MISCELLANEOUS MICROWAVE COMPONENTS 



5S5 



10-15] 



angles to the dielectric plate. As a consequence, the emerging wave is 

 circularly polarized. The sense of circular polarization will be reversed if 

 the quarter-wave plates is rotated 90° from its indicated position. Other 

 forms of microwave quarter-wave pl'ates employ elliptical waveguide, 

 periodically loaded square waveguide, ^^ and capacitive pins in circular 

 waveguide.*^ 



Half-Wave Plates^ or A 180° plates, resemble the quarter-wave plates in 

 construction but introduce a 180° phase delay difference. Two quarter- 

 wave plates having the same orientation are equivalent to a half-wave plate. 

 Because of the 180° differential phase delay introduced by a half-wave plate, 

 it will reverse the sense of rotation of a circularly polarized wave passing 

 through it, and if rotated about its axis will produce a continuous change in 

 phase of the circularly polarized wave, advancing or retarding the phase, 

 depending on direction of rotation. Such a device is often used as a con- 

 tinuous phase shifter,^^ although generally in conjunction with two quarter- 

 wave plates — the first to convert from linear to circular polarization, and 

 the second to convert back to linear polarization. The construction of a 

 commercial continuous phase shifter^^ of this type is shown in Fig. 10-27. 



Fig. 10-27 Phantom View of a Commercial Continuous Phase Shifter. (Courtesy 



of Hewlett-Packard Company. Reprinted from Reference 46 by permission of The 



Institute of Radio Engineers) 



43A. J. Simmons, A Method of Producing Broadband Circular Polarization in Square Wave- 

 guide, NRL Report 4286, Washington, D.C., January 1954. 



^<A. J. Simmons, "A Compact Broad-Band Microwave Quarter-Wave Plate," IRE Proc. 40, 

 No. 9 1089-1090 (1952). 



«A. G. Fox, "An Adjustable Wave-Guide Phase Changer," Proc. IRE 35, 1489-1498 (1947). 



«E. F. Barnett, "A Precision X-Band Phase-Shifter," IRE Trans. PGI-4, 150-154 (October 

 1955). 



