Abstract
The problem of the realization of broadband quadrature directional couplers in UMS (United Monolithic Semiconductors) PH25 is thoroughly investigated. The limitations of the selected technology are discussed with respect to directional couplers’ design. It is shown that, in such technologies, two major problems have to be overcome to achieve the high-performance of the resulting integrated couplers, i.e., the realization of appropriate coupling together with appropriate characteristic impedances, and the equalization of inductive and capacitive coupling coefficients that are inherently different in inhomogeneous dielectric structures. Three different solutions that allow for achieving strong coupling in the selected UMS PH25 process were selected and experimentally investigated, showing the possibility of such circuits’ realization. In each of the presented integrated couplers, capacitive compensation techniques were applied for coupling coefficients’ equalization.
Highlights
Quadrature directional couplers are well-known components that are often used in complex microwave circuits and networks [1,2,3,4]
We present thorough investigations on the coupled-line directional couplers that are designed and fabricated in the chosen UMS PH25 technology
Another coupled-line configuration that can be considered in the UMSPH25 stack-up is a two-strip geometry, in which one of the strips is placed on the M1 layer and the other one is placed on the M2 layer
Summary
Quadrature directional couplers are well-known components that are often used in complex microwave circuits and networks [1,2,3,4]. Though the application of these compensation methods results in a very good performance of the designed coupled-line sections in terms of isolation and return losses, they require freedom in the dielectric stack-up selection and in the geometry of coupled conductors, which, in general, cannot be achieved in processes designated for monolithic integrated circuits. In such processes, it is common that the dielectric stratification cannot be modified and that the constraints on conductor dimensions and their relative placement are very tight. Experimental results of the three fabricated directional couplers are presented for comparison of the achieved properties and commented
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