Terahertz radiation source based on packaging of dielectric lens with air cavity

Abstract

The invention discloses a terahertz radiation source based on packaging of a dielectric lens with an air cavity, and relates to the technical field of terahertz radio frequency. The radiation source comprises a dielectric lens with an air cavity, a terahertz radiation source chip, an FR4 circuit board and a gold bonding wire. The terahertz radiation source chip is connected with the FR4 circuit board through the gold bonding wire, and the FR4 circuit board provides working voltage and a direct-current filter circuit for the terahertz radiation source chip. A core element of the terahertz radiation source adopts a resonant tunneling diode, LC oscillation is formed by utilizing the negative resistance characteristic of the resonant tunneling diode and the equivalent inductance of the radiation antenna, terahertz radiation signals are generated, and the terahertz signals are radiated to a free space through the dielectric lens with the air cavity. The terahertz radiation source is packaged by adopting the dielectric lens with the air cavity, so that the effective radiation power of the terahertz radiation source is improved, and the terahertz radiation source has the advantages of high directivity and easiness in integration, and has important application value in the aspects of long-distance terahertz communication and high-precision terahertz detection.

Description

Technical Field

[0001] The present invention relates to the field of terahertz radio frequency technology, and specifically to a terahertz radiation source based on a dielectric lens package with an air cavity. Background Art

[0002] Terahertz waves (terahertz, THz) are electromagnetic waves located between microwaves and infrared rays, with frequencies in the range of 0.1 - 10 THz. Connecting microwaves and infrared light waves, they are regarded as a transitional stage between macroscopic electronics and micro - optical photonics. The practical application of terahertz technology is inseparable from the development of terahertz sources. As an indispensable device in systems such as terahertz communication, terahertz radar, and terahertz high - precision imaging, the terahertz source plays the role of transmitting signals and providing local oscillator signals in the application system. As an important part of the radio frequency front - end, the power, efficiency, and stability of the terahertz source are core indicators and also bottleneck problems restricting the current terahertz system from moving towards practical applications.

[0003] In order to achieve an efficient and high - power terahertz radiation source, it is necessary to integrate a high - performance antenna with an oscillator circuit and couple the generated terahertz radiation into free space to realize terahertz on - chip integrated radiation technology. To radiate most of the radio frequency power in a specific direction and provide a greater coverage distance, it is best to use an antenna with high gain and directivity. Integrate a high - performance antenna with an oscillator circuit to ensure that most of the generated radio frequency power is radiated into free space.

[0004] Most of the energy of an antenna designed on a substrate with a large dielectric constant will be radiated to the substrate or through the substrate. In addition, any radiation incident on the substrate at an angle greater than the critical angle will be completely internally reflected on the top and bottom surfaces, resulting in the energy being confined inside the substrate. As long as there is continuity at the edge, the radiated energy will be confined inside the substrate and not radiated into free space, leading to a decline in antenna performance. A common solution is to use a hemispherical lens on the back to collect the power from the bottom surface of the substrate. The radiation achieved based on this method is collimated, and the half - power beam width is relatively narrow. This narrow beam width is very beneficial for scenarios requiring point - to - point communication. However, currently, the general connection method between the lens and the chip is a structure of an "inverted lens". This structure is a form of back - radiation where a silicon lens is bonded to the bottom of the chip. It is difficult to achieve a tight fit between the lens and the chip during assembly, and it is difficult to avoid the existence of gaps. These tiny air gaps will cause multiple reflections and resonances of the radiation at the lens edge, resulting in the deterioration of output matching and radiation characteristics, and this effect is more intense in dielectric lenses with a high dielectric constant. Summary of the Invention

[0005] The object of the present invention is to address the above deficiencies and propose a terahertz radiation source based on an air-cavity dielectric lens package, which uses an air-cavity dielectric lens to improve the performance of the terahertz radiation source chip, such as the effective radiation power, protects the terahertz radiation source chip, promotes the compact design and lightweight of the RF front-end, and has broad application prospects in the fields of long-distance terahertz communication and high-precision terahertz detection.

[0006] To achieve the above invention, the present invention provides the following technical solutions: A terahertz radiation source based on an air-cavity dielectric lens package, comprising a dielectric lens, a bonding wire, a terahertz radiation source chip, and an FR4 circuit board; The dielectric lens is used to achieve forward radiation with high gain, and the terahertz radiation source chip is located in the air cavity of the dielectric lens to achieve the protection and encapsulation of the terahertz radiation source chip; The terahertz radiation source chip is used to generate and radiate terahertz oscillation signals; The FR4 circuit board is used for feeding the DC signal of the terahertz radiation source chip and implementing a DC filter circuit; The bonding wire is used to connect the power supply terminal of the terahertz radiation source chip and the FR4 circuit board.

[0007] Further, the dielectric lens is provided on the upper surface of the FR4 circuit board, and the bottom of the dielectric lens is concave to form the air cavity with the FR4 circuit; the terahertz radiation source chips are all located in the air cavity, and the terahertz radiation source chips are installed on the top of the FR4 circuit, and the power supply terminals of the terahertz radiation source chips are connected to the FR4 circuit board through bonding wires.

[0008] Further, the dielectric lens is made of high-resistance silicon, nylon, fiberglass, plastic, or photosensitive resin dielectric materials.

[0009] Further, the dielectric lens is processed by micro-machining, laser processing, ultra-precision cutting, die casting, or 3D printing.

[0010] Further, the terahertz radiation source chip is a terahertz patch antenna or a terahertz slot antenna.

[0011] Further, the radiation antenna dielectric layer of the terahertz radiation source chip is made of any one or a combination of SU-8, polyimide, benzocyclobutene, and silicon nitride.

[0012] Further, the core device of the terahertz radiation source chip is a resonant tunneling diode, which forms a terahertz band LC oscillation circuit with the equivalent inductance of the radiation antenna to generate terahertz signals.

[0013] Further, the semiconductor substrate material used for the terahertz radiation source chip is any one or a combination of several of indium phosphide, gallium arsenide, and silicon.

[0014] Further, the main body of the dielectric lens is a hemispherical lens; the plane of the hemispherical lens extends outward; the optimal extension length of the hemispherical lens is L0, which is expressed as: ; wherein, the radius of the hemispherical lens is R, and the dielectric constant of the lens material is ɛ L 。

[0015] Further, the method for obtaining the optimal length value of the air cavity is as follows: Step 1, the extension length of the hemispherical lens is the initial value L1, and L1 is the sum of the optimal extension length L0 and the margin b; perform stepping according to the actual processing progress, varying from 0 to L1, and the step value is c; Step 2, for a specific extension length L2, use the optical ray tracing method to calculate the corresponding focal length F of the current extension length, and the air cavity height a0 = F - L2, wherein, L2 is nc, n is the number of steps, and 0 ≤ L2 ≤ L1; Step 3, based on the obtained dielectric lens numerical values, establish a simulation model of the lens antenna in the simulation software FECO, and simulate the air cavity height range: a0 ± 0.2 × a0, and obtain the S parameters of the lens antenna. Step 4, repeat Step 2 and Step 3 to obtain the S parameters under different extension lengths L2, import each S parameter into the simulation software ADS, and perform co - simulation analysis with the resonant tunneling diode device. Through result comparison, obtain the optimal air cavity height and radiation power value.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The terahertz radiation source with a dielectric lens package with an air cavity provided by the present invention can achieve forward radiation of the radiation source, improving the radiation efficiency of the radiation source.

[0017] 2. The terahertz radiation source with a dielectric lens package with an air cavity provided by the present invention realizes the package design of the terahertz radiation source chip by using a dielectric lens with an air cavity, reduces the volume and weight of the lens, protects the chip placed therein, improves the radiation performance of the radiation source, and promotes the compactness and lightness of the radiation source. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of a terahertz radiation source based on a dielectric lens package with an air cavity according to the present invention.

[0019] Figure 2 is a schematic structural diagram of a dielectric lens with an air cavity.

[0020] Figure 3 It is a schematic diagram of a terahertz radiation source chip.

[0021] Figure 4 It is a sectional view of the terahertz radiation source chip taken along the A-A' direction.

[0022] Figure 5 It is a sectional view of the terahertz radiation source chip taken along the B-B' direction. Specific implementation manners

[0023] The following describes the technical solutions of the exemplary embodiments of the present invention with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The described embodiments are only for illustration, rather than a limitation of the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] As Figure 1 shown, the terahertz radiation source structure provided by the embodiment includes a dielectric lens 1 with an air cavity 1-2, a bonding wire 5, a terahertz radiation source chip 4, and an FR4 circuit board 3. The main body of the terahertz radiation source chip 4 includes a radiation antenna 4-2 and a resonant tunneling diode 4-1.

[0025] The DC signal passes through the feeding network and filtering network of the FR4 circuit board 3 and is supplied with DC power to the resonant tunneling diode 4-1 through the bonding wire 5. The bias point of the resonant tunneling diode 4-1 is set to its negative resistance state, forming a terahertz oscillation with the equivalent inductance of the radiation antenna 4-2 to generate a terahertz signal. The generated terahertz signal is improved in performance of the radiation signal through the dielectric lens 1 with an air cavity 1-2, and then radiated into free space.

[0026] Referring to Figure 2 , where R is the radius of the hemisphere of the lens, L is the extended length of the lens with an air cavity 1-2, a is the height of the air cavity 1-2, and b is the width of the air cavity 1-2. For the optimal extended length L0 of the traditional extended hemispherical lens, it is related to the dielectric constant (ɛ L ) of the lens material and the radius R, and can be expressed as: .

[0027] For L and a in the lens with an air cavity 1-2, theoretically, as long as L + a is equal to the focal length F, the highest directivity coefficient can be obtained. However, considering the actual physical dimensions of the lens and the chip, the lengths of L and a will vary. Therefore, the extended length and the size of the air cavity 1-2 of the dielectric lens 1 with an air cavity 1-2 need to be further optimized by an electromagnetic simulation algorithm. The optimization process is as follows: Step 1: Use the extended length of the traditional extended hemispherical lens as the initial value L1. The length of L1 is generally slightly greater than L0. Perform stepping according to the actual processing progress, varying from 0 to L1. Step 2: For a specific extended length L2, use the ray tracing method to calculate the corresponding focal length, thereby obtaining the initial height a0 of the air cavity 1-2. L2 is the total stepping length, that is, the product of the stepping value and the number of steps.

[0028] Step 3: Based on the obtained numerical values of the dielectric lens 1, establish a simulation model of the lens antenna in the simulation software FECO. Simulate the height range of the air cavity 1-2: a0 ± 0.2 × a0, and obtain the S parameters of the lens antenna. Step 4: Repeat Step 2 and Step 3 to obtain the S parameters under different extended lengths L2. Import each S parameter into the simulation software ADS and perform co-simulation analysis with the resonant tunneling diode 4-1 device. Through result comparison, obtain the optimal height of the air cavity 1-2 and the radiation power value.

[0029] Refer to Figure 3 , the terahertz radiation source includes a resonant tunneling diode 4-1, a radiation antenna 4-2, a feeder line 4-3, a capacitor 4-4, a resistor 4-5, a ground 4-6, a substrate 4-7, a dielectric layer a 4-8, a dielectric layer b 4-9, and a metallized via 4-10.

[0030] The resonant tunneling diode 4-1 operates in the negative resistance region and is used to jointly generate terahertz signals with the radiation antenna 4-2.

[0031] The radiation antenna 4-2 is mainly used to form a terahertz oscillation with the resonant tunneling diode 4-1 and at the same time radiate the generated terahertz signal. By changing the size of the radiation antenna 4-2, a terahertz radiation source with different oscillation frequencies can be realized.

[0032] The feeder line 4-3 is mainly used to supply power to the resonant tunneling diode 4-1 with an external DC signal.

[0033] The capacitor 4-4 is mainly used to short the RF signal to the ground 4-6 during emission to reduce RF signal loss.

[0034] The resistor 4-5 is mainly used to suppress low-frequency oscillation and improve the stability of the radiation source.

[0035] The ground 4-6 is mainly used for grounding the entire radiation source.

[0036] To achieve forward radiation of the terahertz radiation source, the radiation antenna 4-2 of the terahertz radiation source based on the resonant tunneling diode 4-1 is designed using a low dielectric constant material, such as Figure 4 shown.

[0037] The dielectric layer A is mainly used to implement the feeder line 4-3, thereby reducing the influence on the entire radiation source caused by feeding through the radiation antenna 4-2.

[0038] The dielectric layer B is mainly used to implement the dielectric layer of the radiation antenna 4-2. By optimizing the thickness of the dielectric layer B and different dielectric materials, a radiation antenna 4-2 with optimal performance is obtained, improving the radiation performance of the radiation source.

[0039] A terahertz radiation source based on the encapsulation of a dielectric lens 1 with an air cavity 1-2 proposed in this embodiment can achieve forward radiation of the radiation source. The encapsulation design of the terahertz radiation source chip 4 is realized by using the dielectric lens 1 with the air cavity 1-2, reducing the volume and weight of the lens, playing a protective role for the chip placed therein, improving the radiation performance of the radiation source, and promoting the compactness and lightness of the radiation source.

[0040] The above-described specific embodiments have elaborated on the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the optimal embodiment of the present invention and does not limit the present invention. Any modifications, supplements, equivalent replacements, etc. made within the scope of the principles of the present invention shall be included within the protection scope of the present invention.

[0041] It should be understood that the above description of the specific embodiments of this patent is only an exemplary description listed for the convenience of those of ordinary skill in the art to understand the patent solution, and does not imply that the protection scope of this patent is only limited to these examples. Those of ordinary skill in the art can fully understand the technical solution of this patent and, without any creative labor, obtain more specific embodiments by combining technical features, replacing some technical features, adding more technical features, etc. to the various examples listed in this patent. All these specific embodiments are within the scope covered by the claims of this patent. Therefore, these new specific embodiments should also be within the protection scope of this patent.

Claims

1. A terahertz radiation source based on an air-cavity dielectric lens package, characterized in that, It includes a dielectric lens (1), a bonding wire (5), a terahertz radiation source chip (4), and an FR4 circuit board (3); The dielectric lens (1) is used to achieve high-gain forward radiation. The terahertz radiation source chip (4) is located in the air cavity (1-2) of the dielectric lens (1) to protect and encapsulate the terahertz radiation source chip (4); The terahertz radiation source chip (4) is used to generate and radiate terahertz oscillation signals; The FR4 circuit board (3) is used to feed the DC signal of the terahertz radiation source chip (4) and implement a DC filter circuit; The bonding wire (5) is used to connect the power supply terminal of the terahertz radiation source chip (4) and the FR4 circuit board (3).

2. The terahertz radiation source based on the encapsulation of a dielectric lens with an air cavity according to claim 1, wherein The dielectric lens (1) is disposed on the upper surface of the FR4 circuit board (3), and the bottom of the dielectric lens (1) is concave to form the air cavity (1-2) with the FR4 circuit board (3); the terahertz radiation source chips (4) are all located in the air cavity (1-2), and the terahertz radiation source chip (4) is mounted on the top of the FR4 circuit board (3), and the power supply terminal of the terahertz radiation source chip (4) is connected to the FR4 circuit board (3) through the bonding wire (5).

3. The terahertz radiation source based on the encapsulation of a dielectric lens with an air cavity according to claim 1, wherein, The dielectric lens (1) is made of a high-resistance silicon, nylon, fiberglass, plastic, or photosensitive resin dielectric material; 4. A terahertz radiation source based on an air cavity dielectric lens package according to claim 1, wherein The dielectric lens (1) is processed by micro-machining, laser processing, ultra-precision cutting, die casting, or 3D printing; 5. A terahertz radiation source based on an air cavity dielectric lens package according to claim 1, characterized in that, The terahertz radiation source chip (4) is a terahertz patch antenna or a terahertz slot antenna; 6. The terahertz radiation source based on the encapsulation of a dielectric lens with an air cavity according to claim 1, wherein, The dielectric layer of the radiation antenna (4-2) of the terahertz radiation source chip (4) is made of any one or a combination of SU-8, polyimide, benzocyclobutene, and silicon nitride; 7. A terahertz radiation source based on encapsulation of a dielectric lens with an air cavity according to claim 1, characterized in that, The core device of the terahertz radiation source chip (4) is a resonant tunneling diode (4-1), which forms a terahertz-band LC oscillation circuit with the equivalent inductor of the radiation antenna (4-2) to generate terahertz signals; 8. A terahertz radiation source based on an air cavity dielectric lens package according to claim 1, characterized in that The semiconductor substrate material used for the terahertz radiation source chip (4) is any one or a combination of indium phosphide, gallium arsenide, and silicon; 9. The terahertz radiation source based on the encapsulation of a dielectric lens with an air cavity according to claim 1, wherein The main body of the dielectric lens (1) is a hemispherical lens; the plane of the hemispherical lens extends outward; the optimal extension length of the hemispherical lens is L0, expressed as: ; Among them, the radius of the hemispherical lens is R, and the dielectric constant of the lens material is ɛ L .

10. A terahertz radiation source based on an air cavity dielectric lens package according to claim 9, characterized in that, The optimal length value of the air cavity (1-2) is obtained as follows: Step 1, the extended length of the hemispherical lens is the initial value L1, and L1 is the sum of the optimal extended length L0 and the margin b; step by step according to the actual processing progress, it changes from 0 to L1, and the step value is c; Step 2, for a specific extended length L2, use the ray tracing method to calculate the corresponding focal length F of the current extended length. The height a0 of the air cavity (1-2) is F - L2, where L2 is nc, n is the number of steps, and 0 ≤ L2 ≤ L1; Step 3, based on the obtained numerical values of the dielectric lens (1), establish a simulation model of the lens antenna in the simulation software FECO, simulate the height range of the air cavity (1-2): a0 ± 0.2 × a0, and obtain the S parameters of the lens antenna Step 4: Repeat Step 2 and Step 3 to obtain the S-parameters at different extended lengths L2. Import each S-parameter into the simulation software ADS and perform co-simulation analysis with the resonant tunneling diode (4-1) device. Through result comparison, obtain the optimal height of the air cavity (1-2) and the radiation power value.

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