Microstrip hybrid circulator with high isolation

Abstract

The invention discloses a microstrip hybrid circulator with high isolation, and belongs to the technical field of microwaves and millimeter waves. Comprising a metal plate with a nail bed structure and a mixed circulator main body, and the metal plate comprises a cover plate metal plate and a metal pin array arranged on the face, facing the mixed circulator main body, of the cover plate metal plate; a gap is formed between the metal plate and the mixing circulator main body; the hybrid circulator main body comprises a micro-strip hybrid circulator, a dielectric substrate and a reference ground plane, the micro-strip hybrid circulator is arranged on the side, close to the metal plate, of the dielectric substrate, and the reference ground plane is arranged on the side, away from the metal plate, of the dielectric substrate. The periodic nail bed structure is designed to suppress coupling of surface waves and high-order modes, so that the isolation of the hybrid circulator is improved, and the hybrid circulator is suitable for multiple microwave and millimeter wave fields such as millimeter wave radar systems and the like.

Description

Technical Field

[0001] This invention belongs to the field of millimeter-wave short-range detection technology, specifically a microstrip hybrid circulator with high isolation. Background Technology

[0002] A microstrip hybrid circulator is a microwave passive device based on a ring resonant structure, commonly used in power distribution and signal synthesis applications. Its core consists of a ring transmission line, achieving directional coupling between ports through a specific geometric layout. Traditional microstrip hybrid circulators suffer from drawbacks such as poor port isolation, large physical size, and narrow operating bandwidth. In radar and communication systems, low transmit / receive isolation leads to significant signal energy leakage from the transmit channel to the receive channel, degrading system sensitivity and other performance characteristics. Furthermore, the narrow operating bandwidth further limits system performance improvements.

[0003] To address the issue of poor isolation in microstrip hybrid circulators, researchers have proposed several methods to improve the transmit-receive isolation of hybrid circulators.

[0004] Reference 1 (Lim, W.-G. and Yu, J.-W. (2008), Balanced circulator structure with enhanced isolation characteristics. Microw. Opt. Technol. Lett., 50:2389-2391. https: / / doi.org / 10.1002 / mop.23696) proposes a novel balanced circulator structure, which consists of two branch couplers and two circulators. By using coupling path cancellation, leakage signals from the circulator and reflected signals from the antenna are eliminated, improving the isolation of a single circulator by about 20 dB. However, due to the use of the principle of radio frequency cancellation, this structure has a relatively narrow bandwidth and is complex and large in size.

[0005] Reference 2 (Y. Liao, J. Liu and X. Ji, "Study of Millimeter Wave Circulators based on the methods of circular polarization isolation," 2022 IEEE 16th International Conference on Solid-State & Integrated Circuit Technology (ICSICT), Nangjing, China, 2022, pp. 1-3, doi: 10.1109 / ICSICT55466.2022.9963216.) designs a 224 GHz modular circulator with a probe positive transducer and a trench circular waveguide based on the circular polarization isolation method. This circulator employs a same-mode converter structure using a metal wire grid and a microstrip probe. When the linearly polarized wave is output from the transmitting port, the polarization converter converts the transmitted wave from linear polarization to circular polarization. After reflection from the target, the wave's polarization direction changes, and it is then converted back to linear polarization by the polarization converter, but rotated by 90°. At this point, the signal at the receiving port is orthogonal to the direction of the transmitting port, with an isolation of approximately 46 dB. However, this structure is relatively complex, and the polarization converter requires high precision, making it unsuitable for general applications. Summary of the Invention

[0006] To address the issue of transmit / receive isolation in existing technologies, this invention proposes a microstrip hybrid circulator with high isolation.

[0007] The technical solution to achieve the objective of this invention is as follows: a microstrip hybrid circulator with high isolation, comprising a metal plate with a bed of nails structure and a hybrid circulator body, wherein the metal plate includes a cover metal plate and an array of metal pins disposed on the side of the cover metal plate facing the hybrid circulator body; a gap is provided between the metal plate and the hybrid circulator body; the hybrid circulator body includes a microstrip hybrid circulator, a dielectric substrate and a reference ground plane, wherein the microstrip hybrid circulator is disposed on the side of the dielectric substrate close to the metal plate, and the reference ground plane is disposed on the side of the dielectric substrate away from the metal plate.

[0008] Preferably, the metal pin array is arranged periodically to form an artificial ideal magnetic conductor.

[0009] Preferably, the metal pins in the metal pin array are right quadrangular prism metal pins with a square base, and the metal pin array is perpendicular to the cover plate metal plate.

[0010] Preferably, the side length of the metal pins in the metal pin array is one-eighth of the working wavelength, the height is one-quarter of the working wavelength, and the spacing between the metal pins is also one-quarter of the working wavelength.

[0011] Preferably, the gap between the metal plate and the microstrip hybrid circulator is less than one-quarter of the operating wavelength.

[0012] Preferably, the microstrip hybrid circulator has four ports, with any one port as the input and two adjacent ports as the outputs. The distance between each port is one-quarter of the operating wavelength, and the signal phase difference between ports separated by 180° is to achieve radio frequency cancellation of the signal.

[0013] Preferably, the outer circumference of the microstrip hybrid circulator is three-half the operating wavelength.

[0014] Preferably, the difference between the inner and outer ring radii of the microstrip hybrid circulator is equal to the characteristic impedance under the dielectric constant of the dielectric substrate. The line width.

[0015] Compared with the prior art, the present invention has the following significant advantages: by using ideal electrical conductors and artificial ideal magnetic conductors to form an electromagnetic bandgap gap waveguide structure, the present invention suppresses the propagation of surface waves and higher-order modes, and still has a high transmit-receive isolation in the high-frequency band (V-band), which can be widely used in microwave and millimeter-wave systems; the present invention has a compact structure, simple power supply, and is more miniaturized than traditional RF front-end structures, which is easy to process and has low production cost.

[0016] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0017] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0018] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0019] Figure 1 This is a schematic diagram of the overall structure of a microstrip hybrid circulator with high isolation according to the present invention.

[0020] Figure 2 This is a front view of the overall structure of a microstrip hybrid circulator with high isolation according to the present invention.

[0021] Figure 3This is a schematic diagram of a nail bed structure metal plate of a microstrip hybrid circulator with high isolation according to the present invention.

[0022] Figure 4 This is a top view of a microstrip hybrid circulator with a bed of nails structure and high isolation, according to the present invention.

[0023] Figure 5 This is a front view of a metal plate with a bed of nails structure for a microstrip hybrid circulator with high isolation, according to the present invention.

[0024] Figure 6 This is a schematic diagram of the structure of a microstrip hybrid circulator with high isolation according to the present invention.

[0025] Figure 7 This is a top view of a microstrip hybrid circulator with high isolation according to the present invention.

[0026] Figure 8 This is a schematic diagram of the dimensions of a microstrip hybrid circulator with high isolation according to the present invention.

[0027] Figure 9 This is a simulation diagram of the return loss of a microstrip hybrid circulator with high isolation according to the present invention.

[0028] Figure 10 The isolation curve is shown for a microstrip hybrid circulator with high isolation according to the present invention. Detailed Implementation

[0029] It is readily understood that, based on the technical solution of this invention, various embodiments of the invention can be conceived by those skilled in the art without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention. Rather, these embodiments are provided to enable those skilled in the art to gain a more thorough understanding of the invention. Preferred embodiments of the invention are described below in conjunction with the accompanying drawings, which form part of this application and, together with the embodiments of the invention, serve to illustrate the innovative concept of the invention.

[0030] The concept of this invention is to combine Figures 1-2A microstrip hybrid circulator with high isolation includes a metal plate with a bed of nails structure and a hybrid circulator body. The metal plate includes a cover metal plate (1) and a metal pin array (2) disposed on the side of the cover metal plate facing the hybrid circulator body. A gap is provided between the metal plate and the hybrid circulator body. The hybrid circulator body includes a microstrip hybrid circulator (3), a dielectric substrate (4), and a reference ground plane (5). The microstrip hybrid circulator (3) is disposed on the side of the dielectric substrate (4) close to the metal plate, and the reference ground plane (5) is disposed on the side of the dielectric substrate (4) away from the metal plate. The hybrid circulator is integrated on the top surface of the dielectric substrate (4) in the form of a microstrip line, further optimizing signal transmission efficiency. The design of the metal pin array (2) is not only simple and practical, but also has a wide range of materials, low cost, and easy installation process, which can significantly reduce production costs while meeting high performance requirements. The overall structure combines functionality, economy, and manufacturability, and is suitable for various millimeter-wave application scenarios.

[0031] In a further embodiment, the metal pin array (2) is periodically arranged to form an artificial ideal magnetic conductor (AMC).

[0032] In a further embodiment, the metal pins in the metal pin array (2) are right quadrangular prism metal pins with a square base, and the metal pin array (2) is perpendicular to the cover metal plate (1).

[0033] In a further embodiment, the metal pins in the metal pin array (2) have a side length of one-eighth of the operating wavelength, a height of one-quarter of the operating wavelength, and a spacing between the metal pins that is also one-quarter of the operating wavelength. This design creates an electromagnetic bandgap structure that blocks the propagation of electromagnetic waves in a specific frequency band. This spacing is determined by the operating wavelength of the hybrid circulator, thereby effectively suppressing the propagation of surface waves, improving electromagnetic performance, and increasing the isolation between the transceiver ports.

[0034] In a further embodiment, the gap between the metal plate and the microstrip hybrid circulator (3) is less than one-quarter of the operating wavelength to form a gap waveguide with an electromagnetic bandgap, suppressing the propagation of surface waves, effectively reducing electromagnetic leakage of the microstrip line, ensuring signal integrity, and increasing the isolation between the transceiver ports.

[0035] In a further embodiment, the microstrip hybrid circulator (3) has four ports, with any one port as the input and two adjacent ports as the output. The distance between each port is one-quarter of the working wavelength, and the signal phase difference between the ports is 180° to achieve radio frequency cancellation of the signal.

[0036] In a further embodiment, the outer perimeter of the microstrip hybrid circulator (3) is three-half the operating wavelength to achieve good impedance matching.

[0037] In a further embodiment, the difference between the inner and outer ring radii of the microstrip hybrid circulator is equal to the characteristic impedance under the dielectric constant of the dielectric substrate. The line width.

[0038] like Figure 7 As shown, the microstrip hybrid circulator (3) is a four-port coupler. Ports A, B, C, and D are spaced one-quarter of the operating wavelength apart. Since adjacent ports are connected, this distance ensures that the amplitude and phase of the electromagnetic wave remain unchanged, minimizing electromagnetic wave loss. Ports A and D are spaced three-quarters of the wavelength apart. When a signal is input from port B, it will be output from both ports A and C simultaneously. However, a signal will also travel clockwise towards port D, at which point the electromagnetic wave passes through a path of length λ. At the same time, port B will also transmit an electromagnetic wave of equal amplitude counterclockwise, at which point the electromagnetic wave passes through a path of length λ. The path of length is 180° out of phase with the electromagnetic wave mentioned above, and the amplitude is equal. According to the principle of electromagnetic cancellation, the two signals will be canceled at port D, so ports B and D are isolated.

[0039] The present invention will be further described in detail below with reference to specific embodiments.

[0040] Example 1

[0041] This embodiment of a microstrip hybrid circulator with high isolation includes a metal plate with a bed of nails structure and a hybrid circulator body. The metal plate includes a cover metal plate (1) and an array of metal pins (2) disposed on the side of the cover metal plate facing the hybrid circulator body. A gap is provided between the metal plate and the hybrid circulator body. The hybrid circulator body includes a microstrip hybrid circulator (3), a dielectric substrate (4), and a reference ground plane (5). The microstrip hybrid circulator (3) is disposed on the side of the dielectric substrate (4) close to the metal plate, and the reference ground plane (5) is disposed on the side of the dielectric substrate (4) away from the metal plate.

[0042] like Figure 8 As shown, the dielectric constant (Dk) of the dielectric substrate 4 is 3.00 ± 0.04, the dielectric loss (Df) is 0.001 @ 10 GHz, the thickness of the dielectric substrate 4 is h0 = 0.254 mm, and the total thickness including the microstrip hybrid circulator (3) is h1 = 0.289 mm. The side length of the substrate is a1 = 10.2 mm. The width of the microstrip hybrid circulator (3) is such that the characteristic impedance under the dielectric constant of the dielectric substrate 4 is... The linewidth is as follows. The outer ring radius of the microstrip hybrid ring on the printed circuit board is r1 = 2.3 mm, the inner ring radius is r2 = 2 mm, and the width is 0.3 mm. z0 is the characteristic impedance of the microstrip hybrid circulator. The linewidth w0 = 0.54 mm is 50 Ω. The metal plate is placed directly above the microstrip hybrid circulator (3), close but not in contact. The gap between the lower surface of the metal pin and the upper surface of the microstrip hybrid circulator (3) is h4 = 0.5 mm. The height of each metal pin unit is h2 = 0.5 mm. The side length of the bottom section is d1 = 0.3 mm. The distance between each metal pin unit is d2 = 0.3 mm. The total thickness of the metal plate with the periodically arranged pin bed structure is h3 = 0.83 mm. The side length of the metal cover plate is a2 = 10.5 mm.

[0043] The overall structure was simulated and optimized using the simulation software Ansys-HFSS, and the resulting return loss curve is shown below. Figure 9 As shown, the isolation curve is as follows Figure 10 As shown.

[0044] like Figure 9 As shown, the reflection coefficient of this structure is less than -10dB in the frequency range of 54.09GHz-75GHz, basically covering the entire V-band frequency range.

[0045] like Figure 10 As shown, the designed microstrip hybrid circulator achieves better isolation than -20dB in the 60.3GHz-66.2GHz frequency range and better isolation than -30dB in the 61.4GHz-62.9GHz frequency range, thus achieving high isolation.

Claims

1. A microstrip hybrid circulator with high isolation, characterized in that, The application relates to a metal plate with a nail bed structure, a hybrid ring body, the metal plate comprising a cover plate metal plate (1) and a metal nail array (2) arranged on the side of the cover plate metal plate facing the hybrid ring body; a gap is arranged between the metal plate and the hybrid ring body; the hybrid ring body comprises a microstrip hybrid ring (3), a dielectric substrate (4) and a reference ground plane (5), the microstrip hybrid ring (3) is arranged on the side of the dielectric substrate (4) close to the metal plate, and the reference ground plane (5) is arranged on the side of the dielectric substrate (4) away from the metal plate.

2. The microstrip hybrid circulator with high isolation according to claim 1, characterized in that, The metal nail array (2) is periodically arranged to form an artificial ideal magnetic conductor.

3. The microstrip hybrid circulator with high isolation according to claim 1, characterized in that, The metal nails in the metal nail array (2) are straight quadrangular prism metal nails with square bottom surfaces, and the metal nail array (2) is perpendicular to the cover plate metal plate (1).

4. The microstrip hybrid circulator with high isolation according to claim 1, characterized in that, The side length of the metal nails in the metal nail array (2) is one-eighth of the working wavelength, the height of the metal nails is one-fourth of the working wavelength, and the interval between the metal nails is also one-fourth of the working wavelength.

5. The microstrip hybrid circulator with high isolation according to claim 1, characterized in that, The gap between the metal plate and the microstrip hybrid ring (3) is less than one-fourth of the working wavelength.

6. The microstrip hybrid circulator with high isolation according to claim 1, characterized in that, The microstrip hybrid ring (3) has four ports, any one port is used as an input, and two adjacent ports are used as outputs, the distance between each port is one-fourth of the working wavelength, the phase difference between the signals of the ports separated by one-fourth of the working wavelength is 180 DEG, and the radio frequency cancellation of the signals is realized.

7. The microstrip hybrid circulator with high isolation according to claim 1, characterized in that, The outer perimeter of the microstrip hybrid ring (3) is two-thirds of the working wavelength.

8. The microstrip hybrid circulator with high isolation according to claim 1, characterized in that, The difference between the inner and outer ring radius of the microstrip hybrid circulator is the line width of the characteristic impedance under the dielectric constant of the dielectric substrate. the line width of the characteristic impedance under the dielectric constant of the dielectric substrate.

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