CN207053506U - A kind of High Precision Voltage Adjustable control balanced device - Google Patents
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Abstract
A kind of High Precision Voltage Adjustable control balanced device is the utility model is related to, the attenuation characteristic of the coaxial cable suitable for CATV systems compensates, including adjustable voltage-controlled attenuator chip and impedance matching element T1；Wherein, inductance L1 and electric capacity C1 the first series vias in series；Resistance R1 and electric capacity C3 the second series vias in series；The output pin of the adjustable voltage-controlled attenuator chip is connected with electric capacity C4, and electric capacity C4 another pin is connected with 1 pin of the impedance matching element T1, and 3 pin of the impedance matching element T1 are connected with electric capacity C5, forms the 3rd series via；First series via, second series via, the 3rd series via are in parallel；The control terminal Access Control voltage of the adjustable voltage-controlled attenuator chip, the control voltage by changing input, realize continuously adjusting for adjustable voltage-controlled attenuator chip attenuation.
Description
Technical Field
The utility model relates to an electronic device, concretely relates to novel adjustable voltage-controlled equalizer of high accuracy is suitable for and compensates the attenuation characteristic of the coaxial cable in the CATV system, belongs to the wire communication field.
Background
In the CATV system, the attenuation characteristics of the coaxial cable for transmitting audio and video signals vary with frequency, so that in practical applications, it is necessary to design an equalization network to compensate the attenuation characteristics of the coaxial cable, so as to improve the flatness of the system in the whole frequency band. The equalizer is a bridge T-shaped four-end and high-pass network formed by an inductor, a capacitor and a resistor, the inclination of amplitude-frequency characteristics can be changed by adjusting a reactance element, namely, the attenuation of low-frequency signals is large, the attenuation of high-frequency signals is reduced in sequence, which is just opposite to the attenuation characteristics of cables, so that the attenuation amplitude of the cables to signals with different frequencies is compensated. Equalization networks can be divided into fixed equalizers and adjustable equalizers. In CATV systems, fixed equalizers, tunable equalizers are used. The quality of the system has a large influence on the system, and the performance of the system is usually measured by indexes such as balance, insertion loss, balance deviation, reflection loss and the like.
Fixed slope CATV amplitude equalization networks are often used to compensate for the attenuation of certain lengths of cable, while variable slope amplitude equalizers may be used to compensate for the attenuation of different lengths of cable. The fixed equalizer is composed of passive devices such as an inductor, a capacitor and a resistor. The fixed equalizer is usually a bridge T-shaped passive four-terminal network, which overcomes the instability of a variable equalizer bridge T-shaped attenuation network and is widely applied. Its advantages are simple circuit and low cost. The disadvantage is that the equalization amount is fixed and equalization adjustment needs to be realized by replacing equalizers with different equalization amounts. It is not flexible enough to realize remote control.
The adjustable equalizer is formed by replacing a fixed attenuation network with an adjustable attenuation network and adding an impedance matching element on the basis of the fixed equalizer. The adjustable equalizer can realize the adjustment of the equalization amount within a certain range. The adjustable attenuators are classified into two types, one is a passive adjustable equalizer, and a typical circuit thereof is as shown in figure 1, namely R is0、R1、R2The formed attenuation network is made into a pluggable insertion sheet, and the balance adjustment of different slopes can be realized by replacing different insertion sheets. The other is an active adjustable attenuator. Active sourceThe implementation method of the adjustable equalizer is generally to replace R in FIG. 1 with two variable resistance diodes2、R2And controlling the resistance of the variable resistance diode by using the voltage to realize the adjustment of the attenuation size. The stability of such equalizers depends on the stability of the regulated voltage, and deviations in the voltage can result in deviations in the equalization amount. At present, a Digital controlled step attenuator (Digital stepattentuator) chip is used to replace the adjustable attenuation network. The amount of attenuation of the step attenuator chip is generally controlled by the SPI bus. The principle is that the attenuation value is switched by controlling an internal switch of a chip through a digital signal. Its advantages are convenient application, remote control by cooperating with network management software, wide variation range and automatic control. The disadvantage is that the variation of the attenuation can only be increased or decreased according to a certain step, and is not flexible. The adjustable equalizer can realize the fixed impedance condition and different equalization requirements, and when the adjustable equalizer is designed in detail, the fixed impedance condition is not easy to realize when the adjustable equalizer realizes the large equalization adjustment, and the adjustment precision and stability, the insertion loss and the reflection loss of the adjustable equalizer are not as good as those of the fixed equalizer.
With the development of DOCSIS 3.1 technology, the frequency of CATV systems has been expanded from 1GHz to 1.2GHz, and at the same time, higher requirements are placed on the flatness of signals. The attenuation characteristics of coaxial cables vary with frequency. While coaxial cables of different materials have different attenuation characteristics. At the same time, temperature also affects its attenuation characteristics. The slope of the gain curve of the main amplifier in the existing network is also affected by temperature. This requires an adjustable equalizer to compensate for it. This puts new demands on the precision, stability and remote control capabilities of the attenuator.
Disclosure of Invention
In order to solve the above technical problem, the utility model provides a high-precision adjustable voltage-controlled equalizer, which comprises an adjustable voltage-controlled attenuator chip and an impedance matching element T1; wherein,
the inductor L1 and the capacitor C1 are connected in series to form a first series circuit;
the resistor R1 and the capacitor C3 are connected in series to form a second series path;
an output pin of the adjustable voltage-controlled attenuator chip is connected in series with a capacitor C4, the other pin of the capacitor C4 is connected with a pin 1 of the impedance matching element T1, and a pin 3 of the impedance matching element T1 is connected in series with a capacitor C5 to form a third series path; the pin 2 of the impedance matching element T1 is connected with the GND pin of the adjustable voltage-controlled attenuator chip and is connected to the ground level through an inductor L2 and a capacitor C2 which are connected in parallel;
the first series circuit, the second series circuit and the third series circuit are connected in parallel, an input pin of the inductor L1, the resistor R1 and the adjustable voltage-controlled attenuator chip is connected to an input end of the adjustable voltage-controlled equalizer, and the capacitor C1, the capacitor C3 and the capacitor C5 are connected to an output end of the adjustable voltage-controlled equalizer;
and the control end of the adjustable voltage-controlled attenuator chip is connected with a control voltage for continuously adjusting the attenuation of the adjustable voltage-controlled attenuator chip.
In the above technical solution, the impedance matching element T1 is a balun and is formed by winding a two-hole high-frequency magnetic core.
In the above technical solution, the adjustable voltage-controlled attenuator chip includes a pi-type attenuation network composed of four voltage-controlled variable resistance diodes.
In the above technical solution, the chip of the adjustable voltage-controlled attenuator is RFSA 3043.
The utility model discloses following technological effect has been gained:
the utility model discloses compare in traditional fixed attenuator and inserted sheet formula adjustable attenuator, but have remote control's function. The temperature compensation EQ function can be realized by combining with a temperature detection chip. Automatic temperature compensation of the amplifier can be achieved. This greatly reduces the cost of manual maintenance of the amplifier during use.
Compared with the traditional electric control adjustable equalizer, the method has the advantages of low insertion loss, high precision and continuously variable slope. The current step digital attenuator has a minimum step of 0.5dB, and the equalizer slope based on the step digital attenuator can only change by 0.5 dB. And in the use process, signals are interrupted instantaneously when the switch is switched. The utility model provides an equalizer can not appear this problem. In a specific use process, high-precision temperature compensation can be realized by high-precision slope change, and the performance of a product is further improved.
Drawings
FIG. 1 is a schematic diagram of a typical fixed equalization network circuit in the prior art;
fig. 2 is a schematic diagram of a continuously adjustable equalization network circuit provided by the present invention;
FIG. 3 is a circuit diagram of an exemplary application of the present invention;
fig. 4 is a graph of the slope change of 10-18dB according to the present invention.
Detailed Description
To facilitate understanding and implementing the present invention by those of ordinary skill in the art, the present invention will be described in further detail with reference to the accompanying drawings and detailed description.
The utility model provides a novel adjustable voltage-controlled equalizer of high accuracy. The circuit design block diagram is shown in fig. 2. In the figure, an inductor L1 is connected in series with a capacitor C1, a resistor R1 is connected in series with a capacitor C3, an output pin of the adjustable voltage-controlled attenuator chip is connected in series with a capacitor C4, the other pin of the capacitor C4 is connected with a pin 1 of an impedance matching element T1, and a pin 3 of the impedance matching element T1 is connected in series with a capacitor C5. The series networks are connected in parallel, an inductor L1, a resistor R1 and an input pin of the adjustable voltage-controlled attenuator chip are connected into an input end of the circuit, and a capacitor C1, a capacitor C3 and a capacitor C5 are connected into an output end of the circuit. The pin 2 of the impedance matching element T1 is connected with the GND pin of the adjustable voltage-controlled attenuator chip, and is connected to the ground through the inductor L2 and the capacitor C2 which are connected in parallel. The control end of the adjustable voltage-controlled attenuator chip is connected with control voltage. The adjustable voltage-controlled attenuator chip can realize continuous adjustment of attenuation amount by changing input control voltage.
The functional block diagram inside the voltage-controlled attenuator chip is shown in the dotted frame in fig. 2, and the chip includes a pi-type attenuation network composed of four voltage-controlled variable-resistance diodes. The whole link forms an adjustable equalization network for changing the slope of the frequency spectrum of the broadband radio frequency signal.
The characteristic of the voltage-controlled variable resistance diode is that when the forward bias voltage of two ends is increased, the forward current of the diode is increased, and the equivalent internal resistance of the diode is reduced; when the forward bias voltage at the two ends of the diode is reduced, the forward current of the diode is reduced, and the equivalent internal resistance of the diode is increased.
In the internal principle circuit of the voltage-controlled attenuator chip shown in the dashed line box in fig. 2, a control voltage and a 5V reference voltage are respectively connected to the input end of an operational amplifier, and the control voltage is connected to a point a through a resistor R11, when the control voltage is increased, the voltage at the point a is increased, and the resistances of two voltage-controlled variable-resistance diodes (D1 and D2) connected to the point a are reduced. When the control voltage is 5V, the resistance is the smallest. At this time, the output of the comparator formed by the operational amplifier is 0V, so the voltage at the point B is 0V, and the resistances of the two voltage-controlled variable-resistance diodes (D3 and D4) connected to the point C are infinite. At this time, the attenuation of the entire attenuator is minimized. When the control voltage is decreased, the voltage at the point a is decreased, and the resistances of the two voltage-controlled variable resistance diodes (D1 and D2) connected to the point a are increased accordingly. When the voltage at the point a decreases to a certain value, the resistances of the two voltage-controlled variable-resistance diodes (D1 and D2) connected to the point a become infinite. At this time, the output of the comparator constituted by the operational amplifier is maximum, and the voltage at the point B is maximum. The resistance of the two voltage controlled variable resistance diodes (D3 and D4) connected to point C is minimized. The attenuation value of the attenuation chip reaches the maximum value at this time. I.e., the control voltage increases and the attenuation chip attenuation decreases. The continuous variation of the voltage can cause the attenuation amount of the attenuation chip to continuously vary.
The input and output impedance of the equalizer can be improved by changing the value of the resistor R1 in the circuit shown in FIG. 2, and large reflection loss is obtained, a small-capacity capacitor C3 is connected in series behind the resistor R1, and the capacitor C3 has a frequency compensation effect on the resistor R1. The inductor L1 and the capacitor C1 form a series resonant network, and the upper limit cut-off frequency of the equalizer can be adjusted by adjusting the parameters of the inductor L1 and the capacitor C1. The inductor L2 and the capacitor C2 form a parallel resonant network, and the parameters of the capacitor C2 can also adjust the upper limit frequency of the equalizer and the linearity of a low-end equalization curve by adjusting the inductor L2. T1 is an impedance matching element (i.e. balun) made by winding a two-hole high-frequency core, and can perform impedance conversion by changing the ratio of the number of turns in the two holes to achieve the effect of impedance matching. The number of winding turns of the impedance matching element T1 affects the insertion loss and return loss of the equalizer and needs to be selected according to the actual link conditions. In practical use, when the impedance mismatch condition occurs in the link, the impedance mismatch condition can be adjusted by exchanging different numbers of balun. Compared with the existing numerical control step attenuator, the constant impedance condition of the voltage-controlled attenuator is not easy to realize. Because the numerical control attenuator is an attenuator circuit integrating different attenuation values in the attenuator, and is switched by a switch. The digital control attenuator chip solidifies and finishes the input and output impedance matching of each attenuation value, and the voltage control attenuator is difficult to ensure that the input and output impedance is always unchanged at any attenuation value because the attenuation value is continuously variable. The capacitors C4, C5 across the impedance matching element T1 are used to assist in adjusting the impedance matching of the impedance matching element T1. The voltage-controlled attenuator can be continuously adjusted by continuously changing the control voltage of the voltage-controlled attenuator, and can be conveniently adjusted when used in a circuit.
The stability and accuracy of the equalizer is determined by the control voltage. If the control voltage changes, the slope of the equalization network also changes correspondingly. To solve this problem, a DAC chip may be used for control. Voltage controlled attenuator chips according to the schematic block diagram of fig. 2 (circuit within the dashed box) can be used to implement such a continuously adjustable equalization network. Such as: RFSA3043, and the like.
FIG. 3 shows the application of the present invention as a high precision continuously adjustable EQ for temperature compensation in DOCSIS 3.1 trunk amplifier. The circuit design is shown in fig. 3. The voltage controlled attenuation chip selects RFSA 3043. The peripheral circuit design is performed as shown in fig. 2. The control voltage signal given by the MCU is amplified by an inverting amplifier and then input into a voltage control pin of the chip. Thus, the 0-3V signal output by the MCU is converted into the 0-5V control signal required by the chip. Good impedance matching can be obtained by properly selecting the input-output capacitance inductance and the values of L67 and C135. Adjusting the values of C286, L99 can adjust the frequency of the highest point of the EQ circuit. The specific appropriate value can be obtained through simulation or actual debugging.
Tests show that the slope can be changed in 0.1dB step. Specific test results are shown in table 1. From the results in the table, it can be seen that the change in the flatness of the curve due to the change in slope is very slight, being only ± 0.07 dB.
TABLE 110-11 dB slope change
As shown in Table 2, when the slope of the EQ varies from 10-18dB, the flatness of the gain curve of the whole link does not vary by more than + -0.21 dB. It can thus be shown that the change in EQ has very little effect on the overall link metrics.
Therefore, the slope of the gain curve can be adjusted with high precision within a wide range by using the scheme as the high-precision continuously adjustable EQ for temperature compensation, so that the change of the whole gain curve caused by the chip performance change due to the temperature change can be compensated, and the flatness of the whole gain curve can not be greatly influenced. The amplifier can achieve stable output in the whole temperature range only by being matched with software for writing.
Table 210-18 dB slope change
| Theoretical value/dB | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |
| Test value/dB | 10.03 | 11.18 | 12.12 | 12.96 | 14.20 | 15.15 | 16.18 | 16.99 | 17.93 |
| flatness/dB | ±0.49 | ±0.42 | ±0.37 | ±0.33 | ±0.28 | ±0.28 | ±0.27 | ±0.30 | ±0.35 |
While the invention has been particularly shown and described with reference to a particular embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. Such modifications are intended to fall within the scope of the appended claims.
Claims (4)
1. A high-precision adjustable voltage-controlled equalizer is characterized in that: the circuit comprises an adjustable voltage-controlled attenuator chip and an impedance matching element T1; wherein,
the inductor L1 and the capacitor C1 are connected in series to form a first series circuit;
the resistor R1 and the capacitor C3 are connected in series to form a second series path;
an output pin of the adjustable voltage-controlled attenuator chip is connected in series with a capacitor C4, the other pin of the capacitor C4 is connected with a pin 1 of the impedance matching element T1, and a pin 3 of the impedance matching element T1 is connected in series with a capacitor C5 to form a third series path; the pin 2 of the impedance matching element T1 is connected with the GND pin of the adjustable voltage-controlled attenuator chip and is connected to the ground level through an inductor L2 and a capacitor C2 which are connected in parallel;
the first series circuit, the second series circuit and the third series circuit are connected in parallel, an input pin of the inductor L1, the resistor R1 and the adjustable voltage-controlled attenuator chip is connected to an input end of the adjustable voltage-controlled equalizer, and the capacitor C1, the capacitor C3 and the capacitor C5 are connected to an output end of the adjustable voltage-controlled equalizer;
and the control end of the adjustable voltage-controlled attenuator chip is connected with a control voltage for continuously adjusting the attenuation of the adjustable voltage-controlled attenuator chip.
2. The high precision adjustable voltage controlled equalizer of claim 1, wherein: the impedance matching component T1 is a balun and is formed by winding a two-hole high-frequency magnetic core.
3. The high precision adjustable voltage controlled equalizer of claim 1, wherein: the adjustable voltage-controlled attenuator chip comprises a pi-type attenuation network consisting of four voltage-controlled variable-resistance diodes.
4. The high precision adjustable voltage controlled equalizer of claim 1, wherein: the chip of the adjustable voltage-controlled attenuator is RFSA 3043.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108574537A (en) * | 2018-07-19 | 2018-09-25 | 苏州市高事达信息科技股份有限公司 | A kind of electric adjustable balancing control circuit of photoreceiver |
| CN108964683A (en) * | 2018-06-05 | 2018-12-07 | 海能达通信股份有限公司 | A kind of RF transmit-receive circuit and mobile terminal |
| CN109030900A (en) * | 2018-06-28 | 2018-12-18 | 宁波环球广电科技有限公司 | CATV blade inserting fixed attenuator identification circuit |
| CN109756691A (en) * | 2018-11-30 | 2019-05-14 | 宁波环球广电科技有限公司 | A kind of automatically controlled equalization compensation device of general purpose type high accuracy |
| CN110311645A (en) * | 2019-05-28 | 2019-10-08 | 西安空间无线电技术研究所 | A kind of electric modulation balanced device of novel topological structure |
| CN111697994A (en) * | 2020-06-24 | 2020-09-22 | 天津中科海高微波技术有限公司 | Novel adjustable amplitude equalizer |
| CN112583365A (en) * | 2020-12-11 | 2021-03-30 | 重庆西南集成电路设计有限责任公司 | Bit-sensitive trans-impedance amplifier with temperature compensation and automatic attenuation functions |
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2017
- 2017-08-30 CN CN201721093578.1U patent/CN207053506U/en active Active
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108964683A (en) * | 2018-06-05 | 2018-12-07 | 海能达通信股份有限公司 | A kind of RF transmit-receive circuit and mobile terminal |
| CN109030900A (en) * | 2018-06-28 | 2018-12-18 | 宁波环球广电科技有限公司 | CATV blade inserting fixed attenuator identification circuit |
| CN108574537A (en) * | 2018-07-19 | 2018-09-25 | 苏州市高事达信息科技股份有限公司 | A kind of electric adjustable balancing control circuit of photoreceiver |
| CN109756691A (en) * | 2018-11-30 | 2019-05-14 | 宁波环球广电科技有限公司 | A kind of automatically controlled equalization compensation device of general purpose type high accuracy |
| CN110311645A (en) * | 2019-05-28 | 2019-10-08 | 西安空间无线电技术研究所 | A kind of electric modulation balanced device of novel topological structure |
| CN110311645B (en) * | 2019-05-28 | 2023-03-31 | 西安空间无线电技术研究所 | Novel topological structure's electricity modulation amplitude equalizer |
| CN111697994A (en) * | 2020-06-24 | 2020-09-22 | 天津中科海高微波技术有限公司 | Novel adjustable amplitude equalizer |
| CN111697994B (en) * | 2020-06-24 | 2021-07-09 | 天津中科海高微波技术有限公司 | Novel adjustable amplitude equalizer |
| CN112583365A (en) * | 2020-12-11 | 2021-03-30 | 重庆西南集成电路设计有限责任公司 | Bit-sensitive trans-impedance amplifier with temperature compensation and automatic attenuation functions |
| CN112583365B (en) * | 2020-12-11 | 2023-05-12 | 重庆西南集成电路设计有限责任公司 | Bit-sensitive transimpedance amplifier with temperature compensation and automatic attenuation functions |
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