CN111029701A - Novel branch line balun - Google Patents
Novel branch line balun Download PDFInfo
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- CN111029701A CN111029701A CN201911414340.8A CN201911414340A CN111029701A CN 111029701 A CN111029701 A CN 111029701A CN 201911414340 A CN201911414340 A CN 201911414340A CN 111029701 A CN111029701 A CN 111029701A
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- matching unit
- impedance matching
- branch line
- balun
- balanced
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- 238000002955 isolation Methods 0.000 claims abstract description 22
- 230000005540 biological transmission Effects 0.000 claims abstract description 18
- 238000003780 insertion Methods 0.000 abstract description 3
- 230000037431 insertion Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P5/00—Coupling devices of the waveguide type
- H01P5/08—Coupling devices of the waveguide type for linking dissimilar lines or devices
- H01P5/10—Coupling devices of the waveguide type for linking dissimilar lines or devices for coupling balanced lines or devices with unbalanced lines or devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P5/00—Coupling devices of the waveguide type
- H01P5/12—Coupling devices having more than two ports
- H01P5/16—Conjugate devices, i.e. devices having at least one port decoupled from one other port
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- Coils Or Transformers For Communication (AREA)
Abstract
The invention discloses a novel branch line balun which comprises a balanced end 1, an unbalanced end 2, an isolation end 3 and a transmission line 5, wherein the balanced end 1 is electrically connected with the unbalanced end 2 through the transmission line 5, an impedance matching unit is arranged on the balanced end 1, and a load resistor 31 is arranged on the isolation end 3. The impedance matching unit is arranged on the balance end 1 to carry out standing wave matching, so that signals of the first balance end 11 and the second balance end 12 are ensured to have relatively stable phase difference in a large input frequency range, the circuit is ensured to have stable insertion loss in a large input frequency range, and the problem that the passband bandwidth of the traditional planar branch line balun is small is solved. Meanwhile, the load resistor 31 is arranged on the isolation end 3, so that the even mode impedance of the balun in the even mode state is improved, and the problem that the isolation degree of the balance end of the traditional plane branch line balun is poor is solved.
Description
Technical Field
The invention relates to the field of communication, in particular to a novel branch line balun.
Background
Balun is a converter of balanced and unbalanced signals and also has the function of impedance transformation. Specifically, balun is a three-port network, which broadly consists of three parts: an unbalanced port, a pair of balanced ports and an isolated port. The working characteristic of the balun is that equal-amplitude and opposite-phase signals are output from two balanced ports, and the balun has the characteristics of good phase balance degree, good amplitude balance degree, good power equal division and the like. The current typical balun structure comprises a branch line balun, a Marchand balun and a Wilkinson power divider balun.
At present, the plane branch line balun is limited by a PCB processing technology, and has the problems of smaller passband bandwidth and poorer isolation.
Disclosure of Invention
In view of this, the present invention provides a novel branch line balun, which solves the problems of a planar branch line balun that the passband bandwidth is small and the isolation is poor by improving the circuit structure.
In order to solve the technical problems, the technical scheme of the invention is to adopt a novel branch line balun which comprises a balanced end, an unbalanced end, an isolation end and a transmission line, wherein the balanced end is electrically connected with the unbalanced end through the transmission line, an impedance matching unit is arranged on the balanced end, and a load resistor is arranged on the isolation end.
Optionally, the balanced terminal includes a first balanced terminal and a second balanced terminal, and the impedance matching unit includes a first impedance matching unit, a second impedance matching unit, a third impedance matching unit, and a fourth impedance matching unit.
Optionally, the first impedance matching unit is electrically connected to the first balanced terminal in series, and the second impedance matching unit is electrically connected to the first balanced terminal in parallel; the third impedance matching unit is electrically connected with the second balanced terminal in series, and the fourth impedance matching unit is electrically connected with the second balanced terminal in parallel.
Optionally, the load resistor is electrically connected to the isolation terminal in series, and the resistance of the load resistor is equal to
Optionally, the characteristic impedance of the first impedance matching unit is
The characteristic impedance of the second impedance matching unit, the third impedance matching unit and the fourth impedance matching unit is Z0。
Optionally, the transmission line comprises a plurality of characteristic impedances of
The resonant transmission line of (1).
The invention has the primary improvement that the novel branch line balun is provided, the impedance matching unit is arranged on the balance end to carry out standing wave matching, so that signals of the first balance end and the second balance end are ensured to have relatively stable phase difference in a larger input frequency range, the circuit is ensured to have stable insertion loss in a larger input frequency range, and the problem that the traditional planar branch line balun is smaller in passband bandwidth is solved. Meanwhile, the load resistor is arranged on the isolation end, so that the even mode impedance of the balun in the even mode state is improved, and the problem that the isolation degree of the balance end of the traditional plane branch line balun is poor is solved.
Drawings
FIG. 1 is a simplified circuit diagram of the novel FPGA-based stub balun of the present invention;
fig. 2 is a simplified circuit diagram of the reference circuit 1;
fig. 3 is a simplified circuit schematic of the reference circuit 2;
fig. 4 and 5 are graphs of simulation results of the present invention.
List of reference numerals
1: balance end 2: unbalanced terminal 3: isolation terminal
11: first balance terminal 12: second balance terminal 41: a first impedance matching unit
42: second impedance matching unit 43: third impedance matching unit 44: fourth impedance matching unit
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the novel branch line balun includes a balanced end 1, an unbalanced end 2, an isolation end 3 and a transmission line 5, where the balanced end 1 is electrically connected to the unbalanced end 2 through the transmission line 5, an impedance matching unit is disposed on the balanced end 1, and a load resistor 31 is disposed on the isolation end 3. Wherein the transmission line 4 comprises a plurality of characteristic impedances of
Resonant transmission line of, Z0Is 50 omega. Specifically, θ of the resonant transmission line is an electrical length corresponding to the center frequency, and is 90 degrees, that is, a 90-degree phase shift is generated after an electrical signal passes through one resonant transmission line.
Further, the balanced terminal 1 includes a first balanced terminal 11 and a second balanced terminal 12, and the impedance matching unit includes a first impedance matching unit 41, a second impedance matching unit 42, a third impedance matching unit 43, and a fourth impedance matching unit 44. Wherein the first impedance matching unit 41 is electrically connected to the first balanced terminal 11 in series, and the second impedance matching unit 42 is electrically connected to the first balanced terminal 11 in parallel; the third impedance matching unit 43 is electrically connected to the second balanced terminal 12 in series, and the fourth impedance matching unit 44 is electrically connected to the second balanced terminal 12 in parallel.
Specifically, in order to increase the passband bandwidth of the balun, the characteristic impedance of the first impedance matching unit 41 is determined to be
The characteristic impedance of the second impedance matching unit 42, the third impedance matching unit 43, and the fourth impedance matching unit 44 is Z0。
Further, the load resistor 31 is electrically connected to the isolation terminal 3 in series, and the resistance value of the load resistor 31 is
For the sake of understanding the working principle of the present invention, taking the input of the electrical signal at the unbalanced terminal 2 as an example, the initial electrical signal is divided into a first electrical signal and a second electrical signal. The first electrical signal is transmitted to the first balanced terminal 11 via three resonant transmission lines and the first impedance matching unit 41, and the second electrical signal is transmitted to the second balanced terminal 12 via one resonant transmission line and the third impedance matching unit 43. At this time, theoretically, the phase of the first electrical signal is shifted by 360 degrees and is the same as the phase of the initial electrical signal, and the phase of the second electrical signal is shifted by 180 degrees and has a phase difference of 180 degrees with the first electrical signal. However, in practical use, since the phase change of the signal cannot reach the theoretical value due to the fact that the input frequency of the signal deviates from the operating center frequency thereof more, the present invention ensures that the first electrical signal and the second electrical signal have a relatively stable phase difference in a larger input frequency range by performing standing wave matching by connecting the second impedance matching unit 42 in parallel at the first balanced terminal 11 and connecting the fourth impedance matching unit 44 in parallel at the second balanced terminal 12.
Accordingly, theoretically, the first electrical signal and the second electrical signal have a phase difference of 180 degrees when the isolated terminal 3 intersects, so that the electrical signals at the isolated terminal 3 can be cancelled out theoretically. However, in actual use, the signal phase change cannot reach the theoretical value due to the fact that the signal input frequency deviates from the working center frequency of the signal input frequency by a large amount, and the load resistor 31 is arranged on the isolation end 3, so that the even-mode impedance of the balun in the even-mode state is improved.
Furthermore, the ground terminal 6 is arranged between the second impedance matching unit 42 and the fourth impedance matching unit 44, so that the balun can further cancel an interference signal between the first balanced terminal 11 and the second balanced terminal 12 while realizing multi-terminal grounding, and the isolation of the balun is effectively improved.
For the sake of understanding, the present invention will be described by comparing the simulation results of the balun structure with those of the reference circuit. FIG. 2 shows the document "minor branched bridge-line bag with bag width enhancement" (J. -L.Li, S. -W.Qu, and Q.Xue Electronics Letters, vol.43, No.17, pp.931-932Reference circuit 1 proposed in aug.2007) simplifies the circuit diagram; fig. 3 shows a simplified circuit schematic of a reference circuit 2 proposed in the document "New broadband base" (h.bex, electronics letters, vol.11, No.2, pp.47-48, jan.1975). If we define that the bandwidth | S21-S31| -0.1 dB in reference circuits 1 and 2 is close to the 3dB line, | S in this invention12-2-S11-20.1dB approaches the 3dB line, as shown in fig. 4 and 5, the bandwidth in the pass band is increased to 54.4% and the isolation is increased to 11.4dB compared with the conventional two reference balun structures. It can be seen that the present invention has significant advantages in both bandwidth and isolation.
The impedance matching unit is arranged on the balance end 1 to carry out standing wave matching, so that signals of the first balance end 11 and the second balance end 12 are ensured to have relatively stable phase difference in a large input frequency range, the circuit is ensured to have stable insertion loss in a large input frequency range, and the problem that the passband bandwidth of the traditional planar branch line balun is small is solved. Meanwhile, the load resistor 31 is arranged on the isolation end 3, so that the even mode impedance of the balun in the even mode state is improved, and the problem that the isolation degree of the balance end of the traditional plane branch line balun is poor is solved.
The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and these modifications and adaptations should be considered within the scope of the invention.
Claims (6)
1. A novel branch line balun comprises a balanced end (1), an unbalanced end (2), an isolated end (3) and a transmission line (5), characterized in that the balanced end (1) is electrically connected with the unbalanced end (2) through the transmission line (5), wherein,
an impedance matching unit is arranged on the balance end (1), and a load resistor (31) is arranged on the isolation end (3).
2. The branch line balun according to claim 1, wherein the balanced terminal (1) comprises a first balanced terminal (11) and a second balanced terminal (12), and the impedance matching unit comprises a first impedance matching unit (41), a second impedance matching unit (42), a third impedance matching unit (43) and a fourth impedance matching unit (44).
3. The branch line balun according to claim 2, wherein the first impedance matching unit (41) is electrically connected in series with the first balanced terminal (11), and the second impedance matching unit (42) is electrically connected in parallel with the first balanced terminal (11);
the third impedance matching unit (43) is electrically connected to the second balanced terminal (12) in series, and the fourth impedance matching unit (44) is electrically connected to the second balanced terminal (12) in parallel.
4. The branch line balun according to claim 3, wherein the load resistor (31) is electrically connected in series with the isolated terminal (3), the load resistor (31) having a resistance value of
5. The branch line balun according to claim 4, wherein the characteristic impedance of the first impedance matching unit (41) is
The characteristic impedance of the second impedance matching unit (42), the third impedance matching unit (43) and the fourth impedance matching unit (44) is Z0。
6. Branch line balun according to claim 5, characterized in that the transmission line (5) comprises a plurality of characteristic impedances of
The resonant transmission line of (1).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911414340.8A CN111029701A (en) | 2019-12-31 | 2019-12-31 | Novel branch line balun |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911414340.8A CN111029701A (en) | 2019-12-31 | 2019-12-31 | Novel branch line balun |
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| CN111029701A true CN111029701A (en) | 2020-04-17 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201911414340.8A Pending CN111029701A (en) | 2019-12-31 | 2019-12-31 | Novel branch line balun |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010154474A (en) * | 2008-12-26 | 2010-07-08 | Tdk Corp | Thin-film balun |
| CN103338019A (en) * | 2013-06-04 | 2013-10-02 | 华为技术有限公司 | A balun circuit |
| CN103531895A (en) * | 2013-09-29 | 2014-01-22 | 华侨大学 | Novel broadband printed dipole antenna with branch wire integrated with feed balun |
| KR20150102310A (en) * | 2014-02-28 | 2015-09-07 | 전자부품연구원 | Wideband microwave balun with high isolation properties |
| CN108270407A (en) * | 2016-12-30 | 2018-07-10 | 通用电气公司 | A kind of planar Balun and a kind of multilayer circuit board |
-
2019
- 2019-12-31 CN CN201911414340.8A patent/CN111029701A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010154474A (en) * | 2008-12-26 | 2010-07-08 | Tdk Corp | Thin-film balun |
| CN103338019A (en) * | 2013-06-04 | 2013-10-02 | 华为技术有限公司 | A balun circuit |
| CN103531895A (en) * | 2013-09-29 | 2014-01-22 | 华侨大学 | Novel broadband printed dipole antenna with branch wire integrated with feed balun |
| KR20150102310A (en) * | 2014-02-28 | 2015-09-07 | 전자부품연구원 | Wideband microwave balun with high isolation properties |
| CN108270407A (en) * | 2016-12-30 | 2018-07-10 | 通用电气公司 | A kind of planar Balun and a kind of multilayer circuit board |
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Application publication date: 20200417 |
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