Ensuring the performance of modified microstrip loops in the frequency band

Abstract

Problem statement. Microstrip loop structures of various configurations are widely used to form topologies of multi-pole microwave devices. In this regard, there is a need to study the frequency properties and topological features of the construction of loop structures that determine the amplitude and phase frequency characteristics, as well as the overall parameters of a microstrip radio engineering device. Objective. Studying of frequency characteristics of T- and U-shaped loop configurations implemented on the basis of high-resistance and low-resistance segments of microstrip transmission lines that allow configuring small-sized topologies of multi-pole devices with acceptable electrical characteristics. Results. A number of basic topologies of loop structures designed to function in given frequency bands have been studied. With the help of electrodynamic modeling and parametric optimization, according to a number of criteria (given wave resistance, phase shift, reflection coefficient), the necessary geometric dimensions of the modified topologies were determined. The dependence of the frequency band on the geometric dimensions of the low-resistance loop of the T-section is revealed. By the level of “minus” 20 dB from the maximum of the reflection coefficient, the values of the frequency band width of two types of T-structures – symmetrical and counter-pin - were determined and compared. It is shown that the U-shaped section is characterized by an increased frequency band due to better matching, however, its geometric dimensions exceed the dimensions of the basic T-structures. Practical significance. Modified microstrip loop structures in some cases are able to effectively replace quarter-wave segments of transmission lines, on the basis of which most microwave devices are formed (directional couplers, power dividers, electric filters, phase shifters, crossovers, etc.). The use of combinations of T- and U-shaped structures leads to a significant reduction in the area of microstrip devices designed to operate in the UHF and Microwave bands.