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A practical implementation of a miniaturized crossover is presented using negative-refractive-index transmission-line (NRI-TL) metamaterial lines. NRI-TL metamaterial theory has demonstrated that by loading a conventional transmission line with lumped LC elements, a large phase shift per-unit-length can be achieved. Employing this technique, the conventional microstrip transmission lines in a three-section branch-line coupler crossover are replaced with 90° NRI-TL lines, and thus a compact NRI-TL crossover with an area 47 times smaller than the area of its conventional counterpart is demonstrated. Measured results demonstrate that the proposed NRI-TL metamaterial crossover exhibits a −10 dB |S11| bandwidth of 33% and a |3 dB| |S31| bandwidth of 26% around 1 GHz.

This paper presents a compact reconfigurable phase-shifter based on negative-refractive-index transmission-line (NRI-TL) metamaterial unit cells. Two inter-switchable NRI-TL metamaterial unit cells are collocated within the same board area, and can be reconfigured based on the biasing polarity of embedded PIN diodes to provide two discrete phase states. The PIN diodes are located on the shunt branches of the metamaterial line in order to reduce losses in the direct signal path. Design limitations in terms of return loss and insertion loss are discussed in relation to the two phase states. A proof-of-concept module with a size of 17.8 × 21.6 mm2 is designed at 1 GHz, with measured insertion phases of −14.5° and +58.5° in the two phase states leading to a differential phase shift of 73°, while exhibiting insertion losses of 1.43 dB and 0.89 dB, respectively. The combined bandwidth for which the reflection coefficient in both states remains simultaneously below −10 dB is 0.46 GHz (46%), from 0.83 GHz to 1.29 GHz.