A dual-mode oscillator based on artificial surface plasmons

Abstract

The application discloses a dual-mode oscillator based on artificial surface plasmons, which comprises a resonant unit, a switching circuit and a differential circuit, wherein the resonant unit comprises concentric first and second metal rings, 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 and second metal bars are arranged at intervals, the first metal ring is provided with a first notch, the second metal ring is provided with a second notch at a position corresponding to the first notch and a third notch at a position 180 degrees away from the second notch, the two ends of the differential circuit are respectively connected with the two ends of the first notch for outputting a differential excitation signal, and the two ends of the switching circuit are respectively connected with the two ends of the third notch for realizing a switching function, so as to switch the mode of the dual-mode oscillator. The application has a wide frequency modulation range and low phase noise and can be realized on a chip.

Description

TECHNICAL FIELD

[0001] The present application relates to an oscillator, in particular to a dual-mode oscillator based on artificial surface plasmons. BACKGROUND

[0002] Oscillator is a commonly used device on chip, which is used to generate high-frequency alternating current signal. The oscillator can convert direct current energy into alternating current 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, and its phase noise and frequency modulation range directly affect the performance of the communication system. In the millimeter wave communication transceiver chip, LC voltage-controlled oscillator is often used to generate high-performance local oscillator signal. The traditional LC voltage-controlled oscillator uses variable capacitance to realize frequency tuning and expand the frequency modulation range. Variable capacitance is often realized by varactor and switched capacitor. However, in the millimeter wave frequency band, variable capacitance will introduce significant loss, which will deteriorate the phase noise of the voltage-controlled oscillator. The larger the variable capacitance, the larger the frequency modulation range of the voltage-controlled oscillator, but the phase noise performance will also be more serious. Therefore, it is difficult to realize a millimeter wave voltage-controlled oscillator with 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, which can produce electromagnetic waves similar to surface plasmons on the interface of the medium. Artificial localized surface plasmon is a kind of artificial surface plasmon. Artificial localized surface plasmon resonance is a resonance produced by periodic slotted metamaterial structure, which can be regarded as a standing wave caused by artificial localized surface plasmon propagating on the surface of metamaterial metal structure. The 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 board and chip. SUMMARY

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

[0006] In order to achieve the above-mentioned purposes, the application provides a dual-mode oscillator based on artificial surface plasmons, which comprises a resonant unit, a switching circuit and a differential circuit, wherein the resonant unit comprises concentric first and second metal rings, the second metal ring is located in the first metal ring, a plurality of first metal bars are connected to the inner ring of the first metal ring and face the second metal ring, a plurality of second metal bars are connected to the outer ring of the second metal ring and face the first metal ring, the first and second metal bars are arranged at intervals, the first metal ring is provided with a first notch, the second metal ring is provided with a second notch at a position corresponding to the first notch and a third notch at a position 180 degrees away from the second notch, the differential circuit is connected to the two ends of the first notch for outputting a differential excitation signal, and the switching circuit is connected to the two ends of the third notch for realizing a switching function and switching the mode of the dual-mode oscillator.

[0007] Further, the first metal bars extend inward along the diameter direction of the first metal ring, and the second metal bars extend outward along the diameter direction of the second metal ring. 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 is a gap between the first metal bars and the second metal bars, and the gaps of all the first metal bars and the second metal bars are consistent. The second metal ring is provided with one second metal bar missing at the second notch and the third notch, respectively.

[0008] Further, the differential circuit comprises a parallel-connected capacitor structure circuit and an active tube structure circuit, the capacitor structure circuit is equivalent to a capacitor, and the active tube structure circuit is equivalent to a negative conductance. 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 notch.

[0009] Further, the capacitor structure circuit specifically comprises any one or a combination of fixed capacitors, adjustable capacitors and switch capacitors. The capacitor structure circuit specifically comprises a first adjustable capacitor, a second adjustable capacitor and a switch capacitor array. The switch capacitor array controls the switch through an input digital control signal, thereby adjusting the oscillation frequency. The second end of the first adjustable capacitor and the first end of the second adjustable capacitor are 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. The two ends of the switch capacitor array are respectively connected to the two ends of the first notch.

[0010] Further, the active tube structure circuit includes several cross-coupled transistors.

[0011] Compared with the prior art, the present application has the following advantages:

[0012] 1. The artificial local surface plasmon with high quality factor is used as a resonance unit in the voltage-controlled oscillator, so that the phase noise of the voltage-controlled oscillator can be reduced.

[0013] 2. In the artificial local surface plasmon, the first metal ring and the second metal ring with metal grating are coupled to each other, so that the equivalent capacitance of the artificial local surface plasmon is improved, the resonance frequency of the artificial local surface plasmon is further reduced, and the artificial local surface plasmon has a smaller area than the existing artificial local surface plasmon at the same resonance frequency.

[0014] 3. In the artificial local surface plasmon, the first metal ring and the second metal ring with metal grating are coupled to each other, so that the binding ability of the artificial local surface plasmon to the electromagnetic field is strengthened, thereby reducing the electromagnetic interference between the artificial local surface plasmon and surrounding devices.

[0015] 4. In the artificial local surface plasmon, the first metal ring and the second metal ring with metal grating are coupled to each other, so that more available resonance modes can be excited than the existing artificial local surface plasmon.

[0016] 5. The switching circuit is introduced in the artificial local surface plasmon, so that the switching of the resonance mode of the artificial local surface plasmon and the change of the resonance frequency are realized, thereby realizing the mode switching of the voltage-controlled oscillator and widening the tuning range of the voltage-controlled oscillator.

[0017] 6. The capacitance C at both ends of the first gap in the artificial local surface plasmon can be composed of a fixed capacitance, an adjustable capacitance or a switch capacitance, so that the tuning range of the voltage-controlled oscillator can be further widened, and the mode ambiguity problem of the voltage-controlled oscillator can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Structure diagram of one embodiment of the artificial surface plasmon based dual-mode oscillator provided by the present application;

[0019] Figure 2 Working state diagram of the switching circuit provided by the present application;

[0020] Figure 3 Structure diagram of one embodiment of the capacitance structure circuit provided by the present application;

[0021] Figure 4 Structure diagram of one embodiment of the active tube structure circuit provided by the present application;

[0022] Figure 5 Structure diagram of another embodiment of the artificial surface plasmon based dual-mode oscillator provided by the present application;

[0023] Figure 6 Structure diagram of the different switching circuit states of the present application;

[0024] Figure 7 Impedance frequency response curve of the present application;

[0025] Figure 8 Electric field intensity distribution diagram of each resonance mode of the present application;

[0026] Figure 9 Phase noise simulation result of the present application. DETAILED DESCRIPTION

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

[0028] The embodiments of the present application provide an artificial surface plasmon based dual-mode oscillator, which comprises a resonance unit, a switching circuit and a differential circuit.

[0029] As shown in FIG. 1, the artificial surface plasmon based dual-mode oscillator provided by the present application comprises a resonance unit, a switching circuit and a differential circuit. Figure 1As shown, the resonant unit comprises concentric first metal ring 1 and second metal ring 2, both of which are circular rings, and the second metal ring 2 is located in the first metal ring 1. A plurality of first metal bars 3 facing the second metal ring 2 are connected to the inner circle of the first metal ring 1, and a plurality of second metal bars 4 facing the first metal ring 1 are connected to the outer circle of the second metal ring 2, and the first metal bars 3 and the second metal bars 4 are arranged at intervals. The first metal ring 1 is provided with a first notch 5, the second metal ring 2 is provided with a second notch 6 at a position corresponding to the first notch 5, and a third notch 7 is provided at a position 180 degrees away 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 the switching function, thereby switching the mode of the dual-mode oscillator. Among them, the first metal bars 3 extend inward along the diameter direction of the first metal ring 1, and the second metal bars 4 extend outward 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 is a gap between the first metal bars 3 and the second metal bars 4, and they are not directly connected, and the gap between all the first metal bars 3 and the second metal bars 4 is consistent. The second metal ring 2 is missing one second metal bar at the second notch 6 and the third notch 7 respectively. The first metal bars 3 are not connected to the second metal ring 2, and the second metal bars 4 are 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 bars 3 and the second metal bars 4 can be adjusted. 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 bars 3 and the second metal bars 4. Under the premise of ensuring that the first metal bars 3 are not connected to the second metal ring 2 and the second metal bars 4 are not connected to the first metal ring 1, adjusting the above structural parameters can change the frequency, strength and quality factor of each resonant mode of the resonant unit.

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

[0032] The differential circuit includes a parallel connection of a capacitor structure circuit and an active tube structure circuit, the capacitor structure circuit being a circuit equivalent to a capacitor C, and the active tube structure circuit being a circuit 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 capacitor 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. The negative conductance -G m The differential circuit includes a parallel connection of a capacitor structure circuit and an active tube structure circuit, the capacitor structure circuit being a circuit equivalent to a capacitor C, and the active tube structure circuit being a circuit equivalent to a negative conductance -G

[0033] The capacitor structure circuit is in parallel connection with the resonant unit and can be composed of a fixed capacitor, an adjustable capacitor, a switch capacitor, or any combination of the three. If the capacitor structure circuit includes an adjustable capacitor or a switch 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 one illustrative embodiment, as Figure 3As shown, the capacitor structure circuit specifically comprises a first adjustable capacitor C1, a second adjustable capacitor C2 and a switched capacitor array C3. The first adjustable capacitor C1 and the second adjustable capacitor C2 can be MOS varactor tubes. The second end of the first adjustable capacitor C1 and the first end of the second adjustable capacitor C2 are both connected to an adjustable control voltage Vtune. The first end of the first adjustable capacitor C1 is connected to the first end of the switched capacitor array C3, and the second end of the second adjustable capacitor C2 is connected to the second end of the switched capacitor array C3. The two ends of the switched capacitor array C3 are respectively connected to the two ends p+ and p- of the first notch 5. By adjusting the control voltage Vtune to change the capacitance of the adjustable capacitor, the oscillation frequency of the oscillator is adjusted. In addition, the switched capacitor array C3 is switched on and off by 3-bit switches of the input digital control signal S1S2S3, so as to change the capacitance of the switched capacitor array C3, and the oscillation frequency of the oscillator is adjusted.

[0034] The active tube structure circuit is composed of a plurality of cross-coupled transistors (such as field effect tubes or triodes). In an illustrative embodiment, as shown in Figure 4 The active tube structure circuit can comprise 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 also connected to the gate of the fourth switch tube S4 through a resistor. The source of the fourth switch tube S4 is grounded. The drain of the fourth switch tube S4 is respectively connected to the gate and a 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 DC bias for the cross-coupled NMOS tubes. The circuit uses a basic current mirror with RC low-pass filtering to copy the external input current.

[0035] In an illustrative embodiment, the overall structure of the dual-mode voltage-controlled oscillator is as shown in Figure 5 which can be implemented using a silicon-based CMOS process. The dual-mode voltage-controlled oscillator uses a NMOS cross-coupled pair to form an equivalent negative conductance-G m , uses a current mirror to provide DC bias, and uses a varactor and a switched capacitor to form an equivalent capacitor C. The negative conductance-G m and the capacitor C are connected in parallel to the resonant unit. A section of interconnection line extending from the differential virtual ground of the first metal ring 1 connects to the DC power supply. The two ports of the switching circuit are respectively connected to the resonant unit.

[0036] Experiments were conducted on the present application, as Figure 6As shown, the differential input impedance of the resonant unit is simulated as Figure 7 As shown, the simulation results of the electric field distribution of each resonant mode in the two working states are shown in FIG. 6 and FIG. 7, respectively. Figure 7 As shown, the simulation results of the electric field distribution of each resonant mode in the two working states are shown in FIG. 6 and FIG. 7, respectively. Figure 8 As shown, the resonant unit generates multiple resonant modes through the coupling between the first metal ring 1 and the second metal ring 2, and achieves mode hybridization. On the other hand, the switching circuit changes the boundary conditions of the resonant unit by switching the working state, thereby changing the resonant modes and the corresponding resonant frequencies of the resonant unit, and achieving the switching of the resonant frequency.

[0037] The simulation results of the phase noise of the dual-mode voltage-controlled oscillator based on the above-mentioned embodiment circuit are shown in FIG. 8. Figure 9 The phase noise of the dual-mode voltage-controlled oscillator varies in the range of -104.9dBc / Hz to -107.1dBc / Hz.

[0038] It should be understood that the above embodiments and the description in the specification are only the principles, main features and advantages of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the protection scope of the present application.

Claims

1. A dual-mode oscillator based on artificial surface plasmon, comprising a resonant unit, a switching circuit, and a differential circuit, wherein: The resonant 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 away from the second notch, the two ends of the differential circuit are respectively connected to the two ends of the first notch for outputting a differential excitation signal, the two ends of the switching circuit are respectively connected to the two ends of the third gap, for realizing the switching function, thereby switching the mode of the dual-mode oscillator; the first metal grid extends inward along the diameter direction of the first metal ring, and the second metal grid extends outward along the diameter direction of the second metal ring; the first metal grids are arranged at equal intervals in the circumferential direction, and the second metal grids are arranged at equal intervals in the circumferential direction, there is a gap between the first metal grid and the second metal grid, and the gap between all the first metal grids and the second metal grids is consistent; the second metal ring lacks a second metal grid in the second gap and the third gap respectively. 2 . The dual-mode oscillator based on artificial surface plasmon according to claim 1 , wherein the switching circuit is specifically a switch tube.

3. 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 the active tube structure circuit are respectively connected to both ends of the first gap.

4. The dual-mode oscillator based on artificial surface plasmon according to claim 3, wherein the capacitor structure circuit is specifically any one of a fixed capacitor, an adjustable capacitor, and a switched capacitor, or a combination of several of them.

5. The dual-mode oscillator based on artificial surface plasmon according to claim 4, wherein the capacitor structure circuit specifically includes a first adjustable capacitor, a second adjustable capacitor and a switched capacitor array, the switched capacitor array controls the switch by an input digital control signal, thereby adjusting 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 switched capacitor array, the second end of the second adjustable capacitor is connected to the second end of the switched capacitor array, and the two ends of the switched capacitor array are respectively connected to the two ends of the first notch. 6 . The dual-mode oscillator based on artificial surface plasmon according to claim 3 , wherein the active transistor structure circuit comprises a plurality of cross-coupled transistors.

7. The dual-mode oscillator based on artificial surface plasmon according to claim 6, wherein the active tube structure circuit includes a first switching tube, a second switching tube, a third switching tube, and a fourth switching tube, wherein the drain of the first switching tube is respectively connected to the first end of the first notch and the gate of the second switching tube, the gate of the first switching tube is respectively connected to the second end of the first notch and the drain of the second switching tube, the source of the first switching tube is respectively connected to the source of the second switching tube and the drain of the third switching tube, the source of the third switching tube is grounded, the gate is grounded through a capacitor, and is also connected to the gate of the fourth switching tube through a resistor, the source of the fourth switching tube is grounded, and the drain of the fourth switching tube is respectively connected to the gate and a current source.

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