A method for designing a radio frequency broadband impedance matching network

Abstract

The application discloses a kind of radio frequency broadband impedance matching network design methods, it is related to radio frequency microwave technical field, for realizing wideband radio frequency circuit front and back stage impedance matching;Including two kinds of matching units: one is parallel LC unit, can simulate parallel inductance or parallel capacitance or open circuit in matching circuit;One is series LC unit, can simulate series inductance or series capacitance or short circuit in matching circuit;Selecting appropriate number of parallel LC unit and series LC unit cascade, through simulation optimization reflection coefficient to-10dB below, realize the purpose of wideband impedance matching;The application can simply and effectively realize radio frequency broadband impedance matching network, greatly reduce design difficulty, improve design efficiency;The application does not need designer to have rich design experience and profound radio frequency technology reserve, only needs to insert a pair of cascaded parallel LC unit and series LC unit gradually, uses simulation software to optimize, can complete broadband matching, and matching process is simple and effective.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radio frequency microwave technology, and particularly relates to a design method of a radio frequency wideband impedance matching network. BACKGROUND

[0002] Ultra Wideband (UWB) technology is a wireless communication technology. Compared with traditional narrowband communication technology, the UWB technology has a very wide bandwidth and a high data transmission rate. The high bandwidth and narrow pulse enable the UWB technology to have strong time resolution capability, and the UWB technology is currently widely applied to the fields of ranging and positioning. Due to the high time resolution capability, the UWB technology also has strong anti-multipath capability. The UWB technology was initially developed by the Defense Advanced Research Projects Agency (DARPA) of the United States in the 1960s and was mainly used in radar systems and military communication fields. The UWB technology has the characteristics of a very wide signal bandwidth and very complex time domain and frequency domain characteristics of signals, and high-resolution target detection and tracking can be achieved through the signals. For an ultra-wideband circuit, impedance matching of front-stage and rear-stage radio frequency circuits needs to be achieved in a very wide bandwidth.

[0003] A traditional impedance matching method usually uses a Smith chart for design, and generally only considers impedance variation at a center frequency point. This method can only achieve good impedance matching at a single frequency point.

[0004] When designing a wideband impedance matching circuit, a designer usually tries various matching circuit structures manually and optimizes the structures through simulation software to finally obtain a wideband impedance matching circuit. The design is time-consuming and laborious, and more depends on the design experience of the designer. This method is highly dependent on the experience of the designer and is time-consuming and irregular. SUMMARY

[0005] The present application aims to solve the technical problems of the background art and provides a design method of a wideband radio frequency impedance matching network. A proper number of parallel LC units and series LC units are selected and cascaded to optimize the reflection coefficient to below -10 dB through simulation, thereby achieving the purpose of wideband impedance matching.

[0006] The present application solves the above technical problems by using the following technical solution:

[0007] A design method of a radio frequency wideband impedance matching network, specifically comprising the following steps:

[0008] Step 1: defining a load impedance Zl and a signal source impedance Zs that need to be matched;

[0009] Step 2, a wideband radio frequency impedance matching network is inserted between the load impedance ZL and the source impedance Zs, and simulation optimization is performed; wherein the wideband radio frequency impedance matching network comprises a pair of cascaded parallel LC units and series LC units, simulation obtains the impedance Z0 after the load impedance ZL and the wideband radio frequency impedance matching network are connected in series, and the input reflection coefficient S11 at this time, and the corresponding relationship is:

[0010]

[0011] In dB form:

[0012]

[0013] Step 3, when the wideband radio frequency impedance matching network is inserted between the load impedance ZL and the source impedance Zs and completely matched, that is, Zo = Zs, at this time the input reflection coefficient is zero, that is, the circuit is completely matched; in general, it is impossible to completely match in the band of the wideband circuit, and the in-band reflection coefficient is controlled to be less than -10dB, that is:

[0014]

[0015] Step 4, whether the in-band S11 value is less than -10dB is observed in the simulation software, if not, the parameter θ value variable range of the parallel LC unit and the series LC unit is set in the simulation software, the optimization target S11 <-10dB is set, and automatic optimization is performed;

[0016] If the optimization result S11 <-10dB, the target is completed, if the optimization result does not satisfy S11 <-10dB, a pair of cascaded parallel LC units and series LC units are continuously inserted in the wideband radio frequency impedance matching network, and steps 2 to 4 are repeated until the optimization result S11 <-10dB;

[0017] Step 5, according to the θ value obtained by optimization, the types and element values of the parallel elements and series elements represented by the parallel LC unit and the series LC unit in the wideband radio frequency impedance matching network are determined, that is, the design of the wideband radio frequency impedance matching network is completed.

[0018] As a further preferred scheme of the radio frequency wideband impedance matching network design method, the parallel LC unit is a schematic unit described by Verilog A language, used to represent parallel inductance or parallel capacitance or open circuit in the impedance matching network.

[0019] As a further preferred scheme of the radio frequency wideband impedance matching network design method, the series LC unit is a schematic unit described by Verilog A language, used to represent series inductance or parallel capacitance or short circuit in the impedance matching network.

[0020] As a further preferred scheme of the present application, the characteristic impedance of the parallel LC unit can be expressed as

[0021]

[0022] Wherein, Z0 is the standard reference impedance of the radio frequency system, generally 50 ohms; f is the simulation frequency; f0 is the center frequency of the bandwidth; P i The constant is the circular constant

[0023] When θ>0, Z PLC is proportional to f, which can be equivalent to a parallel inductor, and the inductance value is

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

[0025] When θ<0, Z PLC is inversely proportional to f, which can be equivalent to a parallel capacitor, and the capacitance value is

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

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

[0028] As a further preferred scheme of the present application, the characteristic impedance of the parallel LC unit can be expressed as

[0029]

[0030] Wherein, Z0 is the standard reference impedance of the radio frequency system, generally 50 ohms; f is the simulation frequency; f0 is the center frequency of the bandwidth; P

[0031] When θ≥0, Z SLC is proportional to f, which can be equivalent to a series inductor, and the inductance value is

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

[0033] When θ<0, Z SLC is inversely proportional to f, which can be equivalent to a series capacitor, and the capacitance value is

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

[0035] When θ=0, it can be equivalent to short circuit.

[0036] Compared with the prior art, the application has the following technical effects:

[0037] 1. The application discloses a design method of a wideband RF impedance matching network, which is used for realizing impedance matching of front and rear stages of a wideband RF circuit.

[0038] 2. The design method of the wideband RF impedance matching network does not require the designer to have rich design experience and deep RF technical reserves, but only needs to insert a pair of cascaded parallel LC units and series LC units step by step, and uses simulation software to optimize, so that the wideband matching can be completed, and the matching process is simple and effective. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0040] Figure 1 is the trajectory diagram of the parallel LC unit and the series LC unit in the Smith chart of the application;

[0041] Figure 2 is the in-band source impedance Zs value diagram of the application;

[0042] Figure 3 is the in-band partial frequency point mismatch S11 parameter result diagram of the application;

[0043] Figure 4 is the wideband RF impedance matching network diagram after inserting a few pairs of cascaded parallel LC units and series LC units of the application;

[0044] Figure 5 is the S11 parameter result diagram after optimization of the application;

[0045] Figure 6 is the converted wideband RF impedance matching network diagram of the application;

[0046] Figure 7 is a flow chart of the broadband RF impedance matching network design method of the present application. DETAILED DESCRIPTION

[0047] The technical solutions of the embodiments of the present application will be further described in detail below with reference to the drawings:

[0048] The technical solutions of the embodiments of the present application will be further described in detail below with reference to the drawings:

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

[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, and the impedance Zo after the load impedance ZL and the broadband RF impedance matching network are cascaded and the input reflection coefficient S11 at this time are obtained by simulation, and their corresponding relationship is:

[0051]

[0052] In dB form:

[0053]

[0054] When the broadband RF impedance matching network is completely matched between the load impedance ZL and the source impedance Zs, i.e. Zo = Zs, the input reflection coefficient is zero at this time, i.e. the circuit is completely matched. In general, it is not possible to achieve complete matching in the passband of the broadband circuit, and in engineering, it is generally necessary to control the in-band reflection coefficient to be less than -10 dB, i.e.

[0055]

[0056] In the simulation software, observe whether the value of S11 in the passband is less than -10 dB, 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 <-10 dB, and perform automatic optimization

[0057] If the optimization result S11 <-10dB, the target is completed, if the optimization result does not satisfy S11 <-10dB, a pair of cascaded parallel LC unit and series LC unit is inserted in the wideband RF impedance matching network, and the above three steps 7, 8 and 9 are repeated until the optimization result S11 <-10dB

[0058] According to the optimized θ value, the types and element values of the parallel elements and series elements represented by the parallel LC unit and the series LC unit in the wideband RF impedance matching network are determined

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

[0060]

[0061] Wherein, Z0 is the standard reference impedance of the RF system, generally 50 ohms; f is the simulation frequency; f0 is the center frequency of the bandwidth; P i The constant is the ratio of the circumference to the diameter;

[0062] When θ> 0, Z PLC is proportional to f, which can be equivalent to a parallel inductor, and the inductance value is

[0063] L p =[Z0 cot(θ / 2)] / (2*P i *f0);

[0064] When θ<0, Z PLC is inversely proportional to f, which can be equivalent to a parallel capacitor, and the capacitance value is

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

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

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

[0068]

[0069] Wherein, Z0 is the standard reference impedance of the RF system, generally 50 ohms; f is the simulation frequency; f0 is the center frequency of the bandwidth; P

[0070] When θ≥0, Z SLC is proportional to f, which can be equivalent to a series inductor, and the inductance value is

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

[0072] When θ<0, ZSLC Inversely proportional to f, which can be equivalent to a series capacitor, whose capacitance value is

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

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

[0075] The broadband RF impedance matching network method described in the application does not require the designer to have rich design experience and deep RF technology reserves, but only needs to insert a pair of cascaded parallel LC units and series LC units step by step, and use simulation software for optimization, so that the broadband matching can be completed, and the matching process is simple and effective.

[0076] Embodiment 1:

[0077] For a given RF circuit, a pair or several pairs of cascaded parallel LC units and series LC units are inserted between the load impedance ZL and the source impedance Zs, wherein the parallel LC unit can simulate a parallel inductor or a parallel capacitor or an open circuit in the matching circuit; the series LC unit can simulate a series inductor or a series capacitor or a short circuit in the matching circuit. By simulating and optimizing the parameter θ value in the parallel LC unit and the series LC unit, the specific network structure and parameters are obtained, that is, the broadband impedance matching network is obtained.

[0078] The application will be described in detail below in combination with the drawings and specific examples

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

[0080] Now taking a specific broadband power amplifier (PA) output matching circuit design as an example to illustrate the specific implementation of the application

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

[0082] The load impedance ZL of the power amplifier is usually 50 ohms. The in-band source impedance Zs is obtained by active load-pulling power simulation of the selected power amplifier transistor within the bandwidth, as shown in Figure 2

[0083] Step 2: Next, insert a wideband RF impedance matching network between the load impedance ZL and the source impedance Zs, which contains a pair of cascaded parallel LC units and series LC units. By setting the value of the variable θ in the parallel LC unit and the series LC unit to the range -π ≤ θ ≤ π, and using simulation software to set the in-band optimization target value S11 <-10, automatic optimization is performed. If the optimization results in S11 <-10 within the band, go to step four, otherwise go to step three. The step two optimization results of this example are shown in Figure 3 , which shows that it cannot be optimized to S11 <-10 within the band, so go to step three

[0084] Step 3: Continue to insert a pair of cascaded parallel LC units and series LC units in the wideband RF impedance matching network, as shown in Figure 4 , repeat the above step two until the optimization results S11 <-10 dB, and the final simulation S11 results are shown in Figure 5

[0085] Step 4: According to the final simulation optimization of each parameter θ value, the corresponding matching element type and element parameter value are obtained by the following method, and 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, generally 50 ohms; f is the simulation frequency; f0 is the center frequency of the bandwidth; P i is a constant, and π is the constant of the circle

[0089] When θ > 0, Z PLC is proportional to f, which can be equivalent to a parallel inductor with an inductance value of

[0090] L p = [Z0 cot(θ / 2)] / (2*P i *f0);

[0091] When θ < 0, Z PLC is inversely proportional to f, which can be equivalent to a parallel capacitor with a capacitance value of

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

[0093] When θ = 0, it can be equivalent to open circuit.

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

[0095]

[0096] Wherein, Z0 is a standard reference impedance of a radio frequency system, and is a simulation frequency; is a center frequency of a bandwidth;

[0097] When θ ≥ 0, Z SLC is proportional to f, and can be equivalent to a series inductance, and the inductance value is

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

[0099] When θ < 0, Z SLC is inversely proportional to f, and can be equivalent to a series capacitance, and the capacitance value is

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

[0101] When θ = 0, it can be equivalent to short circuit.

[0102] So far, the design work of a wideband power amplifier (PA) output matching circuit is completed. The design method process of a wideband radio frequency impedance matching network is shown in the figure. Figure 7 The present application is also applicable to the matching network design of any wideband radio frequency circuit structure, including the design of low noise amplifiers, power amplifiers, mixers and the like.

[0103] The above only describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present application.

[0104] Those skilled in the art can understand that the above only describes the preferred examples of the present application and is not used to limit the present application, although the present application is described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions recorded in the foregoing examples or make equivalent replacement for part of the technical features. Any modification, equivalent replacement and the like within the spirit and principles of the present application should be included in the protection scope of the present application. All technical features in the embodiments can be freely combined according to actual needs.

[0105] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent ones, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of designing a radio frequency broadband impedance matching network, characterized by: Specifically comprising the following steps: Step 1, clearly need to match the load impedance Zl and source impedance Zs; Step 2, between the load impedance ZL and the source impedance Zs insert a wideband RF impedance matching network, simulation optimization; wherein, wideband RF impedance matching network contains a pair of cascaded parallel LC unit and series LC unit, simulation of load impedance ZL and wideband RF impedance matching network after the impedance Z0 and the input reflection coefficient S11 at this time, its corresponding relationship is: In dB form as: Step 3, when the load impedance ZL and the source impedance Zs between the insertion of wideband RF impedance matching network completely matched, that is, Zo = Zs, at this time the input reflection coefficient is zero, that is, the circuit is completely matched; usually, the wideband circuit in-band can not be completely matched, the in-band reflection coefficient is controlled below-10dB, that is: Step 4, observe the value of S11 in-band in simulation software, if not satisfied, set the parallel LC unit and series LC unit parameter θ value variable range in simulation software, set the optimization target S11 <-10dB, automatic optimization; If the optimization result S11 <-10dB, the target is completed, if the optimization result does not satisfy S11 <-10dB, continue to insert a pair of cascaded parallel LC unit and series LC unit in the wideband RF impedance matching network, repeat step 2 to step 4, until the optimization result S11 <-10dB; Step 5, according to the optimization of θ value, determine the parallel LC unit and series LC unit in the wideband RF impedance matching network represents the parallel element and series element type and element value, that is, the design of wideband RF impedance matching network is completed.

2. The method of claim 1, wherein: The parallel LC unit is a schematic unit described by Verilog A language, used to represent the parallel inductance or parallel capacitance or open circuit in the impedance matching network.

3. The method of claim 1, wherein: The series LC unit is a schematic unit described by Verilog A language, used to represent the series inductance or parallel capacitance or short circuit in the impedance matching network.

4. The method of claim 1, wherein: The characteristic impedance of the parallel LC unit can be expressed as wherein Z0 is the standard reference impedance of the radio frequency system, generally 50 ohms; f is the simulation frequency; f0 is the center frequency of the bandwidth; P i the constant is the ratio of the circumference of a circle to its diameter When θ > 0, Z PLC is proportional to f, which is equivalent to connecting an inductor in parallel, whose inductance is L p = [Z0cot(θ / 2)] / (2*P i *f0); When θ < 0, Z PLC Inversely proportional to f, which is equivalent to connecting a capacitor in parallel, whose capacitance value is C p = [tan(-θ / 2)] / (2 * P i * f0* Z0); When θ = 0, it can be equivalent to open circuit.

5. The method of claim 3, wherein: The characteristic impedance of the series LC unit can be expressed as Wherein, Z0 is the standard reference impedance of RF system, is the simulation frequency; is the center frequency of the bandwidth; When θ ≥ 0, Z SLC Proportional to f, can be equivalent to a string of inductance, inductance value is L s = [Z0tan(θ / 2)] / (2*P i *f0); When θ < 0, Z SLC Inversely proportional to f, which can be equivalent to a series capacitor, whose capacitance value is C s = [cot(-θ / 2)] / (2 * P i * f0* Z0); When θ = 0, it can be equivalent to short circuit.

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