A dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning

Abstract

The application discloses a dual-mode W-waveband voltage-controlled oscillator based on transformer magnetic tuning, which comprises two pairs of cross-coupled MOS transistors, a dual-mode six-coil transformer, a fine-tuning MOS transistor with a tuning switch, a coarse-tuning MOS transistor with a tuning switch and two pairs of output buffer stage MOS transistors; the change of the equivalent inductance value of a resonant cavity is realized by controlling the fine-tuning MOS transistor Msw1 and the fine-tuning MOS transistor Msw2; the fine-tuning MOS transistor Msw1 is turned on in a high-frequency band with small inductance and is turned off in a low-frequency band with large inductance; for fine frequency tuning without a varactor, the resistance of the fine-tuning MOS transistor Msw2 is changed by changing the gate voltage of the fine-tuning MOS transistor Msw2, so that fine tuning of the equivalent inductance is realized; the dual-mode six-coil transformer is used to replace a single-mode three-coil transformer, so that a four-frequency-band W-waveband voltage-controlled oscillator is realized. The application has higher resonant cavity Q value, can realize better phase noise and provides a high-quality local oscillator signal source for a W-waveband signal transceiving front end.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit technology, specifically relating to a dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning. Background Technology

[0002] The W-band frequency range of 75 GHz to 110 GHz has a wide range of applications, including communications, radar, radio astronomy, weather radar, medical imaging, and scientific research. With the continuous miniaturization of CMOS process nodes, it is now possible to realize voltage-controlled oscillators (VCOs) based on CMOS technology in this band. However, achieving VCOs with low phase noise, low power consumption, and a wide tuning range at such high frequencies remains challenging.

[0003] Traditional varactor tuning methods suffer from a sharp drop in the quality factor (Q) as the frequency increases. This leads to a decrease in the effective quality factor (Q) of the resonant cavity, ultimately compromising the phase noise performance of the entire voltage-controlled oscillator (VCO). Furthermore, considering parasitic effects in the W-band frequency range, the tuning range of varactors is typically limited to below 6%. This is far from sufficient for most applications, especially those requiring adaptation to process and temperature variations. Therefore, improving the resonant cavity's quality factor (Q), reducing phase noise, and achieving a wider frequency tuning range have become highly attractive challenges in the design of W-band VCO circuits. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A transformer-based dual-mode W-band voltage-controlled oscillator includes cross-coupled pair MOSFETs M1, M2, M3, and M4; dual-mode six-coil transformer coupled resonant coils L1 and L2; dual-mode six-coil transformer fine-tuning coils Lsw1, Lsw2, Lsw3, and Lsw4; tuning switch fine-tuning MOSFETs Msw1, Msw2, Msw3, and Msw4; output buffer stage MOSFETs M5, M6, M7, and M8.

[0007] The sources of the cross-coupled MOS transistors M1 and M2 are connected to ground, and the drains of the cross-coupled MOS transistors M1 and M2 are respectively connected to the two ends of the dual-mode six-coil transformer coupled resonant coil L1. The gate of the cross-coupled MOS transistor M1 is connected to the drain of the cross-coupled MOS transistor M2.

[0008] The gate of the output buffer stage MOSFET M5 is connected to the drain of the cross-coupled MOSFET M1, the source of the output buffer stage MOSFET M5 is grounded, and the drain of the output buffer stage MOSFET M5 is connected to the output OUT1P; the gate of the output buffer stage MOSFET M6 is connected to the drain of the cross-coupled MOSFET M2, the source of the output buffer stage MOSFET M6 is grounded, and the drain of the output buffer stage MOSFET M6 is connected to the output OUT1N.

[0009] The gate and drain of the fine-tuned MOS transistor Msw1 are respectively connected to the two ends of the fine-tuning coil Lsw1 of the dual-mode six-coil transformer, and the source of the fine-tuned MOS transistor Msw1 is connected to the gate fine-tuning control voltage VS1; the gate and drain of the coarse-tuned MOS transistor Msw3 are respectively connected to the two ends of the coarse-tuning coil Lsw3 of the dual-mode six-coil transformer, and the source of the coarse-tuned MOS transistor Msw3 is connected to the gate coarse-tuning control voltage VS3.

[0010] The sources of the cross-coupled MOSFETs M3 and M4 are connected to ground, the drains of the cross-coupled MOSFETs M3 and M4 are connected to the two ends of the dual-mode six-coil transformer coupled resonant coil L2, and the gate of the cross-coupled MOSFET M3 is connected to the drain of the cross-coupled MOSFET M4.

[0011] The gate of the output buffer stage MOSFET M7 is connected to the drain of the cross-coupled MOSFET M3, the source of the output buffer stage MOSFET M7 is grounded, and the drain of the output buffer stage MOSFET M7 is connected to the output OUT2P; the gate of the output buffer stage MOSFET M8 is connected to the drain of the cross-coupled MOSFET M4, the source of the output buffer stage MOSFET M8 is grounded, and the drain of the output buffer stage MOSFET M8 is connected to the output OUT2N.

[0012] The gate and drain of the fine-tuned MOS transistor Msw2 are respectively connected to the two ends of the fine-tuning coil Lsw2 of the dual-mode six-coil transformer, and the source of the fine-tuned MOS transistor Msw2 is connected to the gate fine-tuning control voltage VS2; the gate and drain of the coarse-tuned MOS transistor Msw4 are respectively connected to the two ends of the coarse-tuning coil Lsw4 of the dual-mode six-coil transformer, and the source of the coarse-tuned MOS transistor Msw4 is connected to the gate coarse-tuning control voltage VS4.

[0013] In the above technical solution, the fine-tuning coil Lsw1 of the dual-mode six-coil transformer is located in the innermost coil, and the fine-tuning coil Lsw2 of the dual-mode six-coil transformer is located in the outermost coil. Between the fine-tuning coil Lsw1 and the fine-tuning coil Lsw2 of the dual-mode six-coil transformer, the coupling resonant coil L1, the coarse-tuning coil Lsw3, the coarse-tuning coil Lsw4, and the coupling resonant coil L2 of the dual-mode six-coil transformer are arranged in sequence, thereby forming a dual-mode six-coil transformer.

[0014] In the above technical solution, the coarse tuning coil Lsw3 and coarse tuning coil Lsw4 of the dual-mode six-coil transformer are configured as shielded coils.

[0015] In the above technical solution, the dual-mode six-coil transformer fine-tuning coil Lsw1, dual-mode six-coil transformer fine-tuning coil Lsw2, dual-mode six-coil transformer coupling resonant coil L1, dual-mode six-coil transformer coarse-tuning coil Lsw3, dual-mode six-coil transformer coarse-tuning coil Lsw4 and dual-mode six-coil transformer coupling resonant coil L2 all use a top-layer thick metal.

[0016] In the above technical solution, when the dual-mode six-coil transformer is in high-frequency mode, the dual-mode six-coil transformer couples the resonant coil L1 and the fine-tuning coil Lsw1 of the dual-mode six-coil transformer. The coarse-tuning MOS transistor Msw3 is configured to be turned on, and the coarse-tuning MOS transistor Msw4 is configured to be turned off.

[0017] In the above technical solution, in the low-frequency mode, the dual-mode six-coil transformer uses the dual-mode six-coil transformer to couple the resonant coil L2 and the fine-tuning coil Lsw2 of the dual-mode six-coil transformer. The coarse-tuning MOS transistor Msw3 of the tuning switch is configured to be off, and the coarse-tuning MOS transistor Msw4 of the tuning switch is configured to be on.

[0018] In the above technical solution, the dual-mode six-coil transformer generates a four-band W-band signal.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The transformer-based dual-mode W-band voltage-controlled oscillator provided by the present invention effectively solves the problem that the quality factor (Q) of the varactor tube decreases sharply with the increase of frequency compared with the traditional varactor tube tuning method. At the same time, it reduces the parasitic capacitance inside the resonant cavity, so that the W-band oscillator without varactor tube can achieve low phase noise and a wide frequency tuning range, providing a reliable local oscillator signal source for the generation of W-band frequency.

[0021] (2) Compared with a three-coil single-mode transformer, the present invention uses a six-coil dual-mode transformer, which enables it to generate an ultra-wideband four-band W-band signal. This not only achieves double the frequency tuning range, but also brings a wider tuning range and better phase noise performance. Attached Figure Description

[0022] Figure 1 The circuit diagram of the dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning described in this invention is shown below.

[0023] Figure 2 This is a layout diagram of the dual-mode six-coil transformer described in this invention;

[0024] Figure 3 The transient waveforms of the voltage-controlled oscillator described in this invention under different gate voltages are shown below.

[0025] Figure 4 The graph shows the relationship between different sideband frequencies and gate voltage for the voltage-controlled oscillator described in this invention.

[0026] Figure 5 The diagram shows the phase noise characteristics of the voltage-controlled oscillator described in this invention under different gate voltages. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0028] Please see Figure 1 , Figure 1 This is a circuit diagram of a dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning provided in an embodiment of the present invention. The voltage-controlled oscillator includes two pairs of cross-coupled MOSFETs M1 and M2, M3 and M4, dual-mode six-coil transformer coupled resonant coils L1 and L2, dual-mode six-coil transformer fine-tuning coils Lsw1 and Lsw2, dual-mode six-coil transformer coarse-tuning coils Lsw3 and Lsw4, tuning switch fine-tuning MOSFETs Msw1 and Msw2, tuning switch coarse-tuning MOSFETs Msw3 and Msw4, and two pairs of output buffer stage MOSFETs M5 and M6, M7 and M8.

[0029] The first pair of cross-coupled MOSFETs M1 and M2 have their sources connected to ground, their gates connected to the drains of M2, and their drains connected to the gates of M1. The drains of M1 and M2 are connected to the two ends of the dual-mode six-coil transformer coupled resonant coil L1. The gate of the output buffer stage MOSFET M5 is connected to the drain of M1, its source is connected to ground, and its drain is connected to the output OUT1P. The gate of the output buffer stage MOSFET M6 is connected to the drain of M2, its source is connected to ground, and its drain is connected to the output OUT1N. The gate and drain of the fine-tuning MOSFET Msw1 are respectively connected to the two ends of the fine-tuning coil Lsw1 of the dual-mode six-coil transformer, and the source of Msw1 is connected to the gate fine-tuning control voltage VS1. The gate and drain of the coarse-tuning MOSFET Msw3 are respectively connected to the two ends of the coarse-tuning coil Lsw3 of the dual-mode six-coil transformer, and the source of Msw3 is connected to the gate coarse-tuning control voltage VS3.

[0030] The second pair of cross-coupled MOSFETs M3 and M4 have their sources connected to ground, their gates connected to the drains of M4, and their drains connected to the gates of M3. The drains of M3 and M4 are connected to the two ends of the dual-mode six-coil transformer coupled resonant coil L2. The gate of the output buffer stage MOSFET M7 is connected to the drain of M3, its source is connected to ground, and its drain is connected to the output OUT2P. The gate of the output buffer stage MOSFET M8 is connected to the drain of M4, its source is connected to ground, and its drain is connected to the output OUT2N. The gate and drain of the fine-tuning MOSFET Msw2 are respectively connected to the two ends of the fine-tuning coil Lsw2 of the dual-mode six-coil transformer, and the source of Msw2 is connected to the gate fine-tuning control voltage VS2. The gate and drain of the coarse-tuning MOSFET Msw4 are respectively connected to the two ends of the coarse-tuning coil Lsw4 of the dual-mode six-coil transformer, and the source of Msw4 is connected to the gate coarse-tuning control voltage VS4.

[0031] In this embodiment, two pairs of cross-coupled transistors provide negative resistance to compensate for the loss of the resonant cavity. The resulting parasitic capacitance and the equivalent inductance of the dual-mode six-coil transformer form a resonant cavity to generate an oscillation signal. When the tuning switches coarsely tune the MOSFETs Msw3 and Msw4, the equivalent inductance is small when they are turned on, forming a high-frequency band. When they are turned off, the equivalent inductance is large, forming a low-frequency band. By finely tuning the gate voltages (VS1 and VS2) of the MOSFETs Msw1 and Msw2 through the tuning switches, their resistances (Rsw1 and Rsw2) are changed, thus achieving fine tuning of the equivalent inductance.

[0032] Please see Figure 2 , Figure 2This is a layout diagram of a dual-mode six-coil transformer provided in an embodiment of the present invention, including: coupled resonant coils L1 and L2, fine-tuning coils Lsw1 and Lsw2, and coarse-tuning coils Lsw3 and Lsw4. The coarse-tuning coils Lsw3 and Lsw4 are configured as shielded coils and placed between L1 and L2 to reduce the coupling coefficient between the resonant coils L1 and L2. Only one of Lsw3 and Lsw4 can be used at any given time. The fine-tuning coil Lsw1 is placed in the innermost coil, and fine-tuning of the equivalent inductance L1eq is achieved through magnetic tuning with L1. SW2 is placed on the outermost coil, and fine tuning of the equivalent inductance L2eq is achieved through magnetic tuning with L2. All coils use a thick top layer of metal to reduce losses. In the 100GHz simulation, the self-inductance values ​​of the coupled resonant coils L1 and L2 are 110pH and 134pH, respectively; the self-inductance values ​​of the fine-tuned coils Lsw1 and Lsw2 are 72pH and 183pH, respectively; the self-inductance values ​​of the coarse-tuned coils Lsw3 and Lsw4 are 86pH and 104pH, respectively; and the coupling coefficient between the coupled resonant coils L1 and L2 is 0.32.

[0033] In this implementation example, the dual-mode six-coil transformer is powered only by VDD1 in high-frequency mode, using coupled resonant coil L1 and fine-tuning coil Lsw1, while coarse-tuning coils Lsw3 and Lsw4 are configured to be on and off, respectively. In low-frequency mode, power supply VDD2 is powered only, using coupled resonant coil L2 and fine-tuning coil Lsw2, while coarse-tuning coils Lsw3 and Lsw4 are configured to be off and on, respectively. To ensure the stability of dual-mode operation, coarse-tuning coils Lsw3 and Lsw4 are configured as shielded coils to reduce the coupling coefficient of coupled resonant coils L1 and L2, and at any given time, only one of coarse-tuning coils Lsw3 and Lsw4 is on.

[0034] The advantages of the transformer-based single-mode W-band voltage-controlled oscillator of the present invention are further illustrated by the simulation experiment below.

[0035] This example uses a 40nm CMOS process to fabricate a dual-mode W-band voltage-controlled oscillator. This process has one poly layer and ten metal layers, with the transformer structure primarily implemented using an M10 thick metal layer. The parameters of the transformer-tuned dual-mode W-band voltage-controlled oscillator in this example are shown in Table 1.

[0036] Table 1

[0037] Power supply voltage VDD1 (V) 1 Power supply voltage VDD2 (V) 1 Cross-coupling pairs M1-M4 1μm*24*40nm Output buffer stage MOSFETs M5-M8 1μm*10*40nm Tuning switches and fine-tuning MOSFETs Msw1-Msw2 1μm*8*40nm Tuning switches, coarse tuning MOSFETs Msw3-Msw4 1μm*6*100nm Coupled resonant coils L1 and L2 110pH / 134pH Fine tuning coils Lsw1 and Lsw2 72pH / 183pH coarse tuning coils Lsw3 and Lsw4 86pH / 104pH

[0038] Please see Figure 3 , Figure 3This embodiment of the invention provides a transformer-based dual-mode W-band voltage-controlled oscillator (VCO) with power supply VDD1 connected in high-frequency mode. The system uses a coupled resonant coil L1, with the coarse-tuned MOSFET Msw3 configured to be on and the coarse-tuned MOSFET Msw4 configured to be off. The transient waveforms of the fine-tuned MOSFET Msw1 under different gate voltages are shown. According to the simulation waveforms, after oscillation starts, the VCO amplitude reaches 1.2V. As the gate voltage of the fine-tuned MOSFET Msw1 gradually increases, the VCO amplitude slightly decreases.

[0039] The truth table for the selection of each sideband of the transformer-magnetically tuned dual-mode W-band voltage-controlled oscillator in this embodiment is shown in Table 2:

[0040] Table 2

[0041]

[0042] Please see Figure 4 , Figure 4 This is a graph showing the relationship between the gate voltage and different sideband frequencies of the transformer-based dual-mode W-band voltage-controlled oscillator provided in this embodiment of the invention. By selecting the configuration methods in Table 2, four different output frequency sidebands can be obtained. According to the simulated output waveform, it can be seen that: by controlling the fine-tuning MOS transistors Msw1 (Msw2), the output frequency can be continuously adjusted, and by controlling the coarse-tuning MOS transistors Msw3 (Msw4), the output frequency sideband can be adjusted. The output frequency range is 85-108GHz, achieving a wide frequency tuning range of 23.8%.

[0043] Please see Figure 5 , Figure 5 This embodiment of the invention provides a dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning. With power supply VDD1 connected in high-frequency mode, a coupled resonant coil L1 is used. The coarse-tuning MOS transistor Msw3 is configured to be on, and the coarse-tuning MOS transistor Msw4 is configured to be off. The phase noise characteristics of the fine-tuning MOS transistor Msw1 under different gate voltages are shown in the diagram. According to the phase noise characteristics, when the output frequency is around 100 GHz, as the gate voltage increases, the output phase noise of the voltage-controlled oscillator gradually increases from -107.36 dBc / Hz@10 MHz to -102.31 dBc / Hz@10 MHz. This is because as the gate voltage increases, the quality factor (Q) of the dual-mode six-coil transformer gradually decreases. At the 100 GHz output frequency, since no switched capacitor array and varactor diodes are used for tuning, a wide frequency tuning range and good phase noise performance are achieved.

[0044] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning, characterized in that, This includes cross-coupled MOSFETs M1, M2, M3, and M4; dual-mode six-coil transformer coupled resonant coil L1 and L2; dual-mode six-coil transformer fine-tuning coil Lsw1, Lsw2, Lsw3, and Lsw4; tuning switch fine-tuning MOSFETs Msw1, Msw2, Msw3, and Msw4; output buffer stage MOSFETs M5, M6, M7, and M8. The sources of the cross-coupled MOS transistors M1 and M2 are connected to ground, and the drains of the cross-coupled MOS transistors M1 and M2 are respectively connected to the two ends of the dual-mode six-coil transformer coupled resonant coil L1. The gate of the cross-coupled MOS transistor M1 is connected to the drain of the cross-coupled MOS transistor M2, and the gate of the cross-coupled MOS transistor M2 is connected to the drain of the cross-coupled MOS transistor M1. The gate of the output buffer stage MOSFET M5 is connected to the drain of the cross-coupled MOSFET M1, the source of the output buffer stage MOSFET M5 is grounded, and the drain of the output buffer stage MOSFET M5 is connected to the output OUT1P; the gate of the output buffer stage MOSFET M6 is connected to the drain of the cross-coupled MOSFET M2, the source of the output buffer stage MOSFET M6 is grounded, and the drain of the output buffer stage MOSFET M6 is connected to the output OUT1N. The gate and drain of the fine-tuned MOS transistor Msw1 are respectively connected to the two ends of the fine-tuning coil Lsw1 of the dual-mode six-coil transformer, and the source of the fine-tuned MOS transistor Msw1 is connected to the gate fine-tuning control voltage VS1; the gate and drain of the coarse-tuned MOS transistor Msw3 are respectively connected to the two ends of the coarse-tuning coil Lsw3 of the dual-mode six-coil transformer, and the source of the coarse-tuned MOS transistor Msw3 is connected to the gate coarse-tuning control voltage VS3. The sources of the cross-coupled MOSFETs M3 and M4 are connected to ground, and the drains of the cross-coupled MOSFETs M3 and M4 are connected to the two ends of the dual-mode six-coil transformer coupled resonant coil L2. The gate of the cross-coupled MOSFET M3 is connected to the drain of the cross-coupled MOSFET M4, and the gate of the cross-coupled MOSFET M4 is connected to the drain of the cross-coupled MOSFET M3. The gate of the output buffer stage MOSFET M7 is connected to the drain of the cross-coupled MOSFET M3, the source of the output buffer stage MOSFET M7 is grounded, and the drain of the output buffer stage MOSFET M7 is connected to the output OUT2P; the gate of the output buffer stage MOSFET M8 is connected to the drain of the cross-coupled MOSFET M4, the source of the output buffer stage MOSFET M8 is grounded, and the drain of the output buffer stage MOSFET M8 is connected to the output OUT2N. The gate and drain of the fine-tuned MOS transistor Msw2 are respectively connected to the two ends of the fine-tuning coil Lsw2 of the dual-mode six-coil transformer, and the source of the fine-tuned MOS transistor Msw2 is connected to the gate fine-tuning control voltage VS2; the gate and drain of the coarse-tuned MOS transistor Msw4 are respectively connected to the two ends of the coarse-tuning coil Lsw4 of the dual-mode six-coil transformer, and the source of the coarse-tuned MOS transistor Msw4 is connected to the gate coarse-tuning control voltage VS4. The fine-tuning coil Lsw1 of the dual-mode six-coil transformer is located in the innermost coil, and the fine-tuning coil Lsw2 of the dual-mode six-coil transformer is located in the outermost coil. Between the fine-tuning coils Lsw1 and Lsw2, the coupling resonant coil L1, the coarse-tuning coil Lsw3, the coarse-tuning coil Lsw4, and the coupling resonant coil L2 of the dual-mode six-coil transformer are arranged in sequence, thereby forming a dual-mode six-coil transformer.

2. The dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning according to claim 1, characterized in that, The coarse tuning coils Lsw3 and Lsw4 of the dual-mode six-coil transformer are configured as shielded coils.

3. The dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning according to claim 2, characterized in that, The dual-mode six-coil transformer fine-tuning coil Lsw1, dual-mode six-coil transformer fine-tuning coil Lsw2, dual-mode six-coil transformer coupling resonant coil L1, dual-mode six-coil transformer coarse-tuning coil Lsw3, dual-mode six-coil transformer coarse-tuning coil Lsw4, and dual-mode six-coil transformer coupling resonant coil L2 all use a top-layer thick metal.

4. The dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning according to claim 1, characterized in that, In high-frequency mode, the dual-mode six-coil transformer couples the resonant coil L1 and the fine-tuning coil Lsw1. The coarse-tuning MOS transistor Msw3 is configured to be on, and the coarse-tuning MOS transistor Msw4 is configured to be off.

5. The dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning according to claim 4, characterized in that, In low-frequency mode, the dual-mode six-coil transformer couples the resonant coil L2 and the fine-tuning coil Lsw2. The coarse-tuning MOS transistor Msw3 is configured to be off, and the coarse-tuning MOS transistor Msw4 is configured to be on.

6. The dual-mode W-band voltage-controlled oscillator based on transformer magnetic tuning according to claim 5, characterized in that, The dual-mode six-coil transformer generates a four-band W-band signal.

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