CN203813004U - Leakage feeder - Google Patents
Leakage feeder Download PDFInfo
- Publication number
- CN203813004U CN203813004U CN201420151294.3U CN201420151294U CN203813004U CN 203813004 U CN203813004 U CN 203813004U CN 201420151294 U CN201420151294 U CN 201420151294U CN 203813004 U CN203813004 U CN 203813004U
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- balun
- twisted pair
- radio frequency
- feeder
- coaxial connector
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- 238000004804 winding Methods 0.000 claims abstract description 5
- 239000004020 conductor Substances 0.000 claims description 8
- 230000009466 transformation Effects 0.000 claims description 5
- 230000005540 biological transmission Effects 0.000 abstract description 10
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 238000005452 bending Methods 0.000 abstract description 2
- 238000006243 chemical reaction Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 230000008054 signal transmission Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 1
- 238000002592 echocardiography Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
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Abstract
The utility model provides a leakage feeder. The leakage feeder comprises a twisted pair, a termination resistor, a balun and a radio frequency coaxial connector; the twisted pair is formed by winding two wires which are mutually insulated; at one end of the twisted pair, the two wires of the twisted pair are connected with each other through the termination resistor, at the other end of the twisted pair, the two wires of the twisted pair are connected with the balanced terminal of the balun; and the unbalanced terminal of the balun is connected with the radio frequency coaxial connector. The leakage feeder is relatively soft and thin, and is small in bending radius, and therefore the leaky feeder is simple to install, and can be reused. The leakage feeder is low in cost and simple to manufacture, radio coverage which is along linear paths and is similar to a leakage coaxial cable is achieved at the same time, and therefore the leakage feeder is suitable for being applied to occasions where the transmission distance is relatively short and requirements on signal attenuation are low.
Description
Technical Field
The utility model relates to a wireless communication field especially relates to a leakage transmission cable.
Background
Compared to conventional antennas, leaky coaxial cables are more suitable for applications requiring radio coverage along well-defined paths, such as subway, railway and highway intra-tunnel communications with limited radio propagation, WLAN communications in underground buildings, etc. Leaky coaxial cables may also be referred to as leaky cables or leaky cables for short. The structure of the leaky cable is basically consistent with that of a common coaxial cable and consists of an inner conductor, an insulating medium and an outer conductor provided with periodic slotted holes. Electromagnetic waves are longitudinally transmitted in the leaky cable and are radiated to the outside through the slotted holes; the external electromagnetic field can be induced into the leaky cable through the slotted hole and transmitted to the receiving end. Leaky cables are often used in wireless local area network systems or other wireless communication systems to transmit Radio Frequency (RF) signals. Compared with the traditional antenna, the leaky coaxial cable has the advantages that the signal coverage is uniform, and the transmission parameters such as characteristic impedance, standing wave coefficient and attenuation are more uniform and stable.
However, although leaky coaxial cables have good radio frequency characteristics and are durable, they are expensive. In some cases, for example, when the required propagation path is not long, the very low attenuation provided by leaky coaxial cables is not necessary in practice. Furthermore, leaky coaxial cables are relatively large in diameter (about 20 mm) and very stiff, requiring a relatively large bend radius.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a leakage feeder.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
according to an aspect of the present invention, there is provided a leakage feeder, including: the system comprises a twisted pair, a terminating resistor, a balun and a radio frequency coaxial connector; the twisted pair is formed by winding two mutually insulated wires; at one end of the twisted pair, two wires of the twisted pair are connected through the termination resistor, and at the other end of the twisted pair, two wires of the twisted pair are connected with a balance end of the balun; and the unbalanced end of the balun is connected with the radio frequency coaxial connector.
The leaky feeder may be directly connected to a radio frequency interface of the wireless device, receive radio frequency signals from the wireless device, and leak radio frequency signals to a nearby environment through the twisted pair, thereby achieving radio coverage along a linear path. The leaky feeder is cheap and convenient to use for applications where the transmission path is relatively short and does not require very low attenuation. In addition, such leaky feeder is relatively flexible and can be repeatedly installed and utilized.
According to a further embodiment of the present invention, the leaky feeder may further comprise another twisted pair in parallel with the twisted pair, wherein at one end of the two twisted pairs in parallel, the two conductors of each twisted pair are connected through the termination resistor, and at the other end of the two twisted pairs in parallel, the two conductors of each twisted pair are connected to the balanced terminal of the balun. The radio frequency signal leaked by such a leaking feeder line has a greater strength. In such a leaky feeder, matching of impedance characteristics is simpler, and a balun having a simpler structure and being cheaper can be used, thereby further reducing the cost.
Drawings
The drawings are only intended to illustrate and explain the present invention and do not limit the scope of the invention. Wherein,
fig. 1 is a schematic structural view of a leaky feeder according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an exemplary circuit configuration of a lumped element balun;
fig. 3 is a schematic structural diagram of an example of a microstrip line balun;
fig. 4 is a schematic view of an application scenario of a leaky feeder according to an embodiment of the present invention;
fig. 5 is a schematic view of an application scenario of a leaky feeder according to yet another embodiment of the present invention;
fig. 6 is a schematic structural view of a leaky feeder according to yet another embodiment of the present invention;
fig. 7 is a schematic diagram of an example of a transmission line balun.
Detailed Description
In order to clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will be described with reference to the accompanying drawings.
Although leaky coaxial cable is commonly used to transmit radio frequency signals in wireless lan systems or other wireless communication systems, twisted pair cables can also propagate radio frequency signals at certain frequencies (preferably up to 2.4 GHz). The unshielded twisted pair can leak a part of radio frequency signals to the external environment, and in an application occasion with low requirements on signal attenuation in a proper transmission distance, the characteristic can be utilized to use the twisted pair as a substitute of a leaky coaxial cable and realize radio frequency coverage along a linear path similar to the leaky coaxial cable.
Fig. 1 shows a schematic structural diagram of a leaky feeder according to an embodiment of the present invention. The leaky feeder 10 includes a twisted pair 101 formed by winding two mutually insulated wires, a terminating resistor 103, a balun 105, and a radio frequency coaxial connector 107. At one end of the twisted pair 101, the two conductors of the twisted pair are connected by a terminating resistor 103. The terminating resistor 103 is used here primarily to avoid reflections and echoes of the signal, and its resistance depends on the impedance characteristics of the connected cable, irrespective of the length of the cable. For a twisted pair, the termination resistance is typically between 100 ohms and 140 ohms, with a typical value being 120 ohms. At the other end of the twisted pair 101, two wires of the twisted pair are respectively connected to a balanced terminal of a balun 105, and an unbalanced terminal of the balun 105 is connected to a radio frequency coaxial connector 107. The common rf coaxial connector may be an SMA type rf coaxial connector, an N type rf coaxial connector, a BNC type rf coaxial connector, or a TNC type rf coaxial connector. The types of baluns commonly used may be microstrip line baluns, lumped element baluns, etc.
The leaky feeder has low cost and simple manufacture, and simultaneously realizes radio coverage along a linear path similar to a leaky coaxial cable, thereby completely meeting the signal transmission requirement of an application occasion with relatively short transmission distance or less strict signal attenuation requirement. In addition, such leaky feeder is very flexible and can be repeatedly installed and utilized.
With continued reference to fig. 1, in leaky feeder 10, balun 105 is used for unbalanced to balanced conversion and impedance matching. This is because twisted pair transmission is balanced, while RF signal transmission from a wireless device is unbalanced, and the impedance of the twisted pair formed by two wires wound is typically 100 ohms, while the impedance of the radio frequency port of the wireless device or the coaxial cable transmitting the RF signal is typically 50 ohms, with impedance mismatch between the two. Therefore, balun is required for the unbalanced to balanced conversion and impedance matching. Here, a balun device having impedance matching characteristics, such as a 1: 2 type balun, may be used.
As mentioned above, the types of balun may employ, for example, a microstrip line balun, a lumped element balun, or the like. Fig. 2 shows a schematic diagram of an example of a lumped-element balun. As shown in fig. 2, one side of the balun is a single-ended port 201 (which may also be referred to as an unbalanced terminal), and the other side of the balun is two differential ports 202 and 203 (which may be collectively referred to as balanced terminals), the balun generates a phase shift of ± 90 ° through two capacitors C and two inductors L, thereby realizing conversion between unbalanced and balanced, and impedance matching between two terminals of the balun is realized through a parallel resistor R of an appropriate size. The lumped element balun can simultaneously realize the conversion of unbalance and balance and impedance matching on the chip level, and has stable performance and high reliability. Fig. 3 shows a schematic structural diagram of an example of a microstrip line balun, where a port 301 is an unbalanced terminal and ports 302 and 303 are balanced terminals. The microstrip line type balun realizes the conversion between unbalance and balance and impedance matching based on a printed circuit board or a metal substrate, has a simpler and more flexible structure, is convenient to realize, and has the advantage of low price.
It should be noted that the above is illustrative only and not limiting, and is not limited to balun type 1: 2. Different types of coaxial cables may have different impedances, and the impedance of the cable may change at different frequencies, and those skilled in the art may select a balun having a corresponding impedance transformation ratio according to different actual application environments and requirements, or different characteristic impedances of connected cables, antennas, and other devices.
Fig. 4 shows an application scenario of the leaky feeder according to an embodiment of the present invention. The rf coaxial connector of the leaky feeder 40 may be directly connected to the rf interface of the wireless device 41. In this way, the leaky feeder 40 may receive radio frequency signals from the wireless device 41, and when the radio frequency signals are transmitted over the twisted pair in the leaky feeder 40, the twisted pair may leak part of the radio frequency signals into the environment near the leaky feeder, thereby achieving radio coverage along a linear path as with leaky coaxial cables. Compared with a leaky coaxial cable, the leaky feeder is softer and thinner, has a smaller bending radius, is convenient to install and can be reused. Although having higher attenuation losses than leaky coaxial cable, the leaky feeder is very inexpensive and simple to manufacture compared to leaky coaxial cable, while also achieving radio coverage along a linear path similar to leaky coaxial cable and therefore can be used as a substitute for leaky coaxial cable within a suitable transmission distance or in applications where signal attenuation is not as demanding.
Fig. 5 shows an application scenario of the leaky feeder according to another embodiment of the present invention. The rf coaxial connector of leaky feeder 50 may also be connected to the rf interface of wireless device 51 by a length of coaxial cable 52. For example, when a wireless device (e.g., a wireless local area network access device AP) needs to be installed in a location that is remote from the desired coverage area due to system requirements or requirements of the actual installation environment, the leaky feeder 50 may be connected to the radio frequency interface of the wireless device 51 through a standard (non-leaky) coaxial cable 52. Thus, the wireless device 51 can transmit the radio frequency signal to the leaky feeder 50 installed at a remote place from the wireless device 51 through the coaxial cable 52, so that the application range of the leaky feeder can be expanded.
Fig. 6 is a schematic structural diagram of a leaky feeder according to yet another embodiment of the present invention. The leaky feeder 60 differs from the leaky feeder described above in connection with fig. 1 mainly in that it comprises two twisted pairs in parallel: twisted pair 601 and twisted pair 602. Each of the two parallel twisted pairs is formed by winding two wires insulated from each other. At one end of the two parallel twisted pairs, the two conductors in each twisted pair are connected by a terminating resistor 603. As discussed above in connection with fig. 1, the value of the terminating resistor depends on the impedance characteristics of the connected cable, independent of the length of the cable. In this embodiment, the impedance of the two twisted pairs in parallel is about 50 ohms, and thus, the termination resistance 603 may be between 40 ohms and 70 ohms, for example, 50 ohms. At the other end of the two parallel twisted pairs, two wires of each twisted pair are respectively connected to the balanced end of the balun 605, and the unbalanced end of the balun 605 is connected to the rf coaxial connector 607. As discussed above in connection with fig. 1, those skilled in the art can select baluns with corresponding impedance transformation ratios according to different application environments and requirements, or different characteristic impedances of connected cables, antennas, and the like. In this embodiment, since the impedance (50 ohms) of the two twisted pairs in parallel is exactly matched to the impedance of the radio frequency interface, a balun with an impedance conversion ratio of 1: 1 may be used, or a balun without impedance conversion characteristics may be used. The radio frequency signal leaked by the leakage feeder line has larger strength. In addition, in the leakage feeder line, the impedance characteristic can be directly matched with the impedance characteristic of a radio frequency interface of the wireless equipment, so that a balun with a simpler structure and lower cost can be adopted, and the cost is further reduced.
Fig. 7 shows an exemplary structure diagram of a transmission line balun, which is actually a coaxial balun implemented by using a quarter-wave coaxial line, and provides an impedance transformation ratio of 1: 1, where port 701 is an unbalanced terminal and ports 702 and 703 are balanced terminals. For another example, in the lumped balun structure discussed in connection with fig. 2, the parallel resistors R are removed, and a balun providing only balanced and unbalanced conversion is obtained. The balun described above is for illustrative purposes only and is not limiting, and those skilled in the art can select the corresponding balun device according to actual requirements.
It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.
The above description is only exemplary of the present invention, and is not intended to limit the scope of the present invention. Any equivalent changes, modifications and combinations that may be made by those skilled in the art without departing from the spirit and principles of the invention should be considered within the scope of the invention.
Claims (6)
1. A leaky feeder, comprising: the system comprises a twisted pair, a terminating resistor, a balun and a radio frequency coaxial connector; the twisted pair is formed by winding two mutually insulated wires; at one end of the twisted pair, two wires of the twisted pair are connected through the termination resistor, and at the other end of the twisted pair, two wires of the twisted pair are connected with a balance end of the balun; and the unbalanced end of the balun is connected with the radio frequency coaxial connector.
2. Leaky feeder as claimed in claim 1, characterized in that said balun is of the type microstrip line balun or lumped element balun.
3. The leakage feed line of claim 1 or 2, wherein the balun is a balun having an impedance transformation ratio of 1: balun of type 2.
4. The leaky feeder as claimed in claim 1, further comprising another twisted pair in parallel with said twisted pairs, wherein at one end of the two twisted pairs in parallel, the two conductors of each twisted pair are connected through said termination resistor, and at the other end of the two twisted pairs in parallel, the two conductors of each twisted pair are connected to the balanced terminal of said balun.
5. The leakage feed line of claim 4, wherein the balun is a balun having an impedance transformation ratio of 1: balun of type 1.
6. The leakage feed line of claim 1, wherein the radio frequency coaxial connector is of any one of the following types: SMA type radio frequency coaxial connector, N type radio frequency coaxial connector, BNC type radio frequency coaxial connector, TNC type radio frequency coaxial connector.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420151294.3U CN203813004U (en) | 2014-03-31 | 2014-03-31 | Leakage feeder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420151294.3U CN203813004U (en) | 2014-03-31 | 2014-03-31 | Leakage feeder |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN203813004U true CN203813004U (en) | 2014-09-03 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201420151294.3U Expired - Fee Related CN203813004U (en) | 2014-03-31 | 2014-03-31 | Leakage feeder |
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| CN (1) | CN203813004U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115149234A (en) * | 2022-09-02 | 2022-10-04 | 浙江铖昌科技股份有限公司 | Transmission line structure and transmission line design method |
-
2014
- 2014-03-31 CN CN201420151294.3U patent/CN203813004U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115149234A (en) * | 2022-09-02 | 2022-10-04 | 浙江铖昌科技股份有限公司 | Transmission line structure and transmission line design method |
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| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20140903 |
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| CF01 | Termination of patent right due to non-payment of annual fee |