CN113950176A - Magnetron anode power supply ripple mixing multi-frequency heating device and method - Google Patents

Abstract

The invention discloses a magnetron anode power supply ripple mixing multi-frequency heating device and method, belonging to the field of microwave heating. The magnetron power supply is connected with a first cathode power supply line and a second cathode power supply line; The two cathode power lines are respectively connected with the two ends of the cathode of the magnetron; one end of the first capacitor is connected with the intermediate frequency signal generator, and the other end is connected with the first cathode power line; the cavity is provided with a feed port; the magnetron passes through the feed port Microwaves of multiple frequencies are input into the cavity. The device and method for multi-frequency heating of the magnetron anode power ripple mixing frequency are based on the nonlinear response characteristics of the magnetron, and the intermediate frequency signal is equivalent to the ripple of the magnetron anode voltage and is loaded on the magnetron anode voltage. , and the resonance signal excited by the magnetron itself is used as the local oscillation signal, and the output end of the magnetron generates microwaves of multiple frequencies by mixing the magnetron to heat the material uniformly.

Description

Magnetron anode power supply ripple mixing multi-frequency heating device and method

technical field

The invention belongs to the field of microwave heating, and in particular relates to a device and a method for heating a magnetron anode power supply ripple frequency mixing multi-frequency.

Background technique

As a new type of clean energy, microwave is widely used in many fields such as food, chemical industry, metallurgy and sewage treatment. Microwave directly acts on the polar molecules and charged particles inside the heated material, so microwave heating has the advantages of selective heating, bulk heating and cleaning heating. However, in the actual heating process of microwaves, there is generally a problem of uneven heating. The uneven heating causes the local temperature to be too high to form a "hot spot". The absorption capacity of many substances to electromagnetic waves is positively correlated with the temperature, and the temperature of the "hot spot" area rises more. The phenomenon of "thermal runaway" is finally formed, which greatly restricts the large-scale application of microwave energy.

With the development of science and technology and the improvement of people's living standards, microwave ovens are increasingly valued by consumers, and have gradually become an essential household appliance in the kitchen. Because microwave heating has the advantages of fast heating speed, low energy consumption and convenient control at any time, microwave ovens have gradually been widely used. However, with the continuous development of technology, consumers' requirements for microwave ovens have gradually increased, especially in terms of heating uniformity and heating efficiency of food. The operating frequency of traditional microwave ovens is 2450MHz, and only a single microwave source and a single frequency are used for heating. Although the microwave oven cavity is a multi-mode resonant cavity, multiple electromagnetic modes can be excited in the cavity, but the number of excited modes is limited after all. There is a phenomenon of uneven heating.

Scholars have done a lot of work on the improvement of microwave heating uniformity. In 1989, Ji Tianren proposed the concept of rotating antenna, that is, the mode field in the cavity changes while the antenna rotates with the driver, which leads to the change of the field distribution and improves the heating uniformity. In 1995, Yan Liping et al. mainly explored the influence of the rotation of the turntable in the microwave oven cavity on the heating uniformity and the relationship between the load size and area and the output power of the microwave oven. In 2001, Sung Yi and Lie Liu used FEM, that is, finite element method, to simulate and analyze regular rectangular waveguides and resonant cavities, and concluded that the more resonant frequencies excited in the cavity, the more uniform the field distribution. In 2006, Shinya Watanabe et al. used the THE method to calculate the heat conduction and the FDTD method to calculate the electromagnetic field, and studied the temperature distribution on the surface of the heated object. In 2017, Sang-Hyeon Bae and Min-GyoJeong studied a sustainable power-controlled microwave conveyor belt dryer made of multiple 2.45GHz microwave sources. By sequentially controlling the input power of the microwave sources, the uniform heating of the cavity can be improved. sex. The intermediate frequency signal refers to the frequency signal with the frequency band from 300KHz to 3000KHz, and in the radio frequency communication system, the signal before modulation is called the baseband signal, and the signal after mixing is called the radio frequency (or high frequency) signal. It's the IF signal.

So far, no research has been done on how to enable a single microwave source to output microwaves of multiple frequencies to uniformly heat materials, so as to improve the problem of uneven heating of materials by microwaves. Even if it is considered to use microwaves of multiple frequencies to heat the material, the number of microwave sources will generally increase, which will inevitably lead to an increase in cost. Or even if a single microwave source can output microwaves of multiple frequencies, a separate mixer and a large number of auxiliary accessories must be used, which also leads to an increase in cost. The invention realizes that a single microwave source outputs microwaves of multiple frequencies at low cost, and the frequency of the output microwaves is controllable and adjustable, so as to ensure the uniformity of microwave heating.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a magnetron anode power supply ripple mixing multi-frequency heating device and method in view of the above shortcomings, and it is intended to solve the problems of uneven microwave heating in the prior art. To achieve the above object, the present invention provides the following technical solutions:

The magnetron anode power supply ripple mixing multi-frequency heating device includes a magnetron power supply 1, a magnetron 2, an intermediate frequency signal generator 3, a first capacitor 41 and a cavity 8; the magnetron power supply 1 is connected with The first cathode power supply line 71 and the second cathode power supply line 72; the first cathode power supply line 71 and the second cathode power supply line 72 are respectively connected to both ends of the cathode of the magnetron 2; one end of the first capacitor 41 and the intermediate frequency The signal generator 3 is connected, and the other end is connected to the first cathode power line 71 ; the cavity 8 is provided with a feeding port; the magnetron 2 inputs microwaves of multiple frequencies into the cavity 8 through the feeding port.

Further, a first inductance 51 is provided on the first cathode power supply line 71 between the connection point of the first capacitor 41 and the first cathode power supply line 71 and the magnetron power supply 1 .

Further, the second cathode power line 72 is provided with a second inductor 52 .

Further, it also includes a third inductor 53; one end of the third inductor 53 is connected to the intermediate frequency signal generator 3 and one end of the first capacitor 41 connected to the intermediate frequency signal generator 3, and the other end is grounded.

Further, a fourth capacitor 44 is also included; one end of the fourth capacitor 44 is connected to the first cathode power supply line 71 between the magnetron power supply 1 and the first inductor 51 , and the other end is grounded.

Further, a fifth capacitor 45 is also included; one end of the fifth capacitor 45 is connected to the second cathode power supply line 72 between the magnetron power supply 1 and the second inductor 52 , and the other end is grounded.

Further, it also includes a first resistor 61, a second resistor 62 and a third resistor 63; both ends of the first resistor 61 and the third inductor 53 are connected in parallel; both ends of the second resistor 62 and the first inductor 51 are connected in parallel; Both ends of the third resistor 63 and the second inductor 52 are connected in parallel.

Further, it also includes an impedance matching regulator; the impedance matching regulator includes a second adjustable capacitor 42 and a third adjustable capacitor 43; one end of the second adjustable capacitor 42 is connected to the intermediate frequency signal generator 3 and the first capacitor One end of 41 connected to the intermediate frequency signal generator 3 is connected, and the other end is grounded; one end of the third adjustable capacitor 43 is connected to the intermediate frequency signal generator 3 and the first capacitor 41 is connected to one end of the intermediate frequency signal generator 3, and the other end is grounded .

Further, it also includes a circuit board; the first capacitor 41, the first inductor 51, the second inductor 52, the third inductor 53, the fourth capacitor 44, the fifth capacitor 45, the first resistor 61, the second resistor 62 and the The third resistor 63 is integrated on the circuit board; the circuit board includes a first port, a second port, a third port, a fourth port and a fifth port; the first port is located at the first inductor 51 and the magnetron power supply 1 on the first cathode power supply line 71; the second port is located on the second cathode power supply line 72 between the second inductor 52 and the magnetron power supply 1; the third port is located on the first inductor 51 and On the first cathode power line 71 between the magnetrons 2; the fourth port is on the second cathode power line 72 between the second inductor 52 and the magnetron 2; the fifth port is on the intermediate frequency signal generation Between the generator 3 and the first capacitor 41, the intermediate frequency signal generator 3 and the first capacitor 41 are connected.

A magnetron anode power supply ripple-mixing multi-frequency heating method adopts any one of the above-mentioned magnetron anode power supply ripple-mixing multi-frequency heating devices; the specific steps are: the magnetron power supply 1 supplies power to the magnetron 2; The intermediate frequency signal generator 3 generates an intermediate frequency signal, and the intermediate frequency signal is input to the first cathode power supply line 71 through the first capacitor 41. At this time, the intermediate frequency signal is equivalent to the ripple of the anode voltage of the magnetron 2 and is loaded into the magnetron 2. On the anode voltage, the resonance signal excited by the magnetron 2 itself is used as the local oscillation signal, and the intermediate frequency signal acts as the anode voltage ripple and the resonance signal of the magnetron 2. When the resonance signal of the magnetron 2 acts, the nonlinear response characteristics of the magnetron 2 The output end of the magnetron 2 generates microwaves of multiple frequencies, and the microwaves of multiple frequencies are input into the cavity 8 through the feeding port to heat the material 9 .

The beneficial effects of the present invention are:

The invention discloses a magnetron anode power supply ripple mixing multi-frequency heating device and method. The magnetron power supply is connected with a first cathode power supply line and a second cathode power supply line; the first cathode power supply line and the second cathode power supply line are respectively It is connected with both ends of the cathode of the magnetron; one end of the first capacitor is connected with the intermediate frequency signal generator, and the other end is connected with the power line of the first cathode; the cavity is provided with a feeding port; microwave frequency. The device and method for multi-frequency heating of the magnetron anode power supply ripple mixing frequency of the present invention are based on the nonlinear response characteristics of the magnetron, and the intermediate frequency signal is equivalent to the ripple of the magnetron anode voltage and is loaded on the magnetron anode voltage. , and the resonance signal excited by the magnetron itself is used as the local oscillation signal, and the output end of the magnetron generates microwaves of multiple frequencies by mixing the magnetron to heat the material uniformly.

Description of drawings

1 is a schematic diagram of the circuit principle of a magnetron anode power supply ripple mixing multi-frequency heating device of the present invention, and the cavity is not shown;

Figure 2 is the equivalent circuit diagram of the magnetron; according to the research on the structure and function of the resonant cavity of the magnetron, the resonant cavity of the magnetron can be equivalent to an RLC parallel resonant circuit, and g+jb is the equivalent magnetron source part, G+jB is equivalent load, R, L, C are equivalent resistance, equivalent inductance and equivalent capacitance respectively;

Figure 3 is the time-domain image of the output signal of the magnetron; the derived expression of the output signal of the free-oscillating magnetron in the steady state with the anode voltage containing the intermediate frequency signal is plotted, and the depth of the sideband envelope represents the loaded intermediate frequency The amplitude of the signal, and the frequency of the sideband envelope is related to the frequency of the IF signal;

Figure 4 is the frequency domain image of the output signal of the magnetron; the figure obtained by fast Fourier transform of the derived expression, the frequency point with the highest intensity in the image represents the center frequency of the free oscillating magnetron, and the frequency points on both sides of the center frequency The sub-frequency point with slightly weaker intensity represents the new frequency point obtained after the magnetron local oscillator frequency and the intermediate frequency signal frequency are mixed, and the frequency difference between the center frequency and the sub-frequency component is the frequency of the intermediate frequency signal;

Figure 5 is a waveform diagram of the anode voltage of the magnetron loaded with an intermediate frequency signal; the ideal anode voltage is a DC voltage originally, and the loaded intermediate frequency signal is reflected as the ripple component on the DC voltage. Here, the complex intermediate frequency signal carrying information will be Simplified to a single frequency sinusoidal signal;

Figure 6 is the time-domain image of the output signal of the magnetron in the free oscillation state. The magnetron is modeled by electromagnetic simulation software. The simulation calculation obtains the time-domain output image of the magnetron in the free oscillation stable state, and the sideband envelope characteristics Similar to the image derived from Figure 3;

Figure 7 is the frequency domain image of the output signal of the magnetron in the free oscillation state. The output spectrum of the magnetron is obtained by simulation calculation. The relationship between the center frequency and the sub-frequency component on the image is similar to the image derived from Figure 4. ;

Figure 8 is the frequency domain image of the output signal of the magnetron when the intermediate frequency signal is not loaded, the spectrum is the output spectrum of the 2M244-M1 magnetron produced by Panasonic in the free oscillation state;

Fig. 9 is the frequency domain image of the magnetron output signal when the 2MHz intermediate frequency signal is loaded, and the relationship between the center frequency and the sub-frequency component on the image is similar to the image derived from Fig. 4;

Figure 10 is the frequency domain image of the magnetron output signal when the 3MHz intermediate frequency signal is loaded, and the relationship between the center frequency and the sub-frequency component on the image is similar to the image derived from Figure 4;

Figure 11 is the frequency domain image of the magnetron output signal when the 4MHz intermediate frequency signal is loaded, and the relationship between the center frequency and the sub-frequency component on the image is similar to the image derived from Figure 4;

Fig. 12 is the formula that the high-frequency output voltage under the free oscillation state of the magnetron can be obtained by solving the real part expression as VRF(t);

Fig. 13 is the formula of the transient output frequency ω(t) of the free oscillation state of the magnetron that can be obtained by solving the imaginary part expression;

Figure 14 is a schematic diagram of the material being located in the cavity;

Figure 15 is a heating simulation diagram of the cavity designed as a rectangular cavity of 405×295×340mm, the potato is 50mm directly below the center point of the cavity, the initial temperature is 293.15K, and the heating time is 20s. The single-frequency input microwave is 2.45GHz and the power is 600W. , it can be seen that the average temperature ave=313.68K, cov=0.5352;

Figure 16 is a heating simulation diagram of a rectangular cavity with a cavity design of 405×295×340mm, the potato is 50mm directly below the center point of the cavity, the initial temperature is 293.15K, and the heating time is 20s. GHz, 2.454GHz) microwave, power 200W, it can be seen that the average temperature ave=310.63K, cov=0.3738;

Figure 17 shows that the experimental results of the output power of the three main frequencies of microwaves can be close to the same.

In the drawings: 1-magnetron power supply, 2-magnetron, 3-intermediate frequency signal generator, 41-first capacitor, 42-second adjustable capacitor, 43-third adjustable capacitor, 44-fourth Capacitor, 45-fifth capacitor, 51-first inductor, 52-second inductor, 53-third inductor, 61-first resistor, 62-second resistor, 63-third resistor, 71-first cathode power supply Line, 72-second cathode power line, 8-cavity, 9-material.

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to the following examples.

Example 1:

See Figures 1 to 11 and 14. The magnetron anode power supply ripple mixing multi-frequency heating device includes a magnetron power supply 1, a magnetron 2, an intermediate frequency signal generator 3, a first capacitor 41 and a cavity 8; the magnetron power supply 1 is connected with The first cathode power supply line 71 and the second cathode power supply line 72; the first cathode power supply line 71 and the second cathode power supply line 72 are respectively connected to both ends of the cathode of the magnetron 2; one end of the first capacitor 41 and the intermediate frequency The signal generator 3 is connected, and the other end is connected to the first cathode power line 71 ; the cavity 8 is provided with a feeding port; the magnetron 2 inputs microwaves of multiple frequencies into the cavity 8 through the feeding port.

The working principle of a single magnetron capable of outputting multiple frequencies of microwaves:

The invention makes full use of the characteristics of the magnetron as an amplitude nonlinear response device, and uses the magnetron as a mixer in combination with the influence of the anode voltage ripple of the magnetron on its output spectrum characteristics. The magnetron power supply 1 supplies power to the magnetron 2; the intermediate frequency signal generator 3 generates a modulated intermediate frequency signal, and the intermediate frequency signal is input to the first cathode power supply line 71 through the first capacitor 41. At this time, the intermediate frequency signal, etc. The effect is that the ripple of the anode voltage of the magnetron 2 is loaded on the anode voltage of the magnetron 2, and the resonance signal excited by the magnetron 2 itself is used as the local oscillation signal, and the intermediate frequency signal is used as the anode voltage ripple and the magnetron. When the resonant signal of 2 acts, the nonlinear response characteristics of the magnetron 2 make the output end of the magnetron 2 generate microwaves of multiple frequencies, which are the result of the linear operation between the frequency of the intermediate frequency signal and the frequency of the resonant signal. At the same time, microwaves of multiple frequencies can be directly input into the cavity 8 through the feed port to uniformly heat the material 9 .

Magnetron structure: The magnetron has a cylindrical anode, the anode blade is installed on the inner wall of the anode along the radial direction, the spiral filament is used as the cathode, the cathode is located in the center of the magnetron, the antenna is installed on one of the anode blades, and many A cooling fin is placed on the outer circumferential surface of the anode, and two magnets are installed at the top and bottom of the anode to form a magnetic field. The magnetron power supply 1 supplies power to the cathode through the first cathode power supply line 71 and the second cathode power supply line 72, and heats the cathode filament to emit thermionic electrons. The resonant cavity converts electron energy into high-frequency energy, namely microwaves, while doing cycloid motion, and the microwaves are emitted through the antenna. The magnetron power supply 1 provides 3.3V for the cathode, the anode is grounded, and there is a negative high voltage of about 4kV between the cathode and the anode.

The first cathode power supply line 71 and the second cathode power supply line 72 are respectively directly or indirectly connected to the cathode ends of the magnetron 2; the cathode ends can be respectively connected to the first cathode power supply line 71 and the second cathode through a choke coil. Power cord 72. The first capacitor 41 is used to block direct current and alternating current, to prevent the high voltage direct current of the magnetron power supply 1 from running into the intermediate frequency signal generator 3, and at the same time to ensure that the modulated intermediate frequency signal generated by the intermediate frequency signal generator 3 can be input to the first cathode. on power cord 71.

Theoretical derivation:

Referring to Fig. 2, the present invention is based on the equivalent RLC resonant circuit model of the magnetron, and the circuit equation under the free oscillation stable state of the magnetron:

in,

ω is the oscillation frequency of the magnetron, that is, the oscillation frequency of the signal generated by the output end of the magnetron; ω ₀ is the local oscillation frequency of the resonant cavity, that is, the resonant signal excited by the magnetron itself is used as the frequency of the local oscillation signal; Q ₀ is the intrinsic quality factor of the resonant circuit; Q _ext is the external quality factor of the resonant circuit; V _dc is the anode voltage of the magnetron, that is, the voltage between the cathode and the anode of the magnetron, and the anode is grounded; V _RF is the high-frequency voltage , that is, the voltage of the signal generated at the output end of the magnetron; A is the amplitude of the intermediate frequency signal; f is the frequency of the intermediate frequency signal; g+jb is the equivalent magnetron source part, g is the electron conductance of the magnetron source, b is the electronic susceptance of the magnetron source; G+jB is the equivalent load, G is the electronic conductance of the load end, B is the electronic susceptance of the load end; j is the imaginary unit; b ₀ , tanα are constants; R, L, C are the equivalent resistance, equivalent inductance and equivalent capacitance, respectively; t is the time variable. JCSlater once published a paper named "THE PHASING OF MAGNETRONS" on April 3, 1947, in which the above theoretical principles are described in detail. It is now common knowledge in the field and can be used directly.

In order to analyze the start-up process of the magnetron, in the process of its initial oscillation, it can be assumed that the amplitude of its voltage changes exponentially with time, and the frequency is expressed as a complex number, and its imaginary part represents the relationship of exponential growth, namely:

ω=ω ₁ +jω ₂

因此定义

则ω＝ω₁+jГ(t)。此时，磁控管自由振荡稳定状态下的电路方程可以改写为：The relationship of the high frequency voltage with time is expressed as

So define

Then ω=ω ₁ +jГ(t). At this point, the circuit equation in the free oscillation steady state of the magnetron can be rewritten as:

Separating the real and imaginary parts of this equation gives:

in

Solving the real part expression, the high-frequency output voltage of the magnetron in the free oscillation state can be obtained as:

Similarly, by solving the imaginary part expression, the transient output frequency of the free oscillation state of the magnetron can be obtained as:

in,

It shows that after the magnetron works stably, its frequency consists of three parts:

代表由电子束引起的频率前推效应；

代表由负载引起的频率牵引效应。ω ₀ represents the local oscillator frequency of the resonator;

represents the frequency push effect caused by the electron beam;

Represents the frequency pulling effect caused by the load.

To sum up, when the intermediate frequency signal is loaded on the anode voltage of the magnetron, which is equivalent to the anode voltage ripple, the output signal of the magnetron in the free oscillation stable state is expressed as:

V(t)= _VRF (t)·sin(ω(t)·t)

Fast Fourier transform is performed on the magnetron output expression derived theoretically in the previous section, and the frequency domain diagram corresponding to the expression can be obtained. Figure 3 is the time-domain image of the output signal of the magnetron; the derived expression of the output signal of the free-oscillating magnetron in the steady state with the anode voltage containing the intermediate frequency signal is plotted, and the depth of the sideband envelope represents the loaded intermediate frequency The amplitude of the signal, and the frequency of the sideband envelope is related to the frequency of the IF signal. Figure 4 is the frequency domain image of the output signal of the magnetron; the figure obtained by fast Fourier transform of the derived expression, the frequency point with the highest intensity in the image represents the center frequency of the free oscillating magnetron, and the frequency points on both sides of the center frequency The sub-frequency point with slightly weaker intensity represents the new frequency point obtained by mixing the local oscillator frequency of the magnetron with the frequency of the intermediate frequency signal. The frequency difference between the center frequency and the sub-frequency component is the frequency of the intermediate frequency signal. According to the frequency domain image output by the magnetron, a slightly weaker sub-frequency component appears on both sides of the center frequency of the magnetron output signal, and the frequency difference between the center frequency and the sub-frequency component is the intermediate frequency loaded on the anode voltage. The frequency of the signal means that the magnetron acts as the intended mixer.

Figure 5 is a waveform diagram of the anode voltage of the magnetron loaded with an intermediate frequency signal; the ideal anode voltage is a DC voltage originally, and the loaded intermediate frequency signal is reflected as the ripple component on the DC voltage. Here, the complex intermediate frequency signal carrying information will be Simplified to a single frequency sinusoidal signal. Figure 6 is the time-domain image of the output signal of the magnetron in the free oscillation state. The magnetron is modeled by electromagnetic simulation software. The simulation calculation obtains the time-domain output image of the magnetron in the free oscillation stable state, and the sideband envelope characteristics Similar to the image derived from Figure 3. Figure 7 is the frequency domain image of the output signal of the magnetron in the free oscillation state. The output spectrum of the magnetron is obtained by simulation calculation. The relationship between the center frequency and the sub-frequency component on the image is similar to the image derived from Figure 4. . In the electromagnetic simulation software CST Studio Suite, the free oscillation state magnetron with the intermediate frequency signal loaded on the anode voltage as the equivalent ripple is simulated, and the output spectrum results obtained also verify that the magnetron can function as a mixer.

On this basis, the present invention builds a test system to verify the results of numerical calculation and software simulation. The system uses the 2M244-M1 magnetron produced by Panasonic. When the intermediate frequency signal is not loaded, the output spectrum of the magnetron is As shown in FIG. 8 ; after loading intermediate frequency signals of different frequencies, the output spectrum of the magnetron is shown in FIG. 9 , FIG. 10 , and FIG. 11 . The relationship between the center frequency and the sub-frequency component on the image is similar to the image derived from Figure 4. The frequency difference between the center frequency and the sub-frequency component is the frequency of the intermediate frequency signal loaded on the anode voltage, indicating that the intermediate frequency signal The ripple equivalent to the anode voltage of the magnetron is loaded on the anode voltage of the magnetron, and the resonance signal excited by the magnetron itself is used as the local oscillation signal, and the output of the magnetron can be mixed by using the magnetron. The main three frequencies of microwaves are generated at the end of the magnetron, that is, the center frequency and the slightly weaker sub-frequency components appearing on both sides of the center frequency, so the intermediate frequency signal can not only make the output end of the magnetron generate the main three frequencies of microwaves, but also It can affect the frequency distribution, make the frequency adjustable and controllable, and the main three frequencies of microwave can heat the material evenly.

Embodiment 2:

See Figures 1 to 11 and 14. On the basis of the first embodiment, the first inductance 51 is provided on the first cathode power supply line 71 between the connection point of the first capacitor 41 and the first cathode power supply line 71 and the magnetron power supply 1 . It can be seen from the above structure that the first inductor 51 is used to separate AC and DC, preventing the intermediate frequency signal from entering the magnetron power supply 1, and at the same time ensuring that the high-voltage DC and low-frequency DC filament currents can enter the magnetron.

The second cathode power line 72 is provided with a second inductor 52 . It can be seen from the above structure that the second inductor 52 is used to separate AC and DC to prevent the intermediate frequency signal from entering the magnetron power supply 1, and at the same time to ensure that the high-voltage DC and low-frequency DC filament currents can enter the magnetron.

It also includes a third inductor 53; one end of the third inductor 53 is connected to the intermediate frequency signal generator 3 and one end of the first capacitor 41 connected to the intermediate frequency signal generator 3, and the other end is grounded. It can be seen from the above structure that when the first capacitor 41 fails and short-circuits, the high voltage is directly applied to the intermediate frequency signal generator 3, so the third inductor 53 is added. When the first capacitor 41 fails and short-circuits, the high-voltage DC is grounded through the third inductor 53. . The third inductor 53 functions to protect the intermediate frequency signal generator 3 .

It also includes a fourth capacitor 44; one end of the fourth capacitor 44 is connected to the first cathode power supply line 71 between the magnetron power supply 1 and the first inductor 51, and the other end is grounded. It can be known from the above structure that the fourth capacitor 44 prevents the high frequency signal from returning to the magnetron power supply 1 .

It also includes a fifth capacitor 45; one end of the fifth capacitor 45 is connected to the second cathode power supply line 72 between the magnetron power supply 1 and the second inductor 52, and the other end is grounded. It can be seen from the above structure that the fifth capacitor 45 prevents the high frequency signal from returning to the magnetron power supply 1 .

It also includes a first resistor 61, a second resistor 62 and a third resistor 63; both ends of the first resistor 61 and the third inductor 53 are connected in parallel; both ends of the second resistor 62 and the first inductor 51 are connected in parallel; Both ends of the three resistors 63 and the second inductor 52 are connected in parallel. It can be seen from the above structure that the first resistor 61 , the second resistor 62 and the third resistor 63 are used to reduce the Q value of the third inductor 53 , the first inductor 51 and the second inductor 52 respectively, so as to prevent the inductors from resonating.

It also includes an impedance matching regulator; the impedance matching regulator includes a second adjustable capacitor 42 and a third adjustable capacitor 43; one end of the second adjustable capacitor 42 is connected to the intermediate frequency signal generator 3 and the first capacitor 41 at the intermediate frequency One end of the signal generator 3 is connected, and the other end is grounded; one end of the third adjustable capacitor 43 is connected to the intermediate frequency signal generator 3 and the first capacitor 41 is connected to one end of the intermediate frequency signal generator 3, and the other end is grounded. It can be known from the above structure that the impedance matching regulator is used for impedance matching with the circuit.

It also includes a circuit board; the first capacitor 41, the first inductor 51, the second inductor 52, the third inductor 53, the fourth capacitor 44, the fifth capacitor 45, the first resistor 61, the second resistor 62 and the third resistor 63 is integrated on the circuit board; the circuit board includes a first port, a second port, a third port, a fourth port and a fifth port; the first port is located between the first inductor 51 and the magnetron power supply 1 on the first cathode power supply line 71 of the 2 on the first cathode power supply line 71; the fourth port is located on the second cathode power supply line 72 between the second inductor 52 and the magnetron 2; the fifth port is located on the intermediate frequency signal generator 3 and Between the first capacitors 41, the intermediate frequency signal generator 3 and the first capacitor 41 are connected. It can be seen from the above structure that the first capacitor 41 , the first inductor 51 , the second inductor 52 , the third inductor 53 , the fourth capacitor 44 , the fifth capacitor 45 , the first resistor 61 , the second resistor 62 and the third resistor 63 It is integrated on the circuit board, which is convenient for modular use. The intermediate frequency signal generator 3, the magnetron power supply 1, and the magnetron 2 are directly connected to the corresponding ports of the circuit board, and the structure is more simplified and simpler.

The three main intensities of microwave frequencies that generally appear are the center frequency and the slightly weaker sub-frequency components appearing on both sides of the center frequency. After adjusting the matching of the modulation circuit, the intensity of the center frequency output by the magnetron and the intensity of the sub-frequency components can be adjusted. The same, that is, the same power, which will help the material to be heated evenly.

Embodiment three:

See Figures 1 to 11 and 14. A method for heating a magnetron anode power supply ripple frequency mixing and multi-frequency, using any of the above-mentioned embodiments of the magnetron anode power supply ripple mixing and multi-frequency heating device; the specific steps are: the magnetron power supply 1 is the magnetron 2 Power supply; the intermediate frequency signal generator 3 generates an intermediate frequency signal, and the intermediate frequency signal is input to the first cathode power supply line 71 through the first capacitor 41. At this time, the intermediate frequency signal is equivalent to the ripple of the anode voltage of the magnetron 2 and is loaded into the magnetron On the anode voltage of tube 2, the resonance signal excited by the magnetron 2 itself is used as the local oscillation signal, and the intermediate frequency signal acts as the anode voltage ripple and the resonance signal of the magnetron 2, the non-linear response of the magnetron 2 The characteristic of the magnetron 2 generates microwaves of multiple frequencies at the output end of the magnetron 2 , and the microwaves of multiple frequencies are input into the cavity 8 through the feeding port to heat the material 9 . The method of the invention makes full use of the characteristics of the magnetron as an amplitude nonlinear response device, combined with the influence of the anode voltage ripple of the magnetron on its output spectrum characteristics, uses the magnetron as a mixer, and does not need to separately set a mixer and With a large number of auxiliary accessories, the output end of the magnetron 2 can generate multiple microwaves with controllable and adjustable frequencies, and the microwaves with multiple frequencies are input into the cavity 8 through the feed port to uniformly heat the material 9 .

In fact, the magnetron outputs a large number of microwaves of different frequencies, but the three main frequencies of microwaves have high intensities, so only the microwaves of these three frequencies are considered, and the remaining low-intensity microwaves can be ignored. It only needs to be verified in the COMSOL Multiphysics simulation software that the magnetron outputs three different frequency microwaves to improve the heating uniformity of the material:

Experiment description: Because it is impossible to feed sources with different frequencies at the same time in this software, the present invention uses a single frequency source to feed in COMSOL Multiphysics, and the temperature rise results obtained at different frequencies are exported to MATLAB software for calculation. This is to simulate the effect of the three-frequency output of the magnetron at the same time.

First, the cavity is designed as a rectangular cavity of 405×295×340mm, the magnetron is fed by a BJ-26 rectangular waveguide, and potatoes with a size of 50×50×50mm are placed in the cavity as materials. In the simulation verification, a single microwave source with a frequency of 2.45GHz and a power of 600W is used with a center frequency of 2.45GHz and a frequency difference of 2-8MHz (for example, a frequency difference of 2MHz means that the three microwave frequencies are 2.448GHz, 2.45GHz, and 2.452GHz). Three different frequency microwaves with a power of 200W were fed separately, and then the temperature rise data was imported into MATLAB for calculation, and the three-frequency heating results were simulated. This method was used to compare and verify the improvement effect of heating uniformity.

Use MTALAB software to calculate the average temperature (ave) and temperature coefficient of variation (cov) in each case. The temperature coefficient of variation (cov) is the ratio of the standard deviation of the original data to the average of the original data, reflecting the absolute value of the degree of dispersion of the data, cov Smaller values indicate more uniform heating. At the same time, the improvement of heating uniformity under different positions of potatoes was calculated.

The following table shows the data when the potato is 50mm directly below the center point of the cavity:

The following table shows the data of potatoes at 80mm directly below the center point:

The cavity is designed as a rectangular cavity of 450×350×340mm. The following table shows the data of the potato being 80mm directly below the center point:

From the above data, it can be concluded that the modulation circuit that modulates the intermediate frequency signal to the magnetron high-voltage power supply makes the magnetron mix frequency to generate a microwave signal with a specified frequency difference, and realizes the microwave heating of the three-frequency output to improve the heating uniformity. It has good effect and can achieve the expected purpose. According to the experiment, the frequency of the optimal intermediate frequency signal can be selected to make the heating uniformity of the material optimal.

Figure 15 is a heating simulation diagram of the cavity designed as a rectangular cavity of 405×295×340mm, the potato is 50mm directly below the center point of the cavity, the initial temperature is 293.15K, and the heating time is 20s. The single-frequency input microwave is 2.45GHz and the power is 600W. , it can be seen that the average temperature ave=313.68K, cov=0.5352;

Figure 16 is a heating simulation diagram of a rectangular cavity with a cavity design of 405×295×340mm, the potato is 50mm directly below the center point of the cavity, the initial temperature is 293.15K, and the heating time is 20s. GHz, 2.454GHz) microwave, power 200W, it can be seen that the average temperature ave=310.63K, cov=0.3738;

From the comparison of Figures 15 and 16, it can be seen that the maximum temperature and average temperature of triple-frequency heating are not as high as those of single-frequency heating, but the difference in average temperature is small, and it can be seen from the temperature distribution of the body surface that triple-frequency heating does exist for uniformity. certain improvement.

As can be seen from Figure 17, by changing the power of the intermediate frequency signal, the experiment can obtain that the output power of the three main frequencies of microwaves is close to the same, and the closer it is, the more uniform the heating is.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied to other related All technical fields are similarly included in the scope of patent protection of the present invention.

Claims (10)

1. Magnetron anode power supply ripple frequency mixing multifrequency heating device, its characterized in that: the device comprises a magnetron power supply (1), a magnetron (2), an intermediate frequency signal generator (3), a first capacitor (41) and a cavity (8); the magnetron power supply (1) is connected with a first cathode power supply line (71) and a second cathode power supply line (72); the first cathode power line (71) and the second cathode power line (72) are respectively connected with two ends of the cathode of the magnetron (2); one end of the first capacitor (41) is connected with the intermediate frequency signal generator (3), and the other end of the first capacitor is connected with a first cathode power line (71); a feed port is arranged on the cavity (8); the magnetron (2) inputs microwaves of multiple frequencies into the cavity (8) through the feed port.

2. The magnetron anode power supply ripple mixing multifrequency heating apparatus of claim 1, wherein: and a first inductor (51) is arranged on the first cathode power line (71) between the connection intersection point of the first capacitor (41) and the first cathode power line (71) and the magnetron power supply (1).

3. The magnetron anode power supply ripple mixing multifrequency heating apparatus of claim 2, wherein: and a second inductor (52) is arranged on the second cathode power line (72).

4. The magnetron anode power supply ripple mixing multifrequency heating apparatus of claim 3, wherein: further comprising a third inductance (53); one end of the third inductor (53) is connected with the intermediate frequency signal generator (3) and one end of the first capacitor (41) connected with the intermediate frequency signal generator (3), and the other end of the third inductor is grounded.

5. The magnetron anode power supply ripple mixing multifrequency heating apparatus of claim 4, wherein: further comprising a fourth capacitance (44); one end of the fourth capacitor (44) is connected with a first cathode power line (71) between the magnetron power supply (1) and the first inductor (51), and the other end of the fourth capacitor is grounded.

6. The magnetron anode power supply ripple mixing multifrequency heating apparatus of claim 5, wherein: further comprising a fifth capacitance (45); one end of the fifth capacitor (45) is connected with a second cathode power line (72) between the magnetron power supply (1) and the second inductor (52), and the other end of the fifth capacitor is grounded.

7. The magnetron anode power supply ripple mixing multifrequency heating apparatus of claim 6, wherein: the circuit also comprises a first resistor (61), a second resistor (62) and a third resistor (63); the first resistor (61) and the third inductor (53) are connected in parallel; the second resistor (62) is connected with the two ends of the first inductor (51) in parallel; the third resistor (63) is connected with the second inductor (52) in parallel.

8. The magnetron anode power supply ripple mixing multifrequency heating apparatus of claim 7, wherein: also includes an impedance matching adjuster; the impedance matching regulator comprises a second adjustable capacitor (42) and a third adjustable capacitor (43); one end of the second adjustable capacitor (42) is connected with the intermediate frequency signal generator (3) and one end of the first capacitor (41) connected with the intermediate frequency signal generator (3), and the other end of the second adjustable capacitor is grounded; one end of the third adjustable capacitor (43) is connected with the intermediate frequency signal generator (3) and one end of the first capacitor (41) connected with the intermediate frequency signal generator (3), and the other end of the third adjustable capacitor is grounded.

9. The magnetron anode power supply ripple mixing multifrequency heating apparatus of claim 8, wherein: the circuit board is also included; the first capacitor (41), the first inductor (51), the second inductor (52), the third inductor (53), the fourth capacitor (44), the fifth capacitor (45), the first resistor (61), the second resistor (62) and the third resistor (63) are integrated on a circuit board; the circuit board comprises a first port, a second port, a third port, a fourth port and a fifth port; the first port is located on a first cathode power line (71) between the first inductor (51) and the magnetron power supply (1); the second port is located on a second cathode power line (72) between the second inductor (52) and the magnetron power supply (1); the third port is located on a first cathode power line (71) between the first inductor (51) and the magnetron (2); the fourth port is positioned on a second cathode power line (72) between the second inductor (52) and the magnetron (2); the fifth port is positioned between the intermediate frequency signal generator (3) and the first capacitor (41) to communicate the intermediate frequency signal generator (3) with the first capacitor (41).

10. The magnetron anode power supply ripple frequency mixing multi-frequency heating method is characterized in that: the magnetron anode power supply ripple mixing multi-frequency heating device of any one of claims 1 to 9 is adopted; the method comprises the following specific steps: the magnetron power supply (1) supplies power to the magnetron (2); the medium frequency signal generator (3) generates a medium frequency signal, the medium frequency signal is input to a first cathode power line (71) through a first capacitor (41), the medium frequency signal is equivalent to a ripple of an anode voltage of the magnetron (2) and is loaded to the anode voltage of the magnetron (2), a resonance signal excited by the magnetron (2) is used as a local oscillation signal, when the medium frequency signal is used as the anode voltage ripple and is acted with the resonance signal of the magnetron (2), the output end of the magnetron (2) generates microwaves with multiple frequencies due to the nonlinear response characteristic of the magnetron (2), and the microwaves with multiple frequencies are input into the cavity (8) through the feed port to heat the material (9).

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