Frequency shifting using corrugated coupled microstrip lines

Coupled microstrip lines are used to suit a wide variety of circuit applications like directional couplers and filters. Another coupled line variety called corrugated coupled microstrip modifies the phase velocities of the two eigen-modes in the direction of propagation. This property can be used in the design of fase shift couplers, i.e., the coupled wave is phase shifted with respect to the input wave, and in the design of filters with suppression of spurious response at twice the frequency center. The property cited above is used here to discuss other important feature of the corrugated coupled microstrip lines that doesn´t appear in the conventional literature: frequency shift. The simulations performed in an appropriate software show that the idea works very well and can be useful in microwave devices like duplex, diplex and multiplex.