A broadband low-loss sum-difference amplifier integrated on a double-sided copper clad laminate and its simulation design method

Abstract

The present invention relates to a broadband low-loss sum-difference divider integrated on a double-sided copper clad laminate and a simulation design method thereof, which includes a single-layer dielectric substrate, metal layers on its upper and lower surfaces, and an aluminum bottom plate with grooves. Among them, the differential coupling metal sheets in the upper metal layer and the wide sides of the grounding metal sheets in the lower metal layer are coupled to form a differential circuit; the T-shaped metal sheet in the upper metal layer, a pair of bent stubs in the lower metal layer, and the metallized vias form a sum port power divider circuit with the aluminum bottom plate; the use of jumpers and narrow gaps is avoided. The broadband sum-difference divider of the present invention has the advantages of simple structure, low processing difficulty, low loss, more stable phase difference, better isolation, and wider bandwidth.

Description

Technical Field

[0001] The present invention belongs to the technical field of antenna microwave, and particularly relates to the design of a sum-difference divider with wide bandwidth, stable phase difference and good matching. Background Art

[0002] In a monopulse radar antenna, the sum-difference divider plays a crucial role. Through the sum and difference beams of the antenna, real-time tracking of the target is achieved. After the received electromagnetic wave signals are synthesized by the quadrant feeding network, they are sent to the sum-difference divider network. The sum-difference divider network forms a sum beam, an azimuth difference beam and an elevation difference beam, and sends them to the receiver. The position of the target is determined by processing the signals. Therefore, the electrical performance of the sum-difference divider directly affects the performance of the radar antenna, such as antenna gain, zero depth of the difference beam, and angle and distance measurement accuracy. Therefore, it is of great significance to improve the amplitude-phase consistency, sum-difference isolation and bandwidth of the sum-difference divider.

[0003] A typical sum-difference divider is called a magic T, which is a four-port device. Two of the ports are equal-amplitude ports, the third port is the sum signal port, and the fourth port is the difference signal port. When the sum signal port is fed, the two output ports output equal amplitude and in-phase; when the difference signal port is fed, the two output ports output equal amplitude and out-of-phase; good isolation is formed between the sum and difference signal ports.

[0004] The present invention adopts the Marchand balun principle. In the prior art, the designed sum-difference network uses the coupling method to generate differential signals, and often uses the coplanar coupling plus jumper method or the microstrip line-coupled slot line conversion method to achieve broadband. At present, when designing the coupling circuit of the sum-difference divider network, the coplanar coupling gap is often within 0.1 - 0.2 mm, and the electrical performance is easily affected by the processing accuracy. In addition, both of them have problems such as high loss, difficult processing, and unreasonable signal routing, and the electrical performance needs to be improved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to provide a broadband sum-difference divider based on printed circuit technology with wide bandwidth, stable phase difference, low loss, excellent performance and easy processing.

[0006] To solve the above technical problem, the technical solution adopted by the present invention is:

[0007] A broadband low-loss sum-difference divider integrated on a double-sided copper clad laminate, characterized by comprising:

[0008] A multi-layer structure stacked in sequence from top to bottom, an upper printed metal layer, a dielectric substrate, a lower printed metal layer, and an aluminum bottom plate with grooves. The upper printed metal layer is connected to the lower printed metal layer through metallized vias on the dielectric substrate;

[0009] The upper printed metal layer described above includes a T-shaped metal sheet, a differential port coupling metal sheet, and a metal sheet with a short-circuit stub; the lower printed metal layer includes a ground metal sheet, a first bent stub, and a first bent stub;

[0010] The differential port coupling metal sheet is coupled with the wide side of the ground metal sheet to form a differential microstrip circuit; the T-shaped metal sheet, the first bent stub, the first bent stub, the metallized via, and the aluminum bottom plate with a groove constitute a sum port power divider circuit; the metal sheet with a short-circuit stub and the aluminum bottom plate with a groove form a matching transmission section for sum-difference signals.

[0011] A further technical solution of the present invention: The ground metal sheet is in partial contact with the aluminum bottom plate with a groove, and is electrically connected to the first bent stub and the first bent stub.

[0012] A further technical solution of the present invention: The aluminum bottom plate with a groove has the same depression depth, and the depression position is consistent with the conductor trace of the microstrip line. The two form an air microstrip or a microstrip transmission line in the form of a dielectric substrate with a certain dielectric constant laminated with an air layer.

[0013] A further technical solution of the present invention: The ground metal sheet is disconnected in the middle, and the distance from the disconnection to the ground is 1 / 4 wavelength of the low frequency.

[0014] A further technical solution of the present invention: The upper printed metal layer further includes a short-circuit stub connected to the upper copper clad, which is connected to the metal sheet with a short-circuit stub.

[0015] A further technical solution of the present invention: The length of the metal sheet with a short-circuit stub is one wavelength of the center frequency.

[0016] A further technical solution of the present invention: The lower printed metal layer further includes a short-circuit stub connected to the lower copper clad, and the short-circuit stub connected to the lower copper clad is connected to the short-circuit stub connected to the upper copper clad through a metallized via.

[0017] A further technical solution of the present invention: The total length of the T-shaped metal sheet, the first bent stub, and the first bent stub is 1 / 4 wavelength of the low frequency.

[0018] A simulation design method for a broadband low-loss sum-difference device integrated on a double-sided copper clad laminate, characterized in that an ideal-fed differential network as described above is constructed, the gap width at the structure disconnection is taken as 4-5 mm, the length of the ideal-fed microstrip line is twice the gap width, the line width is selected according to 60-70 ohms, the length from the disconnection to the ground is 1 / 4 wavelength of the low frequency, the S parameters of the structure are extracted through full-wave simulation, and then brought into circuit software to build a circuit structure and optimize the impedance and electrical length of each section to complete the simulation design of the broadband sum-difference device network.

[0019] Application of a broadband low-loss sum-difference device integrated on a double-sided copper clad laminate, characterized in that after the received electromagnetic wave signals are synthesized by a quadrant feeding network, they are sent to the sum-difference device, and the sum-difference device forms a sum beam, an azimuth difference beam, and an elevation difference beam, which are sent to a receiver, and the determination of the target position is completed through signal processing.

[0020] The beneficial effects of the present invention are as follows: By reasonably utilizing metallized vias and an aluminum bottom plate, broadside coupling is achieved under the condition of a single-layer dielectric substrate, greatly improving the electrical performance of the sum-difference, and the phase difference bandwidth, impedance bandwidth, and isolation degree have all been greatly improved; within the 50% bandwidth, the isolation degree is greater than 40 dB, the phase difference is stable within 180°±1°, and the reflection loss is less than -20 dB; at the same time, the routing of the sum-difference signals is more reasonable, avoiding the use of jumpers, the overall structure is more planar, the processing is simpler, and the performance is more stable. Brief Description of the Drawings

[0021] The drawings are only for the purpose of illustrating specific embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference signs denote the same components.

[0022] Figure 1 It is the overall structure diagram of the broadband sum-difference device of the present invention;

[0023] Figure 2 It is the interlayer relationship diagram of the printed circuit of the broadband sum-difference device of the present invention;

[0024] Figure 3 It is the top view of the printed circuit board of the broadband sum-difference device of the present invention;

[0025] Figure 4 It is the top view of the upper and lower metal layers of the printed circuit board of the broadband sum-difference device of the present invention;

[0026] Figure 5 It is the microstrip line and via structure diagram of the broadband sum-difference device of the present invention;

[0027] Figure 6 It is the principle topology diagram of the broadband sum-difference device of the present invention;

[0028] Figure 7 It is the ideal feeding structure diagram of the differential circuit of the broadband sum-difference device of the present invention;

[0029] Figure 8 It is the impedance matching design principle topology diagram of the broadband sum-difference device of the present invention;

[0030] Figure 9 It is the port S parameters of the broadband sum-difference device of the present invention (4-port input, S42 and S43 are port power dividers, and S44 is the port reflection loss);

[0031] Figure 10The port S parameters of the broadband sum-difference divider of the present invention (input at port 1, S12 and S13 are power dividers at ports, and S11 is the port reflection loss);

[0032] Figure 11 The phase imbalance of the power divider ports when the sum port of the broadband sum-difference divider of the present invention is input;

[0033] Figure 12 The phase imbalance of the power divider ports when the difference port of the broadband sum-difference divider of the present invention is input;

[0034] Figure 13 The coupling degree between the sum and difference ports of the broadband sum-difference divider of the present invention;

[0035] Wherein, 1 - upper printed metal layer, 2 - dielectric substrate, 3 - lower printed metal layer, 4 - aluminum bottom plate with grooves, 5 - RF cable socket.

[0036] 101 - first feeding port; 102 - second feeding port; 103 - third feeding port; 104 - fourth feeding port; 105 - T-shaped metal sheet; 106 - differential coupling metal sheet; 107 - output matching section; 108 - short-circuit stub grounded upper copper clad;

[0037] 201 - dielectric plate; 202 - metallized via; 203 - screw;

[0038] 301 - grounding metal sheet; 302 - first bent stub; 303 - second bent stub; 304 - short-circuit stub grounded lower copper clad. Detailed implementation manners

[0039] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] As Figures 1-5 shown, the embodiment of the present invention provides a broadband low-loss sum-difference divider integrated on a double-sided copper clad laminate, including: printed circuit board upper layer metal 1, dielectric substrate 2, printed circuit board lower layer metal 3, aluminum bottom plate 4 with grooves, and RF cable socket 5. The upper and lower layer metal layers are respectively etched on the upper and lower surfaces of the dielectric substrate of the double-sided copper clad laminate and are connected through metallized vias. The two together with the aluminum bottom plate form the sum-difference divider network.

[0041] The material and thickness of the above-mentioned dielectric substrate 2 can be appropriately selected as needed; in this embodiment, the dielectric substrate 2 is a material with a thickness of 1 mm and a dielectric constant of 2.65; upper and lower printed metal layers 1 and 3 are covered on both sides of the dielectric substrate 2, and the upper and lower metal layers are connected by metallized vias 202 on the dielectric substrate 2. The dielectric substrate 2 is fixed on the grooved aluminum base plate 4 by 4 screws.

[0042] The upper printed metal layer 1 includes a T-shaped metal sheet 105, a differential coupling metal sheet 106, an output matching section 107, and a short-circuit stub upper-layer copper clad 108. The output matching section 107 is connected to the short-circuit stub upper-layer copper clad 108; one end of the T-shaped metal sheet 105 is provided with a fourth feeding port 104, one end of the differential coupling metal sheet 106 is provided with a first feeding port 101, and one end of the output matching section 107 is provided with a second feeding port 102 and a third feeding port 103; the first feeding port 101, the second feeding port 102, the third feeding port 103, and the fourth feeding port 104 are all connected to the RF cable socket 5 for bottom feeding.

[0043] Preferably, the T-shaped metal sheet 105 is of a T-shaped structure and is located on the center line of the dielectric substrate 2; the output matching section 107 is of a microstrip line structure, and the number is 2, symmetrically distributed on both sides of the center line; the short-circuit stub upper-layer copper clad 108 is of a rectangular structure, and the number is 2, symmetrically distributed on both sides of the center line.

[0044] The lower printed metal layer 3 includes a grounding metal sheet 301, a first bent stub 302, a second bent stub 303, and a short-circuit stub lower-layer copper clad 304. The first bent stub 302 and the second bent stub 303 are connected to the trapezoidal metal sheet of the grounding metal sheet 301 through an equal-width metal sheet.

[0045] Preferably, the grounding metal sheet 301 is provided with a groove structure in the middle; the first bent stub 302 and the second bent stub 303 are symmetrically distributed on both sides of the center line of the dielectric substrate 2; the short-circuit stub lower-layer copper clad 304 is of a rectangular structure, and the number is 2, symmetrically distributed on both sides of the center line.

[0046] Specifically, the differential coupling metal sheet 106 in the upper metal layer 1 is coupled with the wide side of the grounding metal sheet 301 in the lower metal layer 3 to form a differential circuit; the distance from the disconnection point of the lower metal layer 301 to the grounding point (the connection point of the equal-width metal sheet and the trapezoidal metal sheet, that is, the decomposition line where the width of the disconnection point starts to change) is approximately 1 / 4 wavelength of the low frequency. The gap at the disconnection point can be taken as 1-5 mm, which reduces the requirement for processing accuracy. Due to the wide-side coupling, the electrical performance of the balun can be greatly improved.

[0047] Preferably, the projection of the differential coupling metal sheet 106 in the upper metal layer 1 is located on the equal-width metal sheet in the lower metal layer 3.

[0048] Specifically, the T-shaped metal sheet 105 in the upper metal layer, a pair of bent branches 302 and 303 in the lower metal layer, and the metallized vias 202 and the aluminum bottom plate 4 form a sum port power divider circuit, with a length of about 1 / 4 wavelength of the center frequency; the output matching section 107 in the upper metal layer and the aluminum bottom plate 4 form a matching transmission microstrip line for the two output ports, with a length of about one wavelength of the center frequency; the two and the above-mentioned differential circuit form a complete sum-difference network through the metallized vias 202, and improve the sharing ratio of the sum-difference signal circuit, avoiding the introduction of jumpers.

[0049] The recess of the grooved aluminum bottom plate 4 serves as the ground of the microstrip transmission line. The position of the recess is consistent with the conductor trace of the microstrip line, and the two form a microstrip transmission line in the form of an air microstrip or a dielectric substrate with a certain dielectric constant laminated with an air layer. The recess depth can be selected according to the thickness requirements of the microstrip line. In this embodiment, it is selected to be the same as the thickness of the dielectric substrate 2, which is 1 mm. The air layer serves as a partial dielectric substrate of the microstrip line, reducing the number of dielectric substrate layers and transmission losses.

[0050] Further, the transmission sections of the first feeding port 101, the second feeding port 102, the third feeding port 103, and the fourth feeding port 104 are all located in the upper metal layer 1, which is beneficial for the radio frequency cable to perform bottom feeding.

[0051] Further, the upper and lower metal layers realize the wide-side coupling of the microstrip line in the differential network, the short-circuit grounding of the matching branches of the output matching section, and the probe to perform bottom feeding through the metallized vias.

[0052] Further, the disconnection in the lower metal layer is the common transmission section existing in the sum port power divider circuit and the differential circuit except for the matching transmission microstrip line of the two output ports.

[0053] Further, the output matching section in the upper metal layer and the aluminum bottom plate form a matching transmission microstrip line for the two output ports, and the structures of the left and right output ports are exactly the same.

[0054] Further, referring to Figure 6 as shown, each transmission line of the broadband sum-difference network should correspond to Figure 6 the impedance transformation section in the equivalent circuit. The thickness of the transmission line should be optimized according to the thickness of the dielectric substrate 2, the depth of the recess of the aluminum bottom plate 4, and the electrical performance requirements of each port to obtain the impedance and electrical length of each transmission line.

[0055] Further, for the efficient design of the broadband sum-difference network, referring to Figures 7-8 as shown, the design idea is introduced. First, construct as Figure 7The ideal-fed differential network shown has a slot width at the break that can be set to an appropriate value according to the operating frequency band. In this embodiment, the slot width is taken as 4 - 5 mm. The length of the ideal-fed microstrip line is approximately twice the slot width, and the line width is selected according to 60 - 70 ohms. The length from the break to the ground is approximately 1 / 4 wavelength of the low frequency. Through full-wave simulation, the S-parameters of this structure are extracted and brought into the circuit software to build the circuit structure as shown in Figure 8 to complete the simulation design of the broadband sum-difference network by optimizing the impedance and electrical length of each section.

[0056] The circuit structure adopted in the embodiment of the present invention greatly improves the electrical performance of the sum-difference device under the condition of a single-layer dielectric substrate. Within a 50% bandwidth, the isolation is greater than 40 dB, the phase difference is stable within 180° ± 1°, and the reflection losses at the sum and difference ports are close to -20 dB. At the same time, the routing of the sum and difference signals is more reasonable, avoiding the use of jumpers, the overall structure is more planar, easier to process and install, and the performance is more stable.

[0057] Refer to Figures 9-13 , and the reflection coefficients of each port and the transmission coefficients between ports of the sum-difference device in the above embodiment are simulated and calculated using simulation software. The simulation results are as follows:

[0058] Figures 9-10 shows the characteristics of the S-parameters varying with the operating frequency when the sum and difference ports of the sum-difference device in the embodiment are fed separately. It can be seen from the figure that this sum-difference device can achieve equal power splitting of 50% (1.5 GHz - 2.5 GHz), low reflection loss (≤ -20 dB), and low in-band loss of only about 0.3 dB.

[0059] Figures 11-12 shows the characteristics of the phase difference between the two output ports varying with the operating frequency when the sum and difference ports of the sum-difference device in the embodiment are fed separately. It can be seen from the figure that this sum-difference device can achieve a phase difference offset of ±1°.

[0060] Figure 13 shows the characteristics of the coupling degree between the sum and difference ports of the sum-difference device in the embodiment varying with the operating frequency. It can be seen from the figure that the coupling degree of this antenna is low, far lower than that of the sum-difference device ports in the past.

[0061] The simulation results show that this sum-difference device can achieve stable phase difference, high isolation, and low loss within a 50% bandwidth, and at the same time, the input impedance matching of each port is excellent.

[0062] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A broadband low-loss sum-difference device integrated on a double-sided copper clad laminate, characterized in that, Comprising: A multi-layer structure stacked layer by layer from top to bottom, including an upper printed metal layer (1), a dielectric substrate (2), a lower printed metal layer (3), and an aluminum bottom plate (4) with grooves. The upper printed metal layer (1) and the lower printed metal layer (3) are connected through metallized vias on the dielectric substrate (2). The upper printed metal layer (1) includes a T-shaped metal sheet (105), a differential-port coupling metal sheet (106), and a metal sheet with a short-circuit stub (107). One end of the T-shaped metal sheet (105) is provided with a fourth feeding port (104), one end of the differential-port coupling metal sheet (106) is provided with a first feeding port (101), and one end of the metal sheet with a short-circuit stub (107) is provided with a second feeding port (102) and a third feeding port (103). The first feeding port (101), the second feeding port (102), the third feeding port (103), and the fourth feeding port (104) are all connected to a radio frequency cable socket (5) for bottom feeding. The lower printed metal layer (3) includes a grounding metal sheet (301), a first bent stub (302), and a second bent stub (303). The grounding metal sheet (301) is in partial contact with the aluminum bottom plate (4) with grooves and is electrically connected to the first bent stub (302) and the second bent stub (303). The differential-port coupling metal sheet (106) and the grounding metal sheet (301) are coupled by their wide sides to form a differential microstrip circuit. The T-shaped metal sheet (105), the first bent stub (302), the second bent stub (303), the metallized vias, and the aluminum bottom plate (4) with grooves constitute a sum-port power divider circuit. The metal sheet with a short-circuit stub (107) and the aluminum bottom plate (4) with grooves form a matching transmission section for sum and difference signals.

2. The broadband low-loss sum-difference device integrated on a double-sided copper clad laminate according to claim 1, characterized in that, The aluminum bottom plate (4) with grooves has the same depression depth, and the depression position is consistent with the conductor trace of the microstrip line. The two form an air microstrip or a microstrip transmission line in the form of a dielectric substrate with a certain dielectric constant laminated with an air layer.

3. The broadband low-loss sum-difference device integrated on a double-sided copper clad laminate according to claim 1, characterized in that, The grounding metal sheet (301) is disconnected in the middle, and the distance from the disconnection point to the grounding point is 1 / 4 wavelength of the low frequency.

4. The broadband low-loss sum-difference device integrated on a double-sided copper clad laminate according to claim 1, characterized in that, The upper printed metal layer (1) further includes a short-circuit stub grounded upper copper clad (108), which is connected to the metal sheet with a short-circuit stub (107).

5. The broadband low-loss sum-difference device integrated on a double-sided copper clad laminate according to claim 4, characterized in that, The lower printed metal layer (3) further includes a short-circuit stub grounded lower copper clad (304), and the short-circuit stub grounded lower copper clad (304) is connected to the short-circuit stub grounded upper copper clad (108) through a metallized via.

6. The broadband low-loss sum-difference device integrated on a double-sided copper clad laminate according to claim 4, characterized in that, The length of the metal sheet with a short-circuit stub (107) is one wavelength of the center frequency.

7. The broadband low-loss sum-difference device integrated on a double-sided copper clad laminate according to claim 1, characterized in that, The total length of the T-shaped metal sheet (105), the first bent stub (302), and the second bent stub (303) is 1 / 4 wavelength of the low frequency.

8. A simulation design method for a broadband low-loss sum-difference device integrated on a double-sided copper clad laminate, characterized in that, Construct the broadband low-loss sum-difference device integrated on the double-sided copper clad laminate. The gap width at the structural disconnection is 4 - 5 mm. The ideal length of the feeding microstrip line is twice the gap width. The line width is selected according to 60 - 70 ohms. The length from the disconnection to the ground is 1 / 4 wavelength of the low frequency. Through full-wave simulation, extract the S-parameters of this structure, bring them into the circuit software, build the circuit structure, optimize the impedance and electrical length of each section, and complete the simulation design of the broadband sum-difference device network.

9. An application of the broadband low-loss sum-difference device integrated on a double-sided copper clad laminate according to any one of claims 1-7, characterized in that, The received electromagnetic wave signals are synthesized by the quadrant feeding network and sent to the sum-difference device. The sum-difference device forms a sum beam, an azimuth difference beam, and an elevation difference beam, which are sent to the receiver. The target position is determined by processing the signals.

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