A transmission line transformer with a non-integer square turns ratio

Abstract

The present invention discloses a transmission line transformer with a non-integer square turns ratio, which comprises a winding transformer T1 with an impedance turns ratio of 1:N<supgt;2< / supgt; and a Guanella transformer T2 with an impedance turns ratio of 4:1, where N is an integer greater than or equal to 2; both the winding transformer T1 and the Guanella transformer T2 have a low-impedance port and a high-impedance port; the low-impedance port of the winding transformer T1 is connected in parallel with the high-impedance port of the Guanella transformer T2, and after parallel connection, the overall external low-impedance port of the transmission line transformer is formed; the high-impedance port of the winding transformer T1 is connected in series with the low-impedance port of the Guanella transformer T2, and after series connection, the overall external high-impedance port of the transmission line transformer is formed. The present invention can realize a non-integer square impedance turns ratio transformer, refine the impedance turns ratio step, and at the same time can realize single-ended - differential (balanced) impedance transformation, with a compact structure and flexible impedance turns ratio switching.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency circuits, and particularly relates to a transmission line transformer with a non-integer square turns ratio.

Background Art

[0002] The transmission line transformer has the advantages of wide bandwidth, simple structure, and low cost, and is widely used in short-wave and ultra-short-wave radio frequency circuits. By selecting the power capacity of the transmission line, a large power passing ability can be obtained, and it is particularly suitable for use as an impedance converter of a high-power power amplifier.

[0003] Commonly used transmission transformers include the Ruthoff type, Guanella type, and Toroid type, etc., as Figures 1 - 4 shown. The core structure of the above transformers is a radio frequency transmission line, such as a twisted pair or a coaxial cable. Generally, the two conductors of the transmission line are of equal length and appear in pairs. Its advantage is that the distributed capacitance and inductance between the conductors form a transmission line effect, with good broadband characteristics. At the same time, the electromagnetic field energy is distributed between the two conductors, and the field strength outside the transmission line is weak. This is particularly important for low-frequency applications that require magnetic materials, such as the short-wave and ultra-short-wave frequency bands, and can greatly reduce the requirements for the magnetic saturation intensity and loss of the material. Therefore, it is particularly suitable for low-frequency high-power applications. The typical implementation of the Toroid type is as Figure 4 shown. Its low-impedance port is a differential balanced port, presenting a high impedance to the ground and having a common-mode isolation function, and is particularly suitable for use in push-pull circuits.

[0004] Since the number of segments of the transmission line is N (N≥1) and is an integer, the impedance turns ratio that can be achieved is N 2 :1, that is, 1:1, 4:1, 9:1, etc. The turns ratio has a large step, and it cannot meet the requirements for optimizing the performance of high-power power amplifiers. In recent years, the demand for miniaturization of communication electronic devices has been increasing. High-power power amplifiers are the key and difficult points for miniaturization due to their high power consumption and large heat dissipation space requirements. Reducing the volume of the power amplifier requires on the one hand high-power density devices to support it, and on the other hand an external matching circuit to cooperate and optimize the balance in terms of efficiency and linearity. If the impedance turns ratio step is too large, fine impedance adjustment cannot be achieved, and the requirements for performance optimization cannot be met.

[0005] To refine the impedance turns ratio, Figure 5 and Figure 6 show two transformer topology diagrams with non-integer turns ratios implemented based on the Guanella principle. Among them Figure 5The shown transformer includes a total of 3 coaxial cables 21’, 22’ and 23’. On the side of port 24’, cables 21’ and 22’ are in parallel, and then in series with cable 23’. On the side of port 25’, cable 21’ is in series with cable 22’, and then in parallel with cable 23’. If a load with an impedance of Z is connected to the side of port 25’, the equivalent input impedance of port 24’ is 1.5 2 Z, and the impedance ratio is 2.25 times. Using three coaxial cables can also achieve an impedance ratio of 9:1.

[0006] Figure 6 As shown, 4 coaxial cables 31’ to 34’ are used. On the side of port 35’, cables 31’ and 32’ are in parallel, then in series with 33’. These three cables are combined as one and then in parallel with 34’. On the side of port 36’, cable 31’ is first in series with 32’, then combined as one and in parallel with cable 33’, and finally combined as one and in series with cable 34’. When a load with an impedance of Z is connected to port 35’, the input impedance of port 36’ is Using 4 coaxial cables can also achieve and a ratio of 16:1.

[0007] The above non-integer square ratio transformer can theoretically meet the refined impedance ratio requirements. However, due to the requirement of insulation isolation between cables, in applications with relatively low frequencies and long wavelengths (such as the shortwave band), the length of each cable is relatively long, and it needs to be wound into a spiral shape, and the inter-turn spacing should be as large as possible to reduce the distributed capacitance, which results in a relatively large volume and brings difficulties to the implementation of miniaturization projects. Therefore, it is generally used in the ultra-short wave band with relatively high frequencies.

[0008] In addition, Guanella transformers are mostly directly used for single-ended to single-ended impedance transformation. While high-power power amplifiers generally use push-pull circuits and require single-ended to differential (or push-pull) transformation. To better achieve ground isolation, a section of balun (BALUN) needs to be added, further increasing the volume of the impedance transformation part.

[0009] Figure 4 As shown, the outer conductors of different sections of the winding transformer are in close electrical contact, and single-ended to differential impedance transformation can be achieved without the need for an external balun, with a compact structure. Therefore, it is particularly suitable for low-frequency applications such as shortwaves. However, its working principle is different from that of the Figure 5 、 Figure 6 shown circuit, so the principle cannot be directly applied to achieve non-integer square ratio.

[0010] Another solution to achieve a non-integer square ratio is disclosed in the Chinese invention patent publication CN109754989A, the principle of which is to lengthen the conductor length of the high impedance winding so that the number of turns of the high impedance winding is (2+1 / 2) turns, thereby achieving an impedance ratio of 6.25:1. This method causes the two conductors of the transmission line to have inconsistent lengths, destroying the basic mode of the transmission line transformer, forming a strong induced magnetic flux in the external space, and easily causing magnetic saturation of the magnetic material when the passing power is large. The loss of the magnetic material will also cause heating of the magnetic core, resulting in high transmission loss, which is not suitable for high-power applications.

[0011] At present, there is no compact transmission line transformer with non-integer square ratio suitable for high power application in the short wave frequency band. Therefore, it is necessary to provide a new transmission line transformer with non-integer square ratio to solve the above technical problems. [Summary of the invention]

[0012] The main purpose of the present invention is to provide a transmission line transformer with a non-integer square ratio, which overcomes the shortcomings of the non-integer square ratio transmission line transformer in the short-wave frequency band, such as large volume, unsuitable for miniaturization and high loss.

[0013] The present invention achieves the above-mentioned purpose through the following technical scheme: a transmission line transformer with a non-integer square ratio, comprising an impedance ratio of 1:N 2 A winding transformer T1 and a guanella transformer T2 with an impedance ratio of 4:1, N is an integer greater than or equal to 2; the winding transformer T1 and the guanella transformer T2 both have a low impedance port and a high impedance port; the low impedance port of the winding transformer T1 is connected in parallel with the high impedance port of the guanella transformer T2, and after parallel connection, a total external low impedance port of the transmission line transformer is formed; the high impedance port of the winding transformer T1 is connected in series with the low impedance port of the guanella transformer T2, and after series connection, a total external high impedance port of the transmission line transformer is formed.

[0014] Further, the low impedance port of the winding transformer T1 is composed of a low impedance terminal e and a low impedance terminal f;

[0015] The high impedance port of the winding transformer T1 is composed of a high impedance terminal g and a high impedance terminal h;

[0016] The low impedance terminal e and the high impedance terminal g of the winding transformer T1 are in phase;

[0017] The low impedance port of the guanella transformer T2 is composed of a low impedance terminal i and a low impedance terminal j;

[0018] The low impedance port of the guanella transformer T2 is composed of a high impedance terminal k and a high impedance terminal m;

[0019] The low-impedance terminals i and the high-impedance terminals k of the Guanella transformer T2 are in the same phase.

[0020] Furthermore, the high-impedance port of the winding transformer T1 and the low-impedance port of the Guanella transformer T2 are connected in series in a first series connection method to achieve the impedance transformation ratio; the first series connection method is: the low-impedance terminal i of T2 is connected to the high-impedance terminal h of T1, and the low-impedance terminal j of T2 is grounded; or

[0021] The high-impedance port of the winding transformer T1 and the low-impedance port of the Guanella transformer T2 are connected in series in a second series connection method to achieve the impedance transformation ratio; the second series connection method is: the low-impedance terminal j of T2 is connected to the high-impedance terminal h of T1, and the low-impedance terminal i of T2 is grounded.

[0022] Furthermore, the winding transformer T1 includes N sections of transmission lines TL 1 ~TL N ; each section of the transmission line includes conductors R1 and R2 of equal length; the conductors R1 in the N sections of transmission lines are connected in series end to end, and the starting end of the transmission line TL 1 constitutes the high-impedance terminal g of T1, and the terminal of TL N constitutes the high-impedance terminal h of T1; one ends of the conductors R2 in the N sections of transmission lines are connected in parallel to form the low-impedance terminal e of T1, and the other ends are connected in parallel to form the low-impedance terminal f of T1, and the center points of all the conductors R2 are grounded.

[0023] Furthermore, the Guanella transformer T2 includes two sections of transmission lines TL N+1 and TL N+2 ; each section of the transmission line is composed of conductors R3 and R4 of equal length; one end of the conductor R3 in the transmission line TL N+1 is connected in parallel with one end of the conductor R4 in the transmission line TL N+2 to form the low-impedance terminal i of T2, and one end of the conductor R4 in the transmission line TL N+1 is connected in parallel with one end of the conductor R3 in the transmission line TL N+2 to form the low-impedance terminal j of T2; the other end of the conductor R3 in the transmission line TL N+1 constitutes the high-impedance terminal k of T2, and the other end of the conductor R4 in the transmission line TL N+1 is connected to the other end of the conductor R3 in the transmission line TL N+2 ; the other end of the conductor R4 in the transmission line TL N+2 constitutes the high-impedance terminal m of T2.

[0024] Further, the winding transformer T1 includes N - 1 "U"-shaped coaxial cables and two straight coaxial cables; the N - 1 "U"-shaped coaxial cables are stacked in parallel and their outer conductors are in close contact to form a "U"-shaped cable cluster. The first straight coaxial cable is parallel and closely attached to one straight side of the "U"-shaped cable cluster from below, and the second straight coaxial cable is parallel and closely attached to the opposite straight side of the "U"-shaped cable cluster from above. The outer conductors of the two straight coaxial cables are both in close contact with the outer conductor of the "U"-shaped cable cluster.

[0025] At the open end of the "U"-shaped cable cluster, the inner conductor of the first straight coaxial cable is connected to the inner conductor of the opposite straight side of the lowermost "U"-shaped coaxial cable in the "U"-shaped cable cluster. The inner conductor of the same-side straight side of this layer of "U"-shaped coaxial cable is connected to the inner conductor of the opposite straight side of the upper layer of "U"-shaped coaxial cable, and so on layer by layer until the top layer; the inner conductor of the same-side straight side of the top layer of "U"-shaped coaxial cable is connected to the inner conductor of the second straight coaxial cable on the opposite side.

[0026] In the "U"-shaped cable cluster, the straight-side outer conductors of the "U"-shaped coaxial cables on the same side as the second straight coaxial cable are integrally connected together to form the low-impedance terminal e of T1, and the straight-side outer conductors of the "U"-shaped coaxial cables on the same side as the first straight coaxial cable are integrally connected together to form the low-impedance terminal f of T1; the end of the inner conductor of the first straight coaxial cable close to the arc segment of the "U"-shaped coaxial cable forms the high-impedance terminal g of T1, and the end of the inner conductor of the second straight coaxial cable close to the arc segment of the "U"-shaped coaxial cable forms the high-impedance terminal h of T1; the outer conductors of the "U"-shaped cable cluster are integrally connected together at the arc segment and grounded.

[0027] Further, the Guanella transformer T2 is located above the winding transformer T1. Except for the connections between the terminals, all conductors of the two transmission lines TL N+1 and TL N+2 do not contact T1; the high-impedance port of T2 is located on the open side of the "U"-shaped cable cluster of T1, and the low-impedance port of T2 is located on the arc-end side of the "U"-shaped cable cluster of T1.

[0028] Further, the transmission lines TL N+1 and TL N+2 of the Guanella transformer T2 are coaxial cables; among the two transmission lines,

[0029] the inner conductor of the coaxial cable is the conductor R3 and the outer conductor is the conductor R4; or

[0030] the outer conductor of the coaxial cable is the conductor R3 and the inner conductor is the conductor R4.

[0031] Further, the Guanella transformer T2 further includes an independent wire, and the length of the independent wire is the same as that of the transmission line in the Guanella transformer T2;

[0032] In the first series connection mode, one end of the independent wire is connected to the high-impedance terminal k of T2, and the other end is connected to the low-impedance terminal j of T2 and grounded;

[0033] In the second series connection mode, one end of the independent wire is connected to the high-impedance terminal m of T2, and the other end is connected to the low-impedance terminal i of T2 and grounded.

[0034] Further, it further includes a magnetic core, and the magnetic core includes at least two through rectangular holes and at least two through circular holes; a circular hole is correspondingly arranged above each rectangular hole; the "U"-shaped cable cluster of the winding transformer T1 and the first and second straight coaxial cables are installed in the rectangular holes, and the open end and the arc end of the "U"-shaped cable cluster are conductively connected outside the magnetic core; the transmission lines TL N+1 and TL N+2 are respectively located in two of the circular holes, and the two ends of the transmission line TL N+1 and TL N+2 extend out of the magnetic core and are connected to corresponding conductors.

[0035] Further, the Guanella transformer T2 further includes an independent wire, and the length of the independent wire is the same as that of the transmission line in the Guanella transformer T2;

[0036] In the first series connection mode, one end of the independent wire is connected to the high-impedance terminal k of T2, and the other end is connected to the low-impedance terminal j of T2 and grounded;

[0037] In the second series connection mode, one end of the independent wire is connected to the high-impedance terminal m of T2, and the other end is connected to the low-impedance terminal i of T2 and grounded;

[0038] Three circular holes are arranged side by side in sequence, and the independent wire is arranged in the middle circular hole.

[0039] Compared with the prior art, the beneficial effects of a transmission line transformer with a non-integer square turns ratio of the present invention are as follows: it has the characteristics of compact structure, simple implementation, and flexible impedance turns ratio change. Specifically, by combining a winding transformer and a Guanella transformer, the winding transformer realizes the impedance transformation of the integer part and the single-ended-differential conversion, and the Guanella transformer completes the non-integer turns ratio, which not only ensures a compact structure volume but also can realize the single-ended-differential (balanced) impedance transformation, and has The non-integer square turns ratio refines the step of the impedance turns ratio. Additionally, by changing the series connection order of the high-impedance port of the winding transformer and the low-impedance port of the Guanella transformer, the turns ratio can be conveniently and flexibly switched. This solution is particularly suitable for the miniaturization design and performance index optimization of short-wave high-power amplifiers. Since the two conductors in the transmission lines used in the two transformers in this solution always maintain equal lengths, the external magnetic field intensity of the transmission lines is cancelled out. After introducing magnetic cores in the short-wave or ultra-short-wave frequency bands, the requirements for the magnetic saturation intensity and loss characteristics of magnetic materials are greatly reduced, and the loss will not increase due to the introduction of magnetic materials, thus solving the problem of high loss. and the turns ratio switching; This solution is particularly suitable for the miniaturization design and performance index optimization of short-wave high-power amplifiers. Since the two conductors in the transmission lines used in the two transformers in this solution always maintain equal lengths, the external magnetic field intensity of the transmission lines is cancelled out. After introducing magnetic cores in the short-wave or ultra-short-wave frequency bands, the requirements for the magnetic saturation intensity and loss characteristics of magnetic materials are greatly reduced, and the loss will not increase due to the introduction of magnetic materials, thus solving the problem of high loss.

Description of the Drawings

[0040] Figure 1 is the schematic diagram of the Latham transformer in the prior art;

[0041] Figure 2 is the schematic diagram of the Guanella transformer in the prior art;

[0042] Figure 3 is the schematic diagram of the winding transformer in the prior art;

[0043] Figure 4 is the schematic diagram of the typical implementation method of the winding transformer in the prior art;

[0044] Figure 5 is the schematic diagram of a 2.25:1 transformer based on the Guanella principle in the prior art;

[0045] Figure 6 is a transformer schematic diagram based on the Guanella principle in the prior art;

[0046] Figure 7 is the principle structure block diagram of Embodiment 1 of the present invention;

[0047] Figure 8 is the schematic diagram of the first series connection method in Embodiment 1 of the present invention;

[0048] Figure 9 is the schematic diagram of the second series connection method in Embodiment 1 of the present invention;

[0049] Figure 10 is the implementation structure schematic diagram of the first solution in Embodiment 1 of the present invention;

[0050] Figure 11 is the implementation structure schematic diagram of the second solution in Embodiment 1 of the present invention;

[0051] Figure 12 is the implementation structure schematic diagram of the third solution in Embodiment 1 of the present invention;

[0052] Figure 13 It is a schematic diagram of the implementation structure of the fourth solution in the first embodiment of the present invention;

[0053] Figure 14 It is a schematic diagram of the implementation structure of the second embodiment of the present invention;

[0054] Figure 15 It is a schematic diagram of the magnetic core structure in the third embodiment of the present invention;

[0055] Figure 16 It is a view of the open end of the "U"-shaped cable cluster in the third embodiment of the present invention;

[0056] Figure 17 It is a view of the arc section of the "U"-shaped cable cluster in the third embodiment of the present invention;

[0057] Figure 18 It is a side view of the third embodiment of the present invention;

[0058] Figure 19 It is the real part frequency response of the differential mode impedance in the third embodiment of the present invention;

[0059] Figure 20 It is the imaginary part frequency response of the differential mode impedance in the third embodiment of the present invention;

[0060] Figure 21 It is the common mode impedance amplitude frequency response in the third embodiment of the present invention.

Specific implementation manner

[0061] Embodiment 1:

[0062] This embodiment is a transmission line transformer with a non-integer square turns ratio. As Figure 7 shown, it includes a wound transformer T1 with an impedance turns ratio of 1:N 2 (N is an integer greater than or equal to 2) and a Guanella transformer T2 with an impedance turns ratio of 4:1. The low impedance port 11 of T1 is connected in parallel with the high impedance port 21 of transformer T2. After parallel connection, the external low impedance terminals a and b of the non-integer square turns ratio transformer are formed. The external low impedance port is formed between the external low impedance terminal a and the external low impedance terminal b. The high impedance port 12 of T1 is connected in series with the low impedance port 22 of T2. After series connection, the total external high impedance terminals c and d of the non-integer square turns ratio transformer are formed. The external high impedance port is formed between the external high impedance terminal c and the external high impedance terminal d.

[0063] The principle of the embodiment of the present invention is as Figure 8 and Figure 9 shown.

[0064] Among them, the wound transformer T1 is composed of N sections of transmission lines TL1 ~TL N is composed of. Each transmission line includes two conductors of equal length, conductor R1 and conductor R2. TL 1 ~TL N The N conductors R1 of ~TL are connected in series end to end in sequence, and the starting end 1311 of the conductor R1 of TL 1 forms the high-impedance terminal g of the winding transformer T1, and the terminal 1312 of the conductor R1 of TL N forms the high-impedance terminal h of the winding transformer T1. The first ends 1321 of all N conductors R2 are connected in parallel together as the low-impedance terminal e of the winding transformer T1, and the second ends 1322 of all N conductors R2 are connected in parallel together as the low-impedance terminal f of the winding transformer T1. The center points of all conductors R2 are grounded. The low-impedance port 11 of T1 is formed between the low-impedance terminal e and the low-impedance terminal f, and the high-impedance port 12 of T1 is formed between the high-impedance terminal g and the high-impedance terminal h.

[0065] The Guanella transformer T2 is composed of two sections of transmission lines TL N+1 and TL N+2 is composed of. Each transmission line includes conductors R3 and R4 of equal length. At one end of TL N+1 and TL N+2 (the right side of T2 in the figure), the conductor R3 of TL N+1 is connected in parallel with the conductor R4 of TL N+2 to form the low-impedance terminal i of T2, and the conductor R4 of TL N+1 is connected in parallel with the conductor R3 of TL N+2 to form the low-impedance terminal j of T2; at the other end of TL N+1 and TL N+2 (the left side of T2 in the figure), the conductor R3 of TL N+1 serves as the high-impedance terminal k of T2, the conductor R4 of TL N+1 is connected to the conductor R3 of TL N+2 , and the conductor R4 of TL N+2 serves as the high-impedance terminal m of T2. The low-impedance port 21 of T2 is formed between the low-impedance terminal i and the low-impedance terminal j, and the high-impedance port 22 of T2 is formed between the high-impedance terminal k and the high-impedance terminal m.

[0066] The low-impedance terminals e and f of the winding transformer T1 are connected in parallel with the high-impedance terminals k and m of the Guanella transformer T2 to realize the parallel connection of the low-impedance port 11 and the high-impedance port 22.

[0067] In Figure 8 , the low-impedance port 21 of T2 is connected to the high-impedance port 12 of T1 in the first series connection method, that is, the low-impedance terminal i of T2 is connected to the high-impedance terminal h of T1, and the low-impedance terminal j of T2 is grounded to realize The impedance transformation ratio. The principle is as follows:

[0068] If the voltages of the external low-impedance terminals a and b of the non-integer square transformation ratio transformer with respect to the ground are +V / 2 and -V / 2 respectively, then the voltage of the low-impedance terminal i of T2 with respect to the ground is +V / 2. The voltage of the first end 1321 of all conductors R2 of T1 with respect to the ground is +V / 2, and the voltage of the second end 1322 with respect to the ground is -V / 2. Starting from the terminal 1312 of the conductor R1 in the TL N transmission line, every time a section of the transmission line TL i is passed, the voltage at the starting end of the conductor R1 increases by V, and finally the voltage of the high-impedance terminal g of T1 with respect to the ground is That is, the voltage of the overall external high-impedance terminal c of the transformer with respect to the ground.

[0069] If there is an external current I flowing out from the overall external high-impedance terminal c of the non-integer square transformation ratio transformer, then the current of all conductors R1 of the winding type transformer T1 is I, and the current at the high-impedance terminal h of T1 is also I, and it flows into the high-impedance terminal h. The current amplitude of all conductors R2 of T1 is also I, and the direction is from the first end 1321 to the second end 1322, then the current amplitude at the low-impedance terminal e of T1 is NI, and the direction is into the low-impedance terminal e. At the high-impedance terminal g of T1, the current amplitude is I / 2, and the direction is into the high-impedance terminal g. Therefore, at the overall external high-impedance terminals c and d of the non-integer square transformation ratio transformer, the current amplitude is The direction is into the external high-impedance terminal c and out of the external high-impedance terminal d.

[0070] If the load impedance connected to the ground terminal of the overall external high-impedance terminal c is Z, then the following is satisfied there:

[0071]

[0072] At the overall external low-impedance port, the equivalent input impedance is:

[0073]

[0074] Therefore, the high-low impedance transformation ratio is:

[0075]

[0076] Please refer to Figure 9 , Figure 9 As shown, the low-impedance port 21 of T2 and the high-impedance port 12 of T1 adopt the second series connection method, that is, the low-impedance terminal j of the Guanella transformer T2 is connected to the high-impedance terminal h of T1, and the low-impedance terminal i of T2 is grounded to achieve The impedance transformation ratio. Its principle is similar to the first series connection method. The difference is that the voltage to ground at the low-impedance terminal j of T2 (i.e., the high-impedance terminal h of T1) is -V / 2; the current amplitude at the high-impedance terminal k of T2 is I / 2, and the direction is the direction flowing out of the high-impedance terminal k, resulting in the sign of the final 1 / 2 transformation ratio term becoming negative.

[0077] Based on the above principle, the implementation structure schematic diagram of this embodiment is as Figures 10 - 13 shown, including a winding transformer T1 and a Guanella transformer T2.

[0078] The winding transformer T1 of this embodiment includes N - 1 "U"-shaped coaxial cables 511, 2 straight coaxial cables 512, and 513. The N - 1 "U"-shaped coaxial cables 512 are arranged in parallel and stacked, and the outer conductors of adjacent two "U"-shaped coaxial cables 512 are in close contact, jointly forming a "U"-shaped cable cluster. In this embodiment, the first straight cable 512 is parallel and closely attached to the right straight side (viewed from the open end) of the "U"-shaped cable cluster from below, and the second straight coaxial cable 513 is parallel and closely attached to the left straight side of the "U"-shaped cable cluster from above. The outer conductors of the two straight coaxial cables are in close contact with the outer conductor of the "U"-shaped cable cluster. At the open end of the "U"-shaped cable cluster, one end 5121 of the inner conductor of the first straight coaxial cable 512 is connected to the inner conductor 5111 of the left straight side of the lowermost "U"-shaped coaxial cable, and the inner conductor 5112 of the right straight side of this layer of "U"-shaped cable is connected to the inner conductor 5113 of the left straight side of the upper layer of "U"-shaped coaxial cable, and so on until the top layer. The inner conductor 5114 of the right straight side of the top layer of "U"-shaped coaxial cable is connected to one end 5131 of the inner conductor of the second straight coaxial cable 513 located on the left. At the open end of the "U"-shaped cable cluster, the outer conductors 514 and 515 of the two straight sides of the "U"-shaped coaxial cable are respectively used as the low-impedance terminal e and the low-impedance terminal f of T1, constituting a differential low-impedance port; in the arc section of the "U"-shaped cable cluster, the outer conductor 516 of the "U"-shaped cable cluster is grounded, and the other end 5122 of the inner conductor of the first straight coaxial cable 512 is used as the high-impedance terminal g of the high-impedance port of the winding transformer T1, and the other end 5132 of the inner conductor of the second straight coaxial cable 513 is used as another high-impedance terminal h of the high-impedance port of the winding transformer T1.

[0079] The first solution of this embodiment is as Figure 10 , the Guanella transformer T2 is composed of two straight coaxial cables 521 and 522. Viewed from the open end of the "U"-shaped cable cluster, the straight coaxial cable 521 is placed parallel above the right straight side of the "U"-shaped cable cluster; the straight coaxial cable 522 is placed parallel above the left straight side of the "U"-shaped cable cluster; the outer conductors of the straight coaxial cables 521 and 522 are not in contact with the outer conductor of the "U"-shaped cable cluster.

[0080] In the solution of this embodiment, it is defined that the outer conductor of the coaxial cable is conductor R1 or conductor R3, and the inner conductor is conductor R2 or R4. Then, according to Figure 8 the principle, one end 5211 of the inner conductor of the straight coaxial cable 521 is connected to one end 5221 of the inner conductor of the straight coaxial cable 522. One end 5222 of the outer conductor of the straight coaxial cable 522 and one end 5212 of the outer conductor of the straight coaxial cable 521 are respectively used as the high-impedance terminal k and high-impedance terminal m of T2, forming the high-impedance port of T2. In the arc section of the "U"-shaped cable cluster, the other end 5223 of the inner conductor of the straight coaxial cable 522 is connected to the other end 5214 of the outer conductor of the straight coaxial cable 521, serving as the low-impedance terminal j of T2; the other end 5213 of the inner conductor of the straight coaxial cable 521 is connected to the other end 5224 of the outer conductor of the straight coaxial cable 522, serving as the low-impedance terminal i of T2. The low-impedance terminal j and the low-impedance terminal i form the low-impedance port of T2.

[0081] Figure 10 The solution of the shown embodiment adopts the first series connection method, that is, the low-impedance terminal i of T2 is connected to the high-impedance terminal h of T1, and the low-impedance terminal j of T2 is connected to the outer conductor 516 of the arc section of the "U"-shaped cable cluster to achieve grounding.

[0082] The total externally low-impedance terminals of the transformer are that the externally low-impedance terminal a is directly led out from the low-impedance terminal e of T1, the externally low-impedance terminal b is directly led out from the low-impedance terminal f of T1, and the total externally high-impedance terminal c of the transformer is directly led out from the high-impedance terminal g of T1. The solution of this embodiment can achieve an impedance transformation ratio of (N + 1 / 2) 2 :1.

[0083] The second solution of the embodiment of the present invention is as shown in Figure 11 Shown. Different from the Figure 10 solution, it adopts the second series connection method, that is, the low-impedance terminal j (i.e., the other end 5214 of the outer conductor of the straight coaxial cable 521) of the Guanella transformer T2 is connected to the high-impedance terminal h (i.e., the other end 5132 of the inner conductor of the second straight coaxial cable 513) of the winding transformer T1; the low-impedance terminal i (i.e., the other end 5224 of the outer conductor of the straight coaxial cable 522) of T2 is connected to the outer conductor 516 of the arc section of the "U"-shaped cable cluster to achieve grounding. Other connection methods are the same as those of the first solution. The solution of this embodiment can achieve an impedance transformation ratio of (N - 1 / 2) 2 :1.

[0084] The third solution of Embodiment 1 of the present invention is as shown in Figure 12 Shown. This implementation solution adopts the second series connection method, different from Figure 11The difference of the second solution is that the inner conductors of the two coaxial cables 521 and 522 of the Guanella transformer T2 are defined as conductor R3, and the outer conductors are defined as conductor R4. Then, at the high-impedance end of T2, one end 5221 of the inner conductor of the coaxial cable 522 is the high-impedance terminal k, and one end 5211 of the inner conductor of the coaxial cable 521 is used as the high-impedance terminal m; one end 5222 of the outer conductor of the coaxial cable 522 is connected to one end 5212 of the outer conductor of the coaxial cable 521. At the low-impedance end of T2, the other end 5223 of the inner conductor of the coaxial cable 522 is used as the low-impedance terminal i of T2, and the other end 5213 of the inner conductor of the coaxial cable 521 is used as the low-impedance terminal j of T2. Other connection methods are the same as those of the second solution. The solution of this embodiment can achieve an impedance transformation ratio of (N - 1 / 2) 2 :1.

[0085] The fourth solution of Embodiment 1 of the present invention is as Figure 13 shown. This implementation scheme adopts the first series connection method. The difference from the first solution of Figure 10 is that the inner conductors of the two coaxial cables 521 and 522 of the Guanella transformer T2 are defined as conductor R3, and the outer conductors are defined as conductor R4. The connection method at the high-impedance end of T2 is the same as that of the third solution ( Figure 12 ). At the low-impedance end of T2, the other end 5223 of the inner conductor of the coaxial cable 522 is used as the low-impedance terminal i and is connected to the high-impedance terminal h of the winding transformer T1 (i.e., the other end 5132 of the inner conductor of the second coaxial cable 513). The other end 5213 of the inner conductor of the coaxial cable 521 is used as the low-impedance terminal j and is connected to the arc segment 516 of the "U"-shaped cable cluster of T1 to achieve grounding. The solution of this embodiment can achieve an impedance transformation ratio of (N + 1 / 2) 2 :1.

[0086] Embodiment 2:

[0087] This embodiment has a transmission line transformer with a non-integer square transformation ratio. Its structure is as Figure 14 shown. It includes a winding transformer T1 with an impedance transformation ratio of 1:N 2 and a Guanella transformer T2 with an impedance transformation ratio of 4:1. It is basically similar to the first solution in Embodiment 1, but the difference is that an independent wire 623 is added in the Guanella transformer T2. At the high-impedance port of T2, one end 6231 of the independent wire 623 is connected to the high-impedance terminal k of T2; at the low-impedance port of T2, the other end 6232 of the independent wire 623 is connected to the arc segment 516 of the "U"-shaped cable cluster and then grounded. Other structures and connection relationships in this embodiment are the same as those of the first solution in Embodiment 1, and the impedance transformation ratio is also the same. The addition of the independent wire 623 will improve the balance between the external low-impedance terminal a and the external low-impedance terminal b.

[0088] Similarly, the independent wire 623 added in this embodiment can also be incorporated into the second, third, and fourth solutions of Embodiment 1. In the second solution, one end 6231 of the independent wire 623 is connected to the high-impedance terminal m of T2( Figure 11 ) connection; in the third solution, one end 6231 of the independent wire 623 is connected to the high-impedance terminal m of T2( Figure 12 ) connection; in the fourth solution, one end 6231 of the independent wire 623 is connected to the high-impedance terminal k of T2( Figure 13 ) connection. In the above solutions, the other end 6232 of the independent wire is connected to the arc section 516 of the "U"-shaped cable cluster and then grounded.

[0089] Embodiment 3:

[0090] The transmission line transformer with a non-integer square turns ratio in this embodiment has the same principle, structure, and connection relationship as the second solution in Embodiment 1. The difference is that this embodiment also adds a magnetic core 71 as shown in Figure 15 . The magnetic core is a cuboid structure with two through rectangular holes 711 and 712 in the lower middle part. Circular holes 713 and 714 are provided at the tops of the rectangular holes 711 and 712, and all the circular holes penetrate the entire magnetic core 71. Embodiment 3 is composed of a winding transformer T1 and a Guanella transformer T2, as shown in Figure 16 . Among them, the "U"-shaped cable cluster, the first straight coaxial cable 512, and the second straight coaxial cable 513 of the winding transformer T1 are correspondingly installed in the two rectangular holes 711 and 712, and the straight coaxial cables 521 and 522 of the Guanella transformer T2 are respectively installed in the two circular holes 713 and 714 at the top, as shown in Figure 17 . The ends of all the cables are exposed outside the magnetic core 71 and are connected in the areas 74 and 75 shown in Figure 18 according to the second solution in Embodiment 1.

[0091] In this embodiment, two circular holes are provided. In other embodiments, three can also be arranged side by side, and the independent wire 623 in Embodiment 2 is arranged in the middle circular hole.

[0092] In Embodiment 3, coaxial cables with a diameter of 3 mm and a characteristic impedance of 25 Ω are used to fabricate each section of the cables in the winding transformer and the Guanella transformer. Among them, there are 2 "U"-shaped cables in the winding transformer. The relative permeability of the ferrite of the magnetic core 71 is 100, and the length is between 40 and 60 mm. At the arc section of the "U"-shaped cable cluster, for convenience of connection, the end of the first straight coaxial cable 512 is bent downward, and its inner conductor can be connected to the external circuit system as a high-impedance terminal; after the end of the second straight coaxial cable 513 is bent along the arc of the bottom of the "U" shape, it is respectively connected to the straight coaxial cables 521 and 522 of the Guanella transformer. In theory, this embodiment can achieve an impedance transformation ratio of 2.5 2 :1.

[0093] Perform full-network S-parameter testing on Embodiment 3, and then calculate the differential impedance of the two low-impedance ports to the ground, as shown in Figure 19 , 20 . According to the theoretical transformation ratio relationship, when the high-impedance terminal is connected to a 50 Ω load, the differential impedance is 50 / 6.25 = 8 Ω. After splitting it into two resistances to the ground, each is 4 Ω. The measured results show that in the short-wave frequency band of 2 MHz to 30 MHz, the real part of the differential-mode impedance is 4 ± 0.12 Ω, and the deviation between the two ports is less than 0.1 Ω; the imaginary part shows weak inductance, and better tuning can be achieved by connecting a capacitive reactance in parallel at the port. To fully describe the characteristics of the differential port, attention also needs to be paid to its common-mode impedance to the ground. The measured results are shown in Figure 21 . The amplitude of the lowest common-mode impedance exceeds 40 Ω, which is 10 times that of the differential-mode impedance. It can be seen from the measured results that the impedance transformation ratio of the transmission-line transformer in this embodiment satisfies the non-integer square relationship of 6.25:1, the differential-mode impedance balance is good, the reactance is small, the minimum common-mode impedance is 10 times that of the differential-mode impedance, and the common-mode suppression is good.

[0094] It should be noted that the connection between all cable conductors in the above embodiments can be achieved by means such as direct docking of cables, wire connection, and printed circuit board (PCB). The connection means do not belong to the technical features of the present invention.

[0095] The above are only some embodiments of the present invention. For those of ordinary skill in the art, without departing from the inventive concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A transmission line transformer with a non-integer square turns ratio, characterized in that: It includes a winding transformer T1 with an impedance ratio of 1:N 2 and a Guanella transformer T2 with an impedance ratio of 4:1, where N is an integer greater than or equal to 2; both the winding transformer T1 and the Guanella transformer T2 have a low-impedance port and a high-impedance port; The low-impedance port of the winding transformer T1 is connected in parallel with the high-impedance port of the Guanella transformer T2, and after parallel connection, the overall external low-impedance port of the transmission line transformer is formed; The high-impedance port of the winding transformer T1 is connected in series with the low-impedance port of the Guanella transformer T2, and after series connection, the overall external high-impedance port of the transmission line transformer is formed.

2. The transmission line transformer with a non-integer square turns ratio according to claim 1, characterized in that: The low-impedance port of the winding transformer T1 is composed of a low-impedance terminal e and a low-impedance terminal f; The high-impedance port of the winding transformer T1 is composed of a high-impedance terminal g and a high-impedance terminal h; The low-impedance terminal e and the high-impedance terminal g of the winding transformer T1 are in the same phase; The low-impedance port of the Guanella transformer T2 is composed of a low-impedance terminal i and a low-impedance terminal j; The high-impedance port of the Guanella transformer T2 is composed of a high-impedance terminal k and a high-impedance terminal m; The low-impedance terminal i and the high-impedance terminal k of the Guanella transformer T2 are in the same phase.

3. The transmission line transformer with a non-integer square turns ratio according to claim 2, characterized in that: The high-impedance port of the winding transformer T1 and the low-impedance port of the Guanella transformer T2 are connected in series in a first series connection method to achieve the impedance transformation ratio; the first series connection method is: the low-impedance terminal i of T2 is connected to the high-impedance terminal h of T1, and the low-impedance terminal j of T2 is grounded; or The high-impedance port of the winding transformer T1 is connected in series with the low-impedance port of the Guanella transformer T2 in a second series connection to achieve the impedance transformation ratio; the second series connection method is: the low-impedance terminal j of T2 is connected to the high-impedance terminal h of T1, and the low-impedance terminal i of T2 is grounded.

4. The transmission line transformer with a non-integer square turns ratio according to claim 2 or 3, characterized in that: The winding type transformer T1 includes N sections of transmission lines TL 1 ~TL N ; Each section of the transmission line includes a conductor R1 and a conductor R2 with equal lengths; The conductors R1 in the N sections of transmission lines are connected in series end to end in sequence, and the starting end of the transmission line TL 1 forms the high impedance terminal g of T1, and the terminal of TL N forms the high impedance terminal h of T1; One ends of the conductors R2 in the N sections of transmission lines are connected in parallel to form the low impedance terminal e of T1, and the other ends are connected in parallel to form the low impedance terminal f of T1, and the center points of all the conductors R2 are grounded.

5. The transmission line transformer with a non-integer square turns ratio according to claim 3, characterized in that: The Guanella transformer T2 includes two transmission lines TL of equal length N+1 and TL N+2 ; Each of the transmission lines consists of a conductor R3 and a conductor R4 of equal length; The conductor R3 in the transmission line TL N+1 One end of the conductor R3 in is connected in parallel with one end of the conductor R4 in the transmission line TL N+2 to form the low-impedance terminal i of T2. One end of the conductor R4 in the transmission line TL N+1 is connected in parallel with one end of the conductor R3 in the transmission line TL N+2 to form the low-impedance terminal j of T2; The other end of the conductor R3 in the transmission line TL N+1 forms the high-impedance terminal k of T2. The other end of the conductor R4 in the transmission line TL N+1 is connected to the other end of the conductor R3 in the transmission line TL N+2 . The other end of the conductor R4 in the transmission line TL N+2 forms the high-impedance terminal m of T2.

6. The transmission line transformer with a non-integer square turns ratio according to claim 5, characterized in that: The winding transformer T1 includes N - 1 "U"-shaped coaxial cables and two straight coaxial cables; the N - 1 "U"-shaped coaxial cables are stacked in parallel and their outer conductors are in close contact to form a "U"-shaped cable cluster. Among them, the first straight coaxial cable is parallel and closely attached to one straight side of the "U"-shaped cable cluster from below, and the second straight coaxial cable is parallel and closely attached to the opposite straight side of the "U"-shaped cable cluster from above. The outer conductors of the two straight coaxial cables are both in close contact with the outer conductor of the "U"-shaped cable cluster; At the open end of the "U"-shaped cable cluster, the inner conductor of the first straight coaxial cable is connected to the inner conductor of the opposite straight side of the lowermost "U"-shaped coaxial cable in the "U"-shaped cable cluster. The inner conductor of the same-side straight side of this layer of "U"-shaped coaxial cable is connected to the inner conductor of the opposite straight side of the upper layer of "U"-shaped coaxial cable, and it is pushed up layer by layer until the top layer; the inner conductor of the same-side straight side of the topmost "U"-shaped coaxial cable is connected to the inner conductor of the opposite second straight coaxial cable. In the "U"-shaped cable cluster, the straight outer conductors of the "U"-shaped coaxial cables on the same side as the second straight coaxial cable are integrally connected together to form the low-impedance terminal e of T1, and the straight outer conductors of the "U"-shaped coaxial cables on the same side as the first straight coaxial cable are integrally connected together to form the low-impedance terminal f of T1; one end of the inner conductor of the first straight coaxial cable close to the arc segment of the "U"-shaped coaxial cable forms the high-impedance terminal g of T1, and one end of the inner conductor of the second straight coaxial cable close to the arc segment of the "U"-shaped coaxial cable forms the high-impedance terminal h of T1; the outer conductors of the "U"-shaped cable cluster are integrally connected together at the arc segment and grounded.

7. The transmission line transformer with a non-integer square turns ratio as claimed in claim 6, characterized in that: The Guanella transformer T2 is located above the winding transformer T1. Except for the connections between terminals, all conductors of the two transmission lines TL N+1 and TL N+2 do not contact T1; the high-impedance port of T2 is located on the open side of the "U"-shaped cable cluster of T1, and the low-impedance port of T2 is located on the arc-end side of the "U"-shaped cable cluster of T1.

8. The transmission line transformer with a non-integer square turns ratio as claimed in claim 6, characterized in that: The transmission line TL of the Guanella transformer T2 N+1 and TL N+2 is a coaxial cable; among the two sections of the transmission line the inner conductor of the coaxial cable is the conductor R3 and the outer conductor is the conductor R4; or the outer conductor of the coaxial cable is the conductor R3 and the inner conductor is the conductor R4.

9. The transmission line transformer with a non-integer square turns ratio as claimed in claim 5, characterized in that: the Guanella transformer T2 further includes an independent wire, and the length of the independent wire is the same as the length of the transmission line in the Guanella transformer T2; in the first series connection mode, one end of the independent wire is connected to the high-impedance terminal k of T2, and the other end is connected to the low-impedance terminal j of T2 and grounded; in the second series connection mode, one end of the independent wire is connected to the high-impedance terminal m of T2, and the other end is connected to the low-impedance terminal i of T2 and grounded.

10. The transmission line transformer with a non-integer square turns ratio as claimed in claim 6, characterized in that: It further includes a magnetic core, and the magnetic core includes at least two through rectangular holes and at least two through circular holes; one of the circular holes is correspondingly arranged above each of the rectangular holes; the "U"-shaped cable cluster of the winding type transformer T1 and the first and second straight coaxial cables are installed in the rectangular holes, and the open end and the arc end of the "U"-shaped cable cluster are conductively connected correspondingly outside the magnetic core; the transmission lines TL N+1 and TL N+2 of the Guanella type transformer T2 are respectively located in two of the circular holes, and the two ends of the transmission line TL N+1 and TL N+2 extend outside the magnetic core and are connected to corresponding conductors.

11. The transmission line transformer with a non-integer square turns ratio as claimed in claim 10, characterized in that: the Guanella transformer T2 further includes an independent wire, and the length of the independent wire is the same as the length of the transmission line in the Guanella transformer T2; in the first series connection mode, one end of the independent wire is connected to the high-impedance terminal k of T2, and the other end is connected to the low-impedance terminal j of T2 and grounded; in the second series connection mode, one end of the independent wire is connected to the high-impedance terminal m of T2, and the other end is connected to the low-impedance terminal i of T2 and grounded; three circular holes are arranged side by side in sequence, and the independent wire is arranged in the middle circular hole.

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