Effects of the Even and Odd Phase Velocity Separation on the Bandwidth Limitation of Nonuniform Line Microstrip Couplers

Frequency response of nonuniform line micros trip couplers is given by using a second order theory applied for the even and odd signals which have unequal velocities. This condition leads to finite isolation which becomes worse as the velocity separation increases. A modified structure to equalize the even and odd mode phase velocities is analyzed by a finite difference method applied to hybrid waves.