A magnetically tuned class F voltage-controlled oscillator based on multi-coil coupling

Abstract

The present invention discloses a magnetically tuned class-F voltage-controlled oscillator based on multi-coil coupling, comprising: a class-F oscillation loop, for generating an oscillation signal of a desired frequency and performing harmonic adjustment on the spectrum of the oscillation signal; a magnetically tuned transformer, for adjusting the voltage-current relationship of the oscillation signal in the class-F oscillation loop, changing the equivalent inductance value in the class-F oscillation loop, and thereby adjusting the oscillation frequency; and a common-mode resonant capacitor, for determining the common-mode capacitance in the class-F oscillation loop, and further reducing phase noise at the second harmonic through common-mode resonance. The present invention uses 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 a low-quality-factor varactor to control and change the resonant frequency. Compared with a traditional LC voltage-controlled oscillator, the voltage-controlled oscillator of the present invention can obtain lower phase noise and higher quality factor, and eliminates the need for an additional frequency multiplier for generating millimeter-wave oscillation signals.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency integrated circuit technology, specifically relating to a magnetically tuned Class F voltage-controlled oscillator based on multi-coil coupling. Background Technology

[0002] With the growing demand for high bandwidth and high speed in emerging wireless applications, frequency ranges above 100 GHz are attracting increasing attention. Applications such as high-data-rate wireless backhaul, automotive radar systems, and medical imaging require the generation of jitter-free and high-output-power local oscillator (LO) signals over a wide frequency range. However, generating broadband signals in the millimeter-wave range is challenging. Firstly, parasitic elements have a greater impact than inductors and capacitors (LC) slots. Secondly, the quality factor of varactors used to control and regulate the frequency drops sharply in the millimeter-wave range.

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

[0004] Chinese invention application CN118100802A discloses a millimeter-wave band three-coil coupled oscillator structure and chip. It adopts a dual-core CLASS-F oscillator structure with three-coil coupling and extraction of the third harmonic to achieve low phase noise, but the power consumption is relatively large due to the use of dual-core structure. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a magnetically tuned Class F voltage-controlled oscillator based on multi-coil coupling. This oscillator reduces its operating frequency by enhancing harmonics through a Class F voltage-controlled oscillator, and uses magnetic tuning to replace the low-quality-factor varactor tube for frequency tuning. Changing the ratio of differential-mode capacitance to common-mode capacitance allows common-mode resonance to occur at the second harmonic, preventing quality-factor degradation caused by transistor operation. This solves the technical problem of deteriorated oscillation signal phase noise due to reduced quality factor in millimeter-wave passive devices in the prior art.

[0006] To achieve the above objectives, 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 oscillating loop: Used to generate an oscillating signal at the desired frequency and to harmonic modulate the spectrum of the oscillating 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 a Class F oscillation loop, change the equivalent inductance value in the Class F oscillation loop, and thus adjust the oscillation frequency;

[0010] Common-mode resonant capacitor: Used to determine the common-mode capacitance in a Class F oscillating loop. It provides high impedance at the second harmonic frequency through the common-mode resonant frequency, further reducing phase noise.

[0011] The oscillation signal output terminal of the Class F oscillation loop is connected to the oscillation signal input terminals of the magnetically tuned 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 coil L1 of a feedback transformer, a second inductor coil 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 terminal of the first inductor coil L1, the gate of the first transistor M1 is connected to the second terminal of the second inductor coil L2 of the feedback transformer, and the source of the first transistor M1 is connected to ground. The drain of the second transistor M2 is connected to the second terminal of the first inductor coil L1 of the feedback transformer, the gate of the second transistor M2 is connected to the first terminal of the second inductor coil L2 of the feedback transformer, and the source of the second transistor M2 is connected to ground. The third terminal of the first inductor coil L1 of the feedback transformer is connected to the power supply voltage V. DD The third terminal 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 terminal of the third capacitor C3, the second terminal of the third capacitor C3 is connected to the second terminal of the fourth capacitor C4, and the first terminal 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 terminal of the seventh capacitor C7, the second terminal of the seventh capacitor C7 is connected to the second terminal of the eighth capacitor C8, and the first terminal of the eighth capacitor C8 is connected to the drain of the second transistor M2.

[0013] The magnetically tuned transformer includes a third inductor L3 and a third transistor M3; the first end of the third inductor L3 is connected to the drain of the third transistor M3, and the second end of the third inductor L3 is connected to ground; the gate of the third transistor M3 is connected to the frequency control voltage V. CTRL The source of the third transistor M3 is connected to 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; the first terminal of the first capacitor C1 is connected to the gate of the first transistor M1, and the second terminal of the first capacitor C1 is connected to ground; the first terminal of the second capacitor C2 is connected to the gate of the second transistor M2, and the second terminal of the second capacitor C2 is connected to ground; the first terminal of the fifth capacitor C5 is connected to the drain of the first transistor M1, and the second terminal of the fifth capacitor C5 is connected to ground; the first terminal of the sixth capacitor C6 is connected to the drain of the second transistor M2, and the second terminal of the sixth capacitor C6 is connected to ground.

[0015] There is a coupling coefficient K1 between the first inductor L1 and the second inductor L2 of the feedback transformer, a coupling coefficient K2 between the first inductor L1 and the third inductor L3 of the magnetically tuned transformer, and a coupling coefficient K3 between the second inductor L2 and the third inductor L3 of the magnetically tuned transformer, and the coupling coefficients K2 and K3 are equal.

[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. This invention sets up an F-class oscillation loop to generate an oscillation signal of the desired frequency, and performs harmonic modulation on the spectrum of the oscillation signal to enhance the amplitude of the third harmonic, reduce phase noise, and the stronger third harmonic can easily generate a higher frequency signal through a third harmonic.

[0019] 2. This invention uses a magnetically tuned transformer to adjust the voltage-current relationship of the oscillation signal in the Class F oscillation loop, thereby changing the equivalent inductance value in the Class F oscillation loop and adjusting the oscillation frequency. This avoids the use of varactor tubes with poor quality factors in variable capacitor frequency adjustment structures.

[0020] 3. This invention uses a common-mode capacitor to adjust the common-mode resonance, so that the common-mode resonance is at the second harmonic, preventing the first and second transistors from operating in the transistor region and reducing the overall quality factor of the oscillator. Compared with explicit common-mode resonance, implicit common-mode resonance eliminates the need for an additional inductor, which helps to reduce the chip area.

[0021] In summary, compared with traditional LC voltage-controlled oscillators, the overall circuit of this invention uses a Class F voltage-controlled oscillator to enhance harmonics and achieve third-harmonic generation of millimeter-wave oscillation signals. It also uses magnetic tuning instead of a low-quality-factor varactor tube to control and change the resonant frequency, which can achieve lower phase noise and higher quality factor, and eliminates the need for an additional frequency multiplier for the generation of millimeter-wave oscillation signals. Attached Figure Description

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

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

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

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

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

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

[0028] Figure 7 This is a simulation diagram of phase noise under a 1MHz frequency offset provided by the present invention. Detailed Implementation

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

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

[0031] Class F oscillating loop: Used to generate an oscillating signal at the desired frequency and to harmonic modulate the spectrum of the oscillating 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 a Class F oscillation loop, obtain the equivalent inductance value in the Class F oscillation loop, and thus adjust the oscillation frequency;

[0033] Common-mode resonant capacitor: Used to determine the common-mode capacitance in a Class F oscillating loop. It provides high impedance at the second harmonic frequency through the common-mode resonant frequency, further reducing phase noise.

[0034] The oscillation signal output terminal of the Class F oscillation loop is connected to the oscillation signal input terminals of the magnetically tuned 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 coil L1 of a feedback transformer, a second inductor coil 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 terminal of the first inductor coil L1, the gate of the first transistor M1 is connected to the second terminal of the second inductor coil L2 of the feedback transformer, and the source of the first transistor M1 is connected to ground. The drain of the second transistor M2 is connected to the second terminal of the first inductor coil L1 of the feedback transformer, the gate of the second transistor M2 is connected to the first terminal of the second inductor coil L2 of the feedback transformer, and the source of the second transistor M2 is connected to ground. The first transistor M1 and the second transistor M2 amplify the loop signal and compensate for the parasitic losses caused by passive components. The third terminal of the first inductor coil L1 of the feedback transformer is connected to the power supply voltage V. DD The third terminal 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 terminal of the third capacitor C3, the second terminal of the third capacitor C3 is connected to the second terminal of the fourth capacitor C4, and the first terminal 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 terminal of the seventh capacitor C7, the second terminal of the seventh capacitor C7 is connected to the second terminal of the eighth capacitor C8, and the first terminal 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 multiple impedance peaks.

[0036] The magnetically tuned transformer includes a third inductor L3 and a third transistor M3; the first end of the third inductor L3 is connected to the drain of the third transistor M3, and the second end of the third inductor L3 is connected to ground; the gate of the third transistor M3 is connected to the frequency control voltage V. CTRL The source of the third transistor M3 is connected to 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, thereby changing the equivalent inductance values ​​of the first inductor L1 and the second inductor L2 of the feedback transformer, and thus 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 terminal of the first capacitor C1 is connected to the gate of the first transistor M1, and the second terminal of the first capacitor C1 is connected to ground. The first terminal of the second capacitor C2 is connected to the gate of the second transistor M2, and the second terminal of the second capacitor C2 is connected to ground. The first terminal of the fifth capacitor C5 is connected to the drain of the first transistor M1, and the second terminal of the fifth capacitor C5 is connected to ground. The first terminal of the sixth capacitor C6 is connected to the drain of the second transistor M2, and the second terminal of the sixth capacitor C6 is connected to ground. The common-mode resonant capacitor is essentially a portion of the capacitor in the Class F oscillation loop converted to common-mode access. By changing the proportion of the common-mode capacitor, implicit common-mode resonance can be achieved, 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, a coupling coefficient K2 between the first inductor L1 of the feedback transformer and the third inductor L3 of the magnetically tuned transformer, and a coupling coefficient K3 between the second inductor L2 of the feedback transformer and the third inductor L3 of the magnetically tuned transformer. The optimal coupling coefficients are determined based on the actual implementation of the feedback transformer and the magnetically tuned 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 Class F voltage-controlled oscillator provided in this embodiment, the fundamental frequency resonance is 77GHz, and the third harmonic resonance is 231GHz. Based on the transformer impedance calculation, the two resonant frequencies ω1 and ω2 can be derived as follows:

[0041]

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

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

[0044]

[0045] Combined with the impedance peak R at the two resonant frequencies ω1 and ω2 p1 and R p2 They are respectively:

[0046]

[0047] Where 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 that frequency can be obtained based on the set harmonic amplitude. The device parameters can be determined by scanning and optimizing the coupling coefficient. As can be seen from the above analysis, the ratio of inductance must 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] Where Q is the overall quality factor of the oscillator, k is the Boltzmann constant, T is the absolute temperature, P is the power of the oscillator, and ω f ω is the corner frequency where the flicker noise component dominates. m Where ω0 is the frequency offset, F is the oscillation frequency, and F is the noise factor.

[0053] The Q value is typically lower than the quality factor of the resonant cavity. The formula illustrates the relationship between the quality factor and phase noise; that is, to reduce phase noise, the quality factor needs to be increased, which is achieved through a magnetically tuned transformer (…). Figure 3 As shown, this can avoid using varactor diodes with poor quality factors in the millimeter-wave band to achieve frequency control.

[0054] like Figure 3 As shown in the schematic diagram of the magnetically tuned transformer section provided in this embodiment, it can be equivalent to the equivalent inductance L. 1eff Its parasitic resistance R 1eff Connect them in series and obtain:

[0055]

[0056] Where L represents the first inductor L1 or the second inductor L2 of the feedback transformer, and R represents the parasitic resistance corresponding to the first inductor L1 or the second inductor L2. eff R represents the equivalent inductance of either the first inductor L1 or the second inductor L2. eff R represents the equivalent parasitic resistance of the first inductor L1 or the second inductor L2, and K represents the coupling coefficient between the first inductor L1 or the second inductor L2 and the third inductor L3 of the magnetically tuned transformer, respectively; V The channel resistance of the third transistor M3 is controlled by the frequency-dependent voltage V. CTRLThe change is that R3 is the parasitic resistance corresponding to the third inductor L3, and M represents the mutual inductance between the first inductor L1 or the second inductor L2 and the third inductor L3 of the feedback transformer. Combining the above derivation, when the coupling coefficients of the first inductor L1 and the second inductor L2 with the third inductor L3 satisfy K2 = K3, the condition L3 can be satisfied during the control of the oscillation frequency. 1eff / L 2eff The conditions remain unchanged.

[0057] In an optional embodiment of the present invention, simulation experiments are used to further illustrate the invention.

[0058] Simulation conditions:

[0059] The SMIC 40nm CMOS process model was used, with a power supply voltage of 1.1V, a gate bias voltage of 0.7V, and an oscillation frequency of 78GHz. The model was simulated using the Cadence simulation tool.

[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 this invention is simulated. Please refer to [link to simulation]. Figure 4 , Figure 4 This is a schematic diagram of a transient simulation provided in an embodiment of the present invention, wherein V D The voltage signal is the drain voltage of the first transistor M1 and the second transistor M2; by 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 by filtering.

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

[0063] Simulation 3: Under the above conditions, the frequency control voltage V of the magnetically tuned F-type voltage-controlled oscillator circuit proposed in this invention is... CTRL To perform a scan, please refer to [link / reference]. Figure 6 and Figure 7 , Figure 6 This is a schematic diagram of a tuning frequency simulation provided in an embodiment of the present invention. Figure 7 This is a schematic diagram of phase noise simulation at a 1MHz frequency offset provided in an embodiment of the present invention. Figure 6It can be seen that the varactor-free voltage-controlled oscillator of this embodiment can cover a range of 1 GHz; from Figure 7 It can be seen that the phase noise range at a frequency offset of 1MHz is -95.89dBc / Hz to -92.86dBc / Hz.

Claims

1. A magnetically tuned Class F voltage-controlled oscillator based on multi-coil coupling, characterized in that, include: Class F oscillating loop: Used to generate an oscillation signal of the desired frequency and to harmonic modulate the spectrum of the oscillation signal to enhance the amplitude of the third harmonic and reduce phase noise; the Class F oscillating loop includes a first transistor (M1), a second transistor (M2), a first inductor coil (L1) of a feedback transformer, a second inductor coil (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 terminal of the first inductor coil (L1) of the feedback transformer, the gate of the first transistor (M1) is connected to the second terminal of the second inductor coil (L2) of the feedback transformer, and the source of the first transistor (M1) is connected to ground; the drain of the second transistor (M2) is connected to the second terminal of the first inductor coil (L1) of the feedback transformer, the gate of the second transistor (M2) is connected to the first terminal of the second inductor coil (L2) of the feedback transformer, and the source of the second transistor (M2) is connected to ground; the third terminal of the first inductor coil (L1) of the feedback transformer is connected to the power supply voltage (V). DD The third terminal 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 terminal of the third capacitor (C3), the second terminal of the third capacitor (C3) is connected to the second terminal of the fourth capacitor (C4), and the first terminal 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 terminal of the seventh capacitor (C7), the second terminal of the seventh capacitor (C7) is connected to the second terminal of the eighth capacitor (C8), and the first terminal of the eighth capacitor (C8) is connected to the drain of the second transistor (M2); Magnetic tuning transformer: Used to adjust the voltage-current relationship of the oscillation signal in a Class F oscillation loop, changing the equivalent inductance value in the Class F oscillation loop, thereby adjusting the oscillation frequency; the magnetic tuning transformer includes a third inductor (L3) and a third transistor (M3); the first end of the third inductor (L3) is connected to the drain of the third transistor (M3), and the second end of the third inductor (L3) is connected to ground; the gate of the third transistor (M3) is connected to the frequency control voltage (V). CTRL The source of the third transistor (M3) is connected to ground; Common-mode resonant capacitor: Used to determine the common-mode capacitance in a Class F oscillating loop. It provides high impedance at the second harmonic frequency through the common-mode resonant frequency, further reducing phase noise. The oscillation signal output terminal of the Class F oscillation loop is connected to the oscillation signal input terminal of the magnetically tuned transformer and the common-mode resonant capacitor, respectively; there is a coupling coefficient K1 between the first inductor coil (L1) and the second inductor coil (L2) of the feedback transformer, a coupling coefficient K2 between the first inductor coil (L1) and the third inductor coil (L3) of the magnetically tuned transformer, and a coupling coefficient K3 between the second inductor coil (L2) and the third inductor coil (L3) of the magnetically tuned transformer, and the coupling coefficients K2 and K3 are equal.

2. 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 includes a first capacitor (C1), a second capacitor (C2), a fifth capacitor (C5), and a sixth capacitor (C6). The first terminal of the first capacitor (C1) is connected to the gate of the first transistor (M1), and the second terminal of the first capacitor (C1) is connected to ground. The first terminal of the second capacitor (C2) is connected to the gate of the second transistor (M2), and the second terminal of the second capacitor (C2) is connected to ground. The first terminal of the fifth capacitor (C5) is connected to the drain of the first transistor (M1), and the second terminal of the fifth capacitor (C5) is connected to ground. The first terminal of the sixth capacitor (C6) is connected to the drain of the second transistor (M2), and the second terminal of the sixth capacitor (C6) is connected to ground.

3. A 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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