Broadband LC Balun

Abstract

The invention discloses a broadband LC Balun, and the design of the broadband LC Balun comprises three steps: S1, constructing the structure of the LC Balun, the structure comprises a sub-network A, a sub-network B, a sub-network C and a sub-network D, the sub-networks A, B, C and D are dual-port networks, the sub-network A is electrically connected with the sub-network B, the sub-network C, and the sub-network B is electrically connected with the sub-network D, S2, constructing four topological structures, the four topological structures are respectively a pi-type sub-network 1, a pi-type sub-network 2, a T-type sub-network 1 and a T-type sub-network 2, and the sub-network A, the sub-network B, the sub-network C and the sub-network D respectively select any one of the four topological structures; the invention provides a miniaturized and planar broadband Balun network topology structure which does not need mutual inductance and is composed of an inductor L and a capacitor C with complete lumped parameters, and an ultra-wideband, miniaturized and planar LC Balun can be realized based on the topology structure.

Description

A broadband LC balun Technical Field

[0001] The present invention relates to the field of radio frequency chips, and in particular to a broadband LC balun. Background Art

[0002] Baluns are widely used in modern communication systems. For example, they are required in the design and implementation of components such as balanced mixers, push-pull amplifiers, differential low-noise amplifiers, and antenna feed networks. The development direction of modern communication systems is broadband and miniaturization, so the design direction of baluns is also broadband and miniaturization. In addition, in order to facilitate large-scale production using existing chip processing technology, the design of baluns generally adopts a planar structure. The existing technology usually uses a Marchand balun topology structure based on a coupled transmission line model to implement broadband baluns. Although this model provides a planar and broadband balun, the coupled transmission line used in the model needs to maintain a certain degree of coupling within its operating frequency range. The achievable coupling degree not only increases the complexity of the design, but also limits the operating bandwidth of this type of balun. In addition, the size of products based on this model is large. It is necessary to provide an LC balun that can achieve ultra-broadband, miniaturization, planarity, and does not require mutual inductance. The said balun is the abbreviation of Balance-Unbalance, which means balanced-unbalanced converter.

[0003] Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the object of the present invention is to provide a broadband LC balun, and to provide a network topology structure of a broadband balun composed of an inductor L and a capacitor C that is miniaturized, planar, does not require mutual inductance, and uses fully lumped parameters. Based on this topology structure, an ultra-broadband, miniaturized, planar LC balun can be realized.

[0005] The technical solution is a broadband LC balun. The design of the broadband LC balun includes three steps:

[0006] S1: Construct an LC Balun structure, which includes sub-network A, sub-network B, sub-network C, and sub-network D. Sub-networks A, B, C, and D are all two-port networks. Sub-network A can be electrically connected to sub-network B and sub-network C, and sub-network B can be electrically connected to sub-network D.

[0007] S2: Construct four topological structures, namely π-type subnetwork 1, π-type subnetwork 2, T-type subnetwork 1, and T-type subnetwork 2. The subnetworks A, B, C, and D respectively select any one of the four topological structures;

[0008] S3: Set sub-network parameters.

[0009] The beneficial effects achieved by the present invention are:

[0010] The novel LC Balun topology proposed in the present invention uses only lumped parameter inductors L and capacitors C. The inductors L and capacitors C in the present invention can be implemented using a planar structure or discrete components. That is, the present invention can be implemented using a variety of chip processing technologies, such as complementary metal oxide semiconductors (CMOS), low-temperature co-fired ceramics (LTCC), and a variety of chip packaging technologies, such as low-temperature co-fired ceramics (LTCC), and glass substrates, as well as ordinary PCB processing technologies and external discrete components. No additional mutual inductance components are required, which simplifies the design complexity and realizes the miniaturization of the corresponding components of the present invention. The present invention has ultra-wideband operating performance and excellent amplitude and phase balance performance within the ultra-wideband operating frequency range. In addition, while realizing the Balun function, the present invention also realizes impedance matching between the source impedance and the load impedance. Therefore, the system design of the present invention does not require additional impedance matching components, and its system size can be further reduced. The present invention can realize an ultra-wideband, miniaturized, planar LC Balun. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 is a structural diagram of constructing an LC Balun and four topological structural diagrams of the present invention.

[0012] FIG2 is a schematic diagram of Balun in which sub-networks A, B, C, and D all choose the topological structure of π-type sub-network 1.

[0013] FIG3 is a diagram showing simulation results of the return loss performance of the unbalanced port of implementation case 1 within the operating frequency range.

[0014] FIG4 is a diagram showing simulation results of the insertion loss performance from port 1 to port 2 and from port 1 to port 3 within the operating frequency range of implementation case 1.

[0015] FIG5 is a diagram showing simulation results of the balanced signal amplitude imbalance performance within the operating frequency range of implementation case 1.

[0016] FIG6 is a diagram showing simulation results of the balanced signal phase difference performance within the operating frequency range of the first implementation example.

[0017] FIG7 is a Balun diagram showing a situation in which subnetwork A selects the topology of T-type subnetwork 2, subnetwork B selects the topology of T-type subnetwork 1, and subnetworks C and D both select the topology of π-type subnetwork 2. FIG7 is a diagram showing a situation in which subnetwork A selects the topology of T-type subnetwork 2, subnetwork B selects the topology of T-type subnetwork 1, and subnetworks C and D both select the topology of π

[0018] FIG8 is a diagram showing simulation results of the return loss performance of the unbalanced port of implementation case 2 within the operating frequency range.

[0019] FIG9 is a diagram showing simulation results of the insertion loss performance from port 1 to port 2 and from port 1 to port 3 within the operating frequency range of implementation case 2.

[0020] FIG10 is a diagram showing simulation results of the balanced signal amplitude imbalance performance within the operating frequency range of implementation case 2.

[0021] FIG11 is a diagram showing simulation results of the balanced signal phase difference performance within the operating frequency range of the second implementation example. DETAILED DESCRIPTION

[0022] The aforementioned and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the implementation cases in conjunction with the accompanying drawings. The structural contents mentioned in the following embodiments are all referenced to the drawings in the specification.

[0023] A broadband LC balun provided by the present invention will be described in detail below through embodiments with reference to the accompanying drawings.

[0024] A broadband LC balun is designed in three steps:

[0025] S1: Construct an LC Balun structure, which includes sub-network A, sub-network B, sub-network C, and sub-network D. Sub-networks A, B, C, and D are all two-port networks. Sub-network A can be electrically connected to sub-network B and sub-network C, and sub-network B can be electrically connected to sub-network D.

[0026] S2: Construct four topological structures, namely π-type subnetwork 1, π-type subnetwork 2, T-type subnetwork 1, and T-type subnetwork 2. The subnetworks A, B, C, and D respectively select any one of the four topological structures;

[0027] S3: Set sub-network parameters.

[0028] Step S1: Constructing the structure of LC Balun, which includes sub-network A, sub-network B, sub-network C, and sub-network D. Sub-networks A, B, C, and D are all dual-port networks. The specific contents are as follows:

[0029] The sub-network A is a two-port network. In Figure 1(a), port 1 of sub-network A consists of terminal 1 A and terminal 1′ A Composition, terminal 1′ A For terminal 1 A The reference terminal of subnet A is 2. A and terminal 2′ A Composition, terminal 2' A For terminal 2 AReference terminal, terminal 1′ A and terminal 2′ A The electrical performance is connected within sub-network A;

[0030] The sub-network B is a two-port network. In Figure 1(a), port 1 of sub-network B consists of terminal 1. B and terminal 1′ B Composition, terminal 1′ B For terminal 1 B The reference terminal of sub-network B is terminal 2. B and terminal 2′ B Composition, terminal 2' B For terminal 2 B Reference terminal, terminal 1′ B and terminal 2′ B The electrical performance is connected within the sub-network B;

[0031] The sub-network C is a two-port network. In Figure 1(a), port 1 of the sub-network C consists of terminal 1 C and terminal 1′ C Composition, terminal 1′ C For terminal 1 C The reference terminal of sub-network C is port 2. C and terminal 2′ C Composition, terminal 2' C For terminal 2 C Reference terminal, terminal 1′ C and terminal 2′ C The electrical performance is connected within the sub-network C;

[0032] The sub-network D is a two-port network. In Figure 1(a), port 1 of the sub-network D consists of terminal 1. D and terminal 1′ D Composition, terminal 1′ D For terminal 1 D The reference terminal of subnetwork D is 2. D and terminal 2′ D Composition, terminal 2' D For terminal 2 D Reference terminal, terminal 1′ D and terminal 2′ D The electrical performance is connected within the sub-network D;

[0033] Terminal 2 of port 2 of subnet A A Terminal 1 of port 1 of subnet B B Electrically connected, terminal 2' of port 2 of subnet A A Terminal 2 of subnet C port 2 CElectrically connected, terminal 1′ of port 1 of subnet B B Terminal 1 of port 1 of subnet D D Electrical performance is connected;

[0034] The port 2 of the sub-network B is open, and the terminal 1 of the sub-network C is C , 1′ C , 2′ C are electrically connected to the reference ground G of the present invention, and the terminal 1′ of the sub-network D D , 2 D , 2′ D They are respectively electrically connected to the reference ground G of the present invention.

[0035] The broadband LC Balun further includes three ports, namely ports 1, 2, and 3. Ports 1, 2, and 3 are all unbalanced ports and are single-ended ports. Port 1 is composed of terminals 1 and 1′, port 2 is composed of terminals 2 and 2′, and port 3 is composed of terminals 3 and 3′. Terminals 1′, 2′, and 3′ are reference terminals for terminals 1, 2, and 3, respectively. Terminals 2′ and 3′ are respectively connected to the reference ground G of the present invention. Terminals 2 and 3 constitute the balanced port of the present invention and are differential ports. The balanced port is electrically connected to an external balanced system, and port 1 is electrically connected to an external unbalanced system.

[0036] As shown in FIG1(a), the unbalanced port 1 is electrically connected to the port 1 of the sub-network A. At the same time, the terminal 1 is electrically connected to the signal of the external unbalanced system, and the terminal 1′ is electrically connected to the reference ground of the external unbalanced system. The unbalanced load impedance of the external unbalanced system at the port 1 of the present invention is Z UB , its impedance value is Z UB =R UB +jX UB , where R UB is the real part of the unbalanced load impedance, X UB is the imaginary part of the unbalanced load impedance value, j is the imaginary unit, j 2 =-1;

[0037] The terminal 2 is electrically connected to the terminal 2 of the sub-network C port 2 C , terminal 3 can be electrically connected to terminal 1 of port 1 of sub-network D D At the same time, terminals 2 and 3 are electrically connected to the balanced signal of the external balanced system. If the external balanced system has a reference ground, terminals 2' and 3' are electrically connected to the reference ground of the external balanced system. If the external balanced system does not have a reference ground, terminals 2' and 3' are open circuit to the outside, and the balanced load impedance presented by the external balanced system at the balanced port of the present invention is Z B , its impedance value is Z B=R B +jX B , R B is the real part of the balanced load impedance, X B is the imaginary part of the balanced load impedance value.

[0038] Step S2: constructing four topological structures, which are π-type subnetwork 1, π-type subnetwork 2, T-type subnetwork 1, and T-type subnetwork 2. The specific contents of selecting any one of the four topological structures for each of the subnetworks A, B, C, and D are as follows:

[0039] The sub-networks A, B, C, and D can respectively select any one of the four topological structures (b), (c), (d), and (e) in FIG1 ;

[0040] The specific topological structure of the π-type sub-network 1 is as follows: As shown in FIG1(b), a two-port sub-network is constructed, and the port 1 of the π-type sub-network 1 is composed of terminal 1. b and terminal 1′ b Composition, terminal 1′ b For terminal 1 b The reference terminal of the π-type sub-network 1 is the port 2. b and terminal 2′ b Composition, terminal 2' b For terminal 2 b Reference terminal, terminal 1′ b and terminal 2′ b The electrical properties inside the sub-network are connected, and the inductor L1 is connected in series to the sub-network terminal 1 b and 2 b Between, capacitor C1 is connected in series to the sub-network terminal 1 b and 1′ b Between, capacitor C2 is connected in series to the sub-network terminal 2 b and 2′ b A π-type sub-network 1 is formed by using capacitor C1, inductor L1 and capacitor C2;

[0041] The specific topology of the π-type sub-network 2 is as follows: As shown in FIG1(c), a two-port sub-network is constructed, and port 1 of the π-type sub-network 2 is composed of terminal 1. c and terminal 1′ c Composition, terminal 1′ c For terminal 1 c The reference terminal of the π-type sub-network 2 is the port 2 of the c and terminal 2′ c Composition, terminal 2' c For terminal 2 c Reference terminal, terminal 1′ c and terminal 2′ cThe sub-network is electrically connected internally, and capacitor C3 is connected in series to the sub-network terminal 1. c and 2 c Between, inductor L2 is connected in series to the sub-network terminal 1 c and 1′ c Between, inductor L3 is connected in series to the sub-network terminal 2 c and 2′ c A π-type sub-network 2 is formed by using the inductor L2, the capacitor C3, and the inductor L3;

[0042] The specific topology of the T-type sub-network 1 is as follows: As shown in FIG1(d), a two-port sub-network is constructed, and the port 1 of the T-type sub-network 1 is composed of terminal 1. d and terminal 1′ d Composition, terminal 1′ d For terminal 1 d The reference terminal of the T-type sub-network 1 is the port 2. d and terminal 2′ d Composition, terminal 2' d For terminal 2 d Reference terminal, terminal 1′ d and terminal 2′ d The sub-network is electrically connected, and the inductors L4 and L5 are connected in series to the sub-network terminals 1 and 2. d and 2 d The capacitor C4 is connected in series with the connection point of the inductor L4 and the inductor L5 and the terminal 1′. d A T-type sub-network 1 is formed by using inductor L4, capacitor C4 and inductor L5;

[0043] The specific topology of the T-type sub-network 2 is as follows: As shown in FIG1(e), a two-port sub-network is constructed, and the port 1 of the T-type sub-network 2 is composed of terminal 1. e and terminal 1′ e Composition, terminal 1′ e For terminal 1 e The reference terminal of T-type sub-network 2 is port 2. e and terminal 2′ e Composition, terminal 2' e For terminal 2 e Reference terminal, terminal 1′ e and terminal 2′ e The sub-network is electrically connected internally, and capacitors C5 and C6 are connected in series to the sub-network terminal 1. e and 2 e Inductor L6 is connected in series with the connection point of capacitors C5 and C6 and terminal 1′ e A T-type sub-network 2 is formed by using capacitor C5, inductor L6 and capacitor C6.

[0044] The specific contents of step S3: setting sub-network parameters are as follows:

[0045] S3.1: Set sub-network parameters according to load conditions:

[0046] S3.1.1: Set the Balun target center operating frequency to f0, then its corresponding angular frequency is ω0 = 2×π×f0, and set the load impedance value of the unbalanced port to Z UN =R UN +jX UN , the balanced load impedance of the balanced port is Z B =R B +jX B ;

[0047] S3.1.2: Set the characteristic parameters of sub-networks A, B, C, and D to be Z respectively 0A , Z 0B , Z 0C , Z 0D , where Z 0A , Z 0B , Z 0C and Z 0D are all real numbers, and Z 0C =Z 0D ;

[0048] S3.2: Calculate Z 0A Value:

[0049] S3.2.1: At the center frequency f0, if Z UN and Z B are all real numbers, then determine

[0050] S3.2.2: At the center frequency f0, if Z UN is a real number, Z B is a plural number, in the present invention, the balanced port of the Balun and the balanced load Z B Adding a matching network between the two can make the load impedance Z balanced. B After passing through the matching network, the load impedance value Z presented at the balanced port of the Balun of the present invention is B2 When the center frequency f0 is a real number, then determine

[0051] S3.2.3: At the center frequency f0, if Z UN is plural, Z B is a real number, and the unbalanced port of the Balun of the present invention and the unbalanced load impedance Z UN Adding a matching network between the two can make the unbalanced load impedance ZUN After passing through the matching network, the load impedance value Z of the unbalanced port of the Balun of the present invention is presented. UN3 When the center frequency f0 is a real number, then determine

[0052] S3.2.4: At the center frequency f0, if Z UN and Z B are not real numbers. In the present invention, the unbalanced port of Balun and the unbalanced load impedance Z UN Adding a matching network 1 between the two can make the unbalanced load impedance Z UN After passing through the matching network 1, the load impedance value Z of the unbalanced port of the Balun of the present invention is presented. UN4 At the center frequency point f0 is a real number. Similarly, at the balanced port of the Balun of the present invention and the balanced load Z B Adding another matching network 2 between the two can make the load impedance Z balanced. B After passing through the matching network 2, the load impedance value Z of the balanced port of the Balun of the present invention is presented. B4 When the center frequency f0 is a real number, then determine

[0053] S3.3: Z 0B and Z 0C The value of can be chosen arbitrarily as long as it meets the requirements of S3.1 and S3.2 above;

[0054] S3.4: For operation at center frequency f0, with characteristic parameter Z 0X In the four topologies of Figure 1(b), (c), (d), and (e), the inductance values ​​of all inductors are the same and the capacitance values ​​of all capacitors are the same, that is, L 1X =L 2X =L 3X =L 4X =L 5X =L 6X , C 1X =C 2X =C 3X =C 4X =C 5X =C 6X , the inductance value is unified with L X , the capacitance value is uniformly C X Indicates that L X and C X The calculation formulas are: L X =Z 0X / ω0,C X =1 / ω0Z 0X ;

[0055] For the case of working at the center frequency f0, with characteristic parameter Z 0A The inductance and capacitance values ​​of the four topologies in Figure 1(b), (c), (d), and (e) are: L A =Z 0A / ω0,C A =1 / ω0Z 0A ,Subnetwork A chooses any one of the four topologies in Figure 1(b), (c), (d), and (e);

[0056] For the case of a central frequency f0, with characteristic parameter Z 0B The inductance and capacitance values ​​of the four topologies in Figure 1(b), (c), (d), and (e) are: L B =Z 0B / ω0,C B =1 / ω0Z 0B ,Subnetwork B chooses any one of the four topologies in Figure 1(b), (c), (d), and (e);

[0057] For the case of working at the center frequency f0, with characteristic parameter Z 0C The inductance and capacitance values ​​of the sub-network C in Figure 1(b), (c), (d), and (e) are as follows: L C =Z 0C / ω0,C C =1 / ω0Z 0C ,Subnetwork C chooses any one of the four topologies in Figure 1(b), (c), (d), and (e);

[0058] For the case of working at the center frequency f0, with characteristic parameter Z 0D The inductance and capacitance values ​​of the four topological structures in Figure 1(b), (c), (d), and (e) are: L D =Z 0D / ω0,C D =1 / ω0Z 0D ,Subnetwork D chooses any one of the four topologies in Figure 1(b), (c), (d), and (e);

[0059] The present invention has a total of 256 topological structures. The performance of the Balun of the present invention composed of each topological structure is different. In actual design, it is necessary to select a certain topological structure according to specific design requirements.

[0060] Perform instance verification:

[0061] Implementation Case 1: Balun with a central operating frequency of 15 GHz and balanced and unbalanced load impedance values ​​of 100 Ω and 50 Ω respectively;

[0062] According to the design method, the values ​​of the lumped parameters L and C of each sub-network are:

[0063] L A =0.7503nH, C A =0.1501pF, L B =0.0884nH, C B =1.2732pF, L C =L D =6.3662nH, C C =C D =0.0177pF;

[0064] According to the above parameters, if sub-networks A, B, C, and D all choose the topology of Figure 1(b), then according to the scheme of the present invention, the schematic diagram of the designed Balun is shown in Figure 2. In Figure 2, L A1 =L A , L B1 =L B , L C1 =L D1 =L C ,C A1 =C A2 =C A ,C B1 =C B2 =C B ,C C1 =C C2 =C D1 =C D2 =C C , Figure 3 is the simulation result of the return loss performance of the unbalanced port of Implementation Case 1 within the operating frequency range, Figure 4 is the simulation result of the insertion loss performance from port 1 to port 2 and from port 1 to port 3 of Implementation Case 1 within the operating frequency range, Figure 5 is the simulation result of the amplitude imbalance performance of the balanced signal of Implementation Case 1 within the operating frequency range, and Figure 6 is the simulation result of the phase difference performance of the balanced signal of Implementation Case 1 within the operating frequency range;

[0065] As shown in Figures 3-6, according to the design of the present invention, the frequency range in which the return loss of the unbalanced port is greater than 10dB is 0.895-18.33GHz, and the relative bandwidth is 181.4%. Within this bandwidth, the amplitude difference of the Balun balanced signal is 0dB, and the absolute value of the phase difference is 180°. It can be seen that within the relative bandwidth of up to 181.4%, the Balun of the present invention provides excellent Balun performance.

[0066] Implementation Case 2: Balun with a central operating frequency of 15 GHz and balanced and unbalanced load impedance values ​​of 100 Ω and 50 Ω respectively;

[0067] The design goal of Case 2 is the same as that of Case 1. The values ​​of L and C calculated in Case 1 are also applicable to Case 2. In Case 2, sub-network A selects the topology of Figure 1(e), sub-network B selects the topology of Figure 1(d), and sub-networks C and D both select the topology of Figure 1(c). According to the scheme of the present invention, the schematic diagram of the designed Balun is shown in Figure 7. L A2 =L A , L B2 =L B3 =L B , L C2 =L C3 =L D2 =L D3 =L C , C A3 =C A4 =C A , C B3 =C B , C C3 =C D3 =C C , Figure 8 is a simulation result of the return loss performance of the unbalanced port of Implementation Case 2 within the operating frequency range, Figure 9 is a simulation result of the insertion loss performance from port 1 to port 2 and from port 1 to port 3 of Implementation Case 2 within the operating frequency range, Figure 10 is a simulation result of the amplitude imbalance performance of the balanced signal of Implementation Case 2 within the operating frequency range, and Figure 11 is a simulation result of the phase difference performance of the balanced signal of Implementation Case 2 within the operating frequency range;

[0068] As can be seen from Figures 8-11, according to the solution of the present invention, the frequency range in which the unbalanced port return loss of this design is greater than 10dB is 12.35-170.0GHz, and the relative bandwidth is 172.9%. Within this bandwidth, the amplitude difference of the Balun balanced signal is 0dB, and the absolute value of the phase difference is 180°. It can be seen that within a relative bandwidth of up to 172.9%, the Balun of the present invention provides excellent Balun performance.

[0069] The present invention provides a broadband LC balun, and provides a network topology structure of a broadband balun that is miniaturized, planar, does not require mutual inductance, and uses an inductor L and a capacitor C with completely lumped parameters. Based on this topology structure, an ultra-broadband, miniaturized, planar LC balun can be realized.

Claims

1. A broadband LC balun, characterized in that: The design of the broadband LC balun includes three steps: S1: Construct an LC Balun structure, which includes sub-network A, sub-network B, sub-network C, and sub-network D. Sub-networks A, B, C, and D are all two-port networks. Sub-network A can be electrically connected to sub-network B and sub-network C, and sub-network B can be electrically connected to sub-network D. S2: Construct four topological structures, namely π-type subnetwork 1, π-type subnetwork 2, T-type subnetwork 1, and T-type subnetwork 2. The subnetworks A, B, C, and D respectively select any one of the four topological structures; S3: Set sub-network parameters; Balun is the abbreviation of Balance-Unbalance, which means a balanced-unbalanced converter.

2. The broadband LC balun according to claim 1, wherein: Step S1: Constructing the structure of LC Balun, which includes sub-network A, sub-network B, sub-network C, and sub-network D. Sub-networks A, B, C, and D are all dual-port networks. The specific contents are as follows: The sub-network A is a two-port network, and port 1 of the sub-network A consists of terminal 1 A and terminal 1′ A Composition, terminal 1′ A For terminal 1 A The reference terminal of subnet A is 2. A and terminal 2′ A Composition, terminal 2' A For terminal 2 A Reference terminal, terminal 1′ A and terminal 2′ A The electrical performance is connected within sub-network A; The sub-network B is a two-port network, and port 1 of the sub-network B is connected to terminal 1. B and terminal 1′ B Composition, terminal 1′ B For terminal 1 B The reference terminal of sub-network B is terminal 2. B and terminal 2′ B Composition, terminal 2' B For terminal 2 B Reference terminal, terminal 1′ B and terminal 2′ B The electrical performance is connected within the sub-network B; The sub-network C is a two-port network, and port 1 of the sub-network C is composed of terminal 1 C and terminal 1′ C Composition, terminal 1′ C For terminal 1 C The reference terminal of sub-network C is port 2. C and terminal 2′ C Composition, terminal 2' C For terminal 2 C Reference terminal, terminal 1′ C and terminal 2′ C The electrical performance is connected within the sub-network C; The sub-network D is a two-port network, and port 1 of the sub-network D is composed of terminal 1 D and terminal 1′ D Composition, terminal 1′ D For terminal 1 D The reference terminal of subnetwork D is 2. D and terminal 2′ D Composition, terminal 2' D For terminal 2 D Reference terminal, terminal 1′ D and terminal 2′ D The electrical performance is connected within the sub-network D; Terminal 2 of port 2 of subnet A A Terminal 1 of port 1 of subnet B B Electrically connected, terminal 2' of port 2 of subnet A A Terminal 2 of subnet C port 2 C Electrically connected, terminal 1′ of port 1 of subnet B B Terminal 1 of port 1 of subnet D D Electrical performance is connected; The port 2 of the sub-network B is open, and the terminal 1 of the sub-network C is C , 1′ C , 2′ C are electrically connected to the reference ground G of the present invention, and the terminal 1′ of the sub-network D D , 2 D , 2′ D They are respectively electrically connected to the reference ground G of the present invention.

3. The broadband LC balun according to claim 2, wherein: The broadband LC Balun further includes three ports, namely ports 1, 2, and 3. Ports 1, 2, and 3 are all unbalanced ports and are single-ended ports. Port 1 is composed of terminals 1 and 1′, port 2 is composed of terminals 2 and 2′, and port 3 is composed of terminals 3 and 3′. Terminals 1′, 2′, and 3′ are reference terminals for terminals 1, 2, and 3, respectively. Terminals 2′ and 3′ are respectively connected to the reference ground G of the present invention. Terminals 2 and 3 constitute the balanced port of the present invention and are differential ports. The balanced port is electrically connected to an external balanced system, and port 1 is electrically connected to an external unbalanced system. The unbalanced port 1 is electrically connected to the port 1 of the sub-network A. At the same time, the terminal 1 is electrically connected to the signal of the external unbalanced system, and the terminal 1′ is electrically connected to the reference ground of the external unbalanced system. The unbalanced load impedance presented by the external unbalanced system at the port 1 of the present invention is Z UN , its impedance value is Z UN =R UN +jX UN , where R UN is the real part of the unbalanced load impedance, X UN is the imaginary part of the unbalanced load impedance value, j is the imaginary unit, j 2 =-1; The terminal 2 is electrically connected to the terminal 2 of the sub-network C port 2 C , terminal 3 can be electrically connected to terminal 1 of port 1 of sub-network D D At the same time, terminals 2 and 3 are electrically connected to the balanced signal of the external balanced system. If the external balanced system has a reference ground, terminals 2' and 3' are electrically connected to the reference ground of the external balanced system. If the external balanced system does not have a reference ground, terminals 2' and 3' are open circuit to the outside, and the balanced load impedance presented by the external balanced system at the balanced port of the present invention is Z B , its impedance value is Z B =R B +jX B , R B is the real part of the balanced load impedance, X B is the imaginary part of the balanced load impedance value.

4. The broadband LC balun according to claim 1, wherein: Step S2: constructing four topological structures, which are π-type subnetwork 1, π-type subnetwork 2, T-type subnetwork 1, and T-type subnetwork 2. The specific contents of selecting any one of the four topological structures for each of the subnetworks A, B, C, and D are as follows: The specific topological structure of the π-type sub-network 1 is as follows: a two-port sub-network is constructed, and the port 1 of the π-type sub-network 1 is composed of terminal 1 b and terminal 1′ b Composition, terminal 1′ b For terminal 1 b The reference terminal of the π-type sub-network 1 is the port 2. b and terminal 2′ b Composition, terminal 2' b For terminal 2 b Reference terminal, terminal 1′ b and terminal 2′ b The electrical properties inside the sub-network are connected, and the inductor L1 is connected in series to the sub-network terminal 1 b and 2 b Between, capacitor C1 is connected in series to the sub-network terminal 1 b and 1′ b Between, capacitor C2 is connected in series to the sub-network terminal 2 b and 2′ b A π-type sub-network 1 is formed by using capacitor C1, inductor L1 and capacitor C2; The specific topological structure of the π-type sub-network 2 is as follows: a two-port sub-network is constructed, and port 1 of the π-type sub-network 2 is composed of terminal 1 c and terminal 1′ c Composition, terminal 1′ c For terminal 1 c The reference terminal of the π-type sub-network 2 is the port 2 of the c and terminal 2′ c Composition, terminal 2' c For terminal 2 c Reference terminal, terminal 1′ c and terminal 2′ c The sub-network is electrically connected internally, and capacitor C3 is connected in series to the sub-network terminal 1. c and 2 c Between, inductor L2 is connected in series to the sub-network terminal 1 c and 1′ c Between, inductor L3 is connected in series to the sub-network terminal 2 c and 2′ c A π-type sub-network 2 is formed by using the inductor L2, the capacitor C3, and the inductor L3; The specific topology of the T-type sub-network 1 is as follows: a two-port sub-network is constructed, and the port 1 of the T-type sub-network 1 is composed of terminal 1 d and terminal 1′ d Composition, terminal 1′ d For terminal 1 d The reference terminal of the T-type sub-network 1 is the port 2. d and terminal 2′ d Composition, terminal 2' d For terminal 2 d Reference terminal, terminal 1′ d and terminal 2′ d The sub-network is electrically connected, and the inductors L4 and L5 are connected in series to the sub-network terminals 1 and 2. d and 2 d The capacitor C4 is connected in series with the connection point of the inductor L4 and the inductor L5 and the terminal 1′. d A T-type sub-network 1 is formed by using inductor L4, capacitor C4 and inductor L5; The specific topology of the T-type sub-network 2 is as follows: a two-port sub-network is constructed, and the port 1 of the T-type sub-network 2 is composed of terminal 1 e and terminal 1′ e Composition, terminal 1′ e For terminal 1 e The reference terminal of T-type sub-network 2 is port 2. e and terminal 2′ e Composition, terminal 2' e For terminal 2 e Reference terminal, terminal 1′ e and terminal 2′ e The sub-network is electrically connected internally, and capacitors C5 and C6 are connected in series to the sub-network terminal 1. e and 2 e Inductor L6 is connected in series with the connection point of capacitors C5 and C6 and terminal 1′ e A T-type sub-network 2 is formed by using capacitor C5, inductor L6 and capacitor C6.

5. The broadband LC balun according to claim 1, wherein: The specific contents of step S3: setting sub-network parameters are as follows: S3.1: Set sub-network parameters according to load conditions: S3.1.1: Set the Balun target center operating frequency to f0, then its corresponding angular frequency is ω0 = 2 × π × f0, and set the load impedance value of the unbalanced port to Z UN =R UN +jX UN , the balanced load impedance of the balanced port is Z B =R B +jX B ; S3.1.2: Set the characteristic parameters of sub-networks A, B, C, and D to be Z respectively 0A , Z 0B , Z 0C , Z 0D , where Z 0A , Z 0B , Z 0C and Z 0D are all real numbers, and Z 0C =Z 0D ; S3.2: Calculate Z 0A Value: S3.2.1: At the center frequency f0, if Z UN and Z B are all real numbers, then determine S3.2.2: At the center frequency f0, if Z UN is a real number, Z B is a plural number, in the present invention, the balance port of the Balun and the balance load Z B Adding a matching network between the two can make the load impedance Z balanced. B After passing through the matching network, the load impedance value Z of the balanced port of the Balun of the present invention is presented. B2 When the center frequency f0 is a real number, then determine S3.2.3: At the center frequency f0, if Z UN is plural, Z B is a real number, and the unbalanced port of the Balun of the present invention and the unbalanced load impedance Z UN Adding a matching network between the two can make the unbalanced load impedance Z UN After passing through the matching network, the load impedance value Z of the unbalanced port of the Balun of the present invention is presented. UN3 When the center frequency f0 is a real number, then determine S3.2.4: At the center frequency f0, if Z UN and Z B are not real numbers. In the present invention, the unbalanced port of Balun and the unbalanced load impedance Z UN Adding a matching network 1 between the two can make the unbalanced load impedance Z UN After passing through the matching network 1, the load impedance value Z of the unbalanced port of the Balun of the present invention is presented. UN4 At the center frequency point f0 is a real number. Similarly, at the balanced port of the Balun of the present invention and the balanced load Z B Adding another matching network 2 between the two can make the load impedance Z balanced. B After passing through the matching network 2, the load impedance value Z of the balanced port of the Balun of the present invention is presented. B4 When the center frequency f0 is a real number, then determine S3.3: Z 0B and Z 0C The value of can be chosen arbitrarily as long as it meets the requirements of S3.1 and S3.2 above; S3.4: For operation at center frequency f0, with characteristic parameter Z 0X In the above four topologies, the inductance values ​​of all inductors are the same and the capacitance values ​​of all capacitors are the same, that is, L 1X =L 2X =L 3X =L 4X =L 5X =L 6X , C 1X =C 2X =C 3X =C 4X =C 5X =C 6X , the inductance value is unified with L X , the capacitance value is uniformly C X Indicates that L X and C X The calculation formulas are: L X =Z 0X / ω0,C X =1 / ω0Z 0X ; For the case of working at the center frequency f0, with characteristic parameter Z 0A The inductance and capacitance values ​​of the sub-network A in the above four topologies are: L A =Z 0A / ω0,C A =1 / ω0Z 0A ,Subnetwork A chooses any one of the four aforementioned topologies; For the case of working at the center frequency f0, with characteristic parameter Z 0B The inductance and capacitance values ​​of the sub-network B in the above four topologies are: L B =Z 0B / ω0,C B =1 / ω0Z 0B ,Subnetwork B chooses any one of the four aforementioned topologies; For the case of working at the center frequency f0, with characteristic parameter Z 0C The inductance and capacitance values ​​of the sub-network C in the above four topologies are: L C =Z 0C / ω0,C C =1 / ω0Z 0C ,Subnetwork C selects any one of the four aforementioned topologies; For the case of working at the center frequency f0, with characteristic parameter Z 0D The inductance and capacitance values ​​of the sub-network D in the above four topologies are: L D =Z 0D / ω0,C D =1 / ω0Z 0D , sub-network D selects any one of the four topologies mentioned above.

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