Comments on "Analysis and design of a circular disc 3-dB coupler" [with reply]

In a recent paper, [see ibid., vol. 42, p. 1437-42, 1994], Bialkowski and Jellett discussed the design of a broadband 3-dB quadrature hybrid. This hybrid is comprised of 4-port microstrip disc. It appears that the authors were able to increase the operational bandwidth of the circular disc 4-dB quadrature coupler to about 20%. Open and short-circuited stubs were introduced to the periphery of the coupler in order to realize a broader bandwidth. This technique was applied previously by Riblet [1980] and Ohta [1989] on planar components and broader operational bandwidth was realized. In addition to listing a few corrections, the author responds to some inaccurate statements made in the original article by offering some comments. The original authors reply to these comments.<>