Terahertz continuous waveguide duplexer based on complementary filter

Abstract

The invention belongs to the field of terahertz waveguide devices, and particularly provides a terahertz continuous waveguide duplexer based on a complementary filter, which is used for solving the problem that a multi-branch coupling type multiplexer in the prior art cannot avoid frequency gaps between channels in a terahertz frequency band. The filter comprises a common end rectangular waveguide 1, a waveguide T-shaped joint 2, an inductive diaphragm waveguide band-pass filter 3 and a capacitive diaphragm waveguide band-pass filter 4, the complementary filter theory is applied for the first time, and the capacitive diaphragm waveguide band-pass filter is creatively introduced on the basis of a traditional multi-branch coupling type structure. The impedance imaginary part of the capacitive diaphragm waveguide band-pass filter is negative, the impedance imaginary part of the inductive diaphragm waveguide band-pass filter is positive, the capacitive diaphragm waveguide band-pass filter and the inductive diaphragm waveguide band-pass filter are connected in parallel through the waveguide T-shaped joint to form a complementary filter, and finally the duplexer is well matched in the working bandwidth. A multi-branch coupling type structure is used in a terahertz frequency band for the first time to realize the design of a waveguide continuous duplexer without frequency gaps.

Description

Technical Field

[0001] The invention belongs to the field of terahertz waveguide devices, and specifically provides a terahertz continuous waveguide duplexer based on a complementary filter. Background Art

[0002] Terahertz waves usually refer to electromagnetic waves with a frequency range of 0.1THz~10THz and a wavelength of 0.03mm~3mm. In the electromagnetic spectrum, terahertz waves occupy a special position between electronics and photonics. As early as the 1920s, scientists had great research interest in terahertz waves; however, limited by the research methods and technical conditions at the time, the development of terahertz waves was mainly limited to the fields of high-resolution spectroscopy and space remote sensing; with the continuous advancement of science and technology, terahertz technology has made great progress, and many emerging disciplines and application fields have emerged, making terahertz technology a research hotspot in the international academic and industrial circles.

[0003] In the field of wireless communications, terahertz waves can theoretically support high-speed data transmission from tens of Gbit / s to several Tbit / s, which is much higher than wireless communications in the microwave and millimeter wave bands. Given the many advantages of terahertz waves in the field of communications, terahertz heterodyne receivers have been widely used. Increasing the instantaneous bandwidth can improve the sensitivity of the receiver's continuous observation and enable the receiver to receive multiple channels simultaneously without changing the local oscillator frequency. However, due to the bandwidth limitations of the mixer and low-noise amplifier, the instantaneous bandwidth of current receivers is still very limited.

[0004] In order to improve the instantaneous bandwidth of the receiver, a relatively simple method is to use a multiplexer to divide the terahertz frequency band of interest into smaller frequency bands, and then inject them into different mixers for down-conversion; a multiplexer contains multiple channels with filtering functions, among which a device with two channels is called a duplexer. In the terahertz frequency band, the waveguide structure has advantages such as high power capacity and low loss compared to other passive structures such as microstrip lines and substrate integrated waveguides, making it widely used in terahertz communication systems; in recent years, with the continuous development of terahertz receiver technology, higher requirements have been put forward for the performance of terahertz waveguide multiplexers.

[0005] At present, the structures of terahertz waveguide multiplexers are mainly hybrid coupling type and multi-branch coupling type. The hybrid coupling type multiplexer is composed of a coupler and a filter. Its advantage is that it can achieve no frequency gap between multiple channels, thereby avoiding the loss of terahertz signals. However, the architecture of the combination of couplers and filters makes the entire multiplexer larger in size, which not only increases the processing cost and the insertion loss of the multiplexer, but also is not conducive to the miniaturization design of the system. For example, a hybrid coupling type triplexer proposed in the document "Design and Development of a Hybrid-Coupled Waveguide Multiplexer for a Multiband Receiver" has a structure like Figure 1 As shown in the figure, it consists of six couplers and six filters. The model is very large, which greatly increases the design complexity and processing difficulty. In comparison, the multi-branch coupled multiplexer has the most compact circuit structure and can achieve the best performance in terms of absolute insertion loss and group delay response. It has become the best choice for multi-channel communication systems. However, this type of multiplexer does not have isolation elements such as circulators. All channel filters are directly connected to the main transmission line through short transmission line branches, resulting in any slight changes in any channel filter will affect other channels. Therefore, the design of this type of multiplexer is very complicated. In the past few decades, domestic and foreign scholars have only carried out related research at lower frequencies. In recent years, with the development of processing technologies such as high-precision CNC milling (CNC), multi-branch coupled multiplexers in the terahertz band have begun to be realized; such as the multi-branch coupled quadplexer proposed in the document "A 200–225-GHz Manifold-Coupled Multiplexer Utilizing Metal Waveguides", its structure is as follows Figure 2 As shown, four waveguide filters based on waveguide inductive membranes are directly connected through a short transmission line branch. However, this structure still cannot realize a continuous waveguide duplexer, that is, the frequency gap between channels cannot be avoided. Summary of the invention

[0006] The purpose of the present invention is to provide a terahertz continuous waveguide duplexer based on complementary filters, so as to solve the problem that the frequency gap between channels of the multi-branch coupling type multiplexer in the prior art cannot be avoided in the terahertz frequency band.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A terahertz continuous waveguide duplexer based on complementary filters comprises: a common port rectangular waveguide 1, a waveguide T-shaped section 2, an inductive diaphragm waveguide bandpass filter 3 and a capacitive diaphragm waveguide bandpass filter 4; wherein the common port rectangular waveguide 1, the inductive diaphragm waveguide bandpass filter 3 and the capacitive diaphragm waveguide bandpass filter 4 are respectively connected to three waveguide ports of the waveguide T-shaped section 2, and the inductive diaphragm waveguide bandpass filter 3 and the capacitive diaphragm waveguide bandpass filter 4 are perpendicular to each other.

[0009] Furthermore, the inductive diaphragm waveguide bandpass filter 3 and the capacitive diaphragm waveguide bandpass filter 4 are connected in parallel via the waveguide T-shaped section 2 to form a complementary filter.

[0010] Furthermore, the common port rectangular waveguide 1 and the waveguide T-section 2 are both standard rectangular waveguides.

[0011] Furthermore, the inductive membrane waveguide bandpass filter comprises: an input waveguide, an output waveguide, an inductive membrane and a resonant cavity, wherein an inductive membrane cascade is respectively connected between the resonant cavity and the input waveguide and the output waveguide, and an inductive membrane cascade is connected between adjacent resonant cavities.

[0012] Furthermore, the capacitive membrane waveguide bandpass filter comprises: an input waveguide, an output waveguide, a capacitive membrane and a resonant cavity; the resonant cavity is cascaded with the input waveguide and the output waveguide respectively through a capacitive membrane, and adjacent resonant cavities are cascaded with a capacitive membrane respectively.

[0013] It can be known from the working principle of the complementary filter that the imaginary impedance parts of the two filters constituting the duplexer should be opposite numbers in order to meet the condition of minimizing the reflection coefficient of the common port; therefore, the present invention creatively introduces a capacitive diaphragm waveguide bandpass filter in the design of a terahertz continuous waveguide duplexer. The imaginary impedance part of the capacitive diaphragm waveguide bandpass filter is negative, while the imaginary impedance part of the inductive diaphragm waveguide bandpass filter is positive. The two are connected in parallel to form a complementary filter, thereby realizing a continuous duplexer in the terahertz frequency band.

[0014] Based on the above technical solution, the beneficial effects of the present invention are:

[0015] The present invention applies complementary filter theory for the first time in the design of a terahertz continuous waveguide duplexer, and proposes a terahertz continuous waveguide duplexer based on complementary filters. A capacitive diaphragm waveguide bandpass filter is creatively introduced on the basis of a traditional multi-branch coupling structure. The imaginary part of the impedance of the capacitive diaphragm waveguide bandpass filter is negative, while the imaginary part of the impedance of the inductive diaphragm waveguide bandpass filter is positive. The two are connected in parallel through a waveguide T-section to form a complementary filter, which ultimately enables the duplexer to achieve good matching within the working bandwidth. This is the first time that a multi-branch coupling structure is used in the terahertz frequency band to realize the design of a waveguide continuous duplexer without a frequency gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of a hybrid coupling multiplexer in the prior art.

[0017] Figure 2 It is a schematic diagram of the structure of a multi-branch coupling multiplexer in the prior art.

[0018] Figure 3 It is a system block diagram of the continuous duplexer in the present invention.

[0019] Figure 4 It is a schematic diagram of the structure of the terahertz continuous waveguide duplexer based on complementary filters in the present invention, wherein 1 is a common port rectangular waveguide, 2 is a waveguide T-section, 3 is an inductive diaphragm waveguide bandpass filter, and 4 is a capacitive diaphragm waveguide bandpass filter.

[0020] Figure 5 It is a cross-sectional schematic diagram of the inductive diaphragm of the inductive diaphragm waveguide bandpass filter in the present invention.

[0021] Figure 6 It is a cross-sectional schematic diagram of the capacitive diaphragm of the capacitive diaphragm waveguide bandpass filter in the present invention.

[0022] Figure 7 It is a schematic diagram of the structure of the inductive diaphragm waveguide bandpass filter in the present invention.

[0023] Figure 8 It is a schematic structural diagram of the capacitive diaphragm waveguide bandpass filter in the present invention.

[0024] Fig. 9 This is a diagram of the S-parameter simulation results of the inductive diaphragm waveguide bandpass filter in the present invention.

[0025] Fig.10 This is a diagram of the S-parameter simulation results of the capacitive diaphragm waveguide bandpass filter in the present invention.

[0026] Fig.11 This is a diagram of the S-parameter simulation results of the terahertz continuous waveguide duplexer based on complementary filters in the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] In order to realize a terahertz continuous waveguide duplexer based on the structure of a multi-branch coupling type multiplexer, the present invention proposes a terahertz continuous waveguide duplexer based on the theoretical basis of complementary filters, so that it can achieve good matching within the working bandwidth. In terms of working principle, Figure 3As shown in the figure, the continuous duplexer is composed of a low-frequency filter and a high-frequency filter connected in parallel at a common T-junction. In order to minimize the reflection at the combined input port (port 1), the complex input admittance Y of the low-frequency filter is in,低频 The complex input admittance Y of the high frequency filter in,高频 The following equation should be satisfied:

[0029] Y in = Y in,低频 +Y in,高频 = Y0

[0030] Re(Y in,低频 )+ Re(Y in,高频 ) = Y0

[0031] Im(Y in,低频 )+ Im(Y in,高频 ) = 0

[0032] Among them, Y in represents the input admittance, Y in,低频 represents the complex input admittance of the low-frequency filter, Y in,高频 represents the complex input admittance of the high-frequency filter, and Y0 represents the admittance of the input port;

[0033] Two filters that satisfy the above equation are often called complementary filters.

[0034] On this basis, this embodiment provides a terahertz continuous waveguide duplexer based on a complementary filter, the structure of which is as follows: Figure 4 As shown, a multi-branch coupling structure is adopted, specifically including: a common port rectangular waveguide 1, a waveguide T-shaped section 2, an inductive diaphragm waveguide bandpass filter 3 and a capacitive diaphragm waveguide bandpass filter 4; wherein, the common port rectangular waveguide 1 and the waveguide T-shaped section 2 adopt a standard rectangular waveguide, the common port rectangular waveguide 1, the inductive diaphragm waveguide bandpass filter 3 and the capacitive diaphragm waveguide bandpass filter 4 are respectively connected to the three ports of the waveguide T-shaped section 2, and the inductive diaphragm waveguide bandpass filter 3 and the capacitive diaphragm waveguide bandpass filter 4 are perpendicular to each other.

[0035] The inductive diaphragm waveguide bandpass filter is as follows Figure 7As shown, it includes: a standard input waveguide, a standard output waveguide, an inductive diaphragm and a resonant cavity; the resonant cavity is cascaded with the standard input waveguide and the standard output waveguide respectively through an inductive diaphragm, and adjacent resonant cavities are also cascaded through an inductive diaphragm; a three-dimensional rectangular coordinate system is established with the center point of the waveguide port plane of the standard input waveguide as the coordinate origin, the signal propagation direction as the Y axis, and the electric field direction as the Z axis. The inductive diaphragm waveguide bandpass filter is symmetrical along the ZOY plane and the XOY plane. Further, the dimension in the X-axis direction is defined as the width, the dimension in the Y-axis direction is defined as the length, and the dimension in the Z-axis direction is defined as the height. The width and height of the resonant cavity are the same as those of the standard rectangular waveguide, and the width of the inductive diaphragm is smaller than that of the standard rectangular waveguide, and the height is the same as that of the standard rectangular waveguide.

[0036] The capacitive diaphragm waveguide bandpass filter is as follows Figure 8 As shown, it includes: a standard input waveguide, a standard output waveguide, a capacitive diaphragm and a resonant cavity; the resonant cavity is cascaded with the standard input waveguide and the standard output waveguide respectively through a capacitive diaphragm, and adjacent resonant cavities are also cascaded through a capacitive diaphragm; a three-dimensional rectangular coordinate system is established with the center point of the waveguide port plane of the standard input waveguide as the coordinate origin, the signal propagation direction as the Z axis, and the vertical downward direction of the electric field as the Y axis, and the capacitive diaphragm waveguide bandpass filter is symmetrical along the YOZ plane and the XOZ plane. Further, the dimension in the X-axis direction is defined as the width, the dimension in the Z-axis direction is defined as the length, and the dimension in the Y-axis direction is defined as the height. The width of the resonant cavity is the same as that of the standard rectangular waveguide, the width of the capacitive diaphragm is equal to that of the standard rectangular waveguide, and the height is less than that of the standard rectangular waveguide.

[0037] The inductive membrane waveguide bandpass filter 3 is used as a high-frequency filter, and the capacitive membrane waveguide bandpass filter 4 is used as a low-frequency filter. The two components constitute a channel in the duplexer, so that the duplexer can achieve the complementarity of the two filters within its working bandwidth, thereby achieving good matching of the common port. In the inductive membrane waveguide bandpass filter, the cross-section of the inductive membrane is as follows: Figure 5 As shown in the figure, the blank area corresponds to the cavity, and the shaded area corresponds to the metal. The signal is input from the direction perpendicular to the ZOX plane. The height of the inductive diaphragm is consistent with that of the standard waveguide, and the width is smaller than that of the standard waveguide, making the TE in the waveguide 10 The magnetic field of the mode is concentrated and strengthened in the inductive diaphragm, showing inductive characteristics, forming magnetic coupling, thereby exciting TE in the resonant cavity cascaded with the inductive diaphragm. 101 Resonance mode, TE in the resonant cavity 101 The resonant mode forms magnetic coupling in the inductive diaphragm at the other end, which in turn excites the TE in the next resonant cavity. 101 The resonant mode finally allows the signal frequency near the resonant frequency of the resonant cavity to pass, showing a bandpass characteristic. In the capacitive diaphragm waveguide bandpass filter, the cross section of the capacitive diaphragm is as follows Figure 6As shown in the figure, the blank area corresponds to the cavity, the shaded area corresponds to the metal, and the signal is input from the direction perpendicular to the XOY plane. The width of the capacitive diaphragm is consistent with that of the standard waveguide, and the height is smaller than that of the standard waveguide, so that the TE in the waveguide 10 The electric field of the mode is concentrated and strengthened in the capacitive diaphragm, showing capacitive characteristics, forming electrical coupling, thereby exciting the TE in the resonant cavity cascaded with the capacitive diaphragm. 101 Resonance mode, TE in the resonant cavity 101 The resonant mode forms electrical coupling in the capacitive diaphragm at the other end, thereby exciting the TE in the next resonant cavity. 101 The resonant mode also exhibits a bandpass characteristic.

[0038] It can be known from the working principle of the complementary filter that the imaginary impedance parts of the two filters constituting the duplexer should be opposite numbers in order to meet the condition of minimizing the reflection coefficient of the common port; therefore, the present invention creatively introduces a capacitive diaphragm waveguide bandpass filter in the design of a terahertz continuous waveguide duplexer. The imaginary impedance part of the capacitive diaphragm waveguide bandpass filter is negative, while the imaginary impedance part of the inductive diaphragm waveguide bandpass filter is positive. The two are connected in parallel to form a complementary filter, thereby realizing a continuous duplexer in the terahertz frequency band.

[0039] The beneficial effects of the present invention are described in detail below in conjunction with simulation tests.

[0040] The common port rectangular waveguide 1 and the waveguide T-section 2 are standard rectangular waveguides.

[0041] The inductive diaphragm waveguide bandpass filter is as follows Figure 7As shown, it is specifically a 6th-order terahertz waveguide bandpass filter, which includes, from left to right, an input waveguide, a first inductive diaphragm, a first resonant cavity, a second inductive diaphragm, a second resonant cavity, a third inductive diaphragm, a third resonant cavity, a fourth inductive diaphragm, a fourth resonant cavity, a fifth inductive diaphragm, a fifth resonant cavity, a sixth inductive diaphragm, a sixth resonant cavity, a seventh inductive diaphragm and an output waveguide; wherein, the input waveguide and the output waveguide adopt standard WR-6 waveguides, the width of the first inductive diaphragm is 1.05 mm, and the length is 0.2 mm, the length of the first resonant cavity is 0.69 mm, the width of the second inductive diaphragm is 0.88 mm, and the length is 0.25 mm, the length of the second resonant cavity is 0.75 mm, the width of the third inductive diaphragm is The width of the first inductive diaphragm is 0.86mm and the length is 0.25mm, the length of the third resonant cavity is 0.71mm, the width of the fourth inductive diaphragm is 0.88mm and the length is 0.25mm, the length of the fourth resonant cavity is 0.71mm, the width of the fifth inductive diaphragm is 0.86mm and the length is 0.25mm, the length of the fifth resonant cavity is 0.75mm, the width of the sixth inductive diaphragm is 0.9mm and the length is 0.23mm, the length of the sixth resonant cavity is 0.62mm, the width of the seventh inductive diaphragm is 1.1mm and the length is 0.21mm; and, in order to accurately simulate the filter in the actual application scenario, a fillet with a radius of 0.15mm caused by a high-precision CNC milling process is introduced into the simulation model.

[0042] The capacitive diaphragm waveguide bandpass filter structure is as follows: Figure 8As shown, it is specifically an 8th-order terahertz waveguide bandpass filter, including: four single-mode resonant cavities and one dual-mode resonant cavity, from left to right are an input waveguide, a first capacitive diaphragm, a first resonant cavity, a second capacitive diaphragm, a second resonant cavity, a third capacitive diaphragm, a third resonant cavity, a fourth capacitive diaphragm, a fourth resonant cavity, a fifth capacitive diaphragm, a fifth resonant cavity, a sixth capacitive diaphragm, a sixth resonant cavity, a seventh capacitive diaphragm, a seventh resonant cavity, an eighth capacitive diaphragm, an eighth resonant cavity, a ninth capacitive diaphragm and an output waveguide; wherein, the input waveguide and the output waveguide adopt a standard WR-6 waveguide, the first capacitive diaphragm has a height of 0.61 mm and a length of 0.2 mm, the first resonant cavity has a length of 0.63 mm, the second capacitive diaphragm has a height of 0.56 mm and a length of 0.2 mm, the second resonant cavity has a length of 0.7 mm, the third capacitive diaphragm has a height of 0.56 mm and a length of 0.2 mm, the third resonant cavity has a length of 0.7 mm, the third capacitive diaphragm has a height of 0.56 mm and a length of 0.2 mm, and the third resonant cavity has a length of 0.7 mm. The length of the resonance cavity is 0.68mm, the height of the fourth capacitive diaphragm is 0.56mm and the length is 0.2mm, the length of the fourth resonant cavity is 0.7mm, the height of the fifth capacitive diaphragm is 0.54mm and the length is 0.2mm, the length of the fifth resonant cavity is 0.59mm, the height of the sixth capacitive diaphragm is 0.51mm and the length is 0.2mm, the length of the sixth resonant cavity is 0.62mm, the height of the seventh capacitive diaphragm is 0.48mm and the length is 0.2mm, the length of the seventh resonant cavity is 0.58mm, the height of the eighth capacitive diaphragm is 0.48mm and the length is 0.2mm, the length of the eighth resonant cavity is 0.53mm, and the height of the ninth capacitive diaphragm is 0.64mm and the length is 0.2mm; and, in order to accurately simulate the filter in the actual application scenario, a fillet with a radius of 0.15mm caused by a high-precision CNC milling process is introduced into the simulation model.

[0043] like Fig. 9 FIG. 4 shows the S parameter simulation result of the inductive membrane waveguide bandpass filter in this embodiment, and the filter passband is 140 GHz to 160 GHz; Fig.10 FIG. 1 shows the S parameter simulation result of the capacitive membrane waveguide bandpass filter in this embodiment. The filter passband is 120 GHz to 140 GHz. The common port standard rectangular waveguide is port 1, the inductive membrane waveguide bandpass filter is port 2, and the capacitive membrane waveguide bandpass filter is port 3. Fig.11 This is the S-parameter simulation result of the terahertz continuous waveguide duplexer based on complementary filters in this embodiment. Within the working bandwidth of 120 GHz to 160 GHz, the common port reflection coefficient is lower than -16 dB, that is, almost all the signals input at the common port are output through the output port, thereby realizing a continuous waveguide duplexer without frequency gaps in the terahertz band.

[0044] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A terahertz continuous waveguide duplexer based on complementary filters, comprising: A common port rectangular waveguide (1), a waveguide T-shaped section (2), an inductive diaphragm waveguide bandpass filter (3) and a capacitive diaphragm waveguide bandpass filter (4); the common port rectangular waveguide (1), the inductive diaphragm waveguide bandpass filter (3) and the capacitive diaphragm waveguide bandpass filter (4) are respectively connected to three waveguide ports of the waveguide T-shaped section (2), and the inductive diaphragm waveguide bandpass filter (3) and the capacitive diaphragm waveguide bandpass filter (4) are perpendicular to each other.

2. The terahertz continuous waveguide duplexer based on complementary filters according to claim 1, characterized in that: The inductive diaphragm waveguide bandpass filter (3) and the capacitive diaphragm waveguide bandpass filter (4) are connected in parallel via a waveguide T-shaped section (2) to form a complementary filter.

3. The terahertz continuous waveguide duplexer based on complementary filters according to claim 1, characterized in that: The common port rectangular waveguide (1) and the waveguide T-shaped section (2) both adopt standard rectangular waveguides.

4. The terahertz continuous waveguide duplexer based on complementary filters according to claim 1, characterized in that: The inductive membrane waveguide bandpass filter comprises: an input waveguide, an output waveguide, an inductive membrane and a resonant cavity. An inductive membrane cascade is respectively passed between the resonant cavity and the input waveguide and the output waveguide, and an inductive membrane cascade is passed between adjacent resonant cavities.

5. The terahertz continuous waveguide duplexer based on complementary filters according to claim 1, characterized in that: The capacitive membrane waveguide bandpass filter comprises: an input waveguide, an output waveguide, a capacitive membrane and a resonant cavity; a capacitive membrane cascade is respectively passed between the resonant cavity and the input waveguide and the output waveguide, and a capacitive membrane cascade is passed between adjacent resonant cavities.

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