Space-time modulation-based coupled terahertz on-chip circulator and implementation method thereof
Technical Field
The invention relates to the technical field of millimeter wave communication, in particular to a coupling terahertz on-chip circulator based on space-time modulation and an implementation method thereof.
Background
With the vigorous development of mobile communication technology, the concept of communication perception integration is gradually rising, and compared with communication, perception needs to send and receive data simultaneously and continuously to meet the perception requirement of high quality. In the existing communication system, the time division duplex technology is mainly adopted, and simultaneous transceiving cannot be achieved. The minority frequency division duplex system can realize simultaneous uplink and downlink, but is only used in a low frequency band and needs independent uplink and downlink frequency bands at present, so that the spectrum utilization rate is low, and resources and specific frequency characteristics of the high frequency band cannot be utilized. Therefore, in order to realize synchronous uplink and downlink reception and transmission, the requirement of sense fusion is better realized, and research and development of in-band full duplex technology are urgent.
Circulators are an important primary way to achieve in-band full duplex. In the microwave band, the circulator is typically implemented by ferrite. The traditional ferrite circulator is large in size, and magnetic materials such as ferrite are difficult to be compatible with the existing integrated circuit processing technology due to material limitation. Therefore, research into on-chip nonmagnetic circulators is of paramount importance. In recent years, scientific research groups at home and abroad successfully adopt a space-time modulation technology to realize the nonreciprocal effect without external magnetic bias. The general non-reciprocal implementation method based on space-time modulation comprises the following steps: a series of constant-amplitude time-varying signals with initial phase gradient change are applied to a certain medium or device, the frequency and the amplitude of the signals are adjusted to achieve the effect similar to ferrite, the symmetry of time inversion is broken, and the function of the circulator is realized. The existing circulator based on space-time modulation is generally concentrated in an L-band and an S-band, and the space-time modulation circulator of millimeter wave and terahertz frequency bands has not been reported yet. In 2014, nicholas et al disclosed a circulator based on space-time modulation, with an operating frequency of about 170MHz, and constructed a maskless upper circulator using lumped elements. With the increase of frequency, the size of the device is smaller and smaller, the lumped element cannot meet the design requirement, and in order to adapt to the development of future general sense integration, a terahertz on-chip circulator of a full microstrip circuit is needed.
Disclosure of Invention
The invention aims to provide a space-time modulation-based coupled terahertz on-chip circulator and an implementation method thereof, aiming at the defects of the prior art.
The invention aims at realizing the following technical scheme:
a coupling terahertz on-chip circulator based on space-time modulation comprises a medium substrate, a microstrip transmission line, a microstrip coupling line, a microstrip sector filter, a varactor, a terahertz signal input/output port, a modulation signal input port, a grounding port and a cross microstrip transmission line; the center of the top of the medium substrate is a connection point of a microstrip transmission line and is connected with the microstrip transmission line in a cross shape; the microstrip coupling line is connected with a terahertz signal input/output port; the varactor diode pair is arranged along a straight line, anodes are opposite, and the middle of the varactor diode pair is connected with the microstrip sector filter and the modulation signal input port; the microstrip sector filter is connected with a grounding port.
Further, the microstrip coupling lines are 3 groups, namely a first microstrip coupling line, a second microstrip coupling line and a third microstrip coupling line.
Further, the microstrip sector filters are 7 groups, namely a first microstrip sector filter, a second microstrip sector filter, a third microstrip sector filter, a fourth microstrip sector filter, a fifth microstrip sector filter, a sixth microstrip sector filter and a seventh microstrip sector filter.
Further, the varactors comprise two varactors forming a varactor pair, 3 groups are respectively a first varactor pair, a second varactor pair and a third varactor pair.
Further, the total of 3 groups of terahertz signal input/output ports are respectively a first terahertz signal input/output port, a second terahertz signal input/output port and a third terahertz signal input/output port.
Further, the total of 3 groups of modulation signal input ports are respectively a first modulation signal input port, a second modulation signal input port and a third modulation signal input port.
Further, the total of the grounding ports is 4 groups, namely a first grounding port, a second grounding port, a third grounding port and a fourth grounding port.
Further, the left, right and upper directions of the cross microstrip transmission line connection are connected with three circulator substructures, and the three circulator substructures are congruent in structure.
Further, the lower direction of the cross microstrip transmission line connection is connected with a seventh microstrip sector filter, and then is grounded through a fourth grounding port.
The invention also provides a realization method of the coupling terahertz on-chip circulator based on space-time modulation, which is to load three paths of sine modulation signals and reverse bias voltage on a first modulation signal input port, a second modulation signal input port and a third modulation signal input port, and break the time inversion symmetry of the system through the actions of a first varactor pair, a second varactor pair and a third varactor pair, thereby realizing the nonreciprocal effect.
The invention has the following advantages:
according to the invention, three paths of sine modulation signals with the same amplitude and 120 DEG initial phase difference and the same reverse direct current bias are loaded on a first modulation signal input port, a second modulation signal input port and a third modulation signal input port, and the time inversion symmetry of the system is broken through the actions of a first varactor diode pair, a second varactor diode pair and a third varactor diode pair, so that a coupling terahertz on-chip circulator based on space-time modulation is realized. In addition, the invention does not need to add magnetic bias or magnetic materials, has small structure, convenient processing and high isolation, works in the millimeter wave terahertz frequency band, and is convenient to integrate with other on-chip terahertz communication systems.
Drawings
Fig. 1 is a schematic structural diagram of a coupling terahertz on-chip circulator based on space-time modulation.
Fig. 2 is a simulation graph of return loss, insertion loss and isolation degree using a first terahertz signal input/output port as an input port, a second terahertz signal input/output port as a transmission port, and a third terahertz signal input/output port as an isolation port according to an embodiment.
Fig. 3 is a simulation graph of return loss, insertion loss and isolation of the second terahertz signal input/output port as an input port, the third terahertz signal input/output port as a transmission port, and the first terahertz signal input/output port as an isolation port according to an embodiment.
Fig. 4 is a simulation graph of return loss, insertion loss and isolation of the third terahertz signal input/output port, the first terahertz signal input/output port, and the second terahertz signal input/output port.
The marks in the figure: 1. a first terahertz signal input/output port; 2. a second terahertz signal input/output port; 3. a third terahertz signal input/output port; 4. a first modulated signal input port; 5. a second modulated signal input port; 6. a third modulated signal input port; 7. a first ground port; 8. a second ground port; 9. a third ground port; 10. a first microstrip coupling line; 11. a second microstrip coupling line; 12. a third microstrip coupling line; 13. a first varactor pair; 14. a second varactor pair; 15. a third varactor pair; 16. a first microstrip sector filter; 17. a second microstrip sector filter; 18. a third microstrip sector filter; 19. a fourth microstrip sector filter; 20. a fifth microstrip sector filter; 21. a sixth microstrip sector filter; 22. a seventh microstrip sector filter; 23. a fourth ground port; 24. the cross microstrip transmission lines are connected.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings and examples.
As shown in fig. 1, the coupling terahertz on-chip circulator based on space-time modulation provided in this embodiment includes a dielectric substrate, a microstrip transmission line, a microstrip coupling line, a microstrip sector filter, a varactor, a terahertz signal input/output port, a modulation signal input port, a ground port, and a cross microstrip transmission line connection; the center of the top of the medium substrate is a connection point of a microstrip transmission line and is connected with the microstrip transmission line in a cross shape; the microstrip coupling line is connected with a terahertz signal input/output port; the varactor diode pair is arranged along a straight line, anodes are opposite, and the middle of the varactor diode pair is connected with the microstrip sector filter and the modulation signal input port; the microstrip fan-shaped filter is connected with a grounding port 。 The microstrip coupling lines are three groups, namely a first microstrip coupling line 10,A second microstrip coupling line 11, a third microstrip coupling line 12; the microstrip sector filters are 7 groups, namely a first microstrip sector filter 16, a second microstrip sector filter 17, a third microstrip sector filter 18, a fourth microstrip sector filter 19, a fifth microstrip sector filter 20, a sixth microstrip sector filter 21 and a seventh microstrip sector filter 22; the varactors comprise two varactors forming a varactor pair, 3 groups are respectively a first varactor pair 13, a second varactor pair 14 and a third varactor pair 15; the terahertz signal input and output ports are 3 groups, namely a first terahertz signal input and output port 1, a second terahertz signal input and output port 2 and a third terahertz signal input and output port 3; the modulated signal input ports are 3 groups, namely a first modulated signal input port 4, a second modulated signal input port 5 and a third modulated signal input port 6; the total of the grounding ports is 4 groups, namely a first grounding port 7, a second grounding port 8, a third grounding port 9 and a fourth grounding port 23.
The three directions of the left, right and upper directions of the cross microstrip transmission line connection 24 are connected with three circulator substructures, and the three substructures are congruent in structure.
The cross microstrip transmission line connection 24 is connected to the seventh microstrip sector filter 22 in the lower direction and then grounded through the fourth grounding port 23.
The dielectric substrate is a quartz substrate with the thickness of 50 mu m, the microstrip metal structure on the substrate is composed of gold with the thickness of 2 mu m, the varactor diode is a single-tube flip-chip GaAs diode with the tube core diameter of 1 mu m, and the impedance of each terahertz signal input/output port, the impedance of each terahertz signal modulation signal input/output port and the impedance of each terahertz signal ground port are all adjusted to 50 omega.
The implementation method of the coupled terahertz on-chip circulator based on space-time modulation provided by the embodiment comprises the following steps: the time reversal symmetry of the system is broken through by loading three paths of sine modulation signals with the amplitude of 1.3V, the initial phase difference of 120 degrees and the frequency of 14GHz and reverse bias voltage of 2.6V on the first modulation signal input port 4, the second modulation signal input port 5 and the third modulation signal input port 6 and the action of the first varactor pair 13, the second varactor pair 14 and the third varactor pair 15, so that the nonreciprocal effect is realized.
When the circulator is deployed by taking the first terahertz signal input/output port 1 as an input port, the second terahertz signal input/output port 2 as a transmission port and the third terahertz signal input/output port 3 as an isolation port, the return loss, insertion loss and isolation simulation curves of the circulator are shown in fig. 2. When the working frequency is 140GHz, the return loss is 15.32dB, the insertion loss is 8.04dB, and the isolation degree is 22.02dB.
When the circulator is deployed by taking the second terahertz signal input/output port 2 as an input port, the third terahertz signal input/output port 3 as a transmission port and the first terahertz signal input/output port 1 as an isolation port, the return loss, insertion loss and isolation simulation curves of the circulator are shown in fig. 3. When the working frequency is 140GHz, the return loss is 13.84dB, the insertion loss is 8.87dB, and the isolation degree is 18.81dB.
When the circulator is deployed by taking the third terahertz signal input/output port 3 as an input port, the first terahertz signal input/output port 1 as a transmission port and the second terahertz signal input/output port 2 as an isolation port, the return loss, insertion loss and isolation simulation curves of the circulator are shown in fig. 4. When the working frequency is 140GHz, the return loss is 12.3dB, the insertion loss is 8.99dB, and the isolation degree is 21.48dB.
In addition, the invention does not need to add magnetic bias or magnetic materials, has small structure, convenient processing and high isolation, works in the millimeter wave terahertz frequency band, and is convenient to integrate with other on-chip terahertz communication systems.
The foregoing is merely a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification and substitution based on the technical scheme and the inventive concept provided by the present invention should be covered in the scope of the present invention.