Abstract:The Dual-band technique based on Composite Right/Left Handed (CRLH) Transmission Lines (TLs) is improved in this paper. By properly choosing the parameters of the CRLH-TLs, the structure will yield electrical length and at the two operating frequencies. Employing this structure, an arbitrary dual-band microstrip Branch-Line Coupler (BLC) operating at 0.9GHz and 1.8GHz is achieved. Simulated and measured results demonstrate that when the rest of the parameters are unchanged, this BLC is significantly more compact compared to the CRLH approach proposed before, and as small as that of the conventional BLC based on quarter-wavelength TLs with single operating frequency at 0.9GHz. The proposed method can mitigate some of the problems between the dual-band work and the need for compact size, which is of great use in practical applications.