Increasing Quality Factor of Two-Stub Resonator

Introduction. Narrowband filters and oscillators based on resonators are used in radiolocation, wireless and mobile communications, testing and measuring equipment. Coupled resonators form a bandpass characteristic. Resonance structures based on transmission line stubs are widely used, in particular, a two-stub resonator with open-circuited stubs. The advantages of such a resonator are a high steepness of the transmission response and the presence of zeros near the passband. The purpose of this paper is to increase two-stub resonator quality factor by replacing conventional open-circuited one-section stubs with two-section ones.1 Conditions for comparing the characteristics of stubs. The frequency dependence of the resonator's reactive conductivity determines both the quality factor and the level in the resonator's suppression bands. It is shown that at a given level in the suppression bands, one-section and two-section stubs should have the same low-frequency capacities.2 Comparison of reactive characteristics of open-circuited two-section and one-section stubs. The frequency dependences of reactive conductivity of open-circuited two-section and one-section stubs are given. The steepness of the reactive conductivity of the two-section stub is higher, which makes it possible to increase the quality factor of the two-stub resonator. Rise in steepness increases with the decrease in the length of the two-section stub and reaches 23%. The two-section stub is shorter than the one-section stub.3 Resonator based on open-circuited two-section stubs. The transmission response of a two-stub resonator with open-circuited two-section stubs is presented. The resonator has a 15% higher quality factor and half the length compared to a resonator with one-section stubs.4 Resonator based on open- and short-circuited stubs. The transmission response of a two-stub resonator with open-circuited two-section and short-circuited one-section stubs is given. In such a resonator, there are no parasitic responses at zero and doubled frequencies. The disadvantages are the short length of the short-circuited stub (which complicates its constructive implementation), the worse steepness of frequency response on the side of lower frequencies and only one zero.5 Results discussion. A two-stub resonator with one-section stubs is half-wave. The length of the two-stub resonator with two-section stubs is much shorter. The quality factor of this resonator increases with decreasing length, since the steepness of its reactive conductivity increases with decreasing stub length. The limitations are the minimum acceptable length of the stub section and the maximum acceptable difference in the characteristic impedances of the sections, which increases as the length decreases.Conclusion. The frequency dependence of the reactive conductance of an open two-section stub has a steeper slope compared to an open one-section stub. Increase in steepness reaches 23%.Given the frequency response parameters, the considered resonator with open-circuited two-section stubs has a 15% higher quality factor and half the length. Making one of the resonator stubs short-circuited allows you to expand the suppression bands.The development of the research is the consideration of the formation of the bandpass characteristic by the proposed resonators.