A microwave impedance adjustment circuit and a microwave device having the same

Abstract

This application provides a microwave impedance adjustment circuit and a microwave device having the same. The microwave impedance adjustment circuit includes a control unit connected to the control unit and a tuning unit connected to the control unit. The tuning unit includes at least three microstrip lines of different lengths, each microstrip line having a corresponding switch for controlling the on / off state of the microstrip lines. The control unit controls the on / off state of multiple switches to adjust an antenna element. The tuning unit is also connected to the antenna element. The microwave impedance adjustment circuit and microwave device provided in this application achieve impedance adjustment by adjusting the length of the microstrip lines, replacing the inductor-capacitor adjustment in the prior art. This results in higher accuracy, significantly reduced adjustment time, and lower costs.

Description

Technical Field

[0001] This application relates to the field of microwave technology, and more specifically to a microwave impedance adjustment circuit and a microwave device having the same. Background Technology

[0002] Microwave heating equipment, as a common household appliance, is widely used in home cooking, one important application being the defrosting of frozen food. In defrosting applications, the quantity and type of food to be defrosted can cause impedance mismatch in the radio frequency amplifier providing defrosting energy, leading to reduced defrosting energy and longer defrosting time. Existing microwave heating equipment addresses this by adjusting the inductance or capacitance for matching; however, due to the inherent errors and time lags in both capacitors and inductors, this matching circuit has a long adjustment time and low accuracy.

[0003] Therefore, it is necessary to provide an impedance adjustment circuit so that the RF amplifier can be in the optimal matching state regardless of the quantity or type of food that needs to be defrosted and heated, so as to make the defrosting and heating energy better and the defrosting and heating time shorter. Summary of the Invention

[0004] This application provides a microwave impedance adjustment circuit and a microwave device incorporating the same. By setting multiple microstrip lines and adjusting their lengths, microwave impedance is adjusted, eliminating the need for inductors or capacitors required in existing solutions. This results in higher accuracy and faster adjustment time. Furthermore, the elimination of inductors and capacitors, along with the compact integration of multiple microstrip lines onto a PCB board, helps reduce costs.

[0005] One embodiment of this application provides a microwave impedance adjustment circuit, including: a control unit and a tuning unit connected to the control unit. The tuning unit includes at least three microstrip lines of different lengths, and each microstrip line of different lengths is provided with a corresponding switch. The switch is used to control the on / off state of the microstrip line. The control unit is used to control the on / off state of the plurality of switches to adjust the antenna unit. The tuning unit is also used to connect the antenna unit.

[0006] Furthermore, the multiple microstrip lines are connected in series.

[0007] Furthermore, each of the switches is connected in parallel to the corresponding microstrip line, and the microstrip line is short-circuited when the switch is closed.

[0008] Furthermore, the multiple microstrip lines are formed by switching a whole microstrip line disposed on the circuit board on and off through the multiple switches.

[0009] Furthermore, the multiple microstrip lines have the same length.

[0010] Furthermore, the multiple microstrip lines have multiple sets of different lengths, wherein the microstrip lines in each set of microstrip lines are of the same length, and the lengths of the microstrip lines in different sets of microstrip lines are in a multiple relationship.

[0011] Furthermore, the microwave impedance adjustment circuit further includes: a signal source for generating microwave signals; an RF amplifier connected to the signal source and the control unit for amplifying power and outputting it to the antenna; and a power detection circuit connected to the RF amplifier and the tuning unit for detecting the power of the RF amplifier and feeding the detection result back to the control unit; wherein the control unit controls the on / off state of the switch based on the detection result.

[0012] Furthermore, the power detection circuit is used to detect the forward power and reverse power of the RF amplifier, and the control unit determines the matching status of the RF amplifier and the antenna unit based on the forward power and reverse power.

[0013] Furthermore, at least one segment of the microstrip line has a meandering structure with reciprocating folds.

[0014] Furthermore, at least one segment of the microstrip line is at least partially surrounded by another segment of the microstrip line.

[0015] Furthermore, at least one section of the microstrip line is simultaneously disposed on both sides of the circuit board.

[0016] Furthermore, the multiple microstrip lines of the tuning unit are all disposed on both sides of the circuit board.

[0017] Furthermore, at least one segment of the microstrip line includes a first metal layer disposed on one side surface of the circuit board and a second metal layer disposed on the other side surface of the circuit board; wherein the first metal layer and the second metal layer have the same orientation, and the first metal layer and the second metal layer are electrically connected by metallized vias arranged in an array along their extension direction.

[0018] Furthermore, the microwave impedance adjustment circuit also includes a matching unit connected to the power detection circuit and the tuning unit, used for matching the antenna unit and the RF amplifier.

[0019] Another aspect of this application provides a microwave device for defrosting food, including an antenna unit, a cavity, and a microwave impedance adjustment circuit as described in the preceding aspect of this application.

[0020] This application discloses a microwave impedance adjustment circuit and microwave device. By using multiple microstrip lines, the length of the microstrip lines is controlled to adjust the microwave impedance. This eliminates the inductors and capacitors found in existing solutions, effectively solving the problems of low adjustment accuracy and long adjustment time caused by errors and time delays in inductors and capacitors. It provides a microwave impedance adjustment method that can significantly shorten the adjustment time and achieve high adjustment accuracy. Furthermore, the multiple microstrip lines can be compactly integrated onto a PCB board, further reducing costs. Attached Figure Description

[0021] To make the technical problems solved, the technical means adopted, and the technical effects achieved by the embodiments of this application clearer, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. However, it should be noted that the accompanying drawings described below are merely drawings of exemplary embodiments of this application. For those skilled in the art, drawings of other embodiments can be obtained based on these drawings without any creative effort.

[0022] Figure 1 A schematic diagram of a microwave impedance adjustment circuit provided in an embodiment of this application; Figure 2 A schematic diagram of a microwave device provided in an embodiment of this application; Figure 3 A schematic diagram of a tuning unit provided in an embodiment of this application; Figure 4 A partial physical diagram of a tuning unit provided in an embodiment of this application; Figure 5 This is a cross-sectional schematic diagram of a microstrip line provided in an embodiment of this application. Detailed Implementation

[0023] Exemplary embodiments of the present application will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limiting the embodiments of the present application to those set forth herein. Rather, these exemplary embodiments are provided to make the embodiments of the present application more comprehensive and complete, and to facilitate a full communication of the inventive concept to those skilled in the art. The same reference numerals in the drawings denote the same or similar elements, components, or parts, and therefore repeated descriptions of them are omitted. The terms “and / or” or “and / or” include any and all combinations of any one or more of the associated listed items.

[0024] Subject to the technical concept of the embodiments of this application, the features, structures, characteristics or other details described in a particular embodiment may be combined in one or more other embodiments in a suitable manner.

[0025] In the description of specific embodiments, the features, structures, characteristics, or other details described in this application are intended to enable those skilled in the art to fully understand the embodiments. However, it is not excluded that those skilled in the art can practice the technical solutions of the embodiments of this application without one or more specific features, structures, characteristics, or other details.

[0026] The microwave impedance adjustment circuit and microwave device provided in the embodiments of this application will be described below with reference to the accompanying drawings.

[0027] This application provides a microwave device for defrosting food, which includes a microwave impedance adjustment circuit as provided in this application. The microwave device includes the microwave impedance adjustment circuit, an antenna unit, and a cavity. The microwave impedance adjustment circuit includes a control unit and a tuning unit connected to the control unit. The tuning unit includes at least three microstrip lines of different lengths, each microstrip line having a corresponding switch for controlling the on / off state of the microstrip lines. In some embodiments, the microwave impedance adjustment circuit may further include a signal source for generating microwave signals, an RF amplifier connected to the signal source and the control unit for power amplification and output to the antenna unit, and a power detection circuit connected to the RF amplifier and the tuning unit for detecting the RF amplifier power and feeding the detection result back to the control unit. The control unit can control the on / off state of the switches based on the detection result.

[0028] The following is combined Figure 1 and Figure 2 The microwave impedance adjustment circuit and microwave device provided in this application are described below. See also... Figure 1 The microwave impedance adjustment circuit includes a control unit 10 and a tuning unit 50, the tuning unit 50 being connected to the antenna unit 60. The microwave impedance circuit may further include a signal source 20, an RF amplifier 30, and a power detection circuit 40. See also... Figure 2 The microwave device includes a microwave impedance adjustment circuit and further comprises an antenna unit 60 and a cavity 100. The control unit 10 can also be connected to the signal source 20, the radio frequency amplifier 30, and the power detection circuit 40. The signal source 20 is a module that generates microwave signals, such as a 40.68MHz signal; depending on the actual needs of the microwave device, the signal source 20 can also generate signals of other frequencies. The microwave signal generated by the signal source 20 is amplified by the radio frequency amplifier 30 and then output to the antenna unit 60. The antenna unit 60 transmits the processed microwave signal to the cavity 100, thereby heating food or other objects within the cavity 100. A power detection circuit 40 and a tuning unit 50 are also provided between the radio frequency amplifier 30 and the antenna unit 60 for detecting the power of the microwave device and adjusting its impedance. The specific detection and adjustment methods will be further explained below.

[0029] See Figure 1 In the microwave impedance adjustment circuit, the tuning unit 50 is connected to the control unit 10 and also to the antenna unit 60. It includes at least three microstrip lines of different lengths, and each microstrip line of different lengths is equipped with a corresponding switch. Figure 1 As shown, the tuning unit includes microstrip lines M1~n and switches S1~n, i.e., microstrip lines M1 and S1, M2 and S2, and so on up to microstrip lines Mn and Sn. Each switch controls the on / off state of its corresponding microstrip line. The control unit 10 controls the overall on / off state of the switches, thereby controlling the tuning unit and adjusting the microwave impedance. Specifically, the control unit 10 can control the on / off state of any single switch, meaning the on / off states of each switch are independent. Thus, by controlling the on / off state of each switch, the control unit 10 can achieve different combinations of microstrip lines. It is understood that the length of the microstrip line mentioned in the embodiments of this application refers to the electrical length achieved by the microstrip line.

[0030] Furthermore, such as Figure 3 As shown, the aforementioned microstrip lines are connected in series. This series connection allows for the superposition of microstrip line lengths. For each microstrip line segment, the corresponding switch is connected in parallel. When the switch is closed, the microstrip line segment is short-circuited and does not participate in operation; when the switch is open, the microstrip line segment is connected to the circuit and participates in operation.

[0031] These multiple microstrip lines can have the same length, such as each microstrip line having a length of L0. By setting up multiple microstrip lines, a binary microstrip line length adjustment method can be formed, where each switch represents a 0 or 1 bit in binary; when the switch is open, the length of that microstrip line is 1, and when the switch is closed, the length of that microstrip line is 0. Taking four microstrip lines of equal length as an example, the control unit can select a specific microstrip line combination using different values ​​from 0000 to 1111, and then judge the impedance matching result in real time by combining forward and reverse power, and determine whether the microstrip line combination needs adjustment based on the matching result; if further adjustment is needed to obtain better impedance adjustment, the control unit will change the microstrip line combination using the aforementioned binary method and judge the impedance matching result again. In the adjustment method, the control unit can further accelerate the adjustment speed through a combination of coarse and fine adjustments. Through feedback adjustment, the control unit can quickly determine the optimal combination in the matching network of different microstrip line combinations, thereby achieving precise and rapid impedance adjustment to the optimal linear state.

[0032] In other embodiments, the multiple microstrip lines may also have different lengths. For example, the microstrip lines may be in different length groups, with microstrip lines within each group having the same length, while the microstrip lines between different groups have different lengths. Exemplarily, the microstrip lines between different groups may have a multiple-length relationship. This arrangement, by providing groups of microstrip lines of different lengths, effectively expands the overall length adjustment range based on the adjustment method of equal-length microstrip lines, enabling both precise adjustment of microwave impedance and a wider adjustment range.

[0033] By setting up the aforementioned multi-segment microstrip line and corresponding switch tuning unit, the microwave impedance adjustment circuit and microwave device provided in this application can quickly and accurately adjust the length of the microstrip line to adjust the impedance to match the appropriate power, thereby achieving a better defrosting effect.

[0034] In microwave devices, the microstrip lines of microwave impedance adjustment circuits are formed by multiple switches controlling the on / off state of a single microstrip line mounted on a circuit board. Specifically, the single microstrip line is formed on the circuit board, and switches are positioned at specific locations along the microstrip line to cut and control its on / off state, while simultaneously connecting multiple microstrip lines in series. Thus, the tuning unit of the microwave impedance adjustment circuit provided in this application only requires conventional circuit boards and microstrip lines. By arranging the switches, the aforementioned combination of multiple microstrip lines is achieved, effectively reducing the number of components used, lowering equipment costs, and achieving efficient adjustment. For example, see... Figure 4 The figure shows a partial view of a tuning unit according to an embodiment of this application, illustrating microstrip lines M1', M2', and M3'. The tuning unit includes these three microstrip lines and may also have more microstrip line structures. These microstrip lines are connected in series and correspondingly equipped with switches (not shown in the figure).

[0035] In some embodiments, at least one segment of the microstrip lines has a meandering structure with reciprocating folds, such as... Figure 4 Microstrip lines M1', M2', and M3' in the circuit all have this structure. In microwave impedance adjustment circuits, only some microstrip lines may have this structure, while the rest may be straight lines, broken lines, or other structures. In other embodiments, at least one segment of these microstrip lines is at least partially surrounded by another segment of microstrip line; for example, one microstrip line is surrounded by another segment of microstrip line. The microstrip line is surrounded by a folded, meandering structure. It is understood that at least one segment of the microstrip line can simultaneously possess the aforementioned reciprocating folded, meandering structure and be at least partially surrounded by another segment of the microstrip line. Further, in some embodiments, these microstrip lines may also have an entirely enclosed area on the circuit board. Figure 4As shown, microstrip lines M1', M2', and M3' are adjacent and have a meandering, folded structure, forming a closed region. Based on any of the aforementioned microstrip line configurations, the microstrip line structure on the circuit board can be made more compact, effectively achieving microstrip line integration, improving overall circuit integration, and further reducing costs.

[0036] In some embodiments, at least one segment of the microstrip lines is simultaneously disposed on both sides of the circuit board. Further, multiple segments of the microstrip lines in the tuning unit 50 are disposed on both sides of the circuit board. Further, see... Figure 5 At least one section of the microstrip line's conductor includes a first metal layer 210 and a second metal layer 220 respectively disposed on both sides of the circuit board. The first metal layer 210 and the second metal layer 220 have the same orientation, that is, they correspond to each other in the thickness direction of the circuit board; the dielectric layer 230 of the circuit board is between them. The first metal layer 210 and the second metal layer 220 are electrically connected through metallized vias 240 arranged in an array along their extension direction, so that the first metal layer 210, the second metal layer 220, and the metallized vias 240 together constitute the conductor of this section of the microstrip line. For example, see Figure 4 The diagram illustrates the metallized via structure on the microstrip line. It is understood that the number and spacing of the arrayed metallized vias on the microstrip line can be set according to the actual microstrip line structure design and / or electrical performance requirements. This microstrip line structure with double-sided metal layers and arrayed metallized vias can optimize the RF signal transmission performance of the microstrip line, increase transmit power, reduce microstrip line loss, and improve overall system efficiency.

[0037] The microwave impedance adjustment circuit provided in this embodiment further includes a signal source 20, an RF amplifier 30, and a power detection circuit 40, all of which are connected to the control unit 10. As mentioned above, the signal source 20 generates a microwave signal, which is amplified by the RF amplifier 30; the power detection circuit 40 detects the power of the RF amplifier 30 and feeds the detection result back to the control unit 10, which then controls the switching on and off based on the detection result.

[0038] Specifically, the control unit 10 performs calculations based on the detection results fed back from the power detection circuit 40 to confirm the matching status of the RF amplifier 30 and the antenna unit 60. When the two are mismatched and the circuit impedance needs to be adjusted, the control unit 10 adjusts the on / off state of the switch and re-confirms the matching based on the detection results fed back from the power detection circuit 40 until the matching is complete. Because the switch adjustment response is rapid, the control unit 10 can quickly and accurately adjust the circuit impedance through this feedback adjustment method, which can significantly reduce the adjustment time compared to the existing capacitor or inductor adjustment methods.

[0039] As mentioned earlier, the multiple microstrip lines in the tuning unit 10 can have equal lengths, and the binary length can be adjusted by switching different switches on and off. In actual adjustment, the control unit 10 achieves rapid control adjustment through a combination of coarse and fine adjustments. Specifically, a certain length can be selected first to observe the detection result fed back by the power detection circuit 40. If the detection result is mismatched, the control unit 10 increases or decreases the number of bits in the binary length according to the actual situation, i.e., doubling the length or halving the length, to continue observing the matching result. If further increase or decrease is still needed, the above adjustment is repeated. If the adjusted length deviates from the matching adjustment direction, it indicates that the actual required length is within the range of doubling or halving the length. At this point, the final matching length can be gradually approached within the above range by adjusting a smaller number of bits in the binary length. Through this combination of coarse and fine adjustments and the control of the binary microstrip line length switch, the control unit 10 can quickly adjust to the desired impedance, significantly reducing the adjustment time and achieving high adjustment accuracy.

[0040] The tuning unit 10 can also have multiple sets of microstrip lines of different lengths, with the microstrip lines in each set having the same length. In this case, the control of the microstrip lines in each set is as described above, while the different sets of microstrip lines provide a wider range of selectable lengths, thereby providing a higher impedance dynamic range and further improving the tuning capability.

[0041] In some implementations, the power detection circuit 40 is used to detect the forward and reverse power of the RF amplifier 30. The control unit 10 uses this forward and reverse power to determine the matching status between the RF amplifier 30 and the antenna unit 60. Specifically, the control unit 10 calculates the standing wave ratio (SWR) based on the forward and reverse power; a lower SWR indicates a better matching effect. If the SWR does not reach a preset threshold, the control unit 10 will quickly adjust the impedance using the tuning unit based on the aforementioned adjustment method. Therefore, when food to be defrosted or heated is placed in the cavity 100, the microwave impedance adjustment circuit can quickly adjust the impedance based on the reverse power of the food and the forward power of the RF amplifier, achieving better defrosting and heating energy and a shorter defrosting and heating time.

[0042] In some embodiments, the microwave impedance adjustment circuit further includes a matching unit connected between the power detection unit 40 and the tuning unit 50, used for matching the antenna unit and the RF amplifier. The matching unit uses microstrip lines or capacitors and inductors, connected in parallel or series to the RF path, to achieve a better matching state between the antenna unit and the RF amplifier.

[0043] The microwave impedance adjustment circuit and microwave device provided in this application embodiment achieve precise adjustment of the microstrip line length by setting multiple microstrip lines, replacing the inductor-capacitor adjustment method in the prior art. This effectively solves the problems of low adjustment accuracy and long adjustment time caused by the errors and time delays of inductors and capacitors. At the same time, multiple microstrip lines can be integrated on a PCB board, which can further reduce costs.

[0044] Other embodiments of the present application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the disclosure herein. The embodiments of the present application are intended to cover any variations, uses, or adaptations of the embodiments of the present application that follow the general principles of the embodiments of the present application and include common knowledge or customary technical means in the art not disclosed in the embodiments of the present application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of the present application should be included within the scope of the claims of the embodiments of the present application.

Claims

1. A microwave impedance adjustment circuit, characterized in that, include: The control unit and the tuning unit connected to the control unit, the tuning unit including at least three microstrip lines of different lengths, each microstrip line of different lengths being provided with a switch, the switch being used to control the on and off of the microstrip line; The control unit is used to control the on / off state of the plurality of switches to adjust the antenna unit, and the tuning unit is also used to connect the antenna unit.

2. The microwave impedance adjustment circuit according to claim 1, characterized in that, The microstrip lines are connected in series.

3. The microwave impedance adjustment circuit according to claim 2, characterized in that, Each of the switches is connected in parallel to the corresponding microstrip line, and the microstrip line is short-circuited when the switch is closed.

4. The microwave impedance adjustment circuit according to claim 3, characterized in that, The multiple segments of the microstrip line are formed by switching a complete microstrip line disposed on a circuit board on and off through the multiple switches.

5. The microwave impedance adjustment circuit according to claim 3, characterized in that, The multiple microstrip lines have the same length.

6. The microwave impedance adjustment circuit according to claim 3, characterized in that, The multi-strip microstrip line has multiple groups of different lengths, wherein the microstrip lines in each group are of the same length, and the lengths of the microstrip lines in different groups are different.

7. The microwave impedance adjustment circuit according to claim 2, characterized in that, At least one segment of the microstrip line has a meandering structure with reciprocating folds.

8. The microwave impedance adjustment circuit according to claim 7, characterized in that, At least one segment of the microstrip line is at least partially surrounded by another segment of the microstrip line.

9. The microwave impedance adjustment circuit according to any one of claims 1-8, characterized in that, At least one section of the microstrip line is simultaneously disposed on both sides of the circuit board.

10. The microwave impedance adjustment circuit according to claim 9, characterized in that, The multiple microstrip lines of the tuning unit are all disposed on both sides of the circuit board.

11. The microwave impedance adjustment circuit according to claim 9, characterized in that, At least one section of the microstrip line includes a first metal layer disposed on one side surface of the circuit board and a second metal layer disposed on the other side surface of the circuit board; The first metal layer and the second metal layer have the same orientation, and the first metal layer and the second metal layer are electrically connected by metallized vias arranged in an array along their extension direction.

12. The microwave impedance adjustment circuit according to claim 9, characterized in that, The microwave impedance adjustment circuit further includes: A signal source, used to generate microwave signals; A radio frequency amplifier, connected to the signal source and control unit, is used to amplify power and output it to the antenna. A power detection circuit, connected to the RF amplifier and the tuning unit, is used to detect the power of the RF amplifier and feed the detection result back to the control unit; The control unit controls the switching on and off based on the detection results.

13. The microwave impedance adjustment circuit according to claim 12, characterized in that, The power detection circuit is used to detect the forward power and reverse power of the RF amplifier, and the control unit determines the matching status of the RF amplifier and the antenna unit based on the forward power and reverse power.

14. The microwave impedance adjustment circuit according to claim 12, characterized in that, The microwave impedance adjustment circuit further includes a matching unit connected to the power detection circuit and the tuning unit, used for matching the antenna unit and the RF amplifier.

15. A microwave device for defrosting food, characterized in that, It includes an antenna unit, a cavity, and a microwave impedance adjustment circuit as described in any one of claims 1-14.

Images