RU2401490C1 - Microstrip broad-bandpass filter - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: filter has an insulating substrate, one side of which is completely metal-coated with a screening layer, while on the other side there electromagnetically-connected parallel folded strip conductors with discontinuity of width at the bend and ends which are closed into a screen. The central strip conductor is folded twice, both its ends are closed into a screen and its central part symmetrically lies between outermost parts.

EFFECT: possibility of realisation with an odd number of resonators, disclosed filter is small in size and has a large bandwidth, high loss in the stop band and has good accuracy for calculating its characteristics using one dimensional structural models.

1 cl, 4 dwg

Description

The invention relates to techniques for microwave frequencies and is intended for frequency selection of signals.

Known microstrip bandpass filter on stud resonators with a jump in wave impedance (figure 1) [B.A. Belyaev, S.V. Butakov, N.V. Laletin, A.A. Lexikov, V.V. Tyurnev, O .N. Chesnokov. Selective properties of microstrip filters on irregular resonators // Radio engineering and electronics. 2004, T. 49, No. 11, S.1397-1406]. The filter contains a dielectric substrate, one side of which is completely metallized with a shielding layer, and on the other side are strip conductors forming electromagnetically coupled microstrip resonators. Strip conductors are once rolled in the form of a hairpin and contain a jump in width at one of the bends. The end of a narrow section of the strip conductor is closed to the screen. In this filter, in the formation of the passband, one oscillation mode is used from each resonator (Fig. 1). Therefore, the order of the filter is equal to the number of resonators. The disadvantage of the filter is the impossibility of its implementation with an odd number of resonators due to the fact that its central resonator, like the rest of the resonators, does not have geometric symmetry. The presence of such symmetry is necessary to ensure the required symmetry of the electrical characteristics with respect to the filter ports.

The closest analogue is a microstrip broadband pass-pass filter on stud resonators with a jump in wave impedance (Fig.2) [Patent RU No. 2182738, MKI ⁷ Н01Р 1/203, 1/205, bull. No. 14 dated 05/20/2002 (prototype)]. The filter contains a dielectric substrate, one side of which is completely metallized with a shielding layer, and on the other side are strip conductors forming electromagnetically coupled microstrip resonators. Strip conductors are once folded in the form of a hairpin and contain a jump in width at one of the bends. The end of a wide section of the strip conductor is closed to the screen (figure 2). Such strip conductors operate in the filter as dual-mode resonators, which increases the selective properties of the filter. Therefore, the order of the filter is equal to twice the number of resonators.

The disadvantage of the filter is the impossibility of its implementation with an odd number of resonators due to the fact that its central resonator, like the rest of the resonators, does not have geometric symmetry. The presence of such symmetry is necessary to ensure the required symmetry of the electrical characteristics with respect to the filter ports.

The technical result of the invention is the possibility of implementing a filter on two-mode resonators with an odd number of resonators.

The indicated technical result is achieved in that in a microstrip broadband bandpass filter containing a dielectric substrate, one side of which is completely metallized by a shielding layer, and on the other side are electromagnetically connected rolled strip conductors with jumps in width at the bend and ends closed to the screen, new is that the central strip conductor is double-folded, both ends are closed to the screen, and its central portion is symmetrically located between the extreme sections.

The difference of the claimed device from the closest analogue is that the strip conductor of the central resonator is double-folded, both ends are closed to the screen, and its central section is symmetrically located between the extreme sections. Due to this, the microstrip filter on two-mode resonators becomes symmetrical and therefore can be realized with an odd number of resonators.

Thus, the above characteristics that are distinctive from the prototype allow us to conclude that the claimed technical solution meets the criterion of "novelty."

Signs that distinguish the claimed technical solution from the prototype are not identified in other technical solutions and, therefore, provide the claimed solution with the criterion of "inventive step".

The invention is illustrated using graphic materials:

Figure 1 shows a well-known microstrip bandpass filter on rolled single-mode resonators with a jump in wave impedance.

Figure 2 shows the closest analogue of the invention.

Figure 3 shows an example implementation of the inventive filter, where 1 is a dielectric substrate, 2 is strip conductors, 3 is a port.

Figure 4 shows the frequency response for a specific implementation example of a filter.

The band-pass filter (Fig. 3) contains a dielectric substrate (1), one side of which is completely metallized with a shielding layer, and on the other side are rolled strip conductors with jumps in width at the bend and with wide ends closed to the screen, forming electromagnetically coupled microstrip resonators (2). The central strip conductor is double-rolled so that its narrow section is symmetrically located between the wide sections. The two extreme strip conductors are conductively connected to the input and output ports (3).

The filter works as follows. The signal is applied to one of the filter ports. Due to the increase in the amplitude of electromagnetic excitations in microstrip resonators at the frequencies of coupled oscillations, it is transmitted with small losses in the passband to the second port. At other frequencies, the signal undergoes a strong reflection from the input port. The jumps in the width and folding of the strip conductors bring together the resonance frequencies of the first two vibration modes, turning the microstrip resonators into two-mode ones. This doubles the order of the filter, increasing its selective properties.

Figure 3 shows an example of a filter. The filter contains three folded two-mode microstrip resonators with a jump in wave impedance, electromagnetically coupled to each other. The strip conductors of the two extreme resonators are identical. They are folded once and have one jump in width. Their wide ends are closed to the screen. The conductors of the input and output ports of the filter are conductively connected to narrow sections of the conductors of the extreme resonators.

The strip conductor of the central microstrip resonator is twisted twice, and has two jumps in width. Its central section is symmetrically located between the two extreme sections. Both ends of the resonator are closed to the screen.

Figure 4 shows the amplitude-frequency characteristic for a microstrip filter with a central frequency bandwidth of 0.5 GHz, a relative width of 91% at a relative level of -3 dB and a maximum level of reflection in the passband of -14 dB, made on a substrate with dimensions of 23.75 × 5.95 × 1 mm ³ with a dielectric constant of 80. The proportions of the dimensions of the conductors are shown in figure 3.

The advantages of this filter design are its small size, wide passband, high losses in the obstacle, as well as good accuracy in calculating its characteristics using one-dimensional design models, which allows for high-speed synthesis.

Claims (1)

A microstrip broadband bandpass filter containing a dielectric substrate, one side of which is completely metallized with a shielding layer, and on the other side are electromagnetically connected rolled strip conductors with jumps in width at the bend and ends closed to the screen, characterized in that the central strip conductor is double-rolled , both ends are closed to the screen, and its central section is symmetrically located between the extreme sections.

Images