A Gunn diode oscillating signal source based on dielectric integrated waveguide resonant cavity and its working method

Abstract

The present invention relates to a Gunn diode oscillation signal source based on a dielectric integrated waveguide resonant cavity and a working method thereof, comprising: a top layer, a middle layer and a bottom layer from top to bottom; the top layer is a coplanar waveguide multilayer metal feeding and signal output structure, the middle layer is an insulating plate structure, and the bottom layer is a metal structure for Gunn diode integration; a via structure that runs through the top layer, the middle layer and the bottom layer. The present invention has a stable output frequency, a relatively simple structure, low noise, a compact shape, light weight, easy circuit integration, and high cost-effectiveness.

Description

Technical Field

[0001] The invention discloses a Gunn diode oscillating signal source based on a dielectric integrated waveguide resonant cavity and a working method thereof, belonging to the cross-technical field of electromagnetic field and microwave technology and semiconductor technology. Background Art

[0002] In recent years, due to the research and development of some new technologies and new materials, terahertz technology has developed rapidly, and the research on terahertz wave radiation sources has also been taken seriously in the corresponding fields, and has set off a wave of enthusiasm. At present, the semiconductor solid-state signal sources used in the terahertz field are mainly negative resistance devices, such as Gunn diodes, resonant tunneling diodes (RTDs), and avalanche diodes (IMPATT diodes). Among these diodes, Gunn diodes have many advantages such as high operating frequency, strong stability, high reliability, low noise, wide bandwidth, low power supply voltage, and long working life. At present, negative resistance devices are becoming more and more important in semiconductor solid-state radiation sources in the terahertz field. Therefore, among many transfer electron devices, Gunn diodes have great potential for application in the terahertz frequency band.

[0003] In 1963, Gunn (JB Gunn) discovered that when a constant DC voltage higher than the critical value is applied to the contact electrodes on the opposite sides of a small piece of N-type gallium arsenide, an oscillating current is generated. This phenomenon of generating high-frequency current in the semiconductor body is called the Gunn effect. The Gunn diode has five operating modes: ideal uniform field mode, limited space charge accumulation mode, quenched dipole layer mode, accumulation layer mode and transit time dipole domain mode; the first four modes are prone to frequency drift, while the fifth mode resonant frequency is locked to the frequency of the external resonant circuit and will not drift. When the Gunn diode is placed in a resonant cavity with a high quality coefficient (Q), the oscillation frequency of the Gunn diode is no longer simply affected by the channel length like other modes, but is near the resonant frequency of the resonant cavity. This working mode is called the external resonant mode. The Gunn diode working in the external resonant mode not only has a very stable oscillation frequency, but also can change with the change of the resonant frequency of the resonant cavity, and the adjustment range can reach 40%.

[0004] Over the past few decades, Gunn diode waveguide oscillators have been widely used due to their high power, low noise, small size and high frequency performance. From the main materials of the Gunn diode to the waveguide cavity, its seemingly simple structure uses extremely complex and finely tuned geometries and materials to achieve optimal performance. Although transistor-type VCOs that are easy to mass-produce are more widely used, Gunn diode waveguide oscillators are more in line with the needs of the growing field of millimeter-wave test and measurement.

[0005] Traditional devices have the disadvantage of frequency limitation and demanding working environment. They also have obvious defects such as large packaging volume and inability to integrate, which limits their application in high frequency, integrated and other fields. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a Gunn diode oscillation signal source based on a dielectric integrated waveguide resonant cavity.

[0007] The present invention realizes a terahertz and millimeter wave signal source with stable output frequency by processing a dielectric integrated waveguide resonant cavity on a circuit board and integrating it with a Gunn diode. The structure is simple, the plane is easy to process, and it is conducive to planar circuit integration. At the same time, it has a high Q factor and can be integrated with a planar Gunn diode or a vertical structure. The signal source has the advantages of stable output signal frequency, small size, and low cost.

[0008] The present invention also provides a working method of the above-mentioned Gunn diode oscillator signal source based on dielectric integrated waveguide resonant cavity

[0009] Terminology explanation:

[0010] Room temperature, 25℃.

[0011] The technical solution of the present invention is

[0012] A Gunn diode oscillation signal source based on a dielectric integrated waveguide resonant cavity, comprising:

[0013] The top layer, middle layer and bottom layer from top to bottom; the top layer is a cpw (coplanar waveguide) multi-layer metal structure, the middle layer is an insulating plate structure, and the bottom layer is a cpw (coplanar waveguide) multi-layer metal structure;

[0014] Via structures that penetrate the top, middle, and bottom layers.

[0015] Preferably according to the present invention, the cpw multilayer metal structure includes from top to bottom a 4-6um metal Au layer, an 8-14um metal Ti layer, and an 8-12um metal Cu layer.

[0016] Further preferably, the thickness of the metal Au layer is 5 um, the thickness of the metal Ti layer is 12 um, and the thickness of the metal Cu layer is 10 um.

[0017] Preferably according to the present invention, the middle layer is made of Rogers-4350B sheet material with a thickness of 4 mil.

[0018] Preferably, according to the present invention, the via structure is a structure that penetrates the top layer, the middle layer and the bottom layer from top to bottom, and the via structure includes a plurality of regularly and closely arranged cylindrical holes with a diameter of 50-200 um.

[0019] Further preferably, the diameter of the cylindrical hole is 100 um.

[0020] Preferably, according to the present invention, the cpw multilayer metal structure is prepared by the following method, which specifically comprises the following steps:

[0021] (1) Using electron beam evaporation technology, an 8-12um metal Cu layer, an 8-14um metal Ti layer, and a 4-6um metal Au layer are sequentially evaporated on the surface of the Rogers sheet from bottom to top.

[0022] (2) using photolithography technology, etching a top-layer coplanar waveguide multilayer metal feeding and signal output structure and a bottom-layer cpw multilayer metal structure for Gunn diode integration on the metal surface evaporated in step (1);

[0023] (3) wet etching the structure after photolithography in step (2);

[0024] (4) placing the sample treated in step (3) in a degumming solution for degumming.

[0025] Further preferably, in step (2), the photolithography technology is laser direct writing or ultraviolet photolithography.

[0026] Further preferably, the specific implementation process of step (3) is:

[0027] First, the sample after photolithography in step (2) was placed in a 20% by mass KI solution at room temperature for 1 hour, and the metal Au layer and the metal Ti layer fell off;

[0028] Then, the sample was placed in a 50% FeCl3 solution at room temperature for 5 hours, and the metal Cu layer fell off, exposing the middle layer.

[0029] Further preferably, the specific implementation process of step (4) is: the sample processed in step (3) is allowed to stand at room temperature for 5 minutes and then taken out, at which time the remaining pattern of the sample is the top-layer coplanar waveguide multi-layer metal feeding and signal output structure and the bottom-layer cpw multi-layer metal structure for Gunn diode integration.

[0030] The working method of the Gunn diode oscillator signal source based on the substrate integrated waveguide resonant cavity structure comprises the following steps:

[0031] A. The top anode of the planar Gunn diode is a dual-port, one end of which is applied with the working voltage and the other end is connected to the Gunn diode oscillator signal source;

[0032] The bottom cathode of the planar Gunn diode is connected to the cathode of the bottom cpw multilayer metal structure for Gunn diode integration, and the top anode of the planar Gunn diode is connected to the anode of the bottom cpw multilayer metal structure for Gunn diode integration;

[0033] B. applying an operating voltage to the middle resonant patch of the cpw multilayer metal structure for Gunn diode integration at the bottom layer;

[0034] C. The via array, the top layer, the bottom layer and the middle layer constitute a SIW resonant cavity; the signal generated by the planar Gunn diode is coupled with the SIW resonant cavity through the middle resonant patch to generate resonance, so that the Gunn diode works in an external resonant mode;

[0035] D. The signal generated by the planar Gunn diode is output through the top coplanar waveguide multi-layer metal feeding and signal output structure, thereby achieving the purpose of high-frequency signal output.

[0036] Preferably, according to the present invention, the intermediate conductor of the intermediate resonant patch is a coplanar waveguide transmission line with Ohm characteristic impedance, the width of the coplanar waveguide transmission line is 0.3-0.5mm, the length of the coplanar waveguide transmission line is 1-2mm, and the gap width between the intermediate conductor and the conductors on both sides is 0.04-0.07mm.

[0037] Further preferably, the ohmic characteristic impedance of the selected coplanar waveguide transmission line is 50 ohms.

[0038] Preferably according to the present invention, the horizontal spacing between the anode and cathode coupling interfaces of the planar Gunn diode is 8-12 um.

[0039] The beneficial effects of the present invention are:

[0040] 1. The Gunn diode oscillator signal source structure based on the dielectric integrated waveguide resonant cavity of the present invention has a relatively simple structure, generates low noise content, is compact and light in size, and has high cost-effectiveness.

[0041] 2. The Gunn diode oscillation signal source structure based on the dielectric integrated waveguide resonant cavity of the present invention adopts a sandwich structure of CPW-insulating layer-CPW combination from top to bottom, which is simple to operate, easy to process, and saves production costs.

[0042] 3. The Gunn diode oscillation signal source structure of the present invention is based on the dielectric integrated waveguide resonant cavity, which improves the traditional imprinting and etching technology, facilitates small-batch production, and avoids waste of resources.

[0043] 4. The present invention uses a coplanar waveguide transmission line structure group to dissipate heat using a copper plate, which effectively solves the high-current thermal effect of the Gunn diode and increases the reliability of the device.

[0044] 5. The present invention adopts a monolithic microwave integrated circuit and coplanar waveguide technology and adopts a self-biased circuit structure, which simplifies the circuit structure, is easy to implement monolithic integration, and does not require complex waveguide packaging components.

[0045] 6. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity of the present invention can be used to test the external resonant frequency of the planar Gunn diode.

[0046] 7. The Gunn diode oscillation signal source structure of the present invention is based on the dielectric integrated waveguide resonant cavity. It adopts the combination of planar Gunn diode and SIW resonant cavity, has a high and adjustable operating frequency, is easy to integrate, has a small size, and can work well at room temperature (15-40 degrees Celsius). BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the structure of the Gunn diode oscillation signal source of the present invention;

[0048] Figure 2 A schematic plan view of a cpw multilayer metal structure for Gunn diode integration at the bottom layer of the Gunn diode oscillation signal source of the present invention;

[0049] Figure 3 It is a side schematic diagram of a Gunn diode oscillator signal source based on a substrate integrated waveguide resonant cavity structure of the present invention;

[0050] Figure 4 Schematic diagram of the integration of the SIW resonant cavity and the planar Gunn diode of the present invention;

[0051] Figure 5 It is a schematic diagram of the simulation results of the resonant frequency of the Gunn diode oscillator signal source based on the substrate integrated waveguide resonant cavity structure of the present invention when it is working.

[0052] 1. Top layer, 2. Via structure, 3. Anode of cpw multilayer metal structure, 4. Middle resonant patch, 5. Cathode of cpw multilayer metal structure, 6. Bottom layer, 7. Planar Gunn diode, 8. Middle layer. DETAILED DESCRIPTION

[0053] The present invention will be further defined below in conjunction with the accompanying drawings and embodiments, but is not limited thereto.

[0054] Example 1

[0055] A Gunn diode oscillating signal source based on a dielectric integrated waveguide resonant cavity, such as Figure 1 , Figure 3 As shown, including:

[0056] From top to bottom, the top layer 1, the middle layer 8 and the bottom layer 6; the top layer 1 is a cpw (coplanar waveguide) multilayer metal structure, the middle layer 8 is an insulating plate structure, and the bottom layer 6 is a cpw (coplanar waveguide) multilayer metal structure;

[0057] A via structure 2 penetrates the top layer 1 , the middle layer 8 and the bottom layer 6 .

[0058] Example 2

[0059] The difference between the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity described in Example 1 is that:

[0060] The cpw multilayer metal structure includes a 4-6um metal Au layer, an 8-14um metal Ti layer, and an 8-12um metal Cu layer from top to bottom. The metal Au layer is to prevent the metal Cu layer from oxidizing and corroding, which affects the structural performance, and the metal Ti layer is to increase the adhesion of the Au layer and prevent it from falling off.

[0061] The middle layer 8 is made of Rogers-4350B with a thickness of 4 mil, which provides low dielectric constant and low loss, and its price is a fraction of traditional microwave materials, saving production costs and improving the Q factor of the resonant cavity, but the material selection is not limited to this.

[0062] The via structure 2 is a structure that penetrates the top layer 1, the middle layer 8 and the bottom layer 6 from top to bottom, and the via structure 2 includes a plurality of regularly and closely arranged cylindrical holes with a diameter of 50-200 um.

[0063] Example 3

[0064] The difference between the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity described in Example 2 is that:

[0065] The thickness of the metal Au layer is 5um, the thickness of the metal Ti layer is 12um, and the thickness of the metal Cu layer is 10um.

[0066] The diameter of the cylindrical hole is 100um.

[0067] Example 4

[0068] The difference between the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity described in Example 1 is that:

[0069] The cpw multilayer metal structure is manufactured by evaporating a metal layer on the surface of the Rogers plate, photolithography, and wet etching. The cpw multilayer metal structure is prepared by the following method, which specifically includes the following steps:

[0070] (1) Using electron beam evaporation technology, an 8-12um metal Cu layer, an 8-14um metal Ti layer, and a 4-6um metal Au layer are sequentially evaporated on the surface of the Rogers sheet from bottom to top.

[0071] (2) using photolithography technology, etching the top layer coplanar waveguide (CPW) multilayer metal feeding and signal output structure and the bottom layer 6 CPW multilayer metal structure for Gunn diode integration on the metal surface evaporated in step (1); Figure 2 As shown; the lithography technology is laser direct writing or ultraviolet lithography.

[0072] (3) wet etching the structure after photolithography in step (2); the specific implementation process is as follows:

[0073] First, the sample after photolithography in step (2) was placed in a 20% by mass KI solution at room temperature for 1 hour, and the metal Au layer and the metal Ti layer fell off;

[0074] Then, the sample was placed in a 50% by mass FeCl3 solution at room temperature for 5 hours, and the metal Cu layer fell off, exposing the intermediate layer 8.

[0075] (4) The sample processed in step (3) is placed in a degumming solution for degumming. The specific implementation process is: the sample processed in step (3) is left to stand at room temperature for 5 minutes and then taken out. At this time, the remaining pattern of the sample is the top coplanar waveguide (CPW) multilayer metal feeding and signal output structure and the bottom 6 CPW multilayer metal structure for Gunn diode integration.

[0076] Example 5

[0077] The working method of the Gunn diode oscillator signal source based on the substrate integrated waveguide (SIW) resonant cavity structure described in any one of Examples 1-4 comprises the following steps:

[0078] A. The top anode of the planar Gunn diode 7 is a dual-port, one end of which is applied with a working voltage and the other end is connected to a Gunn diode oscillator signal source;

[0079] The bottom cathode of the planar Gunn diode 7 is connected to the cathode 5 of the cpw multilayer metal structure for Gunn diode integration of the bottom layer 6, and the top anode of the planar Gunn diode 7 is connected to the anode 3 of the cpw multilayer metal structure for Gunn diode integration of the bottom layer 6; Figure 4 shown.

[0080] B. applying a working voltage to the middle resonant patch 4 of the cpw multilayer metal structure for Gunn diode integration on the bottom layer 6;

[0081] C. The via array 2, the top layer 1, the bottom layer 6 and the middle layer 8 constitute a SIW resonant cavity; the signal generated by the planar Gunn diode 7 is coupled with the SIW resonant cavity through the middle resonant patch 4 to produce resonance, so that the Gunn diode 7 operates in an external resonant mode; the operating frequency of its external resonance can be adjusted between 1 GHz and 120 GHz according to the size changes of the upper and lower layers of the cpw multi-layer metal structure.

[0082] D. The signal generated by the planar Gunn diode 7 is output through the top coplanar waveguide (cpw) multi-layer metal feeding and signal output structure, thereby achieving the purpose of high-frequency signal output.

[0083] The middle conductor of the middle resonant patch 4 is a coplanar waveguide transmission line with Ohm characteristic impedance, the width of the coplanar waveguide transmission line is 0.3-0.5mm, the length of the coplanar waveguide transmission line is 1-2mm, and the gap width between the middle conductor and the conductors on both sides is 0.04-0.07mm.

[0084] The ohmic characteristic impedance of the coplanar waveguide transmission line is 50 ohms.

[0085] The horizontal spacing between the anode and cathode coupling interfaces of the planar Gunn diode 7 is 8-12 um.

[0086] Both the top layer 1 and the bottom layer 6 use metal copper as the basic layer, which enhances the heat dissipation of the structure while ensuring signal transmission.

[0087] The simulation results of the resonant frequency of the Gunn diode oscillator signal source based on the substrate integrated waveguide resonant cavity structure are shown in the figure below. Figure 5 As shown, Figure 5 In the figure, the upper curve is S11 and the lower curve is S21. The simulation results show that the operating frequency of the Gunn diode oscillator signal source based on the substrate integrated waveguide resonant cavity structure of the present invention can generate resonance at 38Ghz, 60Ghz and 85Ghz, so that the Gunn diode reaches the external resonant mode, and the output frequency can be adjusted between 1 and 120 GHz as the size changes. The simulation results prove that the Gunn diode oscillator signal source based on the substrate integrated waveguide resonant cavity structure of the present invention achieves the purpose of stable output of high-frequency signals.

Claims

1. A working method of a Gunn diode oscillator signal source based on a dielectric integrated waveguide resonant cavity, characterized in that: The steps include: A. The top anode of the planar Gunn diode is a dual-port, one end of which is applied with the working voltage and the other end is connected to the Gunn diode oscillator signal source; The bottom cathode of the planar Gunn diode is connected to the cathode of the bottom cpw multilayer metal structure for Gunn diode integration, and the top anode of the planar Gunn diode is connected to the anode of the bottom cpw multilayer metal structure for Gunn diode integration; B. applying an operating voltage to the middle resonant patch of the cpw multilayer metal structure for Gunn diode integration at the bottom layer; C. The via array, the top layer, the bottom layer and the middle layer constitute a SIW resonant cavity; the signal generated by the planar Gunn diode is coupled with the SIW resonant cavity through the middle resonant patch to generate resonance, so that the Gunn diode works in an external resonant mode; D. The signal generated by the planar Gunn diode is output through the top coplanar waveguide multi-layer metal feeding and signal output structure, thereby achieving the purpose of high-frequency signal output; The Gunn diode oscillation signal source includes: a top layer, a middle layer and a bottom layer from top to bottom; the top layer is a cpw multilayer metal structure, the middle layer is an insulating plate structure, and the bottom layer is a cpw multilayer metal structure; the cpw multilayer metal structure includes a metal Au layer, a metal Ti layer, and a metal Cu layer from top to bottom; a via structure that runs through the top layer, the middle layer and the bottom layer; and multiple via structures constitute a via array.

2. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 1, characterized in that: The cpw multilayer metal structure includes, from top to bottom, a 4-6um metal Au layer, an 8-14um metal Ti layer, and an 8-12um metal Cu layer.

3. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 2, characterized in that: The thickness of the metal Au layer is 5 um, the thickness of the metal Ti layer is 12 um, and the thickness of the metal Cu layer is 10 um.

4. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 1 is characterized in that: The via structure is a structure that penetrates the top layer, the middle layer and the bottom layer from top to bottom, and the via structure includes a plurality of regularly and closely arranged cylindrical holes with a diameter of 50-200 um.

5. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 4, characterized in that: The diameter of the cylindrical hole is 100um.

6. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 1, characterized in that: The middle layer is made of Rogers-4350B sheet material with a thickness of 4 mil.

7. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 1, characterized in that: The cpw multilayer metal structure is prepared by the following method, which specifically includes the following steps: (1) Using electron beam evaporation technology, 8-12um metal Cu layer, 8-14um metal Ti layer, and 4-6um metal Au layer are sequentially evaporated on the surface of Rogers sheet from bottom to top; (2) using photolithography technology, etching a top-layer coplanar waveguide multilayer metal feeding and signal output structure and a bottom-layer cpw multilayer metal structure for Gunn diode integration on the metal surface evaporated in step (1); (3) wet etching the structure after photolithography in step (2); (4) placing the sample treated in step (3) in a degumming solution for degumming.

8. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 7, characterized in that: The specific implementation process of step (3) is as follows: First, the sample after photolithography in step (2) was placed in a 20% by mass KI solution at room temperature for 1 hour, and the metal Au layer and the metal Ti layer fell off; Then, the sample was placed in a 50% FeCl3 solution at room temperature for 5 hours, and the metal Cu layer fell off, exposing the middle layer.

9. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 5, characterized in that: The specific implementation process of step (4) is: the sample processed in step (3) is left standing at room temperature for 5 minutes and then taken out. At this time, the remaining pattern of the sample is the top-layer coplanar waveguide multi-layer metal feeding and signal output structure and the bottom-layer cpw multi-layer metal structure for Gunn diode integration.

10. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 1, characterized in that: The middle conductor of the middle resonant patch is a coplanar waveguide transmission line with Ohm characteristic impedance, the width of the coplanar waveguide transmission line is 0.3-0.5mm, the length of the coplanar waveguide transmission line is 1-2mm, and the gap width between the middle conductor and the conductors on both sides is 0.04-0.07mm.

11. The working method of the Gunn diode oscillation signal source based on the dielectric integrated waveguide resonant cavity according to claim 10, characterized in that: The ohmic characteristic impedance of the selected coplanar waveguide transmission line is 50 ohms.

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