Compact Single-/Dual-Band Planar Crossovers Based on Strong Coupled Lines

Three compact planar crossovers based on strong coupled lines loaded with open stubs are proposed in this paper. Two conventional coupled lines loaded with different electrical wavelength open stubs are used to realize the single/dual passband. The center frequencies of the three planar crossovers can be adjusted over a wide frequency band by changing the even-/odd-mode characteristic impedance of the coupled lines and the characteristic impedance of the open stubs. Three compact planar crossovers located at 1.78, 1.88, and 1.02/2.98 GHz are designed and fabricated for verification. The theoretical and measured results are in good agreement and show good in-band performances.