RU2492539C2 - Miniature device for mangetisation and thermal stabilisation of ferrite microwave resonators - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: dynamic frequency stability increases owing to design features of a magnetic system which includes heat-insulating elements which damp environmental thermal shocks. Frequency stability of the resonator is ensured by selecting thickness of two different magnets which are connected in a magnetic circuit in series to form a heat-insulating gap with an adjustment screw mounted in a hole in a magnetic shield. The adjustment screw is used only for tuning the resonator to a given thermal stabilisation frequency. Further frequency tuning is carried out using an electric control coil mounted in the lateral gap of permanent magnets. Temperature stability of the resonator frequency is maintained in the entire range of electrical adjustment. The design of the device enables accommodation in the working gap of a ferrite resonator together with the wafer of the microstrip integrated circuit of the electric device. The magnetic shield further operates as the housing of the electric device.

EFFECT: high dynamic stability of the resonator frequency during sharp changes in ambient temperature and miniaturisation of the functional microwave device.

3 cl, 5 dwg

Description

The invention relates to radio engineering and can be used in integrated microwave devices containing film ferrite resonators.

A magnetization device is known, consisting of two parallel steel plates and two identical permanent rectangular magnets located between two steel plates and connected by the same poles to one plate and opposite poles to another plate. The field strength in the working gap formed by the plates between the magnets is regulated using steel shunts located on the outer side surface of the permanent magnets (USSR Author's Certificate No. 951208, IPC G01R 33/05).

However, this device does not have protection against external magnetic fields and is strongly shunted by surrounding steel objects.

Also known is a shielded magnetic system with mechanical and electrical field adjustment, consisting of a cylindrical steel screen, inside of which there is a steel disk and a pair of ring magnets connected by the same poles to a steel plate, and opposite poles to the inner flat surfaces of the steel screen. Between the side surfaces of the steel disk and the screen, a gap is made, which is filled with turns of an electric control coil. Mechanical adjustment of the field in the working gap formed by the flat surfaces of the steel disk and the screen is carried out by an adjusting screw mounted symmetrically on the opposite surface of the screen (USSR Author's Certificate No. 1781744, IPC Н01К 33/05).

However, this device does not provide temperature stability of the frequency of the ferrite resonator installed in the working gap of the magnetic system.

Closest to the proposed invention is a magnetization and thermal stabilization of a ferrite resonator equipped with a pair of dissimilar ring magnets with different temperature demagnetization coefficients that satisfy the condition

$${\alpha }_{M\mathrm{one}}<\frac{\mathrm{four}\mathrm{<figure-callout\; id="0"\; label="\pi \; M"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">\pi \; </figure-callout>}{M}_{}{}_0}{{\mu }_0{\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">H</figure-callout>}}_0}{\alpha }_F<{\mathrm{<figure-callout\; id="2"\; label="\alpha \; M"\; filenames="00000015.png"\; state="\{\{state\}\}">\alpha \; </figure-callout>}}_M\text{,}\left(\text{one}\right)$$

where α _F is the temperature coefficient of demagnetization of ferrite;

α _M1 - temperature coefficient of demagnetization of the first magnet;

α _M2 is the temperature coefficient of demagnetization of the second magnet;

4πM ₀ is the saturation magnetization of ferrite;

H ₀ - the required magnetic field strength in the working gap;

µ ₀ is the magnetic constant,

and the ratio of the pole areas of the ring magnets S _M0 and S _M1 satisfies the condition:

$$\frac{S_{M0}}{S_{M\mathrm{one}}}=\frac{B_{M\mathrm{one}}}{{\mathrm{<figure-callout\; id="0"\; label="B\; M"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">B\; </figure-callout>}}_M}\cdot \frac{\mathrm{four}\mathrm{<figure-callout\; id="0"\; label="\pi \; M"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">\pi \; </figure-callout>}{M}_{}{}_0{\alpha }_F-{\mathrm{<figure-callout\; id="0"\; label="\alpha \; M"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">\alpha \; </figure-callout>}}_M{\mu }_0{\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">H</figure-callout>}}_0}{{\mu }_0{\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">H</figure-callout>}}_0{\alpha }_{M\mathrm{one}}-\mathrm{four}\mathrm{<figure-callout\; id="0"\; label="\pi \; M"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">\pi \; </figure-callout>}{M}_{}{}_0{\alpha }_F}\left(\text{2}\right)$$

where B _M0 and B _M1 are the residual induction of permanent magnets. The magnetization device comprises a closed cylindrical steel screen, a steel disk mounted axisymmetrically inside the screen, two dissimilar magnets, a steel adjusting screw, an electric control coil, configured to connect to a power source, installed in the side gap of the steel disk and the screen, a ferrite resonator made with the ability to connect to an external microwave path, located axisymmetrically between the steel disk and the flat surface of the steel screen (see patent for retention RU No. 2356120, C2, IPC H01F 13/00).

The disadvantage of this device is the thermodynamic instability of the frequency of the ferrite resonator, which occurs due to the uneven heating (cooling) of the permanent magnets and the resonator during sudden changes in ambient temperature.

The technical result of the invention is to increase the thermodynamic stability of the frequency of the ferrite resonator, as well as to reduce the size of the integrated device, the element of which is a ferrite resonator.

The specified technical result is achieved by the fact that a miniature magnetization and thermal stabilization frequency of a ferrite microwave resonator, comprising: a closed cylindrical steel screen, a steel disk mounted axisymmetric inside the screen; two dissimilar magnets, a steel adjusting screw, an electric control coil made with the ability to connect to a power source, installed in the lateral gap of the steel disk and the screen; a ferrite resonator configured to connect to an external microwave path, located axisymmetrically between the steel disk and the flat surface of the steel screen, according to the decision, the steel adjustment screw is mounted in a threaded hole made axisymmetrically in the flat surface of the steel screen opposite the ferrite resonator, the device contains a second steel adjustment screw mounted in an axisymmetric threaded hole on the opposite surface of the steel screen; the device comprises a microstrip integrated circuit connected to a ferrite resonator, configured to be connected to a power source, the first and second permanent magnets are made in the form of axial magnetized disks; magnets are connected by opposite poles and connected by one of the external poles to the back of the steel disk; the opposite outer pole forms a gap with the first adjusting screw; the electric control coil is provided with a frame of heat insulating material. The diameters of the first and second permanent magnets, the steel disk, the first and second adjusting screws are equal to each other, and the ratio of the thicknesses of the permanent magnets l _M1 , l _M2 are selected from the condition

$$\frac{l_{M\mathrm{one}}}{{\mathrm{<figure-callout\; id="2"\; label="l\; M"\; filenames="00000015.png"\; state="\{\{state\}\}">l\; </figure-callout>}}_M}=\frac{B_{r2}}{B_{r\mathrm{one}}}\cdot \frac{\mathrm{four}\pi \gamma M_0\left({\alpha }_F/{\alpha }_{M2}-\mathrm{one}\right)-f_{st}}{f_{st}-\mathrm{four}\pi \gamma M_0\left({\alpha }_F/{\alpha }_{M\mathrm{one}}-\mathrm{one}\right)}\left(\text{3}\right)$$

where α _F is the temperature coefficient of demagnetization of ferrite; M _{0 is} the saturation magnetization of ferrite; α _M1 , α _M2 - temperature coefficients of demagnetization of the first and second permanent magnets; B _r1 , B _r2 - residual induction of the first and second permanent magnets; γ is the gyromagnetic ratio; f _st - a given frequency of temperature stabilization. The microstrip integrated circuit is made on a disk dielectric substrate, the diameter of which is made equal to the inner diameter of the steel screen; a hole is made in the center of the substrate, inside which a ferrite resonator is mounted.

The design of the device is presented in figure 1. The miniature magnetization and thermal stabilization device for the frequency of a ferrite microwave resonator contains a closed cylindrical steel screen 1. Two dissimilar permanent magnets 2 and 3 and a steel disk 4 are mounted axisymmetrically. The magnets are made in the form of disks with diameters equal to the diameter of the steel disk and have axial magnetization ; the magnets are connected by opposite poles and connected by one of the external poles to one flat side of the steel disk. The device contains two tabletop adjusting screws 5 and 6, mounted in axisymmetric threaded holes made on opposite flat surfaces of the steel screen. In the gap between the adjusting screw 6 and the flat side of the steel disk 4, facing away from the magnets, there is a ferrite microwave resonator 7 mounted on a dielectric substrate of a microstrip integrated circuit 8 configured to connect to an external microwave path through a coaxial microwave output 9 and to a power source by conclusions 10. In the lateral gap between the steel disk and the inner surface of the screen is an electric control coil 12, equipped with a dielectric frame 11 and complements to be connected to the power source via pin 13.

The device operates as follows. Serially connected first 2 and second 3 disk magnets create a magnetic flux, which enters the steel disk 4 and through the air gap enters the second adjusting screw by breaking the steel screen 1. Then through the first adjusting screw 5 and the air gap closes at the opposite pole of the first magnet 2. The mechanical adjustment of the field in the working gap is carried out by screwing in / out the adjusting screws 5 and 6. This adjustment is used only for initial tuning of the resonator to a given frequency of the temperature -temperature stabilization. After completing the setting, the position of the screws is fixed firmly. In the future, only electric field adjustment is used, which is carried out by changing the magnitude and direction of the current in the winding of the electric control coil 12. The power supply of the control coil is supplied through insulated inputs 13 passing through the holes in the screen. Coaxial input 9 are used to connect the microstrip integrated circuit 8 to an external microwave path. The insulated input 10 is used to supply power to the active elements of the microstrip integrated circuit.

The overall dimensions of the integrated device containing the ferrite resonator are significantly reduced due to the use of the steel screen of the magnetizing device of the resonator as the housing of the microstrip integrated circuit. The design features of the invention further reduce the dimensions of the magnetizing device by reducing the diameters of disk magnets, steel disk and adjusting screws to sizes comparable to the dimensions of a ferrite resonator, as well as by reducing the thicknesses of the constants of magnesium "when reducing the thickness of the working gap in the case of a ferrite resonator in the hole substrates of a microstrip integrated circuit.

The built-in thermal stabilization system does not increase the dimensions of the magnetization device of a ferrite resonator. In this design, it is implemented on the principle of compensating the temperature drift of the resonator frequency with an adequate change in the field in the working gap. In the case of normal magnetization, as shown in Fig. 1, the condition for the temperature stability of the resonator frequency f (T) ≈γ [H ₀ (T) -4πM ₀ (T)] is reduced to

$$\frac{\partial H_0\left(T\right)}{\partial T}-\mathrm{four}\pi \frac{\partial M_0\left(T\right)}{\partial T}=0\left(\text{four}\right)$$

where H ₀ (T) is the field strength in the working gap, M ₀ (T) is the saturation magnetization of ferrite, γ = 2.83 MHz / E is the gyromagnetic ratio. The field strength H ₀ (T) is calculated according to the Kirchhoff rules for the magnetic circuit shown in Fig. 2, where Φ _M1 (T) = B _r1 (T) S _M1 and Φ _M2 (T) = B _r2 (T) S _M2 - magnetic flux generated by the first and second magnets, B _r1 (T), B _r2 (T) - residual induction of permanent magnets, S _M1 , S _M2 - the area of the poles of the magnets, R _M1 = l _M1 / µ ₀ S _M1 , R _M2 = l _M2 / µ ₀ S _M2 are the internal resistances of the magnets, l _M1 , l _M2 are the thicknesses of the magnets, µ ₀ is the magnetic permeability of the vacuum, E _M = Iw is the magnetomotive force of the coil with current, I is the current strength, w is the number of turns of the coil, R ₀ = l ₀ / μ ₀ S _0, R ₁ = l ₁ / μ ₀ S _1, R ₂ = l ₂ / μ ₀ S ₂ - magnetic resisting I, respectively, working, adjustment and lateral clearances, l _0, S _0; l ₁ , S ₁ ; l ₂ , S ₂ - respectively, the thickness and area of the working, adjusting and lateral gaps. Taking into account the requirement S ₀ = S ₁ = S _M1 = S _M2 = S, the field strength in the working gap is obtained in the form

$$H_0\left(T\right)=\frac{B_{r\mathrm{one}}\left(T\right)l_{M\mathrm{one}}+B_{r2}\left(T\right){\mathrm{<figure-callout\; id="2"\; label="l\; M"\; filenames="00000015.png"\; state="\{\{state\}\}">l\; </figure-callout>}}_M\pm Iw{\mu }_{0}S}{{\mu }_0\left\{{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">l</figure-callout>}}_0+l_{\mathrm{one}}+\left(l_{M\mathrm{one}}+l_{M2}\right)\left[\mathrm{one}+\frac{\left({\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="00000015.png,00000016.png"\; state="\{\{state\}\}">l</figure-callout>}}_0+l_{\mathrm{one}}\right)}{l_2}\frac{S_2}{S}\right]\right\}},\left(\text{5}\right)$$

where the sign (±) is determined by the direction of current flow in the control coil. Taking into account (5), the condition of thermal stabilization (4) is rewritten in the form

$$\frac{{\alpha }_{M\mathrm{one}}{B}_{r\mathrm{one}}\left(T\right)l_{M\mathrm{one}}+{\alpha }_{M2}{B}_{r2}\left(T\right)l_{M2}}{B_{r\mathrm{one}}\left(T\right)l_{M\mathrm{one}}+B_{r2}\left(T\right){\mathrm{<figure-callout\; id="2"\; label="l\; M"\; filenames="00000015.png"\; state="\{\{state\}\}">l\; </figure-callout>}}_M}=\mathrm{four}\pi \frac{{\alpha }_F{M}_0\left(T\right)}{H_{0M}\left(T\right)},\left(\text{6}\right)$$

, $${\alpha }_{M2}=\frac{1}{B_{r2}\left(T\right)}\frac{\partial B_{r2}\left(T\right)}{\partial T}$$

- температурные коэффициенты остаточной индукции первого и второго магнитов, $${\alpha }_F=\frac{1}{B_{r1}\left(T\right)}\frac{\partial M_0\left(T\right)}{\partial \left(T\right)}$$

- температурный коэффициент намагниченности феррита. Из условия (6) нетрудно получить соотношение толщин постоянных магнитовwhere H _0M (T) is the field strength in the working gap in the absence of current in the control coil, $${\alpha }_{M\mathrm{one}}=\frac{\mathrm{one}}{B_{r\mathrm{one}}\left(T\right)}\frac{\partial B_{r\mathrm{one}}\left(T\right)}{\partial \left(T\right)}$$

, $${\mathrm{<figure-callout\; id="2"\; label="\alpha \; M"\; filenames="00000015.png"\; state="\{\{state\}\}">\alpha \; </figure-callout>}}_M=\frac{\mathrm{one}}{B_{r2}\left(T\right)}\frac{\partial B_{r2}\left(T\right)}{\partial T}$$

- temperature coefficients of the residual induction of the first and second magnets, $${\alpha }_F=\frac{\mathrm{one}}{B_{r\mathrm{one}}\left(T\right)}\frac{\partial M_0\left(T\right)}{\partial \left(T\right)}$$

- temperature coefficient of magnetization of ferrite. From condition (6) it is easy to obtain the ratio of the thicknesses of permanent magnets

$$\frac{l_{M\mathrm{one}}}{{\mathrm{<figure-callout\; id="2"\; label="l\; M"\; filenames="00000015.png"\; state="\{\{state\}\}">l\; </figure-callout>}}_M}=\frac{B_{r2}}{B_{r\mathrm{one}}}\cdot \frac{\mathrm{four}\pi \gamma M_0\left({\alpha }_F/{\alpha }_{M2}-\mathrm{one}\right)-f_{st}}{f_{st}-\mathrm{four}\pi \gamma M_0\left({\alpha }_F/{\alpha }_{M\mathrm{one}}-\mathrm{one}\right)},\left(\text{7}\right)$$

at which the resonator frequency f _{st is} stabilized over the entire range of operating temperatures, within which the temperature demagnetization of ferrite and permanent magnets is linear and reversible, and the stabilization frequency satisfies the condition

$$f_{st\mathrm{one}}\le f_{st}\le {\mathrm{<figure-callout\; id="2"\; label="f\; s\; t"\; filenames="00000015.png"\; state="\{\{state\}\}">f\; </figure-callout>}}_{st},\left(\text{8}\right)$$

where f _st1 = 4πγM ₀ (α _F / α _M1 -1), f _st2 = 4πγM ₀ (α _F / α _M2 -1) are the boundary frequencies of the stabilization range corresponding to the zero thickness of one of the magnets. It is essential that the current flowing in the control coil is not included in expression (6). This means that the temperature stabilization of the resonator frequency is maintained over the entire range of electrical tuning. However, this does not exclude frequency shifts when temperature gradients of the permanent magnets and the resonator occur.

In this invention, the causes of temperature gradients are eliminated by the design features of the device. The dielectric substrate of the microstrip circuit, the frame of the electric control coil 11 and the air gaps formed by the first 5 and second 6 adjusting screws additionally perform the functions of heat insulators damping thermal shock of the environment. Thermal insulation causes a slower and, accordingly, more uniform heating (cooling) of permanent magnets and a resonator, eliminating the possibility of temperature gradients.

It should be noted that calculations of the temperature stabilization frequencies f _st according to the Kirchhoff rules for magnetic circuits give only an approximate result, since they do not take into account the scattering fields, and magnets are considered in the approximation of the rectangularity of the hysteresis loop. In a real device, the stabilization frequency may differ from the calculated one, but this does not interfere with the implementation of the invention.

The following is an example implementation of the invention. For clarity, a mathematical model of a real device was considered, as in Fig. 2, with neodymium-iron-boron (Nd-Fe-B) and samarium-cobalt (Sm-Co) magnets connected in series for magnetizing and thermal stabilization of the film YIG resonator in the range temperatures (-40, +60) ºС. The field topology was modeled by the finite element method implemented in the Ansoft Maxwell SV software package. The initial calculation data were the specified thicknesses: Nd-Fe-B magnet l _M1 = 2 mm; Sm-Co magnet l _M2 = 1 mm; steel disk d ₀ = 0.5 mm, working clearance l ₀ = 1 mm and adjusting clearance l ₁ = 0; 0.5; one; 1.5; 2 mm. The radii of the Nd-Fe-B and Sm-Co magnets, the steel disk, and the adjusting screws were chosen equal to r ₀ = 2.5 mm. The inner radius of the steel screen was r ₁ = 7 mm, and the outer radius was r ₂ = 8 mm. The thickness of the end walls of the magnetic screen was d ₁ = 1.5 mm. The dimensions of the device were ⌀16 × 10 mm. For the calculations, reference data were used: for YIG - α _F = 0.23% / ºС, 4πM ₀ = 1.75 KG; for Nd-Fe-B - α _M1 = 0.12% / ºС, B _r1 = 11.2 KG; for Sm-Co - α _M2 = 0.05% / ºС, B _r2 = 7.5 kgf.

Below are the results of numerical calculations. The graph of figure 3 shows the radial dependence of the field strength in the working gap H ₀ (r), calculated in the plane of the film resonator with a thickness of the adjustment gap l ₁ = 0.5 mm. The dotted line on the graph indicates the radius of the pole pieces r ₀ = 2.5 mm. It is seen that the field is uniform in the radius of the YIG film r _F ~ 1.5 mm, which is necessary for the effective excitation of the YIG resonator, and its intensity is H ₀ = 3754 Oe, which corresponds to excitation of the resonator at a frequency f (T ₀ ) = 5674 MHz . Figure 3 shows that the field lines do not extend beyond the steel casing, which indicates a good shielding of the magnetic system.

Figure 4 presents the calculation of the temperature dependence of the excitation frequencies of the YIG resonator f (T), with two thicknesses of the adjustment gap l ₁ = 0 and l ₁ = 0.5 mm. It is seen that the dependence f (T) has a strictly linear character, and the resonator excitation frequency and the slope of the temperature characteristic of the frequency ∆f / ∆T substantially depend on the position of the adjusting screw. Calculation of ∆f / ∆T values for a number of thicknesses of the adjustment gap l ₁ = 0; 0.5; one; 1.5; 2 mm is shown in FIG. Here, on the abscissa axis, the frequencies of the YIG resonator excitation at room temperature T ₀ = 20 ° C are marked.

The stabilization frequency f _st corresponding to the condition Δf / ΔT = 0 is located in the frequency range 5673.98 ... 6621.95 MHz, at which the function Δf / ΔT changes sign (in figure 5, the frequency f _{st is} marked by an arrow). Using the rule of similarity of right-angled triangles, the required thickness of the adjusting gap l ₁ = 0.3 8 mm and the stabilization frequency of the YIG resonator f _st = 5892.46 MHz are calculated. The required clearance is set by rotating the first adjusting screw.

In practice, the thermal stabilization system settings parameter is the frequency of the YIG resonator, measured in a given temperature range. In this case, the procedure for determining the stabilization frequency f _st and tuning the resonator to this frequency exactly repeats the steps described above. At the end of the adjustment, the position of both adjusting screws is firmly fixed. In the future, the tuning of the resonant frequency is carried out by electrical adjustment.

Claims (3)

1. A miniature device for magnetizing and thermally stabilizing the frequency of a ferrite microwave resonator, comprising a closed cylindrical steel screen, a steel disk mounted axisymmetrically inside the screen; two dissimilar magnets, a steel adjusting screw, an electric control coil made with the ability to connect to a power source, installed in the side gap of the steel disk and the screen, a ferrite resonator made with the ability to connect to the external microwave path, located axisymmetrically between the steel disk and the flat surface of the steel screen, characterized in that the steel adjusting screw is installed in a threaded hole made axisymmetrically in the flat surface of the steel screen n against a ferrite resonator, the device contains a second steel adjusting screw mounted in an axisymmetric threaded hole on the opposite surface of the steel screen, the device contains a microstrip integrated circuit connected to a ferrite resonator, configured to connect to a power source, the first and second permanent magnets are made in the form of disks with axial magnetization, the magnets are connected by opposite poles and connected by one of the external poles to the back the opposite side of the steel disk forms a gap with the first adjusting screw, the electric control coil is equipped with a frame made of heat-insulating material. 2. The device according to claim 1, characterized in that the diameters of the first and second permanent magnets, steel disk, first and second adjusting screws are made equal to each other, and the ratio of the thicknesses of the permanent magnets l _M1 , l _{M2 is} selected from the condition
$$\frac{l_{M\mathrm{one}}}{l_{M2}}=\frac{B_{r2}}{B_{r\mathrm{one}}}\cdot \frac{\mathrm{four}\pi \gamma M_0\left({\alpha }_F/{\alpha }_{M2}-\mathrm{one}\right)-f_{st}}{f_{st}-\mathrm{four}\pi \gamma M_0\left({\alpha }_F/{\alpha }_{M\mathrm{one}}-\mathrm{one}\right)}\text{,}$$

where α _F is the temperature coefficient of demagnetization of ferrite; M ₀ is the saturation magnetization of ferrite; α _M1 , α _M2 - temperature coefficients of demagnetization of the first and second permanent magnets; In _r1 , In _r2 - residual induction of the first and second permanent magnets; γ is the gyromagnetic ratio; f _st - a given frequency of temperature stabilization. 3. The device according to claim 1, characterized in that the electrical circuit is made on a disk dielectric substrate, the diameter of which is made equal to the inner diameter of the steel screen; a hole is made in the center of the substrate, inside which a ferrite resonator is mounted.

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