Dual-band Y-junction power dividers implemented through artificial lines based on complementary resonators

In this work, dual-band Y-junction power dividers based on impedance inverters with composite right/left handed (CRLH) characteristics are presented for the first time. The inverters are either implemented through complementary split ring resonators (CSRRs) or through complementary spiral resonators (CSRs). By using the left handed and right handed frequency bands of the inverters, the required phase shifts, -90deg and +90deg, at the respective operating frequencies, f₁ and f₂, can be obtained, whereas the characteristic impedance can be set to the necessary value to achieve effective input matching (Z_o=35.35Omega for a 1:2 power splitter). The main advantages of these devices are: (i) dual-band operation with arbitrary f₂/f₁ ratio, due to the possibility of engineering the dispersion diagram of the impedance inverter; (ii) compact size, owing to the small electrical size of CSRRs or CSRs; and (iii) full compatibility with planar technology, since neither lumped elements nor vias are used. The reported examples are two dual-band Y-junction power dividers operative at the mobile GSM bands (f₁=0.9 GHz, f₂=1.8 GHz). The area occupied by the CSR- and CSRR-based divider is 0.11lambda times 0.09lambda and 0.14lambda times 0.12lambda, respectively (where lambda is the guided wavelength at f₁) and their measured characteristics are good.