JPH11195903A - Waveguide filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a filter which has sharp attenuation and a passage characteristic showing a high Q and also is easily and inexpensively installed even in a device that needs high breakdown power by providing air tight windows that hold vacuum air tight at an input end part and an output end part and specifying the degree of internal vacuum. SOLUTION: Slit windows 2 made by one set of two partition plates which face each other are arranged on plural stages in a waveguide 1 and air tight parts 4 are arranged at both ends of it. Ceramics is mainly used for the parts 4. An air release pipe 5 that is provided at the waveguide 1 reduces pressure of the internal degree of vacuum below 1×10<-3> Torr or increases pressure of internal atmospheric pressure up to more than one atmospheric pressure. The pipe 5 is sealed after the pressure is reduced or increased. As the pressure of gas is reduced less than the atmospheric pressure, arcing start voltage falls once and arcing becomes hard to be generated. However, as it is reduced further, the arcing start voltage becomes higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a kind of microwave waveguide circuit element used in a pulse radar device or the like, which passes a necessary frequency component and blocks an unnecessary frequency component. The inside of the waveguide type circuit is decompressed and vacuum-tight or pressurized to improve the power durability against microwave high power.
The present invention relates to a waveguide type filter having a structure capable of maintaining a pressure higher than an atmospheric pressure.

[0002]

2. Description of the Related Art A typical structure of a conventional waveguide type filter is shown in FIGS. 6 to 8, and the prior art is briefly described below. FIG. 6 is an example of a circuit diagram of a waveguide type filter. This circuit is called a 1/4 wavelength coupling type multistage cavity filter, and forms one element with a pair of transmission lines and a pair of susceptances: B, and is usually configured with multiple stages to secure the attenuation. Have been. As can be seen from this figure, since the resonance frequency of each stage is determined by li (i = 1, 2,...), The dimension between the stages is given by λg / 4− (ki + ki + 1). good. Here, ki = 1/2 (1/2 + n) .lambda.g-li / 2, and .lambda.g: guide wavelength n = 0, 1, 2,...

This circuit can be easily realized by a waveguide, and the susceptance B is constituted by installing a pair of slit windows and studs in the waveguide. FIG. 7 is a schematic diagram of a susceptance B constituted by a plurality of pairs of slit windows 2 in a waveguide 1. FIG. FIG. 4 is a schematic view of a device using studs 3 that are paired with the stud.
Then, when a microwave is input to the input terminal in this state, a predetermined necessary frequency component is passed, and a microwave with unnecessary frequency components cut off is output to the output terminal. However, there is no problem when the inputted microwave has a small power, but when a microwave having a large peak power is inputted, the power durability becomes a problem. When a microwave exceeding the withstand power is input, arcing occurs in the waveguide 1 due to a high-frequency electric field. The generated arcing causes a remarkable obstacle to the pulse radar device or the like, and sometimes destroys it.

[0004]

However, in a pulse radar device or the like which operates a microwave having a large peak power, a waveguide type filter is used to suppress frequency components other than the main operating frequency, that is, spurious frequencies. It is necessary to use. Then, as described above, the power durability becomes a problem. If a waveguide type filter that satisfactorily satisfies the power durability is used, a waveguide type filter having a sharp attenuation and a transmission characteristic showing a high Q value is used. Cannot be used. Then, the spurious frequency is suppressed in the pulse radar device or the like, that is, good characteristics of spurious radiation cannot be obtained. Therefore, in such a case, although the power durability is small, it has a passage characteristic showing a sharp attenuation and a high Q value.
That is, a plurality of waveguide type filters having the same characteristics with good spurious radiation are installed in parallel and used. However, with this method, it is difficult to match the characteristics of a plurality of waveguide filters installed in parallel. In addition, there has been a problem that the cost for this is increased. SUMMARY OF THE INVENTION The present invention solves this problem, and can be easily and inexpensively installed even in a pulse radar device or the like which has a sharp attenuation and a high Q value and has a high withstand power, that is, a large microwave. It is an object of the present invention to provide a waveguide type filter that can be used.

[0005]

The present invention has solved the above-mentioned problems by the following first to third means. First, a plurality of slit windows 2 each composed of a pair of two partitioning plates facing each other inside the waveguide 1 or a plurality of studs 3 each formed of a cylindrical rod are installed in the waveguide 1 so that necessary frequency components of microwaves are provided. In a waveguide type filter that passes through and blocks unnecessary frequency components, an airtight window 4 for maintaining vacuum tightness is provided at an input end and an output end of the waveguide type filter. The degree of vacuum inside the waveguide type filter is set to 1.times.10@-3 To.
rr or less.

Secondly, in the above-mentioned waveguide type filter, the pressure inside the waveguide type filter is set to 1 atmosphere or more.

Third, in the above-mentioned waveguide type filter, the pressure inside the waveguide type filter is reduced by sulfur hexafluoride (SF6).
) The pressure is set to 1 atm or more by using gas.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention using the above-described first to third means will be described below with reference to FIGS. FIG. 1 is a schematic diagram of an embodiment of the present invention. First, a plurality of slit windows 2 each composed of a pair of two opposing partition plates are provided in a waveguide 1, and airtight windows 4 are provided at both ends thereof. In this form, airtight windows 4 are provided at both ends of the conventional waveguide type filter shown in FIG. The hermetic window 4 is mainly made of ceramics. In addition, the distance between the slit window 2 and the airtight window 4: L1 is approximately L1 ≒ λg / 4 + nλg / 2λg: guide wavelength n = 0, 1, 2,. Good to do.

The interior of the waveguide 1 is evacuated to a degree of vacuum of 1 × 10 −3 Torr or less, or the internal pressure is increased to 1 atm or more by an exhaust pipe 5 installed in the waveguide 1. Then, the exhaust pipe 5 is sealed after decompression or pressurization. The specifications of this waveguide type filter are as follows.

Center frequency: F = 9400 MHz Pass band width: F ± 140 MHz Required attenuation of stop band: 30 dB (at detuning frequency of F ± 400 MHz) Number of steps: 3 Step size of slit window: d 0 = 9.3 mm Slit Interval between windows 2 (first stage): d1 = 17.8 mm Interval between slit windows 2 (second stage): d2 = 18.9 mm Interval between slit windows 2 (third stage): d3 = 17.8 mm Distance between steps (1st stage): D1 = 6.5 mm Interstage distance (2nd stage): D2 = 6.5 mm In addition, the specified waveguide is WRJ-10.

FIG. 2 is a schematic view of another embodiment of the present invention. A stud 3 is used in place of the slit window 2 described above, and the basic structure is almost the same as FIG. Alternatively, this embodiment is such that the hermetic windows 4 are provided at both ends of the conventional waveguide type filter shown in FIG. That is, the hermetic window 4 is also made of ceramics, and the distance between the stud 3 and the hermetic window 4: L2 is also approximately L2Ｌλg / 4 + nλg / 2λg to prevent ripples in the microwave transmission characteristics. The guide wavelength n = 0, 1, 2,...

The interior of the waveguide 1 is evacuated to a degree of vacuum of 1 × 10 −3 Torr or less or the internal pressure is increased to 1 atm or more by an exhaust pipe 5 installed in the waveguide 1. Then, the exhaust pipe 5 is sealed after decompression or pressurization. The specifications of this waveguide type filter are the same as those in FIG. 1 except for the following items.

The size of the diameter of the stud 3: d 0 = 2.1 mm The interval between the studs 3 (first stage): d 1 = 17.8 mm The interval between the studs 3 (second stage): d 2 = 18.9 mm The interval between the studs 3 (3rd stage): d3 = 17.8 mm Interstage distance (1st stage): D1 = 6.5 mm Interstage distance (2nd stage): D2 = 6.5 mm

FIG. 3 is a schematic view of still another embodiment of the present invention, and FIG. 4 is a side view thereof. This waveguide type filter is called a waffle iron type low-pass filter, and a resonance type dielectric hermetic window 6 is provided at both ends. Then, similarly to the above-described two embodiments, the inside is reduced to a degree of vacuum of 1 × 10 −3 Torr or less, or the internal pressure is increased to 1 atm or more by the installed exhaust pipe 5. Then, the exhaust pipe 5 is sealed after decompression or pressurization.

As described above, in a pulse radar device or the like operating a microwave having a large peak power,
The arcing in the waveguide due to the high-frequency electric field is a problem in terms of the power durability. As shown in the above embodiment, the arcing is performed by reducing or increasing the pressure in the waveguide type filter. Can be suppressed. That is, once the gas pressure is reduced below the atmospheric pressure, the arcing start voltage decreases once. That is, arcing is likely to occur. However, the pressure was further reduced and the degree of vacuum was about 1 × 10
At -3 Torr or less, the arcing start voltage becomes higher than at atmospheric pressure. That is, arcing hardly occurs. On the other hand, when the pressure is sequentially increased from the atmospheric pressure, the arcing start voltage increases accordingly.
That is, arcing hardly occurs. FIG. 5 is a diagram showing the relationship between the pressure reduction or pressurization and the peak power of the microwave at the start of arcing in the embodiment of FIG. It can be seen from this figure that the occurrence of arcing can be suppressed by applying a predetermined pressure reduction or pressure to the inside of the waveguide.

In the above three embodiments, the internal pressure is set to 1
When the pressure is increased to a pressure higher than the atmospheric pressure, the atmosphere may be used. However, if sulfur hexafluoride (SF6) gas is used, a better effect for preventing arcing can be obtained.

[0017]

As described above, the configuration according to the present invention makes it possible to obtain a transmission characteristic exhibiting a sharp attenuation and a high Q value equivalent to those of a conventional waveguide type filter. In addition, a waveguide type filter which has a higher withstand power than a conventional waveguide type filter and a high arcing start voltage, that is, can be easily and inexpensively installed even in a pulse radar device or the like which operates a large microwave. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view of a waveguide type filter using a slit window according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a waveguide filter using studs according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a waffle-iron low-pass waveguide filter according to one embodiment of the present invention.

FIG. 4 is a side view of FIG. 3;

FIG. 5 is a diagram showing a relationship between arcing and microwave power in the embodiment of FIG. 1;

FIG. 6 is a circuit diagram showing a typical structure of a conventional waveguide filter.

FIG. 7 is a schematic diagram of a susceptance: B of FIG. 6 configured by a slit window 2 in a waveguide 1.

FIG. 8 is a schematic diagram of a stud 3 used in the waveguide 1 as the resonance element of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Waveguide 2 ... Slit window 3 ... Stud 4 ... Airtight window 5 ... Exhaust pipe 6 ... Resonant type dielectric airtight window

Claims (3)

[Claims] 1. A plurality of slit windows each having a pair of two partition plates facing each other inside a waveguide, or a plurality of studs each formed by a cylindrical rod are provided so as to allow a necessary frequency component of microwaves to pass therethrough. In a waveguide type filter that blocks unnecessary frequency components, an airtight window for maintaining vacuum tightness is provided at an input end and an output end of the waveguide type filter,
The degree of vacuum inside the waveguide type filter is set to 1.times.10@-3 Torr.
A waveguide type filter characterized by the following. 2. The waveguide type filter according to claim 1, wherein the pressure inside the waveguide type filter is 1 atm or more. 3. The waveguide-type filter according to claim 1, wherein the pressure inside the waveguide-type filter is at least 1 atm using sulfur hexafluoride (SF6) gas. 3. The waveguide type filter according to 2.