A terahertz vector modulator based on waveguide coupling

Abstract

The present invention provides a terahertz vector modulator based on waveguide coupling, which includes a modulator body in the shape of a "T". The three ends of the "T"-shaped modulator body are respectively a first waveguide coupler, a second waveguide coupler, and a third waveguide coupler. The first waveguide coupler, the second waveguide coupler, and the third waveguide coupler each include two parallel straight metal waveguides, and a plurality of fixed segments are integrally connected between the two straight metal waveguides, and coupling holes are formed between adjacent fixed segments. A combiner is also integrally connected between the second waveguide coupler and the third waveguide coupler, and on-chip modulation chips are respectively provided on the second waveguide coupler and the third waveguide coupler. The present invention has the advantages of both achieving high amplitude and phase modulation accuracy, and having component miniaturization, low cost, and easy integration.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic functional devices, and in particular, to a terahertz vector modulator based on waveguide coupling. Background Art

[0002] Terahertz waves refer to electromagnetic waves with frequencies in the range of 0.1 - 10 THz (wavelengths between 3 mm and 30 μm). Their frequencies are between microwaves and infrared rays. Terahertz waves overlap with millimeter waves in the long wavelength band and with infrared rays in the short wavelength band, and are located in an important region of the transition from macroscopic electronics to micro-optical photonics in the electromagnetic spectrum. Due to their special spectral position and the inherent advantages of high frequency, large bandwidth, and strong penetration ability of terahertz waves, they have become a research hotspot for researchers in various countries and research institutions around the world. As a very important cross-cutting frontier field, the research value and application prospects of terahertz waves are being explored, and terahertz will be widely used in biomedicine, wireless communication, national defense security, etc. in the future.

[0003] The concept of vector modulators was first proposed in the 1980s. So far, various forms of vector modulators have been developed and widely used. The main types include: digital control type, analog type, impedance transformation type, differential amplification type, I / Q type, etc. At the same time, because vector modulators have the advantage of directly realizing signal amplitude and phase modulation, they have currently been widely used in multiple fields such as radio frequency reflection power cancellation systems, digital communication systems, space communication systems, multi-channel transceiver systems, phased array radars, etc.

[0004] Digital communication systems are an important application of vector modulators. In today's digital communication systems that pursue miniaturization, low cost, high data rate, and low bit error rate, traditional intermediate frequency modulation technologies have insurmountable defects. First, the circuit structure is complex, the circuit volume is large, and it is difficult to integrate. The addition of an intermediate frequency synthesizer makes the output filter of the upconverter require both high Q value and good linear phase characteristics; when the intermediate frequency is low, even double conversion is required to meet the requirements of upconversion, further increasing the circuit complexity. Second, the cost is high and the reliability is insufficient. The complex circuit firmware in the transmitter greatly increases the cost, and at the same time, the complex design increases the failure rate and reduces the reliability. Moreover, the modulation rate is limited. The intermediate frequency signal for transmitting information has a low frequency and a narrow bandwidth, which cannot meet the high data rate requirements of modern communication. Finally, due to the non-linear characteristics of devices such as upconverters, non-linear distortion, in-band distortion, and out-of-band spectral spreading will inevitably occur during signal transmission, which will lead to a decline in the quality of the modulated signal. Due to some inevitable problems existing in intermediate frequency modulation technologies, direct modulation technology has become a research hotspot.

[0005] Typical direct modulation methods include binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK). In a phased array radar system, to achieve simultaneous modulation of the amplitude and phase of a signal, a cascaded manner of a phase shifter and an attenuator is usually adopted. However, this modulation method of cascading two devices has two serious problems. One is that phase shifters and attenuators are usually relatively large in size, which is not conducive to the miniaturization and integration of the system. The other is that the modulation accuracy of the cascaded manner of phase shifters and attenuators cannot meet the requirements of modern phased array radars. Summary of the Invention

[0006] Aiming at the deficiencies in the prior art, the present invention provides a terahertz vector modulator based on waveguide coupling, which has the advantages of high modulation accuracy, miniaturization of components, and easy integration.

[0007] The above technical object of the present invention is achieved through the following technical solutions:

[0008] A terahertz vector modulator based on waveguide coupling includes a modulator body in the shape of a "T". The three ends of the "T"-shaped modulator body are respectively a first waveguide coupler, a second waveguide coupler, and a third waveguide coupler. The first waveguide coupler, the second waveguide coupler, and the third waveguide coupler each include two parallel straight metal waveguides. A plurality of fixed segments are integrally connected between the two straight metal waveguides, and coupling holes are formed between adjacent fixed segments. A combiner is also integrally connected between the second waveguide coupler and the third waveguide coupler, and on-chip modulation chips are respectively provided on the second waveguide coupler and the third waveguide coupler.

[0009] The present invention is further configured as: The first waveguide coupler includes four ports, namely a first input end, a first through end, a first coupling end, and a first isolation end. The phases of the terahertz waves at the first through end and the first coupling end differ by 90°.

[0010] The present invention is further configured as: The second waveguide coupler and the third waveguide coupler have the same structure, and both include a second input end, a second through end, a second coupling end, and a second isolation end.

[0011] The present invention is further configured as: The first through end of the first waveguide coupler is connected to the second input end of the second waveguide coupler, and the first coupling end of the first waveguide coupler is connected to the second input end of the third waveguide coupler.

[0012] The present invention is further configured as: The combiner is a T-shaped metal waveguide, including a first combiner input port, a second combiner input port, and a combiner output port. The first combiner input port is connected to the second isolation end of the second waveguide coupler, and the second combiner input port is connected to the second isolation end of the third waveguide coupler.

[0013] The present invention is further configured such that openings are provided on the second through end and the second coupling end of the second waveguide coupler and the third waveguide coupler, and the on-chip modulation chip is inserted into the openings.

[0014] The present invention is further configured such that the on-chip modulation chip includes a substrate, and an E-plane probe, a first metal microstrip line, a second metal microstrip line, a grounding stub, a feeding stub, and a gallium arsenide diode are provided on the substrate;

[0015] One end of the E-plane probe is inserted into the openings on the second through end and the second coupling end, the other end of the E-plane probe is connected to the first metal microstrip line, the other end of the first metal microstrip line is connected to the negative pole of the gallium arsenide diode, the first metal microstrip line is also connected to the grounding stub, the positive pole of the gallium arsenide diode is connected to the second metal microstrip line, and the other end of the second metal microstrip line is connected to the feeding stub.

[0016] The present invention is further configured such that the material of the linear metal waveguide and the T-shaped metal waveguide is any one of copper, aluminum, or gold; the substrate material is any one of quartz, gallium nitride, gallium arsenide, indium phosphide, or silicon carbide.

[0017] The present invention has the advantages of both achieving high amplitude and phase modulation accuracy and having component miniaturization, low cost, and easy integration. Description of the Drawings

[0018] Figure 1 is a three-dimensional structural schematic diagram of this embodiment;

[0019] Figure 2 is a planar schematic diagram of this embodiment;

[0020] Figure 3 is a schematic diagram of the first waveguide coupler in this embodiment;

[0021] Figure 4 is an installation schematic diagram of the second waveguide coupler and the on-chip modulation chip in this embodiment;

[0022] Figure 5 is a structural schematic diagram of the on-chip modulation chip in this embodiment;

[0023] Figure 6 is a schematic diagram of the combiner in this embodiment;

[0024] Figure 7 is a simulation constellation diagram of this embodiment;

[0025] Figure 8 is a phase diagram of the simulation for implementing QPSK modulation in this embodiment;

[0026] Figure 9 The transmission curve graph for realizing QPSK modulation in the simulation of this embodiment.

[0027] In the above-mentioned drawings: 1. First waveguide coupler; 2. Second waveguide coupler; 3. Third waveguide coupler; 4. Combiner; 5. On-chip modulation chip; 6. Coupling hole; 7. First input end; 8. First through end; 9. First coupling end; 10. First isolation end; 11. Second input end; 12. Second through end; 13. Second coupling end; 14. Second isolation end; 15. Substrate; 16. E-plane probe; 17. First metal microstrip line; 18. Ground stub; 19. Gallium arsenide diode; 20. Second metal microstrip line; 21. Feeding stub; 22. First combiner input port; 23. Second combiner input port; 24. Combiner output port. Specific implementation mode

[0028] The technical solutions in the present invention will be further described below in conjunction with the drawings and embodiments.

[0029] A terahertz vector modulator based on waveguide coupling, as Figures 1-6 shown, includes a modulator body in the shape of a "T". The three ends of the "T"-shaped modulator body are respectively a first waveguide coupler 1, a second waveguide coupler 2, and a third waveguide coupler 3. The first waveguide coupler 1, the second waveguide coupler 2, and the third waveguide coupler 3 all include two parallel straight metal waveguides. Five fixed segments are integrally connected between the two straight metal waveguides. Coupling holes 6 are formed between adjacent fixed segments. The sizes of the coupling holes 6 are the same and are symmetrically arranged between the two straight metal waveguides.

[0030] Among them, the first waveguide coupler 1 includes four ports, namely a first input end 7, a first through end 8, a first coupling end 9, and a first isolation end 10. The phases of the terahertz waves at the first through end 8 and the first coupling end 9 differ by 90°. The second waveguide coupler 2 and the third waveguide coupler 3 have the same structure and both include a second input end 11, a second through end 12, a second coupling end 13, and a second isolation end 14. The first through end 8 of the first waveguide coupler 1 is connected to the second input end 11 of the second waveguide coupler 2, and they are integrally connected by an arc-shaped metal waveguide; the first coupling end 9 of the first waveguide coupler 1 is connected to the second input end 11 of the third waveguide coupler 3, and they are also integrally connected by an arc-shaped metal waveguide. Among them, the first input end 7 of the first waveguide coupler 1 inputs a terahertz wave signal, and the first isolation end 10 of the first waveguide coupler 1 is used to connect an external matching load.

[0031] A combiner 4 is also integrally connected between the second waveguide coupler 2 and the third waveguide coupler 3. The combiner 4 is a T-shaped metal waveguide, including a first combiner input port 22, a second combiner input port 23, and a combiner output port 24. The first combiner input port 22 is integrally connected to the second isolation end 14 of the second waveguide coupler 2, and the second combiner input port 23 is integrally connected to the second isolation end 14 of the third waveguide coupler 3. The combiner 4 vectorially combines two modulated terahertz wave signals into one signal for output.

[0032] The materials of the linear metal waveguide and the T-shaped metal waveguide are any one of copper, aluminum, or gold, and gold is preferably used in this embodiment.

[0033] Openings are provided on the second through end 12 and the second coupling end 13 of the second waveguide coupler 2 and the third waveguide coupler 3, and an on-chip modulation chip 5 is inserted into the openings. The on-chip modulation chip 5 includes a substrate 15, and the material of the substrate 15 is any one of quartz, gallium nitride, gallium arsenide, indium phosphide, or silicon carbide, and quartz is preferably used in this embodiment. An E-plane probe 16, a first metal microstrip line 17, a second metal microstrip line 20, a grounding stub 18, a feeding stub 21, and a gallium arsenide diode 19 are provided on the substrate 15. One end of the E-plane probe 16 is inserted into the openings on the second through end 12 and the second coupling end 13, the other end of the E-plane probe 16 is connected to the first metal microstrip line 17, and the other end of the first metal microstrip line 17 is connected to the negative electrode of the gallium arsenide diode 19. The first metal microstrip line 17 is also connected to the grounding stub 18, the positive electrode of the gallium arsenide diode 19 is connected to the second metal microstrip line 20, and the other end of the second metal microstrip line 20 is connected to the feeding stub 21.

[0034] After simulating the terahertz vector modulator based on waveguide coupling in this embodiment, it is found that it has good effects. In this embodiment, by using the equivalent resistance change of 0.1 - 2000 ohms in the connected state, disconnected state, and intermediate state of the gallium arsenide diode 19, and at the same time adopting the simulation method of independent control of I / Q two terahertz wave signals, as Figure 7 shown, it represents the constellation diagram of S21 at a frequency point of 220 GHz. Each point in the figure represents the amplitude and phase of the terahertz wave signal of S21 under different impedances of the diode. The results show that it can achieve continuous phase modulation of 0 - 360° and at the same time perform amplitude modulation better than -40 dB. As Figure 8 compared with Figure 9As shown, based on waveguide coupling, the terahertz vector modulator can achieve QPSK modulation under the condition of the equivalent resistance value change of 0.1 - 2000 ohms in the connected state and the disconnected state of its gallium arsenide diode 19, and by using the independent control method of two I / Q terahertz wave signals simultaneously under simulation conditions. The simulation results in the figure show that at the frequency point of 220 GHz, QPSK modulation with a phase error of ±3° and an amplitude error of ±0.6 dB can be achieved, and the bandwidth above -10 dB can reach more than 16 GHz. This shows that the terahertz vector modulator based on waveguide coupling of the present invention has the characteristics of high precision, low insertion loss, continuous phase and amplitude regulation, so it can be widely used in terahertz wireless communication systems and terahertz phased array radar systems.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A terahertz vector modulator based on waveguide coupling, characterized in that: It includes a modulator body in the shape of a "T", and the three ends of the "T"-shaped modulator body are respectively a first waveguide coupler (1), a second waveguide coupler (2), and a third waveguide coupler (3); the first waveguide coupler (1), the second waveguide coupler (2), and the third waveguide coupler (3) all include two parallel straight metal waveguides, and several fixed segments are integrally connected between the two straight metal waveguides, and coupling holes (6) are formed between adjacent fixed segments; a combiner (4) is also integrally connected between the second waveguide coupler (2) and the third waveguide coupler (3), and on-chip modulation chips (5) are respectively provided on the second waveguide coupler (2) and the third waveguide coupler (3); the second waveguide coupler (2) and the third waveguide coupler (3) have the same structure, and both include a second input end (11), a second through end (12), a second coupling end (13), and a second isolation end (14); openings are provided on the second through end (12) and the second coupling end (13) of the second waveguide coupler (2) and the third waveguide coupler (3), and the on-chip modulation chip (5) is inserted into the openings.

2. The terahertz vector modulator based on waveguide coupling according to claim 1, characterized in that: The first waveguide coupler (1) includes four ports, namely a first input end (7), a first through end (8), a first coupling end (9), and a first isolation end (10), and the terahertz waves of the first through end (8) and the first coupling end (9) have a phase difference of 90°.

3. The terahertz vector modulator based on waveguide coupling according to claim 2, characterized in that: The first through end (8) of the first waveguide coupler (1) is connected to the second input end (11) of the second waveguide coupler (2), and the first coupling end (9) of the first waveguide coupler (1) is connected to the second input end (11) of the third waveguide coupler (3).

4. The terahertz vector modulator based on waveguide coupling according to claim 3, characterized in that: The combiner (4) is a T-shaped metal waveguide, including a first combiner input port (22), a second combiner input port (23), and a combiner output port (24); the first combiner input port (22) is connected to the second isolation end (14) of the second waveguide coupler (2), and the second combiner input port (23) is connected to the second isolation end (14) of the third waveguide coupler (3).

5. The terahertz vector modulator based on waveguide coupling according to claim 4, characterized in that: The on-chip modulation chip (5) includes a substrate (15), and an E-plane probe (16), a first metal microstrip line (17), a second metal microstrip line (20), a grounding stub (18), a feeding stub (21), and a gallium arsenide diode (19) are provided on the substrate (15); One end of the E-plane probe (16) is inserted into the openings on the second through end (12) and the second coupling end (13), the other end of the E-plane probe (16) is connected to the first metal microstrip line (17), the other end of the first metal microstrip line (17) is connected to the negative pole of the gallium arsenide diode (19), the first metal microstrip line (17) is also connected to the grounding stub (18), the positive pole of the gallium arsenide diode (19) is connected to the second metal microstrip line (20), and the other end of the second metal microstrip line (20) is connected to the feeding stub (21).

6. The terahertz vector modulator based on waveguide coupling according to claim 5, characterized in that: The materials of the linear metal waveguide and the T-shaped metal waveguide are any one of copper, aluminum or gold; the material of the substrate (15) is any one of quartz, gallium nitride, gallium arsenide, indium phosphide or silicon carbide.

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