CN115208319A - Millimeter wave dual-band voltage-controlled oscillator fused with local surface plasmons - Google Patents

Abstract

The invention discloses a millimeter wave dual-band voltage-controlled oscillator fused with local surface plasmons. The switch circuit is loaded at the position of the local surface plasmon gap, so that the shearing of the resistance and the resonance mode of the local surface plasmon are realized, and the frequency band of the voltage-controlled oscillator is further switched; and in each sub-frequency band, the varactor is connected with the interdigital capacitor in series to realize the function of precise frequency modulation. The invention realizes the integration of the local surface plasmon and the cross coupling circuit to form an oscillation circuit. Based on a high-quality factor resonance mechanism of the local surface plasmon, the quality factor of the whole resonant cavity of the voltage-controlled oscillator is improved.

Description

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

technical field

The invention relates to a millimeter-wave dual-band voltage-controlled oscillator, in particular to a millimeter-wave dual-band voltage-controlled oscillator with a localized surface plasmon.

Background technique

Millimeter wave communication technology has been widely used in the military field. Millimeter-wave integrated circuits are the core components of systems such as radar, remote sensing, guidance, and navigation. In the process of millimeter wave transition from military to civilian, there are still several key issues to be resolved. One of the problems is that traditional millimeter-wave integrated circuits are mostly made of GaAs and other processes to ensure their performance, so the cost is high, and it is difficult to popularize in the cost-sensitive civilian field. In addition, GaAs technology cannot achieve monolithic integration with baseband digital circuits using CMOS technology, thus complicating overall system connections.

As the feature size of the CMOS process gradually enters the nanometer level, some performance indicators of the CMOS process have approached the GaAs process. For example, the cut-off frequency of the 65nm CMOS process has exceeded 200GHz, and its device performance can meet the requirements of millimeter-wave mid-low frequency circuit design, and the manufacturing cost is far lower than that of the GaAs process.

The local oscillator signal with low phase noise is necessary for the millimeter wave transceiver system. The phase noise performance of the local oscillator has an important influence on the sensitivity and output signal-to-noise ratio of the receiver. VCO is the main source of out-of-band phase noise of PLL, so reducing the phase noise of VCO has become the focus of PLL research. In addition, when the frequency increases to millimeter wave and submillimeter wave, the Q value of passive devices decreases, and the chip interconnection will increase the load of the voltage-controlled oscillator. It is necessary to use a distributed model for calculation, and comprehensively consider all parasitic effects.

RF transceivers that can adapt to multi-mode and multi-band applications are the development trend. Although frequency multipliers, frequency dividers and mixers can be used to perform frequency changes, this requires multiple signal sources and greatly increases system functionality. Therefore, in order to efficiently obtain a multi-band local oscillator signal source, it requires the frequency synthesizer to be able to switch in different frequency bands, thereby generating dual-band/multi-band local oscillator signals.

In addition, although the ring oscillator can achieve a wider tuning range, its phase noise is far worse than that of the LC oscillator, which cannot meet the requirements of RF transceiver chips. Therefore, in the millimeter-wave frequency band, LC oscillators are usually used to achieve high-performance local oscillator signal generation.

In addition, the localized surface plasmon is a strongly resonant mode with deep subwavelength local field enhancement and high-Q resonance. Conventional localized surface plasmons are generated in the optical frequency band and can be generated by external light excitation of metal nanoparticles or microstructures. In recent years, localized surface plasmons have expanded from the optical frequency band to the far-infrared, terahertz and microwave frequency bands. The present invention intends to integrate the localized surface plasmon resonance unit on the chip in the microwave frequency band, and the primary problem faced is that the size of the localized surface plasmon polariton structure is too large, which seriously wastes the chip area. In addition, due to the thin dielectric layer of the chip, the resonance impedance peak value and quality factor of the on-chip localized surface plasmon are restricted. In addition, the localized surface plasmon structure is improved to realize the switching of different resonant frequencies under the same structure, so as to realize the output of the local oscillator signal of the dual-band VCO. Therefore, how to integrate local surface plasmons with high quality factor in microwave-band VCOs, reduce chip size, achieve dual-band frequency switching, and achieve low phase noise has become a key issue.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the present invention provides a millimeter-wave dual-band voltage-controlled oscillator integrating localized surface plasmon, which utilizes a localized surface plasmon structure with a gap to load a switch circuit, It can realize local surface plasmon resonance in different frequency bands, and has a high resonance impedance peak, so that the phase noise of the output signal of the voltage-controlled oscillator is at a low level, so as to achieve high-performance dual-band millimeter-wave voltage-controlled oscillation device. In addition, the localized surface plasmon can be directly connected with the cross-coupling circuit and the varactor branch, and the structure is compact, which reduces the chip area of the dual-band voltage-controlled oscillator and reduces the electromagnetic simulation caused by the complex interconnection. workload.

The technical solution adopted in the present invention is: a millimeter-wave dual-band voltage-controlled oscillator integrating local surface plasmon, comprising: a resonance unit, a cross-coupling circuit, a capacitor frequency modulation circuit and a switch circuit;

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

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

The localized surface plasmon includes: an inner ring part and an outer ring part, the inner ring part includes inwardly protruding interdigital pieces, and the interdigital pieces are spaced apart from each other in the circumferential direction; the outer ring part includes a ring and three taps;

the cross-coupling circuit for generating a negative conduction signal to compensate for losses in the resonance unit and the capacitive frequency modulation circuit;

The cross-coupling circuit includes: a first field effect transistor and a second field effect transistor, the sources of the first field effect transistor and the second field effect transistor are grounded, and the drain electrode of the first field effect transistor and the second field effect transistor are connected to the ground. The gate is connected, 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 the fundamental wave differential signal;

The capacitor frequency modulation circuit, connected in parallel with the cross-coupling circuit, 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, which is connected to the first feeder and the second feeder of the localized surface plasmon, and is used for fine frequency modulation in the sub-band of the voltage-controlled oscillator;

The switch circuit, connected in parallel at the gap of the outer ring of the resonance unit, is used to determine the resonance mode of the resonance unit;

The switch circuit is connected with the gap of the outer ring of the localized surface plasmon to control whether the signal of the localized surface plasmon is turned on or not at the gap;

By regulating the on-off of the switch circuit, and controlling whether the signal of the localized surface plasmon at the gap is turned on or not, the resonant mode and the resonant frequency of the resonant unit will change;

By changing the resonant mode and resonant frequency of the resonant unit, the voltage-controlled oscillator can switch the oscillation frequency of two frequency bands.

Further, 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.

Further, 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 in the surface plasmon Both sides of the inner ring inward and on the same straight line;

The inner ring interdigitated 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 in the interdigital vacancy of the inner ring;

The outer ring has two taps on the outside at the positions of the first feeding port and the second feeding port, and has one tap outside the outer ring on the other side of the first feeding port and the second feeding port symmetrically.

Further, the resonance frequency of the resonance unit is higher than the actual oscillation frequency of the millimeter-wave dual-band voltage-controlled oscillator.

Further, the varactor branch circuit includes: a first capacitor, a varactor and a first resistor, the varactor is connected in series with the fixed interdigital capacitor C1, and the first resistor is connected to the first capacitor and the varactor connected to provide a DC voltage bias at the negative port of the varactor.

Further, the oscillation frequency of the millimeter-wave dual-band voltage-controlled oscillator is adjusted by adjusting the resonant frequency of the resonance unit, the parasitic capacitance of the cross-coupling circuit, and the capacitance of the capacitance frequency modulation module.

Beneficial effects of the present invention:

1. The present invention integrates the localized surface plasmon into the voltage-controlled oscillator. The localized surface plasmon is used as a high-quality resonant unit to replace the inductance-capacitor resonant cavity of the traditional voltage-controlled oscillator, and provides cross-coupling. Tube supply voltage DC bias.

2. The resonant frequency of the localized surface plasmon is higher than the actual oscillation frequency of the VCO, which is different from the traditional inductance-capacitor resonant cavity. The higher the frequency, the lower the resonance quality factor. Due to the inherent properties of localized surface plasmons, the higher the frequency, the higher the resonance quality factor, which helps to reduce the phase noise of the voltage-controlled oscillator and improve the conversion efficiency of DC power consumption.

3. The localized surface plasmon introduces a gap, which changes the resonance mode and resonance frequency of the resonance unit, which can further reduce the resonance frequency and reduce the physical size of the resonance structure under the premise of ensuring the same resonance frequency. Helps reduce the chip area of the overall VCO.

4. The local surface plasmon adds a switch circuit at the gap, and the switch circuit realizes the on-off of the signal at the gap, so as to realize the different resonance modes of the local surface plasmon, so as to realize the dual-band millimeter wave voltage controlled oscillator.

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.

6. All centralized circuits are arranged inside the local surface plasmon, with compact structure and simple interconnection lines, which is conducive to simplifying the electromagnetic simulation process.

7. The present invention is realized by standard CMOS technology, and has the advantages of high integration and low cost.

Description of drawings

1 is a schematic structural diagram of a millimeter-wave dual-band voltage-controlled oscillator in the present invention;

2 is a schematic diagram of a localized surface plasmon structure in the present invention;

Fig. 3 is the simplified circuit of small signal of millimeter wave dual-band voltage-controlled oscillator in the present invention;

Fig. 4 is the resonance impedance frequency response curve of the localized surface plasmon with or without the outer ring gap in the present invention;

Fig. 5 is the frequency response curve of the real part of the resonance impedance loaded with different resistance value resistors at the localized surface plasmon gap in the present invention;

Fig. 6 is the frequency response curve of the imaginary part of the resonance impedance loaded with different resistance value resistors at the localized surface plasmon gap in the present invention;

7 is a frequency modulation curve of a millimeter-wave dual-band VCO in the present invention;

FIG. 8 is a phase noise curve of a millimeter-wave dual-band voltage-controlled oscillator in the present invention.

Detailed ways

For better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention. not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Referring to the millimeter wave voltage controlled oscillator shown in FIG. 1 , it includes a resonance unit I, a cross-coupling circuit II, a capacitor frequency modulation circuit III and a switch circuit IV.

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

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 feeder 3, a second feeder 4 and a localized surface plasmon.

The center tap 2 is used to connect the circuit VDD to supply power to the voltage controlled oscillator.

The first output port 7, the second output port 8, the first feeder 3 and the second feeder 4 are in a straight line.

The localized surface plasmon includes an outer ring 10 , an inwardly protruding interdigital member 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 pieces 9 . The outer ring has a notch (5, 6) at 270°. The fingers are spaced 9 from each other in the circumferential direction and are missing a unit at 270°.

The first feeder 3 and the second feeder 4 form a differential feeder, which is used to connect the cross-coupling circuit II and the capacitor frequency modulation module III.

The notches (5, 6) of the outer ring are used to connect the switch circuit (IV).

Ground plane 1 is located below the localized surface plasmon.

The cross-coupling circuit II includes a first field effect transistor M1 and a second field effect transistor M2, the sources of the first field effect transistor and the second field effect transistor are grounded, and the drain of the first field effect transistor is connected to the second field effect transistor. The gate of the transistor is connected, 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 module III includes a varactor branch.

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 and the capacitance of the capacitor frequency modulation module, the oscillation frequency in a single frequency band can be adjusted.

The switch circuit is composed 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 gaps (5, 6) of the surface plasmon are equivalently turned on. When S0 is at a low level, the switch tube is turned off, and the gaps (5, 6) of the surface plasmon are equivalent to isolation. By switching the two modes, the resonant mode switching of the surface plasmon can be regulated, so as to realize the transformation of the resonant frequency, and finally realize a dual-band millimeter-wave voltage-controlled oscillator.

As shown in Fig. 2, the resonant frequency of the localized surface plasmon is adjusted by the inner boundary radius Rs of the interdigital element 9, the radial length Rin, the width Wring of the outer ring and the interval angle θ of the interdigital element elements.

The switching circuit switches the oscillation frequency of the VCO in two different frequency bands, and the varactor is responsible for fine frequency modulation in each frequency band.

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

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

如图3为该毫米波双频段压控振荡器小信号等效电路简化模型。当开关电路为断开时，也即S0为低电平，局域表面等离激元缺口处即等效为断开，此时局域表面等离激元等效为2Rp，2Cp和R_LSP2并联。当开关电路为导通时，也即S0为高电平，局域表面等离激元缺口处即等效为导通，此时局域表面等离激元等效为Rp，Cp和R_LSP并联。通过调节局域表面等离激元的Rs,Rin,Wring和θ参数，可通过仿真确定出具体开关电路断开时的谐振频率

和开关电路导通时的谐振频率

另外谐振处的局域表面等离激元的品质因数分别为

和

因此在保证合适谐振频率，使压控振荡器在高、低频段更易起振，功耗更低，相位噪声更低，局域表面等离激元品质因数需要更高，谐振阻抗需要更高，应尽可能提高R_LSP2和R_LSP数值来提高局域表面等离激元的谐振品质因数。交叉耦合电路等效为负导-Gm与寄生电容Ceq并联，交叉耦合电路中晶体管的尺寸决定了负导和寄生电容的大小，负导越大越容易起振，输出功率越大。电容调谐电路等效为一个可变电容并联Rc，用来在初始谐振频率的基础上调节压控振荡器的输出频率。局域表面等离激元的并联网络(Lp||Cp或者2Lp||2Cp),交叉耦合电路的寄生电容Ceq，变容管电容Cvar并联电容决定了基于局域表面等离激元双频段压控振荡器的最终输出频率。According to Fig. 2, the localized surface plasmon resonance frequency ω ₀ is adjusted according to the inner boundary radius Rs of the interdigital element, the radial length Rin, the width Wring of the outer ring and the interval angle θ of the interdigital element element

Figure 3 is a simplified model of the small-signal equivalent circuit of the millimeter-wave dual-band voltage-controlled oscillator. When the switch circuit is off, that is, S0 is at low level, the localized surface plasmon gap is equivalent to disconnection. At this time, the localized surface plasmon is equivalent to 2Rp, 2Cp and R _LSP2 in parallel. When the switch circuit is turned on, that is, S0 is at a high level, the localized surface plasmon gap is equivalently turned on. At this time, the localized surface plasmon is equivalent to Rp, Cp and R _LSP . in parallel. By adjusting the Rs, Rin, Wring and θ parameters of the localized surface plasmon, the resonant frequency when the specific switching circuit is turned off 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 a suitable resonant frequency, make the voltage controlled oscillator easier to start vibration in high and low frequency bands, lower power consumption, lower phase noise, the local surface plasmon quality factor needs to be higher, and the resonance impedance needs to be higher. The values of R _LSP2 and R _LSP should be increased as much as possible to improve the resonance quality factor of the localized surface plasmon. The cross-coupling circuit is equivalent to the negative lead-Gm in parallel with the parasitic capacitance Ceq. The size of the transistor in the cross-coupling circuit determines the size of the negative lead and the parasitic capacitance. The larger the negative lead, the easier it is to start vibrating and the greater the output power. The capacitance tuning circuit is equivalent to a variable capacitance parallel Rc, which is used to adjust the output frequency of the voltage-controlled oscillator on the basis of the initial resonance frequency. The parallel network of localized surface plasmons (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 dual-band voltage based on the localized surface plasmon. The final output frequency of the controlled oscillator.

Figure 4 shows the impedance-frequency response curves of localized surface plasmons of the same size with and without notches. When the switching circuit changes from on to off, the localized surface plasmon resonance frequency drops from 441GHz to 218.5GHz. Considering the dimensional deviation of the outer ring structure at the notch, it can be concluded that the resonant frequency of the localized surface plasmon in the ideal turn-on case is twice that of the ideal turn-off case. In addition, it can be seen from Figure 4 that after the resonant frequency drops to 218.5GHz, the resonant impedance amplitude of the corresponding frequency point decreases, but considering the fixed thickness of the on-chip dielectric layer, the resonant impedance increases with the increase of frequency, The addition of a notch switch circuit to this structure reduces the resonant impedance of the localized surface plasmon within an acceptable range.

来表征局域表面等离激元的谐振处品质因数。由图6可以发现当Rslit接近OΩ或∞Ω时，谐振处的品质因数会更大，因此压控振荡器相位噪声性能会更好。由此得出结论，我们在设计开关电路中应尽可能降低导通电阻和增大关断电阻。Referring to Figures 5 and 6, the frequency response curves of the real part and the imaginary part of the impedance under the load of different resistances (Rslit) at the localized surface plasmon gap are respectively shown. The resistance Rslit at the notch should be OΩ and ∞Ω for the turn-on and turn-off of the localized surface plasmon outer ring under ideal conditions, respectively. However, in the actual switching circuit implementation, it can only be as close as possible to the ideal turn-on and turn-off. Especially in the millimeter wave or even terahertz frequency band, it is more difficult to use a simple and the same circuit structure to achieve ideal turn-on and turn-off at the same time. As shown in Figure 5, when the switch resistance at the notch is less than a certain value (such as 38Ω), the localized surface plasmon outer ring is turned on and resonates in the m=1 mode ω _on ; when the switch resistance at the notch is greater than At a certain value (eg 336Ω), the localized surface plasmon outer ring appears to be turned off, and resonates in the m=0.5 mode ω _off , and the resonant frequency is roughly ω _on =2ω _off . And in Figure 5, it can be found that when the notch resistance Rslit deviates from the ideal turn-on and turn-off conditions, the localized surface plasmon resonance impedance is decreasing, and resonance no longer occurs in the case of the intermediate resistance. This situation can also be confirmed from the variation of the impedance imaginary part of the localized surface plasmon with the notch resistance in Fig. 6: when Rslit is between 38Ω and 336Ω, the frequency response curve of the imaginary impedance part will no longer have a zero-crossing point. Additionally, we can use

to characterize the quality factor at the resonance of the localized surface plasmon. It can be found from Figure 6 that when Rslit is close to OΩ or ∞Ω, the quality factor at the resonance will be larger, so the VCO phase noise performance will be better. It is concluded from this that we should reduce the on-resistance and increase the off-resistance as much as possible in the design of the switching circuit.

In this design, the switch circuit uses the structure of a switch tube, a resistor and an inverter, and the appropriate size of the switch tube is selected. When the switch circuit is turned on and off, the resonant impedance of the local surface plasmon can satisfy the voltage-controlled oscillator start-up. conditions, and optimize the on and off resistance of the switching circuit as much as possible, improve the resonance quality factor of the localized surface plasmon, and reduce the phase noise of the millimeter-wave dual-band voltage-controlled oscillator.

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, and selects the first field effect transistor and the second field effect transistor. The size of the tube, and the equivalent negative conductance G _m and parasitic capacitance C _eq of the cross-coupling circuit are fixed.

Finally, it is determined that the resonant frequency of the localized surface plasmon is 218.5 GHz when the outer ring is turned off, and the resonant frequency when the outer ring is turned on is 441 GHz. The resonant impedance peaks are: 401.9Ω and 1048Ω, respectively. In the corresponding frequency band, the varactor fine-tuning method is used for frequency modulation. Figure 7 shows that when the switching circuit is turned on, the frequency coverage is 128.35GHz-131.74GHz. When the switch circuit is turned off, the frequency coverage is 90.29GHz-91.73GHz.

Figure 8 shows the phase noise of the fused localized surface plasmon dual-band VCO. At 131.74GHz carrier frequency, the phase noise is -82.54dBc/Hz at 1MHz frequency offset. At 91.73GHz carrier frequency, the phase noise is -90.19dBc/Hz at 1MHz frequency offset.

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, but not to limit it; although referring to the foregoing implementation The present invention has been described in detail by the examples, and those of ordinary skill in the art should understand that; it is still possible to modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements to some of the technical features; and these modifications or replacements , does not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (6)

1. A millimeter wave dual-band voltage-controlled oscillator fused with local surface plasmons comprises: the circuit comprises a resonance unit, a cross coupling circuit, a capacitance frequency modulation circuit and a switch circuit;

the resonance unit is used for providing high resonance impedance of multiple frequency bands; the resonant unit is directly connected with the cross coupling circuit through the first feeder line and the second feeder line to form an oscillating circuit; the resonance unit further comprises a local surface plasmon, and the local surface plasmon is provided with a notch at an outer ring position of 270 degrees; the localized surface plasmons include: the inner ring part comprises inward-protruding interdigital parts which are arranged at intervals in the circumferential direction; the outer ring part comprises a circular ring and three taps;

the cross-coupling circuit is used for generating a negative conducting signal to compensate for the loss in the resonance unit and the capacitance frequency modulation circuit; the cross-coupling circuit includes: the source electrodes of the first field effect tube and the second field effect tube are grounded, the drain electrode of the first field effect tube is connected with the grid electrode of the second field effect tube, and the drain electrode of the second field effect tube is connected with the grid electrode of the first field effect tube; the drain electrodes of the first field effect tube and the second field effect tube output fundamental wave differential signals;

the capacitance frequency modulation circuit is connected with the cross coupling circuit in parallel and is used for adjusting the resonant frequency of the millimeter wave dual-band voltage-controlled oscillator; the capacitance frequency modulation circuit includes: the varactor branch is connected with a first feeder line and a second feeder line of the local surface plasmon and used for fine frequency modulation in a sub-frequency band of the voltage-controlled oscillator;

the switching circuit is connected in parallel at the notch of the outer ring of the resonance unit and is used for determining the resonance mode of the resonance unit; the switch circuit is connected with the outer ring gap of the local surface plasmon and is used for controlling whether the signal of the local surface plasmon at the gap is conducted or not;

controlling whether the signal of the local surface plasmon at the notch is conducted or not by regulating the on-off of the switch circuit, and changing the resonance mode and the resonance frequency of the resonance unit;

the voltage-controlled oscillator is switched between the oscillation frequencies of the two frequency bands by changing the resonance mode and the resonance frequency of the resonance unit.

2. The local surface plasmon merged millimeter wave dual-band voltage-controlled oscillator according to claim 1, wherein the local surface plasmon further comprises: a ground plane is provided on the substrate,

the ground plane is located below the inner loop portion and the outer loop portion.

3. The local surface plasmon merged millimeter wave dual-band voltage-controlled oscillator according to claim 1, wherein the local surface plasmon further comprises a first feed port and a second feed port; the first feed port and the second feed port are respectively positioned on two inward sides of the surface plasmon inner ring and are positioned on the same straight line;

the inner ring interdigital array is provided with a unit at one symmetrical side of the first feed port and the second feed port;

the outer ring is provided with a gap at the gap of the inner ring interdigital;

the outer loop has two taps outside the outer loop at the locations of the first and second feed ports, and one tap outside the outer loop on the other side of symmetry of the first and second feed ports.

4. The local area surface plasmon fused millimeter wave dual-band voltage-controlled oscillator according to claim 1, wherein the resonance frequency of the resonance unit is higher than the actual oscillation frequency of the millimeter wave dual-band voltage-controlled oscillator.

5. The local surface plasmon fused millimeter wave dual-band voltage-controlled oscillator according to claim 1, wherein the varactor branch comprises: the variable capacitor is connected with the fixed interdigital capacitor C1 in series, and the first resistor is connected with the first capacitor and the variable capacitor to provide direct-current voltage bias at a negative port of the variable capacitor.

6. The local surface plasmon fused millimeter wave dual-band voltage-controlled oscillator according to claim 1, wherein the oscillation frequency of the millimeter wave dual-band voltage-controlled oscillator is adjusted by adjusting the resonant frequency of the resonant unit, the parasitic capacitance of the cross-coupling circuit and the capacitance of the capacitance frequency modulation module.

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