2]. Also, a novel feeding network is proposed, in which the traditional transmission lines between the elements in the parallel-series fed arrays is replaced by the CRLH-TLs (Fig. 1). By adjusting the characteristics of the CRLH-TL to make no phase shift introducing in each microstrip elements and to get perfect match to the microstrip elements so that the higher gain of the antenna array can be obtained without radiation pattern shift (Fig. 2).
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