An artificial localized surface plasmon active oscillation sensor

Abstract

The present invention discloses an artificial localized surface plasmon active oscillation sensor, which includes an artificial localized surface plasmon resonator, a microwave amplifier, a coupler, and an auxiliary capacitance-resistance matching circuit. The artificial localized surface plasmon resonator serves as the filtering network of the active oscillator and forms a loop with the microwave amplifier, thereby converting the resonance frequency of the passive artificial localized surface plasmon resonator into the frequency of the active oscillation signal and outputting it from the coupler. The active oscillation sensor of the present invention realizes high-precision sensing of the surface dielectric environment based on the high-quality factor and high-sensitivity resonance of the artificial localized surface plasmon, and realizes the active output of the sensing signal.

Description

Technical Field

[0001] The present invention belongs to the field of sensors, and particularly relates to an active oscillator using a spoof localized surface plasmon resonator as a filtering network, whose oscillation frequency varies with the sensing signal. Background Art

[0002] A sensor is a device, module or system that responds to specific parameters in the environment and converts the change information of the parameters into electrical signals for subsequent information transmission and processing. Sensor technology, together with computer technology and communication technology, is known as the three major pillars of information technology.

[0003] The development of resonant sensors in the microwave band can be traced back to the quartz crystal microbalance invented in 1959, which can be understood as an active resonant sensor. With the development of microwave printed circuits and microwave integrated circuits, more flexible passive resonant structures such as microstrip loops and RFID antennas have been used for sensing. The concept and design method of metamaterials bring more abundant and flexible choices for resonant structures, such as split-ring resonators and left-handed transmission lines. Thanks to the compatibility with planar printed circuits and semiconductor integrated circuits, microwave resonant sensors have superior integration, general environmental adaptability and high robustness to noise and vibration; and they have natural compatibility with signal detection circuits and communication circuits, so they have great technical advantages and development potential in the field of sensors for the Internet of things.

[0004] In recent years, microwave resonant sensors based on spoof localized surface plasmons (SLSP) have received extensive attention and developed rapidly. Spoof localized surface plasmons achieve equivalent negative permittivity through sub-wavelength artificial electromagnetic microstructures, thus reproducing the mode characteristics of optical frequency localized surface plasmons in the microwave band, and realizing deep sub-wavelength field confinement and high local sensitivity. Sensors based on spoof localized surface plasmons have been verified in applications such as gas sensing and biochemical sensing (such as glucose solution concentration, alcohol solution concentration); and a ultra-small wireless IoT sensing system has been realized.

[0005] However, existing artificial localized surface plasmon sensors are all based on passive resonant structures. Although there are some reports on loading amplifiers inside the resonant structures of artificial localized surface plasmons, the amplifier only serves to compensate for the losses of the passive resonator and can improve the quality factor of the passive resonator. However, as the detection signal of the sensor, the resonator still requires an external microwave source. This detection method of resonant sensors greatly limits their applications, especially the development towards integrated Internet of Things sensors. The artificial localized surface plasmon active oscillation sensor proposed in the present invention can convert the passive resonant sensing signal into the frequency of an active oscillation signal, simplifying the complexity of its signal detection. On the other hand, based on the high quality factor of the artificial localized surface plasmon resonator, the phase noise of the active oscillation signal is greatly improved, and the detection accuracy of the sensing signal is also improved. Compared with other microwave resonant sensing technologies based on active oscillation, artificial localized surface plasmons exhibit excellent sensing sensitivity. Therefore, the present invention will provide a new technical path for microwave resonant sensing and promote the technological innovation of the next generation of integrated miniaturized Internet of Things sensors. Summary of the Invention

[0006] Object of the Invention: The present invention aims to provide an artificial localized surface plasmon active oscillation sensor.

[0007] Technical Solution: The present invention adopts the following technical solutions:

[0008] An artificial localized surface plasmon active oscillation sensor includes an artificial localized surface plasmon resonator, a microwave amplifier, and a coupler;

[0009] The artificial localized surface plasmon resonator, the microwave amplifier, and the coupler form a closed loop;

[0010] The artificial localized surface plasmon resonator is composed of a plurality of radial metal arms surrounding the circumference.

[0011] The radial metal arms can be radial straight lines or spirals.

[0012] The radial metal arms can diverge outward from the central small disc or converge towards the center from the outer ring.

[0013] The sensor circuit form can be a microstrip circuit, a coplanar waveguide circuit, or a dielectric integrated waveguide circuit.

[0014] The dielectric substrate of the sensor circuit described above is a printed circuit or microwave circuit dielectric substrate of FR4, F4B, RO4003, 3003, 4350, RT5880, 5870, 6002, 6006, 6010, 6035, 6202 produced by Rogers Corporation, or N4000-13, N4000-13EPSI produced by Nelco Corporation, or a semiconductor or dielectric material of Si, SiO2, Al2O3, GaAs, GaN, or a flexible organic dielectric material.

[0015] The sensing signal comes from the change of dielectric constant on the surface of the artificial localized surface plasmon resonator or in the near-field range, and can come from gas concentration, solution concentration, chemical reaction on the resonator surface, temperature change, stress change, etc.

[0016] Beneficial effects: Compared with the prior art, the artificial localized surface plasmon active oscillation sensor disclosed in the present invention has the following innovative principles: (1) Through the artificial localized surface plasmon resonator, deeper sub-wavelength electrical size, higher quality factor and higher sensitivity are achieved; (2) By combining the artificial localized surface plasmon with an amplifier, an active oscillation sensor is formed, which can actively emit microwave signals to measure the sensing signal without relying on large devices with excitation sources such as vector network analyzers. (3) Based on the high quality factor of the artificial localized surface plasmon, the phase noise of its active oscillation signal is greatly improved, thereby improving the signal detection accuracy. Brief Description of the Drawings

[0017] Figure 1 It is the schematic diagram of the artificial localized surface plasmon active oscillation sensor disclosed in the present invention.

[0018] Figure 2 It is the artificial localized surface plasmon resonator adopted in the first embodiment disclosed in the present invention, where (a) is the circuit diagram of the artificial localized surface plasmon resonator including a transmission line and an excitation structure, (b) is the schematic diagram of the geometric shape and parameters of the artificial localized surface plasmon resonator, (c) is the side view of the sensing medium to be measured and the circuit board, showing the positional relationship of each layer, and (d, e) are the S 21 amplitude (d) and phase (e) spectra when the relative dielectric constant of the medium to be measured of this artificial localized surface plasmon resonator is 72 and 80 (for sensing aqueous solutions).

[0019] Figure 3 It is the microwave amplifier adopted in the first and second embodiments of the present invention, where (a) is the peripheral matching circuit of the amplifier, and (b) and (c) are the S 21 spectra of the amplifier under different matching circuit parameters in the coplanar waveguide (CPW) circuit and the microstrip circuit respectively.

[0020] Figure 4 The artificial localized surface plasmon active oscillation sensor of Embodiment 1 of the present invention, where (a) is the upper-layer pattern and device layout of the entire circuit, and (b) is the output signal spectrum when the relative permittivities of the medium to be measured (aqueous solution) are 72 and 80 respectively.

[0021] Figure 5 The artificial localized surface plasmon resonator adopted in Embodiment 2 of the present invention, where (a) is the circuit pattern of the artificial localized surface plasmon resonator including a transmission line and an excitation structure, (b) is the side view of the medium to be sensed and the circuit board, showing the positional relationship of each layer, and (c, d) are the S 21 magnitude (c) and phase (d) spectra when the relative permittivity of the medium to be measured is 2.3 and 2.8 respectively.

[0022] Figure 6 The artificial localized surface plasmon active oscillation sensor of Embodiment 2 of the present invention, where (a) is the upper-layer pattern and device layout of the entire circuit, and (b) is the output signal spectrum when the relative permittivities of the medium to be measured are 2.3 and 2.8 respectively. Specific embodiments

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the specific implementation cases of the present invention will be described below with reference to the accompanying drawings.

[0024] The present invention discloses an artificial localized surface plasmon active oscillation sensor, including an artificial localized surface plasmon resonator, a microwave amplifier, and a coupler, as Figure 1 shown.

[0025] Embodiment 1:

[0026] The artificial localized surface plasmon resonator in Embodiment 1 is as Figure 2 , the entire circuit adopts the form of a coplanar waveguide (CPW), and the artificial localized surface plasmon is excited by a capacitive coupling structure composed of slits. In the CPW circuit form, all metal patterns are on the upper surface (Top Layer) of the dielectric substrate, and the devices are also labeled on the upper surface, and all the copper foils on the lower surface of the dielectric substrate are removed. In this embodiment, an F4B board with a thickness of 0.5 mm and a dielectric constant of 2.65 is adopted. The geometric structure and structural parameters of the artificial localized surface plasmon resonator are as Figure 2In (b), in this embodiment, D = 6 mm, d = 2 mm, s = 0.2 mm. When a 0.3-mm-thick aqueous solution covers the surface of this artificial localized surface plasmon resonator (the loading of the thin-layer solution is controlled by a microfluidic cavity, the area of the solution is a circle with a diameter of 6 mm and coincides with the center of the resonator), the S of the resonator 21 amplitude and phase are as shown in Figure 2 (d) and (e). The quality factor of the artificial localized surface plasmon resonance is 7.6 (in an aqueous solution environment). When the dielectric constant of the solution changes from 72 to 80, its resonance frequency changes from 3.70 GHz to 3.54 GHz. Within the frequency band corresponding to the resonance bandwidth, the phase of this artificial localized surface plasmon resonator experiences a change of approximately 180°, laying a foundation for its active oscillation sensor.

[0027] The microwave amplifier used in this embodiment is as shown in Figure 3 , which is the ATF-54143 model of Avago. The matching circuit of this amplifier is as shown in Figure 3 (a), and voltages V ds = 3 V and V gs = 0.65 V need to be applied. In this embodiment, the capacitance and inductance values of its bias circuit are: C1 = 2 pF, C2 = 68 pF, C3 = C4 = C5 = 0.1 μF, L1 = 68 nH, L2 = L3 = 47 nH, R1 = 15 Ω. Under the CPW circuit and the above matching circuit parameters, the S 21 curve is as shown in Figure 3 (b).

[0028] The circuit layout of this embodiment is as shown in Figure 4 (a), where the capacitors and inductors adopt 0603 packages; except for the components in Figure 3 , at the isolation port of the coupler, a resistor with R2 = 50 Ω is grounded. The coupler of this embodiment is on the right side of the circuit board and consists of mutually coupled transmission lines. The spectrum of the oscillation signal in the loop of this embodiment is as shown in Figure 4 (b), which is the simulation result of Advanced Design System. When the dielectric constant of the solution on the artificial localized surface plasmon surface changes from 72 to 80, its output signal frequency changes from 3.54 GHz to 3.41 GHz; its change trend is consistent with that of the resonance frequency of the passive artificial localized surface plasmon resonator, and the difference in values is caused by the matching network.

[0029] Embodiment 2:

[0030] The artificial localized surface plasmon resonator in Embodiment 2 is as shown in Figure 5, the circuit adopts the form of a microstrip circuit, and the artificial localized surface plasmon is excited by a capacitive coupling structure formed by an arc with a width of 1 mm. In the form of a microstrip circuit, various metal patterns are on the upper surface (Top Layer) of the dielectric substrate, and the devices are also labeled on the upper surface. The lower surface (BottomLayer) of the dielectric substrate is a large-area metal ground. In this embodiment, an F4B board with a thickness of 0.5 mm and a dielectric constant of 2.65 is used. The geometric structure and structural parameters of the artificial localized surface plasmon resonator are as Figure 5 shown in (a) of 21 . In this embodiment, two Archimedean spiral lines with a width of 0.15 mm are used as the metal arms of the artificial localized surface plasmon resonator, and the diameter of the resonator is about 5.25 mm. When a 0.1 mm thick square polydimethylsiloxane (PDMS) film with a side length of 7 mm covers the surface of the artificial localized surface plasmon resonator, its S Figure 5 amplitude and phase are as shown in (d) and (e) of 21 . When the PDMS film is under pressure or absorbs organic vapor, its dielectric constant will change, so that mechanical quantity and gas sensing can be carried out. The quality factor of the artificial localized surface plasmon resonator is 53.7; when the dielectric constant of the PDMS film changes from 2.3 to 2.8, its resonance frequency changes from 2.52 GHz to 2.47 GHz. In the frequency band corresponding to the resonance bandwidth, the S

[0031] phase of this artificial localized surface plasmon resonator experiences a change of about 180°, laying a foundation for its active oscillation sensor. Figure 3 shown in (a) of ds ), and voltages V gs = 3V and V 21 need to be loaded. The capacitance and inductance values of its bias circuit are: C1 = C2 = C3 = C4 = C5 = 0.1 μF, L1 = 3.3 nH, L2 = L3 = 47 nH, R1 = 30 Ω. Under the parameters of the microstrip circuit and the above matching circuit, the S Figure 3 curve is as shown in (c) of Figure 3 . In addition to the components in

[0032] , a resistor with R2 = 50 Ω is grounded at the isolation port of the coupler. Figure 6 The circuit layout of this embodiment is as shown in (a) of Figure 6As shown in (b), it is the simulation result of Advanced Design System. When the dielectric constant of the PDMS thin film on the artificial localized surface plasmon surface changes from 2.3 to 2.8, its output signal frequency changes from 2.51 GHz to 2.46 GHz; its change trend is consistent with that of the resonance frequency of the passive artificial localized surface plasmon resonator, and the numerical difference is caused by the matching network.

Claims

1. An artificial localized surface plasmon active oscillation sensor, characterized in that: It includes an artificial localized surface plasmon resonator, a microwave amplifier, and a coupler; The artificial localized surface plasmon resonator, the microwave amplifier, and the coupler form a closed loop.

2. The artificial localized surface plasmon active oscillation sensor according to claim 1, wherein: The artificial localized surface plasmon resonator is composed of a plurality of radial metal arms surrounding a circumference.

3. The artificial localized surface plasmon active oscillation sensor according to claim 2, characterized in that: The radial metal arms are radial straight lines or spirals.

4. The artificial localized surface plasmon active oscillation sensor according to claim 2, characterized in that: The radial metal arms diverge outward from a central small disk or converge toward the center from an outer ring.

5. An artificial localized surface plasmon active oscillation sensor according to claim 1, characterized in that, The circuit form of the sensor is a microstrip circuit, a coplanar waveguide circuit, and a dielectric integrated waveguide circuit.

6. The artificial localized surface plasmon active oscillation sensor according to claim 1, wherein The dielectric substrate of the sensor circuit is a printed circuit or a dielectric substrate of a microwave circuit made of FR4, F4B, RO4003, 3003, 4350, RT5880, 5870, 6002, 6006, 6010, 6035, 6202 produced by Rogers Corporation, N4000-13, N4000-13EPSI produced by Nelco Corporation, or a semiconductor or dielectric material such as Si, SiO2, Al2O3, GaAs, GaN, or a flexible organic dielectric material.

7. The artificial localized surface plasmon active oscillation sensor according to claim 1, wherein The sensing signal comes from the change in dielectric constant on the surface of the artificial localized surface plasmon resonator or in the near-field range, from gas concentration, solution concentration, chemical reactions on the resonator surface, temperature change, or stress change.

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