A simple, inexpensive device has been conceived for shifting the phase of a signal in a feed line of a scanning-beam microstrip antenna in order to change the direction of the beam. Heretofore, phase shifters used for this purpose have been relatively bulky and expensive.
The phase shifter and the overall scanning antenna are made more compact than they otherwise would be by integrating the feed line and the phase shifter. The feed line in this case is a dielectric waveguide made of a ceramic that is characterized by low loss at a wavelength of the order of a millimeter. The waveguide feeds the microstrip antenna through a slot.
The design of the device exploits the fact that the phase velocity, and thus the phase, of a signal propagating along the ceramic waveguide, can be varied by perturbing dielectric/air/conductor boundaries. In particular, the variation in phase and thus the scanning ability of the beam is effected by rotating a cam on top of the ceramic waveguide. The phase varies with the gap between the ceramic waveguide and the cam.
The development of this device is at the prototype stage. The one major source of difficulty in fabrication and use is that the waveguide/cam gap is less than a tenth of a millimeter and must be controlled accurately.
This work was done by XiaoDong Wu, Robert Knox, Kenneth Gilliam, and Dawei Li of Epsilon Lambda Electronics Corp. for Glenn Research Center.
Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Commercial Technology Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135.
Refer to LEW-16912.