Study of the influence of dielectric permittivity on effectiveness of branch-line coupler miniaturization

Due to dynamic development and growing complexity of radio-technical devices, such field as miniaturization appeared. Miniaturization is reduction of device dimensions. This paper presents analysis of the influence dielectric permittivity has on effectiveness of branch-line coupler miniaturization. The miniaturization method in this paper consists in use of artificial transmission lines, having smaller longitudinal dimensions than a quarter-wave microstrip transmission line segment. By means of three-dimensional electrodynamic simulation the standard and compact branch-line couplers with dielectric permittivity of 3, 4.4, 6, 7.2 and operating frequency of 2000 MHz were simulated and their frequency characteristics were obtained. The suggested miniaturization method allowed to reduce the dimensions of branch-line couplers by 67.8, 71.15, 70.4, 67% correspondingly as compared to those of standard structures.