Dual-mode oscillator based on artificial surface plasmon

Abstract

The invention discloses an artificial surface plasmon-based dual-mode oscillator, which comprises a resonance unit, a switching circuit and a differential circuit, and is characterized in that the resonance unit comprises a first metal ring and a second metal ring which are concentric, the inner ring of the first metal ring is connected with a plurality of first metal grid bars facing the second metal ring, and the inner ring of the second metal ring is connected with a plurality of second metal grid bars facing the second metal ring; a plurality of first metal grid bars facing the first metal ring are connected to the outer ring of the first metal ring, a plurality of second metal grid bars facing the first metal ring are connected to the outer ring of the second metal ring, the first metal grid bars and the second metal grid bars are arranged at intervals, a first notch is formed in the first metal ring, a second notch is formed in the position, corresponding to the first notch, of the second metal ring, and a third notch is formed in the position, 180 degrees away from the second notch, of the second metal ring. The two ends of the differential circuit are connected with the two ends of the first gap respectively and used for outputting differential excitation signals, and the two ends of the switching circuit are connected with the two ends of the third gap respectively and used for achieving the switching function, so that the modes of the dual-mode oscillator are switched. The invention has the advantages of wide frequency modulation range and low phase noise, and can be realized on a chip.

Description

Technical Field

[0001] The invention relates to an oscillator, in particular to a dual-mode oscillator based on artificial surface plasmons. Background Art

[0002] An oscillator is a commonly used device on a chip that is used to generate high-frequency AC signals. The oscillator can convert DC energy into AC energy for output without external signal excitation. The voltage-controlled oscillator can adjust the oscillation frequency of the oscillator by introducing an external voltage control signal.

[0003] The voltage-controlled oscillator is an important module in the millimeter-wave wireless communication system. Its phase noise and frequency modulation range directly affect the performance of the communication system. In the millimeter-wave communication transceiver chip, the LC voltage-controlled oscillator is often used to generate a high-performance local oscillator signal. The traditional LC voltage-controlled oscillator uses a variable capacitor to achieve frequency tuning and thereby widen the frequency modulation range. Variable capacitors are often implemented using varactors and switched capacitors. However, in the millimeter-wave frequency band, variable capacitors will introduce significant losses and deteriorate the phase noise of the voltage-controlled oscillator. The larger the variable capacitor, the larger the frequency modulation range of the voltage-controlled oscillator, but the more serious the degradation of its phase noise performance. Therefore, it is difficult to implement a millimeter-wave voltage-controlled oscillator with a wide frequency modulation range and low phase noise on chip.

[0004] On the other hand, artificial surface plasmon is a new type of artificial electromagnetic medium. The intersection of this electromagnetic medium and the dielectric can generate electromagnetic waves similar to surface plasmons. Artificial localized surface plasmon is a type of artificial surface plasmon. Artificial localized surface plasmon resonance is a resonance generated by periodic slotted metamaterial structure, which can be regarded as caused by standing waves generated when artificial localized surface plasmon propagates on the surface of metamaterial metal structure. Artificial localized surface plasmon resonance can be tuned by adjusting the metal structure of the metamaterial. The emergence of ultra-thin artificial localized surface plasmon makes it easier to integrate artificial localized surface plasmon on printed circuit boards and chips. Summary of the invention

[0005] In view of the problems existing in the prior art, an object of the present invention is to provide a dual-mode oscillator based on artificial surface plasmons which has a wide frequency modulation range and low phase noise and can be implemented on a chip.

[0006] In order to achieve the above-mentioned purpose of the invention, the dual-mode oscillator based on artificial surface plasmon provided by the present invention includes a resonance unit, a switching circuit, and a differential circuit, wherein the resonance unit includes a concentric first metal ring and a second metal ring, the second metal ring is located inside the first metal ring, the inner ring of the first metal ring is connected to a plurality of first metal bars facing the second metal ring, the outer ring of the second metal ring is connected to a plurality of second metal bars facing the first metal ring, the first metal bars and the second metal bars are arranged at intervals, a first notch is provided on the first metal ring, a second notch is provided on the second metal ring at a position corresponding to the first notch, and a third notch is provided at a position 180 degrees different from the second notch, two ends of the differential circuit are respectively connected to two ends of the first notch for outputting a differential excitation signal, and two ends of the switching circuit are respectively connected to two ends of the third notch for realizing a switching function, thereby switching the mode of the dual-mode oscillator.

[0007] Furthermore, the first metal bars extend inwardly along the diameter direction of the first metal ring, and the second metal bars extend outwardly along the diameter direction of the second metal ring. The first metal bars are arranged at equal intervals in the circumferential direction, and the second metal bars are arranged at equal intervals in the circumferential direction. There are gaps between the first metal bars and the second metal bars, and the gaps between all the first metal bars and the second metal bars are consistent. The second metal ring lacks a second metal bar in the second gap and the third gap respectively.

[0008] Furthermore, the differential circuit includes a capacitor structure circuit and an active tube structure circuit in parallel, the capacitor structure circuit is a circuit equivalent to a capacitor, the active tube structure circuit is a circuit equivalent to a negative conductance, and both ends of the capacitor structure circuit and both ends of the active tube structure circuit are respectively connected to both ends of the first notch.

[0009] Furthermore, the capacitor structure circuit is specifically a combination of any one or more of a fixed capacitor, an adjustable capacitor, and a switch capacitor. The capacitor structure circuit specifically includes a first adjustable capacitor, a second adjustable capacitor, and a switch capacitor array, wherein the switch capacitor array controls the switch through an input digital control signal to adjust the oscillation frequency, the second end of the first adjustable capacitor and the first end of the second adjustable capacitor are both connected to an adjustable control voltage, the first end of the first adjustable capacitor is connected to the first end of the switch capacitor array, the second end of the second adjustable capacitor is connected to the second end of the switch capacitor array, and the two ends of the switch capacitor array are respectively connected to the two ends of the first gap.

[0010] Further, the active transistor structure circuit includes a plurality of cross-coupled transistors. The active transistor structure circuit includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube, wherein the drain of the first switch tube is respectively connected to the first end of the first notch and the gate of the second switch tube, the gate of the first switch tube is respectively connected to the second end of the first notch and the drain of the second switch tube, the source of the first switch tube is respectively connected to the source of the second switch tube and the drain of the third switch tube, the source of the third switch tube is grounded, the gate is grounded through a capacitor, and is also connected to the gate of the fourth switch tube through a resistor, the source of the fourth switch tube is grounded, and the drain of the fourth switch tube is respectively connected to the gate and a current source.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] 1. The present invention uses artificial localized surface plasmons with a high quality factor as a resonance unit in a voltage-controlled oscillator, which can reduce the phase noise of the voltage-controlled oscillator.

[0013] 2. In the artificial localized surface plasmon proposed in the present invention, the first metal ring with metal grids and the second metal ring are coupled with each other, which increases the equivalent capacitance of the artificial localized surface plasmon and further reduces the resonant frequency of the artificial localized surface plasmon, so that at the same resonant frequency, the artificial localized surface plasmon proposed in the present invention has a smaller area than the existing artificial localized surface plasmon.

[0014] 3. In the artificial localized surface plasmon proposed in the present invention, the first metal ring with metal grids and the second metal ring are coupled with each other, so that the binding ability of the artificial localized surface plasmon to the electromagnetic field is enhanced, thereby reducing the electromagnetic interference between the artificial localized surface plasmon and surrounding devices.

[0015] 4. In the artificial localized surface plasmon proposed by the present invention, the first metal ring with metal grids and the second metal ring are coupled with each other, which can excite more available resonance modes than the existing artificial localized surface plasmon.

[0016] 5. A switching circuit is introduced into the artificial localized surface plasmon proposed in the present invention to realize the switching of the artificial localized surface plasmon resonance mode and the change of the resonance frequency, thereby realizing the mode switching of the voltage-controlled oscillator and broadening the tuning range of the voltage-controlled oscillator.

[0017] 6. The capacitor C at both ends of the first gap in the artificial localized surface plasmon can be composed of a fixed capacitor, an adjustable capacitor, or a switched capacitor, which can further broaden the tuning range of the voltage-controlled oscillator and avoid the mode ambiguity problem of the voltage-controlled oscillator. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of an embodiment of a dual-mode oscillator based on artificial surface plasmon provided by the present invention;

[0019] Figure 2 A schematic diagram of the working state of the switching circuit provided by the present invention;

[0020] Figure 3 A schematic structural diagram of an embodiment of a capacitor structure circuit provided by the present invention;

[0021] Figure 4 A schematic structural diagram of an embodiment of an active tube structure circuit provided by the present invention;

[0022] Figure 5 A schematic structural diagram of another embodiment of a dual-mode oscillator based on artificial surface plasmons provided by the present invention;

[0023] Figure 6 It is a schematic diagram of the structure of the present invention under different switching circuit states;

[0024] Figure 7 is the impedance frequency response curve of the present invention;

[0025] Figure 8 The electric field intensity distribution diagram of each resonance mode of the present invention;

[0026] Fig. 9 This is the phase noise simulation result of the present invention. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0028] An embodiment of the present invention provides a dual-mode oscillator based on artificial surface plasmons, including a resonance unit, a switching circuit, and a differential circuit.

[0029] like Figure 1As shown, the resonance unit includes a concentric first metal ring 1 and a second metal ring 2, both of which are circular rings, and the second metal ring 2 is located inside the first metal ring 1. The inner ring of the first metal ring 1 is connected with a plurality of first metal bars 3 facing the second metal ring 2, and the outer ring of the second metal ring 2 is connected with a plurality of second metal bars 4 facing the first metal ring 1, and the first metal bars 3 and the second metal bars 4 are arranged at intervals. A first notch 5 is provided on the first metal ring 1, a second notch 6 is provided on the second metal ring 2 at a position corresponding to the first notch 5, and a third notch 7 is provided at a position 180 degrees different from the second notch 6, the two ends of the differential circuit are respectively connected to the two ends of the first notch 5 for outputting a differential excitation signal, and the two ends of the switching circuit are respectively connected to the two ends of the third notch 7 for realizing a switching function, thereby switching the mode of the dual-mode oscillator. Among them, the first metal bars 3 extend inwardly along the diameter direction of the first metal ring 1, and the second metal bars 4 extend outwardly along the diameter direction of the second metal ring 2. The first metal bars 3 are arranged at equal intervals in the circumferential direction, and the second metal bars 4 are arranged at equal intervals in the circumferential direction. There are gaps between the first metal bars 3 and the second metal bars 4, and they are not directly connected, and the gaps between all the first metal bars 3 and the second metal bars 4 are consistent. The second metal ring 2 lacks one second metal bar in the second notch 6 and the third notch 7, respectively. The first metal bar 3 is not connected to the second metal ring 2, and the second metal bar 4 is not connected to the first metal ring 1.

[0030] The structural parameters of the first metal ring 1, the second metal ring 2, the first metal grid 3 and the second metal grid 4 are adjustable. The adjustable structural parameters include the inner and outer radii of the first metal ring 1 and the second metal ring 2, the length, width, spacing and number of the first metal grid 3 and the second metal grid 4. Under the premise of ensuring that the first metal grid 3 is not connected to the second metal ring 2 and the second metal grid 4 is not connected to the first metal ring 1, the frequency, intensity and quality factor of each resonant mode of the resonant unit can be changed by adjusting the above structural parameters.

[0031] The switching circuit controls the switching of the resonance mode and the resonance frequency of the resonance unit by changing the boundary conditions of the resonance unit. The switching circuit can work in two states, namely, an open state and a closed state. Figure 2As shown. On the one hand, ideally, when the switching circuit works in the open state, the two ports of the switching circuit are equivalent to an ideal open circuit; when the switching circuit works in the closed state, the two ports of the switching circuit are equivalent to an ideal short circuit. On the other hand, in actual situations, considering the non-ideal factors of the switching circuit, when the switching circuit works in the open state, the two ports of the switching circuit are equivalent to a capacitor; when the switching circuit works in the closed state, the two ports of the switching circuit are equivalent to a resistor. In specific implementation, a switching tube such as a field effect tube or a triode can be used as a switching circuit. By switching the switching circuit, the switching of the resonance unit between the two resonance modes can be realized, and the change of the resonance frequency of the resonance unit will cause the change of the oscillation frequency of the oscillator. Therefore, by switching the switching circuit, the switching of the oscillator between the two oscillation frequencies can be realized.

[0032] The differential circuit includes a capacitor structure circuit and an active tube structure circuit connected in parallel, wherein the capacitor structure circuit is equivalent to a capacitor C, and the active tube structure circuit is equivalent to a negative conductance -G m The two ends of the capacitor structure circuit and the two ends of the active tube structure circuit are respectively connected to the two ends of the first gap 5. Changing the equivalent capacitance C can change the resonant frequency of the parallel network of the resonant unit and the capacitor structure circuit, thereby changing the oscillation frequency of the oscillator. Negative conductance - G m It is used to provide energy to the parallel resonant network composed of the resonant unit and the capacitor structure circuit, so that the oscillator can start and maintain stable oscillation.

[0033] The capacitor structure circuit is connected in parallel with the resonant unit and can be composed of fixed capacitors, adjustable capacitors, switched capacitors, or any combination of the three. If the capacitor structure circuit includes an adjustable capacitor or a switched capacitor, the equivalent capacitor C can be tuned by an external voltage control signal, thereby realizing the tuning of the oscillation frequency of the oscillator by the external voltage signal. In an exemplary embodiment, Figure 3As shown, the capacitor structure circuit specifically includes a first adjustable capacitor C1, a second adjustable capacitor C2 and a switch capacitor array C3. The first adjustable capacitor C1 and the second adjustable capacitor C2 can adopt MOS varactor. The second end of the first adjustable capacitor C1 and the first end of the second adjustable capacitor C2 are both connected to the adjustable control voltage Vtune. The first end of the first adjustable capacitor C1 is connected to the first end of the switch capacitor array C3, the second end of the second adjustable capacitor C2 is connected to the second end of the switch capacitor array C3, and the two ends of the switch capacitor array C3 are respectively connected to the two ends p+ and p- of the first gap 5. By adjusting the control voltage Vtune, the capacitance of the adjustable capacitor is changed, thereby realizing the adjustment of the oscillation frequency of the oscillator. In addition, the switch capacitor array C3 is turned on and off by the 3-bit switch of the input digital control signal S1S2S3, so as to change the capacitance of the switch capacitor array C3, thereby realizing the adjustment of the oscillation frequency of the oscillator.

[0034] The active transistor structure circuit is composed of a number of cross-coupled transistors (such as field effect transistors or triodes). In an exemplary embodiment, Figure 4 As shown, the active transistor structure circuit may include a first switch tube S1, a second switch tube S2, a third switch tube S3, and a fourth switch tube S4. The drain of the first switch tube S1 is respectively connected to the first end p+ of the first notch 5 and the gate of the second switch tube S2, the gate of the first switch tube S1 is respectively connected to the second end p- of the first notch 5 and the drain of the second switch tube S2, the source of the first switch tube S1 is respectively connected to the source of the second switch tube S2 and the drain of the third switch tube S3, the source of the third switch tube S3 is grounded, the gate is grounded through a capacitor, and is also connected to the gate of the fourth switch tube S4 through a resistor, the source of the fourth switch tube S4 is grounded, and the drain of the fourth switch tube S4 is respectively connected to the gate and the current source IS. The first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are all NMOS tubes. The current source IS provides a DC bias for the cross-coupled NMOS tube. The circuit uses a basic current mirror with an RC low-pass filter to replicate the external input current.

[0035] In an exemplary embodiment, the overall structure of the dual-mode voltage-controlled oscillator is as follows: Figure 5 As shown, it can be realized using silicon-based CMOS technology. The dual-mode voltage-controlled oscillator uses NMOS cross-coupled pairs to form an equivalent negative conductance-G m , a current mirror is used to provide DC bias, and a varactor and a switched capacitor are used to form an equivalent capacitor C. Negative conductance - G m The first metal ring 1 is connected to the resonance unit in parallel with the capacitor C. A section of interconnection line is extended from the differential virtual ground point of the first metal ring 1 to connect to the DC power supply. The two ports of the switching circuit are respectively connected to the resonance unit.

[0036] The present invention was tested, Figure 6As shown, when the switching circuit is in the open and closed states, differential excitation is applied to the resonant unit, and the differential input impedance is obtained by simulation as follows: Figure 7 As shown. The simulation shows that when the switching circuit is in two working states, the resonant unit generates multiple modes. When the switching circuit is in the open state, the resonant unit generates three resonant modes, namely M1, M2 and M3, and their resonant frequencies are 121GHz, 289GHz and 346GHz respectively; when the switching circuit is in the closed state, the resonant unit generates three resonant modes, namely m1, m2 and m3, and their resonant frequencies are 82GHz, 124GHz and 271GHz respectively. Figure 7 The electric field distribution of each resonant mode in the two working states is shown in Figure 8 As shown. On the one hand, the resonance unit generates multiple resonance modes through the coupling between the first metal ring 1 and the second metal ring 2, thereby realizing mode hybridization. On the other hand, the switching circuit changes the boundary conditions of the resonance unit by switching the working state, thereby changing the resonance mode and the corresponding resonance frequency of the resonance unit, thereby realizing the switching of the resonance frequency.

[0037] The phase noise simulation results of the dual-mode voltage-controlled oscillator designed based on the circuit of the above embodiment are as follows: Fig. 9 The phase noise of the dual-mode voltage-controlled oscillator varies from -104.9dBc / Hz to -107.1dBc / Hz.

[0038] It should be understood that the above embodiments and descriptions only describe the principles, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A dual-mode oscillator based on artificial surface plasmon, comprising a resonant unit, a switching circuit, and a differential circuit, wherein: The resonance unit includes a concentric first metal ring and a second metal ring, the second metal ring is located inside the first metal ring, the inner ring of the first metal ring is connected with a plurality of first metal bars facing the second metal ring, the outer ring of the second metal ring is connected with a plurality of second metal bars facing the first metal ring, the first metal bars and the second metal bars are arranged at intervals, a first notch is provided on the first metal ring, a second notch is provided on the second metal ring at a position corresponding to the first notch, and a third notch is provided at a position 180 degrees different from the second notch, two ends of the differential circuit are respectively connected to two ends of the first notch for outputting a differential excitation signal, and two ends of the switching circuit are respectively connected to two ends of the third notch for realizing a switching function, thereby switching the mode of the dual-mode oscillator.

2. According to the dual-mode oscillator based on artificial surface plasmons according to claim 1, the first metal grid extends inwardly along the diameter direction of the first metal ring, and the second metal grid extends outwardly along the diameter direction of the second metal ring.

3. According to the dual-mode oscillator based on artificial surface plasmons in claim 1, the first metal bars are arranged at equal intervals in the circumferential direction, the second metal bars are arranged at equal intervals in the circumferential direction, there are gaps between the first metal bars and the second metal bars, and the gaps between all the first metal bars and the second metal bars are consistent. 4 . The dual-mode oscillator based on artificial surface plasmon according to claim 1 , wherein the second metal ring lacks a second metal grid at the second gap and the third gap respectively. 5 . According to the dual-mode oscillator based on artificial surface plasmons according to claim 1 , the switching circuit is specifically a switch tube.

6. According to the dual-mode oscillator based on artificial surface plasmons according to claim 1, the differential circuit includes a capacitor structure circuit and an active tube structure circuit in parallel, the capacitor structure circuit is a circuit equivalent to a capacitor, and the active tube structure circuit is a circuit equivalent to a negative conductance, and both ends of the capacitor structure circuit and both ends of the active tube structure circuit are respectively connected to both ends of the first gap. 7 . The dual-mode oscillator based on artificial surface plasmon according to claim 6 , wherein the capacitor structure circuit is specifically any one of a fixed capacitor, an adjustable capacitor, and a switch capacitor, or a combination of several of them.

8. According to the dual-mode oscillator based on artificial surface plasmons according to claim 7, the capacitor structure circuit specifically includes a first adjustable capacitor, a second adjustable capacitor and a switch capacitor array, the switch capacitor array controls the switch through the input digital control signal to adjust the oscillation frequency, the second end of the first adjustable capacitor and the first end of the second adjustable capacitor are both connected to the adjustable control voltage, the first end of the first adjustable capacitor is connected to the first end of the switch capacitor array, the second end of the second adjustable capacitor is connected to the second end of the switch capacitor array, and the two ends of the switch capacitor array are respectively connected to the two ends of the first gap. 9 . The dual-mode oscillator based on artificial surface plasmon according to claim 6 , wherein the active transistor structure circuit comprises a plurality of cross-coupled transistors.

10. According to the dual-mode oscillator based on artificial surface plasmons according to claim 9, the active tube structure circuit includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube, the drain of the first switch tube is respectively connected to the first end of the first notch and the gate of the second switch tube, the gate of the first switch tube is respectively connected to the second end of the first notch and the drain of the second switch tube, the source of the first switch tube is respectively connected to the source of the second switch tube and the drain of the third switch tube, the source of the third switch tube is grounded, the gate is grounded through a capacitor, and is also connected to the gate of the fourth switch tube through a resistor, the source of the fourth switch tube is grounded, and the drain of the fourth switch tube is respectively connected to the gate and a current source.

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