Trough line designed phase shifters offer improved reliability over coaxial structure phase shifters. In a trough line design, only the center conductor moves while the outer conductor remains stationary. This simplifies the construction and improves performance. Improved reliability has been exemplified through use in a number of military applications. The trough line design approach allows for size reduction, making higher frequency operation possible.
The trough line design approach has been extended by adding multiple "U" sections to achieve the multiple "trombone” effect.