LC oscillator and switching circuit and regulation control method thereof

Abstract

The invention relates to an LC oscillator and a switch circuit and an adjustment control method thereof, and the switch circuit of the LC oscillator comprises two groups of switch arrays. Each group of switch array comprises a plurality of second variable capacitors which are connected in parallel, the output end of each second variable capacitor in one group of switch array is connected with a first output node of the resonant cavity, and the output end of each second variable capacitor in the other group of switch array is connected with a second output node of the resonant cavity; and in any group of switch arrays, the sizes of the second variable capacitors are in a multiplication relationship, the size of the smallest second variable capacitor is a target multiple of the size of the first variable capacitor, the target multiple is smaller than 1, and according to the sequence of the sizes from small to large, the control ends of the second variable capacitors are sequentially connected to the low-order control word to the high-order control word. A metal capacitor in a traditional switch array is replaced by the variable capacitor, and the problem that the performance of an existing LC oscillator switch capacitor array is not ideal is solved.

Description

Technical Field

[0001] The present application relates to the field of oscillators, and in particular to an LC oscillator and a switching circuit and a regulation control method thereof. Background Art

[0002] The oscillator is the core module in modern communication systems, used to provide accurate local oscillator signals. Its phase noise performance affects the sensitivity and bit error rate of the communication system, restricting the performance of the system. Therefore, LC oscillators with superior noise performance have been more widely used. On the other hand, in order to support multi-mode communication systems and higher data rates, oscillators also need to be able to cover a sufficiently wide frequency range.

[0003] Reference Figure 1 , a conventional LC oscillator connects a variable capacitor (Varactor) in the resonant cavity (composed of two capacitors L1 and MOS tubes M1 and M2); changing the voltage V on one plate of the variable capacitor cont The capacitance value presented by the Varactor to the resonant cavity can be changed, thereby changing the oscillation frequency of the oscillator. In order to achieve wide frequency coverage, the size of the Varactor, especially the length, needs to be increased; however, the quality factor (Q value) of a larger Varactor will be lower, thereby lowering the Q value of the resonant cavity and worsening the phase noise performance.

[0004] Reference Figure 2 , the current LC oscillator design often introduces a switched capacitor array, that is, by using the digital control of the switch to connect the capacitor size of the resonant cavity, with a Varactor of appropriate size, to achieve the purpose of wide frequency coverage. Metal capacitors with higher Q values, such as MIM capacitors or MOM capacitors, are usually used in the switched capacitor array to avoid lowering the overall Q value of the resonant cavity. Since the switching transistor will present a certain on-resistance when closed, the introduction of the switched capacitor will inevitably reduce the Q value of the resonant cavity. Although the use of transistors with a larger width-to-length ratio can reduce the on-resistance, it will increase the area consumption of the circuit and increase the parasitic capacitance Cp when the switch is turned off, so that the capacitance change presented to the resonant cavity is reduced (from the metal capacitor Cu to Cu-Cu / / Cp), resulting in a reduction in the tuning range. Therefore, the performance of the current LC oscillator switched capacitor array is not ideal.

[0005] Currently, no effective solution has been proposed to solve the problem of unsatisfactory performance of LC oscillator switched capacitor arrays. Summary of the invention

[0006] The present invention provides an LC oscillator and a switch circuit and an adjustment control method thereof to solve the problem of unsatisfactory performance of the LC oscillator switch capacitor array.

[0007] In a first aspect, the present invention provides a switching circuit of an LC oscillator, wherein the LC oscillator further comprises a resonant cavity, the switching circuit is used to control the oscillation frequency of the LC oscillator by controlling the capacitance value of the resonant cavity, and a first output node and a second output node of the resonant cavity are both connected to a first variable capacitor; The switch circuit includes two sets of switch arrays; Each switch array group includes a plurality of second variable capacitors connected in parallel, wherein the output end of each second variable capacitor in one switch array group is connected to the first output node of the resonant cavity, and the output end of each second variable capacitor in another switch array group is connected to the second output node of the resonant cavity; In any group of switch arrays, the sizes of the second variable capacitors are in a multiplying relationship and the size of the smallest second variable capacitor is a target multiple of the size of the first variable capacitor, the target multiple is less than 1, and in order of size from small to large, the control ends of the second variable capacitors are connected to the low-order control word to the high-order control word in sequence.

[0008] In a second aspect, the present invention provides an LC oscillator, comprising a resonant cavity and a switching circuit, wherein the switching circuit is used to control the oscillation frequency of the LC oscillator by controlling the capacitance value of the resonant cavity, wherein the first output node and the second output node of the resonant cavity are both connected to a first variable capacitor, and the switching circuit is the switching circuit of the LC oscillator described in the first aspect.

[0009] In a third aspect, the present invention provides a method for regulating and controlling an LC oscillator, wherein the LC oscillator is the LC oscillator described in the second aspect, and the method for regulating and controlling comprises: The oscillation frequency of the LC oscillator is controlled by controlling the capacitance value of the resonant cavity through a switching circuit.

[0010] Compared with the related art, the present invention uses variable capacitors to replace metal capacitors in the traditional switch array, which can not only reduce the capacitance noise of the resonant cavity and improve the Q value of the resonant cavity, but also reduce the area occupied by the switch circuit. Therefore, a switch capacitor array with better performance is provided, which solves the problem of unsatisfactory performance of the current LC oscillator switch capacitor array.

[0011] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the resonant cavity structure of the LC oscillator in the prior art; Figure 2 It is an LC oscillator structure in the prior art; Figure 3It is another LC oscillator structure in the prior art; Figure 4 The LC oscillator structure provided by the present invention; Figure 5 The filter circuit structure provided by the present invention; Figure 6 It is an equivalent circuit of the filter circuit structure provided by the present invention. DETAILED DESCRIPTION

[0013] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0014] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the general meaning understood by people with general skills in the technical field to which this application belongs. The words "one", "a", "the", "these" and the like in this application do not indicate a quantitative limitation, and they may be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this application are intended to cover non-exclusive inclusions; for example, a process, method and system, product or device comprising a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" may mean: A exists alone, A and B exist at the same time, and B exists alone. Generally, the character " / " indicates that the objects associated with each other are in an "or" relationship. The terms "first", "second", "third", etc. in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0015] In order to solve the problem of unsatisfactory performance of the current LC oscillator switched capacitor array, some technical solutions have been proposed in the prior art, but these technical solutions still have the problem of obviously unsatisfactory performance.

[0016] Reference Figure 3 The left side of the figure shows a switch transistor using a differential structure (the right side of the figure shows the equivalent model when the switch is turned off, R on1 , R on2 and R on3are the off resistances of transistors S1, S2, and S3, respectively), which can further halve the on resistance of switches of the same size, thereby improving the Q value of the switch capacitor lineup, where transistors S2 and S3 are used to provide the DC levels of points A and B in the on state.

[0017] With the advancement of technology and the further increase in the demand for tuning range, the above Figure 3 The existing solutions shown also have the following shortcomings: (1) Due to the on-resistance of the switching transistor S1 and its gate-source voltage V GS In an inversely proportional relationship, in advanced processes or low-voltage designs, the on-resistance of the switching transistor increases greatly, significantly reducing the Q value of the switching capacitor array, resulting in a reduction in the oscillator phase noise.

[0018] (2) In order to reduce the parasitic capacitance of the transistor, Figure 3 In the structure shown, S2 and S3 are usually transistors of the smallest size, and the switch transistor also usually uses the smallest trench length under the process. However, this will inevitably increase the contribution of flicker noise and deteriorate 1 / f 3 Regional phase noise is particularly significant under advanced processes.

[0019] (3) In order to ensure continuous frequency coverage under process and temperature changes, the unit capacitance Cu in the capacitor array usually needs to be about 30% smaller than the capacitance range (Cmax-Cmin) provided by the selected Varactor - obviously, under the same target tuning range, this means more arrays and worse noise performance.

[0020] Therefore, the prior art still has the problem of unsatisfactory performance of the LC oscillator switched capacitor array.

[0021] Based on this, in an embodiment of the present invention, a switching circuit of an LC oscillator is provided, the LC oscillator also includes a resonant cavity, the switching circuit is used to control the oscillation frequency of the LC oscillator by controlling the capacitance value of the resonant cavity, and the first output node and the second output node of the resonant cavity are both connected to a first variable capacitor.

[0022] Generally, an LC oscillator includes a resonant cavity and a switch circuit. The present invention is an improvement on the switch circuit. The circuit structure of the resonant cavity (including the first variable capacitor) is an existing mature structure. Figure 1 , the present invention will not be described in detail, the first output node and the second output node are respectively Figure 1 The X and Y nodes in .

[0023] Reference Figure 4The switch circuit includes two groups of switch arrays; each group of switch arrays includes a plurality of second variable capacitors connected in parallel, wherein the output end of each second variable capacitor in one group of switch arrays is connected to the first output node of the resonant cavity, and the output end of each second variable capacitor in the other group of switch arrays is connected to the second output node of the resonant cavity; in any group of switch arrays, the sizes of each second variable capacitor are in a multiplication relationship and the size of the smallest second variable capacitor is a target multiple of the size of the first variable capacitor, the target multiple is less than 1, and in order of size from small to large, the control end of each second variable capacitor is connected to the low-order control word to the high-order control word in sequence.

[0024] For example, the size of each second variable capacitor is in a doubling relationship, which means that the size of the next second variable capacitor is twice the size of the previous second variable capacitor. Correspondingly, in order of size from small to large, the control end of each second variable capacitor is connected to the low to high bits of the multi-bit control word in sequence. For example, assuming that the switch array is composed of three second variable capacitors in parallel and the size of the first second variable capacitor is 1 and there is a three-bit control word, then the control end of the first second variable capacitor is connected to the lowest bit of the control word, the size of the second second variable capacitor is 2, and its control end is connected to the middle bit of the control word, and the size of the third second variable capacitor is 4, and its control end is connected to the highest bit of the control word.

[0025] and Figure 2 Compared with the prior art in the prior art, the present invention uses a variable capacitor to replace the metal capacitor to provide capacitance for the resonant cavity. As mentioned above, a switching device is needed to control whether each metal capacitor provides a capacitance value for the resonant cavity. When a certain switching device is closed, the metal capacitor connected in series with it will provide a capacitance value for the resonant cavity. On the one hand, there is resistance when the switching device is closed, and the presence of this resistance will reduce the Q value of the resonant cavity. On the other hand, there is parasitic capacitance when the switching device is disconnected, which reduces the capacitance value that a single metal capacitor can provide for the resonant cavity, which will reduce the tuning range of the resonant cavity and increase the capacitance noise of the resonant cavity, or more metal capacitors need to be set while ensuring the same tuning range, thereby increasing the circuit area and layout difficulty. Thirdly, due to the existence of parasitic capacitance and the difficulty in accurately measuring parasitic capacitance, the difference between the actual capacitance value of a single metal capacitor and the ideal capacitance value (capacitance marking value) is difficult to measure; at the same time, due to the process differences between metal capacitors and variable capacitors (there may be a situation where the capacitance marking value is the same but the actual capacitance value is significantly different), in order to ensure the continuous frequency coverage of the resonant cavity (the actual capacitance value of the metal capacitor must be less than the maximum actual capacitance value of the variable capacitor), it is usually necessary to set the capacitance marking value of the metal capacitor to be less than 30% of the maximum capacitance marking value of the variable capacitor. Therefore, more metal capacitors need to be set within the same tuning range, which increases the circuit area and layout difficulty.

[0026] The present invention uses a variable capacitor to provide a capacitance value for the resonant cavity. On the one hand, the variable capacitor does not have parasitic capacitance and resistance, and its actual capacitance value is basically the same as the capacitance annotation value, so basically no capacitance noise is generated and the Q value of the resonant cavity is reduced. On the other hand, the process error between capacitors of the same type is extremely small, that is, the process error between the first variable capacitor and the second variable capacitor is extremely small. It can be basically considered that when the maximum capacitance annotation values ​​of the two are the same, the actual maximum capacitance values ​​of the two are the same. In order to ensure the continuous frequency coverage of the resonant cavity, the maximum capacitance annotation value of the first variable capacitor is set to be slightly smaller than the maximum capacitance annotation value of the second variable capacitor (for example, reduced by 20% or 10% or even lower, significantly less than 30% in the prior art), and there is no need to provide too much design margin, thereby reducing the number of columns of the switch array and reducing the area occupied by the switch circuit.

[0027] In some preferred embodiments, the target multiple is between 0.8 and 0.95. The maximum capacitance value of the variable capacitor is positively correlated with its own size. The target multiple determines the maximum capacitance ratio between the first variable capacitor and the second variable capacitor. As mentioned above, the process differences of the same type of capacitors are very small, and the maximum capacitance values ​​of variable capacitors of the same size are basically the same. Even considering certain errors, the target multiple can be set to be close to 1. Preferably, when the target multiple is between 0.8 and 0.95, it can be ensured that the actual value of the maximum capacitance of the second variable capacitor is less than the actual value of the maximum capacitance of the first variable capacitor, while ensuring a smaller design margin and minimizing the area occupied by the switching circuit.

[0028] In one embodiment, the target multiple is 0.8, and the multiple ratio of the second variable capacitor to the first variable capacitor is 0.8. For example, the multiple of the first variable capacitor is 5, and the multiple of the second variable capacitor is 4. Or, the multiple of the first variable capacitor is 10, and the multiple of the second variable capacitor is 8. This embodiment can further ensure matching and simplify the difficulty of drawing the layout. In other embodiments, the multiple ratio of the two variable capacitors meets the target multiple.

[0029] In some embodiments, the number of second variable capacitors in each switch array is four, each second variable capacitor corresponds to one control word, and four second variable capacitors can support a four-bit control word.

[0030] In summary, the present invention uses variable capacitors to replace metal capacitors in traditional switch arrays, which can not only reduce the capacitance noise of the resonant cavity and improve the Q value of the resonant cavity, but also reduce the area occupied by the switch circuit. Therefore, a switch capacitor array with better performance is provided, which solves the problem of unsatisfactory performance of the current LC oscillator switch capacitor array.

[0031] Reference Figure 5In some embodiments, each second variable capacitor is connected to its own control word through a low-pass filter. The control word is essentially a control signal. The capacitance value of the variable capacitor can be continuously changed, which is related to the size of its own control signal. In the present invention, the second variable capacitor is used slightly differently from the first variable capacitor. For the first variable capacitor, it is necessary to utilize the characteristic that its capacitance value can be continuously changed, and through the continuously changing control signal, the capacitance value provided by the first variable capacitor to the resonant cavity is controlled to achieve continuous change. For the second variable capacitor, it is necessary to use it as a switching device, and the capacitance value provided by each second variable capacitor to the resonant cavity is 0 or its own maximum capacitance value. This use method is different from the traditional use method of the variable capacitor. In this use method, it is necessary to focus on the control signal noise of the second variable capacitor. Due to the existence of noise, the second variable capacitor cannot accurately provide its own maximum capacitance value for the resonant cavity. In particular, the second variable capacitor controlled by the high-order control word, because the maximum capacitance value of these second variable capacitors is larger, can thus produce a larger capacitance value error. In summary, low-pass filtering the control word of the second variable capacitor can further improve the Q value of the resonant cavity, and since the capacitance error provided by the second variable capacitor to the resonant cavity is reduced, the design margin can be further reduced, that is, the value of the target multiple can be closer to 1.

[0032] It should be noted that in the traditional switching circuit, the transistor used as a switch is a two-state device, which is either on or off, so that the control signal noise is basically not introduced into the resonant cavity. Therefore, when facing the traditional switching circuit, those skilled in the art basically do not pay attention to the control signal noise. However, after the present invention uses a variable capacitor to replace the metal capacitor in the traditional switching circuit, it is not limited by the habitual thinking in this field, but pays keen attention to the control signal noise, and accordingly uses a low-pass filter to denoise the control signal.

[0033] Furthermore, the control signal noise comes from the previous inverter. Specifically, since the control signal usually comes from the previous inverter, no matter the output voltage is low or high, there will be a transistor in the inverter that is turned on; similar to the switch transistor in the traditional design, the limited on-resistance of the transistor here causes thermal noise and flicker noise.

[0034] Furthermore, the low-pass filter can adopt different circuit structures. Figure 5 and Figure 6 Exemplarily, the low-pass filter includes an NMOS tube, a PMOS tube and a MOS capacitor; the source and drain of the NMOS tube (the gate is connected to the power supply) and the PMOS tube (the gate is grounded) are cross-connected to form a resistance part, a first end of the resistance part is connected to the output end of the inverter, and the input end of the inverter is used to access the control word, and the other end of the resistance part is grounded through the MOS capacitor and connected to the control end of the second variable capacitor. Figure 6 is the equivalent circuit diagram of the above low-pass filter.

[0035] Among them, multiple inverters output multi-bit control words respectively, and the output end of each inverter is connected to the control end of the corresponding second variable capacitor through a low-pass filter. The transistor acting as the resistance part includes both N-type MOS tube and P-type MOS tube to avoid threshold loss; the N-type transistor acting as the resistance part uses a larger channel length to reduce flicker noise. At the same time, MOS capacitors with higher capacitance density are used as filter capacitors in the low-pass filter, and it is recommended to use MOS capacitors and metal capacitors at the same time to realize the filter capacitors in this low-pass filter to further save chip area.

[0036] The above is the switching circuit of the LC oscillator provided by the present invention.

[0037] In an embodiment of the present invention, an LC oscillator is also provided, including a resonant cavity and a switching circuit, the switching circuit is used to control the oscillation frequency of the LC oscillator by controlling the capacitance value of the resonant cavity, the first output node and the second output node of the resonant cavity are both connected to a first variable capacitor, and the switching circuit is the switching circuit of the LC oscillator provided by the present invention.

[0038] By applying the switch circuit provided by the present invention to the existing resonant cavity structure, a new LC oscillator can be obtained.

[0039] In some of the embodiments, the LC oscillator is applied in a low power supply voltage scenario.

[0040] From the above introduction to the switching circuit of the LC oscillator, it can be seen that the present invention can effectively reduce the noise introduced into the resonant cavity. It should be noted that in low power supply voltage scenarios and advanced process scenarios, the noise is more obvious, and thus noise removal is of greater significance. The LC oscillator and its switching circuit provided by the present invention are mainly used in low power supply voltage scenarios or advanced process scenarios.

[0041] In an embodiment of the present invention, a method for adjusting and controlling an LC oscillator is further provided. The LC oscillator is the LC oscillator provided by the present invention. The method for adjusting and controlling includes: The capacitance value of the resonant cavity is controlled by the switch circuit to control the oscillation frequency of the LC oscillator. Specifically, by adjusting the multi-bit control word of the switch circuit, the capacitance value of the resonant cavity can be controlled to control the oscillation frequency of the LC oscillator.

[0042] As follows, the oscillator and the switching circuit thereof in the present invention are described through a specific embodiment.

[0043] Taking 4-bit array tuning as an example, the low-voltage LC oscillation based on the variable capacitor array implemented by the present invention is as follows: Figure 4As shown in the figure, the oscillator core is the same as the traditional design, consisting of an inductor, fixed and parasitic capacitors, a differential coupling tube, and a tail current source; the control voltage V cont The controlled Varactor and the proposed variable capacitor array together constitute a frequency tuning unit. The working principle of the overall structure and the working principle of the proposed part are as follows: The inductance L and the sum of all types of capacitance in the circuit C tot (Including fixed load capacitance C L , variable capacitor C Var 、Array capacitance C B And the parasitic capacitance C P ) together form a resonant cavity, at a frequency of 1 / 2π (LC tot ) 1 / 2 A pair of conjugate poles are presented at , which means that the circuit will oscillate at this frequency after power-on; the cross-coupling of the tube and the tail current source I ss It presents an AC negative resistance to offset the parasitic resistance in the resonant cavity and maintain the circuit's equal amplitude oscillation. It is not uncommon to see that by changing C tot By changing the control voltage, C Var or by changing the digital control to change C B The value of can change the oscillation frequency.

[0044] like Figure 4 As shown, in the design of the unit capacitor of the capacitor array, the present invention uses a variable capacitor to replace the metal capacitor in the traditional design, so that: (1) Simplifies the design difficulty of frequency coverage: According to the application scenario of this LC oscillator (such as the K required by the specific design of the phase-locked loop), VCO ) After determining the size of the variable capacitor Varactor, simply select a Varactor with 0.8 times the size as the unit capacitor of the switched capacitor array. Obviously, this design ensures a good matching relationship between the continuous tuning based on the Varactor and the discrete tuning based on the switched capacitor - if the control voltage V cont The change from 0 to VDD introduces a DC change to the resonant cavity, and the control word increases by 1, which causes the switch capacitor array to introduce a 0.8 times DC change to the resonant cavity (this change needs to be less than or equal to DC). There must be an overlap between two adjacent tuning curves (for example, there is an overlap between the 0 to DC and 0.8DC to 1.8DC curves, 0.8DC to DC). In conventional metal capacitor-based designs, careful simulation is required to select the size of the metal capacitor and the switch tube in order to reduce area overhead while ensuring frequency coverage.

[0045] In the design of the present invention, it is recommended to achieve the above-mentioned multiple of 0.8 by selecting the multiplier of the Varactor to be 5 and the multiplier of the unit switch capacitor to be 4. Such values ​​further ensure matching and simplify the difficulty of drawing the layout.

[0046] (2) Avoiding the use of switching transistors: Since variable capacitors are used as the basic unit of the switch array, the capacitance "seen" by the resonant cavity can be changed by changing the voltage applied to the control plate, and there is no need to use a turned-on transistor to connect the capacitor to the resonant cavity. In this way, the related problems caused by the on-resistance or parasitic capacitance of the transistor can be avoided.

[0047] like Figure 5 As shown in the figure, before the digital control voltage is applied to the variable capacitor in the capacitor array, a low-pass filter is first performed: since the control voltage usually comes from the inverter of the previous stage, and no matter the output voltage is low or high, there will be a transistor in the inverter that is turned on; similar to the switch transistor in the traditional design, the thermal noise and flicker noise corresponding to the limited on-resistance of the transistor here will also enter the resonant cavity through the array capacitor, deteriorating the phase noise of the oscillator. Although it is relatively better than the design of the traditional capacitor array, the noise of the transistor cannot be ignored in the design scenario of low voltage, especially advanced process.

[0048] As shown in the figure, the addition of a transistor-based low-pass filter solves the above problem well: the presence of the filter capacitor will direct most of the noise to the ground, and only present a "clean" control voltage to the capacitors in the array; under the design of advanced technology and low voltage, the impact of flicker noise is even greatly optimized (that is, the 1 / f 3 corner).

[0049] As shown in the figure, the low-pass filter described in the present invention is completely implemented by transistors, wherein the transistors acting as the resistor part include both N-type MOS transistors and P-type MOS transistors to avoid threshold loss; the N-type transistors acting as resistors use a larger channel length to reduce flicker noise.

[0050] As shown in the figure, the present invention uses MOS capacitors with higher capacitance density as filter capacitors in the low-pass filter, and advocates using MOS capacitors and metal capacitors to implement the filter capacitors in the low-pass filter to further save chip area.

[0051] As shown in the figure, the control path of the variable capacitor array proposed in the present invention can use the smallest inverter size, and it is only necessary to appropriately optimize the size of the low-pass filter capacitor in combination with the noise simulation results - the reason is that the high-order control word corresponds to the larger variable capacitor in the array, and the noise up-conversion effect caused by it in the oscillator is more significant, so a deeper noise filtering is required; and correspondingly, the filter capacitor on the smaller variable capacitor path corresponding to the low-order control word can be appropriately reduced to save chip area.

[0052] It should be understood that the specific embodiments described herein are only used to explain the application, rather than to limit it. Based on the embodiments provided in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of this application.

[0053] Obviously, the drawings are only some examples or embodiments of the present application. For ordinary technicians in the field, the present application can also be applied to other similar situations based on these drawings without creative work. In addition, it is understandable that although the work done in this development process may be complicated and lengthy, for ordinary technicians in the field, certain changes in design, manufacturing or production based on the technical content disclosed in this application are only conventional technical means and should not be regarded as insufficient content disclosed in this application.

Claims

1. A switching circuit of an LC oscillator, the LC oscillator further comprising a resonant cavity, the switching circuit being used to control the oscillation frequency of the LC oscillator by controlling the capacitance value of the resonant cavity, wherein a first output node and a second output node of the resonant cavity are both connected to a first variable capacitor; It is characterized in that The switch circuit includes two sets of switch arrays; Each switch array group includes a plurality of second variable capacitors connected in parallel, wherein the output end of each second variable capacitor in one switch array group is connected to the first output node of the resonant cavity, and the output end of each second variable capacitor in another switch array group is connected to the second output node of the resonant cavity; In any group of switch arrays, the sizes of the second variable capacitors are in a multiplying relationship and the size of the smallest second variable capacitor is a target multiple of the size of the first variable capacitor, the target multiple is less than 1, and in order of size from small to large, the control ends of the second variable capacitors are connected to the low-order control word to the high-order control word in sequence.

2. The switching circuit of the LC oscillator according to claim 1, characterized in that: The target multiple is between 0.8-0.

95.

3. The switching circuit of the LC oscillator according to claim 2, characterized in that: The target multiple is 0.8, and the ratio of the multiple of the second variable capacitor to the first variable capacitor is 0.

8.

4. The switching circuit of the LC oscillator according to claim 3, characterized in that: The multiple of the first variable capacitance is 5, and the multiple of the second variable capacitance is 4.

5. The switching circuit of the LC oscillator according to claim 1, characterized in that: Each second variable capacitor is connected to its own control word through a low-pass filter.

6. The switching circuit of the LC oscillator according to claim 1, characterized in that: The number of the second variable capacitors in each switch array is four.

7. The switching circuit of the LC oscillator according to claim 4, characterized in that: The low-pass filter includes NMOS tube, PMOS tube and MOS capacitor; The source and drain of the NMOS tube and the PMOS tube are cross-connected to form a resistance part, a first end of the resistance part is connected to the output end of the inverter, the input end of the inverter is used to access the control word, and the other end of the resistance part is grounded through a MOS capacitor and connected to the control end of the second variable capacitor.

8. An LC oscillator, comprising a resonant cavity and a switch circuit, wherein the switch circuit is used to control the oscillation frequency of the LC oscillator by controlling the capacitance value of the resonant cavity, wherein the first output node and the second output node of the resonant cavity are both connected to a first variable capacitor, wherein: The switching circuit is the switching circuit of the LC oscillator according to any one of claims 1 to 7.

9. The LC oscillator according to claim 8, characterized in that: LC oscillators are used in low power supply voltage scenarios.

10. A method for regulating and controlling an LC oscillator, characterized in that: The LC oscillator is the LC oscillator described in claim 8 or 9, and the adjustment and control method comprises: The oscillation frequency of the LC oscillator is controlled by controlling the capacitance value of the resonant cavity through a switching circuit.

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