A transformer electromagnetic coupling-based on-chip inductance adjusting device and a control method thereof
By combining transformer electromagnetic coupling and switched capacitor array, the on-chip inductor is indirectly adjusted, solving the problems of limited inductor adjustable range and high loss in the existing technology, and realizing wide-range inductor adjustment and high-integration RF circuit design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTHEAST UNIV
- Filing Date
- 2026-03-27
- Publication Date
- 2026-07-31
AI Technical Summary
In the existing technology, the adjustable range of on-chip inductors is limited, and the adjustment process introduces additional losses and increases layout complexity, making it difficult to meet the requirements of multi-band, multi-mode and broadband RF integrated circuits.
An on-chip inductor adjustment device using transformer electromagnetic coupling adjusts the equivalent capacitance of the secondary coil indirectly by adjusting the equivalent inductance of the primary coil through the electromagnetic coupling of the primary and secondary coils and combined with a switched capacitor array, thereby avoiding the direct introduction of switching devices into the inductor.
It enables wide-range adjustment of inductance value without changing the physical structure of the primary coil, reducing signal path loss, simplifying layout design, and meeting the needs of multi-mode reconfigurable RF circuits.
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Figure CN122496032A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of radio frequency integrated circuits, and specifically relates to an on-chip inductor adjustment device and its control method based on transformer electromagnetic coupling. Background Technology
[0002] As wireless communication systems evolve towards multi-band, multi-mode, and broadband capabilities, radio frequency (RF) integrated circuits (ICs) are placing higher demands on the reconfigurability of on-chip passive components. On-chip inductors, as key passive components in RF ICs, are widely used in low-noise amplifiers, power amplifiers, phase shifters, and voltage-controlled oscillators (VCOs). Their parameters and adjustable range directly affect the performance and operating frequency band of the RF circuit. In existing technologies, to achieve adjustable on-chip inductor parameters, taps are typically added to the inductor and switched using transistor switches to change the equivalent number of turns. However, in such solutions, the transistor switches are often located in the RF signal path, introducing additional losses. Furthermore, multi-tap inductor structures significantly increase layout complexity, hindering the realization of high integration density in RF ICs. Summary of the Invention
[0003] The purpose of this invention is to provide an on-chip inductor adjustment device and its control method based on transformer electromagnetic coupling, which can realize the wide-range adjustable function of on-chip passive inductors in the radio frequency band.
[0004] To achieve the above objectives, the solution of the present invention is:
[0005] An on-chip inductor adjustment device based on transformer electromagnetic coupling includes a primary coil and a secondary coil electromagnetically coupled to the primary coil. The primary coil and the secondary coil together constitute an on-chip transformer, wherein the primary coil serves as the on-chip inductor to be adjusted.
[0006] The secondary coil is connected in parallel with the switched capacitor array, and one end is connected to a reference potential. The switched capacitor array includes several switched capacitor branches connected in parallel. Each switched capacitor branch includes a capacitor unit and a switching device connected in series. The switching device realizes the connection or disconnection of its corresponding capacitor unit under the control of a digital control signal.
[0007] Each capacitor unit in the aforementioned switched capacitor array is configured according to a predetermined weight, either through equal weighting or binary weighted configuration.
[0008] The aforementioned switching device uses an NMOS transistor, with its source connected to a reference potential, its drain connected to one end of the corresponding capacitor cell, and its gate used to connect to a digital control signal.
[0009] A control method for an on-chip inductor adjustment device based on transformer electromagnetic coupling, as described above, provides digital control signals to control the switching state of each switching device in the switched capacitor array, thereby controlling the connection or disconnection of each capacitor unit in the switched capacitor array. The method utilizes the electromagnetic coupling effect between the primary coil and the secondary coil to adjust the equivalent inductance value of the primary coil.
[0010] Among them, the digital control signal is set as Let n be the number of switching devices in the switched capacitor array, then the total equivalent capacitance of the switched capacitor array is... for,
[0011] ,
[0012] in, This represents the capacitance value of each capacitor unit in the switched capacitor array.
[0013] The capacitance value of each capacitor unit in the above switched capacitor array is configured according to a predetermined weight, which can be either equal weight configuration or binary weighted configuration.
[0014] The equivalent inductance value of the primary coil mentioned above for,
[0015] ,
[0016] in, This is the inductance value of the primary coil. This is the inductance value of the secondary coil; Angular frequency, This represents the coupling coefficient between the primary and secondary coils. This represents the total equivalent capacitance of the switched capacitor array. This is the parasitic resistance of the secondary coil.
[0017] The parasitic resistance of the aforementioned secondary coil Calculated according to the following formula,
[0018]
[0019] in, This is the quality factor of the secondary coil.
[0020] By adopting the above solution, compared with the prior art, the present invention has the following technical effects:
[0021] (1) By adjusting the equivalent capacitance of the secondary coil of the transformer in parallel, the equivalent inductance of the primary coil is changed by using the electromagnetic coupling effect. The adjustable function of the inductance is realized without changing the physical structure of the primary coil, which improves the flexibility and reconfigurability of the on-chip inductor.
[0022] (2) Compared with the adjustment method of directly connecting switches in series / parallel in the inductor, the present invention indirectly adjusts the equivalent inductance through electromagnetic coupling, which effectively reduces the series resistance and parasitic effects introduced by the switches in the signal path, thereby reducing losses.
[0023] (3) By utilizing the electromagnetic coupling of the transformer and the designability of the switched capacitor array parameters, a wider range of equivalent inductance adjustment can be achieved; at the same time, a higher adjustment resolution can be obtained through a multi-position capacitor array, which meets the requirements of broadband and multi-mode reconfigurable RF circuits.
[0024] (4) The inductance adjustment function is realized through a single transformer structure, which can reduce the need for repeated layout of multi-tap inductors or multiple independent inductors, effectively save chip area while meeting performance requirements and simplifying system design. Attached Figure Description
[0025] Figure 1 This is a circuit diagram of the present invention;
[0026] Figure 2 This is a layout of one application embodiment of the present invention using a 65nm CMOS process;
[0027] Figure 3 These are post-simulation results of the equivalent inductance values of the primary coil in different modes in the application embodiments of the present invention;
[0028] Figure 4 This is a post-simulation result of the gain amplitude-frequency characteristics of the present invention applied to a reconfigurable low-noise amplifier for a receiver RF front end. Detailed Implementation
[0029] The technical solution and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.
[0030] This invention provides an on-chip inductor adjustment device based on transformer electromagnetic coupling. In practical applications, such as... Figure 1 As shown, the device includes a primary coil L1 and a secondary coil L2 electromagnetically coupled to the primary coil. The primary and secondary coils together constitute an on-chip transformer with a coupling coefficient of k. The primary coil serves as the on-chip inductor to be adjusted. One end of the secondary coil is connected to a reference potential, and the other end is connected in parallel to a switched capacitor array. The capacitor array includes multiple capacitor units. Each capacitor unit is selectively connected to the secondary coil through a corresponding switching device controlled by a digital control signal to connect or disconnect the capacitor unit.
[0031] The present invention also provides a control method for the aforementioned device, which provides a digital control signal to control the switching state of each switching device in the switched capacitor array, thereby controlling the connection or disconnection of each capacitor unit in the switched capacitor array, changing the equivalent parallel capacitance value of the secondary coil, and utilizing the electromagnetic coupling effect of the transformer to achieve a wide range of adjustable equivalent inductance value of the primary coil.
[0032] The plurality of capacitor units include capacitors C0, C1, C2 to C1. n Each capacitor is connected in series with a switching transistor controlled by digital control signals B[0], B[1], B[2] to B[n], thereby forming the capacitor unit. Each capacitor unit in the switched capacitor array is configured according to a predetermined weight, which includes equal weight configuration or binary weighted configuration, so as to realize multi-level discrete adjustment of the equivalent inductance value of the primary coil.
[0033] The switched capacitor array is controlled by NMOS transistors. In each capacitor unit, the source of the NMOS transistor is connected to the reference potential, the drain is connected to the corresponding capacitor, and the gate is connected to the corresponding digital control bit.
[0034] like Figure 1 As shown, the voltage at port P1 of the primary coil L1 is V. P1 The voltage at port P2 of the primary coil L1 is V. P2 The current flowing into the primary coil L1 at its corresponding terminal is I1, and the current flowing out of the secondary coil L2 at its corresponding terminal is I2. The voltage across the primary coil L1 can be expressed as follows:
[0035]
[0036] in, For complex frequencies, This is the parasitic resistance of the primary coil. , This is the quality factor of the primary coil.
[0037] like Figure 1 As shown, under the control of the n-bit binary code of B[n:0], the total equivalent capacitance of the switched capacitor array is [value missing]. The total equivalent capacitance is connected in parallel with the secondary winding of the transformer. The voltage across the total equivalent capacitance can be expressed as follows:
[0038]
[0039] At this point, through the electromagnetic coupling of the transformer, the equivalent inductance across the primary coil L1 is calculated using the formula... Connect the formulas for the voltage across the primary coil L1, the secondary coil L2, and the total equivalent capacitance connected in parallel across the secondary coil L2. The formula is used to further obtain the equivalent inductance across the primary coil L1. as follows:
[0040]
[0041] In actual implementation, such as Figure 2 As shown, a layout for an application embodiment was designed using a 65nm CMOS process. The primary coil L1 has an inductance of approximately 310 pH, the secondary coil L2 has an inductance of approximately 284 pH, and their coupling coefficient is approximately 0.71. The capacitor array at the secondary coil consists of three capacitors C0, C1, and C2, with capacitance values of approximately 80 fF, 160 fF, and 320 fF, respectively.
[0042] like Figure 3 As shown, it demonstrates Figure 2 The simulation results for the circuit layout shown are as follows. Using the described method, an equivalent inductance adjustment range of 324–401 pH was achieved at 8 GHz; an equivalent inductance adjustment range of 331–471 pH was achieved at 10 GHz; and an equivalent inductance adjustment range of 29–564 pH was achieved at 15 GHz.
[0043] In practical applications, based on the on-chip inductor adjustment principle provided by this invention, a reconfigurable low-noise amplifier for the receiver RF front-end was designed using 65nm CMOS technology. Its gain-amplitude frequency characteristics in multiple operating modes are as follows: Figure 4 As shown. This reconfigurable low-noise amplifier operates from 17.8 to 35.8 GHz, enabling seamless switching of the operating frequency band and flexible selection of wide and narrow band amplification modes.
[0044] This invention controls a capacitor array connected in parallel with the secondary coil of a transformer using transistor switches, thereby changing the equivalent parallel capacitance of the secondary coil. It also utilizes the electromagnetic coupling effect of the transformer to achieve a wide range of adjustable equivalent inductance of the primary coil. This invention avoids introducing transistor switches into the signal path, thus preventing additional losses caused by switching devices being located in the signal path. Simultaneously, the transformer's layout area remains comparable to that of a single on-chip inductor, making it suitable for high-integration designs of multi-mode reconfigurable RF circuits.
[0045] In the several embodiments provided by this invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.
Claims
1. An on-chip inductor adjustment device based on transformer electromagnetic coupling, characterized in that: It includes a primary coil and a secondary coil electromagnetically coupled to the primary coil, wherein the primary coil and the secondary coil together constitute an on-chip transformer, and the primary coil serves as an on-chip inductor to be adjusted. The secondary coil is connected in parallel with the switched capacitor array, and one end is connected to a reference potential. The switched capacitor array includes several switched capacitor branches connected in parallel. Each switched capacitor branch includes a capacitor unit and a switching device connected in series. The switching device realizes the connection or disconnection of its corresponding capacitor unit under the control of a digital control signal.
2. The apparatus as described in claim 1, characterized in that: Each capacitor unit in the switched capacitor array is configured according to a predetermined weight, either by equal weighting or by binary weighting.
3. The apparatus as described in claim 1, characterized in that: The switching device is an NMOS transistor, with its source connected to the reference potential, its drain connected to one end of the corresponding capacitor unit, and its gate used to connect to the digital control signal.
4. A control method for an on-chip inductor adjustment device based on transformer electromagnetic coupling as described in claim 1, characterized in that: A digital control signal is provided to control the switching state of each switching device in the switched capacitor array, thereby controlling the connection or disconnection of each capacitor unit in the switched capacitor array. The equivalent inductance value of the primary coil is adjusted by utilizing the electromagnetic coupling effect between the primary coil and the secondary coil.
5. The method as described in claim 4, characterized in that: Set the digital control signal to Let n be the number of switching devices in the switched capacitor array, then the total equivalent capacitance of the switched capacitor array is... for, ， in, This represents the capacitance value of each capacitor unit in the switched capacitor array.
6. The method as described in claim 5, characterized in that: The capacitance value of each capacitor unit in the switched capacitor array is configured according to a predetermined weight, which can be either equal weight configuration or binary weighted configuration.
7. The method as described in claim 4, characterized in that: The equivalent inductance value of the primary coil for, ， in, This is the inductance value of the primary coil. This is the inductance value of the secondary coil; Angular frequency, This represents the coupling coefficient between the primary and secondary coils. This represents the total equivalent capacitance of the switched capacitor array. This is the parasitic resistance of the secondary coil.
8. The method as described in claim 7, characterized in that: The parasitic resistance of the secondary coil Calculated according to the following formula, ， in, This is the quality factor of the secondary coil.