Design method of radio frequency broadband impedance matching network

Abstract

The invention discloses a radio frequency broadband impedance matching network design method, relates to the technical field of radio frequency microwaves, and is used for realizing impedance matching of front and rear stages of a broadband radio frequency circuit. Comprising two matching units: one is a parallel LC unit which can simulate a parallel inductor or a parallel capacitor or an open circuit in a matching circuit; one unit is a series LC unit which can simulate a series inductor or a series capacitor or a short circuit in a matching circuit; a proper number of parallel LC units and series LC units are selected to be cascaded, and the reflection coefficient is optimized to be below-10dB through simulation, so that the purpose of broadband impedance matching is achieved; according to the invention, the radio frequency broadband impedance matching network can be simply and effectively realized, the design difficulty is greatly reduced, and the design efficiency is improved; a designer does not need to have rich design experience and deep radio frequency technology reserve, broadband matching can be completed only by gradually inserting a pair of cascaded parallel LC units and series LC units and using simulation software for optimization, and the matching process is simple and effective.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency microwave technology, and in particular to a radio frequency broadband impedance matching network design method. Background Art

[0002] Ultra Wideband (UWB) technology is a wireless communication technology. Compared with traditional narrowband communication technology, UWB technology has a very wide bandwidth and a high corresponding data transmission rate. With high bandwidth and narrow pulses, UWB technology has a strong time resolution capability. It is currently widely used in the fields of ranging and positioning. It is also because of its high time resolution capability that it has strong anti-multipath capability. UWB technology was originally developed by the US Department of Defense Research Agency (DARPA) in the 1960s and is mainly used in radar systems and military communications. The characteristics of UWB technology are extremely wide signal bandwidth, and the time domain and frequency domain characteristics of the signal are very complex. High-resolution target detection and tracking can be achieved through this signal. For ultra-wideband circuits, impedance matching of the front-end and rear-end RF circuits is required within a very wide bandwidth.

[0003] Traditional impedance matching methods usually use the Smith chart for design, generally only considering the impedance change at the center frequency point. This method can only achieve good impedance matching for a single frequency point.

[0004] When designing a broadband impedance matching circuit, various matching circuit structures are usually tried manually, and then optimized through simulation software to finally obtain a broadband impedance matching circuit. The design is time-consuming and labor-intensive, and relies more on the designer's design experience. This method relies heavily on the designer's experience, and the design is time-consuming and irregular. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a broadband RF impedance matching network design method in view of the shortcomings of the background technology; select a suitable number of parallel LC units and series LC units for cascading, optimize the reflection coefficient to below -10dB through simulation, and achieve the purpose of broadband impedance matching.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] A method for designing a radio frequency broadband impedance matching network specifically comprises the following steps:

[0008] Step 1: Clearly determine the load impedance Zl and source impedance Zs that need to be matched;

[0009] Step 2, insert a broadband RF impedance matching network between the load impedance ZL and the source impedance Zs, and perform simulation optimization; wherein the broadband RF impedance matching network includes a pair of cascaded parallel LC units and series LC units, and the load impedance ZL and the impedance Z0 after the broadband RF impedance matching network is cascaded and the input reflection coefficient S11 at this time are simulated, and the corresponding relationship is:

[0010]

[0011] In dB form:

[0012]

[0013] Step 3: When the load impedance ZL and the source impedance Zs are fully matched after inserting a broadband RF impedance matching network, that is, Zo = Zs, the input reflection coefficient is zero, that is, the circuit is fully matched; usually, the broadband circuit cannot be fully matched within the band, and the reflection coefficient within the band can be controlled below -10dB, that is:

[0014]

[0015] Step 4, observe in the simulation software whether the values ​​of S11 in the band are all less than -10dB. If not, set the parameter θ value variable range of the parallel LC unit and the series LC unit in the simulation software, set the optimization target S11<-10dB, and perform automatic optimization;

[0016] If the optimization result S11<-10dB, the goal is achieved. If the optimization result does not meet S11<-10dB, a pair of cascaded parallel LC units and series LC units are continuously inserted into the broadband RF impedance matching network, and steps 2 to 4 are repeated until the optimization result S11<-10dB.

[0017] Step 5, according to the optimized θ value, determine the types and values ​​of parallel elements and series elements represented by the parallel LC unit and the series LC unit in the broadband RF impedance matching network, that is, complete the design of the broadband RF impedance matching network.

[0018] As a further preferred embodiment of a radio frequency broadband impedance matching network design method of the present invention, the parallel LC unit is a schematic unit described in Verilog A language, which is used to characterize a parallel inductor or parallel capacitor or open circuit in the impedance matching network.

[0019] As a further preferred embodiment of a radio frequency broadband impedance matching network design method of the present invention, the series LC unit is a schematic unit described in Verilog A language, which is used to characterize the series inductance or parallel capacitance or short circuit in the impedance matching network.

[0020] As a further preferred embodiment of the method for designing a radio frequency broadband impedance matching network of the present invention, the characteristic impedance of the parallel LC unit can be expressed as:

[0021]

[0022] Where Z0 is the standard reference impedance of the RF system, which is generally 50 ohms; f is the simulation frequency; f0 is the bandwidth center frequency; P i The constant is pi

[0023] When θ>0, Z PLC Proportional to f, it can be equivalent to a parallel inductor, and its inductance is

[0024] L p =[Z0cot(θ / 2)] / (2*P i *f0);

[0025] When θ<0, Z PLC Inversely proportional to f, it can be equivalent to a capacitor in parallel, and its capacitance value is

[0026] C p =[tan(-θ / 2)] / (2*P i *f0*Z0);

[0027] When θ=0, it is equivalent to an open circuit.

[0028] As a further preferred embodiment of the method for designing a radio frequency broadband impedance matching network of the present invention, the characteristic impedance of the series LC unit can be expressed as:

[0029]

[0030] Among them, Z0 is the standard reference impedance of the RF system, is the simulation frequency; is the bandwidth center frequency;

[0031] When θ≥0, Z SLC Proportional to f, it can be equivalent to a series inductor, and its inductance value is

[0032] L s =[Z0tan(θ / 2)] / (2*P i *f0);

[0033] When θ<0, Z SLC Inversely proportional to f, it can be equivalent to a capacitor in series, and its capacitance value is

[0034] C s =[cot(-θ / 2)] / (2*P i *f0*Z0);

[0035] When θ=0, it is equivalent to a short circuit.

[0036] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0037] 1. The present invention discloses a method for designing a radio frequency broadband impedance matching network, which is used to achieve impedance matching between the front and rear stages of a broadband radio frequency circuit; it includes two matching units: one is a parallel LC unit, which can simulate the parallel inductance or parallel capacitance or open circuit in the matching circuit; the other is a series LC unit, which can simulate the series inductance or series capacitance or short circuit in the matching circuit. According to the index requirements, an appropriate number of parallel LC units and series LC units are selected for cascading, and the reflection coefficient is optimized to below -10dB through simulation to achieve the purpose of broadband impedance matching; the present invention can simply and effectively realize a radio frequency broadband impedance matching network, greatly reduce the design difficulty, and improve the design efficiency;

[0038] 2. The broadband RF impedance matching network design method described in the present invention does not require the designer to have rich design experience and deep RF technical reserves. It only needs to gradually insert a pair of cascaded parallel LC units and series LC units and use simulation software for optimization to complete broadband matching. The matching process is simple and effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 It is a trajectory diagram of the parallel LC unit and the series LC unit in the Smith chart of the present invention;

[0041] Figure 2 This is a diagram of the in-band source impedance Zs value of the present invention;

[0042] Figure 3 This is the result diagram of the S11 parameter of the in-band frequency division point mismatch of the present invention;

[0043] Figure 4 It is a schematic diagram of a broadband radio frequency impedance matching network after inserting several pairs of cascaded parallel LC units and series LC units of the present invention;

[0044] Figure 5 It is the S11 parameter result diagram after the optimization of the present invention is completed;

[0045] Figure 6 is a simplified diagram of a broadband radio frequency impedance matching network after conversion in the present invention;

[0046] Figure 7 It is a flow chart of the broadband radio frequency impedance matching network design method of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention is described in detail below based on the drawings and preferred embodiments, and the purpose and effect of the present invention will become clearer. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0049] To solve the above problems, the present invention proposes a broadband RF impedance matching network, and the method is as follows. First, the load impedance ZL and the source impedance Zs to be matched are clearly defined.

[0050] Next, a broadband RF impedance matching network is inserted between the load impedance ZL and the source impedance Zs, which includes a pair of cascaded parallel LC units and series LC units. The load impedance ZL and the impedance Zo after the broadband RF impedance matching network is cascaded, and the input reflection coefficient S11 at this time are obtained by simulation. The corresponding relationship is:

[0051]

[0052] In dB form:

[0053]

[0054] When the load impedance ZL and the source impedance Zs are fully matched after inserting a broadband RF impedance matching network, that is, Zo = Zs, the input reflection coefficient is zero, that is, the circuit is fully matched. Usually, broadband circuits cannot be fully matched within the band, and engineering generally requires that the reflection coefficient within the band be controlled below -10dB, that is:

[0055]

[0056] Observe whether the S11 value in the band is less than -10dB in the simulation software. If not, set the parameter θ value variable range of the parallel LC unit and the series LC unit in the simulation software, set the optimization target S11<-10dB, and perform automatic optimization.

[0057] If the optimization result S11<-10dB, the goal is achieved. If the optimization result does not meet S11<-10dB, continue to insert a pair of cascaded parallel LC units and series LC units in the broadband RF impedance matching network, and repeat the above steps 7, 8, and 9 until the optimization result S11<-10dB

[0058] According to the optimized θ value, determine the types and values ​​of parallel and series components represented by parallel LC units and series LC units in the broadband RF impedance matching network

[0059] The characteristic impedance of the parallel LC unit can be expressed as

[0060]

[0061] Where Z0 is the standard reference impedance of the RF system, which is generally 50 ohms; f is the simulation frequency; f0 is the bandwidth center frequency; P i The constant is pi;

[0062] When θ>0, Z PLC Proportional to f, it can be equivalent to a parallel inductor, and its inductance is

[0063] L p =[Z0cot(θ / 2)] / (2*P i *f0);

[0064] When θ<0, Z PLC Inversely proportional to f, it can be equivalent to a capacitor in parallel, and its capacitance value is

[0065] C p =[tan(-θ / 2)] / (2*P i *f0*Z0);

[0066] When θ=0, it is equivalent to an open circuit.

[0067] The characteristic impedance of the series LC unit can be expressed as

[0068]

[0069] Among them, Z0 is the standard reference impedance of the RF system, is the simulation frequency; is the bandwidth center frequency;

[0070] When θ≥0, Z SLC Proportional to f, it can be equivalent to a series inductor, and its inductance value is

[0071] L s =[Z0 tan(θ / 2)] / (2*P i *f0);

[0072] When θ<0, ZSLC Inversely proportional to f, it can be equivalent to a capacitor in series, and its capacitance value is

[0073] C s =[cot(-θ / 2)] / (2*P i *f0*Z0);

[0074] When θ=0, it is equivalent to a short circuit.

[0075] The broadband RF impedance matching network method described in the present invention does not require the designer to have rich design experience and deep RF technical reserves. It only needs to gradually insert a pair of cascaded parallel LC units and series LC units and use simulation software for optimization to complete broadband matching. The matching process is simple and effective.

[0076] Embodiment 1:

[0077] For a given RF circuit, one or more pairs of cascaded parallel LC cells and series LC cells are inserted between the load impedance ZL and the source impedance Zs, where the parallel LC cell can simulate the parallel inductance or parallel capacitance or open circuit in the matching circuit; the series LC cell can simulate the series inductance or series capacitance or short circuit in the matching circuit. By optimizing the parameter θ value in the parallel LC cell and the series LC cell through simulation, the specific network structure and parameters are obtained, and a broadband impedance matching network can be obtained.

[0078] The present invention is described in detail below with reference to the accompanying drawings and specific examples.

[0079] Figure 1 It shows the trajectory diagram of parallel LC cells and series LC cells in the Smith chart. Figure 1 (a) is a parallel LC unit. When θ=0, it means that the parallel LC unit represents an inductor with infinite inductance or a capacitor with a capacitance close to 0 in parallel, that is, the impedance value is infinite, which is equivalent to an open circuit. When θ=±π, it is equivalent to an inductor with an inductance close to 0 or a capacitor with a capacitance close to infinity in parallel, that is, the impedance value is infinitely small, which is equivalent to a short circuit to ground. Figure 1 (b) is a series LC unit. When θ=0, it indicates that the series LC unit represents a series connection of an inductor with an inductance close to 0 or a series connection of a capacitor with an infinite capacitance, that is, the impedance value is infinitely small, which is equivalent to a short circuit. When θ=±π, it is equivalent to a series connection of an inductor with an inductance close to infinity or a series connection of a capacitor with a capacitance close to 0, that is, the impedance value is infinite, which is equivalent to an open circuit.

[0080] Now, the specific implementation mode of the present invention is described by taking the design of a specific broadband power amplifier (PA) output matching circuit as an example.

[0081] Step 1: Identify the load impedance ZL and source impedance Zs that need to be matched

[0082] The power amplifier load impedance ZL is usually a 50 ohm load. Active load-pull power simulation is performed on the selected power amplifier transistor within the bandwidth to obtain the in-band source impedance Zs value, such as Figure 2 Shown

[0083] Step 2: Next, insert a broadband RF impedance matching network between the load impedance ZL and the source impedance Zs, which includes a pair of cascaded parallel LC units and series LC units. By setting the value range of the variable θ in the parallel LC unit and the series LC unit to -π≤θ≤π, use the simulation software to set the in-band optimization target value S11<-10 and then perform automatic optimization. If the optimization is to within the band S11<-10, go to step 4, otherwise go to step 3. The optimization results of step 2 in this example are shown in Figure 3 It is known that it is impossible to optimize to all S11<-10 in the band, so go to step 3

[0084] Step 3: Continue to insert a pair of cascaded parallel LC cells and series LC cells in the broadband RF impedance matching network, such as Figure 4 As shown, repeat the above step 2 until the optimization result S11<-10dB, and the final simulation S11 result is shown in Figure 5 Shown

[0085] Step 4: According to the final simulation optimization of each parameter θ value, the following method is used to correspond to each matching component type and component parameter value. The matching circuit parameters are shown in Figure 6

[0086] The characteristic impedance of the parallel LC unit can be expressed as

[0087]

[0088] Where Z0 is the standard reference impedance of the RF system, which is generally 50 ohms; f is the simulation frequency; f0 is the bandwidth center frequency; P i The constant is pi

[0089] When θ>0, Z PLC Proportional to f, it can be equivalent to a parallel inductor, and its inductance is

[0090] L p =[Z0cot(θ / 2)] / (2*P i *f0);

[0091] When θ<0, Z PLC Inversely proportional to f, it can be equivalent to a capacitor in parallel, and its capacitance value is

[0092] C p=[tan(-θ / 2)] / (2*P i *f0*Z0);

[0093] When θ=0, it is equivalent to an open circuit.

[0094] The characteristic impedance of the series LC unit can be expressed as

[0095]

[0096] Among them, Z0 is the standard reference impedance of the RF system, is the simulation frequency; is the bandwidth center frequency;

[0097] When θ≥0, Z SLC Proportional to f, it can be equivalent to a series inductor, and its inductance value is

[0098] L s =[Z0tan(θ / 2)] / (2*P i *f0);

[0099] When θ<0, Z SLC Inversely proportional to f, it can be equivalent to a capacitor in series, and its capacitance value is

[0100] C s =[cot(-θ / 2)] / (2*P i *f0*Z0);

[0101] When θ=0, it is equivalent to a short circuit.

[0102] At this point, the design of the broadband power amplifier (PA) output matching circuit is completed. The design process of the broadband RF impedance matching network is summarized as follows: Figure 7 The present invention is also applicable to the design of matching networks for any broadband radio frequency circuit structure, including the design of low noise amplifiers, power amplifiers, mixers and other circuits.

[0103] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0104] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention should be included in the protection scope of the invention. All technical features in this embodiment can be freely combined according to actual needs.

[0105] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing a radio frequency broadband impedance matching network, characterized in that: The specific steps include: Step 1: Clearly determine the load impedance Zl and source impedance Zs that need to be matched; Step 2, insert a broadband RF impedance matching network between the load impedance ZL and the source impedance Zs, and perform simulation optimization; wherein the broadband RF impedance matching network includes a pair of cascaded parallel LC units and series LC units, and the load impedance ZL and the impedance Z0 after the broadband RF impedance matching network is cascaded and the input reflection coefficient S11 at this time are simulated, and the corresponding relationship is: In dB form: Step 3: When the load impedance ZL and the source impedance Zs are fully matched after inserting a broadband RF impedance matching network, that is, Zo = Zs, the input reflection coefficient is zero, that is, the circuit is fully matched; usually, the broadband circuit cannot be fully matched within the band, and the reflection coefficient within the band can be controlled below -10dB, that is: Step 4, observe in the simulation software whether the values ​​of S11 in the band are all less than -10dB. If not, set the parameter θ value variable range of the parallel LC unit and the series LC unit in the simulation software, set the optimization target S11<-10dB, and perform automatic optimization; If the optimization result S11<-10dB, the goal is achieved. If the optimization result does not meet S11<-10dB, a pair of cascaded parallel LC units and series LC units are continuously inserted into the broadband RF impedance matching network, and steps 2 to 4 are repeated until the optimization result S11<-10dB. Step 5, according to the optimized θ value, determine the types and values ​​of parallel elements and series elements represented by the parallel LC unit and the series LC unit in the broadband RF impedance matching network, that is, complete the design of the broadband RF impedance matching network.

2. The method for designing a radio frequency broadband impedance matching network according to claim 1, characterized in that: The parallel LC unit is a schematic unit described in Verilog A language, and is used to represent a parallel inductor or a parallel capacitor or an open circuit in an impedance matching network.

3. The method for designing a radio frequency broadband impedance matching network according to claim 1, characterized in that: The series LC unit is a schematic unit described in Verilog A language, and is used to represent a series inductor or a parallel capacitor or a short circuit in an impedance matching network.

4. The method for designing a radio frequency broadband impedance matching network according to claim 1, characterized in that: The characteristic impedance of the parallel LC unit can be expressed as Where Z0 is the standard reference impedance of the RF system, which is generally 50 ohms; f is the simulation frequency; f0 is the bandwidth center frequency; P i The constant is pi; When θ>0, Z PLC Proportional to f, it can be equivalent to a parallel inductor, and its inductance is L p =[Z0cot(θ / 2)] / (2*P i *f0); When θ<0, Z PLC Inversely proportional to f, it can be equivalent to a capacitor in parallel, and its capacitance value is C p =[tan(-θ / 2)] / (2*P i *f0*Z0); When θ=0, it is equivalent to an open circuit.

5. The method for designing a radio frequency broadband impedance matching network according to claim 3, characterized in that: The characteristic impedance of the series LC unit can be expressed as Among them, Z0 is the standard reference impedance of the RF system, is the simulation frequency; is the bandwidth center frequency; When θ≥0, Z SLC Proportional to f, it can be equivalent to a series inductor, and its inductance value is L s =[Z0tan(θ / 2)] / (2*P i *f0); When θ<0, Z SLC Inversely proportional to f, it can be equivalent to a capacitor in series, and its capacitance value is C s =[cot(-θ / 2)] / (2*P i *f0*Z0); When θ=0, it is equivalent to a short circuit.

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