Magnetic tuning F-type voltage-controlled oscillator based on multi-coil coupling

Abstract

The invention discloses a magnetic tuning F-type voltage-controlled oscillator based on multi-coil coupling, and the oscillator comprises an F-type oscillation loop which is used for generating an oscillation signal with a required frequency, and carrying out the harmonic adjustment of a frequency spectrum of the oscillation signal; the magnetic tuning transformer is used for adjusting the voltage-current relationship of the oscillation signal in the F-type oscillation loop, changing the equivalent inductance value in the F-type oscillation loop and further adjusting the oscillation frequency; the common-mode resonant capacitor is used for determining common-mode capacitance in the F-type oscillation loop and further reducing the phase noise at the second harmonic through common-mode resonance; the F-class voltage-controlled oscillator is adopted to enhance harmonic waves to achieve frequency tripling to generate millimeter wave oscillation signals, a magnetic tuning mode is adopted to replace a varactor with a low quality factor to control and change resonant frequency, and compared with a traditional LC voltage-controlled oscillator, the voltage-controlled oscillator can obtain lower phase noise and a higher quality factor, and the performance of the voltage-controlled oscillator is improved. And an additional frequency multiplier is omitted for the generation of the millimeter wave oscillation signal.

Description

Technical Field

[0001] The invention belongs to the technical field of radio frequency integrated circuits, and in particular relates to a magnetically tuned F-class voltage-controlled oscillator based on multi-coil coupling. Background Art

[0002] With the demand for large bandwidth and high speed in emerging wireless applications, the frequency range above 100 GHz has gradually attracted great attention, such as high data rate wireless backhaul, automotive radar systems, medical imaging, etc. These applications require the generation of jitter-free and high output power local oscillator signals (LO) in a wide frequency range. However, it is challenging to generate broadband signals in the millimeter wave range. On the one hand, the influence of parasitic elements will be greater than that of inductor capacitor (LC) tanks. On the other hand, the quality factor of the varactor used to control the frequency will drop sharply in the millimeter wave range.

[0003] The Chinese invention application with announcement number CN117997275A discloses a high-efficiency harmonic voltage-controlled oscillator with dual tuning of inductor and capacitor. The increased loss of millimeter-wave passive devices is solved by a Push-Push harmonic oscillator, an active variable capacitor and a magnetically tuned inductor. Although this structure generates a high-frequency oscillation signal through a harmonic voltage-controlled oscillator (VCO), it is limited to the second harmonic.

[0004] The Chinese invention application with announcement number CN118100802A discloses a millimeter-wave frequency band three-coil coupled oscillator structure and chip, which uses a dual-core CLASS-F oscillator structure with three-coil coupling and third harmonic extraction to achieve low phase noise, but the dual-core structure results in high power consumption. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a magnetically tuned F-class voltage-controlled oscillator based on multi-coil coupling, which reduces the operating frequency of the oscillator by enhancing the harmonics of the F-class voltage-controlled oscillator, and replaces the low-quality-factor varactor for frequency tuning by magnetic tuning. Changing the ratio of differential-mode capacitance to common-mode capacitance can make the common-mode resonance at the second harmonic, preventing the quality factor from decreasing due to operation in the triode region of the transistor, and solving the technical problem of the deterioration of the phase noise of the oscillation signal caused by the reduction of the quality factor of the millimeter-wave passive device in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A magnetically tuned class-F voltage-controlled oscillator based on multi-coil coupling, comprising:

[0008] Class F oscillation loop: used to generate an oscillation signal of the required frequency and perform harmonic adjustment on the spectrum of the oscillation signal to enhance the amplitude of the third harmonic and reduce phase noise;

[0009] Magnetic tuning transformer: used to adjust the voltage-current relationship of the oscillation signal in the F-type oscillation loop, change the equivalent inductance value in the F-type oscillation loop, and then adjust the oscillation frequency;

[0010] Common-mode resonant capacitor: used to determine the common-mode capacitor in the class F oscillation loop, providing high impedance at the second harmonic frequency through the common-mode resonant frequency to further reduce phase noise;

[0011] The oscillation signal output end of the F-type oscillation loop is connected to the oscillation signal input end of the magnetic tuning transformer and the common-mode resonant capacitor respectively.

[0012] The class F oscillation loop includes a first transistor M1, a second transistor M2, a first inductor L1 of a feedback transformer, a second inductor L2 of a feedback transformer, a third capacitor C3, a fourth capacitor C4, a seventh capacitor C7, and an eighth capacitor C8; the drain of the first transistor M1 is connected to the first end of the first inductor L1 of the feedback transformer, the gate of the first transistor M1 is connected to the second end of the second inductor L2 of the feedback transformer, and the source of the first transistor M1 is connected to the ground; the drain of the second transistor M2 is connected to the second end of the first inductor L1 of the feedback transformer, the gate of the second transistor M2 is connected to the first end of the second inductor L2 of the feedback transformer, and the source of the second transistor M2 is connected to the ground; the third end of the first inductor L1 of the feedback transformer is connected to the power supply voltage V DD , the third end of the second inductor L2 of the feedback transformer is connected to the bias voltage V B ; The gate of the first transistor M1 is connected to the first end of the third capacitor C3, the second end of the third capacitor C3 is connected to the second end of the fourth capacitor C4, and the first end of the fourth capacitor C4 is connected to the gate of the second transistor M2; the drain of the first transistor M1 is connected to the first end of the seventh capacitor C7, the second end of the seventh capacitor C7 is connected to the second end of the eighth capacitor C8, and the first end of the eighth capacitor C8 is connected to the drain of the second transistor M2.

[0013] The magnetic tuning transformer comprises a third inductor L3 and a third transistor M3; a first end of the third inductor L3 is connected to the drain of the third transistor M3, and a second end of the third inductor L3 is connected to the ground; a gate of the third transistor M3 is connected to a frequency control voltage V CTRL , the source of the third transistor M3 is connected to the ground.

[0014] The common-mode resonant capacitor includes a first capacitor C1, a second capacitor C2, a fifth capacitor C5, and a sixth capacitor C6; a first end of the first capacitor C1 is connected to the gate of the first transistor M1, and a second end of the first capacitor C1 is connected to the ground; a first end of the second capacitor C2 is connected to the gate of the second transistor M2, and a second end of the second capacitor C2 is connected to the ground; a first end of the fifth capacitor C5 is connected to the drain of the first transistor M1, and a second end of the fifth capacitor C5 is connected to the ground; a first end of the sixth capacitor C6 is connected to the drain of the second transistor M2, and a second end of the sixth capacitor C6 is connected to the ground.

[0015] There is a coupling coefficient K1 between the first inductor L1 of the feedback transformer and the second inductor L2 of the feedback transformer, there is a coupling coefficient K2 between the first inductor L1 of the feedback transformer and the third inductor L3 of the magnetic tuning transformer, there is a coupling coefficient K3 between the second inductor L2 of the feedback transformer and the third inductor L3 of the magnetic tuning transformer, and the coupling coefficient K2 is equal to the coupling coefficient K3.

[0016] The first transistor M1 , the second transistor M2 and the third transistor M3 are all N-type metal-oxide-semiconductor field effect transistors.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention sets up a class F oscillation loop to generate an oscillation signal of a desired frequency, and performs harmonic adjustment on the spectrum of the oscillation signal to enhance the amplitude of the third harmonic and reduce phase noise. The stronger third harmonic can easily generate a higher frequency signal through frequency tripling.

[0019] 2. The present invention sets a magnetic tuning transformer to adjust the voltage-current relationship of the oscillation signal in the F-type oscillation loop, changes the equivalent inductance value in the F-type oscillation loop, and then adjusts the oscillation frequency, thereby avoiding the use of a varactor with a poor quality factor in the structure of variable capacitance frequency adjustment.

[0020] 3. The present invention sets a common-mode capacitor to adjust the common-mode resonance so that the common-mode resonance is at the second harmonic, thereby preventing the first transistor and the second transistor from working in the triode region to reduce the overall quality factor of the oscillator. Compared with the explicit common-mode resonance, the implicit common-mode resonance eliminates the additional inductance, which helps to miniaturize the chip area.

[0021] In summary, compared with the traditional LC voltage-controlled oscillator, the overall circuit of the present invention adopts a class F voltage-controlled oscillator to enhance harmonics to achieve frequency tripling to generate a millimeter-wave oscillation signal, and uses magnetic tuning to replace the low-quality factor varactor to control and change the resonant frequency, which can obtain lower phase noise and higher quality factor, and eliminates the need for an additional frequency multiplier for the generation of millimeter-wave oscillation signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a magnetically tuned F-class voltage-controlled oscillator based on multi-coil coupling provided by the present invention.

[0023] Figure 2 It is a schematic diagram of the principle of the Class F voltage-controlled oscillator provided by the present invention.

[0024] Figure 3 It is a schematic diagram of the principle of transformer coupled magnetic tuning provided by the present invention.

[0025] Figure 4 It is a transient simulation schematic diagram provided by the present invention.

[0026] Figure 5 It is a schematic diagram of phase noise simulation provided by the present invention.

[0027] Figure 6 It is a schematic diagram of tuning frequency simulation provided by the present invention.

[0028] Figure 7 It is a schematic diagram of phase noise simulation under 1 MHz frequency offset provided by the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0030] like Figure 1 As shown, a magnetically tuned class-F voltage-controlled oscillator based on multi-coil coupling comprises:

[0031] Class F oscillation loop: used to generate an oscillation signal of the required frequency and perform harmonic adjustment on the spectrum of the oscillation signal to enhance the amplitude of the third harmonic and reduce phase noise;

[0032] Magnetic tuning transformer: used to adjust the voltage-current relationship of the oscillation signal in the F-type oscillation loop, obtain the equivalent inductance value in the F-type oscillation loop, and then adjust the oscillation frequency;

[0033] Common-mode resonant capacitor: used to determine the common-mode capacitor in the class F oscillation loop, providing high impedance at the second harmonic frequency through the common-mode resonant frequency to further reduce phase noise;

[0034] The oscillation signal output end of the F-type oscillation loop is connected to the oscillation signal input end of the magnetic tuning transformer and the common-mode resonant capacitor respectively.

[0035] The class F oscillation loop includes a first transistor M1, a second transistor M2, a first inductor L1 of a feedback transformer, a second inductor L2 of a feedback transformer, a third capacitor C3, a fourth capacitor C4, a seventh capacitor C7, and an eighth capacitor C8; the drain of the first transistor M1 is connected to the first end of the first inductor L1 of the feedback transformer, the gate of the first transistor M1 is connected to the second end of the second inductor L2 of the feedback transformer, and the source of the first transistor M1 is connected to the ground; the drain of the second transistor M2 is connected to the second end of the first inductor L1 of the feedback transformer, the gate of the second transistor M2 is connected to the first end of the second inductor L2 of the feedback transformer, and the source of the second transistor M2 is connected to the ground. The first transistor M1 and the second transistor M2 amplify the loop signal to offset the loss caused by the parasitics of the passive components; the third end of the first inductor L1 of the feedback transformer is connected to the power supply voltage V DD , the third end of the second inductor L2 of the feedback transformer is connected to the bias voltage V B ; The gate of the first transistor M1 is connected to the first end of the third capacitor C3, the second end of the third capacitor C3 is connected to the second end of the fourth capacitor C4, and the first end of the fourth capacitor C4 is connected to the gate of the second transistor M2; the drain of the first transistor M1 is connected to the first end of the seventh capacitor C7, the second end of the seventh capacitor C7 is connected to the second end of the eighth capacitor C8, and the first end of the eighth capacitor C8 is connected to the drain of the second transistor M2; the frequency selection network composed of passive devices determines the oscillation frequency of the oscillator, and the high-order resonant network based on the feedback transformer can enhance the harmonic components of the oscillation signal through multi-impedance peaks.

[0036] The magnetic tuning transformer comprises a third inductor L3 and a third transistor M3; a first end of the third inductor L3 is connected to the drain of the third transistor M3, and a second end of the third inductor L3 is connected to the ground; a gate of the third transistor M3 is connected to a frequency control voltage V CTRL , the source of the third transistor M3 is connected to the ground, and the voltage V is controlled by controlling the frequency CTRL By changing the channel resistance of the third transistor M3, the voltage-current relationship of the oscillation signal flowing through the first inductor L1 and the second inductor L2 of the feedback transformer is adjusted, and the equivalent inductance value of the first inductor L1 and the second inductor L2 of the feedback transformer is changed, thereby adjusting the oscillation frequency.

[0037] The common-mode resonant capacitor includes a first capacitor C1, a second capacitor C2, a fifth capacitor C5, and a sixth capacitor C6; the first end of the first capacitor C1 is connected to the gate of the first transistor M1, and the second end of the first capacitor C1 is connected to the ground; the first end of the second capacitor C2 is connected to the gate of the second transistor M2, and the second end of the second capacitor C2 is connected to the ground; the first end of the fifth capacitor C5 is connected to the drain of the first transistor M1, and the second end of the fifth capacitor C5 is connected to the ground; the first end of the sixth capacitor C6 is connected to the drain of the second transistor M2, and the second end of the sixth capacitor C6 is connected to the ground; the common-mode resonant capacitor is to change a part of the capacitor in the F-type oscillation loop into a common-mode access mode, and implicit common-mode resonance can be achieved by changing the proportion of common-mode capacitors in the capacitors, thereby further reducing phase noise.

[0038] There is a coupling coefficient K1 between the first inductor L1 and the second inductor L2 of the feedback transformer, there is a coupling coefficient K2 between the first inductor L1 of the feedback transformer and the third inductor L3 of the magnetic tuning transformer, there is a coupling coefficient K3 between the second inductor L2 of the feedback transformer and the third inductor L3 of the magnetic tuning transformer, and the optimal coupling coefficient is determined according to the actual implementation of the feedback transformer and the magnetic tuning transformer.

[0039] The first transistor M1 , the second transistor M2 and the third transistor M3 are all N-type metal-oxide-semiconductor field effect transistors.

[0040] like Figure 2 As shown in the schematic diagram of the F-type voltage-controlled oscillator part provided in this embodiment, the fundamental frequency resonates at 77 GHz and the third harmonic resonates at 231 GHz. According to the calculation of the transformer impedance, the two resonant frequencies ω1 and ω2 can be derived respectively:

[0041]

[0042] Wherein, L1 and L2 are the inductance values ​​of the first inductor coil and the second inductor coil of the feedback transformer respectively, C1 and C2 are the parallel capacitance values ​​of the first inductor coil and the second inductor coil of the feedback transformer respectively, and K1 is the coupling coefficient of the first inductor coil and the second inductor coil of the feedback transformer;

[0043] Then the ratio of the two resonant frequencies ω1 and ω2 is obtained as:

[0044]

[0045] Combined with the impedance peaks R at the two resonant frequencies ω1 and ω2 p1 and R p2 , respectively:

[0046]

[0047] Wherein, Q1 and Q2 are the quality factors of the first inductor L1 and the second inductor L2 of the feedback transformer, respectively. Taking Q1=Q2 and ω2 / ω1=3, we can obtain:

[0048]

[0049] The coupling coefficient and the inductance and capacitance at the set harmonic amplitude can be obtained, and the device parameters can be determined by scanning and optimizing the coupling coefficient. From the above analysis, it can be seen that the inductance ratio needs to remain unchanged after the coupling coefficient and capacitance of the feedback transformer are determined.

[0050] According to the Leeson model, the empirical formula for phase noise is:

[0051]

[0052] Among them, Q is the quality factor of the oscillator as a whole, k is the Boltzmann constant, T is the absolute temperature, P is the power of the oscillator, ω f is the corner frequency where the flicker noise component dominates, ω m is the frequency offset, ω0 is the oscillation frequency, and F is the noise factor;

[0053] The Q value is usually lower than the quality factor of the resonant cavity. The formula explains the relationship between the quality factor and phase noise, that is, in order to reduce the phase noise, the quality factor needs to be increased, and the magnetic tuning transformer ( Figure 3 (as shown) can avoid the use of varactor tubes with poor quality factors in the millimeter wave band to achieve frequency control.

[0054] like Figure 3 As shown, the principle diagram of the magnetic tuning transformer part provided in this embodiment can be equivalent to an equivalent inductance L 1eff Its parasitic resistance R 1eff Concatenate and get:

[0055]

[0056] Wherein, L represents the first inductor L1 or the second inductor L2 of the feedback transformer, R represents the parasitic resistance corresponding to the first inductor L1 or the second inductor L2, L eff represents the equivalent inductance of the first inductor L1 or the second inductor L2, R eff represents the equivalent parasitic resistance of the first inductor L1 or the second inductor L2, K represents the coupling coefficient between the first inductor L1 or the second inductor L2 and the third inductor L3 of the magnetic tuning transformer respectively; R V is the channel resistance of the third transistor M3, and controls the voltage V CTRLAnd change, R3 is the parasitic resistance corresponding to the third inductor L3, M represents the mutual inductance between the first inductor L1 or the second inductor L2 and the third inductor L3 of the feedback transformer; combined with the above derivation, when the coupling coefficients of the first inductor L1 and the second inductor L2 with the third inductor L3 respectively satisfy K2=K3, it can be achieved in the process of controlling the oscillation frequency to meet L 1eff / L 2eff The conditions remain unchanged.

[0057] In an optional embodiment of the present invention, a simulation experiment is used to further illustrate the present invention.

[0058] Simulation conditions:

[0059] The SMIC40nm CMOS process model is used, the power supply voltage is 1.1V, the gate bias voltage is 0.7V, the oscillation frequency is set at 78GHz, and the Cadence simulation tool is used to simulate it.

[0060] Simulation content:

[0061] Simulation 1: Under the above conditions, the output signal of the magnetically tuned class F voltage-controlled oscillator circuit proposed in the present invention is simulated. Figure 4 , Figure 4 is a schematic diagram of a transient simulation provided by an embodiment of the present invention, wherein V D is the voltage signal of the drain of the first transistor M1 and the second transistor M2; Figure 4 It can be seen that the drain output signals of the first transistor M1 and the second transistor M2 are close to square waves after harmonic shaping, and can be easily tripled in frequency through filtering.

[0062] Simulation 2: Under the above conditions, the phase noise of the magnetically tuned class F voltage-controlled oscillator circuit proposed in the present invention is simulated. Figure 5 , Figure 5 is a schematic diagram of phase noise simulation provided by an embodiment of the present invention, Figure 5 It can be seen that the phase noise is -93.9dBc / Hz at a 1MHz frequency offset from the 78GHz oscillation frequency.

[0063] Simulation 3, under the above conditions, the frequency control voltage V of the magnetically tuned class F voltage-controlled oscillator circuit proposed by the present invention is CTRL To scan, see Figure 6 and Figure 7 , Figure 6 is a schematic diagram of a tuning frequency simulation provided by an embodiment of the present invention, Figure 7 is a schematic diagram of phase noise simulation under 1 MHz frequency offset provided by an embodiment of the present invention, Figure 6It can be seen that the voltage-controlled oscillator without a varactor in this embodiment can cover a range of 1 GHz; Figure 7 It can be seen that the phase noise range is -95.89dBc / Hz to -92.86dBc / Hz at a 1MHz frequency offset.

Claims

1. A magnetically tuned class F voltage-controlled oscillator based on multi-coil coupling, characterized in that: include: Class F oscillation loop: used to generate an oscillation signal of the required frequency and perform harmonic adjustment on the spectrum of the oscillation signal to enhance the amplitude of the third harmonic and reduce phase noise; Magnetic tuning transformer: used to adjust the voltage-current relationship of the oscillation signal in the F-type oscillation loop, change the equivalent inductance value in the F-type oscillation loop, and then adjust the oscillation frequency; Common-mode resonant capacitor: used to determine the common-mode capacitor in the class F oscillation loop, providing high impedance at the second harmonic frequency through the common-mode resonant frequency to further reduce phase noise; The oscillation signal output end of the F-type oscillation loop is connected to the oscillation signal input end of the magnetic tuning transformer and the common-mode resonant capacitor respectively.

2. The magnetically tuned class-F voltage-controlled oscillator based on multi-coil coupling according to claim 1, characterized in that: The class F oscillation loop comprises a first transistor (M1), a second transistor (M2), a first inductor (L1) of a feedback transformer, a second inductor (L2) of a feedback transformer, a third capacitor (C3), a fourth capacitor (C4), a seventh capacitor (C7), and an eighth capacitor (C8); the drain of the first transistor (M1) is connected to the first end of the first inductor (L1) of the feedback transformer, the gate of the first transistor (M1) is connected to the second end of the second inductor (L2) of the feedback transformer, and the source of the first transistor M1 is connected to the ground; the drain of the second transistor (M2) is connected to the second end of the first inductor (L1) of the feedback transformer, the gate of the second transistor (M2) is connected to the first end of the second inductor (L2) of the feedback transformer, and the source of the second transistor (M2) is connected to the ground; the third end of the first inductor (L1) of the feedback transformer is connected to a power supply voltage (V DD ), the third end of the second inductor (L2) of the feedback transformer is connected to the bias voltage (V B ); the gate of the first transistor (M1) is connected to the first end of the third capacitor (C3), the second end of the third capacitor (C3) is connected to the second end of the fourth capacitor (C4), and the first end of the fourth capacitor (C4) is connected to the gate of the second transistor (M2); the drain of the first transistor (M1) is connected to the first end of the seventh capacitor (C7), the second end of the seventh capacitor (C7) is connected to the second end of the eighth capacitor (C8), and the first end of the eighth capacitor (C8) is connected to the drain of the second transistor (M2).

3. The magnetically tuned class-F voltage-controlled oscillator based on multi-coil coupling according to claim 1, characterized in that: The magnetic tuning transformer comprises a third inductor (L3) and a third transistor (M3); a first end of the third inductor (L3) is connected to a drain of the third transistor (M3), and a second end of the third inductor (L3) is connected to ground; a gate of the third transistor (M3) is connected to a frequency control voltage (V CTRL ), the source of the third transistor (M3) is connected to ground.

4. The magnetically tuned class-F voltage-controlled oscillator based on multi-coil coupling according to claim 1, characterized in that: The common-mode resonant capacitor comprises a first capacitor (C1), a second capacitor (C2), a fifth capacitor (C5), and a sixth capacitor (C6); a first end of the first capacitor (C1) is connected to the gate of the first transistor (M1), and a second end of the first capacitor (C1) is connected to the ground; a first end of the second capacitor (C2) is connected to the gate of the second transistor (M2), and a second end of the second capacitor (C2) is connected to the ground; a first end of the fifth capacitor (C5) is connected to the drain of the first transistor (M1), and a second end of the fifth capacitor (C5) is connected to the ground; a first end of the sixth capacitor (C6) is connected to the drain of the second transistor (M2), and a second end of the sixth capacitor (C6) is connected to the ground.

5. The magnetically tuned class-F voltage-controlled oscillator based on multi-coil coupling according to claim 1, characterized in that: There is a coupling coefficient K1 between the first inductor (L1) of the feedback transformer and the second inductor (L2) of the feedback transformer, there is a coupling coefficient K2 between the first inductor (L1) of the feedback transformer and the third inductor (L3) of the magnetic tuning transformer, there is a coupling coefficient K3 between the second inductor (L2) of the feedback transformer and the third inductor (L3) of the magnetic tuning transformer, and the coupling coefficient K2 is equal to the coupling coefficient K3.

6. The magnetically tuned class-F voltage-controlled oscillator based on multi-coil coupling according to claim 1, characterized in that: The first transistor (M1), the second transistor (M2) and the third transistor (M3) are all N-type metal-oxide-semiconductor field effect transistors.

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