EP1603187B1 - Cavity resonator, use of the cavity resonator in a oscillation circuit - Google Patents

Description

The present invention relates to cavity resonators and their use especially in oscillator circuits.

Resonators are important components that are used in a wide variety of applications. For example, microwave systems require high-quality resonators used in filters and resonators (oscillators). One has to make a choice between cavity resonators and dielectric resonators, where size, weight, cost and other aspects can play a role.

Cavity resonators in the various known embodiments undergo a change in resonant frequency with temperature change, which is undesirable for most applications. A change in temperature may result from a change in ambient temperature, from a temperature change in an integrated oscillator circuit, or from losses occurring in the resonant cavity. A change in temperature results in a Change in the dimensions of the resonator, which leads to the mentioned change in the resonant frequency.

There are several approaches to reduce the influence of temperature on resonators. For example, it is possible to reduce the resonant frequency change caused by a temperature change by inserting a dielectric member into the cavity, the dielectric member having to have a suitable temperature coefficient of dielectric permittivity.

Another possibility is to build a cavity made of different materials with different coefficients of thermal expansion. This possibility is well known and is used for so-called "coaxial re-entrant cavity" resonators. An example of such a resonator is, for example, in US Pat Japanese Patent JP 52075154 , which was published on 23.6.1977 described. Fig. 1A and 1B show a resonator 10 according to this Japanese patent in a much simplified representation. Like from the Fig. 1A and 1B can be seen, there is a rod 12, which co-axially penetrates into a cavity 11 of the resonator 10. In Fig. 1A a low temperature state T is shown. When the temperature is increased to T ', the cavity 11 expands, as in FIG Fig. 1B indicated by arrows along the circumference. The rod 12 becomes longer at a temperature increase. If the materials of the cavity 11 and the rod 12 are chosen such that the rod 12 undergoes a smaller expansion, the so-called capacitive gap (area 13) between the lower rod end and the lower wall of the cavity 11 becomes larger. This change in the capacitive gap (reduction of the capacitive load of the resonator with temperature increase) in the region 13 results in that the resonant frequency of the resonator 10 remains relatively constant over a certain temperature range. A disadvantage of such a re-entrant cavity resonator 10 is the relatively poor quality factor Q. Especially at high frequencies above 10 GHz, the quality factor Q degrades rapidly due to the high field concentration in the capacitive gap and its immediate environment.

There are other resonators equipped with means for compensating the influence of temperature. These types of resonators are also referred to as "clamped cavity" resonators. An example of such a resonator is the U.S. Patent No. 2,528,387 refer to. The cavity of the resonator is designed according to this approach so that the geometric changes that would normally result from a temperature change are locally limited or even suppressed. This can be done by a suitable choice of materials and measures which ensure that the volume of the resonator is kept constant by compensating for an increase in the cross-section by reducing the length. Other similar examples are the US Pat. Nos. 4,706,053 and US 6,529,104 which also suggest ways and means to keep the volume of a resonator approximately constant with a temperature increase.

In the US 5,867,077 is specifically about a temperature-compensated microwave filter.

Other resonators, in turn, are made of Invar® or similar materials that have a low coefficient of thermal expansion. Invar is expensive and difficult to work with.

Based on the above-mentioned prior art, the object is to provide a resonator which prevents or reduces a change in the resonant frequency with temperature change. Moreover, it is according to the invention to provide a resonator that is inexpensive.

It is a further object of the invention to provide various uses for such a novel resonator with temperature compensation and corresponding oscillator circuits.

According to the invention, a cavity resonator is provided, the volume of which increases with an increase in temperature, respectively decreases with a decrease in temperature, without the resonant frequency experiencing a greater change. To achieve this, the Cavity resonator a pot and at least one cover, which are made of materials with different coefficients of thermal expansion, wherein the at least one cover has a greater coefficient of thermal expansion than the pot. Although both parts of the cavity resonator, namely the pot and the cover contribute to an increase in the cavity volume with an increase in temperature, the resonant frequency can be kept substantially constant with a suitable choice of waveguide mode, as the cover bulges outwards by suitable shaping and thereby a low-field zone forms in the region of the cover.

In order to achieve the aforementioned object, a cavity resonator with the features according to claim 1, the use of a cavity resonator with the features according to claim 16 and an oscillator circuit having the features according to claim 17 is provided.

Further inventive embodiments of the cavity resonator can be found in the dependent claims 2 to 15 and further inventive embodiments of the oscillator circuit can be found in the dependent claims 18 to 19.

Fig. 1A, 1B

eine schematische Schnittdarstellung eines konventionellen re-entrant cavity Resonators, wobei Fig. 1A den Zustand bei einer Temperatur T und Fig. 1B bei einer höheren Temperatur T' darstellt;

Fig. 2

eine schematische Ansicht eines Hohlraumresonators in einer ersten Ausführungsform der Erfindung;

Fig. 3A, 3B

eine schematische Darstellung der Intensitätsverteilung der elektrischen Feldstärke in einem Hohlraumresonator gemäss Erfindung, wobei Fig. 3A den Zustand bei einer Temperatur T und Fig. 3B bei einer höheren Temperatur T' darstellt;

Fig. 4A, 4B

eine schematische Schnittdarstellung eines konventionellen Hohlraumresonators, wobei Fig. 4A den Zustand bei einer Temperatur T und Fig. 4B bei einer höheren Temperatur T' darstellt;

Fig. 4C, 4D

eine schematische Schnittdarstellung eines Hohlraumresonators gemäss Erfindung, wobei Fig. 4C den Zustand bei einer Temperatur T und Fig. 4D bei einer höheren Temperatur T' darstellt;

Fig. 5

eine schematische Schnittdarstellung einer Schaltung mit einem Hohlraumresonator in einer weiteren Ausführungsform der Erfindung;

Fig. 6

ein schematisches Blockdiagramm einer weiteren Schaltung mit einem Hohlraumresonator in einer weiteren Ausführungsform der Erfindung;

Fig. 7

eine schematische Schnittdarstellung eines Hohlraumresonators in einer weiteren Ausführungsform der Erfindung.

The invention is described in detail below, based on exemplary embodiments illustrated in the drawings. Show it:

Fig. 1A, 1B

a schematic sectional view of a conventional re-entrant cavity resonator, wherein Fig. 1A the condition at a temperature T and Fig. 1B at a higher temperature T 'represents;

Fig. 2

a schematic view of a cavity resonator in a first embodiment of the invention;

Fig. 3A, 3B

a schematic representation of the intensity distribution of the electric field strength in a cavity resonator according to Invention, wherein Fig. 3A the condition at a temperature T and Fig. 3B at a higher temperature T 'represents;

Fig. 4A, 4B

a schematic sectional view of a conventional cavity resonator, wherein Fig. 4A the condition at a temperature T and Fig. 4B at a higher temperature T 'represents;

4C, 4D

a schematic sectional view of a cavity resonator according to the invention, wherein Fig. 4C the condition at a temperature T and Fig. 4D at a higher temperature T 'represents;

Fig. 5

a schematic sectional view of a circuit with a cavity resonator in a further embodiment of the invention;

Fig. 6

a schematic block diagram of another circuit with a cavity resonator in a further embodiment of the invention;

Fig. 7

a schematic sectional view of a cavity resonator in a further embodiment of the invention.

Detailed description:

In the following, terms are explained and defined that appear several times in the description and the claims.

The cavity resonator is a component which oscillates in a predetermined wavelength range, for example in the microwave range. As the term "cavity resonator" implies, such a resonator has a cavity whose walls form a body which substantially encloses the cavity. This body is referred to herein as a pot regardless of its actual shape. Typically, such a cavity has, for example, the shape of a cylinder, a prism or a sphere and the walls are made of metal or a metal layer, wherein the metal or metal layer has a very high electrical conductivity. Particularly suitable are copper, a copper alloy (for example CuW), gold or silver, or a superconducting material, to name a few examples.

Unlike the previously known approaches, a cavity resonator is provided according to the invention, the volume increases in a temperature increase, respectively, reduced at a temperature drop, without causing the resonant frequency undergoes a greater change. Embodiments will be described below, and the operation will be explained with reference to the embodiments.

A first embodiment of the invention is in Fig. 2 shown. Shown is a schematic view of a cavity resonator 20. The cavity resonator 20 has a cylindrical pot 21 with a bottom 21.1 and a cover 22, which together enclose a cavity resonance volume V. The cavity resonator 20 is characterized in that the pot 21 comprises a first (metallic) material having a first coefficient of thermal expansion α1. The cover 22, however, comprises a second (metallic) material having a second coefficient of thermal expansion α2. According to the invention, the second temperature expansion coefficient α2 is greater than the first coefficient of thermal expansion α1, ie α2> α1. This leads to an expansion of the pot 21 and a deformation of the cover 22 resulting in an increase in temperature, which together cause an increase in the cavity resonance volume V when the cover 22 is curved outwards (the outer curvature will be under the conditions described increase with temperature increase).

In the embodiment shown, the pot 21 has a cylindrical shape with a radius R and a (resonator) height H. As a cover 22 is a dome-shaped element having a height .DELTA.H and a length P. The pot 21 and the cover 22 are arranged rotationally symmetrically about the axis 23. The rotational symmetry is advantageous for the manufacturing process (Turning), but is not essential to the basic operation of the inventive compensation.

The resonance frequency f _R , _{TM010 of} the TM ₀₁₀ mode in a cavity resonator with a purely cylindrical cavity does not depend on the height H of the pot and is given by the following equation: $$f_{R.\mathit{TM}010}=0.38274\cdot \frac{c}{R}.$$

where c is the speed of light and R is the radius of the pot. For the present case (0 <ΔH << H), the field distribution is similar to that of the TM010 mode. The above formula is approximate, so it can be used as a good first estimate in the design process. The fact that the resonance frequency is independent of H is also valid only for ΔH = 0, otherwise there is a slight dependence (higher order effect) of the resonance frequency on the height H. For this TM _010- like mode, if the pot 21 were made of a metal having a thermal expansion coefficient α1, the temperature coefficient of the resonance frequency is -α1. According to the invention, a cover 22 is now provided, the temperature expansion coefficient α2 is greater than the first coefficient of thermal expansion α1 of the pot 21. This causes the cover bulges outward at a temperature increase. For example, if the cover 22 is dome-shaped, as in FIG Fig. 2 shown, the "dome" sharpener and it results in a total volume of the cavity V 'which is greater than the original volume V (with both the volume of the pot and that of the dome increase).

In addition to increasing the volume from V to V ', there is also a change in the geometric conditions in the region of the cover 22. The influence of the change in volume and geometry on the electrical properties of the resonator 20 will be described below with reference to FIGS FIGS. 3A and 3B explained. In Fig. 3A the distribution of the intensity of the electric field strength E at a first temperature T is shown. The cover 22 has, as in Fig. 2 a length P and a height ΔH. If the temperature is increased from T to T ', then the results in Fig. 3B indicated situation where the cover 22 has curved slightly upwards. The length P becomes the length P 'and the inclination angle β becomes β' with P <P ', ΔH <ΔH' and β <β '. As an approximation, P increases with the material expansion coefficient α2, while ΔH increases much more due to the leverage. In the Figure 3B It can be seen that the electric field strength in the region of the further outwardly curved cover 22 is reduced. In the example shown, a field-poor zone 24 is formed in the region of the lid tip, since the field distribution travels outward along the cover 22. This reduction of the electric field strength corresponds to a reduction of the capacitive load of the resonator 20, which in turn results in an increase of the resonance frequency f _R. In the in the FIGS. 3A and 3B As shown, the ratio P / R = 1.01 and the ratio in Fig. 3B P '/ R' = 1.02. Already such small geometric changes in the area of the cover are sufficient to reduce the influence of temperature on the resonance frequency, or even reverse if necessary (overcompensation).

In order to be able to exploit this effect of the local field strength reduction, the temperature expansion coefficient α 2 of the cover 22 must be greater than the thermal expansion coefficient α 1 of the pot 21. As a result, when increasing the temperature from T to T 'the radius R of the Pot 21 is larger and the dome-shaped cover 22 bulges further outwards. Increasing the radius R results in a decrease in the resonance frequency f _R, and the more curved cover results in an increase in the resonance frequency f _R.

It is formed according to the invention by the deformation of the cover with temperature increase in the various embodiments, an additional volume that helps that increases the total volume of the cavity. Contrary to the expectations of the average person skilled in the art, however, this increase in volume does not lead to a reduction in the resonance frequency since, as described, a geometric change occurs in the region of the cover and a field-poor zone is formed there.

The principle of the present invention will be described below with reference to FIGS FIGS. 4A-4D described with the figures and the following description is a highly simplified representation of the real facts. In this simplified illustration, it is assumed that a cavity resonator can be considered as a combination of a capacitance C and an inductance L, as can be seen from the following equation, where f _{R is} the resonant frequency: $$f_R=\frac{1}{2\mathit{\pi }\sqrt{L\cdot C}}\mathrm{,}$$

In Fig. 4A For example, a conventional cavity resonator 30 is shown with a pot 31 closed in all directions. This cavity resonator 30 has at the temperature T a volume V, a capacitance C and an inductance L. If the temperature is increased from T to T ', the result is the in Fig. 4B shown condition. If only the height H of the resonator pot 31 changed, the resonant frequency f _R would remain constant due to the properties of the TM010 mode, ie f _R = f ' _R , since in this case the capacitance, ie, C'<C and the inductance decreases increases, ie, L '> L. However, as the temperature increases, the radius R of the pot 31 also increases, which leads both to an increase in the inductance, ie, L '> L and to an increase in the capacitance, ie, C'> C. The volume V has increased by changing the height H and the radius R to V ', the capacitance C' has changed, ie C '≠ C, and the inductance has increased, ie L'> L, as already mentioned , Since the product of inductance and capacitance remains constant in the case of a change in height, but increases in the case of an increase in the radius R (L'C '> LC), there is an undesirable reduction in the resonant frequency f _R. Temperature compensation can not be achieved in this way.

In the Figures 4C and 4D now the behavior of a resonator 40 according to the invention is shown. The resonator 40 has a cover 42 with a tapered portion, which is shown in FIGS Images arched down. This cavity resonator 40 has at the temperature T a volume V ₁ , a capacitance C ₁ and an inductance L ₁ . The inductance L ₁ is approximately the same size as the inductance L in Fig. 4A because the addition of a domed cover does not cause any significant H field change and therefore no significant inductance change. However, the capacitance C ₁ is smaller than the capacitance C because the E-field is reduced by the pointed configuration of the cover 42.

If the temperature is increased from T to T ', the result is in Fig. 4D shown state, wherein the dimensional changes of the resonator 40 have been deliberately exaggerated. The volume V ₁ has increased to V ₁ ', the capacitance C ₁ ' has become smaller, ie C ₁ '<C ₁ , and the inductance has increased, ie L ₁ '> L ₁ . It is also true that L ₁ 'is approximately as large as L' in the resonator 30 (see Fig. 4B ). The fact that the capacity decreases and increases the inductance, the temperature dependence of the resonant frequency can be influenced as desired. Importantly, the temperature changes of L and C can be separately affected by the design of the resonator 30.

A cavity resonator according to the invention can be dimensioned as follows. In a first step, the choice of material can be made and a resonance frequency f _{R can be} specified. The pot may, for example, comprise CuW and the cover CuBe. Then the dimensions of the pot (H and R) and the dimensions of the cover (P and ΔH) are determined.
Now, with a commercially available simulation program that solves the eigenvalue problem for the Maxwell differential equations for the given geometry, the resonance frequency f _R can be calculated. In this case, the rotational symmetry of the geometric arrangement can be exploited, which makes it possible to obtain accurate simulation results in a short time. If the calculated value of the resonance frequency f _R does not agree with the specification, then the output variables (eg H, R and ΔH) can be modified in order to then repeat the calculation. In a following Step, the influence of a temperature change (increase or decrease of the temperature) on the shape of the pot and the cover can be determined. This is done by means of commercially available simulation programs for this mechanical problem or experimentally. In addition, the mechanical stresses in the pot and / or the cover can be calculated / simulated. If the mechanical stresses should be too high, the output quantities (eg H, round ΔH) can be modified again to repeat the calculation. Now the dependence of the resonance frequency f _R on the temperature can be calculated / simulated. In this calculation, specifications for the mechanical tolerances can be incorporated. If the dependence of the resonance frequency f _R on the temperature is within a predetermined range, the calculations may be terminated, otherwise the outputs (eg H, R and ΔH) may be modified again to then repeat the calculation.

With a suitable choice of the geometry and the materials of the pot and the cover of the various embodiments of the invention results in a reduction of the temperature dependence of the resonant frequency f _R or a complete compensation or even a reversal of the temperature dependence at least in a predetermined temperature range (eg working temperature ± 50K) ( overcompensation).

The invention is particularly suitable for use in circuits designed to process high power signals for broadband communication.

A resonator according to the invention may be part of a filter circuit which comprises an oscillator with the resonator in the feedback branch. By this type of arrangement only one frequency is transmitted.

The circuit according to the invention can be constructed on a ceramic substrate, for example a multilayer LTCC (Low Temperature Cofired Ceramics) substrate. Such a substrate can on a Base plate sit, which in turn carries the inventive resonator. Preferably, the ceramic substrate and base plate have a compatible (ie, only slightly different) coefficient of thermal expansion to form a stable composite.

Preferred is an embodiment of a circuit 50 in which the pot 51 of the resonator is formed in a base plate 53 of the circuit, as in FIG Fig. 5 shown. The base plate 53 is connected to a substrate 54 and may serve as a heat sink, for example as a heat sink for electronic components mounted on the opposite side of the substrate 54. In the substrate 54 and / or on the substrate 54 elements of the circuit 50 are integrated (these elements are not shown). The pot 51 is cylindrical in the example shown. In the region of the pot bottom, a conductive surface 57 is provided, which in Fig. 5 is indicated as a thick metallic layer. At the opposite end of the pot 51, a cover 52 is provided. This cover 52 comprises an outer annular region 52. 1, which extends substantially parallel to the conductive surface 57. In the area around the cylinder axis 58 around the cover 52.2 is curved conically downwards. In each case, a coupling hole 55 for coupling in an electromagnetic wave and a coupling hole 56 for coupling out the shaft are provided. Alternatively, this coupling and decoupling could also be done by one and the same coupling hole. Strip conductors are typically arranged on the substrate 54 in order to guide the shaft to the coupling point 55 and to pick it up and forward it on the other side 56. The strip conductors are in Fig. 5 not shown.

Preferably, in a circuit according to the invention, the first material is chosen such that the temperature expansion coefficient α1 of the base plate matches the temperature expansion coefficient a3 of the substrate.

Another circuit 60 according to the invention, is in Fig. 6 shown in the form of a block diagram. It is an oscillator circuit 60 with a resonator 80 according to the invention, which has a pot 61 and a cover 62. There are a Einkoppelstelle 66 and a decoupling point 65 in the bottom of the pot 61 is provided. The decoupled signal is coupled into a line leading to a Low Noise Amplifier 63 where the signal is amplified. In the embodiment shown, an optional attenuator 64 with two PIN diodes is provided which limits the power by "clipping". It may be a phase actuator 67 may be provided to adjust the phase position static. Also, the phase actuator 67 is optional. On the output side, a further amplifier 68 is provided to generate sufficiently large output signal power. This second amplifier 68 is usually reliant on a good dissipation of the heat loss, which by the present structure (with massive, good heat-conducting bottom plate 53, Fig. 5 ) can be guaranteed. On the output side of the amplifier 68 is the output (OUT) of the oscillator circuit. At this output the circuit 60 is taken power. A small part of the power is conducted via the coupling point 66 into the resonator 80. The resonator 80 is thus in the feedback path of the circuit 60.

In order to compensate for temperature shifts in the oscillation frequency of the oscillator circuit 60, which may be caused by components of the circuit 60, the temperature compensation of the resonator 80 may be designed so that the resonator 80 per se under- or overcompensation.

In the preferred embodiment shown in FIG Fig. 6 is shown, the circuit 60 includes an electrical component 64 to limit the power. Thus, a stable vibration state can be achieved. Power may be coupled out of circuit 60 at a suitable location (labeled OUT), which coupling may be capacitive, inductive, or direct. It is important that the overall gain in the circuit 60 is sufficient and the phase is correct, so that the oscillation starts and the circuit 60 vibrates stable.

Another embodiment of a cavity resonator 70 according to the invention is shown in FIG Fig. 7 shown. The resonator 70 has a cylindrical pot 71 and a cover 72, which are designed so that the inventive temperature compensation is used. The walls 71.1 of the pot 71, the base plate 74 (for example in the form of a single-sided metallized ceramic plate) and the cover 72 together enclose a cavity resonance volume. The pot 71 comprises a first (metallic or metallized) material having a first coefficient of thermal expansion α1, which is preferably in the range between 4 ppm / K and 10 ppm / K. The cover 72 comprises a second (metallic or metallised) material having a second coefficient of thermal expansion α2, which is preferably in the range between 10 ppm / K and 20 ppm / K. Thus, the second temperature expansion coefficient α2 is greater than the first coefficient of thermal expansion α1. When the temperature increases, the pot 71 expands, as indicated by the arrows 76 pointing outwards, and the cover 72 is deformed, as indicated by the arrows 75 and 77. Taken together, these expansions / deformations cause the cavity resonance volume to increase, with the resonant frequency remaining in a predetermined (tolerance) range.

In the following, further exemplary statements are made for the resonator 70. The radius R of the pot 71 is typically between 2.5 mm and 10 mm. In the illustrated embodiment, the radius is 4 mm. The height H is typically between 2 mm and 20 mm. In the illustrated embodiment, the total height is about 4 mm (total height = H + ΔH). The cover 72 may have a circumferential collar 72. 1 in order to be able to connect the cover 72 to the wall 71. 1 of the pot 71. For this purpose, the pot 71 may have a larger radius in the upper region than in the lower region. This results in a circumferential step 71.2 on the cover 72 can be placed. The cover 72 has in the illustrated embodiment, a thickening 72.2 in the center. In the area of the thickening 72.2 a continuous bore is provided which extends axially. Through this bore, a dielectric rod 73 can be inserted into the cavity of the resonator 70. With this rod 73, which is optional, the resonance frequency can be adjusted within certain limits, since the rod 73, depending on the position in the cavity changes the effective permittivity.

The resonator pot can be drilled, milled, rotated, cast, deep-drawn or otherwise manufactured according to the invention. Preferably, the inner walls of the pot are reworked to produce a surface with low surface roughness. Rolling, grinding, polishing, coating are particularly suitable as post-processing.

Particularly advantageous is an embodiment in which the walls of the pot have a low roughness and are preferably coated with gold and / or silver.

In a particularly advantageous embodiment, special measures ensure that the cover and the pot are conductively connected to one another. This electrical connection can be present on the entire circumference of the cover or on a substantial part of this circumference. Preferably, the cover is electrically and mechanically connected to the pot by a soldered or welded connection.

A further embodiment is characterized in that, instead of a pot with only one cover, a pot (made, for example, from a prismatic or round tube), which has covers on both sides, is used. In this case, both covers can contribute to the described principle of operation for compensation.

It is considered as an advantage of the invention that when using the TM ₀₁₀ mode, the height H of the pot can be chosen freely. It is not necessary here, as with waveguide resonators, to satisfy the condition that the height of the resonator corresponds to half the wavelength. The invention achieves an additional degree of freedom in determining the dimensions of the resonator. The (resonator) height H can be chosen so that a large quality factor Q results. According to the invention, for example, a figure of merit of 2500 can be achieved (at f _R ~ 30 GHz and gold metallization on the surface of pot and cover).

Preferably, the cover according to the invention is dome-shaped, domed or cone-shaped and forms - viewed from the direction of the pot - a cavity. But there are also other forms conceivable.

The present invention is considered to be a true alternative to the resonators initially referred to as clamped cavity resonators. The present invention is a true refinement of the re-entrant approach that is used in conjunction with the Figures 1A and 1B has been described. An advantage over the re-entrant resonators is the significantly higher quality. As an advantage over clamped cavity resonators as well as over re-entrant resonators, it is considered that more degrees of freedom are available in the choice of materials and shape and that easier assembly is possible. In addition, there is less sensitivity to manufacturing tolerances.

Depending on the embodiment of the invention, it is possible to realize a resonator which has a dependence of the resonance frequency on the temperature, which lies in the range between -10 ppm / K and +10 ppm / K. The dependence of the resonant frequency f _R can be determined in a given frame depending on the application and by appropriate design of the resonator, this framework can be complied with as specified.

The compensation effect achievable by the present invention is quantified by the choice of materials and geometry. Preferably, a material is used for the pot, which has an expansion coefficient α1 between 4 ppm / K and 10 ppm / K (for example, a copper-tungsten alloy, CuW, with α1 = 6.1 ppm / K). On the other hand, the cover comprises a material which preferably has an expansion coefficient α2 between 10 ppm / K and 20 ppm / K (for example, another copper alloy such as copper beryllium, CuBe, with α2 = 17.0 ppm / K). Particularly advantageous embodiments are those in which the second temperature expansion coefficient α2 is between 1.1 and 5 times greater than the first temperature expansion coefficient α1.

The resonators according to the invention have the advantage that their quality factor Q is not impaired by the temperature compensation measures, as is the case, for example, with the "re-entrant resonators".

The invention makes it possible to provide resonators having a high quality factor Q and low losses. Such resonators are particularly well suited for low-noise oscillator circuits. In filter circuits (composed of several resonators), high-quality resonators allow the realization of steep-angle, that is, particularly frequency-selective, filters and / or filters with particularly low insertion loss in the transmission frequency range.

It is a further advantage of the invention that the same operating principle can also be applied to other resonance _modes TE _m0m in a rectangular cavity or TM _0n0 (with m, n> 0 and integer) in a circular cavity. Many of these resonance modes lead to mechanically more complex (eg rectangular instead of circular) and more sensitive to tolerances structures. However, the advantage lies, as described, in the accessibility of higher grades (lower losses).

Claims (19)

1. Cavity resonator (20; 40; 80; 70) with temperature compensation, comprising a pot (21; 41; 51; 61; 71) with a floor (21.1; 54, 57; 74) and a cover (22; 42; 52.1, 52.2; 62; 72), with the pot (21; 41; 51; 61; 71) surrounding jointly with the floor (21.1; 54, 57; 74) and the cover (22; 42; 52.1, 52.2; 62; 72) a cavity resonance volume (V), and

   - the cavity resonator (20; 40; 80; 70) having a resonant frequency (f_R) in operation,

   - the pot (21; 41; 51; 61; 71) comprising a first material which has a first temperature expansion coefficient (α1),

   - the cover (22; 42; 52.1, 52.2; 62; 72) comprising a second material having a second temperature expansion coefficient (α2),

   and with the second temperature expansion coefficient (α2) being greater than the first temperature expansion coefficient (α1), and in case of an increase in temperature there being an expansion of the pot (21; 41; 51; 61; 71) and a deformation of the cover (22; 42; 52.1, 52.2; 62; 72) which jointly causes an enlargement of the cavity resonance volume (V), characterized in that the cover is bulged outwardly in such a way that it forms a cavity when viewed from the direction of the pot, and the cover (22; 42; 52.1, 52.2; 62; 72) bulges as a result of the deformation of the cover (22; 42; 52.1, 52.2; 62; 72), thus resulting in an increase in the resonant frequency (f_R), and the diameter of the pot (21; 41; 51; 61; 71) increases by the expansion of the pot (21; 41; 51; 61; 71), thus resulting in a reduction of the resonant frequency (f_R), with the increase of the resonant frequency (f_R) and the reduction of the resonant frequency (f_R) substantially compensate each other in order to ensure in a temperature range that the resonant frequency (f_R) remains substantially stable.
2. Cavity resonator (20; 40; 80; 70) according to claim 1, characterized in that the cavity resonator (20; 40; 80; 70) has a resonant frequency (f_R) in operation and the increase in the cavity resonance volume (V) during a temperature increase occurs in such a way that the resonant frequency (f_R) remains stable within a predetermined margin, or that the resonant frequency (f_R) has a predetermined temperature coefficient which is unequal to zero.
3. Cavity resonator (20; 40; 80; 70) according to claim 2, characterized in that the resonant frequency (f_R) of at least one resonance mode remains stable.
4. Cavity resonator (20; 40; 80; 70) according to claim 1 or 2, characterized in that a local reduction of an electric field strength ( E ) is obtained in the cavity resonance volume by the deformation of the cover (22; 42; 52.1, 52.2; 62; 72).
5. Cavity resonator (20; 40; 80; 70) according to claim 1 or 2, characterized in that a reduction of a capacitive load of the cavity resonator (20; 40; 80; 70) is obtained by the deformation of the cover (22; 42; 52.1, 52.2; 62; 72).
6. Cavity resonator (20; 40; 80; 70) according to claim 1 or 2, characterized in that a cavity resonator (20; 40; 80; 70) is concerned which operates in TM_0N0 resonance mode, with n>0 and integral numbers applying.
7. Cavity resonator (20; 40; 80; 70) according to one of the claims 1 to 5, characterized in that the cover (22; 42; 52.1, 52.2; 62; 72) is shaped in a cupola-like or conical manner and forms a cavity when seen from the direction of the pot (21; 41; 51; 61; 71).
8. Cavity resonator (20; 40; 80; 70) according to claim 1, 2 or 3, characterized in that a cavity resonator (20; 40; 80; 70) is concerned which is suitable for integration in a metallic baseplate of a ceramic substrate (54; 74), preferably the base plate of an LTCC multi-layer ceramics.
9. Cavity resonator (20; 40; 80; 70) according to claim 8, characterized in that the first material is chosen in such a way that the first temperature expansion coefficient (α1) of the baseplate matches the temperature expansion coefficient (α3) of the substrate (54; 74).
10. Cavity resonator (20; 40; 80; 70) according to claim 1, 2 or 3, characterized in that the cavity resonator (20; 40; 80; 70) has a quality factor (Q) which is determined substantially by the resonator height (H) of the pot (21; 41; 51; 61; 71).
11. Cavity resonator (20; 40; 80; 70) according to claim 1, 2 or 3, characterized in that the pot (21; 41; 51; 61; 71) has a copper alloy, preferably a copper and tungsten alloy (CuW), and the cover (22; 42; 52.1, 52.2; 62; 72) has another copper alloy, preferably a copper and beryllium one (CuBe).
12. Cavity resonator (20; 40; 80; 70) according to claim 1, 2 or 3, characterized in that the second temperature expansion coefficient (α2) is larger than the first temperature expansion coefficient (α1) by between 1.1 and 5 times.
13. Cavity resonator (20; 40; 80; 70) according to claim 1, 2 or 3, characterized in that the pot (21; 41; 51; 61; 71) has a low roughness on the inside and is preferably coated with gold and/or silver.
14. Cavity resonator (20; 40; 80; 70) according to claim 1, 2 or 3, characterized in that means (73) for influencing the resonant frequency are provided which preferably partially protrude into the cavity resonance volume and change the effective permittivity there.
15. Cavity resonator (20; 40; 80; 70) according to claim 1, 2 or 3, characterized in that means (55, 56; 65, 66) are provided for injecting and extracting an electromagnetic wave, with preferably a coupling hole for injecting and extracting being provided.
16. Use of a cavity resonator (20; 40; 80; 70) according to one of the claims 1 to 15 in a microwave system (50; 60), with the cavity resonator (20; 40; 80; 70) being part of an oscillator circuit.
17. Oscillator circuit (50; 60), characterized in that a cavity resonator (20; 40; 80; 70) according to one of the claims 1 to 15 is part of the oscillator circuit (50; 60).
18. Oscillator circuit (50; 60) according to claim 17, characterized in that the oscillator circuit (50; 60) is integrated in or on a ceramic substrate (54; 74), preferably an LTCC multi-layer ceramics.
19. Oscillator circuit (50; 60) according to claim 18, characterized in that a part of the oscillator circuit (50; 60) is arranged on one side of the ceramic substrate (54; 74) and the cavity resonator (20; 40; 80; 70) is arranged on another side of the ceramic substrate (54; 74).

Images