RU2619363C1 - Band-pass microwave filter - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: band-pass microwave filter contains quarter-wave resonators installed on a metal base and galvanically interconnected by side surfaces. The resonators are made on the basis of coaxial ceramic lines of square section. Each resonator and its capacitors of coupling with another resonator or external device are made as one structural element. The coupling capacitors are separated from the resonator by a gap in the metal coating on the outer surface of the coaxial ceramic line and are made in the form of ceramic capacitors. The inner conductor and the lateral surfaces of a coaxial ceramic line length running from the gap to the open end of the coaxial ceramic line serve as the capacitors plating. There is no metal coating on the horizontal surfaces of this length of the coaxial ceramic line. Adjustment of the frequency in the filter is performed due to the availability of sampling points in the metal coating. The width of the gap separating the resonator from the coupling capacitors, is determined by the value of the surface breakdown voltage.

EFFECT: reduction of overall dimensions, improvement of frequency, power, strength characteristics.

2 cl, 6 dwg

Description

The invention relates to the field of microwave technology and can be used in receiving and transmitting devices for filtering pulsed microwave signals with a high level of transmitted power.

Known band-pass microwave filter (PPF) on disk dielectric resonators made of ceramic material with high thermal stability and quality factor [1], selected as an analogue.

Structurally, the PPF (Fig. 1) is a disk dielectric resonator (pos. 3 in Fig. 1) installed in a shielded case (pos. 1 in Fig. 1) on dielectric supports (pos. 2 in Fig. 1), the connection between which provided by the electromagnetic field, and with external devices - pin exciters (item 4 in Fig. 1). The presence of such communication elements provides the required distances for electrical strength and allows transmission of microwave signals with a pulse power of at least 100 watts.

The device [1] has the following disadvantages:

- low resistance to mechanical stress;

- the presence of spurious passband near the fundamental frequency;

- low weight and size characteristics.

The above drawbacks are due to the use of disk dielectric resonators as oscillating systems operating on the lower type of vibrations H _01δ , the diameter of which is comparable to 1/2 the wavelength in the dielectric, the method of fastening the disk dielectric resonators and the need to place all elements of the device in a shielded volume with specified the distances of the conductive walls of the housing to disk dielectric resonators and pin exciters.

Known PPF on quarter-wave coaxial ceramic resonators manufactured by LORCH MICROWAVE [2].

Structurally, the PPF (Fig. 2) is a quarter-wave coaxial ceramic resonators (CCR) placed on a metal base (pos. 5 in Fig. 2) (pos. 6 in Fig. 2) and a matching board mounted on them (pos. 7 in Fig. 2) .2), on which coupling capacitors are formed between adjacent coaxial ceramic resonators and coupling capacitors of extreme coaxial ceramic resonators with external devices. The design of PPF [2] allows the use in one product of coaxial ceramic resonators of various lengths made of ceramic materials with various electrophysical parameters, which expands the possibilities for improving the electrical characteristics of PPF.

PPF [2] has the following disadvantages:

- low resistance to mechanical stress;

- low level of transmitted power (not more than 1 W according to the reference data).

The first drawback is due to the mounting of the matching microplate only on the support posts (pos. 8 in Fig. 2), inserted into the holes of the coaxial ceramic resonators and galvanically connected to their internal conductors, without fixing this matching board to the base. In the presence of mechanical vibrations, this board starts to oscillate, which can, as shown by the practice of their application, lead to a break in the strip terminals of communication with external devices.

The second drawback is due to the low breakdown voltage of the coupling capacitors on the matching board, made in the form of gaps between the contact pads to which the internal conductors of the coaxial ceramic resonators are soldered.

Known PPF on ceramic monolithic blocks [3] manufactured by Transtronika OJSC (St. Petersburg).

Structurally, the PPF (Fig. 3) is a ceramic monolithic block (pos. 9 in Fig. 3) placed on a metal base (pos. 10 in Fig. 3), which is equivalent to the closely mounted quarter-wave Raman without adjacent conducting walls, while the coupling capacitors ( Pos. 11 in Fig. 3) are made directly on the open end of the ceramic monolithic block in the form of gaps between conductive pads connected to its internal conductors.

PPF [3] is characterized by high resistance to mechanical stress, small dimensions and weight, small number of parts.

PPF [3] has the following disadvantages:

- low level of transmitted power (not more than 1 W according to TU [3]);

- high requirements for the technological development of technological processes for the manufacture of ceramic monolithic blocks in mass production;

- the exclusion of the possibility of using in one device ceramic materials with different dielectric constants, which limits the possibility of improving its electrical characteristics.

The first drawback is due to the low breakdown voltage of the communication capacitors, made in the form of gaps between conductive pads connected to the internal conductors of the ceramic monolithic block.

The second drawback is due to the need to obtain high uniformity in volume of electrophysical parameters of the ceramic material from which the ceramic monolithic block is made.

The third disadvantage is due to the monoblock design of the ceramic monolithic block.

Known PPF [4] on the quarter-wave coaxial ceramic resonators of square cross section developed by the Federal State Unitary Enterprise Scientific Research Center for Scientific Research Yu.E. Sedakova ”(Nizhny Novgorod), selected for the prototype.

Structurally, the PPF (Fig. 4) is a quarter-wave coaxial ceramic resonators of square section (pos. 13 in Fig. 4) placed on a metal base (pos. 12) and a matching board (pos. 14 in Fig. 4), on which the coupling capacitors between adjacent coaxial ceramic resonators and the coupling of the outermost ones with external devices are made in the form of gaps between the contact pads to which the internal conductors of the coaxial ceramic resonators are soldered.

The parameters of the capacitive elements C1, C2 and C3 of the PPF prototype, the circuit of which is shown in FIG. 5 can be obtained by solving a system of equations of the form

Where

K is the complex transmission coefficient, which is determined for a two-cavity PPF in accordance with the procedure [5];

ω _0р is the resonant frequency of the Raman scattering coefficient;

ω ₀ is the resonant frequency of the PPF;

ω ₁ and ω ₂ are the boundary frequencies of the PPF passband.

и полосе пропускания

(по уровню минус 3 дБ) емкости связи С1,С2 и С3 будут иметь следующие значения:From all possible solutions are selected that provide the maximum value of the transmission coefficient at the center frequency. Considering, for example, PPF based on resonators made of ceramic material with a relative permittivity ε = 100, at the center frequency of the amplitude-frequency characteristic (AFC) of the PPF

and bandwidth

(in terms of minus 3 dB) the communication capacities C1, C2 and C3 will have the following values:

C1 = C3 = 0.9 pF; C2 = 0.23 pF.

When these communication capacities are implemented in the form of gaps in the contact areas of the matching board made of ceramic material with a relative permittivity ε _p = 10 and a substrate thickness h = 1 mm, as was done in the PPF prototype of FIG. 4, their width can be determined using a graph of the relationship between the linear capacitance and the dielectric constant of the substrate versus the ratio of the gap width to the thickness of the substrate for a given ratio of the width of the contact pad to the thickness of the substrate [6]. For the given values of the communication capacities, the length and width of the contact pads l = 3 mm and w = 2 mm, the gap width S is:

for C1 and C3-S1 = 0.075 mm, for C2-S2 = 0.7 mm.

According to [2, 3], the maximum level of transmitted power is 1 W for the PPF design with coupling capacitors made in the form of gaps between conductive pads on a ceramic base with a dielectric constant of ~ 100 and a minimum gap width of ~ 0.3 mm. Thus, the level of transmitted power of the PPF prototype, for which the communication capacitance is realized in the form of gaps in the contact areas of the matching board with a lower dielectric constant (ε _p = 10) and a minimum gap width of ~ 0.075 mm, will not exceed 1 W.

PPF [4] is distinguished by the possibility of using coaxial ceramic resonators made of various ceramic materials in one PPF to improve electrical characteristics, ease of adjustment, resistance to mechanical stress, as well as small dimensions and weight.

PPF [4] has the following disadvantages:

- the presence of a large level of radiation loss;

- a large number of components;

- low manufacturability and assembly;

- low level of transmitted power (not more than 1 W).

The first drawback is caused by microwave radiation from the open end of the resonators and ribbon jumpers (pos. 15 in Fig. 4) connecting the internal conductors of the resonators with the contact pads on the matching board.

The second drawback is due to the design, in which, in addition to the resonators, the base, matching board and ribbon jumpers are used.

The third drawback is due to the need to use photolithography in the manufacture of matching boards and soldering ribbon jumpers to the internal conductors of the resonators.

The fourth drawback is due to the low breakdown voltage of the coupling capacitors on the matching board, made in the form of gaps between the contact pads to which the internal conductors of the resonators and external devices are soldered.

The technical result of the proposed invention is the creation of small PPF with the best frequency, power, strength and mass-dimensional characteristics with high manufacturability.

The technical result is achieved by the fact that in a band-pass microwave filter containing quarter-wave resonators mounted on a metal base and galvanically interconnected by side surfaces, made on the basis of square coaxial ceramic lines, each resonator and its coupling capacitance with another resonator or external device made as one structural element, while the communication capacitance is separated from the resonator by a gap in the metallization of the outer surface of the coaxial core nical lines and made in the form of ceramic capacitors, the electrodes which are an inner conductor and the side surface of the coaxial line from the ceramic gap to the open end of the ceramic coaxial line, and on the horizontal surfaces of the coaxial line is absent ceramic metallization.

The width of the gap separating the resonator from the communication capacities is determined from the magnitude of the surface breakdown voltage corresponding to a given value of the maximum pulse power level of the input signal.

The formation of coupling capacitors in the form of ceramic capacitors, the lining of which are the side surfaces and the inner conductor of the coaxial ceramic line, provides them with high breakdown voltages.

The implementation of the resonator and communication capacities in the form of a single part provides high strength and mass-dimensional characteristics of PPF with a minimum number of assembly units and high adaptability in the manufacture, assembly and adjustment.

The proposed PPF explain figures 1-6.

In FIG. Figure 1 shows the design of the PFD based on disk dielectric resonators, given in [1]. In FIG. 1 shows: 1 - PPF case; 2 - dielectric stand; 3 - disk dielectric resonator; 4 - pin pathogen.

In FIG. 2 shows the design of PPF manufactured by LORCH MICROWAVE [2]. In FIG. 2 shows: 5 - metal base; 6 - a quarter-wave coaxial ceramic resonator of square section; 7 - matching board with communication capacities; 8 - metal support.

In FIG. Figure 3 shows the design of the PPF manufactured by Transtronika OJSC [3]. In FIG. 3 shows: 9 - metal base; 10 - ceramic block; 11 - capacitive coupling gaps.

In FIG. Figure 4 shows the design of the PPF developed by the Federal State Unitary Enterprise Scientific Research Center named after Yu.E. Sedakova ”[4]. In FIG. 4 are shown: 12 — metal base; 13 - a quarter-wave coaxial ceramic resonator of square section; 14 - matching board with communication capacities; 15 - ribbon jumper.

In FIG. 5 shows an equivalent circuit of PPF, the designs of which are shown in FIG. 2-4 and the proposed PPF of FIG. 6. In FIG. 5 shows: Z1, Z2 - resonators; C1, C3 - coupling capacitors with external devices; C2 - capacitor coupling resonators with each other.

In FIG. 6 shows the proposed design of the PPF. In FIG. 6 shows: 16 - metal base; 17 - coaxial ceramic resonator square section; 18 - coupling capacitor between adjacent resonators; 19 - coupling capacitor with external devices; 20 - places of soldering; 21 - places of sampling of metallization when adjusting the frequency; 22 - sampling metallization when adjusting the connection between the resonators; 23 - metallization sampling points when adjusting communication with external devices; 24 - a gap in the metallization of the outer conductor.

In the proposed PPF (Fig. 6), the coupling capacitance between the resonators (pos. 18 in Fig. 6) and the coupling of the extreme resonators with external devices (pos. 19 in Fig. 6) are implemented by capacitors, the lining of which is the inner conductor of the coaxial ceramic line and its side surfaces, and insulator ceramic material of the coaxial line. The minimum thickness of the insulator b is

Where

a - the width of the coaxial line of square section (external conductor);

d is the diameter of the hole of the coaxial line of square section (inner conductor).

In accordance with (2), for a = 6 mm, d = 2.5 mm, the minimum thickness of the insulator b is

b = 1.75 mm.

According to [7], the dielectric strength of the ceramic material is at least E≥10 kV / mm, i.e. for the proposed PPF, the breakdown voltage of the capacitance of communication with external devices C1, C3 will be at least 17.5 kV, for the capacitance of communication between resonators C2 - at least 35 kV (capacitance C2 is formed by two capacitors connected in series). Thus, the capacitive elements of the proposed PPF provide the passage of microwave power of at least 100 watts.

The width of the gap in the metallization of the outer surface of the coaxial ceramic line dividing this line into the resonator and capacitive coupling elements (pos. 24 in Fig. 6) is chosen from the condition that there is no surface breakdown at the center frequency of the frequency-frequency characteristic of the PPF and has little effect on the characteristics of the resonators and coupling capacities.

The lengths of the segments of coaxial ceramic lines from the gap to the open end of the resonator with metallization absent on horizontal surfaces forming the coupling capacities can be determined:

- for capacitances of coupling extreme resonators with external devices C1 and C3 formed by an internal conductor and an external vertical metallized surface of a segment of a coaxial ceramic line [8]

- for the coupling capacitance between adjacent C2 resonators formed by two capacitances connected in series between the inner conductors and the inner vertical metallized surfaces [8]

Production, assembly and adjustment of PPF are carried out in the following sequence.

1. In the initial workpiece in the form of a short-circuited segment of a coaxial ceramic line of square section (pos. 17 in Fig. 6) at a distance corresponding to ¼ of the wavelength in the ceramic material, it is removed from the external surface by a mechanical method, for example, by cutting a boron machine, metallization with formation perpendicular to the axis of the inner hole of the gap (key 24 in FIG. 6). The gap width is determined by the maximum pulse power level of the input microwave signal.

2. Using relations (3) and (4), the length of the segment of the coaxial ceramic line from the gap to the open end, on which the communication capacities are formed (pos. 18 and pos. 19 in Fig. 6), is determined, and then the workpiece is shortened to those calculated by length values by trimming or grinding.

3. From two opposite sides of the segment of the coaxial ceramic line on which the communication capacities are formed (pos. 18 and pos. 19 in Fig. 6), metallization is removed mechanically, the remaining metallized surfaces and the inner conductor will be the lining of the coupling capacitors.

4. A metal base with a minimum coefficient of linear expansion is used to make a PPF base (pos. 16 in Fig. 6), the dimensions of which ensure its absence under a segment of a coaxial ceramic line on which communication capacities are performed.

5. The installation of the resonators on the base is carried out by soldering, also the side surfaces of adjacent resonators and coupling capacitors between the resonators are connected by soldering (pos. 20 in Fig. 6).

6. The resonator frequency is adjusted by partially removing mechanically metallizing (for example, a mill drill) from its upper horizontal surface from the gap side (pos. 21 in Fig. 6).

7. Adjustment of the connection between the resonators is carried out by reducing the galvanic contact area of the welded side surfaces using a boron machine cutter (pos. 22 in Fig. 6).

8. The coupling of the resonator with an external device is adjusted by partially removing the metallization from its side surface (pos. 23 in Fig. 6).

Compared with the prototype, the proposed PPF has the following advantages:

- simplicity of design due to the small number of components;

- high mechanical strength due to the absence of attachments in the structure;

- high transmitted microwave power due to the use of ceramic capacitors as coupling capacitors instead of capacitive gaps;

- high manufacturability, assembly and adjustment, due to the simplicity of the design, the lack of matching boards and ribbon jumpers, ease of access to the adjustment points;

- low loss in the passband due to the absence of radiation from the open end of the resonator and ribbon jumpers.

Literature

1. Dielectric resonators / Ed. M.E. Ilchenko. - M .: Radio and communications, 1989 .-- 224 p.

2. Ceramic filters type 4DF4-975 / 10-M manufactured by LORCH MICROWAVE, http://www.lorch.com.

3. Ceramic filters type FS (3) -975/20 manufactured by Transtronika OJSC. UZHMK.434834.003TU.

4. Antennas and functional units of the microwave and EHF ranges. Calculation Methods and Manufacturing Technology / Ed. A.Yu. Sedakova. - M .: Radio engineering, 2011 .-- 101 p.

5. Sedakov A.Yu., Svetlakov Yu.A., Ivoylova M.M. Mathematical modeling in the design and technology of microwave filters on coaxial ceramic resonators // Antennas, 2016. issue. 1 (221). - S. 8-17.

6. Leonchenko V.P., Feldstein A.L., Shepelyansky L.A. Calculation of strip filters on oncoming rods. Directory. - M .: Communication, 1975 .-- 44 p.

7. Handbook of electrical materials. Volume 2. / Ed. Yu.V. Koritsky, V.V. Pasynkova, B.M. Tareeva. - M.: Energoatomizdat, 1987 .-- 242 p.

8. Meinke X., Gunlach F.V. Radio technical reference. Volume 1. - M .: Gosenergoizdat, 1961 .-- 49 p., 136 p.

Claims (2)

1. A band-pass microwave filter containing quarter-wave resonators mounted on a metal base and galvanically connected to each other by side surfaces, made on the basis of coaxial ceramic lines of square cross section, characterized in that each resonator and its coupling capacitance with another resonator or external device are made as one structural element, while the communication capacitance is separated from the resonator by a gap in the metallization of the outer surface of the coaxial ceramic line and They are in the form of ceramic capacitors, the lining of which is the inner conductor and the side surfaces of the segment of the coaxial ceramic line from the gap to the open end of the coaxial ceramic line, and there is no metallization on the horizontal surfaces of this segment of the coaxial ceramic line. 2. The band-pass microwave filter according to claim 1, characterized in that the width of the gap separating the resonator from the communication capacities is determined from the magnitude of the surface breakdown voltage corresponding to a given value of the maximum level of pulse power of the input signal.

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