RU2829705C2 - Microwave filter - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to radio engineering, namely to microwave engineering, and can be used as a waveguide transformer of ultrahigh frequencies. Waveguide microwave impedance transformer comprises supply rectangular waveguides of different cross-sections, between which there are diaphragms and sections of waveguides. At that, transformer consists of alternation of diaphragms and one-sided or double-sided loops, wherein the diaphragm is located at the supply rectangular waveguide, having a higher wave impedance, and the train is located at the supply waveguide with a lower wave impedance.

EFFECT: improved frequency selectivity of the transformer.

1 cl, 12 dwg

Description

The invention relates to radio engineering, in particular to microwave engineering, and can be used as a waveguide transformer.

State of the art

A microwave waveguide transformer is known, described in: L. Young. "Optimum Quarter-Wave Transformers." IRE Transactions on Microwave Theory and Techniques, vol. 8, issue 5, pp. 478-482, September 1960). doi: 10.1109/TMTT.1960.1124774. The waveguide transformer described in this article contains input and output waveguides of different cross-sections and waveguide quarter-wave sections. The transverse dimensions of the input and output waveguides, the bandwidth, and the value of the standing wave ratio (SWR) determine the cross-sections of each quarter-wave section and their number.

The disadvantage of this device is the low selectivity of its amplitude-frequency response (AFR).

The closest in technical essence to the claimed object is a microwave waveguide impedance transformer, described in: B.V. Prokofiev, M.A. Martynenko. "Short waveguide impedance transformers." Radioelectronics, No. 11, 2013, pp. 1-12.

This waveguide transformer contains input and output waveguides of different cross-sections and a combination of waveguide sections of different cross-sections and diaphragms, which significantly reduces the dimensions. The transition length is reduced by increasing the width of the waveguide sections, which leads to an expansion of the passband. At the same time, there is a width of the waveguide section at which the passband is maximum. The increase in the passband is explained by a decrease in the dispersion of the wave in the waveguide section, and the existence of an optimal width of the waveguide section is explained by the fact that a further increase in the width leads to an increase in reflections at the joints of the waveguide sections. An even greater reduction in length is achieved by replacing one or more of the waveguide sections with resonant diaphragms. With this approach, the transition length can be reduced by 3-4 times compared to a classic quarter-wave impedance transformer.

The disadvantage of this device is the low selectivity of its frequency response.

Thus, there is a technical problem of implementing microwave waveguide transformers with high frequency response selectivity.

Disclosure of invention.

The objective of the proposed invention is to increase the frequency selectivity of the device.

The technical result of the invention is an increase in the selectivity of the frequency response of the transformer due to the formation of attenuation poles near the operating frequency band, leading to the formation of a stop band to the left and right of the pass band.

The specified technical result is achieved by the fact that the transformer design implements alternation of diaphragms and one-sided or two-sided loops (high-resistance waveguide sections).

In the claimed microwave waveguide transformer, a structure consisting of diaphragms and high-resistance waveguide sections (stubs) is used between the input and output metal sections of waveguides of different cross-sections. The supply waveguide (input), the wave resistance of which is lower than the other supply waveguide (output), is immediately joined with the high-resistance waveguide section without an intermediate diaphragm. Then a structure is formed with alternating high-resistance waveguide sections (stubs) and diaphragms. The formation of the stop band is carried out using high-resistance waveguide sections operating as waveguide stubs, forming attenuation poles. The position of the attenuation poles depends on the transverse dimensions of the high-resistance sections. The diaphragms act as resonators that form the passband, so the number of diaphragms determines the order of the waveguide impedance transformer, and high-resistance waveguide sections (stubs) provide inter-resonator connections. This approach reduces the length by 3-4 times compared to the classic quarter-wave impedance transformer.

A waveguide transformer having attenuation poles above the passband consists of alternating capacitive diaphragms and high-resistance waveguide sections (stubs). This waveguide impedance transformer has E-plane symmetry, i.e. the capacitive diaphragms are symmetrical and the high-resistance waveguide sections are also symmetrical. Thus, the high-resistance waveguide sections form two short-circuited identical stubs. A waveguide transformer having attenuation poles above the passband can also be without E-plane symmetry, containing alternation of asymmetric high-resistance waveguide sections and asymmetric capacitive diaphragms. The width of the waveguide transformer is selected so that the cutoff frequency is less than the lower passband frequency, but higher than the cutoff frequencies of the input and output waveguides. Thus, the narrowed width of the transformer forms a stopband without attenuation poles below the passband.

A waveguide transformer having attenuation poles below the passband consists of alternating resonant diaphragms and high-impedance waveguide sections (stubs). This waveguide impedance transformer has E-plane symmetry, i.e. the resonant diaphragms are symmetrical and the high-impedance waveguide sections are also symmetrical. Thus, the high-impedance waveguide sections also form two short-circuited identical stubs. A waveguide transformer having attenuation poles below the passband can also be without E-plane symmetry, containing alternating asymmetric high-impedance waveguide sections and asymmetric resonant diaphragms. The width of the waveguide transformer is selected so that the cutoff frequency is less than the cutoff frequency of at least one of the supply waveguides, or less than the cutoff frequencies of both supply waveguides. To form a stop band above the pass band, the frequency of the attenuation pole of one of the high-impedance sections is selected above the pass band.

The essence of the invention is explained by the drawings:

- Fig. 1. Transformer with E-plane symmetry from the side of the narrow wall of the waveguide with attenuation poles above the passband;

- Fig. 2. Transformer with E-plane symmetry from the side of the wide wall of the waveguide with attenuation poles above the passband;

- Fig. 3. Frequency characteristics of a transformer with E-plane symmetry with attenuation poles above the passband;

- Fig. 4. Transformer without E-plane symmetry from the side of the narrow wall of the waveguide with attenuation poles above the passband;

- Fig. 5. Transformer without E-plane symmetry from the side of the wide wall of the waveguide with attenuation poles above the passband;

- Fig. 6. Frequency characteristics of a transformer without E-plane symmetry with attenuation poles above the passband;

- Fig. 7. Transformer with E-plane symmetry from the side of the narrow wall of the waveguide with attenuation poles below the passband;

- Fig. 8. Transformer with E-plane symmetry from the side of the wide wall of the waveguide with attenuation poles below the passband;

- Fig. 9. Frequency characteristics of a transformer with E-plane symmetry with attenuation poles below the passband;

- Fig. 10. Transformer without E-plane symmetry from the side of the narrow wall of the waveguide with attenuation poles below the passband;

- Fig. 11. Transformer without E-plane symmetry from the side of the wide wall of the waveguide with attenuation poles below the passband;

- Fig. 12. Frequency characteristics of a transformer without E-plane symmetry with attenuation poles below the passband.

The microwave waveguide transformers (Fig. 1...Fig. 12) according to the invention comprise an input waveguide with a lower wave impedance 1 and an output waveguide with a higher wave impedance 2. The transformer, having attenuation poles at the top and possessing E-plane symmetry, between the input and output waveguides comprises alternation of symmetrical capacitive diaphragms 4 and high-resistance waveguide sections (stubs) 3, wherein the low-resistance input waveguide 1 is connected to the high-resistance section of the waveguide 3, and the high-resistance output waveguide 2 is connected to the symmetrical capacitive diaphragm 4, the entire structure of the transformer is performed on a narrowed section 5 (Fig. 1, Fig. 2).

A transformer having attenuation poles at the top and not having E-plane symmetry contains alternation of asymmetric capacitive diaphragms 8 and high-resistance waveguide sections 9 between the input and output waveguides, which are also one-sided loops. Moreover, the low-resistance input waveguide 1 is connected to the high-resistance section of the waveguide 9, and the high-resistance output waveguide 2 is connected to the asymmetric capacitive diaphragm 8, the entire structure of the transformer is performed on a narrowed section 5 (Fig. 4, Fig. 5).

The transformer, having attenuation poles at the bottom and possessing E-plane symmetry, contains alternation of symmetrical resonant diaphragms 6 and high-resistance waveguide sections 3 between the input and output waveguides, which are also two-sided loops. Moreover, the low-resistance input waveguide 1 is connected to the high-resistance section of the waveguide 3, and the high-resistance output waveguide 2 is connected to the symmetrical resonant diaphragm 6, the entire structure of the transformer is performed on the expanded section 7 (Fig. 7, Fig. 8).

A transformer having attenuation poles at the bottom and not possessing E-plane symmetry contains alternation of asymmetrical resonant diaphragms 10 and high-resistance waveguide sections 9 between the input and output waveguides, which are also one-sided loops. Moreover, the low-resistance input waveguide 1 is connected to the high-resistance section of the waveguide 9, and the high-resistance output waveguide 2 is connected to the asymmetrical resonant diaphragm 10, the entire structure of the transformer is performed on the expanded section 7 (Fig. 10, Fig. 11).

Claims (1)

A microwave impedance waveguide transformer containing supply rectangular waveguides of various cross-sections, between which diaphragms and sections of waveguides are located, characterized in that the transformer consists of alternating diaphragms and one-sided or two-sided loops, wherein the diaphragm is located at the supply rectangular waveguide having a greater wave impedance, and the loop is located at the supply waveguide with a lower wave impedance.