A four-way broadband planar power divider

Includes bibliographical references (pages 53-54)A theory for a four-way broadband planar power divider which employs\ud coupled lines is developed. The resulting power divider is designed such that\ud the even mode impedance of four lines cut from a 50 ??? line of given width is\ud tapered to the desired output characteristic impedance values while still coupled. The coupled lines are then separated keeping the even mode impedances constant while tapering the odd mode impedance of each coupled line to the single line characteristic impedance desired at the output. The equations that\ud are developed for uncoupling the lines show that the even mode impedance can\ud be kept constant while tapering the odd mode impedance of each line. The odd mode impedance of each line in the coupled region has a different value. In general, the odd mode impedance is less than the even mode impedance. Tapering the odd mode impedance to equal the even mode impedance requires that the\ud lines separate to a distance infinitely far apart. Both types of impedances can\ud then be considered as the single line characteristic impedance. However, they\ud are sufficiently separated when the spacing between lines is about the same as\ud the ground plane spacing in stripline construction. The initial line width for the 50 ??? line is divided into four separate lines each having the same even mode impedance value of approximately 200 ???. The\ud even mode impedances of the lines are then tapered for a Chebychev reflection\ud response from the higher 200 ??? impedance value back to 50 ???. This is\ud accomplished by changing the widths of the lines and keeping the separation\ud spacing between lines the same. The lines are then uncoupled using the theory\ud developed in this thesis. The odd mode impedance values and corresponding\ud widths are not equal to one another in the coupled region of the power divider.\ud Consequently, the odd mode impedance of each line must be separately tapered\ud from the odd mode impedance at the output of the coupled region to the final\ud 50 ??? value. The frequency of operation was designed to be from 6 to 18 GHz with 12\ud GHz as the matching frequency for the isolation network