LC voltage-controlled generator using nested tail inductor

Abstract

The present invention relates to an LC voltage-controlled generator. An LC voltage-controlled generator, according to an embodiment of the present invention, comprises: a nested tail inductor including a first tail inductor having a figure-of-eight shape to which a supply voltage is applied and a second tail inductor having a figure-of-eight shape to which a ground voltage is applied; and a main inductor which has a space formed therein to surround the nested tail inductor and which is at least partially opened, wherein the first tail inductor and the second tail inductor may be adjacent to each other and nested witheach other in a figure-of-eight shape.

Description

LC voltage-controlled generator using superimposed inductors

[0001] The present invention relates to an LC voltage-controlled generator having low phase noise, a wide frequency tuning range, and a compact silicon area using a nested tail inductor (NTI).

[0002] The growing demand for transceivers employing higher-order modulations necessitates local oscillators (LOs) that offer low phase noise (PN), wide frequency tuning range (FTR), and compact silicon area. To meet these LO requirements, it is crucial to improve phase noise (PN), wide frequency tuning range (FTR), and the area of ​​the voltage-controlled oscillator (VCO), which have the greatest impact on LO performance.

[0003] The purpose of the present invention is to provide an LC voltage control generator capable of preventing interference between inductors while reducing the size of the LC voltage control generator.

[0004] An LC voltage controlled generator according to one embodiment of the present invention for solving the above technical problem includes a superimposed inductor including a first tail inductor in the shape of an 8 connected to a supply voltage and a second tail inductor in the shape of an 8 to which a ground voltage is applied, and a main inductor having a space formed therein to surround the superimposed inductor and at least a portion of which is open, wherein the first inductor and the second inductor can be overlapped in the shape of an 8 adjacent to each other.

[0005] In addition, the direction of the current flowing in the first tail inductor is opposite to the direction of the current flowing in the second tail inductor, and the opposite coupling that strongly occurs between the overlapping inductors due to the currents flowing in different directions in the first tail inductor and the second tail inductor cancels each other, which can eliminate interference to the main inductor.

[0006] Additionally, the main inductor has an oscillation frequency f vco In parallel with the 7-bit coarse tuning capacitor bank and fine tuning capacitor bank, the superimposed inductor is 2f for noise filtering. vco can resonate with the tail capacitor.

[0007] Additionally, the above-described overlapping inductors may share one tail capacitor and one decoupling capacitor connecting the node of the supply voltage and the node of the ground voltage.

[0008] In addition, the first tail inductor and the second tail inductor are adjacent and overlap each other, and the magnetic fields generated in each of the first tail inductor and the second tail inductor can be generated in opposite directions and cancel each other out by currents flowing in opposite directions.

[0009] In addition, as the first tail inductor and the second tail inductor overlap in a figure-8 shape, interference caused by the magnetic field generated from the main inductor can be canceled out through the magnetic field canceling effect of the upper and lower loops.

[0010] According to one embodiment of the present invention described above, an LC voltage control generator can be provided that can prevent interference between inductors while reducing the size of the LC voltage control generator.

[0011] Figure 1 is a diagram illustrating a conventional LC-VCO.

[0012] FIG. 2 is a diagram illustrating an example of area reduction through an LC voltage control generator according to one embodiment of the present invention.

[0013] FIG. 3 is a diagram illustrating the configuration of an LC voltage control generator according to one embodiment of the present invention.

[0014] FIG. 4 is a diagram illustrating a current flow of an LC voltage control generator according to one embodiment of the present invention.

[0015] FIG. 5 is a diagram illustrating simulation results for quantifying magnetic field coupling by a superimposed inductor of an LC voltage-controlled generator according to one embodiment of the present invention.

[0016] FIGS. 6 to 8 are diagrams illustrating the results of an area reduction effect and performance verification experiment of an LC voltage control generator according to one embodiment of the present invention.

[0017] The purposes and effects of the present invention, as well as the technical configurations for achieving them, will become clearer with reference to the embodiments described in detail below, along with the accompanying drawings. In describing the present invention, detailed descriptions of known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the invention.

[0018] However, this is not intended to limit the present invention to a specific embodiment, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0019] And the terms described below are terms defined in consideration of the functions in the present invention, and these may vary depending on the intention or custom of the user or operator.

[0020] However, the present invention is not limited to the embodiments disclosed below and can be implemented in various different forms. These embodiments are provided solely to ensure complete disclosure of the present invention and to fully inform those skilled in the art of the invention of the scope of the invention. The present invention is defined solely by the scope of the claims. Therefore, such definitions should be based on the contents of this specification.

[0021] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0022] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0023] Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate an overall understanding in describing the present invention, identical reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0024]

[0025] Figure 1 is a diagram illustrating a conventional LC-VCO.

[0026] Fig. 1 (a) shows a form in which a nested octet inductor is added to generate the second harmonic for suppressing PN in a class F VCO. The implicit CM (Common-Mode) disclosed in Fig. 1 (b) is generated from the second harmonic to suppress PN. The two VCOs shown in Fig. 1 (b) are designed with their own transformers (xfmr) to avoid using additional area. However, the self-transformer-based VCO is unlikely to be implemented as a practical product due to variations due to nonlinearity and coupling. That is, when multiple LOs are involved, the self-transformer becomes complex and it is difficult to achieve a wide FTR for each VCO. Another solution to suppress PN is a method of generating the second harmonic by utilizing a tail noise filter. However, the tail inductor ( ) and tail capacitor ( ), main inductor ( ) and tail inductor ( ) inevitably increases the area due to potential coupling issues between them, so there is still a problem that noise filtering is inefficient.

[0027] One of the techniques to solve the above-mentioned area increase problem is the main inductor ( ) as a tail inductor ( ) is closely surrounded. As shown in (c) of Fig. 1, the external tail inductor ( ) is the magnetic field of the 8-shaped main inductor ( ) can be removed. However, the main inductor ( )'s magnetic field is external tail inductor ( ) also affects the efficiency of the tail noise filter, which may reduce the efficiency of the tail noise filter. In addition, in terms of area, the main inductor ( ) has a physical size of oscillation frequency f VCO As it is predetermined according to the surrounding tail inductor ( ) will eventually increase the overall area. In addition, the tail inductor ( ) is the main inductor ( ) has a larger radius than 2f VCO Achieving resonance in can be difficult.

[0028]

[0029] FIG. 2 is a diagram illustrating an example of area reduction through an LC voltage control generator according to one embodiment of the present invention, and FIG. 3 is a diagram illustrating a configuration of an LC voltage control generator according to one embodiment of the present invention.

[0030] Referring to FIG. 2, the present invention discloses an LC voltage-controlled generator using a tail noise filter including two overlapping tail inductors provided within a main inductor. This can save 27% of area compared to a conventional LC voltage-controlled generator in which the main inductor and tail inductor are respectively provided and thus require additional area occupied by the tail noise filter, and the overlapping tail inductors can prevent performance degradation by canceling out interference with the main inductor.

[0031]

[0032] Referring to (a) and (b) of FIG. 3, an LC voltage controlled generator (100) according to an embodiment of the present invention may include a superimposed inductor (110), a main inductor (120), a tail capacitor (130), and a decoupling capacitor (140). The superimposed inductor (110) may include a first tail inductor (111) having a figure-8 shape to which a supply voltage is applied and a second tail inductor (112) having a figure-8 shape to which a ground voltage is applied. In addition, the first inductor and the second inductor may be adjacent to each other and overlapped in a figure-8 shape. As illustrated in FIG. 3, the first inductor (111) and the second inductor (112) may be spaced apart from each other by a predetermined distance and overlapped in the same figure-8 shape.

[0033] The main inductor (120) has a space formed inside to surround the overlapping inductor, and at least a portion of it can be opened. Referring to (b) of Fig. 3, the main inductor (120) And the first tail inductor (111) and the second tail inductor (112) It can be confirmed that the tail capacitor (130) is And the decoupling capacitor (140) is You can see that.

[0034] The superimposed inductor (110) and the main inductor (120) can be manufactured from three types of metals. Referring to FIG. 2, m9 is a metal located on top of an ultra-thick metal (UTM), and since UTM has the maximum thickness and conductivity to achieve the maximum Q factor, it can be applied to the superimposed inductor (110) and the main inductor (120).

[0035] The main inductor (120) has an oscillation frequency f vco A 7-bit coarse tuning capacitor bank ( <6:0>) and fine adjustment capacitor bank ( ) can resonate in parallel. The superimposed inductor (110) is 2f for noise filtering. vco can resonate with the tail capacitor at 4 bits. is controlled by the 4-bit MSB of the CT-bank, No manual tuning is required. Also, can be set to 13pF to ensure AC short circuit, which is 2f vco The parallel configuration of tail components (tail capacitors, etc.) can be configured to resonate in. In addition, as shown in Fig. 3, the overlapping inductor (110) is connected to one tail capacitor (130) can be shared, and the node V of the supply voltage DD Node V of ground voltage SS One decoupling capacitor connecting them (140) can be shared, thus saving the overall area of ​​the voltage-controlled generator.

[0036]

[0037] FIG. 4 is a diagram illustrating a current flow of an LC voltage control generator according to one embodiment of the present invention.

[0038] Figure 4 shows an example visualizing the flow of current flowing in the superimposed inductor (110). The differential output of the LC voltage controlled generator (100) is V p and V m It can be expressed as . The direction of the current flowing in the first tail inductor (111) may be the opposite direction to the direction of the current flowing in the second tail inductor (112). For example, the current may flow counterclockwise in the first inductor (111), and the current may flow clockwise in the second inductor (112).

[0039] Specifically, V p is high, and V m When this is low, the current is L as indicated by the solid arrow direction. TAIL,VDD V through (first inductor) DDIn G m - begins to flow to the cell. Afterwards, as indicated by the dotted arrow direction, L TAIL,Vss V as return current through (second inductor) ss It is converted back to . As a result, the V of the solid arrow DD Current from and V of the dotted arrow ss The return currents flow in opposite directions.

[0040] Interference with the main inductor (120) can be eliminated by the currents flowing in different directions of the first tail inductor (111) and the second tail inductor (112). Since the first tail inductor (111) and the second tail inductor (112) overlap in a figure-8 shape, the magnetic field interference generated from the main inductor can be canceled through the magnetic field cancellation effect of the upper and lower loops. In addition, due to the currents flowing in opposite directions, the magnetic fields generated in each of the first tail inductor (111) and the second tail inductor (112) can be generated in opposite directions and canceled. Specifically, since the first tail inductor (111) and the second tail inductor (112) are closely adjacent, they can generate magnetic fields coupled in opposite directions and cancel each other. Therefore, the magnetic field generated in the overlapping inductor (110) has minimal influence on the main inductor (120).

[0041] FIG. 5 is a diagram illustrating simulation results for quantifying magnetic field coupling by a superimposed inductor of an LC voltage-controlled generator according to one embodiment of the present invention.

[0042] Coupling coefficient K for quantifying the magnetic field coupling between the first tail inductor (111) and the second tail inductor (112) 23 (K 32 ) can be simulated as shown in Fig. 4. 2f VCO K within the range 23The minimum value of is 0.65, indicating strong magnetic coupling between the first tail inductor (111) and the second tail inductor (112). The current in the coupling inductor (110) flows in both the same direction and the opposite direction to the main inductor (120). In the case of the current flowing in the opposite direction, the coupling of the magnetic field is at least 19.5 dB lower than the case of the current flowing in the same direction, from 2.67 dB to 3.37 dB, which is a negligible level. In addition, the Q factor of the main inductor (120) is lowered by 5% due to the overlapping structure of the coupling inductor (110), and the inductance of the main inductor (120) is f VCO Since the change is 0.46% compared to the main inductor (120), it is proven that the influence of the coupling inductor (110) on the main inductor (120) is minimized.

[0043] In order to verify the noise filtering effect by the superposition structure of the coupled inductor (110), it is necessary to examine the magnetic field coupling from the main inductor (120) to the coupled inductor (110). The 8-shaped coupled inductor (110) has a robust characteristic with respect to the magnetic field of the main inductor (120). In particular, the main inductor (120) generates a magnetic field that can potentially affect the coupled inductor (110), but the 8-shaped coupled inductor (110) can mitigate external interference through the cancellation effect of the upper and lower loops.

[0044] To verify that the influence of the main inductor (120) on the coupling inductor (110) is negligible, the coupling coefficient K is as shown in Fig. 4. 21 (from the main inductor (120) to the first tail inductor (111)) and K 21 (The simulation results of the second tail inductor (112) in the main inductor (120) are shown. At 16.04 GHz, both coupling coefficients are 2f VCO 8.8·10 within the range 3Although it was shown to be less than -101.4 dB, this indicates that the coupling from the main inductor (120) to the superimposed inductor (110) contributes to PN at a negligible level. The coupling level of the superimposed inductor (110) due to the main inductor (120) was maintained below -101.4 dB throughout the operating frequency, indicating that the coupling from the main inductor (120) to the superimposed inductor (110) is very low.

[0045]

[0046] FIGS. 6 to 8 are diagrams illustrating the area reduction effect and performance verification experiment results of an LC voltage control generator according to one embodiment of the present invention.

[0047]

[0048] Fig. 6 is a drawing comparing the size of an LC voltage-controlled generator (100) according to an embodiment of the present invention with an LC voltage-controlled generator to which an inductor overlap structure is not applied. The LC voltage-controlled generator can be manufactured using a 28 nm CMOS process. Except for the structure of the overlapped inductor (110), the entire structure is the same. As a result of comparing the size with that of a conventional LC voltage-controlled generator, referring to the microscope photograph shown in Fig. 6, the size of the conventional LC voltage-controlled generator is 0.033 μm. 2 And, the LC voltage control generator (100) according to one embodiment of the present invention is 0.024 μm 2 It occupies a smaller area than conventional VCOs.

[0049]

[0050] Fig. 7 shows a voltage controlled generator f min This is a diagram comparing the phase noise (PN) when operating at a voltage-controlled generator f minWhen operating at 1 MHz offset frequency, the conventional voltage-controlled generator exhibits a PN of -115.05 dBc / Hz, while the LC voltage-controlled generator (100) according to an embodiment of the present invention exhibits a PN of -116.38 dBc / Hz. Consequently, the LC voltage-controlled generator (100) according to an embodiment of the present invention can reduce the silicon area by 27% without lowering the PN even when the nested inductor (110) is implemented inside the main inductor (120). In addition, the power consumption of the LC voltage-controlled generator (100) according to an embodiment of the present invention is f min at 8.03mW, f max It can be seen that it indicates 6.57mW.

[0051]

[0052] Figure 8 is FoM TA and represents a benchmark relating the normalized PN to the active area. The FoM, FoM measured for the LC voltage controlled generator (100) according to one embodiment of the present invention A and FoM TA are -182.5 dB, -198.7 dB and -209.1 dB, respectively. Among the voltage-controlled generators utilizing tail noise filters, the LC voltage-controlled generator (100) according to one embodiment of the present invention has the lowest normalized PN and the best performing FoM. TA and has the smallest area. In addition, compared to a conventional LC voltage-controlled generator without a tail noise filter and an xfmr-based LC voltage-controlled generator, the LC voltage-controlled generator (100) according to an embodiment of the present invention can have a small area while exhibiting a competitive PN.

[0053] The features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified and implemented in other embodiments by a person having ordinary skill in the art to which the embodiments belong.

[0054] Accordingly, the contents related to such combinations and modifications should be interpreted as being included within the scope of the present invention. In addition, although the above description focuses on the embodiments, these are merely examples and do not limit the present invention. Those skilled in the art to which the present invention pertains will appreciate that various modifications and applications not illustrated above are possible without departing from the essential characteristics of the present embodiments. For example, each component specifically shown in the embodiments can be modified and implemented. In addition, the differences related to such modifications and applications should be interpreted as being included within the scope of the present invention defined in the appended claims.

[0055] The present invention can be used in an LC voltage controlled generator.

Claims

1. A superimposed inductor including a first tail inductor in the shape of an 8 connected to a supply voltage and a second tail inductor in the shape of an 8 to which a ground voltage is applied; and A main inductor having a space formed inside to surround the above-mentioned overlapping inductor and at least a portion of which is open, An LC voltage-controlled generator, wherein the first inductor and the second inductor are adjacent to each other and overlap each other in a figure-8 shape.

2. In paragraph 1, The direction of the current flowing in the first tail inductor is opposite to the direction of the current flowing in the second tail inductor, An LC voltage controlled generator, wherein interference with the main inductor is eliminated by currents flowing in different directions in the first tail inductor and the second tail inductor.

3. In paragraph 1, The above main inductor has an oscillation frequency f vco In parallel with the 7-bit coarse tuning capacitor bank and fine tuning capacitor bank, The above nested inductor is 2f for noise filtering. vco An LC voltage controlled generator that resonates with the tail capacitor.

4. In paragraph 3, The above nested inductors share one tail capacitor, An LC voltage controlled generator, which shares a single decoupling capacitor connecting the supply voltage node and the ground voltage node.

5. In paragraph 2, An LC voltage-controlled generator, wherein the first tail inductor and the second tail inductor are adjacent and overlap each other, and magnetic fields generated in each of the first tail inductor and the second tail inductor are generated in opposite directions and cancel each other out by currents flowing in opposite directions.

6. In paragraph 5, An LC voltage-controlled generator in which interference caused by a magnetic field generated in a main inductor is canceled out through the magnetic field canceling effect of the upper and lower loops as the first tail inductor and the second tail inductor overlap in a figure-8 shape.

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