Digital Potentiometer Controls Phase Shift: 02/15/96 EDN-Design Ideas 

Digitally Controlled Phase Shift: Altering the phase response of a signal without changing its amplitude characteristics is commonly performed using an all pass filter. This circuit implementation is well suited to using digital potentiometers as the controlling element.  

Phase Shift Radio Direction Finder:

Phase Shifter Yields Slope Polarity Detection: 03/14/96 EDN-Design Ideas 

Phase Shifter:

Scheme Extends DDS Phaseshift Resolution: 08/05/99 EDN-Design Ideas  / PDF contains multiple circuits - scroll to find this circuit.