RU2356120C2 - Device for magnetisation and thermal stabilisation of microwave ferrite devices - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is attributed to electric engineering and can be used in integral microwave devices containing ferrite elements. The device uses combinations of standard-type magnets with increased and decreased value of thermal demagnetisation coefficient. Thermal compensation condition is achieved when there is certain ratio of pole sizes between constant magnets of two types. Device frequency setting is provided by adjusting screw installed in the pole of magnet system. To improve vibration resistance of adjustment, adjusting screw is fixed by polymer material. Electric frequency resetting is performed using coil with current installed inside magnet screen. To provide additional miniaturisation, device design version is suggested which enables integral microwave circuit positioning inside magnet screen.

EFFECT: providing thermal stabilisation of frequency characteristics of microwave ferrite devices and increasing their vibration resistance due to compensation of ferrite thermal demagnetisation by thermal demagnetisation of constant magnets.

2 cl, 2 dwg

Description

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

A magnetization device is known, consisting of two parallel steel plates and two identical permanent rectangular magnets located between the plates and connected by the same poles to one and opposite poles to the other plates. The magnitude of the magnetic field in the working gap formed by the plates in the gap between the magnets is regulated by steel shunts located on the outer side surface of the permanent magnets (copyright certificate No. 951208, USSR, class G01R 33/05, 1982).

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

A magnetic system is also known in which additional permanent magnets, a third steel plate and a shield are inserted, with additional magnets mounted by second poles of the same name on the opposite surface of the second steel plate, their first poles of the same name connected by a third plate, the first and third steel plates connected to the screen, a gap is made between the second steel plate and the screen. To adjust the field in the working gap, an adjustment screw is installed in the third plate opposite the working gap, and control coil turns are placed between the screen and magnets (copyright certificate No. 1781744, USSR, class. H01R 33/05, 1992).

However, this magnetic system does not provide temperature stability to the characteristics of magnetized ferrite devices.

Closest to the proposed invention is a shielded magnetic system with mechanical and electrical adjustment of the field strength in the working gap, which additionally contains built-in temperature compensation and thermostating magnetized ferrite devices. The design of the magnetic system is made in the form of a hinged element of microstrip circuits. The thermal compensation system has two mechanical adjustments, which allow setting the set values of the device output parameters and adjusting the technological variation in the temperature characteristics of magnetic materials. Thermal compensation of the device parameters is achieved by introducing thermomagnetic resistance made of thermomagnetic alloy into the closed magnetic circuit and additional adjustment of the working gap length of the magnetic system. Thermostating of the device is ensured by introducing an adjustable thermocouple and thermal insulation of the magnetic system (copyright certificate No. 5065565, RF, class N01P 11/00, 1996).

The disadvantages of this device are the narrow temperature range of thermal compensation, which necessitates additional temperature control and thermal insulation of the device, as well as the high complexity of setting up the thermal compensation system and its low vibration resistance.

1. The aim of the invention is to increase the thermal stability and vibration resistance of magnetizable ferrite devices.

This goal is achieved by the fact that in a known magnetic system consisting of a closed steel screen of rectangular (or cylindrical) shape; a steel plate (or disk) located inside the screen parallel to its internal flat surfaces with a gap between its side surface and the inner surface of the screen; two pairs of identical rectangular (or two identical ring) magnets located on both sides of the plate (disk), connected by the same poles to the plate (disk), and opposite poles to opposite internal flat surfaces of the screen; an adjusting steel screw installed in the threaded hole of the screen opposite one of the surfaces of the plate (disk); a rectangular (cylindrical) electric coil of a non-magnetic conductor located in the gap between the side surface of the plate (disk) and the inner side surface of the screen; coaxial microwave signal inputs connected to a ferrite device and coil power inputs installed in the openings of the screen base are amended: the adjusting screw is installed in the threaded hole of the steel plate (disk); the threaded hole of the steel screen is replaced by a technological hole, additionally introduced: a second steel plate (disk) adjacent to the first plate on the opposite side of the technological hole; a second steel screen covering the process opening; polymeric material filling the space between the adjusting screw and the technological hole, as well as additional requirements are imposed on the properties of permanent magnets and their sizes, namely: temperature coefficients of the residual induction of permanent magnets α _M0 , α _M1 located on one and the other side of the plate (disk ) must satisfy the condition

Where

4πM ₀ is the saturation magnetization of ferrite;

α _F is the temperature coefficient of demagnetization 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 S _M0 and S _M1 selected, according to condition (1), of the permanent magnets must satisfy the condition

where B _M0 and B _M1 are the residual inductions of the selected magnets.

2. In order to miniaturize the device according to claim 1, changes were made: permanent magnets from the working gap are installed in the gap between the side surfaces of the steel plates and the side surface of the steel screen; Coaxial inputs of the microwave signal and coil power are installed in the holes of the side surface of the screen.

The design of the device according to claim 1 is presented in figure 1. The design of the device according to claim 2 is presented in figure 2.

The device consists of a closed steel shield 1, a steel plate (disk) 2, permanent magnets 3 and 4 (arrows indicate the directions of magnetization), which differ in thermomagnetic properties and pole sizes and satisfy the conditions (1) and (2), the adjusting screw 5, additional steel the pole 6, the technological hole 7, the polymer material 8, the additional steel screen 9, the ferrite device 10, the electric coil 11, the coaxial microwave inputs 12, the power inputs of the coil 13, the dielectric micro loskovoy circuit 14, a coaxial-stripline transitions 15, the housing 16 of the microstrip circuit.

The device according to claim 1 works as follows. Permanent magnets 3 and 4 create magnetic fluxes, which, when summed up, enter the steel plate (disk) 2, then into the adjusting screw 5 and the additional pole 6. Next, the magnetic flux is divided into three outgoing flows: 1) through the working gap formed by the additional pole 6 and screen; 2) through the adjustment gap formed by the end face of the adjustment screw and the screen; and 3) through the lateral gap formed by the side surface of the plate (disk) and the screen. The field value in the working gap is adjusted due to the redistribution of magnetic fluxes that occurs when the screw 5 is screwed in / out. Access to the screw is provided by the technological hole 7. After completing the adjustment to the set field value in the working gap, the screw position is firmly fixed using polymerizable material 8 ( for example, sealant, epoxy resin, etc.), which is poured into the cavity between the screw 5 and the screen 1 through the technological hole 6, and the hole itself is closed with an additional with a real screen 9. Fixing the screw with a polymer material eliminates the backlash of the threaded connection, which increases the vibration resistance of the mechanical adjustment of the system and further increases the strength of the entire structure. The electric adjustment of the field in the working gap is carried out by changing the magnitude and direction of the current in the electric coil 11 installed in the gap between the side surface of the plate (disk) 2 and the screen 1. The power supply of the coil is carried out by means of insulated inputs 13 passing through the holes in the base of the screen. Coaxial inputs 12 are used to connect a ferrite microwave device. Structurally, the device is made in the form of a hinged element of the integrated microwave circuit, which is installed on the back (grounded) side of the microstrip line (MPL) substrate 14 and connected to the MPL through holes in the substrate. The MPL circuit is located in a protective housing 16, in which coaxial-strip transitions 15 are installed.

The combination of specially selected magnets 3, 4 provides a frequency lock of the ferrite device 10 by compensating for the thermal drift of the frequency caused by a decrease in the saturation magnetization of the ferrite 4πM ₀ (T ± ΔT) = 4πM ₀ (1∓α _F ΔT) and a decrease in the residual induction of permanent magnets B _M0 (T ± ΔT) = B _M0 (1∓α _M0 ΔT), B _M1 (T ± ΔT) = B _M1 (1∓α _M1 ΔT). In this case, we are talking about reversible demagnetization effects that occur in the range of operating temperatures T≤T _max ~ 100 ° C.

In the case of normal magnetization of ferrite, as shown in figure 1, figure 2, thermal stabilization of the resonant frequency of the precession ω ₀ = 2πf _{0 the} magnetic moment of ferrite

where γ = 2.83 MHz / G is the gyromagnetic ratio; µ ₀ - magnetic constant, occurs under the condition

where α _H is the temperature coefficient of the field in the working gap of the device.

The relationship of α _H with the temperature coefficients of demagnetization of permanent magnets α _M0 , α _M1 and ferrite α _F was obtained from the calculation of the field H ₀ in the working gap of the device. The calculations were carried out according to the Kirchhoff rules for magnetic circuits of devices according to claim 1 and claim 2 without taking into account the scattering fields and in the approximation of the rectangularity of the hysteresis loop. In these approximations, the temperature dependence of the field strength H ₀ in the working gap of the device according to claim 1 had the form (the formula for the field H _{0 of the} device according to claim 2 is obtained from (4) with the substitution G ₂ = 0)

where Ф _M0 = B _M0 S _M0 , Ф _M1 = B _M1 S _M1 - magnetic flux created by permanent magnets 3, 4;

G _M0 = µ ₀ S _M0 / l _M0 , G _M1 = µ ₀ S _M1 / l _M1 - intrinsic magnetic conductivity of permanent magnets;

S _M0 , l _M0 - the area of the poles and the thickness of the magnets in the working area 3;

S _M1 , l _M1 - the area of the poles and the thickness of the magnets in the regulatory region 4;

G ₀ = µ ₀ S ₀ / l ₀ , G ₁ = µ ₀ S ₁ / l ₁ , G ₂ = µ ₀ S ₂ / l ₂ — magnetic conductivities of the working, adjusting and lateral gaps, respectively;

S ₀ , l ₀ - the area and length of the working gap;

S ₁ , l ₁ - the area and length of the adjustment gap;

S ₂ , l ₂ - the area and length of the lateral gap.

From the expression (4) it follows that the previously obtained condition for frequency self-tuning (3) is equivalent to the condition

Condition (5) can be rewritten as

from which condition (2) immediately follows, which determines the ratio of the sizes of the poles of the permanent magnets. However, condition (6) makes sense only for positive values of the right and left sides of the equality. This imposes additional requirements:

which, ultimately, are reduced to condition (1), which determines the limits of permissible values of the coefficients of thermal demagnetization of permanent magnets. Note that condition (1) does not impose strictly defined requirements on the thermomagnetic properties of permanent magnets. This allows the implementation of the invention to use standard serial magnets that differ in chemical composition and, accordingly, magnetic properties.

The operation of the device according to claim 2 does not differ from that described above, but its design features create additional advantages. In this design (see figure 2) eliminated spurious leakage of magnetic flux through the lateral gap, which takes place in claim 1 (see figure 1). The withdrawal of magnets from the working area of the device creates an additional reserve of the magnetization area, which is used to proportionally reduce the dimensions of the device.

The invention is implemented as follows. The design of the device according to claim 1 was calculated, manufactured and tested, which was used to magnetize and thermally stabilize the frequency of a normally magnetized ferrite microwave resonator made on the basis of an epitaxial film of iron-yttrium garnet (YIG) 6.2 microns thick grown on a gadolinium-gallium garnet substrate ( Tretyakov Gallery) 0.5 mm thick. The dimensions of the film resonator were 1.5 × 1.5 mm. The operating frequency of the resonator was set f ₀ = 3.2 GHz.

To calculate the device used reference data for YIG: α _F = 0.32% / ° C, 4πM ₀ = 1.75 kG. In this case, the calculated field value in the working gap was μ ₀ H ₀ = 2πf ₀ / γ + 4πM ₀ = 8.93 kG, and the ratio 4πM ₀ α _F / (μ ₀ H ₀ ) = 0.06% / ° С. In accordance with condition (1), magnets based on Nd-Fe-B (α _M1 = 0.12% / ° C, B _M1 = 11.2 kG) and based on Sm-Co (α _M0 = 0.03% / ° C, B _M0 = 7.5 kG). The calculated ratio of the pole areas of the selected magnets according to condition (2) was S _M0 / S _M1 = 0.75. Calculations of the dimensions of the device were carried out for a cylindrical structure. The initial data were the dimensions of the working gap: ⌀7 × 1 mm.

In the design of the device according to claim 1, ring magnets with axial magnetization were used. The outer diameters of the Nd-Fe-B and Sm-Co rings were chosen equal to the diameter of the steel disk and amounted to D _M0 = D _M1 = D = 12 mm. The inner diameter of the magnet in the working area was set d _M0 = 7 mm. The calculated inner diameter of the magnet in the adjustment region was d _M1 = 4.2 mm. A steel disk with a thickness of h = 1.5 mm had an axial threaded hole for an adjusting screw M4 × 0.5. The lateral clearance was set l ₂ = 2 mm. The thicknesses of ring magnets l _M0 = l _M1 = _lM = 1.9 mm were calculated, which provided a given field in the working gap. For calculations of l _M , expression (4) was used at ΔT = 0. In reality, the thicknesses of the magnets were chosen with a small margin l _M = 2.0 mm. The resulting excess field in the working gap was easily eliminated by the adjusting screw. Given the selected value of l _{M, the} thickness of the additional pole in the working gap was 1 mm. The thicknesses of the side walls of the cylindrical screen and the additional screen were chosen equal to 0.5 mm, the thickness of the base of the screen was 1 mm. As a result, the overall dimensions of the device were: ⌀17 × 8 mm.

For comparison, the dimensions of the device were calculated according to claim 2 for the same parameters of the working gap and with the same types of permanent magnets. In accordance with the design of the device (see Fig. 2), the ring magnet in the control region also had axial magnetization, the outer diameter of the ring d _M = 7 mm, the inner diameter d _M1 = 2 mm (for the adjusting screw M2 × 0.25) and the specified thickness l ₁ = 2 mm. An annular magnet installed in the lateral gap had radial magnetization, an inner diameter d _M = 7 mm, an outer diameter D _M = 11 mm, and an estimated thickness h = 2.1 mm. According to the calculation results, the external dimensions of the device according to claim 2 were: ⌀ 12 × 7 mm, which is 2.3 times smaller in volume ratio than in the previous case.

In accordance with the calculations, the cylindrical design of the device according to claim 1 was made. Magnetic circuit parts were made of annealed low carbon steel. The control coil was wound from aluminum foil with a teflon layer. The electrical resistance of the coil did not exceed 2 ohms with a number of turns of ~ 100. Inputs and outputs of the power supply and the microwave signal were made of a fluoroplastic coaxial cable without an outer braid with a diameter of 1 mm, which were installed in the holes of the screen base on a hot landing. A film YIG resonator was installed in the working gap of the device, which was included in the feedback circuit of the transistor microwave generator and served as a frequency-setting element. The resonator was tuned to a given generation frequency by an adjusting screw. At the end of the adjustment, the cavity of the adjustment gap was filled with epoxy resin.

Tests of the device were carried out in the temperature range [0, + 60] ° C. The thermal stability was evaluated by measuring the relative values Δf / f _{0 of the} temperature deviation Δf of the operating frequency of the generator f ₀ . Frequency measurements were carried out with an accuracy of 1 kHz. As a result, it was found that the maximum frequency instability of the resonator did not exceed Δf / f ₀ ~ 10 ^-6 in the entire temperature range. The same order of magnitude Δf / f ₀ was observed during electrical tuning of the resonator in the frequency range (f ₀ ± 1) GHz. For comparison, the intrinsic temperature instability of the YIG resonator in the same temperature range was Δf / f ₀ ~ 10 ^-2 . From the comparison it is seen that the application of the invention increased the thermal stability of the YIG resonator by about 4 orders of magnitude, which is equivalent to thermostating of the device with an accuracy of maintaining the temperature to ~ 0.01 ° C.

Claims (2)

1. The magnetization and thermal stabilization of microwave ferrite devices, containing a closed steel screen, an internal steel plate located inside the closed steel screen parallel to its flat inner surfaces, the gap between the side surface of the inner steel plate and the inner side surface of the closed steel screen, permanent magnets located on both sides of the inner steel plate and connected by the same poles to it, and opposite poles to a flat top the closed steel shield, the adjusting steel screw, the ferrite element, the non-magnetic conductor electric coil located in the gap between the side surface of the inner steel plate and the inner side surface of the closed steel shield, the coaxial inputs of the microwave signal and coil power installed in the holes of the closed steel screen, characterized in that it is provided with a second steel plate covering the hole in the inner steel plate from the side of the fer itovogo element in the gap between it and the closed steel screen process opening which formed coaxially with the adjusting steel screw mounted in a threaded hole of the inner stainless steel plate, polymeric material fills the space between the adjusting steel screw and technological opening, the temperature coefficients of remanence of the permanent magnets α _M0 , α _M1 , satisfy the condition:

where α _F is the temperature coefficient of demagnetization of ferrite ferrite device; 4 πМ ₀ is its saturation magnetization; H ₀ - the required magnetic field strength in the working gap; µ ₀ is the magnetic constant,
the ratio of the area of the poles S _M0 and S _{M1 of} permanent magnets satisfies the condition:

where B _M0 and B _M1 are the residual inductions of the magnets selected according to condition (1). 2. The device according to claim 1, characterized in that the permanent magnets are installed in the gap between the side surface of the steel plate and the inner side surface of the steel closed screen, the coaxial inputs of the microwave signal and the power supply of the coil are installed in the holes of the side surface of the closed steel screen.

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