DE10057205A1 - Notch filter has hollow volume resonator coupled to waveguide with variable volume hollow chamber, stepper motor or servomotor with which volume of hollow chamber can be varied - Google Patents

Abstract

The device has a waveguide with a hollow volume resonator coupled to it with a variable volume hollow chamber and a stepper or servomotor (3) with which the volume of the hollow chamber can be varied. The volume of the hollow chamber is varied by a piston. The resonator and waveguide are coupled for microwave radiation by a slot-shaped coupling opening. AN Independent claim is also included for an arrangement with an electron tube for heating an electron plasma with microwave radiation of variable frequency.

Description

The present invention relates to a notch filter. This dampens Microwave radiation with an adjustable cavity resonator for the downstream measurement.

Many diagnostic procedures are based on high-temperature plasma physics the application or measurement of microwave radiation by the in plasma enclosed in a magnetic cage is emitted. This Microwaves are used to determine many plasma properties. The most important applications are the determination of the electron temperature of the Plasma and electron density. To measure the electron temperature is the method based on microwave radiation is currently Reliable.

Extremely sensitive diagnostics (P <1 µW) are used for this. The The input stage of the radiometer used therefore consists of a sensitive mixer that has a total frequency band of about 15 GHz covers.

For some time now, heating methods have been used in high-temperature plasma physics used by radiation of microwaves the electron temperature of the plasma significantly. Couple the electron tubes used a power of about 1 MW into the plasma and exactly at a frequency, which is covered by the mixer of the electron temperature diagnostics. The Tube power is only partially coupled into the plasma. On small proportion is reflected on the walls of the plasma vessel and can the input stage of the electron temperature diagnostics still a few watts be.  

However, this performance is sufficient to destroy the passive mixers. Therefore a notch filter is used in all fusion research experiments the electron temperature diagnosis before the unwanted radiation of the To protect electron tubes. A notch filter is one filter of high quality acting as a band stop with a very narrow stop band (Δf <1 GHz).

To partially target the electron plasma with microwave radiation suitable frequency to be able to stimulate electron tubes that allow the frequency to be adjusted within seconds. To do this also the notch filter or the blocking area according to the set one Tube frequency can be adjusted. Every new shot of a Notchfili: he is but only possible in the laboratory. To do this, the setting of the notch filter be changed, and then by a calibration measurement the set Restricted area determined or even the setting can be corrected again. So far, the setting can only be made directly on the notch filter become, which is difficult to access with effective microwave radiation. The The effort to readjust the notch filter is several hours.

The object of the present invention is to provide a notch filter which allows a simple under the new conditions mentioned above To enable measurement of the electron temperature.

This object is achieved by a generic device with the Features of claim 1 solved. Advantageous configurations result from the subclaims.

The claimed device comprises a waveguide. The Waveguide is used to transport the microwaves from the entrance of the Notch filter up to its exit. Generally the waveguide is a thin, elongated hollow body or canal.  

The cross-section of the waveguide is particularly so on the wavelength the radiation that optimal transport of the Microwave radiation is guaranteed.

With a transported frequency spectrum of 90-140 GHz the Microwave radiation (so-called F-band) is, for example right-angled cross-section with dimensions of 2.002 × 1.02 mm.

One or more cavity resonators are attached to the waveguide coupled. These are cavities except for one opening are closed. This small compared to the cavity for example, a round opening is used to couple the cavity resonator to the waveguide.

Standing waves, their frequency, can form in the cavities is ultimately determined by the dimensions of the cavity. radiation this frequency, from the input to the output of the notch filter is transported, standing over the opening in the cavity resonates Waves (resonance). The wave that is transported past becomes this Frequency deprived of power, and it is attenuated or even filtered out.

Attenuate or filter out different frequencies in this way to be able to, the void volume is in at least one of its dimensions variable. This change is made with a stepper or servo motor performed. This ensures that the precisely specified Actuation of the motor (step-by-step or servo-controlled) the change of the cavity is precisely specified. A stepper or servo motor allows that exact adjustment of axes, since it has no caster and also Partial revolutions are possible without gear. There is a servo motor result, for example, as advantageous since it is cheaper to acquire.  

The frequency to be damped can thus be set in a targeted manner. at In contrast, known notch filters must be time-consuming Adjustment procedure of the cavity resonator readjusted and measured become.

According to one embodiment of the invention, the change in Cavity caused by a piston.

The piston consists, for example, of a movable head that mounted inside the cavity and via a rod from the servo or stepper motor can be moved along an axis. The cavity has at least one breakthrough for the rod for this.

Moving the piston head can cause waves of other Form frequency standing waves. This is for different Frequencies the damping effective.

The movable piston head closes, for example, close to the Sidewalls of the cavity and is on the side facing the cavity Flat side. The two measures have the effect that waves that are as good as possible at exactly one frequency in the cavity can train without losses. As a result, there is a pronounced one Attenuation exactly at a frequency that is used to train standing Has caused waves.

For a single spatial direction, the resonance condition is that the length this spatial direction is an integer multiple of half the wavelength corresponds to the radiation used in the cavity. Is therefore given Wavelength the length of this spatial direction correspondingly over the piston set, standing waves, i.e. resonance, occur.  

With an appropriate cavity, the resonance condition in the different spatial directions are met, and the so-called fashions.

In the frequency spectrum, the number of modes increases with increasing frequency to and the frequency gaps in between get smaller until the resonances occur quasi-continuously. Are the resonances of the cavity in the Frequency band close together, the damping no longer occurs exactly these frequencies, but appears weaker and broadband.

The cavity resonator is therefore preferably designed such that its Dimensioning (plus, the stroke of the piston) essentially only a few corresponds to half the wavelengths of the microwave radiation used. As a result, only the basic modes can be formed. This means, that the resonance condition can only be met for small whole numbers.

A cylindrical cavity with a diameter of 4 mm and one Adjustment range (by piston stroke) from 0 to approx. 9 mm for example as suitable for frequencies around a center frequency of 110 GHz exposed to microwave radiation.

According to the features of claim 3, the coupling between Waveguide and cavity caused by an opening. With that the Waveguide directly on the resonance body. It is avoided class by a coupling device such. B. Another head of losses and / or disturbing reflections of the microwave occur. The specialist is responsible for the shape, size and position of the coupling opening optimize so that the filter strong attenuation and strong Has steepness. To have strong damping, a lot has to be done Power of the wave transported past can be withdrawn by resonance. In order to achieve a steep slope, the must be at a certain Frequency resonance particularly pronounced and sharp (exact) his. By measuring the damping and its course depending on the Such an optimization can be carried out frequency.  

For example, there is a slot-shaped coupling opening and one Dimension of 0.7 × 1.4 mm and a central position in the to Waveguide lying side of the cavity as favorable.

According to claim 4, the notch filter, ie waveguide and / or walls of the cavity resonator, made of gold, or at least are surfaces those in "contact" with the microwave radiation are gilded.

In general, the material of the notch filter is chosen so that it is made of electrically very conductive material. for example brass. A Gilding or gold on the inside of the conductor and / or resonator increases the conductivity and thus the transportability of the conductor for the microwave radiation. This ensures that the Microwave radiation if possible without attenuation by the waveguide passes through and therefore no broadband filter effect of the waveguide occurs.

According to claim 5, more than 4 cavity resonators on the Waveguide coupled. As a result, all cavity resonators work attenuating the microwave radiation transported through the conductor. are the cavity resonators are set to different resonance frequencies, each has a dampening effect on different frequencies Microwave radiation. All cavity resonators are preferred at the same time set to a frequency in order to achieve a particularly strong damping for To achieve microwave radiation of this frequency. For example, through 6 coupled cavity resonators, which are connected to a common Resonance frequency are set, an attenuation of 60 dB is achieved become.

The plurality of cavity resonators are preferably on the waveguide in this way attached that their coupling openings approximately a distance from one have half the wavelength of the microwave frequency to be attenuated. This ensures that the cavity resonators are connected to the  Places of the wave transported past have a dampening effect on those the wave is in a vibration state with large amplitudes located. So can the dampening effect of each Cavity resonators can be particularly effective.

For example, the distance is one that is effective for the F-band Notch filter 5.5 mm between the coupling openings of the individual Cavity resonators.

According to one embodiment of the invention, the cavity resonators are only attached to one side of the waveguide so as to manufacture the Simplify notch filters and make them cheaper.

According to claim 7, the one provided with a plurality of cavity resonators Notchfilter a device that allows simultaneous adjustment of all Notch filter causes. The device thus enables the servo or Stepper motor changed all void volume at the same time. This will avoided that each individual cavity resonated by one individual Motor must be driven and the notch filter is particularly expensive is and can be dimensioned less compact.

For example, all cavity resonators are of the same size and Form arranged in parallel next to each other. The rods of the pistons in the Cavity resonators are arranged in parallel, all face the same Direction and all ends of the piston rods are over a lead angle connected. This is along the stepper or servo motor Route back and forth, which ultimately through the possibility of movement the piston is determined.

Thus, an adjustment caused by the motor acts on the Lead angle and on the pistons simultaneously and to the same extent the volume of the cavity resonators.  

The guide angle has two in the preferred embodiment surfaces standing at right angles. A surface is used to attach the Piston. The other surface is connected to the motor and lies at the same time flat but flexible on a base. Due to the large surface area can be a game in the float of the lead angle avoided, which lead to an inaccurate frequency setting would. In particular, there would be a different frequency setting or volume setting of the resonators, if these by different directions of movement (pushing or pulling) of the motor have been achieved.

All cavity resonators are preferably of the same volume set, and the change in these volumes is simultaneously increased by the made the same amount in all cavity resonators. this will achieved, for example, in that all cavity resonators are the same Have dimensions.

According to claim 8, the above-mentioned device for simultaneous Adjust all cavity resonators on an adjustment that it allows the individual volumes of the cavity resonators to be adjusted easily, without having to disassemble the notch filter. This can a volume difference between the individual cavity resonators can be set by the effect of the adjustment device by the uniform adjustment is retained. In particular, it allows Adjustment device, this volume difference between the individual Adjust cavity resonators to almost zero.

Manufacturing tolerances the different volumes of the Cavity resonators can be compensated for. So that will ensures that the cavity resonators are almost exactly the same Frequency dampening effect.

According to claim 9, the volume of the cavity resonators is adjusted the distance between the piston head and the guide angle, i.e. the effective one  Length of the piston rod changed. With the distance between Lead angle and the cavity resonators becomes the individual Volume of one of the cavity resonators changed.

According to claim 10, the means for adjusting, for example the Guide angle, provided with a bore with an internal thread. each of the individual piston rods is on the free towards the adjusting means Threaded end and are thus in the through hole screwed. On the side beyond the piston head is the Piston rod with a screw slot or with a hexagon socket provided to the piston rod with respect to the means for adjusting to be able to twist. According to a preferred embodiment, this includes the pistons together with the piston rod are rotatable around the piston rod in the individual cavity resonators attached.

This determines the length of the piston rod with respect to the guide angle effective length, set. By turning the piston rod in the The thread of the guide bracket can be used with the distance between Lead angle and the cavity resonators the individual volume of a the cavity resonators are changed.

A once made adjustment is made by a second screw pro Piston rod secured.

This at right angles to the piston rod in the means for adjustment, For example, the guide angle, screwed screw pushes in screwed in condition with its tip at right angles or at least in acute angle on each piston rod and thus fixes it against unintentional twisting.

The use of a servo or stepper motor in the claim embodiment is particularly advantageous because This is a remote-controlled adjustment due to its electronic control of the notch filter allowed. This enables a change in that  Notchfilter make during this the microwave radiation is exposed. An interruption in the measurement of microwave radiation can be largely avoided. A motor can do this Make changes faster because with known notch filters the Cavity is adjusted by a screw that is not as quick by hand can be twisted as it is achieved by an engine.

Fig. 1 shows a side view of the preferred embodiment. The servo motor 3 is attached to a holder 1 . The holder 1 has a base 2 , to which the parts are attached, which have the waveguide and the cavity resonators. These parts consist of block 6 , counterpart 8 and spacer 7 . In block 6 , nine cavities 10 formed by drilling are provided, which serve as cavity resonators, as shown in the sectional view through these parts in FIG. 2.

These holes, which are open on both sides, are closed with the spacer 7 on the side lying opposite the counterpart 8 except for the coupling openings 13 . On the other hand, the cavity is closed off by the movable piston head 9 . The piston head 9 is movable over the piston rod 5 .

As shown in FIG. 1, the piston rod 5 is fastened to the guide bracket 4 , which is moved in parallel to the piston rod 5 by the servo motor on one of its angular surfaces.

As further shown in FIG. 2, the counterpart 8 has a milled groove 12 which extends over the entire length of the counterpart 8 . Another groove 11 made in the spacer 7 lies on the groove 12 of the counterpart when the counterpart 8 and spacer 7 are brought together. The cavity formed by the two grooves 11 and 12 along the counterpart 8 is the waveguide.

As the detailed view in FIG. 3 shows, the groove introduced in the spacer 7 is provided on the side facing the block 6 with nine coupling openings 13 in such a way that the cavity resonators 10 are in “contact” with the waveguide formed by the grooves 11 and 12 ,

According to claim 11, the device according to the invention consists of a Electron tube with a microwave radiation in a magnetic Enclosed electron plasma heated. At the same time Microwave radiation emitted by the plasma, the conclusions about the Plasma properties enabled. To the latter lower performance To be able to measure microwave radiation, the measuring device of the Radiant heat with a notch filter set to this frequency largely shielded.

According to an embodiment of the invention, the Measuring device a passive mixer, a local oscillator and one Detector.

Claims (13)

1. Notch filter with a waveguide ( 11 , 12 ), with a cavity resonator ( 10 ) coupled to it, with a cavity which can be changed in volume, with a stepping or servo motor ( 3 ) with which a change in the cavity volume can be carried out. 2. Notch filter according to claim 1, with a piston ( 9 , 5 ) which causes the change in the cavity. 3. Notch filter according to one of the preceding claims, with a coupling opening ( 13 ) with which the cavity resonator ( 10 ) and the waveguide ( 11 , 12 ) for microwave radiation are connected and which is slit-shaped. 4. Notch filter according to one of the preceding claims, made of gold or at least with gold-plated surfaces in the cavity resonator and / or in the waveguide. 5. Notch filter according to one of the preceding claims, with more than 4 coupled along the waveguide cavity resonators ( 10 ). 6. Notch filter according to one of the preceding claims, with coupled along only one side of the waveguide cavity resonators ( 111 ). 7. Notch filter according to the preceding claim, with means ( 4 ) which bring about a simultaneous and uniform adjustment of the cavity volumes of the cavity resonators. 8. Notch filter according to claim 7, wherein the means for simultaneous Adjusting the cavity volume of all cavity resonators using means are provided for adjusting the individual cavity volumes. 9. Notch filter according to claim 8, wherein the means for adjusting the individual cavity volume from an effective length adjustable Piston rod exist. 10. Notch filter according to claim 8 or 9, wherein the piston rod with Thread is provided, which is screwed into the means for adjustment is the means for adjustment with a perforation and with a Internal threads are provided with the piston rod at its free end is provided with a slot or hexagon through the piston rod a screw is secured against rotation. 11. Device with an electron tube for heating a Electron plasma with a microwave radiation of variable Frequency, with a measuring device for microwave radiation, with a Notch filter according to one of the preceding claims. 12. The apparatus of claim 11, wherein the measuring device for Microwave radiation a mixer, an oscillator and a detector includes. 13. Use of the notch filter according to one of the preceding Requirements for filtering a frequency of 60 dB to be masked out over 50 GHz and a filter width of less than 1 GHz.