A novel traveling wave switch modulator

Abstract

The present application relates to direct modulation and sub-terahertz-terahertz communication technology field, especially to a kind of novel traveling wave switch modulator, including input end and output end waveguide, main transmission line of sub-terahertz signal transmission, intermediate frequency feed circuit, two resonant coupling traveling wave switch unit.Schottky diode is combined with microstrip line, to form a kind of double-resonant dynamic coupling unit, coupling unit uses Z-shaped matching structure, utilize intermediate frequency voltage signal to control the electron transport of diode, change the coupling strength on traveling wave switch, so as to realize the amplitude modulation of sub-terahertz wave.In the realization of high-speed amplitude modulation, the insertion loss is low, the on-off ratio is large, and the working performance is good;And the present application is simple in structure, in the case of using only two dynamic structure units, 25.4dB on-off ratio is obtained at zero phase difference point.By adjusting control voltage, high-speed modulation can be realized, and the phase difference is only 3.66 degrees in the whole control voltage conversion process, with higher modulation bandwidth.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of direct modulation and sub-terahertz-terahertz communication technology, and in particular to a novel traveling wave switch modulator. BACKGROUND

[0002] High-speed direct modulation devices are of great significance to the development of high-bandwidth, miniaturization and low-complexity high-speed communication systems. However, as the carrier frequency increases, in the sub-terahertz and above frequency bands, high-performance direct modulation devices face the problems of high insertion loss and low on-off ratio. In the field of sub-terahertz-terahertz communication technology, direct modulation communication systems are of great concern due to their low system complexity and low power consumption. How to develop high-speed, high-integration, high-switching ratio and low-power sub-terahertz-terahertz direct modulation devices has become a research hotspot in recent years.

[0003] As an effective low-frequency high-speed switch, the traveling wave switch has the potential of chip and high-speed modulation. The traveling wave switch is a direct modulator composed of multiple switching units. The common form of the switching unit is a switch parallel to the ground on the main transmission line. When all the switches are off, the switches are equivalent to parallel capacitors, and the short main transmission line is equivalent to a series inductor. Each switching unit is similar to a transmission line equivalent circuit model, so it can provide large transmission bandwidth and low insertion loss. When all units are open, the incident electromagnetic wave is reflected each time it propagates to each single unit to provide a higher on-off ratio. The traditional traveling wave switch modulator uses a uniform material to build the structure, that is, the uniform material is connected in parallel on one side of the transmission line. By uniformly controlling the material, the traveling wave switch modulator is turned on or off. However, due to its structural problems, its modulation speed is limited. As the frequency changes, the parasitic capacitance will affect the signal integrity of the control signal. When the frequency of the control signal is too high, the capacitance cannot respond, and the charging and discharging of the capacitance is not ideal, so the modulator cannot achieve a suitable control voltage. In addition, it is also difficult to match the wideband control signal, so the modulation effect will also deteriorate accordingly. At the same time, the traditional structure does not consider the coupling problem between units, and the matching within the unit lacks basis. This will result in too many units used in the end, and it is difficult for the control signal to be uniformly loaded on the dynamic device, which will ultimately affect the modulation rate. SUMMARY

[0004] (I) Technical problems to be solved

[0005] In view of the deficiencies of the conventional traveling wave switch, the present application aims to provide a direct modulation device operating in the sub-terahertz frequency band, and provides a novel traveling wave switch modulator, which has the characteristics of high rate, high switching ratio of unit and whole, low insertion loss and easy integration, and greatly reduces the number of switching units, so that the consistency of the control signal during the dynamic period is higher. The traveling wave switch modulator adopts a diode and a microstrip matching circuit to form a traveling wave switch coupling unit, adopts an intermediate frequency feeding method to change the electron mobility of the Schottky diode, thereby controlling the opening and closing of the switch, and realizing signal modulation.

[0006] (II) Technical scheme

[0007] In view of the problems and requirements in the background art, the present application proposes a novel traveling wave switch modulator, which includes an input end and an output end waveguide, a main transmission line for transmitting sub-terahertz signals, an intermediate frequency feeding circuit, and two resonant coupling traveling wave switch units.

[0008] The input and output ends of the traveling wave switch modulator both adopt a standard rectangular waveguide WR-7, which is used to input sub-terahertz waves and output modulated signals. The electromagnetic wave mode of the standard rectangular waveguide is TE10 mode, and strong coupling between signals is realized by changing the length of the standard rectangular waveguide and the length of the short-circuit surface. The input end of the traveling wave switch modulator converts the TE10 mode into the TEM mode of the microstrip line, and the output end converts the mode of the microstrip line into the waveguide mode for output.

[0009] The traveling wave switch coupling unit is composed of a Schottky diode and a microstrip line. The ground circuit and the circuit connected to the main transmission line are respectively located on both sides of the diode, wherein the ground circuit provides zero potential, and the circuit connected to the main transmission line provides an intermediate frequency voltage signal. By changing the state of the intermediate frequency feeding part, the voltage across the two diodes can be changed, thereby controlling the on-off of the traveling wave switch, and further realizing the modulation of electromagnetic waves.

[0010] A filter is added before the ground circuit and the intermediate frequency feeding circuit, which serves as the boundary condition of grounding and feeding, and is easy to control the traveling wave switch.

[0011] Further, the substrate of the microstrip line of the traveling wave switch modulator is quartz.

[0012] Further, the traveling wave switch coupling unit adopts a Z-shaped matching structure.

[0013] Further, the two Schottky diodes are gallium arsenide diodes with an anode column diameter of 1 um.

[0014] Further, a second-order CMRC filter is also added before the intermediate frequency feeding circuit

[0015] Further, the base of the intermediate frequency feeding circuit is Rogers 5880.

[0016] The design principle adopted by the application is a design method of a zero-phase amplitude modulator, which considers the phase characteristics in the switching process. A fixed point in the phase change process near the operating frequency, i.e. a point with a phase difference of 0, can obtain a better modulation speed response. The output waveform of the method will not be distorted, supporting high-speed data transmission. Otherwise, the group delay of the output signal is non-zero, which is harmful to high modulation rate response. In the case that the amplitude characteristics are at a reasonable level, the phase difference between the switching states can be minimized to obtain a better group response, thereby ensuring good modulation speed performance. In addition, this response mode based on the frequency point of the input local oscillator signal can be connected in series before and after the diode and then grounded, thereby realizing the characteristics of high switching ratio and low phase difference of the unit, and the expected modulation rate is high.

[0017] According to the characteristics of the traveling wave switch, the traveling wave switch modulator adopts a Schottky barrier diode with an anode column diameter of 1um. The new traveling wave switch modulator is suitable for sub-terahertz high-speed direct modulation, has excellent circuit characteristics such as high switching ratio and low insertion loss, and is suitable for high-integration sub-terahertz direct modulation communication systems.

[0018] (Three) beneficial effects

[0019] The beneficial effects of the application are:

[0020] (1) The application combines a Schottky diode with a microstrip line to form a double-resonance dynamic coupling unit. The coupling unit adopts a Z-shaped matching structure, uses an intermediate frequency voltage signal to control the electron transport of the diode, changes the coupling strength on the traveling wave switch, and thereby realizes amplitude modulation of sub-terahertz waves.

[0021] (2) Moreover, the application has a simple structure, and a switching ratio of 25.4dB is obtained at the zero-phase difference point using only two dynamic structure units. At the same time, high-speed modulation can be realized by adjusting the control voltage. During the entire control voltage conversion process, the phase difference is only 3.66 degrees, and the modulation bandwidth is high, which has good application prospects.

[0022] (3) The application has the characteristics of high rate, high switching ratio of the unit and the whole, low insertion loss, and easy integration, and the traveling wave switch greatly reduces the number of switching units, so that the consistency of the control signal during the dynamic period is higher.

[0023] (4) The application uses a diode and a microstrip matching circuit to form a traveling wave switch coupling unit, and uses an intermediate frequency feeding method to change the electron mobility of the Schottky diode, thereby controlling the opening and closing of the switch and realizing signal modulation.

[0024] (5) This invention is applicable to high-speed direct modulation of Asia-Pacific Hertz and has excellent circuit characteristics such as high switching ratio and low insertion loss. It is suitable for highly integrated Asia-Pacific Hertz direct modulation communication systems. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the overall circuit of the novel traveling wave switch modulator;

[0027] Figure 2 This is a schematic diagram of the coupling unit of the novel traveling wave switch modulator;

[0028] Figure 3 The amplitude curves of the switching unit S21 in the on and off states of the novel traveling wave switch modulator are shown. Detailed Implementation

[0029] The present invention provides a novel traveling-wave switch modulator in conjunction with the accompanying drawings. The invention will be further described in detail below with reference to embodiments:

[0030] Example:

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and examples.

[0032] In this traveling wave switch modulator, the local oscillator frequency is input from the right side, and after passing through two mutually coupled modulation units controlled by the intermediate frequency signal, the modulated wave is output to the left side.

[0033] like Figure 1 As shown, the novel traveling-wave switch modulator of this invention comprises two standard rectangular waveguides WR-7 on the left and right, a main transmission line between the two standard rectangular waveguides, two traveling-wave switch coupling units, an intermediate frequency feed, and a matching circuit. The standard rectangular waveguide WR-7 covers the full frequency band of 110-170GHz. In the overall structure of this invention, the rectangular waveguides and microstrip lines that input the Asia-Pacific Hertz signal and output the modulation signal constitute a microstrip probe. The input waveguide microstrip probe needs to convert the waveguide mode to the microstrip mode, and the output waveguide microstrip probe needs to convert the microstrip mode to the waveguide mode.

[0034] like Figure 2As shown in the figure, the core modulation element of each traveling wave switch coupling unit is a small size anode column Schottky diode with a diameter of 1 um. The traveling wave switch modulator coupling unit structure is that one transmission line is directly connected to the filter of the ground structure, so that the diode is grounded as transmission line 1, and the other transmission line directly connects the diode with the main transmission line, which is called transmission line 2. In this configuration, a control voltage can be applied to the main transmission line to generate a potential difference on the Schottky diode, thereby controlling the state of the controller switch. At the same time, the resonance generated by transmission 1 will be transferred to transmission line 2 through the Schottky diode, and the voltage across the Schottky diode can be controlled to change the effect of resonance transmission, thereby realizing signal modulation.

[0035] As shown in Figure 1 and Figure 2 The present application adopts a two-traveling wave switch unit structure, and the on-off ratio of the entire traveling wave switch is multiplied by the on-off ratio of each switch unit, and the total insertion loss is also approximately equal to the insertion loss of each switch unit. For the traveling wave switch unit of the present application, a Z-shaped matching structure is adopted, that is, the main transmission line and transmission line 2, the diode, and transmission line 1 form a Z-shaped structure. Through the design of the Z-shaped structure, a higher unit switch ratio can be achieved, the number of units can be reduced, the modulation rate can be improved, and at the same time, the matching effect between microstrip circuits can be improved by using this structure, the strength of resonance coupling can be increased, and the working effect of the entire traveling wave switch modulator can be improved.

[0036] As shown in Figure 1 In order to load control signals to the traveling wave switch unit, the present application designs an intermediate frequency feed source with a filter, which is equivalent to an open boundary condition at 140 GHz, and does not affect the amplitude of the input sub-terahertz signal. At the same time, due to the introduction of the filter, the overall length of the traveling wave switch modulator is large, and the high-frequency control signal may not be perfectly loaded on the two diodes at the same time. Therefore, before the filter of the intermediate frequency feed, the present application designs a 5880 intermediate frequency matching circuit to prevent a large error in the voltage of the two diodes.

[0037] As shown in Figure 3 The figure is the S21 amplitude curve of the on-state and off-state of the traveling wave switch unit of the traveling wave switch modulator. The traveling wave switch coupling unit composed of microstrip lines and diodes changes the length of the matching transmission line to improve the coupling strength, so that the traveling wave switch modulator has a large on-off ratio.

[0038] The above embodiments are only used to describe the preferred embodiments of the present application, and are not used to limit the design and scope of the present application. Without departing from the design concept of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope of the present application. The technical content of the present application claimed for protection has been entirely recorded in the claims.

Claims

1. A novel traveling wave switch modulator characterized by, The traveling wave switch modulator comprises input and output waveguides, a main transmission line for transmitting sub-terahertz signals, an intermediate frequency feeding circuit, an intermediate frequency feeding matching circuit and two resonant coupling traveling wave switch units. The input and output waveguides are WR-7 standard rectangular waveguides, the last stage of the WR-7 rectangular waveguide is a waveguide short circuit surface, and the WR-7 waveguide is connected with a microstrip line; the electromagnetic wave mode of the standard rectangular waveguide is a TE10 mode, signal coupling is performed by changing the length of the standard waveguide and the length of the short circuit surface, the input waveguide converts the TE10 mode into a TEM mode of the microstrip line, and the output waveguide converts the electromagnetic wave of the TEM mode into an electromagnetic wave of the TE10 mode for output; The resonant coupling traveling wave switch unit comprises a microstrip line, a Schottky diode, a filter, a grounding circuit and a circuit connected with the main transmission line in sequence; The Schottky diode is connected with the grounding circuit and the circuit connected with the main transmission line at both ends, and the voltage difference at both ends of the Schottky diode is changed by an intermediate frequency feeding voltage signal to control the opening and closing of the traveling wave switch; The filter is arranged before the grounding circuit and is used as a boundary condition of the grounding circuit to facilitate the control of the traveling wave switch.

2. A novel traveling wave switch modulator as claimed in claim 1, wherein, The main transmission line for transmitting sub-terahertz signals and the microstrip circuit of the traveling wave switch unit use a quartz substrate.

3. A novel traveling wave switch modulator as claimed in claim 1, wherein, The two Schottky diodes are gallium arsenide diodes with an anode column diameter of 1 um.

4. A novel traveling wave switch modulator as claimed in claim 1, wherein, A second-order CMRC filter is also arranged before the intermediate frequency feeding circuit.

5. A novel traveling wave switch modulator as claimed in claim 1, wherein, The two resonant coupling traveling wave switch units adopt a Z-shaped matching structure.

6. A novel traveling wave switch modulator as claimed in claim 1, wherein, The substrate of the intermediate frequency feeding matching circuit is Rogers 5880.

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