A millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmons

Abstract

The present invention discloses a millimeter-wave dual-band voltage-controlled oscillator that integrates localized surface plasmons. The millimeter-wave dual-band voltage-controlled oscillator includes a localized surface plasmon with a notch, a cross-coupling active circuit, a capacitor frequency modulation circuit, and a switching circuit. A switching circuit is loaded at the notch of the localized surface plasmon to achieve resistance shearing, the resonant mode of the localized surface plasmon, and thus switch the frequency band of the voltage-controlled oscillator; in each sub-band, a varactor is connected in series with an interdigital capacitor to achieve a precise frequency modulation function. The present invention integrates the localized surface plasmon and the cross-coupling circuit into one to form an oscillation circuit. Based on the high-quality resonance mechanism of the localized surface plasmon, the quality factor of the overall resonant cavity of the voltage-controlled oscillator is improved.

Description

Technical Field

[0001] The present invention relates to a millimeter wave dual-band voltage-controlled oscillator, and in particular to a millimeter wave dual-band voltage-controlled oscillator of localized surface plasmon. Background Art

[0002] Millimeter-wave communication technology has been widely adopted in the military. Millimeter-wave integrated circuits are core components of radar, remote sensing, guidance, and navigation systems. Several key issues remain to be addressed in the transition of millimeter-wave technology from military to civilian use. One challenge is that traditional millimeter-wave integrated circuits are mostly manufactured using processes such as GaAs to ensure high performance, resulting in high costs and limited adoption in the cost-sensitive civilian sector. Furthermore, GaAs processes cannot be monolithically integrated with baseband digital circuits using CMOS processes, complicating overall system connectivity.

[0003] As CMOS process feature sizes gradually approach the nanometer scale, some performance indicators of CMOS processes are approaching those of GaAs processes. For example, the cutoff frequency of the 65nm CMOS process has exceeded 200GHz, and its device performance can meet the requirements of millimeter-wave mid- and low-frequency circuit design, while also having a manufacturing cost far lower than that of GaAs processes.

[0004] Low-phase-noise local oscillator signals are essential for millimeter-wave transceiver systems. The LO's phase noise performance significantly impacts receiver sensitivity and output signal-to-noise ratio. The voltage-controlled oscillator (VCO) is the primary source of out-of-band phase noise in phase-locked loops (PLLs), making reducing VCO phase noise a key research priority. Furthermore, as frequencies rise to millimeter and submillimeter wave frequencies, the Q factor of passive components decreases, and chip interconnects and other factors increase the VCO's load. Therefore, a distributed model must be used for calculations, comprehensively accounting for all parasitic effects.

[0005] RF transceivers that can adapt to multi-mode and multi-band applications are a development trend. Although frequency changes can be performed with the help of frequency multipliers, dividers, and mixers, this requires multiple signal sources and also greatly increases system power consumption. Therefore, in order to efficiently obtain multi-band local oscillator signal sources, a frequency synthesizer must be able to switch between different frequency bands to generate dual-band / multi-band local oscillator signals.

[0006] While ring oscillators can achieve a wide tuning range, their phase noise is far worse than that of LC oscillators and cannot meet the requirements of RF transceiver chips. Therefore, LC oscillators are often used to achieve high-performance local oscillator signal generation in the millimeter wave band.

[0007] Furthermore, localized surface plasmons (LSPs) are a strong resonant mode characterized by deep subwavelength local field enhancement and high-Q resonance. Traditional LSPs are generated in the optical frequency band and can be generated by externally excited metal nanoparticles or microstructures. In recent years, LSPs have expanded from the optical frequency band to the far-infrared, terahertz, and microwave bands. The present invention proposes integrating LSP resonant units onto a chip in the microwave frequency band. The primary challenge is the excessive size of the LSP structure, which significantly wastes chip area. Furthermore, due to the thinness of the chip dielectric layer, the peak impedance and quality factor of the on-chip LSP resonant impedance are both limited. Furthermore, improvements to the LSP structure are being made to enable switching between different resonant frequencies within the same structure, thereby realizing dual-band voltage-controlled oscillator (VCO) local oscillator signal output. Therefore, how to integrate high-quality LSPs into microwave-frequency VCOs, reduce chip size, achieve dual-band frequency switching, and achieve low phase noise, has become a key issue. Summary of the Invention

[0008] To address the shortcomings of the prior art, the present invention provides a millimeter-wave dual-band voltage-controlled oscillator (VCO) that integrates localized surface plasmons (LSPs). By utilizing a notched LSP structure loaded with a switching circuit, the LSPs can resonate in different frequency bands with a high peak resonant impedance, resulting in low phase noise in the VCO output signal, thus realizing a high-performance dual-band millimeter-wave VCO. Furthermore, the LSPs can be directly connected to the cross-coupling circuit and the varactor branch, resulting in a compact structure that reduces the chip area of ​​the dual-band VCO and reduces the electromagnetic simulation workload caused by complex interconnects.

[0009] The technical solution adopted by the present invention is: a millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmons, comprising: a resonant unit, a cross-coupling circuit, a capacitor frequency modulation circuit, and a switching circuit;

[0010] The resonant unit is used to provide high resonant impedance in multiple frequency bands; it includes a first feeder and a second feeder, and the resonant unit is directly connected to the cross-coupling circuit through the first feeder and the second feeder to form an oscillation loop;

[0011] The resonant unit further includes a localized surface plasmon, and the localized surface plasmon has a gap at 270° of the outer ring;

[0012] The localized surface plasmon includes an inner ring portion and an outer ring portion, wherein the inner ring portion includes inwardly protruding interdigital elements, and the interdigital elements are arranged at intervals in the circumferential direction; the outer ring portion includes a circular ring and three taps;

[0013] The cross-coupling circuit is used to generate a negative conduction signal to compensate for the losses in the resonant unit and the capacitive frequency modulation circuit;

[0014] The cross-coupling circuit includes: a first field effect transistor and a second field effect transistor, wherein the sources of the first field effect transistor and the second field effect transistor are grounded, the drain of the first field effect transistor is connected to the gate of the second field effect transistor, and the drain of the second field effect transistor is connected to the gate of the first field effect transistor; the drains of the first field effect transistor and the second field effect transistor output fundamental wave differential signals;

[0015] The capacitor frequency modulation circuit is connected in parallel with the cross-coupling circuit and is used to adjust the resonant frequency of the millimeter-wave dual-band voltage-controlled oscillator;

[0016] The capacitor frequency modulation circuit includes: a varactor branch connected to a first feed line and a second feed line of the localized surface plasmon, and used for fine frequency modulation within a sub-band of the voltage-controlled oscillator;

[0017] The switch circuit is connected in parallel to the gap of the outer ring of the resonance unit and is used to determine the resonance mode of the resonance unit;

[0018] The switch circuit is connected to the outer ring gap of the localized surface plasmon and is used to control whether the signal of the localized surface plasmon at the gap is turned on or off;

[0019] By regulating the on / off of the switch circuit, the conduction of the signal of the localized surface plasmon at the gap is controlled, and the resonant mode and resonant frequency of the resonant unit are changed;

[0020] By changing the resonance mode and the resonance frequency of the resonance unit, the voltage-controlled oscillator can switch the oscillation frequency of the dual frequency bands.

[0021] Furthermore, the localized surface plasmon further includes: a ground plane, and the ground plane is located below the inner ring portion and the outer ring portion.

[0022] Furthermore, the localized surface plasmon further includes a first feeding port and a second feeding port; the first feeding port and the second feeding port are respectively located on both sides of the inner circle of the surface plasmon and are on the same straight line;

[0023] The inner ring interdigital array has one unit vacant on the symmetrical side of the first feeding port and the second feeding port;

[0024] The outer ring has a gap where the inner ring's interdigitated fingers are missing;

[0025] The outer ring has two taps outside the first feeding port and the second feeding port, and has a tap outside the outer ring on the other side symmetrical to the first feeding port and the second feeding port.

[0026] Furthermore, the resonant frequency of the resonant unit is higher than the actual oscillation frequency of the millimeter-wave dual-band voltage-controlled oscillator.

[0027] Furthermore, the varactor branch includes: a first capacitor, a varactor and a first resistor. The varactor is connected in series with the fixed interdigital capacitor C1. The first resistor is connected to the first capacitor and the varactor to provide a DC voltage bias to the negative port of the varactor.

[0028] Furthermore, the oscillation frequency of the millimeter-wave dual-band voltage-controlled oscillator is adjusted by regulating the resonant frequency of the resonant unit, the parasitic capacitance of the cross-coupling circuit, and the capacitance of the capacitive frequency modulation module.

[0029] Beneficial effects of the present invention:

[0030] 1. The present invention integrates localized surface plasmons into a voltage-controlled oscillator. The localized surface plasmons serve as a high-quality resonant unit, replacing the inductor-capacitor resonant cavity of a traditional voltage-controlled oscillator and providing a DC bias for the power supply voltage of a cross-coupled tube.

[0031] 2. The LSPP resonant frequency is higher than the actual oscillation frequency of the voltage-controlled oscillator (VCO). Unlike traditional inductor-capacitor resonant cavities, the higher the frequency, the lower the resonant quality factor. Due to the inherent properties of LSPPs, the higher the frequency, the higher the resonant quality factor. This helps reduce the VCO's phase noise and improve DC power conversion efficiency.

[0032] 3. The localized surface plasmon introduces a gap, thereby changing the resonant mode and resonant frequency of the resonant unit, which can further reduce the resonant frequency. While ensuring the same resonant frequency, the physical size of the resonant structure is reduced, which helps to reduce the chip area of ​​the overall voltage-controlled oscillator.

[0033] 4. A switching circuit is added to the gap of the localized surface plasmon to realize the signal on and off at the gap through the switching circuit, thereby realizing different resonance modes of the localized surface plasmon, thereby realizing a dual-band millimeter-wave voltage-controlled oscillator.

[0034] 5. The capacitor frequency modulation part uses a varactor in series with a fixed interdigital capacitor, which helps to improve the quality factor of the varactor branch and improve the phase noise of the voltage-controlled oscillator.

[0035] 6. All centralized circuits are arranged inside the localized surface plasmon, with a compact structure and simple interconnections, which helps to simplify the electromagnetic simulation process.

[0036] 7. The present invention is implemented using standard CMOS technology and has the advantages of high integration and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1This is a schematic diagram of the structure of the millimeter-wave dual-band voltage-controlled oscillator in the present invention;

[0038] Figure 2 Schematic diagram of the localized surface plasmon structure in the present invention;

[0039] Figure 3 This is a simplified small signal circuit for the millimeter-wave dual-band voltage-controlled oscillator in the present invention;

[0040] Figure 4 The resonant impedance frequency response curve of the localized surface plasmon with and without an outer ring gap in the present invention;

[0041] Figure 5 The real part frequency response curve of the resonant impedance when resistors with different resistance values ​​are loaded at the localized surface plasmon gap in the present invention;

[0042] Figure 6 The frequency response curve of the imaginary part of the resonant impedance when resistors of different resistance values ​​are loaded at the localized surface plasmon gap in the present invention;

[0043] Figure 7 is the frequency modulation curve of the millimeter wave dual-band voltage-controlled oscillator in the present invention;

[0044] Figure 8 This is the phase noise curve of the millimeter-wave dual-band voltage-controlled oscillator in the present invention. DETAILED DESCRIPTION

[0045] For better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0046] refer to Figure 1 The millimeter-wave voltage-controlled oscillator shown includes a resonance unit I, a cross-coupling circuit II, a capacitor frequency modulation circuit III and a switch circuit IV.

[0047] A resonance unit I is used to provide high resonance impedance in multiple frequency bands; a cross-coupling circuit II is used to generate a negative conduction signal to compensate for losses in the resonance unit I and the capacitor frequency modulation circuit III; the capacitor frequency modulation circuit III is connected in parallel with the cross-coupling circuit II and is used to adjust the resonant frequency of the millimeter-wave dual-band voltage-controlled oscillator; a switching circuit IV is connected in parallel at the gap (5, 6) of the resonance unit and is used to determine the resonant mode of the resonance unit; the resonance unit includes a first feed line 3 and a second feed line 4, and the resonance unit is directly connected to the cross-coupling circuit II through the first feed line 3 and the second feed line 4 to form an oscillation circuit.

[0048] The resonance unit 1 includes a ground plane 1, a center tap 2, a first output port 7, a second output port 8, a first feed line 3, a second feed line 4 and a localized surface plasmon.

[0049] The center tap 2 is used to connect the circuit VDD to power the voltage-controlled oscillator.

[0050] The first output port 7 , the second output port 8 , the first feeder line 3 and the second feeder line 4 are on a straight line.

[0051] The localized surface plasmon includes an outer ring 10 and inwardly protruding interdigital elements 9. The outer ring connects the center tap 2, the first output port 7, the second output port 8, and all the inwardly protruding interdigital elements 9. The outer ring has a gap (5, 6) at 270°. The interdigital elements are spaced apart from each other in the circumferential direction by 9, and a unit is missing at 270°.

[0052] The first feed line 3 and the second feed line 4 constitute a differential feed line, which is used to connect the cross-coupling circuit II and the capacitor frequency modulation module III.

[0053] The gaps (5, 6) of the outer ring are used to connect the switch circuit (IV).

[0054] The ground plane 1 is located below the LSPP.

[0055] Cross-coupling circuit II includes a first field-effect transistor (M1) and a second field-effect transistor (M2). The sources of the first and second field-effect transistors are grounded, the drain of the first field-effect transistor is connected to the gate of the second field-effect transistor, and the drain of the second field-effect transistor is connected to the gate of the first field-effect transistor. The drains of the first and second field-effect transistors output fundamental differential signals.

[0056] The capacitor frequency modulation module III includes a varactor branch.

[0057] The varactor branch is composed of a first capacitor C1, a varactor Cvar, and a first resistor R1. By adjusting the resonant frequency of the localized surface plasmon, the capacitance of the capacitor frequency modulation module adjusts the oscillation frequency within a single frequency band.

[0058] The switching circuit consists of a switch tube M3, a second resistor R2, and an inverter INV1. When SO is at a high level, the switch tube is turned on, and the surface plasmon gaps (5, 6) are equivalent to being conductive. When S0 is at a low level, the switch tube is turned off, and the surface plasmon gaps (5, 6) are equivalent to being isolated. By switching between the two modes, the resonant mode switching of the surface plasmon can be controlled, thereby achieving a change in resonant frequency, ultimately realizing a dual-band millimeter-wave voltage-controlled oscillator.

[0059] like Figure 2 As shown, the resonant frequency of the localized surface plasmon is adjusted by the inner boundary radius Rs, radial length Rin, outer ring width Wring and the spacing angle θ of the interdigital element 9.

[0060] The switching circuit switches the oscillation frequency of the voltage-controlled oscillator between two different frequency bands, and the varactor is responsible for fine frequency modulation within each frequency band.

[0061] The method of integrating localized surface plasmons into a voltage-controlled oscillator in the present invention is not limited to this specific design, but can be extended to other related fields of passive devices and active circuits.

[0062] The principle of the millimeter-wave dual-band voltage-controlled oscillator is given below.

[0063] according to Figure 2 As shown, the localized surface plasmon resonance frequency ω0 is adjusted by the inner boundary radius Rs, radial length Rin, outer ring width Wring and the spacing angle θ of the interdigital element unit. like Figure 3 This is the simplified model of the small signal equivalent circuit of the millimeter wave dual-band voltage-controlled oscillator. When the switch circuit is disconnected, that is, S0 is low, the localized surface plasmon gap is equivalent to being disconnected. At this time, the localized surface plasmon is equivalent to 2Rp, 2Cp and R LSP2 When the switch circuit is on, that is, S0 is high, the localized surface plasmon gap is equivalent to being on. At this time, the localized surface plasmon is equivalent to Rp, Cp and R LSP By adjusting the Rs, Rin, Wring and θ parameters of the localized surface plasmon, the resonant frequency when the specific switch circuit is disconnected can be determined through simulation. and the resonant frequency when the switching circuit is turned on In addition, the quality factors of the localized surface plasmons at the resonance are and Therefore, in order to ensure the appropriate resonant frequency, make the voltage-controlled oscillator easier to start in the high and low frequency bands, lower power consumption, lower phase noise, the localized surface plasmon quality factor needs to be higher, the resonant impedance needs to be higher, and R should be increased as much as possible. LSP2 and R LSP The resonant quality factor of the LSPM is improved by adjusting the value. The cross-coupling circuit is equivalent to a negative conductance -Gm in parallel with a parasitic capacitance Ceq. The size of the transistors in the cross-coupling circuit determines the magnitude of the negative conductance and parasitic capacitance. A larger negative conductance allows for easier oscillation and greater output power. The capacitor tuning circuit is equivalent to a variable capacitor in parallel with Rc, which is used to adjust the output frequency of the voltage-controlled oscillator based on the initial resonant frequency. The parallel network of LSPMs (Lp||Cp or 2Lp||2Cp), the parasitic capacitance Ceq of the cross-coupling circuit, and the parallel capacitance of the varactor capacitance Cvar determine the final output frequency of the dual-band LSPM-based voltage-controlled oscillator.

[0064] Figure 4 The impedance frequency response curves of LSPMs with and without gaps of the same size are shown. When the switch circuit changes from on to off, the LSPM resonant frequency drops from 441 GHz to 218.5 GHz. Considering the dimensional deviation of the outer ring structure at the gap, it can be concluded that the LSPM resonant frequency in the ideal on state is twice that in the ideal off state. In addition, from Figure 4 It can be seen that after the resonant frequency drops to 218.5 GHz, the resonant impedance amplitude of the corresponding frequency point decreases. However, considering that the thickness of the on-chip dielectric layer is fixed, the resonant impedance increases with increasing frequency. The addition of a gap switch circuit in this structure reduces the resonant impedance of the localized surface plasmon to an acceptable range.

[0065] refer to Figure 5 , 6 are the frequency response curves of the real and imaginary impedances when different resistances (Rslit) are loaded at the gap of the localized surface plasmon. Under ideal conditions, the resistance Rslit at the gap should be 0Ω and ∞Ω when the outer ring of the localized surface plasmon is turned on and off respectively. However, in the actual implementation of the switching circuit, it can only be as close to the ideal on and off as possible. Especially in the millimeter wave or even terahertz frequency band, it is more difficult to use the same simple circuit structure to achieve relatively ideal on and off at the same time. Figure 5 As shown in Figure 2, when the switch resistance at the gap is less than a certain value (such as 38Ω), the outer ring of the localized surface plasmon behaves as a conducting state and resonates in the m=1 mode ω. on When the switch resistance at the gap is greater than a certain value (such as 336Ω), the LSPP outer ring behaves as turned off and resonates in the m=0.5 mode ω off , and the resonant frequency is roughly expressed as ωon =2ω off . And in Figure 5 It can be found that when the gap resistance Rslit deviates from the ideal on and off conditions, the localized surface plasmon resonance impedance decreases, and resonance no longer occurs in the case of the intermediate resistance value. Figure 6 The change of the imaginary part of the impedance of the localized surface plasmon with the gap resistance can also confirm this situation: when Rslit is between 38Ω and 336Ω, the frequency response curve of the imaginary part of the impedance will no longer have a zero crossing. In addition, we can use To characterize the quality factor of the localized surface plasmon at resonance. Figure 6 It can be found that when Rslit approaches 0Ω or ∞Ω, the quality factor at resonance will be larger, and thus the voltage-controlled oscillator phase noise performance will be better. From this, we can conclude that when designing a switching circuit, we should minimize the on-resistance and increase the off-resistance as much as possible.

[0066] In this design, the switching circuit uses a structure of switching tubes, resistors, and inverters. The appropriate size of the switching tube is selected so that the resonant impedance of the localized surface plasmon when the switching circuit is turned on and off meets the starting conditions of the voltage-controlled oscillator. The on- and off-resistance of the switching circuit are optimized as much as possible to improve the resonant quality factor of the localized surface plasmon and reduce the phase noise of the millimeter-wave dual-band voltage-controlled oscillator.

[0067] In some embodiments, the first field effect transistor M1 and the second field effect transistor M2 are both NMOS transistors. Based on the 40nm CMOS process, the present invention simulates and optimizes the above circuit structure, selects the size of the first field effect transistor and the second field effect transistor, and fixes the negative conduction G equivalent to the cross-coupling circuit. m and parasitic capacitance C eq .

[0068] The final resonant frequency of the LSPP with the outer loop turned off was determined to be 218.5 GHz, and with the outer loop turned on, it was 441 GHz. The peak resonant impedances were 401.9 Ω and 1048 Ω, respectively. Varactor fine-tuning was used within the corresponding frequency bands for frequency modulation. Figure 7 The display shows that when the switch circuit is on, the frequency range is 128.35GHz-131.74GHz. When the switch circuit is off, the frequency range is 90.29GHz-91.73GHz.

[0069] Figure 8 The phase noise of a dual-band voltage-controlled oscillator (VCO) fused with localized surface plasmons is shown. At a 131.74 GHz carrier frequency and a 1 MHz offset, the phase noise is -82.54 dBc / Hz. At a 91.73 GHz carrier frequency and a 1 MHz offset, the phase noise is -90.19 dBc / Hz.

[0070] Finally, it should be noted that the millimeter-wave dual-band voltage-controlled oscillator disclosed in the embodiment of the present invention is only a preferred embodiment of the present invention and is only used to illustrate the technical solution of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmons, comprising: Resonant unit, cross-coupling circuit, capacitor frequency modulation circuit and switching circuit; The resonant unit is used to provide high resonant impedance in multiple frequency bands; The device comprises a first feed line and a second feed line, wherein a resonant unit is directly connected to the cross-coupling circuit via the first feed line and the second feed line to form an oscillation loop; the resonant unit further comprises a localized surface plasmon, wherein the localized surface plasmon has a notch at 270° of the outer ring; the localized surface plasmon comprises an inner ring portion and an outer ring portion, wherein the inner ring portion comprises inwardly protruding interdigital members, wherein the interdigital members are spaced apart from each other in the circumferential direction; and the outer ring portion comprises a circular ring and three taps; The cross-coupling circuit is configured to generate a negative conduction signal to compensate for losses in the resonant unit and the capacitor frequency modulation circuit. The cross-coupling circuit includes: a first field effect transistor and a second field effect transistor, wherein the sources of the first field effect transistor and the second field effect transistor are grounded, the drain of the first field effect transistor is connected to the gate of the second field effect transistor, and the drain of the second field effect transistor is connected to the gate of the first field effect transistor; the drains of the first field effect transistor and the second field effect transistor output a fundamental wave differential signal; The capacitor frequency modulation circuit is connected in parallel with the cross-coupling circuit and is used to adjust the resonant frequency of the millimeter-wave dual-band voltage-controlled oscillator; the capacitor frequency modulation circuit includes: a varactor branch connected to the first feed line and the second feed line of the localized surface plasmon, and is used for fine frequency modulation within the sub-band of the voltage-controlled oscillator; The switch circuit is connected in parallel to the gap of the outer ring of the resonant unit to determine the resonant mode of the resonant unit; the switch circuit is connected to the gap of the outer ring of the localized surface plasmon to control whether the signal of the localized surface plasmon at the gap is turned on or off; By regulating the on / off of the switch circuit, the conduction of the signal of the localized surface plasmon at the gap is controlled, and the resonant mode and resonant frequency of the resonant unit are changed; By changing the resonance mode and the resonance frequency of the resonance unit, the voltage-controlled oscillator can switch the oscillation frequency of the dual frequency bands.

2. The millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmons according to claim 1, characterized in that: The localized surface plasmon further includes: a ground plane, The ground contact surface is located below the inner ring portion and the outer ring portion.

3. The millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmons according to claim 1, characterized in that: The localized surface plasmon further includes a first feeding port and a second feeding port; the first feeding port and the second feeding port are respectively located on both sides of the inner circle of the surface plasmon and are on the same straight line; The inner ring interdigital array has one unit vacant on the symmetrical side of the first feeding port and the second feeding port; The outer ring has a gap where the inner ring's interdigitated fingers are missing; The outer ring has two taps outside the first feeding port and the second feeding port, and has a tap outside the outer ring on the other side symmetrical to the first feeding port and the second feeding port.

4. The millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmons according to claim 1, characterized in that: The resonant frequency of the resonant unit is higher than the actual oscillation frequency of the millimeter-wave dual-band voltage-controlled oscillator.

5. The millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmons according to claim 1, characterized in that: The varactor branch includes: a first capacitor, a varactor and a first resistor. The varactor is connected in series with the fixed interdigital capacitor C1. The first resistor is connected to the first capacitor and the varactor to provide a DC voltage bias to the negative port of the varactor.

6. The millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmons according to claim 1, characterized in that: The oscillation frequency of the millimeter-wave dual-band voltage-controlled oscillator is adjusted by regulating the resonant frequency of the resonant unit, the parasitic capacitance of the cross-coupling circuit, and the capacitance of the capacitive frequency modulation circuit.

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