Compact Dual-band 90◦ Couplers with Cus- Tomizable Power Division Ratios Utilizing Scrlh Transmission Lines

Novel dual-band 90◦ couplers with arbitrary power division ratios using simplified composite right-/left-handed (SCRLH) transmission lines (TLs) are proposed. With a degree of freedom in the structural parameters, a SCRLH stub can easily be tailored to imitate a conventional 90◦ section at two arbitrary frequencies with different characteristic impedances, making the resulting couplers with customizable power division ratios, as well as ensuring the size miniaturization and element realizability. To validate our idea, 90◦ couplers operated at 2.45/5.2 GHz with various power division ratios are designed and fabricated using microstrip technology. Good agreement is achieved between the simulated and measured results, justifying that the SCRLH configuration provides a new way of implementing compact dual-band 90◦ couplers with arbitrary power split ratios.