A GaN HEMT pressure sensing system enhanced by a microwave rectifier

Abstract

The application relates to a microwave rectifier enhanced GaN HEMT pressure sensor system and belongs to the technical field of sensors. The application is a high-sensitivity pressure sensor based on a microwave rectifier enhanced gallium nitride (GaN) high electron mobility transistor (HEMT), a microwave rectifier working in a Ka band is designed, the source-drain resistance (Rds) of the HEMT is directly connected as a load, a positive feedback enhancement mechanism of Rds change caused by the piezoelectric effect of pressure and rectifier output voltage can realize high-sensitivity detection of a high-frequency pressure signal.

Description

Technical Field

[0001] This invention relates to a microwave rectifier-enhanced GaN HEMT pressure sensing system, belonging to the field of sensor technology. Background Technology

[0002] With the rapid development of wireless technology and the Internet of Things (IoT), the demand for wireless power transmission is increasing. Microwave rectifiers are a key component in microwave wireless power transmission systems, converting microwave signals received by the antenna into DC power. A traditional microwave rectifier circuit consists of an input matching circuit, an input filter circuit, rectifier devices (often transistors or rectifier diodes), an output filter circuit, and a load resistor.

[0003] One major application of wireless power transfer is in sensors. Traditional sensors require power modules, which necessitate wired charging or frequent battery replacements, increasing equipment maintenance costs. Rectifiers convert microwave energy into DC power output to supply the sensor, greatly improving its operational flexibility.

[0004] Gallium nitride high electron mobility transistor (GaN HEMT) pressure sensors are a promising type of sensor. Gallium nitride's wide bandgap, high critical breakdown electric field, and high thermal conductivity make it suitable for high-frequency, high-power, and high-temperature applications. The piezoelectric polarization effect of AlGaN / GaN heterojunctions can generate a high-density two-dimensional electron gas (2DEG), which is highly sensitive to changes in external pressure, making it suitable as a pressure sensor. However, current GaN HEMT pressure sensors suffer from two problems. First, GaN HEMT pressure sensors require an additional constant voltage applied by the power supply module, which limits the miniaturization and lifespan of the sensor. Second, the Wheatstone bridge circuit commonly used in GaN HEMT pressure sensors has very low sensitivity, making it difficult to capture minute changes in physical quantities during detection, and the signal may be masked by noise.

[0005] Therefore, there is an urgent need to find a way to simultaneously achieve stable power supply from the rectifier and improve the sensitivity of the GaN HEMT pressure sensor. Summary of the Invention

[0006] To address the aforementioned problems, this invention combines a microwave rectifier and a GaN HEMT, proposing a method that both powers the sensor and enhances its sensitivity. This invention provides a Ka-band microwave rectifier-enhanced GaN HEMT pressure sensing system, comprising a rectifier. An RF input signal is fed into the rectifier via a DC blocking capacitor. The rectifier includes, from top to bottom, a circuit layer, a dielectric substrate, and a metal ground layer. The circuit layer includes an input-grounded coplanar waveguide, a T-type input matching network, a Schottky diode, and an output filter circuit. The GaN HEMT pressure sensor is directly used as the load of the rectifier, and the output of the rectifier is connected to the drain of the GaN HEMT sensor. The source of the GaN HEMT sensor is grounded, thus forming a rectifier-HEMT closed-loop circuit powered by the rectified DC voltage. Pressure changes are sensed by modulating the HEMT channel current.

[0007] Furthermore, the circuit layer of the rectifier has a circuit topology that is a parallel rectifier circuit designed based on a single gallium nitride Schottky diode.

[0008] Furthermore, the grounded coplanar waveguide is a 50-ohm grounded coplanar waveguide.

[0009] Furthermore, the dielectric substrate is Rogers 4350B material with a dielectric constant of 3.48, a loss of 0.0037, and a thickness of 0.51 mm.

[0010] Furthermore, the edge of the circuit layer is provided with a plurality of linearly arranged through holes.

[0011] Furthermore, the rectifier is a microwave rectifier operating at 27 GHz, and the load resistor is 120 Ω.

[0012] Furthermore, the gate voltage of the rectifier-HEMT closed-loop circuit is -2.5V.

[0013] In some embodiments, the GaN HEMT pressure sensor includes a pressure chamber with a pressure inlet. The rectifier-HEMT closed-loop circuit is bonded to the PDMS and fixed on the PCB board and built into the pressure chamber, so that the HEMT surface can be uniformly stressed.

[0014] Furthermore, when the external pressure changes, the GaN HEMT pressure sensing system utilizes the piezoelectric polarization effect of the GaN / AlGaN heterojunction. The external pressure causes mechanical strain in the barrier layer, inducing polarization charge density on the heterojunction surface, thereby changing the two-dimensional electron gas density, which causes the source-drain resistance Rds of the HEMT to change with the pressure p.

[0015] Furthermore, the relationship between the rectifier's output voltage Vout and Rds is as follows: Where is the rectification efficiency and Pin is the input power;

[0016] When the pressure increases, causing Rds to increase, Vout increases synchronously. The increased Vout further shifts the HEMT operating point toward the saturation region, causing Rds to increase further, and subsequently Vout also increases further, forming a positive feedback loop.

[0017] The beneficial effects of this invention:

[0018] This invention provides a high-sensitivity pressure sensor based on a microwave rectifier-enhanced gallium nitride (GaN) high electron mobility transistor (HEMT). By designing a microwave rectifier operating in the Ka band and directly connecting it to the source-drain resistance (Rds) of the HEMT as a load, and utilizing the positive feedback enhancement mechanism of the change in Rds caused by the piezoelectric effect induced by pressure and the rectifier output voltage, high-sensitivity detection of pressure signals in the high-frequency band can be achieved. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure in one embodiment of the present invention.

[0020] Figure 2 This is a rectifier layout according to one embodiment of the present invention.

[0021] Figure 3 This is a graph showing the efficiency curves of 27GHz rectification simulation and actual measurement in one embodiment of the present invention.

[0022] Figure 4 This is a graph showing the change of output voltage with air pressure in one embodiment of the present invention.

[0023] Figure 5 This is a comparison chart of the rate of change of Rds with and without microwave enhancement in one embodiment of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] In this invention, the terms "first" and "second" are used only to distinguish similar components / parts in different positions or with different characteristics, and have no other limiting meaning; "upper" refers to the direction in which each component is away from the ground, and "lower" refers to the direction in which each component is away from the ground.

[0027] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0028] This invention provides a GaN HEMT pressure sensing system enhanced by a microwave rectifier, in Figure 1 In one example, the present invention includes a rectifier into which an RF input signal is fed via a DC blocking capacitor and a T-type input matching network. The rectifier includes a circuit layer, a dielectric substrate, and a metal ground layer stacked from top to bottom.

[0029] In some embodiments, the rectifier's circuit layer has a circuit topology based on a parallel rectifier circuit designed with a single gallium nitride Schottky diode. Figure 2 In the example, dashed box 1 is a 50-ohm input-ground coplanar waveguide (CPWG), dashed box 2 is a T-type input matching network, and dashed box 3 is an output filter circuit. The circuit layer includes an input-ground coplanar waveguide (CPWG), a T-type input matching network, a Schottky diode, and an output filter circuit. A GaN HEMT pressure sensor is directly used as the load of the rectifier, and the output of the rectifier is connected to the drain of the GaN HEMT sensor. The source of the GaN HEMT sensor is grounded, thus forming a rectifier-HEMT closed-loop circuit, powered by the rectified DC voltage. Pressure changes are sensed by modulating the HEMT channel current.

[0030] exist Figure 2 In the example, the edge of the circuit layer is also provided with multiple linearly arranged vias with a diameter of 1mm. The function of the vias is to connect the bottom metal ground and the surface metal ground to reduce the current phase difference.

[0031] Preferably, the grounded coplanar waveguide (CPWG) is a 50-ohm grounded coplanar waveguide.

[0032] In some embodiments, the dielectric substrate is Rogers 4350B material with a dielectric constant of 3.48, a loss of 0.0037, and a thickness of 0.51 mm. The circuit layer metal is 0.035 mm thick copper. The via diameter is 1 mm. Parameters were optimized for 27 GHz, and simulations determined that the rectification efficiency reached 38.6% with an input power of 24 dBm, a load resistance of 120 Ω, and a capacitance of 0.2 pF.

[0033] In some embodiments, the rectifier is a microwave rectifier operating at 27 GHz, and the load resistor is 120 Ω. The gate voltage of the rectifier-HEMT closed-loop circuit is -2.5 V.

[0034] In some embodiments, the GaN HEMT pressure sensor includes a pressure chamber with a pressure inlet. The rectifier-HEMT closed-loop circuit and PDMS can be bonded to the PCB board and built into the pressure chamber, so that the HEMT surface can be uniformly stressed and the pressure can be uniformly applied to the HEMT chip surface, controlling the internal pressure change within the range of 60kPa-170kPa.

[0035] Example 1

[0036] To optimize parameters for 27GHz, simulations determined that the rectification efficiency reached 38.6% when the input power was 24dBm, the load resistance was 120Ω, and the capacitor was 0.2pF.

[0037] like Figure 3As shown, the measured rectification efficiency at 27GHz, with a load resistance of 110Ω and an input power of 24dBm, is 39.29%. The values ​​are: W1 = 1mm, W2 = 0.4mm, W3 = 1.2mm, W4 = 0.8mm, W5 = 1.5mm, W6 = 0.6mm, W7 = 0.6mm, W8 = 0.8mm, L1 = 0.5mm, L2 = 2.9mm, L3 = 0.55mm, L4 = 2.3mm, L5 = 3.1mm, L6 = 1mm, L7 = 0.8mm, L8 = 3.4mm, L9 = 2.2mm, Wg1 = 1.65mm, Wg2 = 1.2mm, Wg3 = 2.15mm, Wg4 = 4.75mm, Wg5 = 1.55mm, Wg6 = 5.85mm, and Wg7 = 5.15mm.

[0038] Example 2

[0039] With a fixed rectifier input power of 17 dBm and a frequency of 27 GHz, measure the change in rectifier output voltage with air pressure. Figure 4 As shown, the output voltage increases significantly with increasing air pressure. The calculated sensitivity of the sensor is 0.814 mA / kPa, which is 0.62 mA / kPa / V after normalization, far exceeding the existing gallium nitride HEMT pressure sensor circuit.

[0040] Example 3

[0041] When the external pressure changes, the GaN HEMT pressure sensing system utilizes the piezoelectric polarization effect of the GaN / AlGaN heterojunction. The external pressure causes mechanical strain in the barrier layer, which induces polarization charge density on the heterojunction surface, thereby changing the two-dimensional electron gas density and causing the source-drain resistance Rds of the HEMT to change with the pressure p.

[0042] Furthermore, the relationship between the rectifier's output voltage Vout and Rds is as follows: Where η is the rectification efficiency and Pin is the input power;

[0043] When the pressure increases, causing Rds to increase, Vout increases synchronously. The increased Vout further shifts the HEMT operating point toward the saturation region, causing Rds to increase further, and subsequently Vout also increases further, forming a positive feedback loop.

[0044] The source-drain voltage Vds of the HEMT is provided by the output voltage Vout of the microwave rectifier. The output voltage and current under different pressures are measured, and the resistance change rate and sensitivity as a function of pressure are obtained as 0.827% / kPa.

[0045] Comparative Example 1

[0046] In comparison with Example 3, without microwave enhancement, a DC voltage of 1.3V was directly applied to the source and drain, and the output current under different pressures was measured. The resistance change rate and sensitivity as a function of pressure were obtained as 0.458% / kPa.

[0047] like Figure 5 As shown, the resistance change rate with microwave enhancement is significantly better than that without microwave enhancement, and the sensitivity also shows a significant difference. Therefore, it can be proven that the microwave rectifier has a significant enhancement effect on the sensor sensitivity.

[0048] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A microwave rectifier-enhanced GaN HEMT pressure sensing system, comprising a rectifier, characterized in that, The radio frequency input signal is fed into the rectifier via a DC blocking capacitor. The rectifier includes a circuit layer, a dielectric substrate and a metal ground layer stacked from top to bottom. The circuit layer includes an input ground coplanar waveguide, a T-type input matching network, a Schottky diode and an output filter circuit. The GaN HEMT pressure sensor is directly used as the load of the rectifier, and the output terminal of the rectifier is connected to the drain of the GaN HEMT pressure sensor. The source of the GaN HEMT pressure sensor is grounded. The source-drain resistance R of the Ka-band rectifier and the GaN HEMT pressure sensor is connected. ds It is directly connected as a load, thus forming a rectifier-HEMT closed-loop circuit, powered by the rectified DC voltage, and the pressure change is sensed by modulating the channel current of the GaN HEMT pressure sensor. The circuit layer of the rectifier has a circuit topology, which is a parallel rectifier circuit designed based on a single gallium nitride Schottky diode. When external pressure changes, the GaN HEMT pressure sensing system utilizes the piezoelectric polarization effect of the GaN / AlGaN heterojunction. External pressure causes mechanical strain in the barrier layer, inducing polarization charge density on the heterojunction surface, thereby altering the two-dimensional electron gas density and causing the source-drain resistance R to change. ds It changes with pressure p; The output voltage V of the rectifier out With R ds The relationship is: ,in, For rectification efficiency, P in Input power; When pressure increases, it causes R ds When V increases, out The V increases synchronously, while the V rises. out This further shifts the operating point of the GaN HEMT pressure sensor towards the saturation region, resulting in R ds Further increase, then V out This further increases, forming a positive feedback loop.

2. The GaN HEMT pressure sensing system according to claim 1, characterized in that, The edge of the circuit layer is also provided with multiple linearly arranged through holes.

3. The GaN HEMT pressure sensing system according to claim 1 or 2, characterized in that, The GaN HEMT pressure sensor includes a pressure chamber with a pressure inlet. The rectifier-HEMT closed-loop circuit is bonded to the PDMS and fixed on the PCB board and built into the pressure chamber, so that the surface of the GaN HEMT pressure sensor can be uniformly stressed.

4. The GaN HEMT pressure sensing system according to claim 1, characterized in that, The grounding coplanar waveguide is a 50-ohm grounding coplanar waveguide; the dielectric substrate is Rogers 4350B material with a dielectric constant of 3.48, a loss of 0.0037, and a thickness of 0.51 mm. The rectifier is a microwave rectifier operating at 27 GHz with a load resistance of 120 Ω; the gate voltage of the rectifier-HEMT closed-loop circuit is -2.5 V.

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