DE102009046463A1 - Coaxial slit-coupled resonator duplexer - Google Patents

Abstract

The invention describes a coaxial slot-coupled resonator diplexer, based on the use of different eigenmodes of an electromagnetic resonator for the coupling of at least two high-frequency waves of high power and different wavelengths into a coaxial multimode waveguide. This function is of great interest, for example, in superconducting high-frequency resonators for accelerating elementary particles. Another possible application is in radar technology.

Description

The invention relates to a diplexer based on the use of different eigenmodes of an electromagnetic resonator for the coupling of at least two high-power and different wavelength high-frequency waves into a coaxial multi-mode waveguide. This function is of great interest, for example, in superconducting high-frequency resonators for accelerating elementary particles. Another possible application is found in radar technology.

It is known to use the electromagnetic alternating field (TM ₀₁₀ mode) of a metallic radio frequency (RF) cavity resonator for accelerating elementary particles. Due to the lower thermal losses superconducting resonators are preferred for continuous (CW) operation. During acceleration, energy is removed from the electric field. In order to ensure a constant field and thus a constant acceleration, the loss must always be compensated.

It is also known that the power required for this, on the order of a few tens of kilowatts, is coupled laterally outside the resonator into the radiant tube. In this case, HF main couplers specially adapted to the frequency and power range are used [ V. Veshcherevich et al .: Input coupler for ERL Injector Cavities. Proceedings of the Particle Accelerator Conference 2003, p. 1201 ].

Based on this principle of acceleration, superconducting HF electron sources are also known [ DE 10 2004 055 256 B4 ]. They consist of an RF resonator, which contains a cathode on one side. On the opposite side is the jet pipe. When using a photocathode, it is illuminated with a laser beam and emits electrons. With appropriate synchronization of the laser pulse with respect to the RF phase, the electrons are accelerated by the RF field of the resonator and the electron beam leaves the source through the beam tube.

In order to improve the beam properties, in particular the transverse emittance for medium and high powers, the possibility of using an additionally coupled into the resonator transversal mode (TE mode) higher frequency is known DE 10 2004 005 612 B4 ], but not yet practically proven.

The power required to excite this TE mode must be supplied to the resonator via an additional coupler. This requires a redesign of the known resonators, in particular the coupler section. An exchange would only be possible with an unreasonably high effort. Nevertheless, in order to be able to improve the beam characteristics of existing resonators, without modification of them, the use of the existing coaxial waveguide structure of the main coupler is proposed.

The object of the invention is the coupling of at least one further high-frequency wave of higher frequency into an already existing coaxial waveguide structure.

The object is achieved with the resonator structure according to claim 1.

The solution to the problem is explained with illustrations.

shows the structure for explaining the principle of the coaxial resonator duplexer.

shows the arrangement of the resonator (shaded) between the existing elements of the RF main coupler in the embodiment.

shows the structure of the resonator in the embodiment

shows two sectional drawings of the structure of the resonator of the embodiment.

shows the magnitude of the electric field of all TM modes up to 3 GHz. The modes with an electric field component on the resonator axis are degenerate by the coaxial arrangement of the inner conductor, but should still be referred to as TM _0n0 modes according to the usual counting method for cylinder resonators.

The modes shown are: a) TM010 (0.71 GHz), b) TM110 (1.24 GHz), c) TM210 (2.03 GHz), d) TM020 (2.50 GHz), e) TM120 (2 , 57 GHz), f) TM220 (2.80 GHz), g) TM310 (2.80 GHz).

shows the simulated (-) and measured (- -) influence of the tuning punch length in mm on the rejection frequency in MHz of the choke filter (a) and the coupling resonator (b).

shows a comparison of the most important simulated and measured S-parameters.

shows the dependence of the transmission loss for different waveguide modes.

• – einfache und kostengünstige Integration der Erfindung in die bestehende Wellenleiterstruktur
• – hohe Isolationsdämpfung zwischen den Frequenzbereichen bei gleichzeitig geringer Einfügedämpfung
• – Eignung für Leistung bis 10 kW CW (L-Band)
• – Erhaltung der rotationssymmetrischen TEM Feldverteilung trotz mehrmodigen koaxialen Wellenleiters.

The use of this structure is shown using the example of a superconducting electron source. In the realization of the task, there are different requirements:

• - Simple and inexpensive integration of the invention in the existing waveguide structure
• - High insulation loss between the frequency ranges with low insertion loss
• - Suitability for power up to 10 kW CW (L-band)
• - Maintenance of the rotationally symmetric TEM field distribution despite multi-mode coaxial waveguide.

The object of the invention is achieved by a coaxial cylindrical resonator structure (hereinafter referred to as resonator duplexer), which is arranged around the waveguide. With this arrangement, it is possible to couple at least one second high-frequency wave of frequency f ₂ into an already existing coaxial waveguide structure of frequency f ₁ . The component thus corresponds in its function to a diplexer, but can also be expanded as needed to form a multiplexer with multiple inputs. In principle, it does not matter whether the frequency f _{2 to be} coupled in is greater or smaller than the frequency f ₁ already carried in the waveguide.

shows a simplified schematic diagram for a resonator duplexer 1 with three ports 7 to 9 , According to the invention, a coaxial resonator duplexer 1 around the coaxial waveguide 2 appropriate. The inner radius of the coupling resonator corresponds to this 3 the radius of the mantle 17 of the waveguide 2 , The choice of the outer dimension is made by the port 2 8th to be coupled frequency f ₂ and thus by a eigenmode of the coupling resonator 3 established. Between the outer coat 17 of the waveguide 2 and the coupling resonator 3 is located perpendicular to the axis of rotation of the waveguide a coupling gap 4 , The height of the coupling gap 4 to the waveguide 2 determines the bandwidth of the coupling. The narrower the gap, the narrower the coupling bandwidth.

At the port 2 8th is through the appropriate choice of coupling 14 (capacitive / inductive) a eigenmode of the frequency f _{2 of} the coupling resonator 3 (preferably TM _0x0 modes) excited and built up an electromagnetic field with a specific energy content. Part of this energy will now pass over the gap in the waveguide 2 coupled and in equal parts (-3 dB) in the direction of port 1 7 and 3 9 divided up.

By using a second resonator (choke filter) 5 at a distance of λ / 4 (f ₂ ) to the coupling gap 4 of the first resonator 3 , which becomes Port 1 7 wandering wave completely reflects and overlaps constructive with that to port 3 9 current share. The coupling to the waveguide 2 also takes place via a coupling gap 6 ,

The eigenmode of the choke filter 5 must, for maximum reflection, the field distribution of the traveling wave in the waveguide 2 and have the frequency f ₂ . For the standard case of a TEM wave in the coaxial waveguide 2 this eigenmode would be rotationally symmetric. If both requirements are met, the choke filter behaves 5 as an open-circuit and the power is completely reflected without phase shift.

Occurring manufacturing tolerances of both resonators 3 . 5 are made by using appropriate tuning stamps 11 . 13 in both resonators 3 . 5 protrude, balanced. The manual tuning of the self-resonances allows both resonators 3 . 5 tune to the desired frequency (f ₂ ) with a very high frequency accuracy.

Due to the frequency selectivity of the coupling resonator 3 will be on port 1 7 coupled wave with the frequency f ₁ at port 2 8th also heavily steamed. However, this only applies if the waveguide mode is not connected to a eigenmode of the coupling resonator 3 couples and both frequency bands of the resonator duplexer 1 are sufficiently far apart to prevent crosstalk (some bandwidths of the resonator modes). If this is ensured, the resulting insulation damping allows the coupling high performance at port 1 7 (a few kW) with low power at port 2 8th with a simultaneous low insertion loss to the output at port 3 9 ,

The main advantage of the concept presented is that even in multi-mode coaxial waveguides 2 above the cut-off frequency (the first propagatable waveguide mode) to ensure rotationally symmetric coupling to the TEM fundamental. This is important, for example, for applications in which the dimensions are chosen as large as possible in order to enable the transport of high power (at f ₁ ). In this case, the uniqueness range of the TEM wave is very small and a defined coupling of f ₂ would not be possible above the cut-off frequency without the invention.

embodiment

The use of a transversal electric mode to improve the transverse emittance will be investigated for the first time on a superconducting photoelectron source. The coaxial slit-coupled resonator duplexer 1 becomes between the existing elements of the RF main coupler of the photo-electron source 10 built-in.

The PE ₀₁₁ mode to be examined has a resonance frequency of 2.5 GHz and is intended to be transmitted via the coaxial main coupler 10 be stimulated. Its main task is to provide the RF power of 10 kW at 1.3 GHz required for accelerating the electrons to the resonator. There must be a suitable adaptation of the concept presented above to the energy required to build up the additional field in the already existing coaxial waveguide 2 to ensure the fundamental ( ).

Of particular importance in the development of a suitable coupling are the geometric dimensions of the waveguide 2 , The waveguide 2 leads, due to the large outer diameter at the beginning of Resonatordiplexers 1 (D = 76.5 mm at an impedance of 50 Ω) in addition to the desired TEM wave from 1.76 GHz and a TE ₁₁ -like circular waveguide shaft. In the further course towards the end, the waveguide tapers 2 at constant impedance, whereby the cut-off frequency of this TE _11-like mode increases and thus the transmission loss at f ₂ = 2.5 GHz increases sharply. From this follows the central requirement that the coupling via the rotationally symmetric TEM wave of the waveguide 2 must be done ( ). This also requires the field distribution in the coupling resonator 3 be rotationally symmetric, whereby only monopolistic modes come into question.

A realization of the presented concept is in and shown. Here, the TM ₀₂₀ mode of the coupling resonator 3 used. Its electrical and magnetic field components point in the radial direction, ie perpendicular to the axis of rotation, two. Maxima on ( ). The inner maximum of the magnetic component couples directly to the H _φ component of the TEM wave in the coaxial waveguide 2 , The use of the TM ₀₂₀ mode provides a good size compromise. Due to the desired frequency, it does not result in a too small coupling resonator (TM ₀₁₀ mode) or too large, as would be the case for higher monopole modes. In addition, the electric field is distributed in each case to the region of the coupling slot and that of the actual resonator. Thus, the TM ₀₂₀ mode is only slightly disturbed by the coupling to the Koaxialeiter.

The design of the coupling resonator 3 must meet the conditions that no other monopole mode has the natural frequency f _{1 of} the fundamental wave. Ie. the existing TM ₀₁₀ mode must be as far below the fundamental frequency of 1.3 GHz, so as not to be excited by it. The choice of the radius first decides for all monopole modes over their frequency. The coupling gap is used for further separation of the TM ₀₁₀ and TM ₀₂₀ modes 4 in the coaxial waveguide 2 , For both modes, the electric field is located in this area.

It is known that according to Slater [ LC Maier, Jr. et al .: Field Strength Measurements in Resonant Cavities. Journal of Applied Physics (23), 1952, p. 68-77 .] a change in volume also results in a change in frequency. The following applies:

However, the influence on the TM ₀₁₀ mode is greater because its electric field is concentrated exclusively on the coupling region. The shift of the self-resonance is therefore not for both Fashions alike. A further separation takes place by the use of a double ring in the region of the second external electric field maximum. A volume change in this range allows a shift of the desired resonant frequency within certain limits without significantly affecting the TM ₀₁₀ mode.

The height of the coupling gap 4 to the coaxial waveguide 2 determines not only the bandwidth but also the strength of the coupling. The smaller the gap, the narrower the bandwidth and the weaker the coupling ( ).

The power required to build the TM ₀₂₀ mode becomes the coupling resonator 3 symmetric over two opposing capacitively coupled coaxial 50 Ω. coupling pins 14 fed. This ensures that only the rotationally symmetric TM ₀₂₀ mode and not the TE ₁₁ resonance of the same frequency is excited. Separation of these two modes is achieved by inserting two opposing tuners. 11 / Separation stamp 12 reached at the location of the minimum electric field of the TM ₁₂₀ mode. Thus, its resonant frequency remains largely undisturbed, while the TM ₀₂₀ mode undergoes a negative frequency shift when immersing the tuner. The tuner stamp 11 are adjustable realized and serve to compensate for manufacturing tolerances. The separation stamp 12 are fixed but interchangeable and can be adapted as needed.

As well as the manufacturing tolerances of the choke filter 5 To be able to compensate is also this with two movable Tunerstempeln 13 Mistake. All stamps 11 . 13 are with suitable bushings 15 provided to meet the vacuum requirements. The use of more than ever a pair of stamps 11 . 13 and / or the movable execution of the separation punches 12 is possible, but not economically justifiable. ( . )

The tuning range of the coupling resonator 3 is about 100 MHz, that of the choke filter 5 at 40 MHz ( ). Both are sufficient to compensate for the usual manufacturing tolerances.

shows the simulated S-parameters of the embodiment. The transmission loss of port 2 8th to the superconducting acceleration resonator at port 3 9 is for 2.5 GHz S ₃₂ = -0.05 dB. The transmission of the fundamental wave to port 3 with S ₃₁ = -0.07 dB at 1.3 GHz provides comparably good values. The isolation of both ports is S ₂₁ ~ -37 dB at 1.3 GHz and S ₁₂ ~ -40 dB at 2.5 GHz. The S-parameters of the simulation and also the measurement confirm the function of the resonator duplexer 1 ,

Because the resonator duplexer 1 is to be operated on a superconducting electron source, a vacuum capability of the embodiment is required up to a pressure of 10 ^-7 mbar. This is done by suitable sealing and implementation and the manufacture of the resonator duplexer 1 made of oxygen-free copper. To reduce RF losses, the entire internal surface is polished. To avoid field strength peaks and corners, all critical areas have a radius of 1 to 3 mm.

Simulations of the multipacting and flashover tendency as well as the thermal behavior at maximum power show no restriction of the usability of the embodiment.

In the particular embodiment, the wall thickness of the resonator duplexer is determined by the stiffness required to minimize deformation due to the pressure differential and the attached fittings.

LIST OF REFERENCE NUMBERS

1

Coaxial slit-coupled resonator duplexer

2

coaxial waveguide

3

Koppelresonator

4

Coupling gap of the coupling resonator 3

5

Chokefilter

6

Coupling gap of the choke filter 5

7

Port 1 (f ₁ )

8th

Port 2 (f ₂ )

9

Port 3 (f ₃ = f ₁ + f ₂ )

10

RF main coupler of the photo-electron source

11

Tuner temple coupling resonator 3

12

separation stamp

13

Tuner stamp choke filter 5

14

Coupling pin for coupling f ₂ in the coupling resonator 3

15

Vacuum rotary feedthrough

16

Inner conductor of the waveguide 2

17

Outer conductor (sheath) of the waveguide 2

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004055256 B4 [0004]
• DE 102004005612 B4 [0005]

Cited non-patent literature

• V. Veshcherevich et al .: Input coupler for ERL Injector Cavities. Proceedings of the Particle Accelerator Conference 2003, p. 1201 [0003]
• LC Maier, Jr. et al .: Field Strength Measurements in Resonant Cavities. Journal of Applied Physics (23), 1952, pp. 68-77 [0033]

Claims (7)

Coaxial slit-coupled resonator duplexer for coupling at least one further high-frequency wave of frequency f ₂ into a coaxial waveguide of frequency f ₁ , characterized in that a. the resonator is arranged around the waveguide, b. the resonator has a coupling gap, which determines the bandwidth and the strength of the coupling. c. a choke filter of frequency f _{2 is used} at a distance of λ / 4 to Einkoppelstelle Coaxial slit-coupled resonator duplexer according to claim 1, characterized in that a suitable double ring is used for the separation of the different monopole modes. Coaxial slit-coupled resonator duplexer according to one of the preceding claims, characterized in that the resonator duplexer is made of oxygen-free copper and in conjunction with suitable seals in order to be able to be used in a vacuum. Coaxial slit-coupled resonator duplexer according to one of the preceding claims, characterized in that the material is polished and / or that all corners and edges are provided with a radius. Use of the coaxial slot-coupled resonator according to claim 1, characterized in that a TM ₀₂₀ resonator mode for rotationally symmetrical coupling (via the H _φ component) of a TEM wave into a multi-mode coaxial waveguide takes place. Use according to claim 5, characterized in that a symmetrical excitation of the TM ₀₂₀ mode via at least two opposing capacitive coupling pins. Use according to claim 5, characterized in that an adaptation of the TM ₀₂₀ mode and a separation of the TM ₁₂₀ mode is performed by Tuningstempel.

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