Design method of miniaturized broadband 90-degree hybrid bridge

Abstract

The invention discloses a design method for a miniaturized broadband 90-degree hybrid bridge, and belongs to the technical field of hybrid bridges, and the method comprises the steps: employing a symmetric design of six layers of PCBs, enabling the first layer and the sixth layer to be respectively a symmetric bottom layer and a top layer, enabling the four sides to be provided with four ports of the hybrid bridge, enabling the second layer and the fifth layer to be respectively two symmetric optimization adjustment layers, and enabling the bottom layer and the top layer to be respectively provided with four ports of the hybrid bridge; branches are added to four ports, defect grounds are constructed on the two sides of the four ports, the third layer and the fourth layer are symmetrical signal layers, the wiring length is 1 / 4 wavelength of the center frequency, a Rogers Ro4350B plate with the dielectric constant being 3.66 is adopted between the first layer and the second layer, a Rogers 4450F prepreg with the dielectric constant being 3.52 is adopted between the second layer and the third layer, an FR4 prepreg plate with the dielectric constant being 3.96 is adopted between the third layer and the fourth layer, and the FR4 prepreg plate with the dielectric constant being 3.96 is adopted between the third layer and the fourth layer. A Rogers 4450F prepreg with the dielectric constant being 3.52 is adopted between the fourth layer and the fifth layer, and a Rogers Ro4350B plate with the dielectric constant being 3.66 is adopted between the fifth layer and the sixth layer. According to the invention, the requirements of a miniaturized and broadband strip line bridge are met.

Description

Technical Field

[0001] The invention relates to a design method of a miniaturized, wide-band 90° hybrid electric bridge, belonging to the technical field of electric bridges. Background Art

[0002] The 3dB90° hybrid bridge is an important RF device that can realize signal distribution and synthesis. Its internal structure is carefully designed based on the principle of electromagnetic field coupling to achieve specific performance. The input signal undergoes complex transformation in the bridge to achieve a 3dB attenuation characteristic and a 90° phase difference in the output signal.

[0003] In modern communications and microwave systems, 3dB 90° hybrid bridges have extremely broad applications. They are widely used in 4G / 5G base stations, 5G network coverage, Beidou navigation, and high-precision vehicle navigation (unmanned driving) antennas. Specifically, they enable power synthesis and distribution, as well as signal acquisition, in high-power microwave amplifier systems. They are used in active phased array radars, microwave transceiver components, microwave amplifiers, radio stations, and satellite communications.

[0004] As modern communications and microwave systems develop towards miniaturization and integration, the requirements for the size and performance of bridges are becoming increasingly higher. Therefore, high-performance and miniaturized bridge design is extremely critical to component design.

[0005] Currently, in the P-band, the most common bridges on the market are transformer-type bridges and stripline-type bridges. However, the saturation magnetization intensity of the ferrite (commonly known as a magnetic ring) used in transformer-type bridges is closely related to temperature and frequency, resulting in poor product consistency, a large production and debugging workload, and an inability to meet high-power requirements. Common P-band stripline-type bridges, on the other hand, are based on transmission line design theory, requiring a stripline length of a quarter wavelength, resulting in larger product sizes and a narrow bandwidth, typically between 1.1 and 1.5 times the frequency. Therefore, reasonable optimization of the internal structure and special designs are necessary to meet the demand for miniaturized and broadband stripline bridges. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a design method for a miniaturized, broadband 90° hybrid bridge, which reduces the product size and improves the bandwidth, thereby meeting the demand for miniaturized and broadband stripline bridges.

[0007] The technical solution adopted by the present invention is: a miniaturized wide-band 90° hybrid bridge design method, the method is: the hybrid bridge adopts a symmetrical design of a 6-layer PCB board, the first layer and the sixth layer are respectively the bottom layer and the top layer, four port pads are set at the four corners of the hybrid bridge, and the four port pads are respectively the input end, the output 0° 3dB end, the output 90° 3dB end and the isolation end; the middle is a large-surface ground shield, the second layer and the fifth layer are respectively the first optimization adjustment layer and the second optimization adjustment layer, branches are added to the four ports and defective grounds are constructed on both sides, the third layer and the fourth layer are respectively the first stripline coupled signal routing layer and the second stripline coupled signal routing layer, the routing length of the first stripline coupled signal routing layer and the second stripline coupled signal routing layer is 1 / 4 wavelength of the center frequency, the first stripline coupled signal routing layer and the second stripline coupled signal routing layer use curved routing, the routing corners are chamfered, and ground shielding is added at the ports. Rogers with a dielectric constant of 3.66 is used between the first and second layers. Ro4350B board, dielectric thickness 0.254mm, Rogers4450F semi-cured sheet with a dielectric constant of 3.52 is used between the second and third layers, dielectric thickness 0.1mm, FR4 semi-cured sheet with a dielectric constant of 3.96 is used between the third and fourth layers, dielectric thickness 0.05mm, Rogers4450F semi-cured sheet with a dielectric constant of 3.52 is used between the fourth and fifth layers, dielectric thickness 0.1mm, Rogers Ro4350B board with a dielectric constant of 3.66 is used between the fifth and sixth layers, dielectric thickness 0.254mm, the 6-layer PCB board is made by stacking and mixing, with metal edging all around and semi-circular hole metallization treatment on the port.

[0008] The beneficial effects of the present invention are as follows: compared with the prior art, the present invention adopts a hybrid bridge arranged with a 6-layer PCB board to meet the requirements of a miniaturized and wide-band stripline bridge. After testing: the hybrid bridge has an application frequency of 225MHz-678MHz, a bandwidth of approximately 3 times the frequency (678 / 225), a size of 8mm*6mm*0.9mm (the existing size is 21mm*19mm*3.6mm), a loss of less than 3.8dB, a phase difference of 90°±5°, an isolation of greater than 15dB, and a return loss of greater than 15dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is the schematic diagram of the 90° hybrid bridge; Figure 2 This is a schematic diagram of the three-dimensional structure of the 90° hybrid bridge (perspective); Figure 3 This is a front view schematic diagram of the 90° hybrid bridge (perspective); Figure 4 This is a left-side structural diagram of a 90° hybrid bridge (perspective); Figure 5 This is a top view of the 90° hybrid bridge (excluding the plates between layers 1-6); Figure 6 It is a schematic diagram of the three-dimensional structure of the 90° hybrid bridge; Figure 7 This is a top view structural diagram of a 90° hybrid bridge; Figure 8 yes Figure 7 Schematic diagram of the AA section structure; Figure 9 It is the layout diagram of the bottom layer of the PCB board; Figure 10 This is the layout diagram of the first adjustment optimization layer of the PCB board; Figure 11 This is the layout diagram of the first signal layer of the PCB board; Figure 12 This is the layout diagram of the second signal layer of the PCB board; Figure 13 This is the layout diagram of the second adjustment optimization layer of the PCB board; Figure 14 It is the layout diagram of the top layer of the PCB board; Figure 15 This is the circuit diagram of the 90° hybrid bridge; Figure 16 It is the S parameter curve; Figure 17 is the phase difference curve. DETAILED DESCRIPTION

[0010] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0011] Figure 1 This is the schematic diagram of a 90° hybrid bridge. The bridge consists of two striplines coupled by the upper and lower stripline widths. Pin 1 is the input terminal and Pin 2 is the isolation terminal. The signal is input from port 1 and output from port 3. Part of the signal is output from port 4 through coupling. The output signals of port 3 and port 4 differ by 90°. The product ports are reciprocal and interchangeable.

[0012] The overall structure of the design is as follows Figure 2 As shown, the product is made of a multi-layer PCB mixed-pressure integrated design. The main technical parameters of the product are as follows: application frequency 225MHz-678MHz, bandwidth is approximately 3 times the frequency (678 / 225), size is 8mm*6mm*0.9mm, loss is less than 3.8dB, phase difference is 90°±5°, isolation is greater than 15dB, and return loss is greater than 15dB.

[0013] Example 1: Figure 1-15As shown in FIG, a design method for a miniaturized, wide-band 90° hybrid bridge is provided. The method is as follows: the hybrid bridge adopts a symmetrical design of a 6-layer PCB board, the first layer and the sixth layer are the bottom layer and the top layer respectively, four port pads are set at the four corners of the hybrid bridge, and the four port pads are respectively the input terminal, the output 0° 3dB terminal, the output 90° 3dB terminal and the isolation terminal; the middle is a large-surface ground shield, the second layer and the fifth layer are respectively the first optimization adjustment layer and the second optimization adjustment layer, branches are added to the four ports and defective grounds are constructed on both sides, and the third layer is The first and second stripline coupled signal routing layers are the first and second stripline coupled signal routing layers, respectively. The routing lengths of the first and second stripline coupled signal routing layers are 1 / 4 wavelength of the center frequency. The first and second stripline coupled signal routing layers use curved routing, with corners cut off at the routing corners. Grounding is added at the ports (rectangular metal sheets and metal edging are connected to the large surface grounding) for shielding. Rogers with a dielectric constant of 3.66 is used between the first and second layers. Ro4350B board, dielectric thickness 0.254mm, Rogers4450F semi-cured sheet with a dielectric constant of 3.52 is used between the second and third layers, dielectric thickness 0.1mm, FR4 semi-cured sheet with a dielectric constant of 3.96 is used between the third and fourth layers, dielectric thickness 0.05mm, Rogers4450F semi-cured sheet with a dielectric constant of 3.52 is used between the fourth and fifth layers, dielectric thickness 0.1mm, Rogers Ro4350B board with a dielectric constant of 3.66 is used between the fifth and sixth layers, dielectric thickness 0.254mm, the 6-layer PCB board is made by stacking and mixing, with metal edging all around and semi-circular hole metallization treatment on the port.

[0014] A miniaturized, wide-band 90° hybrid bridge is designed, comprising a 6-layer PCB board 1, wherein the 1st and 6th layers are respectively the bottom layer 9 and the top layer 10, the 2nd and 5th layers are respectively the first optimization adjustment layer 11 and the second optimization adjustment layer 12, and the 3rd and 4th layers are respectively the first stripline coupling signal routing layer 13 and the second stripline coupling signal routing layer 14. Four port pads are provided at the four corners of the PCB board 1, and the four port pads are respectively the input terminal 2, the output 0° 3dB terminal 3, the output 90° 3dB terminal 4 and the isolation terminal 5. Two large-area ground shielding surfaces 6 electrically connected to each other are provided in the middle of the bottom layer 9 and the top layer 10 to achieve grounding. The large-area ground shielding surface 6 is cross-shaped. The first optimization adjustment layer 11 and the 4th layer are respectively cross-shaped. The second optimized adjustment layer 12 is provided with four open branches 7 at the four ports and two defective grounds 8 on the front and back sides. There are a total of eight open branches 7 and four defective grounds 8 in the two layers. The four open branches 7 are arranged opposite to each other in pairs on the left and right. The defective ground 8 adopts 15 periodically staggered T-shaped defective grounds cascaded. The cascaded T-shaped defective grounds are connected to the large-area ground shielding surface 6 with the metal edging. The routing length of the first stripline coupled signal routing layer 13 and the second stripline coupled signal routing layer 14 is 1 / 4 wavelength of the center frequency. The first stripline coupled signal routing layer 13 and the second stripline coupled signal routing layer 14 adopt curved routing. A first Rogers with a dielectric constant of 3.66 is set between the bottom layer and the first optimized adjustment layer. Ro4350B board 15, RogersRo4350B board 15 thickness is 0.254mm, a first Rogers4450F prepreg 16 with a dielectric constant of 3.52 is set between the first optimization adjustment layer 11 and the first stripline coupling signal routing layer 13, the first Rogers4450F prepreg 16 thickness is 0.1mm, a FR4 prepreg board 17 with a dielectric constant of 3.96 is set between the first stripline coupling signal routing layer 13 and the second stripline coupling signal routing layer 14, the FR4 prepreg board 17 thickness is 0.05mm, a second Rogers4450F prepreg 18 with a dielectric constant of 3.52 is set between the second stripline coupling signal routing layer 14 and the second optimization adjustment layer 12, the second Rogers4450F prepreg 18 thickness is 0.1mm, a second Rogers4450F prepreg 18 with a dielectric constant of 3.66 is set between the second optimization adjustment layer 12 and the top layer 10. Ro4350B plate 19, the second Rogers Ro4350B plate 19 has a thickness of 0.254 mm. The 6-layer PCB board is formed by laminating and mixing the first Rogers Ro4350B plate 15, the first Rogers4450F prepreg 16, the FR4 prepreg plate 17, the second Rogers4450F prepreg 18 and the second Rogers Ro4350B plate 19. The four sides of the PCB board 1 are metal-edged, and the four ports are metallized with semicircular holes.The corners of the curved routing are chamfered, and rectangular metal sheets 20 are provided near the four ports of the first stripline coupled signal routing layer 13 and the second stripline coupled signal routing layer 14 for grounding.

[0015] The first and second optimization adjustment layers 11 and 12 each add branches to the four ports and construct defective ground planes on both sides to improve bandwidth and return loss. These branches and open transmission lines increase coupling capacitance compensation, thereby enhancing isolation and bandwidth. Defective ground planes are created by etching periodic or aperiodic patterns into the grounded metal plate, imparting band-stop, slow-wave characteristics, and high equivalent characteristic impedance, thereby increasing bandwidth. Bends are used to reduce footprint, and corners are cut to minimize impedance mismatch. Metal edging is used all around to shield against interference and electromagnetic leakage, and ports feature semicircular hole metallization to ensure soldering reliability.

[0016] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A design method for a miniaturized, broadband 90° hybrid bridge, characterized in that: The method is as follows: the hybrid bridge adopts a symmetrical design of a 6-layer PCB board, the first and sixth layers are the bottom and top layers respectively, four port pads are set at the four corners of the hybrid bridge, and the four port pads are the input end, the output 0°3dB end, the output 90°3dB end and the isolation end respectively; the middle is a large-surface ground shield, the second and fifth layers are the first optimization adjustment layer and the second optimization adjustment layer respectively, branches are added to the four ports and defective grounds are constructed on both sides; the third and fourth layers are the first stripline coupled signal routing layer and the second stripline coupled signal routing layer respectively, the routing length of the first stripline coupled signal routing layer and the second stripline coupled signal routing layer is 1 / 4 wavelength of the center frequency, the first stripline coupled signal routing layer and the second stripline coupled signal routing layer use curved routing, and Rogers with a dielectric constant of 3.66 is used between the first and second layers. Ro4350B board, dielectric thickness 0.254mm, Rogers4450F semi-cured sheet with a dielectric constant of 3.52 is used between the 2nd and 3rd layers, dielectric thickness 0.1mm, FR4 semi-cured sheet with a dielectric constant of 3.96 is used between the 3rd and 4th layers, dielectric thickness 0.05mm, Rogers4450F semi-cured sheet with a dielectric constant of 3.52 is used between the 4th and 5th layers, dielectric thickness 0.1mm, RogersRo4350B board with a dielectric constant of 3.66 is used between the 5th and 6th layers, dielectric thickness 0.254mm, the 6-layer PCB board is made by stacking and mixing, with metal edging all around and semi-circular hole metallization treatment on the port.

2. The method for designing a miniaturized, broadband, 90° hybrid bridge according to claim 1, wherein: The corners of the curved routing are chamfered, and rectangular metal pieces are set near the four ports of the first stripline coupled signal routing layer and the second stripline coupled signal routing layer for grounding.

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