CN113224494B - Dual-band power unequal directional coupler based on microstrip-slot line coupling line - Google Patents
Dual-band power unequal directional coupler based on microstrip-slot line coupling line Download PDFInfo
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- CN113224494B CN113224494B CN202110504805.XA CN202110504805A CN113224494B CN 113224494 B CN113224494 B CN 113224494B CN 202110504805 A CN202110504805 A CN 202110504805A CN 113224494 B CN113224494 B CN 113224494B
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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
- H01P5/18—Conjugate devices, i.e. devices having at least one port decoupled from one other port consisting of two coupled guides, e.g. directional couplers
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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
- H01P5/18—Conjugate devices, i.e. devices having at least one port decoupled from one other port consisting of two coupled guides, e.g. directional couplers
- H01P5/184—Conjugate devices, i.e. devices having at least one port decoupled from one other port consisting of two coupled guides, e.g. directional couplers the guides being strip lines or microstrips
Abstract
The invention discloses a dual-band unequal power directional coupler based on a microstrip-slot line coupling line, which is of an axisymmetric structure and comprises a first microstrip-slot line coupling line, a second microstrip-slot line coupling line, a microstrip gradual change line, a third microstrip line, a metal ground, a first port, a second port, a third port, a fourth port and a dielectric substrate; the microstrip-slot line coupling line is composed of a microstrip line positioned on the top layer of the dielectric substrate and a slot line positioned on the bottom layer of the dielectric substrate. The invention not only overcomes the problem of inconsistent odd and even mode phase velocities of the parallel coupling lines, but also has the advantages of small size, convenient design and processing and the like.
Description
Technical Field
The invention belongs to the technical field of microwaves, relates to a dual-band power unequal directional coupler, and particularly relates to a dual-band power unequal directional coupler based on a microstrip-slot line coupling line.
Background
The directional coupler is one of the most basic passive devices in a wireless communication system, and has wide application in microwave circuits such as phase shifters, power dividers or combiners, Butler matrices and the like. The traditional plane directional coupler mainly comprises a branch line coupler and a parallel microstrip line coupling line, wherein the branch line coupler occupies a large area, and the parallel microstrip line coupling line coupler is difficult to realize high coupling degree. With the development of wireless communications and other wireless services, wireless systems are now moving toward dual-band and even multi-band. Therefore, research and development of dual or multi-band microwave devices are imperative.
At present, most of the dual-band directional couplers are formed by improving on the basis of the traditional branch line coupler. For example, short-circuit lines or open-circuit lines are connected in parallel at four corners of a conventional branch line coupler; the midpoint of each branch line of the traditional branch line coupler is connected with a short-circuit line or an open line in parallel; adding a center tap on two branch lines of the traditional branch line coupler; in-line port connection of conventional branch line couplerQuarter wave impedance transformers, etc. However, the dual-band directional coupler formed by improving the conventional branch line coupler has a problem of being oversized. The other dual-band directional coupler is formed on the basis of parallel microstrip coupling lines, the size is remarkably reduced, however, the distance between the parallel microstrip coupling lines is limited by a PCB processing technology, so that the tuning range of odd-mode impedance and even-mode impedance of the dual-band directional coupler is limited, and the isolation degree of the directional coupler is seriously influenced due to different odd-mode and even-mode phase speeds of the parallel microstrip coupling lines. In addition, the direct connection end and the coupling end of most of the current dual-band directional couplers are equal power output, namely | S |31/S 211. In many applications, it is desirable for a directional coupler to have unequal power output characteristics.
The invention provides a novel dual-band unequal power directional coupler based on a microstrip-slot line coupling line, which not only solves the problem of inconsistent odd and even mode phase velocities of parallel coupling lines, but also has the advantages of small size, convenience in design and processing and the like.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a dual-band unequal power directional coupler based on a microstrip-slot line coupling line, which not only solves the problem of inconsistent odd and even mode phase speeds of parallel coupling lines, but also has the advantages of small size, convenience in design and processing and the like.
The invention adopts the following technical scheme:
a dual-band power unequal directional coupler based on a microstrip-slot line coupling line is an axisymmetric structure and comprises:
a dielectric substrate;
the metal ground is positioned at the bottom layer of the dielectric substrate;
two pairs of orthogonal microstrip-slot line coupled lines;
four orthogonal microstrip gradient lines positioned on the top layer of the dielectric substrate;
four ports;
wherein:
the two pairs of orthogonal microstrip-slot line coupled lines comprise a first microstrip-slot line coupled line and a second microstrip-slot line coupled line, the first microstrip-slot line coupled line comprises a first microstrip line positioned on the top layer of the dielectric substrate and a first slot line positioned on the metal ground, and the first slot line is positioned right below the first microstrip line, namely the central line of the first microstrip line is superposed with the central line of the first slot line; the second microstrip-slot line coupling line comprises a second microstrip line positioned on the top layer of the dielectric substrate and a second slot line positioned on the metal ground (namely, the first slot line and the second slot line are both provided with a slot on the metal ground), and the first slot line is positioned under the first microstrip line, namely, the central line of the second microstrip line is superposed with the central line of the second slot line;
the included angle between each microstrip gradual change line of the four orthogonal microstrip gradual change lines and the first microstrip line and the second microstrip line is 45 degrees; the narrower end of each microstrip gradually-changing line is connected with the intersection of the orthogonal microstrip-slot line coupling lines, the wider end of each microstrip gradually-changing line is connected with one end of the third microstrip line, and the other end of the third microstrip line is used as one port.
Preferably, the microstrip gradual change line is a 65 ohm to 50 ohm microstrip gradual change line, and the third microstrip line is a 50 ohm microstrip line.
The initial electrical lengths of the first microstrip line and the first slot line are the same, the center frequency corresponding to the low frequency band is 124 degrees, the initial width of the first microstrip line corresponds to 32 ohm even mode impedance, and the initial width of the first slot line corresponds to 71 ohm odd mode impedance.
The initial electrical lengths of the second microstrip line and the second slot line are the same, the central frequency of the corresponding low frequency band is 116 degrees, the initial width of the second microstrip line corresponds to 42 ohm even mode impedance, and the initial width of the second slot line corresponds to 73 ohm odd mode impedance.
Through design optimization, the width of the second microstrip line is narrower than that of the first microstrip line, and the length of the second microstrip line is shorter than that of the first microstrip line. The second slot line has a width smaller than the first slot line and a length shorter than the first slot line. The first slot line and the second slot line are both longer and narrower than the corresponding microstrip line.
The odd-even mode impedance of the microstrip-slot line coupling line can be effectively adjusted by adjusting the widths of the microstrip and the slot line in the microstrip-slot line coupling line. The length of the first slot line and the length of the second slot line are prolonged, so that the problem of inconsistent electrical lengths of odd and even modes caused by inconsistent phase speeds of the microstrip-slot line coupling line can be effectively compensated, and the isolation of the coupler is improved.
The working principle is as follows:
the micro-strip-slot line coupling line has orthogonality of electric field distribution when odd and even modes work, is relatively independent, and is convenient for adjusting odd and even mode impedance respectively. Make the odd and even mode impedances of the first microstrip-slot line coupled line be zo1And ze1Corresponding admittances are yo1And ye1Electrical length of 2 theta1(ii) a The odd and even mode impedances of the second microstrip-slot line coupled line are zo2And ze2Corresponding admittances are yo2And ye2Electrical length of 2 theta2. The directional coupler provided by the invention is subjected to odd-even mode analysis to obtain a formula (1). If at theta1And an output power ratio K (K ═ S)31/S21I) and the frequency ratio p are degrees of freedom, and theta can be solved by the formula (1)2：
Wherein when tan (p θ)1)＞0，tan(pθ2) And when the value is more than 0, i is equal to 1, j is equal to 2, and conversely, i is equal to 2, and j is equal to 1.
And the selection of the degree of freedom should satisfy: tan (theta)1)≠|tan(pθ1)|，tan(θ2)≠|tan(pθ2)|，tan(pθ1)tan(pθ2)＞0。
When the parity-mode admittance satisfies the following relation:
yo1＝ye1R1 (4)
yo2＝ye2R2 (5)
wherein R is1＝tanθ1|tan(pθ1)|，R2＝tanθ2|tan(pθ2)|，y0Indicating the characteristic admittance of the port.
Can obtain | S11|＝0、|S41|＝0，|S31/S21K and S21)-Φ(S31) I.e., m · 90 ° (m ═ 1, 3), the required condition of the coupler is satisfied.
Particularly, in the design and optimization process, the frequency ratio and the power ratio can be adjusted by adjusting the odd-even mode impedance, namely the microstrip line width and the slot line width of the microstrip-slot line coupled line.
The invention has the following advantages:
(1) for the microstrip-slot line coupled line, the problem of inconsistent electrical lengths of odd and even modes caused by inconsistent phase velocities of the odd and even modes of the traditional parallel coupled line can be effectively solved by changing the length of the slot line and keeping the length of the microstrip line unchanged, so that the isolation of the directional coupler is improved;
(2) because the odd and even mode impedances of the microstrip-slot line coupling line are relatively independent, the odd and even mode impedances can be tuned respectively, so that the design and the processing of the dual-band directional coupler are more convenient;
(3) compared with a dual-band branch line directional coupler, the dual-band directional coupler constructed by the microstrip-slot line coupling line has smaller size, and is beneficial to miniaturization of a system.
Drawings
Fig. 1-1 is an overall structural schematic diagram of a dual-band power unequal directional coupler based on a microstrip-slot line coupled line;
fig. 1-2 is a top metal structure diagram of a dual-band power unequal directional coupler based on microstrip-slot line coupled lines;
FIGS. 1-3 are bottom metal structure diagrams of dual-band unequal power directional couplers based on microstrip-slot line coupled lines;
FIGS. 1-4 are cross-sectional side views AA' of dual-band power unequal directional couplers based on microstrip-slot line coupled lines;
FIG. 2 is the simulation result of S parameter of the dual-band unequal power directional coupler based on the microstrip-slot line coupled line;
fig. 3 is a simulation result of the amplitude and phase balance characteristics of the dual-band power unequal directional coupler based on the microstrip-slot line coupled line.
Detailed Description
The present invention will be further described with reference to the accompanying drawings.
As shown in fig. 1-1, 1-2, 1-3, and 1-4, a dual-band unequal power directional coupler based on a microstrip-slot line coupling line has an axisymmetric structure, and includes a first microstrip-slot line coupling line 1, a second microstrip-slot line coupling line 2, a 65-50 ohm microstrip gradual change line 3, a 50-ohm third microstrip line 4, a metal ground 5, a first port 6, a second port 7, a third port 8, a fourth port 9, and a dielectric substrate 10;
the bottom layer of the medium substrate 10 is provided with a metal ground 5;
the first microstrip-slot line coupled line 1 comprises a first microstrip line 1a positioned on the top layer of the dielectric substrate 10 and a first slot line 1b positioned on the metal ground 5;
the second microstrip-slot line coupled line 2 comprises a second microstrip line 2a positioned on the top layer of the dielectric substrate 10 and a second slot line 2b positioned on the metal ground 5; namely, the first slot line 1b and the second slot line 2b are both grooved on the metal floor 5.
Four orthogonal 65-50 ohm microstrip gradient lines 3 which form an included angle of 45 degrees with the first microstrip line 1a and the second microstrip line 2a are arranged at the joint of the first microstrip line 1a and the second microstrip line 2 a.
The narrower end of each microstrip gradual change line 3 is connected with the intersection of the orthogonal microstrip-slot line coupling lines, the wider end is connected with one end of a 50-ohm third microstrip line 4, and the other end of the 50-ohm third microstrip line 4 is used as one port.
The center lines of the first microstrip line 1a and the second microstrip line 2a are superposed with the center lines of the first slot line 1b and the second slot line 2 b.
The initial electrical lengths of the first microstrip line 1a and the first slot line 1b are the same, the center frequency of the corresponding low frequency band is 124 degrees, and the initial width of the first microstrip line 1a corresponds to 32-ohm even-mode impedance. The initial width of the first slot line 1b corresponds to an odd mode impedance of 71 ohms. The initial electrical lengths of the second microstrip line 2a and the second slot line 2b are the same, the center frequency of the corresponding low frequency band is 116 degrees, and the initial width of the second microstrip line 2a corresponds to 42 ohm even mode impedance. The initial width of the second slot line 2b corresponds to an odd mode impedance of 73 ohms. Through design optimization, the width of the second microstrip line 2a is narrower than that of the first microstrip line 1a, and the length of the second microstrip line is shorter than that of the first microstrip line 1 a. The second slot line 2b is wider than the first slot line 1b and shorter than the first slot line 1 b. The first slot line 1b and the second slot line 2b are both longer and narrower than the corresponding microstrip line.
Fig. 2 is a simulation result of S-parameter of a dual-band power unequal directional coupler based on a microstrip-slot line coupled line when the frequency ratio is 2 and the power ratio is 1.414. The center frequencies of the two working frequency bands of the coupler are 2.4GHz and 4.8GHz respectively. I S21I and I S31The amplitude of |, in the 2.4GHz frequency band is-5.46 dB and-2.37 dB respectively, the power difference is 3.09dB, in the 4.8GHz frequency band is-6.84 dB and-3.77 dB respectively, and the power difference is 3.07 dB. Return loss (| S)11|) better than-40 dB at the 2.4GHz band and better than-14 dB at the 4.8GHz band. Isolation (| S)41|) is better than-22 dB in both frequency bands. In this example, the dielectric substrate is a microwave board with a dielectric constant of 10.2 and a thickness of 1.27 mm.
Fig. 3 is a simulation result of amplitude and phase balance characteristics of a dual-band power unequal directional coupler based on a microstrip-slot line coupled line. It can be seen from the figure that the absolute value of the amplitude difference of the output signals at the through end and the coupling end is 3 +/-0.5 dB, and the phase difference is 89.60 degrees and 270.26 degrees respectively at the two frequency bands, so that the invention has good amplitude and phase balance characteristics no matter in the low frequency band or the high frequency band.
In conclusion, the invention can realize unequal power output in two frequency bands, and has compact structure and simple design. Meanwhile, the method has better levels on the key performances such as return loss, isolation, amplitude and phase balance and the like.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.
Claims (4)
1. Double-frequency-band power unequal directional coupler based on microstrip-slot line coupling line is an axisymmetric structure, and is characterized by comprising:
a dielectric substrate;
the metal ground is positioned at the bottom layer of the dielectric substrate;
two pairs of orthogonal microstrip-slot line coupled lines;
four orthogonal microstrip gradient lines positioned on the top layer of the dielectric substrate;
four ports;
wherein the content of the first and second substances,
the two pairs of orthogonal microstrip-slot line coupled lines comprise a first microstrip-slot line coupled line and a second microstrip-slot line coupled line; the first microstrip-slot line coupling line comprises a first microstrip line positioned on the top layer of the dielectric substrate and a first slot line positioned on the metal ground, and the central line of the first microstrip line is superposed with the central line of the first slot line; the second microstrip-slot line coupling line comprises a second microstrip line positioned on the top layer of the dielectric substrate and a second slot line positioned on the metal ground, and the central line of the second microstrip line is superposed with the central line of the second slot line;
the included angle between each microstrip gradual change line of the four orthogonal microstrip gradual change lines and the first microstrip line and the second microstrip line is 45 degrees; the narrower end of each microstrip gradually-changing line is connected with the intersection point of the orthogonal microstrip-slot line coupling lines, the wider end of each microstrip gradually-changing line is connected with one end of a third microstrip line, and the other end of the third microstrip line is used as one of the four ports;
the frequency ratio and the output power ratio are adjusted by adjusting odd-even mode impedance, namely the widths of a first microstrip line and a first slot line in the first microstrip-slot line coupled line and the widths of a second microstrip line and a second slot line in the second microstrip-slot line coupled line.
2. The dual-band power unequal directional coupler based on the microstrip-slot line coupled line according to claim 1, wherein the microstrip gradual change line is a 65 ohm to 50 ohm microstrip gradual change line, and the third microstrip line is a 50 ohm microstrip line.
3. The dual-band power unequal directional coupler based on the microstrip-slot line coupled line according to claim 1, wherein the widths of the first microstrip line and the first slot line in the first microstrip-slot line coupled line and the widths of the second microstrip line and the second slot line in the second microstrip-slot line coupled line are adjusted for adjusting the odd-even mode impedance of the corresponding microstrip-slot line coupled line.
4. The dual-band power unequal directional coupler based on the microstrip-slot line coupled line according to claim 1, wherein the length of the first slot line and the second slot line is adjusted to regulate and compensate the problem of the inconsistent electrical lengths of the odd and even modes caused by the inconsistent odd and even mode phase velocities of the microstrip-slot line coupled line, so that the isolation of the coupler is improved.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3715692A (en) * | 1972-01-10 | 1973-02-06 | Us Army | Microstrip-slot line phase shifter |
| CN112768864A (en) * | 2020-12-28 | 2021-05-07 | 杭州电子科技大学 | Microstrip-slot line coupled dual-band 90-degree directional coupler |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2008152852A1 (en) * | 2007-06-14 | 2008-12-18 | Kyocera Corporation | Current blocking circuit, hybrid circuit device, transmitter, receiver, transmitter-receiver, and radar device |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3715692A (en) * | 1972-01-10 | 1973-02-06 | Us Army | Microstrip-slot line phase shifter |
| CN112768864A (en) * | 2020-12-28 | 2021-05-07 | 杭州电子科技大学 | Microstrip-slot line coupled dual-band 90-degree directional coupler |
Non-Patent Citations (1)
| Title |
|---|
| 《Microstrip-Slot Coupler Design-Part I: S-Parameters of Uncompensated and Compensated Couplers》;R. K. Hoffmann and J. Siegl;《 IEEE Transactions on Microwave Theory and Techniques》;19820831;第30卷(第8期);全文 * |
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