A multi-bit terahertz phase shifter based on reflection-transmission combined with phase shifting method

Abstract

The present invention relates to the technical field of electromagnetic functional devices, and in particular to a multi-bit terahertz phase shifter based on a reflection-transmission combined with phase shifting method, including an input waveguide, a waveguide-microstrip line transition structure on a large-area substrate, a reflective terahertz phase shifting structure, a transmission terahertz phase shifting structure, a microstrip line-waveguide transition structure on a large-area substrate, and an output waveguide. The multi-bit terahertz phase shifter based on a reflection-transmission combined with phase shifting method proposed in the present invention adopts a waveguide-microstrip line transition structure of a large-area substrate to reduce the insertion loss of the device, avoid excessive reflection from damaging the terahertz source, and is easy to work with other terahertz modules to achieve good working results. The present invention adopts a coding voltage to control the on-off of a diode to achieve 360° multi-bit terahertz phase regulation. The coding voltage can be conveniently combined with a digital baseband circuit to achieve high-speed information transmission.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic functional devices, and in particular to a multi-bit terahertz phase shifter based on a reflection-transmission combined with phase shifting method. Background Art

[0002] Terahertz waves are electromagnetic waves with a frequency range of 0.1THz to 10THz. Within the electromagnetic field, terahertz waves have yet to be fully developed, and various types of terahertz devices are still under research. However, terahertz dynamic devices have shown great potential in terahertz communication systems, terahertz imaging systems, terahertz radar systems, terahertz biodetection, and other fields, and are a key area for the future development of electromagnetic technology.

[0003] The main function of a digital phase shifter is discrete phase shifting, with a phase shift step of 360° / 2N (N = 1, 2, 3, 4, ...), where N is the number of bits in the phase shifter. Since 360° and 0° are the same state, N phase shifters only need to achieve a total phase shift of 360° × (2N-1) / 2N.

[0004] In wireless communication systems, phase-shift keying (PSK) is often used to transmit information. The transmitter encodes the information into a PSK code, which is then used to control the phase shift of the carrier before transmitting it through the antenna. Upon reception, a demodulated signal carrying the information is obtained through coherent demodulation. In terahertz communication systems, significantly increasing the transmission rate is crucial, and PSK is highly feasible for achieving this goal. A key component of this approach is the terahertz phase shifter.

[0005] In radar systems, traditional radar transmitting antennas require mechanical rotation to achieve multi-directional scanning, resulting in a bulky mechanical structure and limited scanning speed. Phased array radar, on the other hand, can control the direction of its beam without mechanical movement, expanding its applicability and enabling more effective detection of high-speed, maneuvering targets. Terahertz phased array radar is a new type of radar characterized by its small size, high speed, narrow beam, and high integration. However, one of its core components, the terahertz phase shifter, remains underdeveloped.

[0006] To meet the needs of phase modulation technologies in communications and radar systems, multi-bit terahertz phase shifters with simple structures and low insertion loss are key to terahertz phase shifting technology. Reflective terahertz continuous phase shifters based on varactor diodes have been proposed, but they fail to achieve 360° digital multi-phase shifting. The specific issues are low phase shift linearity and high insertion loss, making it impossible to achieve low insertion loss multi-bit terahertz 360° phase shifting.

[0007] Through the above analysis, the problems and defects of the existing technology are as follows:

[0008] (1) There are few feasible terahertz phase shifting technology solutions available, and high-performance terahertz phase shifters have yet to be developed;

[0009] (2) The existing phase shifting technology structure has large insertion loss and low linearity when the phase shift is carried out over a large range. Summary of the Invention

[0010] (1) Technical issues to be resolved

[0011] There are few solutions to the existing terahertz phase shifting technology, and high-performance terahertz phase shifters have yet to be developed. The existing phase shifting technology structure has large insertion loss and low linearity when shifting phase over a large range. A multi-bit terahertz phase shifter based on a reflection-transmission combined phase shifting method is provided to solve the problem.

[0012] (2) Technical solution

[0013] In response to the problems and requirements of the background technology, the present invention proposes a multi-bit terahertz phase shifter based on a reflection-transmission combined phase shifting method, which can achieve 360° multi-bit terahertz phase shift while having low insertion loss. The multi-bit terahertz phase shifter based on a reflection-transmission combined phase shifting method utilizes a combination of reflective terahertz phase shifting and transmission terahertz phase shifting methods, specifically:

[0014] 1. Reflective terahertz phase shifting method: A reflection phase shifting circuit is constructed using a 3dB directional coupler and a metal reflection structure embedded with a diode. The diode is controlled by voltage to switch on and off. When the terahertz wave enters the reflection port of the directional coupler, a phase shift is generated due to the change in reflection impedance. When reflected to the output end, a phase shift of 0 to 180° can be achieved.

[0015] 2. Transmission-based terahertz phase shifting: Diodes are embedded in open metal branches. Voltage is used to control the diode's on / off state, changing the branch's impedance. This causes the terahertz wave passing through the structure to undergo a phase shift, achieving small phase shifts, such as 45° or 22.5°. Multiple metal branches are stacked via matching microstrip lines and fed together, reducing feed complexity and enabling phase control in small increments, with a total phase shift of up to 180°.

[0016] The two methods are combined through matching microstrips and superimposed on each other to achieve 360° multi-bit terahertz phase control. The specific technical solutions adopted by the present invention are as follows:

[0017] A multi-bit terahertz phase shifter based on a reflection-transmission combined phase shifting method includes an input waveguide, a waveguide-microstrip line transition structure on a large-area substrate, a reflective terahertz phase shifting structure, a transmission terahertz phase shifting structure, a microstrip line-waveguide transition structure on a large-area substrate, and an output waveguide.

[0018] As a preferred technical solution, the input waveguide is connected to the waveguide-microstrip line transition structure of the large-area substrate to input the terahertz wave; the microstrip line-waveguide transition structure of the large-area substrate is connected to the output waveguide to output the phase-shifted terahertz wave.

[0019] As a preferred technical solution, the waveguide-microstrip line transition structure of the large-area substrate is symmetrical to the microstrip line-waveguide transition structure of the large-area substrate; the waveguide-microstrip line transition structure of the large-area substrate includes a reduced-height waveguide, an L-shaped metal probe, and a matching recessed cavity, wherein the reduced-height waveguide serves as a transition from a standard waveguide to a waveguide of custom size; the L-shaped metal probe is located on the large-area substrate and embedded in the end of the reduced-height waveguide, so that the terahertz wave is converted from a waveguide mode to a microstrip mode; the matching recessed cavity is a recess in the cavity, the depth of the recess is tangent to the large-area substrate, and the edge of the recess is tangent to the L-shaped metal probe; the L-shaped metal probe is combined with the matching recessed cavity.

[0020] As an optimal technical solution, the reflective terahertz phase shift structure includes a 3dB directional coupler, a phase-shifting metal strip, a diode, a matching metal strip, a high- and low-resistance feeding structure, and a high- and low-resistance grounding structure; the 3dB directional coupler divides a terahertz wave into two terahertz waves with a phase difference of 90°, which arrive at two diodes respectively; the phase-shifting metal strip is located between the 3dB directional coupler and the diode, and is connected in parallel with the diode to increase the phase shift; the diode connects the 3dB directional coupler and the matching metal strip, and the on and off of the diode can cause a huge change in the reflection impedance, thereby obtaining a phase shift of the reflected wave; the matching metal strip optimizes the phase shift and insertion loss to ensure low insertion loss and high phase shift; the high- and low-resistance feeding structure consists of a thin high-impedance metal strip and a large low-impedance metal block, which is connected to the matching metal strip to feed the control voltage; the high- and low-resistance grounding structure consists of a thin high-impedance metal strip and a large low-impedance metal block, which connects the 3dB directional coupler and the cavity to provide a reference zero level for the entire device.

[0021] As an optimal technical solution, a transmission-type terahertz phase-shifting structure includes a front-end metal branch, a diode, a rear-end metal branch, a matching microstrip line between branches, and a common feeding structure; the front-end metal branch and the rear-end metal branch together constitute an open metal branch, which plays a role in adjusting the branch impedance; the diode connects the front-end metal branch and the rear-end metal branch; the matching microstrip line between branches matches multiple metal branches with each other, so that the phase shifts of multiple metal branches are linearly superimposed while maintaining low insertion loss; the common feeding structure feeds the diodes on multiple metal branches at the same time, reducing the feeding complexity and obtaining the target phase shift degree.

[0022] As a preferred technical solution, the size and shape of the height-reduced waveguide, L-shaped metal probe, and matching recessed cavity in the waveguide-microstrip line transition structure of the large-area substrate are adjustable to achieve high-efficiency terahertz wave transition from waveguide to microstrip line.

[0023] As a preferred technical solution, the size and shape of the phase-shifting metal strips and matching metal strips in the reflective terahertz phase-shifting structure are adjustable, which changes the phase shift of the terahertz wave and the corresponding insertion loss to obtain a phase shift of 0-180° with low insertion loss.

[0024] As a preferred technical solution, the diodes used in the reflective terahertz phase-shift structure and the transmission terahertz phase-shift structure are PIN diodes, Schottky diodes or high electron mobility transistors.

[0025] As a preferred technical solution, the size and shape of the front and rear metal branches in the transmission-type terahertz phase-shifting structure can be adjusted to obtain the required small-degree phase shift step, and the matching microstrip lines and common feeding structure between the branches can be adjusted according to the required phase shift and insertion loss requirements.

[0026] As a preferred technical solution, the material of the large-area substrate is sapphire, quartz, silicon, gallium arsenide or silicon carbide.

[0027] (3) Beneficial effects

[0028] The beneficial effects of the present invention are:

[0029] (1) In order to solve the problems of few terahertz phase shifting technology solutions and large insertion loss and low linearity of existing phase shifting technologies during large-scale phase shifting, the present invention combines reflective terahertz phase shifting with transmission terahertz phase shifting methods, proposes a new transmission terahertz phase shifting structure, and proposes a waveguide-microstrip line transition structure for large-area substrates. Ultimately, low insertion loss multi-bit terahertz wave phase shifting is achieved with extremely high linearity, which promotes the development of terahertz phase control technology.

[0030] (2) The multi-bit terahertz phase shifter based on the reflection-transmission combined phase shifting method proposed in the present invention adopts a waveguide-microstrip line transition structure with a large-area substrate to reduce the insertion loss of the device, avoid excessive reflection damaging the terahertz source, and is easy to work with other terahertz modules to achieve good working effects.

[0031] (3) The present invention uses a coding voltage to control the on and off of the diode to achieve 360° multi-bit terahertz phase control. The coding voltage can be conveniently combined with the digital baseband circuit to achieve high-speed information transmission.

[0032] (4) The diodes used in the present invention include PIN diodes, Schottky diodes or high electron mobility transistors, which can achieve rapid switching on and off through voltage, complete high-speed terahertz phase shift, and obtain high-speed terahertz wireless communication and phased array scanning.

[0033] (5) The processing technology of the present invention is mature and can be realized by vapor deposition, laser etching, and fine processing means. The use method is not complicated and has good application potential and prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 It is the overall structure of the present invention;

[0036] Figure 2 Schematic diagram of the waveguide-microstrip line transition structure of a large-area substrate according to an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of a reflective terahertz phase shifting structure according to an embodiment of the present invention;

[0038] Figure 4 Schematic diagram of a transmission-type terahertz phase-shifting structure according to an embodiment of the present invention;

[0039] Figure 5 is a phase curve of an embodiment of the present invention;

[0040] Figure 6 This is the S21 curve of an embodiment of the present invention.

[0041] Reference numerals: A, waveguide-microstrip line transition structure of large-area substrate; B, reflective terahertz phase shift structure; C, transmission terahertz phase shift structure; D, microstrip line-waveguide transition structure of large-area substrate;

[0042] A1, height-reducing waveguide; A2, L-shaped metal probe; A3, matching recessed cavity; B1, 3dB directional coupler; B2, phase-shifting metal strip; B3, diode; B4, matching metal strip; B5, high- and low-resistance feeding structure; B6, high- and low-resistance grounding structure; C1, front-end metal branch; C2, diode; C3, rear-end metal branch; C4, matching microstrip line between branches; C5 common feeding structure. DETAILED DESCRIPTION

[0043] The present invention is further described with reference to the accompanying drawings, which are based on a multi-bit terahertz phase shifter combined with a reflection-transmission phase shifting method. The present invention is further described in detail with reference to embodiments.

[0044] Example:

[0045] Figure 1 The multi-bit terahertz phase shifter based on the reflection-transmission combined phase shifting method proposed in an embodiment of the present invention has an input waveguide connected to a waveguide-microstrip line transition structure A on a large-area substrate to achieve efficient conversion of the waveguide mode of the terahertz wave into a microstrip mode. The waveguide-microstrip line transition structure A is sequentially connected to a reflective terahertz phase shift structure B and a transmission terahertz phase shift structure C to achieve dynamic multi-phase shifting of the terahertz wave. Finally, the microstrip line-waveguide transition structure D on the large-area substrate is connected to the output waveguide to output the phase-shifted terahertz wave.

[0046] The waveguide-microstrip line transition structure A of the large-area substrate is symmetrical to the microstrip line-waveguide transition structure D of the large-area substrate. Figure 2 As shown, in the waveguide-microstrip line transition structure of the large-area substrate, the L-shaped metal probe A2 is located on the large-area substrate and embedded in the end of the height-reducing waveguide A1, so that the terahertz wave is converted from the waveguide mode to the microstrip mode; the matching recessed cavity A3 is a recess in the cavity, the depth of the recess is tangent to the large-area substrate, and the edge of the recess is tangent to the L-shaped metal probe, which can confine the terahertz wave on the L-shaped metal probe; the L-shaped metal probe is combined with the matching recessed cavity to prevent energy leakage when the terahertz wave transitions to the microstrip line on the large-area substrate, thereby ensuring input matching of the terahertz wave.

[0047] like Figure 3As shown in Figure 1, in the reflective terahertz phase-shifting structure B, the circuit structures of the two reflective ports of the 3dB directional coupler B1 are symmetrical. A phase-shift-increasing metal strip B2 is located between the 3dB directional coupler B1 and the diode B3, and is connected in parallel with the diode to increase the phase shift. Diode B3 connects the 3dB directional coupler B1 and the matching metal strip B4. The on-off switching of the diode causes a significant change in the reflected impedance, resulting in a phase shift of the reflected wave. The matching metal strip B4 optimizes the phase shift and insertion loss, ensuring low insertion loss and high phase shift. The high-low resistance feeding structure B5, consisting of a thin high-impedance metal strip and a large low-impedance metal block, connects to the matching metal strip B4 to feed the control voltage. The high-low resistance grounding structure B6, consisting of a thin high-impedance metal strip and a large low-impedance metal block, connects the 3dB directional coupler B1 and the cavity, providing a reference zero level for the entire device.

[0048] like Figure 4 As shown, in the transmission-type terahertz phase-shifting structure C, the front metal branch C1 and the rear metal branch C3 together constitute an open metal branch, which plays a role in adjusting the branch impedance, thereby affecting the phase shift of the metal branch; the diode C2 connects the front metal branch C1 and the rear metal branch C3, and controls the connection and disconnection of the metal branch by changing the on-off state to achieve a small phase shift; the inter-branch matching microstrip line C4 connects multiple metal branches, so that the multiple metal branches are matched with each other, achieving linear superposition of phase shifts while maintaining low insertion loss; the common feeding structure C5 is connected to the two metal branches at the same time, which can feed the diodes of the two metal branches to obtain a phase shift of 45°.

[0049] The L-shaped metal probe, the reflective terahertz phase-shifting structure, and the transmission terahertz phase-shifting structure used in this embodiment are located on a large-area substrate, and the material of the substrate is quartz.

[0050] The E-plane width of the height-reducing waveguide in this embodiment changes from 5.46 mm to 3.26 mm; the L-shaped metal probe consists of two mutually perpendicular metal wires with dimensions of 269 μm × 19 μm and 200 μm × 19 μm, respectively; the matching recessed cavity is 457 μm wide, 536 μm long, and 260 μm deep.

[0051] In this embodiment, the size of the phase-shifting metal strip is 165 μm×13 μm; the size of the matching metal strip is 42 μm×37 μm.

[0052] In this embodiment, the size of the front-end metal branch is 115 μm×116 μm, and the size of the back-end metal branch is 100 μm×92 μm.

[0053] The size of the matching microstrip line between the branches in this embodiment is 16 μm×111 μm; the common feeding structure connects two metal branches, which can achieve a phase shift of 45° step.

[0054] The diode used in this embodiment is a Schottky diode.

[0055] The metal material used in this embodiment is Au.

[0056] In this embodiment, a terahertz wave is input through an input waveguide, passes through a waveguide-to-microstrip transition structure on a large-area substrate, and then propagates to a microstrip line, where it first reaches a reflective terahertz phase-shifting structure. In this reflective terahertz phase-shifting structure, a high- and low-resistance feed structure is used to control the on / off switching of a voltage-controlled diode, ultimately achieving a 0 to 180° phase shift of the terahertz wave.

[0057] After passing through the reflective terahertz phase-shifting structure, the terahertz wave reaches the transmission terahertz phase-shifting structure. A common feed structure controls the on / off of diodes on multiple open metal branches, achieving a phase shift in 45-degree steps. The wave is ultimately output to the output waveguide through the microstrip-to-waveguide transition structure on the large-area substrate.

[0058] The two phase-shifting structures are combined through matching microstrips, and by encoding the voltage, they can be superimposed on each other to achieve 360° multi-bit terahertz phase control. Figure 5 、 Figure 6 As shown, this embodiment uses digital coding to represent the input voltage of the feeding structure. The number "1" indicates an input voltage of 1V, at which point the diode is on, and the number "0" indicates an input voltage of -1V, at which point the diode is off. We can obtain a total of eight states: "0,000," "0,001," "0,011," "0,111," "1,001," "1,011," and "1,111." The first digit of "0,000" represents the voltage of the feeding structure in the reflective terahertz phase-shifting structure, and the last three digits represent the voltages of the three common feeding structures in the transmissive terahertz phase-shifting structure. Figure 5 This is the phase curve of this embodiment. In 8 states, it can achieve a 315° phase shift at 220 GHz. Since 315°+45°=360°, this embodiment achieves a 3-bit terahertz 360° phase shift with a step of 45° in the 215 GHz-225 GHz frequency band, which has a highly linear phase shift. Figure 6 This is the S21 curve of this embodiment, that is, the insertion loss. At 220 GHz, the insertion loss of the eight states of the present invention is less than 10 dB.

[0059] The results show that the multi-bit terahertz phase shifter based on the reflection-transmission combined phase shifting method of the present invention can achieve a 3-bit terahertz 360° phase shift with high linearity and low insertion loss, which will provide a strong foundation for the realization of terahertz application systems.

[0060] Application Examples

[0061] In order to prove the creativity and technical value of the technical solution of the present invention, this section provides application examples of the claimed technical solution on specific products or related technologies.

[0062] The multi-bit terahertz phase shifter, based on a combined reflection-transmission and phase-shifting method, can achieve 360° multi-bit terahertz phase shifting in small increments under the control of a digitally encoded voltage, with highly linear phase shift. Combining a phased circuit with a phased scanning algorithm, the present invention forms a phased array. A voltage-controlled gain amplifier at the front end enables high-precision phased array beam scanning. The reflected terahertz wave from the target is then received and analyzed using a sum-and-difference network to achieve radar scanning positioning and imaging.

[0063] The above embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary persons in the art should fall within the scope of protection of the present invention. The technical contents for which protection is sought in the present invention are all recorded in the claims.

Claims

1. A multi-bit terahertz phase shifter based on a reflection-transmission combined with phase shifting method, characterized in that: Including input waveguide, waveguide-microstrip line transition structure on large-area substrate, reflective terahertz phase shift structure, transmission terahertz phase shift structure, microstrip line-waveguide transition structure on large-area substrate, and output waveguide; The waveguide-microstrip line transition structure of the large-area substrate is symmetrical to the microstrip line-waveguide transition structure of the large-area substrate; the waveguide-microstrip line transition structure of the large-area substrate includes a height-reduced waveguide, an L-shaped metal probe, and a matching recessed cavity, wherein the height-reduced waveguide plays a transition role from a standard waveguide to a waveguide of a custom size; the L-shaped metal probe is located on the large-area substrate and is embedded in the end of the height-reduced waveguide, so that the terahertz wave is converted from a waveguide mode to a microstrip mode; the matching recessed cavity is a depression in the cavity, the depth of the depression is tangent to the large-area substrate, and the edge of the depression is tangent to the L-shaped metal probe; the L-shaped metal probe is combined with the matching recessed cavity; the size and shape of the height-reduced waveguide, the L-shaped metal probe, and the matching recessed cavity in the waveguide-microstrip line transition structure of the large-area substrate are adjustable to achieve a high-efficiency terahertz wave transition from a waveguide to a microstrip line; The reflective terahertz phase shift structure includes a 3dB directional coupler, a phase-shifting metal strip, a diode, a matching metal strip, a high-low resistance feeding structure, and a high-low resistance grounding structure; the 3dB directional coupler divides a terahertz wave into two terahertz waves with a phase difference of 90°, which arrive at two diodes respectively; the phase-shifting metal strip is between the 3dB directional coupler and the diode, and is connected in parallel with the diode to increase the phase shift; the diode connects the 3dB directional coupler and the matching metal strip, and the on-off of the diode can cause a huge change in the reflection impedance, thereby obtaining the phase shift of the reflected wave; the matching metal strip optimizes the phase shift and insertion loss, ensuring low insertion loss and high phase shift; The high-low-resistance feeding structure is composed of a thin high-impedance metal strip and a large low-impedance metal block, and is connected to a matching metal strip to feed a control voltage; the high-low-resistance grounding structure is composed of a thin high-impedance metal strip and a large low-impedance metal block, and is connected to a 3dB directional coupler and a cavity to provide a reference zero level for the entire device; The transmission-type terahertz phase-shifting structure comprises a front-end metal branch, a diode, a rear-end metal branch, a matching microstrip line between branches, and a common feeding structure; the front-end metal branch and the rear-end metal branch together constitute an open metal branch, which plays a role in adjusting the branch impedance; The diode connects the front metal branch and the back metal branch; the inter-branch matching microstrip line matches the multiple metal branches, so that the phase shifts of the multiple metal branches are linearly superimposed while maintaining low insertion loss; the common feeding structure feeds the diodes on the multiple metal branches at the same time, reducing the feeding complexity and obtaining the target phase shift degree.

2. A multi-bit terahertz phase shifter based on a reflection-transmission combined with phase shifting method as claimed in claim 1, characterized in that: The input waveguide is connected to the waveguide-microstrip line transition structure of the large-area substrate to input the terahertz wave; the microstrip line-waveguide transition structure of the large-area substrate is connected to the output waveguide to output the phase-shifted terahertz wave.

3. A multi-bit terahertz phase shifter based on a reflection-transmission combined phase shifting method as claimed in claim 1, characterized in that: The size and shape of the phase-shifting metal strip and the matching metal strip in the reflective terahertz phase-shifting structure are adjustable, so as to change the phase shift of the terahertz wave and the corresponding insertion loss, and obtain a phase shift of 0-180° under low insertion loss.

4. The multi-bit terahertz phase shifter based on the reflection-transmission combined with phase shifting method as claimed in claim 1, characterized in that: The diodes used in the reflective terahertz phase-shifting structure and the transmission terahertz phase-shifting structure are PIN diodes, Schottky diodes or high electron mobility transistors.

5. The multi-bit terahertz phase shifter based on the reflection-transmission combined with phase shifting method as claimed in claim 1, characterized in that: The size and shape of the front metal branches and the rear metal branches in the transmission-type terahertz phase-shifting structure are adjustable to obtain the required small-degree phase shift step, and the matching microstrip line and common feeding structure between the branches can be adjusted according to the required phase shift and insertion loss requirements.

6. The multi-bit terahertz phase shifter based on the reflection-transmission combined with phase shifting method as claimed in claim 1, characterized in that: The material of the large-area substrate is sapphire, quartz, silicon, gallium arsenide or silicon carbide.

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