Ultra-small-area four-core voltage-controlled oscillator based on folded ring transformer

Abstract

The invention belongs to the technical field of integrated circuits, and particularly relates to an ultra-small-area four-core voltage-controlled oscillator based on a folded ring transformer. The device comprises a folding ring transformer, four oscillators which are mutually coupled through a multi-channel electromagnetic synchronous network, capacitors A in the oscillators and capacitors B among the oscillators, the folded ring transformer is used as an inductive load of the oscillator, so that the occupied area of the four-core voltage-controlled oscillator can be greatly reduced, and meanwhile, a four-channel magnetic field synchronous network is provided to realize a high quality factor under differential-mode fundamental frequency and common-mode second-order harmonic waves; the capacitor A and the capacitor B can adjust the oscillation frequency, provide two additional electric field synchronization paths and form a multi-channel electromagnetic synchronization network together with the folded ring transformer so as to reduce phase noise degradation caused by frequency mismatch between cores. And the four oscillators oscillate under the same resonant frequency through the multi-channel electromagnetic synchronous network. The filter has the advantages of being ultra-small in area, low in noise, ultra-low in frequency mismatch, high in quality factor and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and in particular relates to an ultra-small area quad-core voltage-controlled oscillator based on a folded toroidal transformer. Background Art

[0002] Among low-noise harmonic oscillators, multi-core oscillators are widely used to generate low-phase-noise local oscillator signals. Multi-core oscillators have a wide range of important applications in both analog and digital circuits, ranging from high-performance phase-locked loops, RF transceivers, analog-to-digital converters, to high-speed SerDes systems, all of which require high-speed, high-quality multi-core oscillators.

[0003] For a 4-core multi-core oscillator, theoretically, it will bring 10log(4)=6dB of phase noise optimization, but at the cost of N times the power consumption and more than N times the area. In order to ensure frequency synchronization between the four oscillator cores and avoid frequency pattern ambiguity, it is necessary to introduce a frequency synchronization network to ensure that all cores oscillate at the same desired frequency.

[0004] Traditional quad-core oscillators often use a synchronization network based on resistive modules such as switches and resistors, which are built between discrete cores. This introduces large parasitics and additional area, resulting in lower frequency synchronization efficiency and degraded phase noise performance. Furthermore, each core often uses a single-coil inductor, which results in a lower quality factor when the inductance is small. The large spacing between the four cores means that the frequency modulation capacitors can only be located within each core, and the ground wires are often far from the power supply lines, making their current return paths difficult to manage and even more difficult to introduce common-mode resonance technology to improve noise performance. Previous common-mode resonance technologies either sacrificed the quality factor of common-mode resonance for high-quality fundamental frequency resonance, or used additional second-order harmonic resonant cavities at the expense of additional on-chip area. Summary of the Invention

[0005] The purpose of the present invention is to provide a quad-core oscillator based on a folded toroidal transformer with an ultra-small area, a strong frequency synchronization network, and high-quality differential and common-mode resonance, so as to solve the problems of traditional quad-core oscillators such as large area, large phase noise penalty due to frequency mismatch, and inability to achieve high-quality differential and common-mode resonance.

[0006] The ultra-small quad-core voltage-controlled oscillator provided by the present invention comprises a folded toroidal transformer, an oscillator core internal capacitor A, an oscillator core inter-capacitor B, an oscillator core 1 (101), an oscillator core 2 (102), an oscillator core 3 (103), and an oscillator core 4 (104) coupled to each other via a multi-channel electromagnetic synchronization network; wherein: The folded toroidal transformer, as the inductive load of the oscillator, is used to greatly reduce the area occupied by the quad-core voltage-controlled oscillator, while providing a four-channel magnetic field synchronization network and achieving a high quality factor at the differential mode fundamental frequency and common mode second-order harmonics; The capacitor A in the oscillator core is used to adjust the oscillation frequency and, together with the folded toroidal transformer, determines that the common mode resonance is located at the second-order harmonic frequency; The capacitor B in the oscillator core is used to adjust the oscillation frequency and, together with the folded toroidal transformer, determines that the common-mode resonance is located at the second-order harmonic frequency. At the same time, it provides two additional electric field synchronization paths and, together with the folded toroidal transformer, forms a multi-channel electromagnetic synchronization network to reduce the phase noise degradation caused by frequency mismatch between cores.

[0007] The oscillator core 1 , oscillator core 2 , oscillator core 3 and oscillator core 4 oscillate at the same resonant frequency through a multi-channel electromagnetic synchronization network, thereby realizing a quad-core voltage-controlled oscillator.

[0008] In the present invention, all four oscillator cores use the same circuit structure to generate negative resistance to offset the corresponding losses in the resonant cavity. This circuit structure can be a standard NMOS, PMOS, or CMOS cross-coupled pair, or a more complex structure such as Class-C or Class-F.

[0009] In the present invention, the folded toroidal transformer structure comprises four slice inductors connected between the drain terminals of non-adjacent cores (i.e., oscillator cores 1 and 3 form a pair of non-adjacent cores, and oscillator cores 2 and 4 form a pair of non-adjacent cores), forming a first magnetic synchronization path. Two fused source inductors connected to the in-phase source nodes between all four oscillator cores form a second magnetic synchronization path. Furthermore, magnetic coupling exists between these drain inductors and the source inductors, with the magnetic coupling between the drain inductors being stronger and the magnetic coupling between the drain and source inductors being relatively weaker. The magnetic coupling between the drain inductors corresponding to different pairs of non-adjacent cores forms a third magnetic synchronization path. The magnetic coupling between the drain inductors and the source inductors exists between both different and the same pairs of non-adjacent cores, forming a fourth magnetic synchronization path. Furthermore, since this structure can be viewed as a folded or rotated version of a toroidal slice transformer (in which inductors are connected between pairs of non-adjacent cores) in a traditional quad-core architecture, the folded toroidal transformer structure of the present invention significantly reduces the vertical or horizontal dimensions, significantly reducing the physical distance between two pairs of adjacent cores. This not only reduces the area of ​​the quad-core oscillator but also reduces parasitics in the frequency synchronization network, thereby improving the transformer's synchronization efficiency. Furthermore, the slice inductors exhibit a higher quality factor at low inductances and can be easily stretched vertically or horizontally to accommodate different inductance values, resulting in better frequency mobility. The folding (or rotation) compresses the symmetry of the layout (from three axes of symmetry: the vertical centerline, the horizontal centerline, and the diagonal line to two axes of symmetry: the vertical centerline and the horizontal centerline). This allows all active devices to be aligned in a uniform orientation, which is more conducive to meeting the DRC requirements of advanced process nodes and thus achieving better process mobility.

[0010] Furthermore, because the folded toroidal transformer significantly reduces the physical spacing between adjacent cores, it is now possible to introduce not only intra-core capacitance A within the oscillator core, but also inter-core capacitance B between adjacent oscillator cores. Inter-core capacitance B can be introduced between any two inverting drain, gate, and source terminals of a transistor in one oscillator core and another transistor in an adjacent oscillator core, acting as a drain, gate, or source capacitor. These inter-core drain, gate, or source capacitances can be implemented in a variety of ways, including but not limited to differential switched capacitor arrays, single-ended switched capacitor arrays, and fixed capacitors. These inter-core capacitances B also serve as electric field synchronization paths, further enhancing frequency synchronization between adjacent cores. Furthermore, these inter-core capacitances can also take the form of frequency-modulated switched capacitor arrays within the fundamental frequency (or higher-order harmonic) resonant cavity, thereby expanding the oscillator's frequency modulation range.

[0011] Furthermore, because the folded toroidal transformer places adjacent oscillator cores together, the currents flowing through the drain inductors in differential and common-mode modes are in the same direction and in phase. Since the magnetic currents between the two strongly coupled drain inductors of this quad-core oscillator reinforce each other during fundamental frequency resonance (both the equivalent inductance and the equivalent quality factor are increased), this leads to improvements in both the equivalent inductance and the equivalent quality factor. Therefore, the quality factor of the two coupled drain inductors of the folded toroidal transformer during common-mode resonance is also enhanced.

[0012] Furthermore, the multi-channel magnetic synchronization network obtained by the folded toroidal transformer is combined with the multi-channel electric field synchronization network obtained by the inter-core capacitance to form a powerful electromagnetic hybrid synchronization network, eliminating the phase noise degradation caused by the frequency mismatch between different cores.

[0013] Furthermore, the present invention can be fabricated using a CMOS process, a BiCMOS process, a GeSi process, or a GaAs process, including but not limited to the processes listed above. The transistors can be fabricated using bipolar transistors, junction field-effect transistors, or MOSFETs.

[0014] The present invention is based on a quad-core voltage-controlled oscillator (VCO) with a folded toroidal transformer and a multi-channel frequency synchronization network. Through a robust and powerful frequency synchronization network, the four oscillator cores are controlled at the same desired frequency, achieving high-quality differential-mode and common-mode resonance. The present invention can achieve ultra-low phase noise degradation caused by inter-core frequency mismatch, low parasitics, and high overall performance in an ultra-small area. The quad-core VCO of the present invention has an ultra-small area (a quad-core VCO with an oscillation center frequency of 17.5 GHz requires only 0.06 mm² of on-chip area), low noise (at 5 mW power consumption and a 16 GHz operating frequency, the phase noise at a 10 MHz frequency offset is -134.5 dBc / Hz), and ultra-low frequency mismatch penalty (a maximum phase noise penalty of only 0.22 dB at a 15% frequency mismatch).

[0015] Compared with the prior art, the present invention has the following significant advantages: Traditional quad-core oscillator circuits are often plagued by large phase noise penalties caused by inter-core frequency mismatch, large area, poor process and frequency compatibility, and compromises in differential and common-mode resonance quality factors. The present invention adopts a folded toroidal transformer structure, which greatly reduces the on-chip area of ​​the quad-core oscillator, resulting in better frequency mobility and inductance quality factor. Combined with the low-parasitic multi-channel electromagnetic frequency synchronization network composed of inter-core capacitors, it almost eliminates the phase noise penalty caused by inter-core frequency mismatch and improves the frequency modulation range of the quad-core oscillator. In addition, the compression of the layout freedom enables active devices in the same direction to better adapt to the DRC of advanced process nodes, and also enables common-mode resonance and differential-mode resonance to enjoy the same constructive magnetic flow, resulting in greater equivalent inductance and quality factor, and achieving better phase noise performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the circuit structure of the ultra-small quad-core voltage-controlled oscillator of the present invention.

[0017] Figure 2 The layout structure of the invented ultra-small area quad-core voltage-controlled oscillator.

[0018] Figure 3 Schematic diagram of the common-mode operation of the invented ultra-small quad-core voltage-controlled oscillator.

[0019] Figure 4 The simulation results of phase noise degradation under frequency mismatch of the invented ultra-small area quad-core voltage-controlled oscillator. DETAILED DESCRIPTION

[0020] The quad-core voltage-controlled oscillator of the present invention comprises: a folded toroidal transformer (composed of a slice-type inductor (141, 144), a fused source-end inductor (151, 154), a magnetic coupling (161, 164) between a drain-end inductor and a source-end inductor, a magnetic coupling (171, 174) between drain-end inductors, a source-end common-mode inductor (181) and a destructive magnetic coupling (191) between the source-end common-mode inductor), an oscillator core internal capacitor A (111, 114), an oscillator core inter-capacitor B (121, 122, 131, 132), a first oscillator core (101), a second oscillator core (102), a third oscillator core (103), and a fourth oscillator core (104) coupled to each other via a multi-channel electromagnetic synchronization network.

[0021] The folded toroidal transformer serves as the inductive load of the oscillator (141, 144, 151, 154, 161, 164, 171, 174, 181, 191), which greatly reduces the area occupied by the quad-core voltage-controlled oscillator, provides a four-channel magnetic field synchronization network, and also achieves high quality factors at the differential mode fundamental frequency and the common mode second-order harmonic; the capacitor A (111, 114) in the oscillator core provides the function of adjusting the oscillation frequency, and together with the folded toroidal transformer determines that the common mode resonance is located at the second-order harmonic frequency; the capacitor B (12 1, 124) provide the function of adjusting the oscillation frequency, and together with the folded toroidal transformer, determine that the common mode resonance is located at the second-order harmonic frequency. At the same time, it provides two additional electric field synchronization paths, and together with the folded toroidal transformer, it forms a multi-channel electromagnetic synchronization network, which greatly reduces the phase noise degradation caused by the frequency mismatch between the cores. Oscillator core 1 (101), oscillator core 2 (102), oscillator core 3 (103), and oscillator core 4 (104) oscillate at the same resonant frequency through the multi-channel electromagnetic synchronization network, realizing a quad-core voltage-controlled oscillator. Through this solution, a quad-core voltage-controlled oscillator with ultra-small area, low noise, and ultra-low frequency mismatch cost can be obtained.

[0022] In the present invention, the four oscillator cores are all generated by the same circuit to generate a negative resistance module to offset the corresponding loss in the resonant cavity. The negative resistance module is composed of two NMOS transistors, wherein the gate of one NMOS tube and the drain of the other NMOS tube are directly short-circuited to form a cross-coupled pair structure. Among them, the first oscillator core (101) and the second oscillator core (102) adjacent to it are short-circuited with the same phase source terminal, and the same is true for the other pair of adjacent third oscillator cores (103) and fourth oscillator cores (104).

[0023] In the present invention, the folded ring transformer structure comprises: four slice inductors (141, 144) respectively connected between the drain ends of non-adjacent cores (the first oscillator core 1 and the third oscillator core 3 form a pair of non-adjacent cores, and the second oscillator core 2 and the fourth oscillator core 4 form a pair of non-adjacent cores), forming a first magnetic synchronization path; and two fused source inductors (151, 154) connected to the same-phase source nodes between all four oscillator cores, forming a second magnetic synchronization path. In addition, there is magnetic coupling (171, 174) between these drain inductors and magnetic coupling (161, 164) between the drain inductors and the source inductors, wherein the magnetic coupling between the drain inductors is stronger and the magnetic coupling between the drain and source inductors is weaker. The magnetic coupling at the drain end exists between the drain inductors corresponding to different non-adjacent core pairs, forming a third magnetic synchronization path. The magnetic coupling between the drain inductor and the source inductor exists between different and the same non-adjacent core pairs, forming a fourth magnetic synchronization path. In addition, the folded toroidal transformer also includes a source-end common-mode transformer, which is composed of a source-end common-mode inductor (181) and a destructive magnetic coupling (191) between the source-end common-mode inductor, and can suppress the injection of common-mode noise to the ground.

[0024] In the present invention, since this structure can be regarded as a toroidal slice transformer (inductors are connected between each non-adjacent core pair) in a traditional quad-core architecture obtained by folding or rotating, the folded toroidal transformer structure of the invention greatly reduces the vertical or horizontal dimensions, so that the physical distance between two pairs of adjacent cores is greatly reduced, which not only reduces the area of ​​the quad-core oscillator, but also reduces the parasitics of the frequency synchronization network, and improves the synchronization efficiency of the transformer. Figure 2 Furthermore, chip inductors have a higher quality factor at low inductances and can be adapted to different inductance values ​​by simply stretching them vertically or horizontally, resulting in better frequency mobility. Furthermore, due to the folding (or rotational) nature of the chip inductor, the symmetry of the layout is compressed (from three axes of symmetry: the vertical centerline, the horizontal centerline, and the diagonal line to two axes of symmetry: the vertical centerline and the horizontal centerline). This allows all active components to be oriented in a unified manner, which is more conducive to meeting the DRC requirements of advanced process nodes and thus achieving better process mobility.

[0025] Furthermore, because the folded toroidal transformer significantly reduces the physical spacing between adjacent cores, it is now possible to introduce not only intra-core capacitance A within the oscillator core, but also inter-core capacitance B between adjacent oscillator cores. Inter-core capacitance B can be introduced between any two inverting drain terminals, gate terminals, and source terminals of a transistor in one oscillator core and another transistor in an adjacent oscillator core, acting as a drain-side capacitance, gate-side capacitance, or source-side capacitance. These inter-core drain-side, gate-side, or source-side capacitances can be implemented in a variety of ways, including but not limited to differential switched capacitor arrays, single-ended switched capacitor arrays, and fixed capacitors. In a specific implementation, the intra-core capacitance A (111, 114) at the drain side is implemented using differential and single-ended switched capacitor arrays, while the inter-core capacitances (121, 122) at the drain side have the same structure as the intra-core capacitance A. The inter-core capacitances (131, 132) at the source side are implemented as fixed capacitors. Inter-core capacitors B (121, 122, 131, 132) also serve as electric field synchronization paths, further enhancing frequency synchronization between adjacent cores. Furthermore, these drain-side intra-core and inter-core capacitors in this invention also exist as frequency-modulated switched capacitor arrays in the differential-mode fundamental resonant cavity and the common-mode second-order harmonic resonant cavity, thereby expanding the oscillator's frequency modulation range.

[0026] Furthermore, because the folded toroidal transformer places adjacent oscillator cores together, the directions of the currents flowing through the drain inductors in differential mode and common mode are identical and in phase. Since the magnetic flow between the two strongly coupled drain inductors of this quad-core oscillator is constructive when it resonates at the fundamental frequency, it will lead to an improvement in the equivalent inductance and equivalent quality factor. Therefore, the quality factor of the two coupled drain inductors of the folded toroidal transformer in common mode is also enhanced when it resonates at the common mode, as shown in the following example. Figure 3 As shown in FIG, when the common-mode currents flow in the same direction, the common-mode equivalent magnetic coupling coefficient is greater than 0.

[0027] Furthermore, the multi-channel magnetic synchronization network obtained by folding the toroidal transformer is combined with the multi-channel electric field synchronization network obtained by the inter-core capacitance to form a powerful electromagnetic hybrid synchronization network, which eliminates the phase noise degradation caused by the frequency mismatch between different cores. The simulation results are as follows: Figure 4 As shown in the figure, under a frequency mismatch of 10%, the phase noise penalty is only 0.16dB, while under a frequency mismatch of 15%, the phase noise penalty is only 0.22dB (the frequency mismatch exists between non-adjacent oscillation cores, that is, the first oscillation core 1 (101) and the fourth oscillation core 4 (104) have the same frequency, and the second oscillation core 2 (101) and the third oscillation core 3 (104) have the same frequency, but there is a frequency mismatch between these two groups of oscillation core pairs).

[0028] In summary, the present invention is based on a quad-core voltage-controlled oscillator consisting of a folded toroidal transformer and a multi-channel frequency synchronization network. The quad-core oscillator cores are controlled at the same desired frequency through a robust and powerful frequency synchronization network to achieve high-quality differential and common-mode resonance. The present invention can achieve ultra-low phase noise degradation caused by inter-core frequency mismatch, low parasitics, and high overall performance in an ultra-small area. Traditional quad-core oscillator circuits are usually plagued by the large phase noise penalty introduced by inter-core frequency mismatch, large area, poor process and frequency compatibility, and a compromise between differential and common-mode resonance quality factors. The present invention adopts a folded toroidal transformer structure, which greatly reduces the on-chip area of ​​the quad-core oscillator, brings better frequency mobility and inductance quality factor, and combines the low parasitic multi-channel electromagnetic frequency synchronization network composed of inter-core capacitors to almost eliminate the phase noise penalty caused by inter-core frequency mismatch, thereby improving the frequency modulation range of the quad-core oscillator. In addition, the compression of layout freedom enables active devices in all directions to better adapt to the DRC of advanced process nodes, and also enables common-mode resonance and differential-mode resonance to enjoy the same constructive magnetic current, resulting in greater equivalent inductance and quality factor, and achieving better phase noise performance.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An ultra-small area quad-core voltage-controlled oscillator based on a folded toroidal transformer, characterized in that: The invention comprises a folded toroidal transformer, an oscillator core internal capacitor A, an oscillator core inter-capacitor B, a first oscillator core, a second oscillator core, a third oscillator core, and a fourth oscillator core coupled to each other via a multi-channel electromagnetic synchronization network; wherein: The folded toroidal transformer, as the inductive load of the oscillator, is used to reduce the area occupied by the quad-core voltage-controlled oscillator, while providing a four-channel magnetic field synchronization network and achieving a high quality factor at the differential mode fundamental frequency and common mode second-order harmonics; The capacitor A in the oscillator core is used to adjust the oscillation frequency and, together with the folded toroidal transformer, determines that the common mode resonance is located at the second-order harmonic frequency; The capacitor B within the oscillator core is used to adjust the oscillation frequency and, together with the folded toroidal transformer, determines that the common-mode resonance is located at the second-order harmonic frequency. It also provides two additional electric field synchronization paths, which, together with the folded toroidal transformer, form a multi-channel electromagnetic synchronization network to reduce phase noise degradation caused by frequency mismatch between cores. The first oscillator core, the second oscillator core, the third oscillator core, and the fourth oscillator core oscillate at the same resonant frequency through a multi-channel electromagnetic synchronization network to realize a quad-core voltage-controlled oscillator; The four oscillator cores are all negative resistance modules with the same structure to offset the corresponding losses in the resonant cavity; the circuit structure is an NMOS, PMOS or CMOS cross-coupled pair, or Class-C or Class-F; The folded ring transformer structure includes: four slice inductors respectively connected between the drain ends of non-adjacent oscillator cores, which constitute the first magnetic synchronization path; two fused source inductors connected to the same-phase source end nodes between all four oscillator cores, which constitute the second magnetic synchronization path; magnetic coupling between these drain inductors and source inductors, among which the magnetic coupling between the drain inductors is stronger and the magnetic coupling between the drain and source inductors is relatively weaker; the magnetic coupling of the drain end exists between the drain inductors corresponding to different non-adjacent oscillator core pairs, which constitutes the third magnetic synchronization path; the magnetic coupling from the drain inductor to the source inductor exists simultaneously between different and the same non-adjacent oscillator core pairs, which constitutes the fourth magnetic synchronization path.

2. The ultra-small quad-core voltage-controlled oscillator according to claim 1, wherein: An intra-core capacitor A is introduced into the oscillator core, and an inter-core capacitor B is introduced between adjacent oscillator cores; the inter-core capacitor B is introduced between any two inverting drain terminals, gate terminals and source terminals of a transistor in one oscillator core and another transistor in an adjacent oscillator core, and exists as a drain capacitor, gate capacitor or source capacitor; and these inter-core drain, gate or source capacitors have the following implementation methods: differential switched capacitor array, single-ended switched capacitor array, fixed capacitor; these inter-core capacitors B also serve as electric field-type synchronization paths, further enhancing the frequency synchronization between adjacent cores; in addition, these inter-core capacitors exist in the form of a frequency modulation switched capacitor array in the fundamental frequency resonant cavity, which expands the frequency modulation range of the oscillator.

3. The ultra-small quad-core voltage-controlled oscillator according to claim 2, wherein: The folded toroidal transformer allows adjacent oscillator cores to be placed together, so that the directions of the currents flowing through the drain inductors in differential mode and common mode are identical and in phase. Since the magnetic currents between the two strongly coupled drain inductors of this quad-core oscillator are mutually reinforcing when resonating at the fundamental frequency (both the equivalent inductance value and the equivalent quality factor are increased), the equivalent inductance value and the equivalent quality factor are improved. Therefore, the quality factor of the two coupled drain inductors of the folded toroidal transformer in common mode resonance is enhanced.

4. The ultra-small quad-core voltage-controlled oscillator according to claim 3, wherein: The multi-channel magnetic synchronization network obtained by folding the toroidal transformer is combined with the multi-channel electric field synchronization network obtained by the inter-core capacitance to form a powerful electromagnetic hybrid synchronization network to eliminate the phase noise degradation caused by the frequency mismatch between different cores.

5. The ultra-small quad-core voltage-controlled oscillator according to claim 1, wherein: The folded toroidal transformer comprises two slice-type inductors (141, 144), two fused source-end inductors (151, 154), magnetic coupling (161, 164) between two drain-end inductors and a source-end inductor, magnetic coupling (171, 174) between the two drain-end inductors, a source-end common-mode inductor (181), and destructive magnetic coupling (191) between the source-end common-mode inductors. Four slice inductors (141, 144) respectively connected between the drain ends of non-adjacent oscillator cores constitute a first magnetic synchronization path; two fused source inductors (151, 154) connected to the same-phase source end nodes between all four oscillator cores constitute a second magnetic synchronization path; in addition, the magnetic coupling (171, 174) existing between these drain inductors and the magnetic coupling (161, 164) existing between the drain inductors and the source inductors, wherein the magnetic coupling of the drain end exists between the drain inductors corresponding to different non-adjacent oscillator core pairs, constitutes a third magnetic synchronization path, and the magnetic coupling from the drain inductor to the source inductor exists between different and the same non-adjacent oscillator core pairs, constitutes a fourth magnetic synchronization path; a source common mode transformer is formed by the destructive magnetic coupling (191) between the source common mode inductor (181) and the source common mode inductor, which is used to suppress the common mode noise injection to the ground.

6. The ultra-small quad-core voltage-controlled oscillator according to claim 5, wherein: The invention comprises an oscillator core internal capacitor A (111, 114), an oscillator core inter-capacitor B (121, 122, 131, 132), a first oscillator core (101), a second oscillator core (102), a third oscillator core (103), and a fourth oscillator core (104) coupled to each other via a multi-channel electromagnetic synchronization network; wherein: The capacitor A (111, 114) in the oscillator core is used to adjust the oscillation frequency and together with the folded toroidal transformer determines that the common mode resonance is located at the second-order harmonic frequency; The capacitors B (121, 124) in the oscillator core are used to adjust the oscillation frequency and determine, together with the folded toroidal transformer, that the common mode resonance is located at the second-order harmonic frequency. At the same time, two additional electric field synchronization paths are provided, and together with the folded toroidal transformer, a multi-channel electromagnetic synchronization network is formed to reduce the phase noise degradation caused by the frequency mismatch between the oscillator cores. The first oscillator core (101), the second oscillator core (102), the third oscillator core (103), and the fourth oscillator core (104) oscillate at the same resonant frequency through the multi-channel electromagnetic synchronization network to realize a quad-core voltage-controlled oscillator.

7. The ultra-small quad-core voltage-controlled oscillator according to claim 6, wherein: The four oscillator cores are all generated by the same circuit to generate a negative resistance module to offset the corresponding loss in the resonant cavity; the negative resistance module is composed of two NMOS transistors, wherein the gate of one NMOS tube and the drain of the other NMOS tube are directly short-circuited to form a cross-coupling pair structure; wherein the first oscillator core (101) and the same-phase source terminal of the adjacent second oscillator core (102) are short-circuited, and another pair of adjacent third oscillator cores (103) and fourth oscillator cores (104) are also connected in the same way.

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