A Terahertz Continuous Waveguide Diplexer Based on Complementary Filter

Abstract

The present invention belongs to the field of terahertz waveguide devices, and specifically provides a terahertz continuous waveguide duplexer based on a complementary filter to solve the problem that the multi-branch coupling type multiplexer in the prior art cannot avoid the frequency gap between channels in the terahertz band. The present invention includes: a common-end rectangular waveguide 1, a waveguide T-junction 2, an inductive diaphragm waveguide band-pass filter 3, and a capacitive diaphragm waveguide band-pass filter 4. For the first time, the complementary filter theory is applied, and a capacitive diaphragm waveguide band-pass filter is creatively introduced on the basis of the traditional multi-branch coupling type structure. The imaginary part of the impedance of the capacitive diaphragm waveguide band-pass filter is negative, while the imaginary part of the impedance of the inductive diaphragm waveguide band-pass filter is positive. The two are connected in parallel through the waveguide T-junction to form a complementary filter, and finally, a good match is achieved within the working bandwidth of the duplexer. For the first time, a waveguide continuous duplexer design without frequency gaps is realized using a multi-branch coupling type structure in the terahertz band.

Description

Technical Field

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

[0002] Terahertz waves usually refer to electromagnetic waves with frequencies in the range of 0.1 THz to 10 THz and wavelengths between 0.03 mm and 3 mm. In the electromagnetic spectrum, terahertz waves are in 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 means and technical conditions at that time, the development of terahertz waves was mainly limited to high-resolution spectroscopy and space remote sensing fields. With the continuous progress of science and technology, terahertz technology has developed greatly, and many emerging disciplines and application fields have emerged continuously, making terahertz technology a research hotspot in the international academic and industrial communities.

[0003] In the field of wireless communication, terahertz waves can theoretically support high-speed data transmission from dozens of Gbit / s to several Tbit / s, far higher than wireless communication in the microwave and millimeter-wave frequency bands. Given the many advantages of terahertz waves in the communication field, 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 simultaneously receive multiple channels without changing the local oscillator frequency. However, due to the bandwidth limitations of mixers and low-noise amplifiers, the current receiver's instantaneous bandwidth is still very limited.

[0004] To increase 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. The multiplexer contains multiple channels with filtering functions. Among them, 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 mainly include two types: hybrid-coupled type and multi-stub coupled type. The hybrid-coupled multiplexer is composed of a coupler and a filter. Its advantage is that it can achieve no frequency gap between multiple channels, thus avoiding the loss of terahertz signals. However, the architecture of the combination of the coupler and the filter makes the whole multiplexer large 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 triple multiplexer of the hybrid-coupled type proposed in the literature "Design and Development of a Hybrid-Coupled Waveguide Multiplexer for a Multiband Receiver" has a structure as shown in Figure 1 shown, which is composed of six couplers and six filters, and the model is very large, greatly increasing the design complexity and processing difficulty. In contrast, the multi-stub coupled multiplexer has the most compact circuit structure and can achieve the best performance in terms of absolute insertion loss and group delay response, etc., and has become the best choice for multi-channel communication systems. However, there is no isolation element such as a circulator in this type of multiplexer, and all channel filters are directly connected to the main transmission line through short transmission line stubs, resulting in that any small change in one channel filter will affect other channels. Therefore, the design of this type of multiplexer is very complex. In the past few decades, domestic and foreign scholars have only carried out relevant research at lower frequencies. In recent years, with the development of processing technologies such as high-precision computer numerical control milling (CNC), the multi-stub coupled multiplexer in the terahertz band has begun to be realized. For example, a quadruple multiplexer of the multi-stub coupled type proposed in the literature "A 200–225-GHz Manifold-Coupled Multiplexer Utilizing Metal Waveguides" has a structure as shown in Figure 2 shown, and 4 waveguide filters based on waveguide inductive diaphragms are directly connected through a short transmission line stub. However, this structure still cannot realize a continuous waveguide duplexer, that is, it cannot avoid the frequency gap between channels. Summary of the Invention

[0006] The purpose of the present invention is to provide a terahertz continuous waveguide duplexer based on complementary filters to solve the problem that the multi-stub coupled multiplexer in the prior art cannot avoid the frequency gap between channels in the terahertz band.

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

[0008] A terahertz continuous waveguide duplexer based on a complementary filter, comprising: a common port rectangular waveguide 1, a waveguide T-junction 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-junction 2, and the inductive diaphragm waveguide bandpass filter 3 and the capacitive diaphragm waveguide bandpass filter 4 are perpendicular to each other.

[0009] Further, the inductive diaphragm waveguide bandpass filter 3 and the capacitive diaphragm waveguide bandpass filter 4 are connected in parallel through the waveguide T-junction 2 to form a complementary filter.

[0010] Further, both the common port rectangular waveguide 1 and the waveguide T-junction 2 adopt standard rectangular waveguides.

[0011] Further, the inductive diaphragm waveguide bandpass filter comprises: an input waveguide, an output waveguide, an inductive diaphragm and a resonant cavity, and the resonant cavity is cascaded with the input waveguide and the output waveguide respectively through an inductive diaphragm, and adjacent resonant cavities are cascaded through an inductive diaphragm.

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

[0013] It can be known from the working principle of the complementary filter that the imaginary parts of the impedances of the two filters constituting the duplexer should be opposite numbers 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 the terahertz continuous waveguide duplexer. 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 to form a complementary filter, thereby realizing a continuous duplexer in the terahertz frequency band.

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

[0015] The present invention first applies the complementary filter theory in the design of the terahertz continuous waveguide duplexer, and proposes a terahertz continuous waveguide duplexer based on a complementary filter. On the basis of the traditional multi-section coupling type structure, a capacitive diaphragm waveguide bandpass filter is creatively introduced. 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 the waveguide T-junction to form a complementary filter, and finally the duplexer realizes good matching within the working bandwidth, and for the first time uses a multi-section coupling type structure in the terahertz frequency band to realize the design of a waveguide continuous duplexer without frequency gaps. Description of the Drawings

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

[0017] Figure 2 It is a schematic structural diagram of a multi-stub coupled 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 structural diagram of a terahertz continuous waveguide duplexer based on a complementary filter in the present invention. Among them, 1 is a common port rectangular waveguide, 2 is a waveguide T-junction, 3 is an inductive diaphragm waveguide bandpass filter, and 4 is a capacitive diaphragm waveguide bandpass filter.

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

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

[0022] Figure 7 It is a schematic structural diagram 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] Figure 9 It is a diagram of the simulation result of the S-parameters of the inductive diaphragm waveguide bandpass filter in the present invention.

[0025] Figure 10 It is a diagram of the simulation result of the S-parameters of the capacitive diaphragm waveguide bandpass filter in the present invention.

[0026] Figure 11 It is a diagram of the simulation result of the S-parameters of the terahertz continuous waveguide duplexer based on a complementary filter in the present invention. Detailed implementation manners

[0027] To make the objectives, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] In order to implement a terahertz continuous waveguide duplexer on the basis of the structure of a multi-stub coupled multiplexer, the present invention proposes a terahertz continuous waveguide duplexer based on the theory of complementary filters, so as to achieve good matching within the working bandwidth. In terms of the working principle, as Figure 3As shown, the continuous duplexer is formed by parallel connection of a low-frequency filter and a high-frequency filter at a common T-junction. To minimize reflection at the combined input port (port 1), the complex input admittance Y in,低频 of the low-frequency filter and the complex input admittance Y in,高频 of the high-frequency filter should satisfy the following equations:

[0029] Y in = Y in,低频 +Y in,高频 = Y 0

[0030] Re(Y in,低频 )+ Re(Y in,高频 )= Y 0

[0031] Im(Y in,低频 )+ Im(Y in,高频 )= 0

[0032] where 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 Y 0 represents the admittance of the input port;

[0033] Two filters that satisfy the above equations are usually referred to as complementary filters.

[0034] On this basis, this embodiment provides a terahertz continuous waveguide duplexer based on complementary filters, and its structure is as Figure 4 shown. It adopts a multi-section coupling structure, specifically including: a common port rectangular waveguide 1, a waveguide T-junction 2, an inductive diaphragm waveguide band-pass filter 3, and a capacitive diaphragm waveguide band-pass filter 4. Among them, the common port rectangular waveguide 1 and the waveguide T-junction 2 adopt standard rectangular waveguides. The common port rectangular waveguide 1, the inductive diaphragm waveguide band-pass filter 3, and the capacitive diaphragm waveguide band-pass filter 4 are respectively connected to the three ports of the waveguide T-junction 2, and the inductive diaphragm waveguide band-pass filter 3 and the capacitive diaphragm waveguide band-pass filter 4 are perpendicular to each other.

[0035] The inductive diaphragm waveguide band-pass filter is as Figure 7As shown in the figure, it includes: a standard input waveguide, a standard output waveguide, a 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; taking 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, a three-dimensional rectangular coordinate system is established, and the inductive diaphragm waveguide bandpass filter is symmetric along both 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 as described Figure 8 As shown in the figure, 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; taking 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 electric field direction vertically downward as the Y-axis, a three-dimensional rectangular coordinate system is established, and the capacitive diaphragm waveguide bandpass filter is symmetric along both 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, and the width of the capacitive diaphragm is equal to that of the standard rectangular waveguide and the height is smaller than that of the standard rectangular waveguide.

[0037] The inductive diaphragm waveguide bandpass filter 3 serves as a high-frequency filter, and the capacitive diaphragm waveguide bandpass filter 4 serves as a low-frequency filter. The two respectively form a channel in the duplexer, enabling the duplexer to achieve the complementarity of the two filters within its operating bandwidth, thereby achieving good matching at the common port. In the inductive diaphragm waveguide bandpass filter, the cross-section of the inductive diaphragm is as Figure 5 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 the same as that of the standard waveguide and the width is smaller than that of the standard waveguide, so that the magnetic field of the TE 10 mode in the waveguide is concentrated and strengthened in the inductive diaphragm, showing inductive characteristics and forming magnetic coupling, thereby exciting the TE 101 resonant mode in the resonant cavity cascaded with the inductive diaphragm. The TE 101 resonant mode in the resonant cavity forms magnetic coupling in the inductive diaphragm at the other end, and then excites the TE 101 resonant mode in the next resonant cavity. Finally, the signal frequency near the resonant frequency of the resonant cavity is passed, showing bandpass characteristics. In the capacitive diaphragm waveguide bandpass filter, the cross-section of the capacitive diaphragm is as Figure 6As shown, 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 XOY plane. The width of the capacitive diaphragm is the same as that of the standard waveguide, and the height is less than that of the standard waveguide, so that the electric field of the TE 10 mode in the waveguide is concentrated and strengthened in the capacitive diaphragm, showing capacitive characteristics and forming an electric coupling, thereby exciting the TE 101 resonant mode in the resonant cavity cascaded with the capacitive diaphragm. The TE 101 resonant mode in the resonant cavity forms an electric coupling in the capacitive diaphragm at the other end, and then excites the TE 101 resonant mode in the next resonant cavity, also showing band-pass characteristics.

[0038] According to the working principle of the complementary filter, the imaginary parts of the impedances of the two filters constituting the duplexer should be opposite numbers to meet the condition of minimizing the common-port reflection coefficient. Therefore, in the design of the terahertz continuous waveguide duplexer of the present invention, a capacitive-diaphragm waveguide band-pass filter is creatively introduced. The imaginary part of the impedance of the capacitive-diaphragm waveguide band-pass filter is negative, while the imaginary part of the impedance of the inductive-diaphragm waveguide band-pass filter is positive. The two are combined in parallel to form a complementary filter, thereby realizing a continuous duplexer in the terahertz band.

[0039] The beneficial effects of the present invention will be described in detail below in combination with simulation tests.

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

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

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

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

[0044] The above are only specific embodiments of the present invention. Any feature disclosed in this specification, unless specifically stated, can be replaced by other equivalent or alternative features with similar purposes; all the disclosed features, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any manner.

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; 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; and the common port rectangular waveguide (1) and the waveguide T-shaped section (2) both adopt standard rectangular waveguides.

2. 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.

3. 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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