An e-plane branch waveguide directional coupler
By introducing a pole extraction filter structure into the E-plane branched waveguide directional coupler, the amplitude non-flatness problem between the through port and the coupled port is solved, achieving higher frequency response consistency and a wider operating bandwidth.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-06
- Publication Date
- 2026-05-15
AI Technical Summary
The amplitude flatness difference between the through port and the coupled port in the existing E-plane branched waveguide directional coupler affects its performance in the high-frequency band.
A pole extraction filter structure is introduced outside the operating frequency band of the coupler. A filter for pole extraction is formed by connecting rectangular waveguides on the branch waveguides at both ends, generating independently controlled transmission zeros to reduce amplitude unevenness.
By introducing a pole extraction filter structure, the amplitude unevenness of the coupler output is reduced, the operating bandwidth is increased, and the consistency of frequency characteristics is improved.
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Figure CN116345104B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of coupling technology, specifically an E-plane branched waveguide directional coupler, which is applied to millimeter-wave terahertz radar or communication systems. Background Technology
[0002] Driven by the rapid development of emerging scientific and industrial applications, terahertz technology has attracted widespread research attention in recent years, making the study of corresponding terahertz devices increasingly important. Couplers are common four-port passive devices used for power distribution and power combining, primarily used to separate and extract input signals at different ratios, playing a crucial role in the microwave and terahertz frequency bands. Common four-port passive devices include directional couplers, magic-T couplers, and hybrid bridges. Compared to traditional power dividers, Wilkinson power dividers feature power splitting into two with in-phase output signals; directional couplers can achieve arbitrary power distribution ratios, with output phase differences of 90° or 180°. With technological advancements, directional couplers are operating at increasingly higher frequencies, smaller in size, and requiring higher precision. Rectangular waveguides, with air as the transmission medium, are simple in structure and easy to connect. At higher frequencies, they exhibit lower transmission loss and greater power carrying capacity than planar structures or other devices. Therefore, couplers operating at higher frequencies primarily utilize rectangular waveguides for transmission.
[0003] E-plane branched waveguide directional couplers based on rectangular waveguides exhibit high isolation, low return loss, low amplitude and phase unevenness, and low insertion loss over a wide bandwidth, making them highly promising for development and practical applications in the terahertz field.
[0004] For example, researchers such as Peer J. Sobis, Jan Stake, and Anders Emrich designed a directional coupler that can be used in terahertz band subharmonic mixers; see [link / reference]. Figure 1 As shown in (a), the phase between its through port and coupled port is 135° / 45°. See also... Figure 1 As shown in (b), the structure employs a six-branch 90° coupling structure with progressively increasing height. A 45° phase shifter, composed of three short-circuit stubs of varying lengths, is located at the output. Simulation results show that the coupler has a center frequency of 170 GHz and a relative bandwidth of 15%. Experimental results demonstrate that the maximum phase imbalance is less than 2° across the entire operating frequency band, the amplitude unevenness between the coupled and through ports is less than 0.4 dB, the isolation is less than 20 dB across the entire operating frequency band, and the return loss is also better than 20 dB.
[0005] For another example, researchers such as K. Lomakin from the University of Erlangen-Nuremberg in Germany used 3D printing technology to research and design an E-plane branch waveguide directional coupler with equal power division, mainly used in the E band. The team printed the overall circuit using plastic and silver-plated its surface. The circuit and test results are shown in Figure 2 (a) and Figure 2 (b). Throughout the E band, the measured amplitude flatness of this coupler is less than 1.5 dB, and the phase flatness is less than 4°.
[0006] For another example, researchers such as Shi Yanan from North University of China formed a new circuit composed of a "field" character and two "H" shapes by adding transverse through branches to the traditional branch line structure. This structure is processed using MEMS technology. The circuit model and test results are shown in Figure 3 (a), Figure 3 (b) and Figure 3 (c). The test results show that within the wide frequency band of 220 - 290 GHz, the return loss is less than -20 dB, the insertion loss is approximately equal to 1.55 dB, and the coupling degree is 12.3 ± 0.9 dB.
[0007] It can be seen that the E-plane branch waveguide directional couplers in the existing technology all have the problem of poor amplitude flatness between the through port and the coupling port. SUMMARY OF THE INVENTION
[0008] The purpose of the present invention is to: aiming at the problems existing in the existing E-plane branch waveguide directional couplers, propose an E-plane branch waveguide directional coupler, which generates an independently controllable transmission zero outside the operating frequency band of the coupler by adding an extraction pole filter, reduces the amplitude flatness of the coupler output, and increases the operating bandwidth.
[0009] To achieve the above object, the present invention adopts the following technical solutions:
[0010] An E-plane branch waveguide directional coupler includes: a first through waveguide and a second through waveguide arranged in parallel. The adjacent two sides of the first through waveguide and the second through waveguide are connected as a whole, and a coupling structure is provided at the connection. The coupling structure is multiple branch waveguides, and the multiple branch waveguides are arranged in parallel along the main axis direction of the first through waveguide; on the two branch waveguides at both ends, a rectangular waveguide is connected to each wide side far from the branch waveguide to form a filter structure for extracting poles.
[0011] Further, the width P of the rectangular waveguide constituting the filter is less than the distance t between the first through waveguide and the second through waveguide.
[0012] Further, the waveguide widths of the first through waveguide and the second through waveguide are the same.
[0013] Furthermore, the waveguide width and waveguide length of the multiple branch waveguides are all the same.
[0014] Furthermore, the E-plane branched waveguide directional coupler has an axisymmetric structure.
[0015] Furthermore, in the branched waveguide, the two branched waveguides located on both sides are the first branched waveguides, and the rest are the second branched waveguides. The two first branched waveguides have the same height, and the multiple second branched waveguides have the same height.
[0016] Furthermore, the height of the first branch waveguide is less than the height of the second branch waveguide.
[0017] This invention provides an E-plane branched waveguide directional coupler, which forms a filter structure for pole extraction by connecting a rectangular waveguide to each of the two branched waveguides located at both ends, on a wide side away from the branched waveguide. The pole extraction filter structure generates independent control zeros to reduce amplitude imbalance between the through ports and the coupling ports.
[0018] Compared with the prior art, the present invention generates transmission zeros outside the coupler's operating frequency band by introducing a pole extraction filter structure, thereby making |S31| flatter and the amplitude flatness of the output port higher. Attached Figure Description
[0019] Figure 1 The diagram shows an existing directional coupler used in terahertz band subharmonic mixers, where (a) is a physical diagram of the 170 GHz coupler and (b) is a structural diagram of the coupler.
[0020] Figure 2 This is an existing power-divided E-plane branched waveguide directional coupler, where (a) is a physical diagram of the coupler and (b) is a diagram of the test results of the coupler.
[0021] Figure 3 A directional coupler that penetrates the branches laterally is added to the traditional branch line structure, where (a) is the circuit model diagram, (b) is the test result diagram of S11 and S21, and (c) is the test result diagram of S31 and S41.
[0022] Figure 4 This is a schematic diagram of the pole extraction filter structure in the E-plane branched waveguide directional coupler of the present invention;
[0023] Figure 5 This is a schematic diagram of the three-dimensional structure of the E-plane branched waveguide directional coupler of the present invention;
[0024] Figure 6 This is a schematic diagram of the parameters of the front view of the E-plane branched waveguide directional coupler of the present invention;
[0025] Figure 7 This is a schematic diagram of the parameters of the side view of the E-plane branched waveguide directional coupler of the present invention;
[0026] Figure 8 The results of S21, S31, and S11 of the E-plane branched waveguide directional coupler in the embodiment are shown in the figure.
[0027] Figure 9 This is a diagram showing the amplitude non-flatness results of the E-plane branched waveguide directional coupler in the embodiment.
[0028] Figure 10 This is a diagram showing the phase non-flatness results of the E-plane branched waveguide directional coupler in the embodiment.
[0029] Figure 11 The figure shows the simulation results of the pole extraction filter structure in the E-plane branched waveguide directional coupler of the embodiment. Detailed Implementation
[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0031] See Figure 5 This embodiment provides an E-plane branched waveguide directional coupler, which has an axisymmetric structure. It includes a first through waveguide, a second through waveguide, and a coupling structure. The input and output ports are standard WR-10 waveguide ports. The first and second through waveguides are arranged in parallel, and the coupling structure connects them. The coupling structure consists of five branch waveguides, arranged parallel to the main axis of the first through waveguide. The two branch waveguides on either side are the first branch waveguides, and the rest are the second branch waveguides.
[0032] A rectangular waveguide is connected to each of the two branch waveguides located at both ends, along the wider side away from the branch waveguide, to form a filter structure for pole extraction. See the filter structure section. Figure 4 The filter structure can be viewed as a half-wavelength open-circuit resonator and a quarter-wavelength short-circuit resonator at different transmission zeros. For example... Figure 11 As shown, this embodiment treats the filter as a half-wavelength open-circuit resonator. In use, when the signal propagates half its wavelength along the propagation direction, the reflected wave is negatively correlated with the incident wave. Because their amplitudes are equal and out of phase, a transmission zero is generated. Applying the extraction node filter structure to a branch waveguide coupler will generate a transmission zero outside the coupler's operating frequency band. Thus, |S31| will be affected by the transmission, with its amplitude decreasing, making the curve of |S31| in the operating frequency band flatter.
[0033] During implementation, the parameters of the E-plane branched waveguide directional coupler are as follows: Figure 6 , Figure 7The first and second through waveguides have the same waveguide width. The two first branch waveguides have the same height, and the multiple second branch waveguides have the same height, with the height of the first branch waveguide being less than the height of the second branch waveguide. The multiple branch waveguides have the same waveguide width and length. The width P of the rectangular waveguide constituting the filter is less than the spacing t between the first and second through waveguides.
[0034] The E-plane branched waveguide directional coupler of this embodiment was simulated using the following parameters to verify its performance.
[0035] The E-plane branched waveguide directional coupler described in this embodiment is used in the W-band. The specific parameters of each component in the coupler are shown in the table below.
[0036] Parameter (mm) p q t w a c Wa Wb Novel Branch Waveguide Coupler 0.27 1.4 0.87 1.1 0.26 0.72 2.54 1.27
[0037] In the table above, p represents the width of the rectangular waveguide that forms the filter; q represents the length of the rectangular waveguide that forms the filter; t represents the distance between the two through waveguides; a and c represent the height of the branch waveguides; w represents the distance between the centers of the two branch waveguides; Wa represents the length of the through waveguide port; and wb represents the width of the through waveguide.
[0038] See Figure 8 , Figure 9 , Figure 10 As can be seen, the E-plane branched waveguide directional coupler of this embodiment, after introducing the pole extraction filter structure, has an operating bandwidth of approximately 16.54 GHz and a relative bandwidth of approximately 19.6% under the condition that the amplitude unflatness is less than 0.4 dB. Return loss and phase unflatness also meet the requirements. Furthermore, the amplitude unflatness of the E-plane branched waveguide coupler is reduced.
Claims
1. A directional coupler for E-plane branched waveguides, characterized in that, It includes: a first and a second straight waveguide arranged in parallel, the two adjacent sides of the first and second straight waveguides are connected as a whole, and a coupling structure is provided at the connection point. The coupling structure consists of multiple branch waveguides, which are arranged in parallel along the main axis of the first straight waveguide. A rectangular waveguide is connected to the wide side of each of the two branch waveguides located at both ends, away from the branch waveguide, to form a filter structure for extracting poles to generate transmission zeros outside the operating frequency band of the coupler.
2. The E-plane branched waveguide directional coupler according to claim 1, characterized in that: The width P of the rectangular waveguide that forms the filter is smaller than the spacing t between the first and second through waveguides.
3. The E-plane branched waveguide directional coupler according to claim 1, characterized in that: The first and second through waveguides have the same waveguide width.
4. The E-plane branched waveguide directional coupler according to claim 1, characterized in that: The multiple branch waveguides have the same waveguide width and waveguide length.
5. The E-plane branched waveguide directional coupler according to claim 1, characterized in that: The E-plane branched waveguide directional coupler has an axisymmetric structure.
6. The E-plane branched waveguide directional coupler according to claim 1, characterized in that: In the branched waveguide, the two branched waveguides located on both sides are the first branched waveguides, and the rest are the second branched waveguides. The two first branched waveguides have the same height, and the multiple second branched waveguides have the same height.
7. The E-plane branched waveguide directional coupler according to claim 6, characterized in that: The height of the first branch waveguide is less than the height of the second branch waveguide.