Photon antenna working at 275-296 GHz

Abstract

The invention discloses a photon antenna working at 275-296 GHz, and belongs to the field of photoelectron and terahertz communication. The UTC-PD comprises two UTC-PD bodies and a passive structure. The UTC-PD body adopts a double-mesa structure, each structure leads out an electrode by electroplating a small bonding pad, a metal bump is processed on the small bonding pad, and the UTC-PD body is electrically connected with a passive structure through flip-chip bonding. The passive structure comprises an impedance matching circuit, a power combiner circuit and a vivaldi antenna; the UTC-PD body generates a signal, and a built-in electric field is introduced by using the gradient doped absorption layer; a cliff layer is arranged between the absorbing layer and the collecting layer; and then, after the signal passes through an impedance matching circuit, the output impedance is close to 50 ohms, two combined output signals are superposed to the feed end of the Vivaldi antenna through a power combiner, and finally, the two combined output signals are converted into high-frequency electromagnetic waves with the frequency band of 275-296 GHz for radiation. Electromagnetic waves within the terahertz frequency range are generated and emitted, and the technical performance of high bandwidth, high gain and low insertion loss is achieved.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronics and terahertz communications, and relates to a photon antenna operating at 275-296 GHz. Background Art

[0002] Terahertz (THz) technology has broad prospects in the fields of broadband wireless communications, spectral analysis, security imaging and biomedical diagnosis due to its unique frequency range (0.1-10THz). Compared with traditional optical and microwave technologies, THz waves have advantages such as strong penetration, moderate wavelength and non-ionization, and can achieve unique functions in high-resolution imaging and precise spectral identification, so it is known as the "core frequency band of future technology."

[0003] In the terahertz frequency band, traditional transistor technology is difficult to meet high-frequency requirements, especially above 100 GHz, where the transistor cutoff frequency and power gain decay rapidly. Photodetectors therefore become key components and need to have characteristics such as high speed, high responsiveness, and high saturation output.

[0004] Traditional PIN photodetectors are limited by the space charge effect and are unable to meet the requirements of high bandwidth and high power output. However, the Uni-Traveling-Carrier Photodetector (UTC-PD) has been optimized in design and makes full use of electrons as the only carriers. Its photodetection performance has been significantly improved in terms of bandwidth and response speed.

[0005] UTC-PD has become a research hotspot in the field of optoelectronic devices due to its high speed, high response and weak space charge effect. However, the traditional UTC-PD design still has bottlenecks in terms of integration, impedance matching efficiency and power output consistency, which hinders its widespread application in higher frequency bands (such as 275-296GHz). Summary of the invention

[0006] The present invention proposes a photon antenna operating at 275-296 GHz, which adopts a monolithic integrated design, optimizes the impedance matching circuit, integrates an efficient power synthesizer, and innovatively designs a broadband antenna to achieve efficient generation and transmission of signals in the terahertz band. Combining the performance advantages of photodetectors with the advanced technology of integrated circuits, the present invention provides a new solution for 275-296 GHz terahertz communications and related applications.

[0007] The photon antenna operating at 275-296 GHz includes a UTC-PD body and a passive structure; the passive structure includes an impedance matching circuit, a power synthesizer circuit and a Vivaldi antenna;

[0008] There are two UTC-PD bodies in total. Each UTC-PD body adopts a double-table structure. The two identical structures have electrodes led out through electroplated small pads. Metal bumps are processed on each small pad and electrical connections are established with the passive structure processed on the quartz substrate through flip-chip bonding.

[0009] The epitaxial structure of the UTC-PD body is, from top to bottom, a P-type ohmic contact layer, a barrier layer, an absorption layer and a collection layer.

[0010] The barrier layer includes a P-type barrier layer InP and a P-type barrier layer InGaAsP;

[0011] The absorption layer includes a P-type heavily doped non-depleted absorption layer InGaAs and a P-type doped depleted absorption layer InGaAs; the absorption layer uses a gradient doping method to introduce a built-in electric field. The concentration difference brings about a potential difference, introduces a high electric field, and accelerates electrons to pass through the absorption layer;

[0012] The collection layer includes an N-type doped cliff layer InP and an N-type lightly doped collection layer InP; the presence of the cliff layer InP increases the electric field of the absorption layer while reducing the electric field of the collection layer.

[0013] The two UTC-PD bodies require two completely symmetrical impedance matching circuits to adjust the output impedance of the UTC-PD to close to 50Ω within the 275-296 GHz frequency band, thereby optimizing the power transmission efficiency in this frequency band and minimizing reflection losses.

[0014] The impedance matching circuit is processed on a quartz substrate with a relative dielectric constant of 3.78, and is composed of a series transmission line, a short-circuit stub and a MIM capacitor, wherein the series transmission line and the short-circuit stub are both in the form of a coplanar waveguide;

[0015] The output impedance of UTC-PD is adjusted to close to 50 ohms. The specific calculation formula is:

[0016] First, the output impedance of the UTC-PD body in a certain frequency band is: Z = m + j * n;

[0017] Where m is resistance and n is reactance;

[0018] Then, the impedance of the impedance matching circuit is Z1 = a + j * c;

[0019] Where a is resistance and c is reactance;

[0020] Finally, the impedance matching is calculated: that is, the impedances Z and Z1 satisfy: Z+Z1=50+j*0, that is, the output resistance of the UTC-PD superimposed with the impedance matching circuit is 50 ohms in this frequency band, and the reactance is zero.

[0021] A T-junction power combiner is used after the impedance matching circuit to superimpose the two signals after impedance matching, and the two input ends of the power combiner correspond to the output ends of the two impedance matching circuits respectively.

[0022] The T-junction power combiner consists of an input end with a length of 10um and a characteristic impedance of 50 ohms; a quarter-wavelength impedance transformation part with a length of 177um and a characteristic impedance of 70.7 ohms; and an output end with a length of 30um and a characteristic impedance of fifty ohms.

[0023] The output port of the power combiner is followed by a Vivaldi antenna, which uses coplanar waveguide feeding to radiate the terahertz signal directly into free space and maintain a high gain.

[0024] The Vivaldi antenna consists of a feed end, a radiation structure, and a reflection structure;

[0025] The feeding end adopts a coplanar waveguide structure, which is exactly the same as the structure of the third port of the T-junction power combiner.

[0026] The radiation structure consists of an exponentially changing opening structure. In order to increase the gain, slots are opened on the radiation plate of the antenna, and a metal block is added in the middle of the dielectric substrate to guide it. In order to reduce the back lobe and side lobe gain, an arc-shaped reflection structure is designed on the back of the dielectric substrate.

[0027] Furthermore, the width of each slot is 30um, the slot spacing is 100um, and the slot height decreases in units of 50um starting from 200um.

[0028] The photon antenna operating at 275-296 GHz has the following working principle:

[0029] The UTC-PD body of the photonic antenna generates signals, and uses a gradient-doped absorption layer to introduce a built-in electric field to accelerate the movement of electrons in the absorption layer; the cliff layer between the absorption layer and the collection layer enhances the electric field of the absorption layer while reducing the electric field of the collection layer; then, the signal passes through an impedance matching circuit to ensure that the output impedance of the UTC-PD is close to 50 ohms in the frequency range of 275-296 GHz, and then the output signals of the two UTC-PD signal sources combined with the impedance matching circuit are superimposed on the feeding end of the Vivaldi antenna through a power synthesizer, and finally converted into high-frequency electromagnetic waves in the 275-296 GHz frequency band for radiation.

[0030] The advantages of the present invention are:

[0031] (1) A photonic antenna operating in the 275-296 GHz frequency band adjusts the load impedance of the UTC-PD to close to 50 ohms through an impedance matching circuit in the 275-296 GHz frequency band, thereby optimizing the power transmission efficiency in this frequency band and minimizing the reflection loss.

[0032] (2) A photonic antenna operating at 275-296 GHz uses a T-junction power combiner to superimpose two impedance-matched signals and maintain a relatively low reflection coefficient at the resonant frequency.

[0033] (3) A photonic antenna operating at 275-296 GHz, with a Vivaldi antenna connected after the power combiner. This antenna can radiate the terahertz signal directly into free space and maintain a relatively high gain.

[0034] (4) A photonic antenna operating at 275-296 GHz, which integrates two UTC-PDs with a P-table diameter of 3 μm and a small pad directly with the passive structure on a quartz substrate by flip-chip bonding. This method of processing the passive structure on a quartz substrate instead of an InP wafer can improve the utilization rate of the InP wafer; at the same time, the active device UTC-PD and the passive structure can be optimized separately, reducing the experimental cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a three-dimensional structural diagram of a photon antenna operating at 275-296 GHz according to the present invention;

[0036] Figure 2 A top view of a photon antenna operating at 275-296 GHz according to the present invention;

[0037] Figure 3 A schematic diagram of an impedance matching circuit and a power combiner module used in the present invention;

[0038] Figure 4 This is a schematic diagram of the Vivaldi antenna used in the present invention;

[0039] Figure 5 It is a schematic diagram of the back reflection structure of the Vivaldi antenna in the present invention;

[0040] Figure 6 It is a schematic diagram of a curve showing a change in reflection coefficient with frequency after the power synthesis circuit, the front-end impedance matching circuit and the UTC-PD are integrated in the present invention;

[0041] Figure 7 are the E-plane radiation pattern and 3D radiation pattern of the vivaldi antenna in the present invention;

[0042] Figure 8The E-plane radiation pattern and 3D radiation pattern of the photon antenna of the present invention;

[0043] Fig. 9 The figure is a schematic diagram of a curve showing how the gain of the photon antenna of the present invention changes with frequency.

[0044] In the figure: ① is the UTC-PD body, ② is the impedance matching circuit, ③ is the power combiner, and ④ is the Vivaldi antenna. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0046] The present invention relates to a photon antenna operating in the 275-296GHz frequency band, which combines an ultrafast photodetector (UTC-PD), an impedance matching circuit, a power synthesizer and a Vivaldi antenna together through a monolithic integration process, and is used to generate and transmit electromagnetic waves in the terahertz frequency range, thereby achieving technical performances of high bandwidth, high gain and low insertion loss. The present invention significantly improves the generation and transmission efficiency of 275-296GHz terahertz signals, has the advantages of high integration, stable performance and strong reliability, and has the significance of promoting the development of terahertz communication technology and expanding its application in high-speed communication, precision measurement and biomedicine.

[0047] The photon antenna operating at 275-296 GHz, such as Figure 1 and Figure 2 As shown, it includes four parts: UTC-PD body, impedance matching circuit, power synthesizer circuit and Vivaldi antenna;

[0048] There are two UTC-PD bodies, each of which adopts a double-table structure. The diameter of the P table is 3μm, and its epitaxy from top to bottom is: P-type ohmic contact layer, barrier layer, absorption layer and collection layer;

[0049] The barrier layer includes a P-type barrier layer InP and a P-type barrier layer InGaAsP;

[0050] The absorption layer includes a P-type heavily doped non-depleted absorption layer InGaAs and a P-type doped depleted absorption layer InGaAs. The absorption layer uses a gradient doping method to introduce a built-in electric field. The concentration difference brings about a potential difference, introduces a high electric field, and accelerates electrons through the absorption layer. According to Poisson's Equation: in, is the electric potential, ρ is the charge density, and ε is the dielectric constant. It can be seen that the gradient change of doping concentration will affect the charge density, thereby generating a potential difference.

[0051] The collection layer includes an N-type doped cliff layer InP and an N-type lightly doped collection layer InP. The presence of the cliff layer InP changes the electric field distribution inside the device, causing the electric field to extend toward the absorption region, resulting in the electric field in the collection region being lower than when there is no cliff layer. This is because when a fixed reverse bias voltage is applied to the UTC-PD, if the electric field strength of a part of the UTC-PD increases, then the electric field strength of other parts will inevitably decrease; therefore, the electric field of the absorption layer is increased while the electric field of the collection layer is reduced.

[0052] The epitaxial structure of the two UTC-PD bodies is the same. The electrodes are led out through two simultaneously processed electroplated small pads. Metal bumps are processed on each small pad and electrically connected to the passive structure processed on the quartz substrate through flip-chip bonding. The passive structure includes an impedance matching circuit, a power synthesizer and a Vivaldi antenna.

[0053] Two UTC-PDs require two completely symmetrical impedance matching structures. Through the impedance matching circuit, the output impedance of the UTC-PD is adjusted to close to 50Ω in the 275-296GHz frequency band to optimize the power transmission efficiency in this frequency band and minimize the reflection loss. The specific calculation formula is:

[0054] The output impedance of UTC-PD in a certain frequency band is: Z = m + j * n; where m is resistance and n is reactance; the unit is ohm. Then, the impedance of the impedance matching circuit is Z1 = a + j * c; where a is resistance and c is reactance;

[0055] Finally, the impedance matching is calculated: that is, the impedances Z and Z1 satisfy: Z+Z1=50+j*0, that is, the output resistance of the UTC-PD superimposed with the impedance matching circuit is 50 ohms in this frequency band, and the reactance is zero.

[0056] Although the impedance matching circuit can improve the output power of the UTC-PD in this frequency band, the improvement effect is limited. Therefore, a T-junction power combiner is used after the impedance matching circuit to superimpose the two signals after impedance matching. The two input ends of the power combiner correspond to the output ends of the two impedance matching circuits, such as Figure 3 As shown; where L1 is the length of the series transmission line in the impedance matching circuit, L2 is the length of the short-circuit stub in the impedance matching circuit, L3 and L4 belong to the impedance transformation part of the power combiner, and the sum of the two is close to a quarter wavelength.

[0057] The Vivaldi antenna is connected after the output port 3 of the power combiner. The antenna uses coplanar waveguide feeding to radiate the terahertz signal directly into free space and maintain a high gain. Figure 4 As shown, L is the length of the radiation structure, and W is the opening width of the radiation structure.

[0058] The impedance matching circuit is processed on a quartz substrate with a relative dielectric constant of 3.78, and consists of a series transmission line, a short-circuit stub, and a MIM capacitor. The series transmission line and the short-circuit stub are in the form of a coplanar waveguide with a characteristic impedance of 50 ohms, and the dielectric layer of the MIM capacitor is SiNx.

[0059] The T-junction power combiner consists of an input end with a length of 10um and a characteristic impedance of 50 ohms, a quarter-wavelength impedance transformation part with a length of 177um and a characteristic impedance of 70.7 ohms, and an output end with a length of 30um and a characteristic impedance of fifty ohms.

[0060] The Vivaldi antenna consists of a feed end, a radiation structure, and a reflection structure. The feed end uses a coplanar waveguide structure, which is exactly the same as the structure of the third port of the T-junction power combiner. The radiation structure consists of an exponentially changing opening structure. In order to increase the gain, a slot is opened on the antenna's radiation plate, and a metal block is added in the middle of the dielectric substrate to guide it. In order to reduce the back lobe and side lobe gain, an arc-shaped reflection structure is designed on the back of the dielectric substrate. The reflection structure is as follows: Figure 5 shown.

[0061] The slots are located on the radiation arm, the width of each slot is 30um, the slot spacing is 100um, and the slot height decreases from 200um in units of 50um.

[0062] The photon antenna operating at 275-296 GHz has the following working principle:

[0063] The UTC-PD body of the photonic antenna generates signals, and uses the gradient-doped absorption layer to introduce a built-in electric field to accelerate the movement of electrons in the absorption layer and improve the photoelectric conversion efficiency. The cliff layer between the absorption layer and the collection layer enhances the electric field of the absorption layer while reducing the electric field of the collection layer, optimizing the flow of carriers and reducing energy loss; then, the signal passes through the impedance matching circuit to ensure that the output impedance of the UTC-PD is close to 50 ohms in the frequency range of 275-296GHz, maximizing power transmission and reducing reflection loss. Then, the output signals of the two UTC-PD signal sources combined with the impedance matching circuit are superimposed on the feeding end of the Vivaldi antenna through a power synthesizer, which enhances the output power of the system. Finally, the signal is converted into high-frequency electromagnetic waves in the 275-296GHz frequency band by the Vivaldi antenna for radiation, achieving efficient signal transmission. This design is suitable for applications such as high-frequency communications and radar detection, and improves system performance and signal transmission efficiency.

[0064] Example:

[0065] The present invention uses HFSS for electromagnetic simulation, and the simulation environment includes a substrate model based on quartz (relative dielectric constant of 3.78) and a circuit matching structure, and the operating frequency band is 275-296 GHz. The specific steps are as follows:

[0066] Step 1: UTC-PD adopts a double-table structure, and the P table diameter is 3μm, which effectively optimizes the RC time constant and improves the electron migration speed. Under 3V reverse bias, the electric field in the device depletion region is 20-40kV / cm, and the electron transit time bandwidth can reach 325GHz.

[0067] Step 2: The impedance matching circuit includes a series transmission line, a short-circuited stub, and a MIM capacitor.

[0068] Among them, the length L1 of the series transmission line is 75um, the length L2 of the short-circuit stub is 43um, and both the series transmission line and the stub are in the form of coplanar waveguide with a characteristic impedance of 50 ohms; the MIM capacitor dielectric layer is SiNx with a thickness of 0.2um.

[0069] Step 3: The T-type power combiner consists of an input end, a quarter-wavelength impedance transformation section, and an output end.

[0070] The length of the impedance transformation part is the sum of L3 and L4, which is equal to 177um. After the power synthesis circuit is integrated with the front-end impedance matching circuit and UTC-PD, it resonates at 285GHz, and the reflection coefficient is less than -39dB. Figure 6 As shown, the signals of two UTC-PDs after impedance matching can be effectively integrated.

[0071] Step 4: The length L of the Vivaldi antenna radiation structure is 1.1mm, the opening width W at the end is 0.65mm, and the thickness of the metal layer is 2um. Through optimization, the back lobe gain of the antenna is reduced to -1.9dBi. The gain of the antenna in the radiation direction reaches 8.9dBi. The E-plane radiation pattern and the 3D radiation pattern are as follows: Figure 7 shown.

[0072] Step 5: Electrode the two UTC-PDs with the same epitaxial structure through electroplating small pads, process metal bumps on the small pads, and integrate them with the passive structure processed on the quartz substrate through flip-chip bonding. The simulation results show that the gain of the photon antenna reaches 7.62dBi at 285GHz, and the E-plane radiation pattern and 3D radiation pattern are as follows: Figure 8 In the range of 275-296GHz, the output gain is above 7dBi, and the gain vs. frequency curve is shown in Fig. 9 shown.

Claims

1. A photon antenna operating at 275-296 GHz, characterized in that: Specifically includes UTC-PD body and passive structure; the passive structure includes impedance matching circuit, power synthesizer circuit and Vivaldi antenna; There are two UTC-PD bodies in total. Each UTC-PD body adopts a double-table structure. The two identical structures have electrodes led out through electroplated small pads. Metal bumps are processed on each small pad and electrical connections are established with the passive structure processed on the quartz substrate through flip-chip bonding.

2. A photon antenna operating at 275-296 GHz as claimed in claim 1, characterized in that: The double-table structure of the UTC-PD body is composed of: a P-type ohmic contact layer, a barrier layer, an absorption layer and a collection layer from top to bottom; The barrier layer includes a P-type barrier layer InP and a P-type barrier layer InGaAsP; The absorption layer includes a P-type heavily doped non-depleted absorption layer InGaAs and a P-type doped depleted absorption layer InGaAs; the absorption layer uses a gradient doping method to introduce a built-in electric field. The concentration difference brings about a potential difference, introduces a high electric field, and accelerates electrons to pass through the absorption layer; The collection layer includes an N-type doped cliff layer InP and an N-type lightly doped collection layer InP; the presence of the cliff layer InP increases the electric field of the absorption layer while reducing the electric field of the collection layer.

3. A photon antenna operating at 275-296 GHz as claimed in claim 1, characterized in that: The two UTC-PD bodies require two completely symmetrical impedance matching circuits to adjust the output impedance of the UTC-PD to close to 50Ω within the 275-296 GHz frequency band, thereby optimizing the power transmission efficiency in this frequency band and minimizing reflection losses.

4. A photon antenna operating at 275-296 GHz as claimed in claim 3, characterized in that: The impedance matching circuit is processed on a quartz substrate with a relative dielectric constant of 3.78, and is composed of a series transmission line, a short-circuit stub and a MIM capacitor, wherein the series transmission line and the short-circuit stub are both in the form of a coplanar waveguide.

5. A photon antenna operating at 275-296 GHz as claimed in claim 3, characterized in that: The load impedance of the UTC-PD is adjusted to be close to 50 ohms, and the specific calculation formula is: First, the output impedance of UTC-PD in a certain frequency band is: Z = m + j * n; Where m is resistance and n is reactance; Then, the impedance of the impedance matching circuit is Z1 = a + j * c; Where a is resistance and c is reactance; Finally, the impedance matching is calculated: that is, the impedances Z and Z1 satisfy: Z+Z1=50+j*0, that is, the output resistance of the UTC-PD superimposed with the impedance matching circuit is 50 ohms in this frequency band, and the reactance is zero.

6. A photon antenna operating at 275-296 GHz as claimed in claim 1, characterized in that: A T-junction power combiner is used after the impedance matching circuit to superimpose the two signals after impedance matching, and the two input ends of the power combiner correspond to the output ends of the two impedance matching circuits respectively.

7. A photon antenna operating at 275-296 GHz as claimed in claim 6, characterized in that: The T-junction power combiner consists of an input end with a length of 10um and a characteristic impedance of 50 ohms; a quarter-wavelength impedance transformation part with a length of 177um and a characteristic impedance of 70.7 ohms; and an output end with a length of 30um and a characteristic impedance of 50 ohms. The Vivaldi antenna is connected after the output port of the power combiner. The antenna adopts coplanar waveguide feeding to directly radiate the terahertz signal into the free space and maintain a high gain.

8. A photon antenna operating at 275-296 GHz as claimed in claim 7, characterized in that: The Vivaldi antenna consists of a feeding end, a radiation structure and a reflection structure; The feeding end adopts a coplanar waveguide structure, which is exactly the same as the structure of the third port of the T-junction power combiner; The radiation structure consists of an exponentially changing opening structure. In order to increase the gain, slots are opened on the radiation plate of the antenna, and a metal block is added in the middle of the dielectric substrate to guide it. In order to reduce the back lobe and side lobe gain, an arc-shaped reflection structure is designed on the back of the dielectric substrate.

9. A photon antenna operating at 275-296 GHz as claimed in claim 8, characterized in that: The width of the groove is 30um, the groove spacing is 100um, and the height of the groove decreases from 200um in units of 50um.

10. A photon antenna operating at 275-296 GHz as claimed in claim 1, characterized in that: The specific working principle is: The UTC-PD body of the photonic antenna generates a signal, and uses a gradient-doped absorption layer to introduce a built-in electric field to accelerate the movement of electrons in the absorption layer; the cliff layer between the absorption layer and the collection layer enhances the electric field of the absorption layer while reducing the electric field of the collection layer; then, the signal passes through an impedance matching circuit to ensure that the output impedance of the UTC-PD body is close to 50 ohms in the frequency range of 275-296GHz, and then the output signals of the two UTC-PD signal sources combined with the impedance matching circuit are superimposed on the feeding end of the Vivaldi antenna through a power synthesizer, and finally converted into high-frequency electromagnetic waves in the 275-296GHz frequency band for radiation.

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