A small dual-frequency branch line coupler with equal phase difference

Abstract

The present invention discloses a small dual-frequency branch line coupler with equal phase difference, and the specific scheme is as follows: it includes a folded dual branch line, an open / short circuit loaded parallel branch and four 50 ohm input / output ports; the folded dual branch line includes a first transmission line, a second transmission line, a third transmission line and a fourth transmission line; the open / short circuit loaded parallel branch includes a first open / short circuit loaded transmission line, a second open / short circuit loaded transmission line, a third open / short circuit loaded transmission line and a fourth open / short circuit loaded transmission line; the first open / short circuit loaded transmission line includes a first bent transmission line, a first winding open line and a first short circuit line; the second open / short circuit loaded transmission line includes a second bent transmission line, a second winding open line and a second short circuit line. The device can achieve small size, dual frequency band, equal phase difference, and has the characteristics of output ports on the same side.

Description

Technical Field

[0001] The invention belongs to the field of electronic technology and relates to a microwave device, in particular to a small dual-frequency branch line coupler with equal phase difference. Background Art

[0002] In recent years, with the development of microwave and millimeter wave technology, the requirements for technical indicators in the fields of communication, navigation, military electronic countermeasures and radar are increasing, making the design difficulty of microwave devices more and more difficult. In different application scenarios, the design requirements for microwave devices are also different. For example: in mobile communication systems, since different networks have specific frequency domain coverage, this puts forward the design of microwave devices with dual-frequency or multi-frequency and wide-range controllable frequency ratio indicators; in various phased array radar systems, due to the large number of antenna units, this requires microwave devices to have the characteristics of small size and large power capacity.

[0003] As a typical microwave passive device, coupler is widely used in radio frequency circuits and is a basic module of microwave integrated circuits. Traditional branch line couplers have the function of equal power output and fixed output phase difference, but they also have many limitations. For example, the bandwidth of traditional branch line couplers is only 10%, and they work at a single frequency, which cannot meet the needs of modern multi-band and wide-band operation, and they also have disadvantages such as large size. The rapid development of wireless communication systems requires that each component inside the system can work within a multi-frequency and wide frequency ratio range. Some dual-frequency microwave systems need to have the same working state at each frequency, that is, the coupler is required to not only realize dual-frequency operation, but also provide equal phase difference output in each frequency band, while most traditional dual-frequency couplers cannot provide equal output phase. On the other hand, with the rapid development of integrated circuit technology towards miniaturization, higher and higher requirements are put forward for the miniaturization of communication systems. However, traditional couplers cannot meet the above requirements. Therefore, improving the performance of couplers while reducing the size of couplers has become a topic worth studying. The small dual-frequency coupler with equal phase difference has the characteristics of small size, dual frequency band, equal phase difference, low cost and easy processing. At the same time, because its coupling end and through end are on the same side, when the coupler is applied to microwave circuits, the circuit layout can be simplified. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention discloses a small dual-frequency branch line coupler with equal phase difference, which is characterized by comprising a folded double branch line, an open / short circuit loaded parallel branch and four 50 ohm ports.

[0005] The folded double-branch line includes a first transmission line, a second transmission line, a third transmission line and a fourth transmission line; the open / short circuit-loaded parallel branch includes a first open / short circuit-loaded transmission line, a second open / short circuit-loaded transmission line, a third open / short circuit-loaded transmission line and a fourth open / short circuit-loaded transmission line; the first open / short circuit-loaded transmission line includes a first bent transmission line, a first winding open line and a first short circuit line; the second open / short circuit-loaded transmission line includes a second bent transmission line, a second winding open line and a second short circuit line; the third open / short circuit-loaded transmission line includes a third bent transmission line, a third winding open line and a third short circuit line; the fourth open / short circuit-loaded transmission line includes a fourth bent transmission line, a fourth winding open line and a fourth short circuit line.

[0006] The left end of the first meandering transmission line is connected to the midpoint of the first transmission line; the lower end of the first meandering transmission line is connected to the upper end of the first winding open line and the left end of the first short line; the other end of the first winding open line is open; the other end of the first short line is short-circuited; the right end of the second meandering transmission line is connected to the midpoint of the second transmission line; the left end of the second meandering transmission line is connected to the right end of the second winding open line and the lower end of the second short line; the other end of the second winding open line is open; the other end of the second short line is short-circuited; the lower end of the third meandering transmission line is connected to the midpoint of the third transmission line; the upper end of the third meandering transmission line is connected to the lower end of the third winding open line and the left end of the third short line; the other end of the third winding open line is open; the other end of the third short line is short-circuited; the upper end of the fourth meandering transmission line is connected to the midpoint of the fourth transmission line; the right end of the fourth meandering transmission line is connected to the left end of the fourth winding open line and the upper end of the fourth short line; the other end of the fourth winding open line is open; the other end of the fourth short line is short-circuited;

[0007] The first transmission line has the same parameters as the third transmission line, and the second transmission line has the same parameters as the fourth transmission line; the first open / short circuit loaded transmission line has the same parameters as the third open / short circuit loaded transmission line, and the second open / short circuit loaded transmission line has the same parameters as the fourth open / short circuit loaded transmission line.

[0008] The characteristic impedance Z0 of the first transmission line, the second transmission line, the third transmission line and the fourth transmission line is determined by the coupling coefficient C of the coupler. For the constant resistance double-branch directional coupler, specifically: the impedance of the first transmission line and the third transmission line The impedance of the second and fourth transmission lines in, Z is the port impedance and C is the coupling coefficient.

[0009] The electrical lengths θ of the first transmission line, the second transmission line, the third transmission line and the fourth transmission line RIt can be determined by the dual-frequency ratio P, specifically: Where P = f2 / f1, f1 is the low frequency center frequency, and f2 is the high frequency center frequency.

[0010] The electrical lengths θ1 of the first meander transmission line, the second meander transmission line, the third meander transmission line and the fourth meander transmission line are determined by the dual-frequency ratio, specifically: in Z c1 are impedance values ​​of the first meander transmission line, the second meander transmission line, the third meander transmission line, and the fourth meander transmission line.

[0011] The electrical length θ2 of the first meandering open line, the second meandering open line, the third meandering open line and the fourth meandering open line is 90 degrees at the high frequency center frequency f2.

[0012] The electrical lengths θ3 of the first short-circuit line, the second short-circuit line, the third short-circuit line and the fourth short-circuit line are determined by the dual-frequency ratio P and the electrical lengths θ1 of the first meandering transmission line, the second meandering transmission line, the third meandering transmission line and the fourth meandering transmission line, specifically: The electrical lengths θ3 of the first short-circuit line, the second short-circuit line, the third short-circuit line, and the fourth short-circuit line are calculated, where Z c2 is the characteristic impedance of the first meandering open line, the second meandering open line, the third meandering open line and the fourth meandering open line, Z c3 is the characteristic impedance of the first short-circuit line, the second short-circuit line, the third short-circuit line and the fourth short-circuit line.

[0013] Due to the adoption of the above technical scheme, the present invention provides a small dual-frequency branch line coupler with equal phase difference. Due to the adoption of the specific structure, it can realize a directional coupler with dual-band, equal phase difference and small-volume co-directional output; in addition, the coupler has a simple structure, which can simplify the circuit layout and reduce the circuit size. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 It is a schematic diagram of the structure of the small dual-frequency branch line coupler with equal phase difference according to the present invention;

[0016] Figure 2 is the S parameter curve of the small dual-frequency branch line coupler with equal phase difference described in the present invention;

[0017] Figure 3 It is a phase difference curve between output ports of the small dual-frequency branch line coupler with equal phase difference described in the present invention.

[0018] In the figure: 1, folded double branch line, 11, first transmission line section, 12, second transmission line section, 13, third transmission line section, 14, fourth transmission line section, 21, first open / short circuit loaded transmission line, 22, second open / short circuit loaded transmission line, 23, third open / short circuit loaded transmission line, 24, fourth open / short circuit loaded transmission line, 211, first bent transmission line, 212, first winding open line, 213, first short line, 221, second bent transmission line, 222, second winding open line, 223, second short line, 231, third bent transmission line, 232, third winding open line, 233, third short line, 241, fourth bent transmission line, 242, fourth winding open line, 243, fourth short line. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0020] Figure 1 Schematic diagram of the structure of a small dual-frequency branch line coupler with equal phase difference of the present invention. The directional coupler of this example includes: a folded dual branch line 1, an open / short circuit loaded parallel branch 2 and four 50 ohm input / output ports.

[0021] Further, the left end of the first curved transmission line 211 is connected to the midpoint of the first section transmission line 11; the lower end of the first curved transmission line 211 is connected to the upper end of the first winding open line 212 and the left end of the first short line 213; the other end of the first winding open line 212 is open; the other end of the first short line 213 is short-circuited; the right end of the second curved transmission line 221 is connected to the midpoint of the second section transmission line 12; the left end of the second curved transmission line 221 is connected to the right end of the second winding open line 222 and the lower end of the second short line 223; the other end of the second winding open line 222 is open; the other end of the second short line 223 is short-circuited; the lower end of the third curved transmission line 231 is connected to the midpoint of the third section transmission line 13; the upper end of the third curved transmission line 231 is connected to the third winding open line 23 2 and the left end of the third short-circuit line 233; the other end of the third winding open line 232 is open; the other end of the third short-circuit line 233 is short-circuited; the upper end of the fourth bent transmission line 241 is connected to the midpoint of the fourth section transmission line 14; the right end of the fourth bent transmission line 241 is connected to the left end of the fourth winding open line 242 and the upper end of the fourth short-circuit line 243; the other end of the fourth winding open line 242 is open; the other end of the fourth short-circuit line 243 is short-circuited; the first section transmission line 11 has the same parameters as the third section transmission line 13, and the second section transmission line 12 has the same parameters as the fourth section transmission line 14; the first open / short-circuit loaded transmission line 21 has the same parameters as the third open / short-circuit loaded transmission line 23, and the second open / short-circuit loaded transmission line 22 has the same parameters as the fourth open / short-circuit loaded transmission line 24.

[0022] Specifically, in this embodiment, the circuit size can be reduced without affecting the dual-band working performance. The circuit parameters are calculated by using existing theoretical analysis, and then the circuit is miniaturized.

[0023] Depend on Figure 1 The two-port network composed of the first transmission line 11, the second transmission line 12, the third transmission line 13, the fourth transmission line 14 and the first open / short-circuit loaded transmission line 21, the second open / short-circuit loaded transmission line 22, the third open / short-circuit loaded transmission line 23, and the fourth open / short-circuit loaded transmission line 24 can obtain its ABCD matrix, and then according to the relationship between the A matrix and the scattering parameter, the phase response of the two-port network is obtained. Under the condition that both operating frequencies have a 90-degree phase response, the existing theoretical formula of the coupler in the present invention can be obtained, and the design steps are as follows:

[0024] Step 1: After determining the coupling coefficient C, the calculation formula of the traditional double-branch line coupler can be used to calculate the characteristic impedance Z0 of the first transmission line 11, the second transmission line 12, the third transmission line 13, and the fourth transmission line 14. For the constant resistance double-branch directional coupler, the impedance of the first transmission line 11 and the third transmission line 13 is The impedance of the second transmission line 12 and the fourth transmission line 14 in, Z is the port impedance, C is the coupling coefficient, and the coupling coefficient in this design is 3dB.

[0025] Step 2: After determining the frequency ratio P, according to the existing theoretical formula Calculate the electrical length θ of the first transmission line 11, the second transmission line 12, the third transmission line 13, and the fourth transmission line 14 R .

[0026] Step 3: Select appropriate impedance values ​​Z of the first meandering transmission line 211, the second meandering transmission line 221, the third meandering transmission line 231 and the fourth meandering transmission line 241 c1 , this design takes 80 ohms, and the electrical length θ2 of the first meandering open line 212, the second meandering open line 222, the third meandering open line 232 and the fourth meandering open line 242 is 90 degrees at high frequency. According to the existing theoretical formula The electrical lengths θ1 of the first meandering transmission line 211, the second meandering transmission line 221, the third meandering transmission line 231 and the fourth meandering transmission line 241 can be calculated, where Z0 is the impedance corresponding to the first transmission line 11 and the third transmission line 13 The impedance values ​​of the second transmission line 12 and the fourth transmission line 14 .

[0027] Step 4: Select appropriate impedance values ​​Z of the first meandering open line 212 , the second meandering open line 222 , the third meandering open line 232 , and the fourth meandering open line 242 c2 and the impedance values ​​Z of the first short-circuit line 213, the second short-circuit line 223, the third short-circuit line 233 and the fourth short-circuit line 243 c3 , this design uses 80 ohms, according to the existing formula The electrical lengths θ3 of the first short-circuit line 213, the second short-circuit line 223, the third short-circuit line 233 and the fourth short-circuit line 243 are calculated, where P=f2 / f1.

[0028] In a specific embodiment of the present invention, the operating frequency of the coupler is 1.207 GHz and 1.561 GHz, the frequency ratio P=1.29, and the input / output port impedance is 50Ω. c1 =Z c2＝ Zc3 =80Ω, θ2=90°, the impedance of the first transmission line 11 and the third transmission line 13 is calculated to be Z0=35.35Ω, the impedance of the second transmission line 12 and the fourth transmission line 14 is Z0=50Ω, θ R =70°, when Z0=50Ω, θ1=44.6°, θ3=18.9°, when Z0=35.35Ω, θ1=37.2°, θ3=25°. The small dual-frequency branch line coupler with equal phase difference of the present invention is designed according to the selected characteristic impedance and electrical length. Figure 2 and 3 As shown, the branch line coupler of this embodiment has a return loss (|S 11 |<-10dB) is greater than 10dB, the relative bandwidth is 14.1% (1.09GHz~1.26GHz) and 15.4% (1.42GHz~1.66GHz), and the isolation (|S 41 |<-10dB) is greater than 10dB, the relative bandwidth is 20.1% (1.09GHz~1.34GHz) and 13.5% (1.49GHz~1.70GHz), the relative bandwidth is 3±0.5dB, the relative bandwidth is 5.8% (1.17GHz~1.24GHz) and 3.8% (1.52GHz~1.58). The relative bandwidth of the phase difference between the output ports of 90°±10° is 14.9% (1.13GHz~1.31GHz) and 9.6% (1.54GHz~1.69GHz).

[0029] The technical indicators used in this embodiment are as follows:

[0030] Input / output port impedance: 50Ω;

[0031] Operating frequency: 1.207GHz and 1.561GHz

[0032] Return loss:>15dB;

[0033] Isolation:>15dB;

[0034] Amplitude imbalance between output ports: 1dB;

[0035] Phase difference error between output ports: ±10°.

[0036] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A small dual-frequency branch line coupler with equal phase difference, characterized in that: It includes a folded double branch line (1), an open / short line loaded parallel branch (2) and four 50 ohm ports; The folded double-branch line (1) comprises a first transmission line (11), a second transmission line (12), a third transmission line (13) and a fourth transmission line (14); the open / short circuit-loaded parallel branch (2) comprises a first open / short circuit-loaded transmission line (21), a second open / short circuit-loaded transmission line (22), a third open / short circuit-loaded transmission line (23) and a fourth open / short circuit-loaded transmission line (24); the first open / short circuit-loaded transmission line (21) comprises a first bent transmission line (211), a first meandering open line (21 2) and a first short-circuit line (213); the second open / short-circuit loaded transmission line (22) comprises a second bent transmission line (221), a second winding open line (222) and a second short-circuit line (223); the third open / short-circuit loaded transmission line (23) comprises a third bent transmission line (231), a third winding open line (232) and a third short-circuit line (233); the fourth open / short-circuit loaded transmission line (24) comprises a fourth bent transmission line (241), a fourth winding open line (242) and a fourth short-circuit line (243); The left end of the first meandering transmission line (211) is connected to the midpoint of the first section of the transmission line (11); the lower end of the first meandering transmission line (211) is connected to the upper end of the first winding open line (212) and the left end of the first short line (213); the other end of the first winding open line (212) is open; the other end of the first short line (213) is short-circuited; the right end of the second meandering transmission line (221) is connected to the midpoint of the second section of the transmission line (12); the left end of the second meandering transmission line (221) is connected to the right end of the second meandering open line (222) and the lower end of the second short line (223); the other end of the second meandering open line (222) is open; the other end of the second short line (223) is short-circuited; The lower end of the third curved transmission line (231) is connected to the midpoint of the third section transmission line (13); the upper end of the third curved transmission line (231) is connected to the lower end of the third winding open line (232) and the left end of the third short line (233); the other end of the third winding open line (232) is open; the other end of the third short line (233) is short-circuited; the upper end of the fourth curved transmission line (241) is connected to the midpoint of the fourth section transmission line (14); the right end of the fourth curved transmission line (241) is connected to the left end of the fourth winding open line (242) and the upper end of the fourth short line (243); the other end of the fourth winding open line (242) is open; the other end of the fourth short line (243) is short-circuited; The first transmission line (11) and the third transmission line (13) have the same parameters, and the second transmission line (12) and the fourth transmission line (14) have the same parameters; the first open / short circuit loaded transmission line (21) and the third open / short circuit loaded transmission line (23) have the same parameters, and the second open / short circuit loaded transmission line (22) and the fourth open / short circuit loaded transmission line (24) have the same parameters.

2. A small dual-frequency branch line coupler with equal phase difference according to claim 1, characterized in that: The characteristic impedance Z0 of the first transmission line (11), the second transmission line (12), the third transmission line (13) and the fourth transmission line (14) is determined by the coupling coefficient C of the coupler; for the constant resistance double-branch directional coupler, specifically: the impedance of the first transmission line (11) and the third transmission line (13) Impedance of the second transmission line (12) and the fourth transmission line (14) in, Z is the port impedance and C is the coupling coefficient.

3. A small dual-frequency branch line coupler with equal phase difference according to claim 1, characterized in that: The electrical lengths θ of the first transmission line (11), the second transmission line (12), the third transmission line (13) and the fourth transmission line (14) are R It is determined by the dual-frequency ratio P, specifically: Where P = f2 / f1, f1 is the low frequency center frequency, and f2 is the high frequency center frequency.

4. A small dual-frequency branch line coupler with equal phase difference according to claim 1, characterized in that: The electrical length θ1 of the first meandering transmission line (211), the second meandering transmission line (221), the third meandering transmission line (231) and the fourth meandering transmission line (241) is determined by the dual-frequency ratio, specifically: in Z c1 are impedance values ​​of the first meandering transmission line (211), the second meandering transmission line (221), the third meandering transmission line (231) and the fourth meandering transmission line (241).

5. A small dual-frequency branch line coupler with equal phase difference according to claim 1, characterized in that The electrical length θ2 of the first meandering open line (212), the second meandering open line (222), the third meandering open line (232) and the fourth meandering open line (242) is 90 degrees at the high frequency center frequency f2.

6. A small dual-frequency branch line coupler with equal phase difference according to claim 1, characterized in that The electrical length θ3 of the first short-circuit line (213), the second short-circuit line (223), the third short-circuit line (233) and the fourth short-circuit line (243) is determined by the dual-frequency ratio P and the electrical length θ1 of the first meandering transmission line (211), the second meandering transmission line (221), the third meandering transmission line (231) and the fourth meandering transmission line (241), specifically: The electrical lengths θ3 of the first short-circuit line (213), the second short-circuit line (223), the third short-circuit line (233) and the fourth short-circuit line (243) are calculated, where Z c2 is the characteristic impedance of the first meandering open line (212), the second meandering open line (222), the third meandering open line (232) and the fourth meandering open line (242), Z c3 is the characteristic impedance of the first short-circuit line (213), the second short-circuit line (223), the third short-circuit line (233) and the fourth short-circuit line (243).

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