CN111641394A - Low-impedance signal amplifying circuit for high-impedance system and amplifying method thereof - Google Patents
Low-impedance signal amplifying circuit for high-impedance system and amplifying method thereof Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/56—Modifications of input or output impedances, not otherwise provided for
- H03F1/565—Modifications of input or output impedances, not otherwise provided for using inductive elements
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/68—Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics
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- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/10—Adaptations for transmission by electrical cable
- H04N7/102—Circuits therefor, e.g. noise reducers, equalisers, amplifiers
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Abstract
The invention discloses a low-impedance signal amplifying circuit for a high-impedance system and an amplifying method thereof. A low impedance signal amplification method for high impedance systems for matching a high impedance system, comprising the steps of: the converted electric signal is output by the optical fiber detector U2, converted into a 50-ohm impedance signal by the first impedance converter B1, amplified by the first impedance chip U1, automatically controlled by the AGC automatic control circuit to output level, amplified by the second impedance chip U3, and converted into a 75-ohm impedance signal by the second impedance converter B2, so that the high-impedance optical fiber detector is suitable for a 75-ohm impedance high-impedance system. The invention discloses a low-impedance signal amplifying circuit for a high-impedance system and an amplifying method thereof, wherein an amplifying IC with 50 ohm impedance is applied to a cable television system with 75 ohm impedance.
Description
Technical Field
The invention belongs to the technical field of cable television systems, and particularly relates to a low-impedance signal amplification circuit for a high-impedance system and a low-impedance signal amplification method for the high-impedance system.
Background
The invention patent with publication number CN100417217C, entitled cable television delivery system network controller, discloses in its technical solution "the apparatus is capable of inserting local availability signals and of selecting digital program signals received from external sources, the apparatus comprising: means for receiving said digital program signal; a digital logic circuit connected to the receiving means, in which said local availability signal can be inserted and in which said digital program signal can be selected; a processor operatively connected to the digital logic circuit, wherein insertion of said local availability signal is controlled and wherein selection of said digital program signal is controlled; and means for transmitting a program, the means being operatively connected to the digital logic circuit, wherein the selected digital program signal is transmitted to the subscriber location, and wherein the local availability signal that has been inserted is transmitted to the subscriber location; the apparatus for receiving the digital program signal further comprises: an integrated receiver demodulator, comprising: a means for receiving an RF signal; means for amplifying the received RF signal, wherein the amplifying means minimizes the amount of amplified noise; a means for demodulating the amplified signal; means for filtering the demodulated signal; and a means for transmitting the demodulated signal; and a demultiplexer comprising: means for separating the transmitted signal into a plurality of components, wherein each component contains video and audio data for a single program; and a means for extracting data from the transmitted signal ".
Taking the above patent as an example, in general, in cable television systems, the impedance is 75 ohms, and in other communication systems, the impedance is substantially 50 ohms. On the other hand, other communication systems are larger and wider than cable television systems, the number of amplification chips in the market is larger than that of cable television systems, the price is relatively lower, and the application of an amplification IC with 50 ohm impedance to a cable television system with 75 ohm impedance is not seen in the industry, and further improvement is needed.
Disclosure of Invention
The present invention addresses the above-identified deficiencies of the prior art by providing a low impedance signal amplification circuit for a high impedance system and a low impedance signal amplification method for a high impedance system.
The invention discloses a low-impedance signal amplifying circuit for a high-impedance system and an amplifying method thereof, and mainly aims to apply (access) an amplifying IC with 50 ohm impedance (low impedance) to a cable television system with 75 ohm impedance (high impedance).
The invention discloses a low impedance signal amplifying circuit and an amplifying method thereof for a high impedance system, and the low impedance signal amplifying circuit and the amplifying method thereof are used for converting an electric signal converted by an optical fiber detector U2 into a 50 ohm impedance signal through a first impedance converter B1, then the signal is amplified by a first impedance chip (50 ohm), then the signal is automatically controlled to output level through an AGC automatic control circuit, then the signal is amplified by a second impedance chip (50 ohm), and finally the signal is converted into a 75 ohm impedance signal through a second impedance converter B2, so that the low impedance signal amplifying circuit is suitable for a 75 ohm impedance cable television system.
The invention adopts the following technical scheme that the low-impedance signal amplification circuit for the high-impedance system is used for matching a high-impedance system, and comprises the following components:
a fiber detector U2 and a first impedance converter B1, wherein a first branch of the output end of the fiber detector U2 is connected to a first end of the first impedance converter B1 through an inductor L1;
a first impedance chip U1, wherein the third terminal of the first impedance transformer B1 is connected to the No. 1 terminal of the first impedance chip U1 through a capacitor C4;
an automatic AGC control circuit, which comprises a Pi-type voltage-controlled attenuation chip D1 with 4 diodes, wherein the No. 3 end of the first impedance chip U1 is connected to the input end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes through a capacitor C37, a resistor R11 and a capacitor C38 in sequence;
the output end of the Pi type voltage-controlled attenuation chip D1 with 4 diodes is connected to the No. 1 end of the second impedance chip U3 through a capacitor C13, a resistor R37 and a capacitor C14;
the No. 3 end of the second impedance chip U3 is connected to the first end of the second impedance converter B2 through a capacitor C15;
the signal protection circuit comprises an inductor L6, and the third end of the second impedance converter B2 is connected to one end of the inductor L6 through a capacitor C18, a capacitor C19 and a capacitor C17 in sequence;
an RF signal output circuit, the RF signal output circuit includes an RF port F1, the other end of the inductor L6 is connected to the No. 1 terminal of the RF port F1 through a capacitor C22, and the RF port F1 is further connected to the high impedance system.
According to the above technical solution, as a further preferable technical solution of the above technical solution, the low impedance signal amplifying circuit for a high impedance system further includes an AD collecting and amplifying circuit, the AD collecting and amplifying circuit includes an AD converting chip U5, and the second branch of the output end of the optical fiber probe U2 is connected to the No. 3 terminal of the AD converting chip U5 through an inductor L3 and a resistor R6.
According to the above technical solution, as a further preferable technical solution of the above technical solution, one end of a capacitor C6 and one end of a resistor R5 connected in parallel to each other are connected between a common end of the inductor L3 and the resistor R6, one end of a capacitor C10 is connected between a common end of the resistor R6 and the No. 3 end of the AD conversion chip U5, and the other end of the capacitor C6, the other end of the resistor R5 and the other end of the capacitor C10 are grounded in common.
According to the above technical solution, as a further preferable technical solution of the above technical solution, the low impedance signal amplifying circuit for a high impedance system further includes an MCU control circuit, the MCU control circuit includes an MCU chip U4, wherein:
the No. 7 end of the MCU chip U4 is connected with the No. 1 end of the AD conversion chip U5 through a resistor R15;
the No. 5 end of the MCU chip U4 is connected to the No. 5 end of the AD conversion chip U5 through a resistor R20.
According to the above technical solution, as a further preferable technical solution of the above technical solution, the resistance value of the first impedance chip U1 is 50 ohms.
According to the above technical solution, as a further preferable technical solution of the above technical solution, the resistance value of the second impedance chip U3 is 50 ohms.
According to the above-described aspect, as a more preferable aspect of the above-described aspect, the high impedance system is embodied as a cable television system.
According to the above aspect, as a more preferable aspect of the above aspect, the impedance of the cable television system is 75 ohms.
The invention also discloses a low impedance signal amplification method for a high impedance system, which is used for matching the high impedance system and comprises the following steps: the converted electric signal is output by the optical fiber detector U2, converted into a 50-ohm impedance signal by the first impedance converter B1, amplified by the first impedance chip U1, automatically controlled by the AGC automatic control circuit to output level, amplified by the second impedance chip U3, and converted into a 75-ohm impedance signal by the second impedance converter B2, so that the high-impedance optical fiber detector is suitable for a 75-ohm impedance high-impedance system.
According to the above technical solution, as a further preferable technical solution of the above technical solution, a first branch of the output end of the optical fiber detector U2 is connected to a first end of the first impedance transformer B1 through an inductor L1;
the third end of the first impedance converter B1 is connected to the No. 1 end of the first impedance chip U1 through a capacitor C4;
the AGC automatic control circuit comprises a Pi-type voltage-controlled attenuation chip D1 with 4 diodes, wherein the No. 3 end of the first impedance chip U1 is connected to the input end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes through a capacitor C37, a resistor R11 and a capacitor C38 in sequence;
the output end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes is connected to the No. 1 end of the second impedance chip U3 through a capacitor C13, a resistor R37 and a capacitor C14;
the terminal 3 of the second impedance chip U3 is connected to the first terminal of the second impedance transformer B2 through a capacitor C15.
The low-impedance signal amplifying circuit for the high-impedance system and the amplifying method thereof have the advantages that the amplifying IC with 50 ohm impedance (low impedance) is applied to (connected into) a cable television system with 75 ohm impedance (high impedance).
Drawings
Fig. 1 is a schematic diagram of a circuit topology of several circuits such as an AGC automatic control circuit, a signal protection circuit, etc. according to the present invention.
Fig. 2 is a schematic diagram of a circuit topology structure of a plurality of circuits such as an MCU control circuit, an AD acquisition and amplification circuit, and the like.
Fig. 3 is a schematic diagram of the circuit topology of the power supply circuit of the present invention.
Detailed Description
The invention discloses a low-impedance signal amplifying circuit for a high-impedance system and a low-impedance signal amplifying method for the high-impedance system, and the specific implementation mode of the invention is further described in combination with the preferred embodiments.
Referring to fig. 1 to 3 of the drawings, fig. 1 shows a circuit topology of several circuits such as an AGC automatic control circuit for a low impedance signal amplification circuit of a high impedance system and an amplification method thereof; fig. 2 shows a circuit topology of several circuits such as a low impedance signal amplifying circuit for a high impedance system and an MCU control circuit of an amplifying method thereof; fig. 3 shows a circuit topology of a power supply circuit for a low impedance signal amplifying circuit of a high impedance system and an amplifying method thereof.
It should be noted that "the first impedance IC" and "the first impedance chip" that may be involved in the embodiments of the present invention are the same concept and are not differentiated.
It should be noted that "the second impedance IC" and "the second impedance chip" that may be involved in the embodiments of the present invention are the same concept and are not differentiated.
Preferred embodiments.
Preferably, the low impedance signal amplifying circuit for high impedance system is used for matching a high impedance system, and the low impedance signal amplifying circuit for high impedance system comprises:
a fiber detector U2 and a first impedance converter B1, wherein a first branch of the output end of the fiber detector U2 is connected to a first end of the first impedance converter B1 through an inductor L1;
a first impedance chip U1, wherein the third terminal of the first impedance transformer B1 is connected to the No. 1 terminal of the first impedance chip U1 through a capacitor C4;
an automatic AGC control circuit, which comprises a Pi-type voltage-controlled attenuation chip D1 with 4 diodes, wherein the No. 3 end of the first impedance chip U1 is connected to the input end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes through a capacitor C37, a resistor R11 and a capacitor C38 in sequence;
the output end of the Pi type voltage-controlled attenuation chip D1 with 4 diodes is connected to the No. 1 end of the second impedance chip U3 through a capacitor C13, a resistor R37 and a capacitor C14;
the No. 3 end of the second impedance chip U3 is connected to the first end of the second impedance converter B2 through a capacitor C15;
the signal protection circuit comprises an inductor L6, and the third end of the second impedance converter B2 is connected to one end of the inductor L6 through a capacitor C18, a capacitor C19 and a capacitor C17 in sequence;
an RF signal output circuit, the RF signal output circuit includes an RF port F1, the other end of the inductor L6 is connected to the No. 1 terminal of the RF port F1 through a capacitor C22, and the RF port F1 is further connected to the high impedance system.
Further, the low impedance signal amplifying circuit for the high impedance system further comprises an AD collecting and amplifying circuit, the AD collecting and amplifying circuit comprises an AD conversion chip U5, and a second branch of the output end of the optical fiber detector U2 is connected to the terminal 3 of the AD conversion chip U5 through an inductor L3 and a resistor R6.
One end of a capacitor C6 and one end of a resistor R5 which are connected in parallel are connected between the common end of the inductor L3 and the resistor R6, one end of a capacitor C10 is connected between the common end of the resistor R6 and the No. 3 end of the AD conversion chip U5, and the other end of the capacitor C6, the other end of the resistor R5 and the other end of the capacitor C10 are grounded in common.
Further, the second terminal of the first impedance converter B1 is connected to a 5V power supply through a resistor R1.
The common terminal between the resistor R1 and the 5V power supply is connected into one terminal of a capacitor C1 and one terminal of a capacitor C2 which are connected in parallel, and the other terminal of the capacitor C1 and the other terminal of the capacitor C2 are connected to the ground in common.
Further, the common terminal between the terminal 3 of the first impedance chip U1 and the capacitor C37 is connected to a 5V power supply through an inductor L2 and a resistor R9.
Two ends of the resistor R9 are respectively connected to one end of a capacitor C9 and one end of a capacitor C11 which are connected in parallel, and the other end of the capacitor C9 and the other end of the capacitor C11 are commonly grounded.
Furthermore, a capacitor C12 is connected in parallel to two ends of the resistor R11.
Further, the Pi-type voltage-controlled attenuation chip D1 with 4 diodes preferably adopts HSMP 3816.
Further, a first branch of a common terminal between the resistor R37 and the capacitor C14 is grounded through a resistor RZ1, a capacitor CZ1 and an inductor LC1, and a second branch of the common terminal between the resistor R37 and the capacitor C14 is grounded through a capacitor C14.
Further, the common terminal between the terminal 3 of the second impedance chip U3 and the capacitor C15 is connected to a 5V power supply through an inductor L5 and a resistor R13.
Two ends of the resistor R13 are respectively connected to one end of a capacitor C24 and one end of a capacitor C23 which are connected in parallel, and the other end of the capacitor C24 and the other end of the capacitor C23 are commonly grounded.
Further, the common terminal between the capacitor C19 and the capacitor C17 is grounded through an inductor L8.
Further, the common terminal between the capacitor C17 and the inductor L6 is grounded through a resistor R12.
Further, the common terminal between the inductor L6 and the capacitor C22 is grounded through two switching diodes D7 and D9, which are cascaded with each other.
Further, the common terminal between the capacitor C22 and the terminal No. 1 of the RF port F1 is grounded through a ceramic gas discharge tube D8.
Further, the low impedance signal amplifying circuit for the high impedance system further comprises an MCU control circuit, the MCU control circuit comprises an MCU chip U4, wherein:
the No. 7 end of the MCU chip U4 is connected with the No. 1 end of the AD conversion chip U5 through a resistor R15;
the No. 5 end of the MCU chip U4 is connected to the No. 5 end of the AD conversion chip U5 through a resistor R20.
Further, the terminal No. 7 of the AD conversion chip U5 is connected to the Pi-type voltage controlled attenuation chip D1 having 4 diodes through an inductor L4.
Furthermore, a common end between the terminal 7 of the AD conversion chip U5 and the inductor L4 is sequentially connected to one end of a capacitor C26, one end of a capacitor C33, and one end of a polar capacitor C25, and the other end of the capacitor C26, the other end of the capacitor C33, and the other end of the polar capacitor C25 are respectively grounded.
A resistor R14, two reversely connected diodes D2 and a resistor R21 are sequentially connected between the No. 2 end and the No. 3 end of the MCU chip U4.
The No. 4 end of the MCU chip U4 is connected to a 5V power supply through a resistor R18.
The common terminal between the No. 5 terminal of the MCU chip U4 and the resistor R20 is grounded through a resistor R19.
Further, the low impedance signal amplifying circuit for the high impedance system further comprises a power circuit, the power circuit comprises a polarity capacitor C30, a capacitor C31, a capacitor C32 and a varactor D10 which are connected in parallel, and a common terminal between the varactor C32 and the varactor D10 is further grounded through a photodiode D4 and a resistor R22.
It is worth mentioning that the resistance value of the first impedance chip U1 is preferably 50 ohms.
It is worth mentioning that the resistance value of the second impedance chip U3 is preferably 50 ohms.
It is worth mentioning that the above-mentioned high impedance system is preferably embodied as a cable television system.
It is worth mentioning that the impedance of the cable television system is preferably 75 ohms.
A first embodiment.
Preferably, the low impedance signal amplifying method for a high impedance system is used for matching a high impedance system, and comprises the following steps: the converted electrical signal is output by the optical fiber detector U2, converted into a 50 ohm impedance signal by the first impedance converter B1, amplified by the first impedance chip U1(50 ohm), automatically controlled by the AGC automatic control circuit to output level, amplified by the second impedance chip U3(50 ohm), and converted into a 75 ohm impedance signal by the second impedance converter B2, so that the high impedance system (e.g., cable television system) with 75 ohm impedance is suitable for the high impedance system (e.g., cable television system) with 75 ohm impedance.
Further, a first branch of the output end of the fiber optic probe U2 is connected to the first end of the first impedance transformer B1 through an inductor L1;
the third end of the first impedance converter B1 is connected to the No. 1 end of the first impedance chip U1 through a capacitor C4;
the AGC automatic control circuit comprises a Pi-type voltage-controlled attenuation chip D1 with 4 diodes, wherein the No. 3 end of the first impedance chip U1 is connected to the input end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes through a capacitor C37, a resistor R11 and a capacitor C38 in sequence;
the output end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes is connected to the No. 1 end of the second impedance chip U3 through a capacitor C13, a resistor R37 and a capacitor C14;
the terminal 3 of the second impedance chip U3 is connected to the first terminal of the second impedance transformer B2 through a capacitor C15.
Further, the low impedance signal amplifying method for a high impedance system adopts a low impedance signal amplifying circuit for a high impedance system, and the low impedance signal amplifying circuit for a high impedance system further includes:
the signal protection circuit comprises an inductor L6, and the third end of the second impedance converter B2 is connected to one end of the inductor L6 through a capacitor C18, a capacitor C19 and a capacitor C17 in sequence;
an RF signal output circuit, the RF signal output circuit includes an RF port F1, the other end of the inductor L6 is connected to the No. 1 terminal of the RF port F1 through a capacitor C22, and the RF port F1 is further connected to the high impedance system.
Further, the low impedance signal amplifying circuit for the high impedance system further comprises an AD collecting and amplifying circuit, the AD collecting and amplifying circuit comprises an AD conversion chip U5, and a second branch of the output end of the optical fiber detector U2 is connected to the terminal 3 of the AD conversion chip U5 through an inductor L3 and a resistor R6.
One end of a capacitor C6 and one end of a resistor R5 which are connected in parallel are connected between the common end of the inductor L3 and the resistor R6, one end of a capacitor C10 is connected between the common end of the resistor R6 and the No. 3 end of the AD conversion chip U5, and the other end of the capacitor C6, the other end of the resistor R5 and the other end of the capacitor C10 are grounded in common.
Further, the second terminal of the first impedance converter B1 is connected to a 5V power supply through a resistor R1.
The common terminal between the resistor R1 and the 5V power supply is connected into one terminal of a capacitor C1 and one terminal of a capacitor C2 which are connected in parallel, and the other terminal of the capacitor C1 and the other terminal of the capacitor C2 are connected to the ground in common.
Further, the common terminal between the terminal 3 of the first impedance chip U1 and the capacitor C37 is connected to a 5V power supply through an inductor L2 and a resistor R9.
Two ends of the resistor R9 are respectively connected to one end of a capacitor C9 and one end of a capacitor C11 which are connected in parallel, and the other end of the capacitor C9 and the other end of the capacitor C11 are commonly grounded.
Furthermore, a capacitor C12 is connected in parallel to two ends of the resistor R11.
Further, the Pi-type voltage-controlled attenuation chip D1 with 4 diodes preferably adopts HSMP 3816.
Further, a first branch of a common terminal between the resistor R37 and the capacitor C14 is grounded through a resistor RZ1, a capacitor CZ1 and an inductor LC1, and a second branch of the common terminal between the resistor R37 and the capacitor C14 is grounded through a capacitor C14.
Further, the common terminal between the terminal 3 of the second impedance chip U3 and the capacitor C15 is connected to a 5V power supply through an inductor L5 and a resistor R13.
Two ends of the resistor R13 are respectively connected to one end of a capacitor C24 and one end of a capacitor C23 which are connected in parallel, and the other end of the capacitor C24 and the other end of the capacitor C23 are commonly grounded.
Further, the common terminal between the capacitor C19 and the capacitor C17 is grounded through an inductor L8.
Further, the common terminal between the capacitor C17 and the inductor L6 is grounded through a resistor R12.
Further, the common terminal between the inductor L6 and the capacitor C22 is grounded through two switching diodes D7 and D9, which are cascaded with each other.
Further, the common terminal between the capacitor C22 and the terminal No. 1 of the RF port F1 is grounded through a ceramic gas discharge tube D8.
Further, the low impedance signal amplifying circuit for the high impedance system further comprises an MCU control circuit, the MCU control circuit comprises an MCU chip U4, wherein:
the No. 7 end of the MCU chip U4 is connected with the No. 1 end of the AD conversion chip U5 through a resistor R15;
the No. 5 end of the MCU chip U4 is connected to the No. 5 end of the AD conversion chip U5 through a resistor R20.
Further, the terminal No. 7 of the AD conversion chip U5 is connected to the Pi-type voltage controlled attenuation chip D1 having 4 diodes through an inductor L4.
Furthermore, a common end between the terminal 7 of the AD conversion chip U5 and the inductor L4 is sequentially connected to one end of a capacitor C26, one end of a capacitor C33, and one end of a polar capacitor C25, and the other end of the capacitor C26, the other end of the capacitor C33, and the other end of the polar capacitor C25 are respectively grounded.
A resistor R14, two reversely connected diodes D2 and a resistor R21 are sequentially connected between the No. 2 end and the No. 3 end of the MCU chip U4.
The No. 4 end of the MCU chip U4 is connected to a 5V power supply through a resistor R18.
The common terminal between the No. 5 terminal of the MCU chip U4 and the resistor R20 is grounded through a resistor R19.
Further, the low impedance signal amplifying circuit for the high impedance system further comprises a power circuit, the power circuit comprises a polarity capacitor C30, a capacitor C31, a capacitor C32 and a varactor D10 which are connected in parallel, and a common terminal between the varactor C32 and the varactor D10 is further grounded through a photodiode D4 and a resistor R22.
It is worth mentioning that the resistance value of the first impedance chip U1 is preferably 50 ohms.
It is worth mentioning that the resistance value of the second impedance chip U3 is preferably 50 ohms.
It is worth mentioning that the above-mentioned high impedance system is preferably embodied as a cable television system.
It is worth mentioning that the impedance of the cable television system is preferably 75 ohms.
It should be noted that the technical features such as specific selection of the ceramic gas discharge tube D8 and the like according to the present invention should be regarded as the prior art, and the specific structure, the operation principle, the control method and the spatial arrangement method of the technical features may be selected conventionally in the field, and should not be regarded as the invention point of the present invention, and the present invention is not further specifically described in detail.
It will be apparent to those skilled in the art that modifications and equivalents may be made in the embodiments and/or portions thereof without departing from the spirit and scope of the present invention.
Claims (10)
1. A low impedance signal amplification method for high impedance systems for matching a high impedance system, comprising the steps of: the converted electric signal is output by the optical fiber detector U2, converted into a 50-ohm impedance signal by the first impedance converter B1, amplified by the first impedance chip U1, automatically controlled by the AGC automatic control circuit to output level, amplified by the second impedance chip U3, and converted into a 75-ohm impedance signal by the second impedance converter B2, so that the high-impedance optical fiber detector is suitable for a 75-ohm impedance high-impedance system.
2. The low impedance signal amplification method of claim 1, wherein the first branch of the output terminal of the fiber optic probe U2 is connected to the first terminal of the first impedance transformer B1 through an inductor L1;
the third end of the first impedance converter B1 is connected to the No. 1 end of the first impedance chip U1 through a capacitor C4;
the AGC automatic control circuit comprises a Pi-type voltage-controlled attenuation chip D1 with 4 diodes, wherein the No. 3 end of the first impedance chip U1 is connected to the input end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes through a capacitor C37, a resistor R11 and a capacitor C38 in sequence;
the output end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes is connected to the No. 1 end of the second impedance chip U3 through a capacitor C13, a resistor R37 and a capacitor C14;
the terminal 3 of the second impedance chip U3 is connected to the first terminal of the second impedance transformer B2 through a capacitor C15.
3. A low impedance signal amplification circuit for use in high impedance systems for matching a high impedance system, said low impedance signal amplification circuit for use in high impedance systems comprising:
a fiber detector U2 and a first impedance converter B1, wherein a first branch of the output end of the fiber detector U2 is connected to a first end of the first impedance converter B1 through an inductor L1;
a first impedance chip U1, wherein the third terminal of the first impedance transformer B1 is connected to the No. 1 terminal of the first impedance chip U1 through a capacitor C4;
an automatic AGC control circuit, which comprises a Pi-type voltage-controlled attenuation chip D1 with 4 diodes, wherein the No. 3 end of the first impedance chip U1 is connected to the input end of the Pi-type voltage-controlled attenuation chip D1 with 4 diodes through a capacitor C37, a resistor R11 and a capacitor C38 in sequence;
the output end of the Pi type voltage-controlled attenuation chip D1 with 4 diodes is connected to the No. 1 end of the second impedance chip U3 through a capacitor C13, a resistor R37 and a capacitor C14;
the No. 3 end of the second impedance chip U3 is connected to the first end of the second impedance converter B2 through a capacitor C15;
the signal protection circuit comprises an inductor L6, and the third end of the second impedance converter B2 is connected to one end of the inductor L6 through a capacitor C18, a capacitor C19 and a capacitor C17 in sequence;
an RF signal output circuit, the RF signal output circuit includes an RF port F1, the other end of the inductor L6 is connected to the No. 1 terminal of the RF port F1 through a capacitor C22, and the RF port F1 is further connected to the high impedance system.
4. The low impedance signal amplifying circuit for high impedance system as claimed in claim 3, wherein the low impedance signal amplifying circuit for high impedance system further comprises an AD collecting and amplifying circuit, the AD collecting and amplifying circuit comprises an AD converting chip U5, the second branch of the output terminal of the fiber probe U2 is connected to the No. 3 terminal of the AD converting chip U5 through an inductor L3 and a resistor R6.
5. The low impedance signal amplifying circuit for high impedance system as claimed in claim 4, wherein one end of a capacitor C6 and one end of a resistor R5 connected in parallel to each other are connected between the inductor L3 and the common terminal of the resistor R6, one end of a capacitor C10 is connected between the resistor R6 and the common terminal of the AD conversion chip U5, and the other end of the capacitor C6, the other end of the resistor R5 and the other end of the capacitor C10 are connected to ground in common.
6. The low impedance signal amplifying circuit for high impedance system of claim 4, wherein said low impedance signal amplifying circuit for high impedance system further comprises an MCU control circuit, said MCU control circuit comprising an MCU chip U4, wherein:
the No. 7 end of the MCU chip U4 is connected with the No. 1 end of the AD conversion chip U5 through a resistor R15;
the No. 5 end of the MCU chip U4 is connected to the No. 5 end of the AD conversion chip U5 through a resistor R20.
7. A low impedance signal amplifying circuit for high impedance system as claimed in any one of claims 3 to 6 wherein said first impedance chip U1 has a resistance of 50 ohms.
8. A low impedance signal amplifying circuit for high impedance system as claimed in any one of claims 3 to 6 wherein said second impedance chip U3 has a resistance of 50 ohms.
9. A low impedance signal amplification circuit for a high impedance system as claimed in any one of claims 3 to 6, wherein said high impedance system is embodied as a cable television system.
10. The low impedance signal amplification circuit of claim 9, wherein said cable television system has an impedance of 75 ohms.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010563648.5A CN111641394A (en) | 2020-06-19 | 2020-06-19 | Low-impedance signal amplifying circuit for high-impedance system and amplifying method thereof |
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| CN202010563648.5A CN111641394A (en) | 2020-06-19 | 2020-06-19 | Low-impedance signal amplifying circuit for high-impedance system and amplifying method thereof |
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