Combining broadband power divider with frequency selection function and design method thereof

Abstract

This invention discloses a frequency-selective broadband power divider and its design method. The method includes designing the power divider; designing a first frequency-selective filter and a second frequency-selective filter; connecting the first and second frequency-selective filters to the power divider, wherein during connection, resonant microstrip transmission lines near the output terminals of the first and second frequency-selective filters are deleted, and a microstrip transmission line is added between the first and second frequency-selective filters and the power divider to obtain a frequency-selective broadband power divider model; the frequency-selective broadband power divider model is debugged and simulated to obtain the final frequency-selective broadband power divider model. This invention reduces debugging difficulty and decreases circuit size and losses by using the added microstrip transmission line for filter resonance and impedance matching between the filter and the power divider.

Description

Technical Field

[0001] This invention belongs to the field of power divider design technology, and particularly relates to a combined broadband power divider with frequency selection function and its design method. Background Technology

[0002] With the advancement of technology, wireless communication and radar systems have been more widely used, placing increasingly higher demands on radio frequency (RF) circuits. In RF microwave circuits, a power divider is a device that splits signal power into two or more paths. Depending on the power output at the port, they can be classified as equal-division or unequal-division power dividers. A power divider used in reverse is a combiner. Ultra-wideband (UWB) technology, due to its superior performance such as good concealment, high transmission rate, and large spatial capacity, has broad application prospects in microwave systems, thus creating a demand for UWB power dividers. Furthermore, with increasing demand, many RF circuits also require frequency selection within the bandwidth of UWB power dividers.

[0003] In conventional design, to meet the requirement of frequency selection, combining, and then power splitting within the operating bandwidth of the power divider (i.e., a frequency-selective combining broadband power divider), the input terminals of two identical power dividers that meet the usage requirements are generally connected together, and then a frequency-selective filter is connected at the front end of the combiner or the back end of the power divider in the circuit. This design can indeed meet the requirements, but it will cause the following problems:

[0004] (1) Excessive loss: Due to the basic losses of the power divider (greater than 3dB) and combiner (greater than 3dB), plus the loss of the filter, the total system loss cannot be less than 6dB.

[0005] (2) Too large: Increased the size of filter + combiner + power divider;

[0006] (3) Impedance matching is difficult to debug. The filter, power divider and combiner need to be debugged separately and then combined for adjustment. Summary of the Invention

[0007] The purpose of this invention is to provide a frequency-selective broadband power divider and its design method to solve the problems of excessive loss, excessive size and difficulty in impedance matching of traditional frequency-selective broadband power dividers.

[0008] This invention solves the above-mentioned technical problems through the following technical solution: a design method for a combined broadband power divider with frequency selection function, the design method comprising the following steps:

[0009] Design a power divider based on the operating frequency range and passband bandwidth requirements;

[0010] Design a first frequency selective filter and a second frequency selective filter to ensure good performance within the operating frequency range;

[0011] The output terminals of the first frequency selective filter and the second frequency selective filter are connected to the input terminal of the power divider. During the connection, the resonant microstrip transmission line near the output terminal of the first frequency selective filter is deleted, the resonant microstrip transmission line near the output terminal of the second frequency selective filter is deleted, and a microstrip transmission line in parallel with the connection point is added between the output terminals of the first and second frequency selective filters and the input terminal of the power divider to obtain the frequency selective combining broadband power divider model.

[0012] The frequency selective combiner broadband power divider model was debugged and simulated to obtain the final frequency selective combiner broadband power divider model.

[0013] Furthermore, the specific implementation process of designing the power divider based on the operating frequency range and passband bandwidth requirements includes:

[0014] Determine the number of sections of the impedance transformation line, and use the even-mode circuit design method to determine the impedance and electrical length of each section of the impedance transformation line;

[0015] The value of the isolation resistor to be added for each impedance transformation line is determined by using the odd-mode circuit design method;

[0016] Construct a power divider circuit schematic, substitute the impedance and electrical length of each impedance transformation line and the resistance value of the isolation resistor into the power divider circuit schematic, and verify the power divider circuit schematic.

[0017] Once the verification is successful, the length and width of the corresponding quarter-wavelength impedance transformation line are calculated based on the impedance and electrical length of each section of the impedance transformation line.

[0018] Construct the power divider layout diagram based on the power divider circuit schematic, the line length and line width of the quarter-wavelength impedance transformation line.

[0019] Furthermore, the specific implementation process for determining the impedance and electrical length of each impedance transformation line using the even-mode circuit design method is as follows:

[0020] Construct an even-mode circuit consisting of n impedance transformation lines connected in series, and add input and output ports to the even-mode circuit;

[0021] Set the impedance of the input and output ports, and set the impedance and electrical length of each impedance transformation line as variables;

[0022] Add input and output standing wave curves, and set the optimization target;

[0023] Calculate the input standing wave curve and output standing wave curve of the even-mode circuit. When the input standing wave curve and output standing wave curve of the even-mode circuit reach the optimization target, record the impedance and electrical length of each impedance transformation line.

[0024] Furthermore, the specific implementation process for determining the value of the isolation resistor to be added to each impedance transformation line using the odd-mode circuit design method is as follows:

[0025] Remove the input port from the even-mode circuit, and add isolation resistors between adjacent impedance transformation lines and between the last impedance transformation line and the output port. Connect the unconnected end of the first impedance transformation line and each isolation resistor to the ground port to obtain the odd-mode circuit.

[0026] Substitute the impedance and electrical length of each impedance transformation line into the odd-mode circuit;

[0027] Add input and output standing wave curves, and set the optimization target;

[0028] Calculate the input standing wave (SWR) curve and output standing wave (SWR) curve of the odd-mode circuit. When the input SWR curve and output SWR curve of the odd-mode circuit reach the optimization target, record the resistance value of each isolation resistor.

[0029] Furthermore, the specific implementation process for designing the first frequency-selective filter or the second frequency-selective filter is as follows:

[0030] Determine the design specifications for the first frequency selective filter or the second frequency selective filter;

[0031] Set the parameters in iFilter Filter Synthesis in AWR software Wizards according to the design specifications;

[0032] The microstrip circuit schematic of the filter, as well as loss and standing wave calculation curves, are automatically generated based on the set parameters.

[0033] When the loss and standing wave ratio meet the requirements, generate the microstrip circuit layout of the filter.

[0034] Furthermore, the specific implementation process for debugging the frequency-selective combined broadband power divider model is as follows:

[0035] Add input VSWR curve, output VSWR curve, loss curve, and isolation curve;

[0036] All parameters of the frequency-selective combined broadband power divider model are set as variables;

[0037] Calculate the standing wave ratio, loss, and isolation of the frequency-selective broadband power divider model;

[0038] When the standing wave ratio, loss, and isolation all meet the requirements, the parameters of the frequency-selective combined broadband power divider model are determined.

[0039] Furthermore, the specific implementation process for simulating the frequency-selective combined broadband power divider model is as follows:

[0040] The debugged frequency-selective combined broadband power divider model was imported into HFSS for electromagnetic simulation calculations, and the parameters were optimized.

[0041] When the simulation output meets the design requirements and the isolation meets the requirements, the design of the frequency selection combiner broadband power divider model is completed.

[0042] Furthermore, the design method also includes: drawing the PCB based on the final frequency selection combined broadband power divider model, sending the PCB manufacturing file to the PCB manufacturer for PCB processing, and obtaining the designed power divider physical object.

[0043] Based on the same concept, the present invention also provides a combined broadband power divider with frequency selection function, wherein the combined broadband power divider is designed using the design method described above.

[0044] Beneficial effects

[0045] Compared with the prior art, the advantages of the present invention are as follows:

[0046] This invention combines a frequency-selective filter and a power divider through a direct connection. The last stage resonant microstrip transmission line of the frequency-selective filter is removed, and a microstrip transmission line is added at the common connection point. This microstrip transmission line at the common connection point is used to adjust the resonance of the frequency-selective filter and the impedance at the connection between the filter and the power divider, achieving impedance matching. This achieves the effect of combining without using a combiner, reducing the design size. Compared to the traditional method of debugging the filter and power divider first, and then re-tuning them after connection, this invention first idealizes the design of the filter and power divider, eliminating the need for debugging. After connection, impedance matching is achieved by debugging the filter and power divider as a whole, reducing the debugging difficulty.

[0047] This invention achieves the effect of frequency selection, combining, and power splitting, while also reducing the losses that would otherwise be introduced by two power dividers compared to the ordinary combining and power splitting scheme, and reducing the design size by using only one power divider. Attached Figure Description

[0048] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a flowchart of the design method in an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of the even-mode circuit in an embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram of the odd-mode circuit in an embodiment of the present invention.

[0052] Figure 4 This is a schematic diagram of the power divider circuit in an embodiment of the present invention;

[0053] Figure 5 This is a schematic diagram of the first quarter-wavelength impedance transformation line in an embodiment of the present invention;

[0054] Figure 6 This is a schematic diagram of the quarter-wavelength impedance transformation line in the second section of this embodiment of the invention;

[0055] Figure 7 This is a layout diagram of the power divider in an embodiment of the present invention;

[0056] Figure 8 This is a schematic diagram of the first frequency selection filter in an embodiment of the present invention;

[0057] Figure 9 This is a schematic diagram of the second frequency selection filter in an embodiment of the present invention;

[0058] Figure 10 This is a schematic diagram of the connection between the filter and the power divider in an embodiment of the present invention;

[0059] Figure 11 This is the frequency selection combined broadband power divider model after docking in this embodiment of the invention;

[0060] Figure 12 This is a standing wave curve diagram during debugging in an embodiment of the present invention;

[0061] Figure 13 This is a loss curve during debugging in an embodiment of the present invention;

[0062] Figure 14 This is an isolation curve during debugging in an embodiment of the present invention;

[0063] Figure 15This is a schematic diagram of a frequency selection combiner broadband power divider model in HFSS software in an embodiment of the present invention;

[0064] Figure 16 This is a standing wave curve diagram from the simulation in this embodiment of the invention;

[0065] Figure 17 This is a loss curve during simulation in an embodiment of the present invention;

[0066] Figure 18 This is an isolation curve during simulation in an embodiment of the present invention;

[0067] Figure 19 This is the actual test result of the power divider when the test signal is input from the first frequency selection filter in the embodiment of the present invention;

[0068] Figure 20 This is the actual test result of the power divider when the test signal is input from the second frequency selection filter in the embodiment of the present invention;

[0069] Figure 21 These are the isolation test results of the actual power divider in the embodiments of the present invention. Detailed Implementation

[0070] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] The technical solutions of this application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0072] The meanings of the characters are explained in Table 1:

[0073] Table 1 Character Meanings

[0074]

[0075] like Figure 1 As shown in the figure, the present invention provides a design method for a combined broadband power divider with frequency selection function, which includes the following steps:

[0076] Step 1: Design the power divider according to the operating frequency range and passband bandwidth requirements.

[0077] This embodiment utilizes AWR software to design a broadband Willkinson power divider, ensuring good performance within the 1500–7240MHz range. The specific implementation process of designing the power divider based on the operating frequency range and passband bandwidth requirements includes:

[0078] Step 1.1: Determine the number of sections of the impedance transformation line, and use the even-mode circuit design method to determine the impedance and electrical length of each section of the impedance transformation line.

[0079] like Figure 2 As shown, a new circuit schematic is created in AWR software, using 6 TLIN sections connected in series, numbered TL1 to TL6 (i.e., 6 impedance transformation lines are used in this embodiment). The minimum frequency F1 of the operating frequency range is set to 1500MHz, the minimum frequency F2 of the operating frequency range is set to 7240MHz, and the center frequency F0 = (F1*F2)^0.5. The impedance parameter Z and electrical length parameter P of each TLIN section are set as variables to create a 6th-order circuit, and input and output ports are added.

[0080] Set the input port impedance to 100Ω and the output port impedance to 50Ω. Set the impedance parameter variable Z for the six TLIN sections from input to output to Z1 to Z6, and the electrical length parameter variable P to P1 to P6. In AWR software, create new charts and add curves S11 (input VSWR curve of the input port) and S22 (output VSWR curve of the output port). Use AWR's automatic optimization function, setting the optimization target: S11 and S22 ≤ -25dB in the 1500–7240MHz range. Automatically optimize and calculate the S11 and S22 curves of the circuit in the 1000–8000MHz range (the calculation results must cover the entire operating frequency range). The calculation stops when both S11 and S22 curves reach the optimization target. Record the values ​​of the impedance parameters Z1–Z6 and the electrical length parameters P1–P6.

[0081] Step 1.2: Use the odd-mode circuit design method to determine the value of the isolation resistor that needs to be added to each impedance transformation line.

[0082] like Figure 3As shown, create a new circuit schematic in AWR software, using 6 TLIN modules connected in series, numbered TL7 to TL12. Substitute the impedance parameters Z1 to Z6 and electrical length parameters P1 to P6 obtained in step 1.1 into TL7 to TL12. Add a port (i.e., output port) to the TLIN terminal corresponding to TL12, and set the port impedance to 50Ω. Add an isolation resistor between the TLIN terminals corresponding to TL7 and TL8, and set the resistance value of the isolation resistor to the variable R1. Similarly, add an isolation resistor to TL8 and TL9, TL9 and TL10, TL10 and TL11, TL11 and TL12, and TL12 and the output port, and set the resistance values ​​of the isolation resistors to the variables R2 to R6. Add a ground port, and connect one end of TL7 (not connected to TL8) and all isolation resistors to the ground port.

[0083] Set the minimum operating frequency F1 to 1500MHz, the minimum operating frequency F2 to 7240MHz, and the center frequency F0 = (F1*F2)^0.5. In AWR software, create a new chart and add curves S11 and S22. Use AWR software's automatic optimization function and set the optimization target: S11 and S22 ≤ -25dB in the range of 1500 to 7240MHz. Automatically optimize and calculate the S11 and S22 curves of this circuit in the range of 1000 to 8000MHz (the calculation results must cover the entire operating frequency range). The calculation stops when both S11 and S22 curves reach the optimization target. Record the values ​​of variables R1 to R6.

[0084] In this embodiment, the input port can be deleted from the even-mode circuit, and isolation resistors can be added between adjacent impedance transformation lines and between the last impedance transformation line (i.e., TL6) and the output port. The unconnected end of the first impedance transformation line (i.e., TL1) and each isolation resistor can be connected to the ground port. Then, the impedance and electrical length of each impedance transformation line obtained in step 1.1 can be substituted into this circuit.

[0085] Step 1.3: Construct the circuit schematic of the power divider, substitute the impedance and electrical length of each impedance transformation line and the resistance value of the isolation resistor into the circuit schematic of the power divider, and verify the circuit schematic of the power divider.

[0086] like Figure 4As shown, create a new circuit schematic in AWR software, using six TLIN strings connected in series, numbered TL1 to TL6. Substitute the impedance parameters Z1 to Z6 and electrical length parameters P1 to P6 obtained in step 1.1 into TL1 to TL6. Then, use six more TLIN strings connected in series, numbered TL7 to TL12. Similarly, substitute the impedance parameters Z1 to Z6 and electrical length parameters P1 to P6 obtained in step 1.1 into TL7 to TL12, making TL1 to TL6 parallel and aligned with TL7 to TL12. Use a TLIN string numbered TL13, setting its impedance parameter Z to 50Ω and electrical length parameter P to 45°. Connect one end of TL13 to the parallel TL1 and TL7, and add input port 1 to the other end of TL13, setting the impedance of input port 1 to 50Ω. Add a TLIN string numbered TL14 after TL6. TLIN, TL14 and TL6 are connected in series. The impedance parameter Z of TL14 is set to 50Ω and the electrical length parameter P is set to 45°. Output port 2 is added to the other end of TL14, and the impedance of output port 2 is set to 50Ω. A TLIN numbered TL15 is added after TL12. TL15 is connected in series with TL12. The impedance parameter Z of TL15 is set to 50Ω and the electrical length parameter P is set to 45°. Output port 3 is added to the other end of TL15, and the impedance of output port 3 is set to 50Ω. An isolation resistor R1 is connected in parallel between TL1 and TL7. Similarly, an isolation resistor R2, R3, R4, R5, and R6 are connected in parallel between TL2 and TL8, TL3 and TL9, TL4 and TL10, TL5 and TL11, and TL6 and TL12, respectively. The resistance values ​​of isolation resistors R1 to R6 obtained in step 1.2 are substituted into the newly created R1 to R6.

[0087] The minimum operating frequency range F1 is set to 1500MHz, the minimum operating frequency range F2 is set to 7240MHz, and the center frequency F0 = (F1*F2)^0.5. In the AWR software, create new charts and add curves S11 (input VSWR curve of input port 1), S22 (output VSWR curve of output port 2), S33 (output VSWR curve of output port 3), S21 (loss curve from input port 1 to output port 2), and S31 (loss curve from input port 1 to output port 3). Using the automatic optimization function of AWR software, the S11, S22, S33, S21, and S31 curves of the circuit in the 1000–8000MHz range (the calculation results must cover the entire operating frequency range) were automatically optimized and calculated. The calculation stopped when the S11, S22, and S33 curves were all less than -25dB in the 1500–7240MHz range, and the S21 and S31 curves were both greater than -3.1dB in the 1500–7240MHz range. This indicates that the power divider circuit schematic has achieved good loss and standing wave ratio effects, and the verification is successful.

[0088] Step 1.4: After verification, calculate the length and width of the corresponding quarter-wavelength impedance transformation line based on the impedance and electrical length of each section of the impedance transformation line.

[0089] The TXLINE tool in AWR software was used to calculate the length and width of the quarter-wavelength impedance transformation line. In this embodiment, the substrate parameters were set according to the Rogers 5880 board parameters: board thickness H was set to 0.508 mm, microstrip thickness T was set to 0.035 mm, dielectric constant was set to 2.2, loss tangent was set to 0.0009, and frequency was set to 3.295 GHz. Fill in 50 and 45 into Impedance and Electrical Length respectively to calculate the line width W and line length L, and record their specific values. The line width W and line length L are the line width and line length of the 50Ω impedance transformation line. Fill in Z1 and P1 into Impedance and Electrical Length respectively to calculate the line width W1 and line length L1, and record their specific values. These are the line width and line length of the first quarter-wavelength impedance transformation line of the Wilkinson power divider. Similarly, obtain the line widths W2 to W6 and line lengths L2 to L6 of the remaining five quarter-wavelength impedance transformation lines, and record their values.

[0090] Step 1.5: Construct the power divider layout diagram based on the power divider circuit schematic and the length and width of the quarter-wavelength impedance transformation line.

[0091] Create a new circuit schematic in AWR software, add a substrate MSUB, and set the substrate parameters according to the Rogers5880 board parameters, specifically: dielectric constant Er = 2.2, board thickness H = 0.508mm, microstrip thickness T = 0.035mm, and loss factor Tand = 0.0009.

[0092] Add input port 1, assuming its impedance is 50Ω. Connect a segment of MLIN labeled TL26 to input port 1. Set the linewidth of TL26 to 2mm based on the linewidth of the first quarter-wavelength impedance transformation line obtained in step 1.4 (i.e., the linewidth of the 50Ω impedance transformation line). Add a three-port connector labeled MTEE$ (MT5). Add a segment of MLIN1, connecting one end of MLIN1 to MT5 and the other end to the first port of the four-port double-section parallel microstrip transmission line MCLIN1. Add a two-port device MUBEND1, connecting its two ports to the second and third ports of MCLIN1, respectively. Add a two-port device MBEND90X1, connecting it to the fourth port of MCLIN1. Add a segment of MLIN3, connecting it in series with both MTEE$1 and MBEND90X1. Let the linewidth of MLIN1, MCLIN1, MUBEND1, MBEND90X1, and MLIN3 all be W1. Let half the linewidth of MT5 plus the line length of MLIN1, MCLIN1, MUBEND1, MBEND90X1, MLIN3, and MTEE$1 equal L1. This completes the construction of one side of the quarter-wavelength impedance transformation line. Similarly, build a completely symmetrical quarter-wavelength impedance transformation line on the other side. The two completely symmetrical quarter-wavelength impedance transformation lines constitute the first section of the quarter-wavelength impedance transformation line (numbered 1). Figure 5 As shown. Add an isolation resistor between MTEE$1 and MTEE$2, with a resistance value of R1.

[0093] Add an MLIN5 device and an MLIN7 device. Add a 2-port MBEND90X3 device and connect the MLIN5 and MLIN7 in series using the MBEND90X3. Add a 4-port dual-section parallel microstrip transmission line device MCLIN3, with the first port of MCLIN3 connected to MLIN7. Add a 2-port MUBEND3 device, with the two ports of MUBEND3 connected to the second and third ports of MCLIN3, respectively. Add a 2-port MBEND90X5 device, with the MBEND90X5 connected to the fourth port of MCLIN3. Add an MLIN9 device, with the MLIN9 connected in series with the MTEE$3 device and the MBEND90X5. Assume the linewidth of devices MLIN5, MBEND90X3, MLIN7, MCLIN3, MUBEND3, MBEND90X5, MLIN9, and MTEE$3 is W2, and the sum of their line lengths is L2. This completes the construction of one quarter-wavelength impedance transformation line. Similarly, construct a perfectly symmetrical quarter-wavelength impedance transformation line on the other side. The two perfectly symmetrical quarter-wavelength impedance transformation lines together constitute the second section of the quarter-wavelength impedance transformation line (numbered 2). Figure 6 As shown. Add an isolation resistor between MTEE$3 and MTEE$4, with a resistance value of R2.

[0094] Similar to the construction of the quarter-wavelength impedance transformation line in Section 2, construct the third quarter-wavelength impedance transformation line with a linewidth of W3 and a bus length of L3, designated as number 3, and add an isolation resistor with a value of R3; construct the fourth quarter-wavelength impedance transformation line with a linewidth of W4 and a bus length of L4, designated as number 4, and add an isolation resistor with a value of R4; construct the fifth quarter-wavelength impedance transformation line with a linewidth of W5 and a bus length of L5, designated as number 5, and add an isolation resistor with a value of R5; construct the sixth quarter-wavelength impedance transformation line with a linewidth of W6 and a bus length of L6, designated as number 6, and add an isolation resistor with a value of R6. Following the quarter-wavelength impedance transformation lines in Section 6, construct two 50Ω impedance lines with a line width of W and a length of 2mm. Add output port 2 (denoted as TL27) and output port 3 at the rear end, assuming both ports have an impedance of 50Ω. Connect an MLIN segment numbered TL27 to output port 2 and an MLIN segment numbered TL28 to output port 3. Finally, connect all the aforementioned quarter-wavelength impedance transformation lines in sequence to obtain the power divider layout diagram, as shown below. Figure 7As shown. The length and width of each line segment in the power divider layout diagram are consistent with the length and width of the quarter-wavelength impedance transformation line calculated in step 1.4, and the resistance value of the isolation resistor is consistent with the resistance value of the isolation resistor obtained in step 1.2.

[0095] In the AWR software, create new charts and add curves S11, S22, and S33. Calculate the S11, S22, and S33 curves for this circuit in the 1000–8000MHz range. When the S11, S22, and S33 curves are all less than -25dB in the 1500–7240MHz range, it indicates that the input and output standing wave ratios meet the requirements. In the AWR software, create new charts and add curves S21 and S31. Calculate the S21 and S31 curves for this circuit in the 1000–8000MHz range. When the S21 and S31 curves are both greater than -3.1dB in the 1500–7240MHz range, it indicates that the loss meets the requirements. In the AWR software, create new charts and add curve S32. Calculate the S32 curve for this circuit in the 1000–8000MHz range. When the S32 curve is all less than -20dB in the 1500–7240MHz range, it indicates that the isolation meets the requirements.

[0096] If any curve does not meet the requirements, adjust the length and width of the microstrip transmission line and recalculate until each curve meets the corresponding requirements.

[0097] Step 2: Design a first frequency selective filter to ensure good performance at the lowest frequency point of the operating frequency range; design a second frequency selective filter to ensure good performance at the highest frequency band of the operating frequency range.

[0098] This embodiment utilizes the design wizard function of AWR software to design two frequency selective filters. The first frequency selective filter performs well at a point frequency of 1500MHz, and the second frequency selective filter performs well in the 6840-7240MHz range. The operating frequency range is 1500-7240MHz.

[0099] For the design of the first frequency selection filter, open the iFilter Filter Synthesis section in the Wizards of AWR software, click Design, select the filter type, choose Lowpass from the Passband menu, Microstrip from the Realization menu, and Optimum Distributed Lowpass Filter from the Main Filter Type menu, then click OK; in the pop-up window, enter 7 in Degree and 1500 in Fp [MHz], click Design Options from the Design Control menu, select Technology in the pop-up window, set Substrate Er to 2.2, Height (H) [mm] to 0.508, Cond. Thickness (t) [mm] to 0.035, and Loss Tangent (tanD) to 0.0009 in the Microstrip menu, then click the microstrip transmission line icon to view the approximate layout, and finally click Generate. In the Design dialog box, click OK to automatically generate the microstrip circuit schematic and loss and VSWR calculation curves for a microstrip low-pass filter with a cutoff frequency of 1500MHz. At the 1500MHz frequency, the loss is greater than -0.5 and the VSWR is less than -20, both meeting the requirements. Then click the View Layout icon to generate the microstrip circuit layout, which gives you the microstrip circuit layout for the first frequency selection filter. Figure 8 As shown.

[0100] For the design of the second frequency selective filter, open the iFilter Filter Synthesis section in the Wizards of AWR software, click Design, select the filter type, choose Lowpass from the Passband menu, Microstrip from the Realization menu, and Optimum Distributed Lowpass Filter from the Main Filter Type menu, then click OK; in the pop-up window, enter 9 in Degree and 7040 in Fp [MHz], click Design Options from the Design Control menu, select Technology in the pop-up window, set Substrate Er to 2.2, Height (H) [mm] to 0.508, Cond. Thickness (t) [mm] to 0.035, and Loss Tangent (tanD) to 0.0009 in the Microstrip menu, then click the microstrip transmission line icon to view the approximate layout, and finally click Generate. In the Design dialog box, click OK to automatically generate the microstrip circuit schematic and loss and VSWR calculation curves for a microstrip low-pass filter with a cutoff frequency of 7240MHz. The loss is greater than -0.5 and the VSWR is less than -20 in the 6840–7240MHz range, meeting the requirements. Then click the View Layout icon to generate the microstrip circuit layout, which gives you the microstrip circuit layout for the second frequency-selective filter. Figure 9 As shown.

[0101] Figure 8 and 9 The TL25 lines in the filter are microstrip transmission lines that play a resonant role in the filter. They need to be removed when the filter is connected to the power divider.

[0102] Step 3: Connect the first frequency selective filter and the second frequency selective filter designed in Step 2 with the power divider designed in Step 1.

[0103] The outputs of the first frequency selective filter and the second frequency selective filter are connected to the input of the power divider. During the connection, the resonant microstrip transmission line near the output of the first frequency selective filter and the resonant microstrip transmission line near the output of the second frequency selective filter are removed. A microstrip transmission line connected in parallel with the connection point is added between the outputs of the first and second frequency selective filters and the input of the power divider to obtain the frequency selective combined broadband power divider model.

[0104] During the connection process, delete TL25 from the first frequency selection filter and also delete MT1 (after deleting TL25, the MTEE three-port connector is no longer needed). Directly connect TL7 and TL8 (e.g., Figure 8 and Figure 10 (As shown); Delete TL25 in the second frequency selection filter, and also delete MT2 (Delete), then directly connect TL21 and TL22 (as shown). Figure 9 and Figure 10 (as shown); as Figure 10 and 11 As shown, add a three-port MTEE$ connector numbered MT3 to connect TL8 and TL23 (TL23 is actually a bent section of TL22, and the original TL22 is composed of TL23 and TL22) together through MT3; add another three-port MTEE$ connector numbered MT4, and add an MLIN device numbered TL24 between MT3 and MT4. The line width of TL24 is the same as that of TL26, and the line length is set to 1.02mm. Connect MT3 and MT4 through TL24, and connect TL24 and TL26 through MT4. Add another MLIN device numbered TL25 to MT4 (that is, add a microstrip transmission line in parallel with the connection point between the output of the first frequency selective filter and the second frequency selective filter and the input of the power divider). The line width of TL25 is set to 1mm, and the line length is set to 1mm, thus obtaining the frequency selective combined broadband power divider model. The TL25 can participate in the filter resonance and also adjust the impedance matching between the first frequency selective filter, the second frequency selective filter and the power divider by adjusting the line width and line length.

[0105] Step 4: Debug the frequency-selective combined broadband power divider model to ensure that the circuit performance meets the design expectations.

[0106] First, create a new chart 1 and add curves S11 (input VSWR curve of input port 1), S22 (input VSWR curve of input port 2), S33 (output VSWR curve of output port 3), and S44 (output VSWR curve of output port 4). Create a new chart 2 and add curves S31 (loss curve from input port 1 to output port 3), S41 (loss curve from input port 1 to output port 4), S32 (loss curve from input port 2 to output port 3), and S42 (loss curve from input port 2 to output port 4). Create a new chart 3 and add curves S21 (isolation curve between input port 1 and input port 2) and S43 (isolation curve between output port 3 and output port 4). Calculate the VSWR, loss, and isolation of this microstrip circuit from 1000 to 8000 MHz.

[0107] In the design of both the power divider and the filter, the line length and linewidth of the microstrip transmission lines were set as parameters. First, the Tune Tool was used to set all parameters as variables. Then, Tune was clicked. When all curves of the frequency-selective combined broadband power divider model met the requirements, the parameters of the frequency-selective combined broadband power divider model were output. In this embodiment, the specific line length and linewidth of each microstrip transmission line in the microstrip circuit of the frequency-selective combined broadband power divider model are as follows:

[0108] The first frequency selection filter consists of: TL1, a 50-ohm input microstrip transmission line with a linewidth of 1.25 mm and a length of 15.3 mm; TL2, a resonant microstrip transmission line with a linewidth of 0.63 mm and a length of 0.9 mm; TL3, a coupled microstrip transmission line with a linewidth of 0.86 mm and a length of 18.98 mm; TL4, a resonant microstrip transmission line with a linewidth of 0.99 mm and a length of 12.7 mm; TL5, a coupled microstrip transmission line with a linewidth of 0.41 mm and a length of 19.15 mm; TL6, a resonant microstrip transmission line with a linewidth of 0.99 mm and a length of 12.7 mm; and TL7, a coupled microstrip transmission line. The line width is 0.41mm and the line length is 19.15mm; TL8 is a coupled microstrip transmission line with a line width of 1.25mm and a line length of 15.78mm; MT1 is a three-port device used to connect TL1, TL2 and TL3; MS1 and MS2 are two-port devices that connect three TL3 sections and form a 90° corner; MX1 is a four-port device used to connect TL3, TL5 and two TL4 sections; MX2 is a four-port device used to connect TL5, TL7 and two TL6 sections; MS3 is a two-port device that connects two TL7 sections and forms a 90° corner.

[0109] The second frequency-selective filter consists of: TL9, a 50-ohm input microstrip transmission line with a linewidth of 0.48 mm and a length of 2.22 mm; TL10, a resonant microstrip transmission line with a linewidth of 1.25 mm and a length of 3.78 mm; TL11, a coupled microstrip transmission line with a linewidth of 0.48 mm and a length of 3.86 mm; TL12, a resonant microstrip transmission line with a linewidth of 1.1 mm and a length of 3.57 mm; and TL13, a resonant microstrip transmission line with a linewidth of 1.68 mm and a length of 3.57 mm. TL14 is a coupled microstrip transmission line with a linewidth of 0.63 mm and a length of 3.21 mm; TL15 is a resonant microstrip transmission line with a linewidth of 2.07 mm and a length of 3.03 mm; TL16 is a resonant microstrip transmission line with a linewidth of 2.53 mm and a length of 1.53 mm; TL17 is a resonant microstrip transmission line with a linewidth of 2.43 mm and a length of 2.7 mm; TL18 is a coupled microstrip transmission line with a linewidth of 0.71 mm and a length of 3.27 mm; TL TL19 is a resonant microstrip transmission line with a linewidth of 1.42 mm and a length of 4.27 mm; TL20 is a resonant microstrip transmission line with a linewidth of 1.42 mm and a length of 2.74 mm; TL21 is a coupled microstrip transmission line with a linewidth of 0.65 mm and a length of 4.14 mm; TL22 is a coupled microstrip transmission line with a linewidth of 0.48 mm and a length of 33.47 mm; TL23 is a coupled microstrip transmission line with a linewidth of 0.48 mm and a length of 12.58 mm; MT2 is a three-terminal... The device has four ports: MX1, MX2, and MX3; MX4, MX5, and MX6; and MS3, MX22, and MS3. MX3 is a four-port device used to connect TL9, TL10, and TL11. MX4 is a four-port device used to connect TL11, TL12, TL13, and TL14. MX5 is a four-port device used to connect TL18, TL19, TL20, and TL21. MS3 is a two-port device that connects TL22 and TL22 and also forms a 90° corner.

[0110] The filter and power divider connection coupling section consists of: TL24, a coupled microstrip transmission line with a line width of 1.27 mm and a length of 1.02 mm; TL25, a resonant impedance matching microstrip transmission line with a line width of 2.3 mm and a length of 1.2 mm; TL26, a coupled microstrip transmission line with a line width of 1.27 mm and a length of 3 mm; and MT4, a three-port device used to connect TL24, TL25, and TL26.

[0111] The power divider consists of: 1. Two symmetrical first-section quarter-wavelength impedance transformation lines, with a line width of 0.49mm and a line length of 9.66mm; 2. Two symmetrical second-section quarter-wavelength impedance transformation lines, with a line width of 0.63mm and a line length of 10.34mm; 3. Two symmetrical third-section quarter-wavelength impedance transformation lines, with a line width of 0.83mm and a line length of 10.28mm; 4. Two symmetrical fourth-section quarter-wavelength impedance transformation lines, with a line width of 1.07mm and a line length of 10.19mm; 5. Two symmetrical fifth-section quarter-wavelength impedance transformation lines, with a line width of 1.29mm and a line length of 10.16mm; 6. Two symmetrical sixth-section quarter-wavelength impedance transformation lines, with a line width of 1.45mm and a line length of 10.29mm.

[0112] Output section: TL27 is a 50-ohm output microstrip transmission line with a line width of 1.27mm and a line length of 0.5mm; TL28 is a 50-ohm output microstrip transmission line with a line width of 1.27mm and a line length of 0.5mm; TL29 is a 50-ohm output microstrip transmission line with a line width of 1.27mm and a line length of 0.5mm; TL30 is a 50-ohm output microstrip transmission line with a line width of 1.27mm and a line length of 0.5mm; TL31 is a 50-ohm output microstrip transmission line with a line width of 1.27mm and a line length of 0.5mm; TL32 is a 50-ohm output microstrip transmission line with a line width of 1.27mm and a line length of 0.5mm; TL33 is a 50-ohm output microstrip transmission line with a line width of 1.27mm and a line length of 0.5mm; TL34 is a 50-ohm output microstrip transmission line with a line width of 1.27mm and a line length of 0.5mm; The transmission line has a width of 1.27mm and a length of 0.5mm. MS5 is a two-port device that connects TL29 and TL31 and forms a 90° corner. MS6 is a two-port device that connects TL27 and TL29 and forms a 90° corner. MS7 is a two-port device that connects TL28 and TL30 and forms a 90° corner. MS8 is a two-port device that connects TL30 and TL32 and forms a 90° corner. MS9 is a two-port device that connects TL31 and TL33 and forms a 90° corner. MS10 is a two-port device that connects TL32 and TL34 and forms a 90° corner.

[0113] Resistors: R1 is the isolation resistor between the two symmetrical first quarter-wavelength impedance transformation lines, with a resistance of 10 ohms; R2 is the isolation resistor between the two symmetrical second quarter-wavelength impedance transformation lines, with a resistance of 51 ohms; R3 is the isolation resistor between the two symmetrical third quarter-wavelength impedance transformation lines, with a resistance of 100 ohms; R4 is the isolation resistor between the two symmetrical fourth quarter-wavelength impedance transformation lines, with a resistance of 130 ohms; R5 is the isolation resistor between the two symmetrical fifth quarter-wavelength impedance transformation lines, with a resistance of 240 ohms; R6 is the isolation resistor between the two symmetrical sixth quarter-wavelength impedance transformation lines, with a resistance of 430 ohms.

[0114] The calculation results for each curve are as follows Figures 12-14 As shown, from Figures 12-14 As can be seen, each curve meets the corresponding requirements.

[0115] Step 5: Simulate the frequency selection combined broadband power divider model after debugging to obtain the final frequency selection combined broadband power divider model.

[0116] Import the debugged frequency-selective combined broadband power divider model into the HFSS software (e.g., Figure 15 As shown, electromagnetic simulation calculations are performed in HFSS software, and the parameters are optimized. When the simulation output results meet the design requirements and the isolation meets the requirements, the design of the frequency selection combiner broadband power divider model is completed.

[0117] The specific operation process is as follows: In the microstrip circuit schematic diagram of AWR software, click View Layout to generate a layout preview, then click Layout, select Export Layout, select DXF format, set the file name, and then open the file in HFSS software. Perform electromagnetic simulation calculations in the same environment as in AWR. Create a new graph 1 and add curves S11, S22, S33, and S44; create a new graph 2 and add curves S31, S41, S32, and S42; create a new graph 3 and add curves S21 and S43. Calculate the standing wave ratio, loss, and isolation of this circuit in the 1000–8000MHz range. Figures 16-18 As shown.

[0118] according to Figures 16-18 Simulation results show that the frequency-selective combined broadband power divider model designed in this invention (i.e., a combined broadband power divider with frequency selection function) has achieved the design expectation. It has frequency-selective combining and power dividing functions at 1500MHz and 6840~7240MHz, and has the effects of low loss, good standing wave ratio, and excellent isolation.

[0119] Step 6: Based on the final frequency selection and combination broadband power divider model, draw the PCB and send the relevant PCB manufacturing files to the PCB manufacturer for PCB processing to obtain the actual power divider.

[0120] The power divider of this invention uses Rogers 5880 board as the PCB substrate. The top surface of the substrate is designed with radio frequency microstrip circuits, the bottom surface of the substrate is copper-plated (as a reference ground for the microstrip radio frequency circuits), the power divider has isolation resistors that need to be soldered, and SMA connectors for inputting and outputting radio frequency signals.

[0121] The power divider obtained in step 6 was tested, such as... Figures 19-21 As shown, by Figure 19 It can be seen that the power divider has frequency selectivity at a frequency of 1500MHz, with a loss of 4.6dB, which significantly reduces loss compared to traditional solutions, while also exhibiting good standing wave ratio (SWR). Figure 20 It can be seen that the frequency selectivity is achieved in the 6840-7240MHz range, with a loss of 5.4-5.9dB, which significantly reduces loss compared to traditional solutions, while also exhibiting good VSWR. Figure 21 It can be seen that the isolation meets the design requirement of greater than 15 at both the frequency point and frequency band where the frequency is selected.

[0122] This invention combines a filter and a power divider in a direct connection manner. By moving the last stage resonant microstrip transmission line of the filter to the common connection end, it achieves the effect of frequency selection, combining, and power dividing. At the same time, it reduces the loss that should be introduced by two power dividers compared to the ordinary combining and power dividing scheme, and also reduces the circuit size. It has the technical feature of 1+1 being greater than 2.

[0123] This invention moves the first-stage resonant microstrip transmission line of the two filters to the common connection terminal, so that the microstrip transmission line, which originally only played a resonant role, can not only play a resonant role, but also adjust the impedance matching between the filter and the power divider connection. This achieves the combining effect without using a combiner and reduces the circuit size.

[0124] The above description only discloses specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or modifications that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A design method of a combined broadband power divider with frequency selection function, characterized in that, The design method includes the following steps: Design a power divider based on the operating frequency range and passband bandwidth requirements; Design a first frequency selective filter and a second frequency selective filter to ensure good performance within the operating frequency range; Connect the output terminals of the first frequency selective filter and the second frequency selective filter to the input terminal of the power divider, and perform the following operations during connection: Delete the first resonant microstrip transmission line that is closest to the output end of the first frequency selective filter. Delete the second resonant microstrip transmission line that is closest to the output of the second frequency selection filter; An additional microstrip transmission line is added in parallel with the interface between the output of the first frequency selective filter and the second frequency selective filter and the input of the power divider. By combining the deletion of the first resonant microstrip transmission line and the second resonant microstrip transmission line with the addition of an additional microstrip transmission line, the additional microstrip transmission line simultaneously performs the following dual functions: Participate in the resonance of the first frequency selective filter and the second frequency selective filter; adjust the impedance matching between the first frequency selective filter, the second frequency selective filter and the power divider connection; A model of a frequency-selective broadband power divider was obtained. The frequency selective combiner broadband power divider model was debugged and simulated to obtain the final frequency selective combiner broadband power divider model.

2. The design method of the combined broadband power divider with frequency selection function according to claim 1, characterized in that, The operating frequency range is 1500~7240MHz.

3. The design method of the combined broadband power divider with frequency selection function according to claim 1, characterized in that, The specific implementation process of designing a power divider based on the operating frequency range and passband bandwidth requirements includes: Determine the number of sections of the impedance transformation line, and use the even-mode circuit design method to determine the impedance and electrical length of each section of the impedance transformation line; The value of the isolation resistor to be added for each impedance transformation line is determined by using the odd-mode circuit design method; Construct a power divider circuit schematic, substitute the impedance and electrical length of each impedance transformation line and the resistance value of the isolation resistor into the power divider circuit schematic, and verify the power divider circuit schematic. Once the verification is successful, the length and width of the corresponding quarter-wavelength impedance transformation line are calculated based on the impedance and electrical length of each section of the impedance transformation line. Construct the power divider layout diagram based on the power divider circuit schematic, the line length and line width of the quarter-wavelength impedance transformation line.

4. The design method of the combined broadband power divider with frequency selection function according to claim 3, characterized in that, The specific implementation process of determining the impedance and electrical length of each impedance transformation line using the even-mode circuit design method is as follows: Construct an even-mode circuit consisting of n impedance transformation lines connected in series, and add input and output ports to the even-mode circuit; Set the impedance of the input and output ports, and set the impedance and electrical length of each impedance transformation line as variables; Add input and output standing wave curves, and set the optimization target; Calculate the input standing wave curve and output standing wave curve of the even-mode circuit. When the input standing wave curve and output standing wave curve of the even-mode circuit reach the optimization target, record the impedance and electrical length of each impedance transformation line.

5. The design method of the combined broadband power divider with frequency selection function according to claim 3, characterized in that, The specific implementation process for determining the value of the isolation resistor to be added to each impedance transformation line using the odd-mode circuit design method is as follows: Remove the input port from the even-mode circuit, and add isolation resistors between adjacent impedance transformation lines and between the last impedance transformation line and the output port. Connect the unconnected end of the first impedance transformation line and each isolation resistor to the ground port to obtain the odd-mode circuit. Substitute the impedance and electrical length of each impedance transformation line into the odd-mode circuit; Add input and output standing wave curves, and set the optimization target; Calculate the input standing wave (SWR) curve and output standing wave (SWR) curve of the odd-mode circuit. When the input SWR curve and output SWR curve of the odd-mode circuit reach the optimization target, record the resistance value of each isolation resistor.

6. The design method of the combined broadband power divider with frequency selection function according to claim 1, characterized in that, The specific implementation process for designing a first frequency selective filter or a second frequency selective filter is as follows: Determine the design specifications for the first frequency selective filter or the second frequency selective filter; Set the parameters in iFilter Filter Synthesis in AWR software Wizards according to the design specifications; The microstrip circuit schematic of the filter, as well as loss and standing wave calculation curves, are automatically generated based on the set parameters. When the loss and standing wave ratio meet the requirements, generate the microstrip circuit layout of the filter.

7. The design method of the combined broadband power divider with frequency selection function according to claim 1, characterized in that, The specific implementation process for debugging the frequency-selective combined broadband power divider model is as follows: Add input VSWR curve, output VSWR curve, loss curve, and isolation curve; All parameters of the frequency-selective combined broadband power divider model are set as variables; Calculate the standing wave ratio, loss, and isolation of the frequency-selective broadband power divider model; When the standing wave ratio, loss, and isolation all meet the requirements, the parameters of the frequency-selective combined broadband power divider model are determined.

8. The design method of the combined broadband power divider with frequency selection function according to claim 1, characterized in that, The specific implementation process of simulating the frequency-selective combined broadband power divider model is as follows: The debugged frequency-selective combined broadband power divider model was imported into HFSS for electromagnetic simulation calculations, and the parameters were optimized. When the simulation output meets the design requirements and the isolation meets the requirements, the design of the frequency selection combiner broadband power divider model is completed.

9. The design method of the combined broadband power divider with frequency selection function according to claim 1, characterized in that, The design method further includes: Based on the final frequency selection and combination broadband power divider model, the PCB is drawn, and the PCB file is sent to the PCB manufacturer for PCB processing to obtain the designed power divider physical object.

10. A combined broadband power divider with frequency selection function, characterized in that, The combined broadband power divider is designed using the design method described in any one of claims 1 to 9.

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