CN214957297U - A broadband high-power directional coupler covering the VLF-VHF frequency band - Google Patents
A broadband high-power directional coupler covering the VLF-VHF frequency band Download PDFInfo
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- CN214957297U CN214957297U CN202121079157.XU CN202121079157U CN214957297U CN 214957297 U CN214957297 U CN 214957297U CN 202121079157 U CN202121079157 U CN 202121079157U CN 214957297 U CN214957297 U CN 214957297U
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- coaxial transmission
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Abstract
The utility model discloses a cover high-power directional coupler of broadband of VLF-VHF frequency channel mainly solves current directional coupler loss increase, the limited problem of power capacity when the low frequency covers. The directional coupler comprises a first coaxial transmission line with a ferrite core, two sampling comparison circuits which are connected to two ends of the first coaxial transmission line and have circuit structures which are symmetrical relative to the middle of the first coaxial transmission line, and a main power channel and a coupling power output channel which are connected with the sampling comparison circuits. Through the design, the utility model discloses a coaxial transmission line and the hybrid circuit that collection total parameter resistance electric capacity constitutes utilize coaxial transmission line's interior outer conductor electric current opposite characteristic, carry out the topological design of the sample comparison circuit that corresponds, the parasitic parameter of compensation and reduction resistance for this directional coupling circuit can conveniently insert in radio frequency microwave communication, the test system, plays the effect of monitoring and protection.
Description
Technical Field
The utility model relates to a directional coupler, specifically speaking relates to a cover high-power directional coupler of broadband of VLF-VHF frequency channel.
Background
The broadband high-power directional coupler is an important component of radio frequency microwave communication, testing and other systems, is mainly used for measuring the forward power and the reverse power passing through the system, and is usually connected behind a high-power transmitter and in front of a radiation antenna and tested equipment. By reading the signals in the positive direction and the negative direction, the information such as the actual transmission signal size, the reflected power size, the system load condition, the impedance matching state of the transmitter and the antenna, the system electrical connection condition and the like in the system can be obtained. The method is of great importance to real-time monitoring and control and operation safety of the system.
Directional couplers fall into two broad categories, lumped and distributed. A typical circuit is shown in figure 1.
The most important way to obtain broadband characteristics at present is to cascade the sections of quarter wavelength in multiple stages, and during design, a parity-mode analysis method is adopted to obtain the coupling coefficients of multiple stages and corresponding characteristic impedance. This approach is suitable in the rf microwave range, because of its short physical length, e.g. 1GHz-2GHz, 2GHz-6GHz, quarter wave in the order of centimetres, and the limitation of this approach is that the volume becomes less realistic when the low end of the operating frequency falls below 100MHz, e.g. 7.5 metres for a quarter wave at 30 MHz. Thus, two solutions have been proposed, one of which is to fold the circuit using a multilayer printed board; the other is to give up a quarter wavelength and perform a comprehensive design with an electrical length of one eighth or less, both of which have their limitations, such as increased loss, limited power capacity, increased thickness of the whole circuit, etc. of the folded circuit method, uneven coupling curve, poor coupling directivity, need of a large number of complex peripheral compensation circuits, repeated design iteration work, etc. By the two methods, the directional coupler working at 1MHz-100MHz and 30MHz-1GHz can be developed, and the passing power can reach 1 kW. However, both of these approaches are difficult to satisfy as the low end of the frequency continues to fall to kHz and the power continues to rise.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a cover high-power directional coupler of broadband of VLF-VHF frequency channel mainly solves current directional coupler loss increase, the limited problem of power capacity when the low frequency covers.
In order to achieve the above object, the utility model adopts the following technical scheme:
a broadband high-power directional coupler covering a VLF-VHF frequency band comprises a first coaxial transmission line with a ferrite core, two sampling comparison circuits, a main power channel and a coupling power output channel, wherein the two sampling comparison circuits are connected to two ends of the first coaxial transmission line, and the circuit structures of the two sampling comparison circuits are symmetrical relative to the middle of the first coaxial transmission line; the sampling comparison circuit comprises a second coaxial transmission line, a sampling resistor R3, a compensation capacitor C2, a resistor R2, a sampling resistor R3, a compensation capacitor C2, a resistor R1 and a resistor R4, wherein the inner conductor of the second coaxial transmission line is connected with the inner conductor of the first coaxial transmission line, the sampling resistor R3 is connected between the outer conductors of the first coaxial transmission line and the second coaxial transmission line, the compensation capacitor C2 is connected in parallel with two ends of the sampling resistor R3, the resistor R2 is connected with the common end of the outer conductor of the first coaxial transmission line, the sampling resistor R1 and the resistor R4 are connected with the other end of the resistor R2, and the compensation capacitor C1 is connected in parallel with two ends of the sampling resistor R1; the other free end of the sampling resistor R1 is connected with the other end of the inner conductor of the second coaxial transmission line, the other end of the outer conductor of the second coaxial transmission line is grounded, the main power channel is connected with the common end of the sampling resistor R1 and the inner conductor of the second coaxial transmission line, and the coupling power output channel is connected with the other free end of the resistor R4.
Furthermore, the main power channels in the two sampling comparison circuits are respectively a main power input channel and a main power output channel, and the corresponding coupled power output channels in the sampling comparison circuits are respectively a forward coupled power output channel and a reverse coupled power output channel.
Compared with the prior art, the utility model discloses following beneficial effect has:
the utility model discloses a coaxial transmission line and the hybrid circuit that total parameter resistance electric capacity constitutes utilize coaxial transmission line's the interior outer conductor electric current opposite characteristic, carry out the topological design of the sample comparison circuit that corresponds, the parasitic parameter of compensation and reduction resistance, make the utility model discloses a typical frequency of coupler is 9kHz ~ 250MHz, is greater than 3kW through power, and the loss is less than or equal to 0.2dB, and coupling flatness +/-0.5 dB, the directionality is more than or equal to 20 dB. The characteristic impedance in the whole frequency band is 50 omega, the existing radio frequency system can be conveniently accessed, and the transmission power exceeding 3kW can be monitored. And the directional coupler is composed of a coaxial transmission line and a forward and reverse sampling circuit. The forward and reverse sampling circuits are completely the same in structure, except that the signal flow directions in the circuits are different, and coupled signals with different forward and reverse directions are obtained by adding and subtracting the signals. Vice versa, if the input and output signals are reversed, the opposite forward and reverse coupling type output can be obtained.
Drawings
Fig. 1 is a schematic diagram of a typical circuit of a prior art directional coupler.
Fig. 2 is a schematic structural diagram of the present invention.
Fig. 3 is a schematic structural diagram of voltage and current transmission of the coaxial transmission line of the present invention.
Fig. 4 is a diagram of forward power coupling for the P3 port in the directional coupler.
Fig. 5 is a reverse power coupling diagram of the P4 port in the directional coupler.
FIG. 6 is a diagram showing simulation results of the 9 kHz-250 MHz directional coupler.
Detailed Description
The present invention will be further described with reference to the following description and examples, which include but are not limited to the following examples.
Examples
As shown in fig. 2, the utility model discloses a cover high-power directional coupler of broadband of VLF-VHF frequency channel, including the first coaxial transmission line b that has ferrite core C, connect in first coaxial transmission line both ends and circuit structure about two sampling comparison circuit of first coaxial transmission line middle part symmetry, two sampling circuit's structure is the same completely, and the signal flow in the circuit is different only, utilizes adding of signal and subtracting to obtain the coupling signal output of positive reverse difference. Vice versa, if the input and output signals are reversed, the opposite forward and reverse coupling type output can be obtained.
The sampling comparison circuit comprises a second coaxial transmission line, a sampling resistor R3, a compensation capacitor C2, a resistor R2, a sampling resistor R3, a compensation capacitor C2, a resistor R1 and a resistor R4, wherein the inner conductor of the second coaxial transmission line is connected with the inner conductor of the first coaxial transmission line, the sampling resistor R3 is connected between the outer conductors of the first coaxial transmission line and the second coaxial transmission line, the compensation capacitor C2 is connected in parallel with two ends of the sampling resistor R3, the resistor R2 is connected with the common end of the outer conductor of the first coaxial transmission line, the sampling resistor R1 and the resistor R4 are connected with the other end of the resistor R2, and the compensation capacitor C1 is connected in parallel with two ends of the sampling resistor R1; the other free end of the sampling resistor R1 is connected with the other end of the inner conductor of the second coaxial transmission line, the other end of the outer conductor of the second coaxial transmission line is grounded, the main power channel is connected with the common end of the sampling resistor R1 and the inner conductor of the second coaxial transmission line, and the coupling power output channel is connected with the other free end of the resistor R4. In fig. 2, P1 and P2 are main power channels, and P3 and P4 are forward and reverse coupled power outputs. If P1 is the power input, then P2 is the power output, P3 is the forward power coupling port, P4 is the reverse power coupling port; if P2 is the power input, then P1 is the power output, P4 is the forward power coupling port, and P3 is the reverse power coupling port.
The basic principle of the circuit utilizes the characteristic that the currents of the inner conductor and the outer conductor of the coaxial transmission line are equal in magnitude and opposite in direction, as shown in 0.
The voltage in the coaxial transmission line is for the voltage difference between the two conductors, the current flows in the two conductors respectively, and the formula of the voltage and the current on the coaxial line with any length l is shown as follows.
Wherein Z0Is the characteristic impedance of the coaxial line and gamma is the transmission characteristic of the coaxial line. Therefore, when the dimensions of the coaxial line are determined, the voltage and current at each point on the line can be calculated. If the voltage to ground at any point on the inner conductor is
The current is I (l), the voltage to ground on the outer conductor is
The current is-I (l).
The sampling resistors R1, R3, R5 and R7 respectively sample voltages from the inner conductor and the outer conductor of the input end and the output end, and the added and subtracted signals are obtained at ports P3 and P4 by utilizing the inherent characteristics of the coaxial inner conductor and the coaxial outer conductor that the current directions are opposite, so that the detection values of the forward power and the reverse power are obtained.
Shown in fig. 4 as part a of the directional coupler. When signals are input from the P1 port, the power transmission direction on the coaxial wire core is rightward, the current directions on R1 and R2 can be obtained through circuit analysis, and the voltage obtained by monitoring the P4 port and U are shown in the figure at the momentR1+UR2Proportional, and the greater the P1 port input power, the greater the detection voltage.
Shown in fig. 5 as part B of the directional coupler. At the same time as that in FIG. 4, the power transmission direction on the coaxial cable core is towards the right, and the current directions on R6 and R7 can be obtained through circuit analysis, and at this time, the voltage obtained by monitoring the P4 port and U are shown in the figureR7-UR6Proportional, and the greater the P1 port input power, the greater the detection voltage.
The voltage at the P3 port is much larger than that at the P4 port and is proportional to the input power at the P1 port by adjusting the resistance in the circuit, so that the P3 can indicate the forward coupling signal, whereas if the signal is input from the P2, which can be regarded as the reflected signal, the P4 port monitors the voltage and the UR7+UR6Is in direct proportion toIs the detection of the reflected signal. The difference between P3 and P4 indicates directionality.
In this embodiment, the resistance values of the sampling resistors R1 and R7 are higher according to the coupling ratio, and the requirements on power and voltage tolerance are also higher. The sampling resistors R3 and R5 have small resistance values, but pass large power and require small parasitic parameters.
The compensation capacitors C1, C2, C3 and C4 in the figure are for compensating parasitic inductance and parasitic capacitance of the resistor itself. Because the time constant difference of each RC circuit in the directional coupler is large, sampling signals cannot be aligned accurately in certain frequency bands, and the added and subtracted values have difference, so that the accuracy and the directivity of the coupling value are affected. Because parasitic parameters of different resistors have large difference and the same resistor can be distinguished due to discreteness, a capacitor is required to be added to make up and adjust a time constant of the forward and reverse sampling circuit, so that forward and reverse signals are superposed at correct time and are completely offset or strengthened, and then high directivity can be obtained. The forward and reverse signals are matched and accurately offset, and the coupling and directivity characteristics are improved. The time constant of the RC circuit is:
τ＝RC；
wherein, τ represents the time required for the voltage across the capacitor to rise to a maximum value of 0.63 times, and R and C are the resistance and the capacitance in the RC circuit, respectively.
For example, the sampling resistor R1 has a large resistance value, and a large parasitic capacitance is introduced; and the resistance of the sampling resistor R3 is smaller, and the parasitic capacitance is also smaller. Their time constant τ will be different by up to 105A rank. It is therefore necessary to adjust the time constants of the two circuits to reduce the difference.
Therefore, the capacitors C1, C2, C3 and C4 are added to adjust and compensate parasitic capacitances of R1, R3, R5 and R7, respectively, so that time constants of the RC circuits do not affect the coupling accuracy and the directivity.
As can be seen from the simulation results in FIG. 6, the loss of the directional coupler is less than or equal to 0.2dB, the coupling flatness is less than or equal to +/-0.5 dB, and the directivity is greater than or equal to 20 dB. The selected coaxial cable and the divider resistor meet the high-power working requirement of 3 kW. And when the power is required to be higher or the device works in a high-temperature environment, a radiator and a forced air cooling device can be additionally arranged in the device in practical use.
Through the design, the utility model discloses a coaxial transmission line and the hybrid circuit that total parameter resistance electric capacity constitutes utilize coaxial transmission line's interior outer conductor electric current opposite characteristic, carry out the topological design of the sample comparison circuit that corresponds, the parasitic parameter of compensation and reduction resistance for this directional coupling circuit can work at 9kHz ~ 100MHz frequency channel simultaneously, is greater than 3kW through power, and the loss is less than or equal to 0.2dB, and coupling flatness +/-0.5 dB, and the directionality is more than or equal to 20 dB. Each port is matched with a 50 omega system, and can be conveniently accessed into a radio frequency microwave communication and test system to play a role in monitoring and protection. Therefore, the method has constant and high use value and popularization value.
The above embodiment is only one of the preferred embodiments of the present invention, and should not be used to limit the protection scope of the present invention, but all the insubstantial changes or modifications made in the spirit and the idea of the main design of the present invention, the technical problems solved by the embodiment are still consistent with the present invention, and all should be included in the protection scope of the present invention.
Claims (2)
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121079157.XU CN214957297U (en) | 2021-05-19 | 2021-05-19 | A broadband high-power directional coupler covering the VLF-VHF frequency band |
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| CN202121079157.XU CN214957297U (en) | 2021-05-19 | 2021-05-19 | A broadband high-power directional coupler covering the VLF-VHF frequency band |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113300070A (en) * | 2021-05-19 | 2021-08-24 | 成都四威功率电子科技有限公司 | A broadband high-power directional coupler covering VLF-VHF frequency band and its realization method |
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2021
- 2021-05-19 CN CN202121079157.XU patent/CN214957297U/en not_active Withdrawn - After Issue
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113300070A (en) * | 2021-05-19 | 2021-08-24 | 成都四威功率电子科技有限公司 | A broadband high-power directional coupler covering VLF-VHF frequency band and its realization method |
| CN113300070B (en) * | 2021-05-19 | 2025-03-28 | 成都四威功率电子科技有限公司 | A broadband high-power directional coupler covering VLF-VHF frequency band and its implementation method |
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