CN100420284C - A power booster system for digital TV co-frequency forwarding - Google Patents

Abstract

The invention relates to a power booster system for co-frequency forwarding of digital TV, comprising a donor antenna, a tower top amplifier, a power booster host and a retransmission antenna, the donor antenna is connected to the input end of the tower top amplifier; the power booster host It is composed of the first channel filter, the second channel filter, low noise amplifier, intermediate frequency processing, power amplification unit, CPU control unit and power supply, the first channel filter, low noise amplifier, intermediate frequency processing, power amplification unit and the second The two channel filters are connected sequentially, the tower top amplifier is connected with the input end of the first channel filter, and the output end of the second channel filter is connected with the retransmission antenna. The invention has the advantages that: the signal can be forwarded in the same frequency, and it is suitable for different frequency bands and different output powers of the digital TV same-frequency forwarding power booster. Good performance, can guarantee the quality of the digital TV signal and the signal coverage of the blind area, so that the digital TV signal can continue to extend forward.

Description

A power booster system for digital TV co-frequency forwarding

technical field

The invention relates to digital TV transmitting equipment, in particular to a power booster system for digital TV same-frequency forwarding.

Background technique

Under the situation that digital TV is increasingly popularized, in some shopping malls, underground parking lots, tunnels, high-rise buildings, elevators, entertainment venues, and suburban and remote areas, it will be unimaginable without the coverage of digital TV signals. Combined with the characteristics of digital TV transmitters, it is impossible to set up a transmitting station in every area with poor digital TV signal coverage or signal blind area. Therefore, digital TV co-frequency forwarding power booster system devices are usually set up in these areas. This system device It solved these problems very well. The power booster uses a directional antenna to introduce digital TV signals, filters and amplifies the digital TV signals, but does not perform any frequency conversion, and then transmits them to the shadow area with a directional antenna. However, due to the limited isolation of the input and output antennas, in order to avoid self-excitation of the amplifier, the amplification power should not be too large. The power booster can also be used to improve indoor reception. Due to the attenuation of electromagnetic waves by buildings, the indoor signal strength is much lower than the outdoor signal strength. The main parameters of the power booster are gain, sensitivity, output power, intermodulation and linear.

Contents of the invention

The present invention aims to solve the above-mentioned defects of the prior art, and provides a power booster system for digital TV co-frequency forwarding. The system can effectively solve the problem of digital TV signal quality in the area that the digital TV transmitter cannot cover.

The present invention solves the technical scheme that its technical problem adopts. This kind of power booster system for digital TV co-frequency forwarding mainly includes donor antenna, tower top amplifier, power booster host and retransmission antenna, in which the donor antenna mainly receives the digital TV signal from the main transmitting station through the coaxial The cable is connected to the input terminal of the tower top amplifier; the main unit of the power booster is composed of the first channel filter, the second channel filter, low noise amplifier, intermediate frequency processing, power amplification unit, CPU control unit and power supply, of which the first The channel filter, low noise amplifier, intermediate frequency processing, power amplifying unit and the second channel filter are connected in sequence, the output of the tower top amplifier is connected with the input of the first channel filter, and the output of the second channel filter It is connected with the retransmission antenna through the coaxial cable; the CPU control unit is respectively connected with the low noise amplifier, the intermediate frequency processing unit and the power amplification unit. After the digital TV signal received by the donor antenna passes through the tower top amplifier, it first enters the first channel filter in the main unit of the power booster for filtering, then sends it to the low noise amplifier, and then sends the output to the power amplifier unit after intermediate frequency processing to achieve The required power is transmitted through the second channel filter through the coaxial cable and directly to the retransmission antenna.

The power booster system used for digital TV same-frequency forwarding related to the present invention has remarkable features in the field: 1. In principle, a new circuit structure is realized, so that signals are forwarded at the same frequency, and it is suitable for digital TV same-frequency forwarding Different frequency bands, different output power of the power booster. The use performance is good, which can ensure the quality of digital TV signals and the signal coverage of blind areas, so that digital TV signals continue to extend forward; 2. In terms of performance, it is truly unattended, and the various tasks of the device can be controlled through the remote wireless control system Parameters and working modes can be adjusted; precise GPS can directly locate the device, which can effectively improve the synchronization of the entire launch system; 3. An easier-to-install structure is used in the project, making installation more convenient, and the installation time is within 2 hours ; 4. Because it is suitable for outdoor installation, it can be used in a wider range of occasions. To sum up, the use of this digital TV same-frequency forwarding GAP FILLER device has epoch-making significance, and has more use value.

Description of drawings

Fig. 1 is a schematic block diagram of the principle of the present invention;

Fig. 2 is a structural representation of the present invention;

Fig. 3 is the circuit diagram of low noise amplifier part in the present invention;

Fig. 4 is the circuit diagram of power amplifier part among the present invention;

Fig. 5 is the circuit diagram of tower top amplifier part among the present invention;

Fig. 6 is the structural representation of channel filter part in the present invention;

Fig. 7 is a circuit diagram of the CPU control unit part in the present invention.

Description of reference signs: 1-donor antenna, 2-tower amplifier, 3-power booster host, 4-retransmission antenna, 5-first channel filter, 6-second channel filter, 7-low noise amplifier , 8-IF processing, 9-power amplifier unit, 10-CPU control unit, 11-power supply, 12-input and output connector, 13-two-color indicator light, 14-power connector, 15-input connector, 16-output Connector, 17-input-output coupling line, 18-cavity, 19-metal cylinder, 20-tuning screw, 21-screw, 22-top cover.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing and embodiment:

Referring to the description of the above drawings, the present invention relates to a power booster system (see Figure 2) for co-frequency forwarding of digital TV, mainly comprising a donor antenna 1, a tower top amplifier 2, a power booster host 3 and a retransmission antenna 4 , wherein the donor antenna 1 that mainly receives the digital TV signal from the main transmitting station is connected with the input end of the tower top amplifier 2 through a coaxial cable; the power booster host 3 is composed of a first channel filter 5 and a second channel filter 6 , low noise amplifier 7, intermediate frequency processing 8, power amplifying unit 9, CPU control unit 10 and power supply 11, wherein the first channel filter 5, low noise amplifier 7, intermediate frequency processing 8, power amplifying unit 9 and the second channel Filter 6 is connected successively, and the output end of tower top amplifier 2 is connected with the input end of first channel filter 5, and the output end of second channel filter 6 is connected with retransmission antenna 4 by coaxial cable; CPU The control unit 10 is respectively connected with the low noise amplifier 7 , the intermediate frequency processing 8 and the power amplification unit 9 . The bottom side input and output end of power booster main frame 3 respectively has an input and output connector 12, and the two-color indicator light 13 that indicates that main frame working state is used, and the power supply connector 14 that power supply is useful; The first channel filter 5 and the first The channel filters 6 can be identical and the range of frequencies can be adjusted.

Donor antenna 1 receives the signal and sends it to the tower top amplifier 2. The amplified digital TV signal first enters the first channel filter 5 in the power booster host 3 for filtering, then sends it to the low noise amplifier 7, and then to the intermediate frequency processing 8 The output is sent to the power amplifier unit 9, and after reaching the required power, it passes through the second channel filter 6 through the coaxial cable and directly transmits to the retransmission antenna 4, so as to ensure that the digital TV signal covers poor areas or Signal coverage problems in signal blind areas.

The donor antenna 1 mentioned here mainly receives digital TV signals from the main transmitting station, and the requirements of the antenna are that it must have a certain directionality, the input standing wave should be small, the lightning protection performance is good, and the receiving performance is stable. The retransmission antenna 4 is used to transmit the signal from the host of the power booster. The retransmission antenna 4 has a certain directionality, a small output standing wave, and good lightning protection performance. In addition, it should have a high power level requirement. The backlobe of the antenna should be small, that is, the isolation between the retransmission antenna 4 and the donor antenna 1 should be large. Described tower top amplifier 2 is made up of an input filter and a low noise amplifier (as Fig. 1), and this low noise amplifier is made up of two 3dB directional couplers of CP0, CP1 as Q2, Q3-SPF-2086TK low noise The first stage composed of the distribution and synthesis of the amplifier tubes and the Q4-AGB3300 high-linearity and low-noise amplifier tube are jointly formed (as shown in Figure 5). In order to ensure the linearity of the Q2 and Q3 amplifier tubes, the circuits C2, C3, C33, and C34 Form a good matching circuit with L2 and L3, and the input and output impedance of Q4 are realized by inductance and capacitance at both ends; the power booster host 3 is composed of a first channel filter 5, a second channel filter 6, a low noise Composed of amplifier 7, intermediate frequency processing 8, power amplifier unit 9, CPU control unit 10 and power supply 11, the first channel filter 5 and the second channel filter 6 need to meet certain standards, and there are no suitable ones available for purchase at this stage. It needs to be designed by oneself; since there is no similar power booster 3 device at this stage, the low-noise amplifier 7 also needs to be designed and processed. Some control interface circuits are provided, such as the power switch and alarm of the tower top amplifier, the current alarm of the low noise amplifier and the functional interface circuit of signal level detection. In Figure 3, components such as 1U8 and 1Q5 form the tower-mounted amplifier switch circuit controlled by the CPU logic level, and 1U0, 1U7, 1U6 and other integrated circuits form the tower-mounted amplifier current alarm circuit, and the voltage of TP7 and TP8 is the alarm window. 1U9, 1U4 and 1U5 form the alarm circuit of the low noise amplifier, and the voltage of TP3 and TP4 is also the alarm window. The signal input level detection circuit is composed of 1U2A, 1U3, etc.; the intermediate frequency processing 8 is replaced by a cavity filter, but the parameters of the filter must meet certain requirements; as shown in Figure 6, this figure is the filter The top view of the top cover 22 is removed, the cavity 18 is made of the same piece of material, and is divided into six cavities, the leftmost and rightmost cavities are absorption cavities, and these two cavities are composed of a metal cylinder 19 and a tuning screw 20 located therein The absorption resonance unit, the metal cylinder 19 is a hollow structure, and the tuning screw 20 is inserted into it. By adjusting the length of the 20, the two cavities resonate at different frequencies respectively, which is reflected in the response curve of the filter to form a transmission zero point at the corresponding frequency point , so as to improve the square coefficient of the filter and increase the selectivity; the remaining four cavities form the main resonant unit with the metal cylinder and tuning screw located in it, which is a typical coaxial cavity comb filter structure, which produces Chebyshev filtering The adjustment of the center frequency of the filter mainly depends on adjusting the length of the tuning screw 20 protruding into the metal cylinder 19 of each main resonance unit. One end of the input-output coupling line 17 is connected to the input-output connectors 15, 16 through the hole in the cavity 18, and the other end is connected to the first section or the last section of the main resonant cylinder. The screw 21 is located between the resonant cavities, and there are 5 rods in total. By adjusting the length, the coupling coefficient between the cavities can be adjusted, thereby adjusting the overall performance of the filter. The power amplifier unit 9 must reach a certain power level and is divided into four stages of amplification. The amplifier components can be purchased, but its circuit structure needs to be designed and manufactured by itself, as shown in Fig. 4, wherein the first, second and third stages all adopt high Linear, low noise, wide gain module, both input and output impedances are 50 ohms, no need to design impedance circuits. The three-stage amplifying tubes are SGA-5486, AGB3300 and MHL9318 respectively. Certain capacitors are required for isolation between the stages, which are C38, C39, C40 and C41. LDU25 is a power amplifier module that can be purchased, using two MRF9030L Composed of power amplifier tubes, the power amplifier unit itself also has detection functions, such as output power detection, standing wave detection, power amplifier current detection, etc. The detection of output power is through the CP1 bridge coupler, and a part of the energy is coupled through the A/ After D conversion, the operational amplifier amplifies and directly enters the I ² C circuit composed of U8 and other components. The circuit principle of the standing wave detection is the same as that of the output power detection, except that the source of the standing wave detection signal is the coupling of the ISO1 isolator. The coupling amount of the isolator coupling terminal needs a certain amount; the bridge coupler and isolator need to meet certain standard specifications, otherwise they will not be available. When the output power is detected, in addition to a part of the op amp as input, a part is sent to the automatic gain control circuit composed of U14, D3, U13, R32, L10, L11, D1, D2 and CP2. The automatic gain control circuit can be in the circuit When the gain is too high or the power amplifier is self-excited, the entire gain of the amplifier is controlled to protect the power amplifier and improve the linearity of the power amplifier. The circuit composed of R21, U5, U7, and Q1 can detect and control the current of the power amplifier. Since this device is used outdoors, if there is no power control when the main transmitting station of the TV station is turned off, the device will always run. Energy saving is disadvantageous, so the power supply of the power amplifier device is controlled by the circuit. The realization of the above functions can be realized by CPU10, wherein U6, U8, U16 and the ^I2C formed by the external circuit is the window for the CPU to realize the detection and control of the power amplifier. The hardware part of the CPU control unit 10: adopt high-speed 51 single-chip microcomputer (AT89C51RD2) as the main control MCU; externally expand 32K capacity SRAM (TC55257DFL-85L), ensure that the device can be embedded in a real-time operating system, and can save a large amount of data; externally expand 64K capacity serial Line EERAM (AT24C512), specially used for system in-application upgrade (IAP); external expansion serial port expansion chip (ST16C2550CQ), can conveniently realize various communication methods; choose GPRS module G20, can use sms and gprs and other communication The real-time monitoring and alarming of the equipment can be realized by means of power supply; it has the function of main and standby power supply switching, which can realize the functions of power failure alarm; Changes such as the network require an upgrade of the system, which can be upgraded in a remote and unattended manner; the network management protocol is the Unicom network management protocol; the software design adopts a modular design, and each module has passed a separate test to ensure the stable and reliable operation of the equipment.

Claims (5)

1. A power booster system for co-frequency forwarding of digital television, characterized in that it comprises a donor antenna (1), a tower mount amplifier (2), a power booster host (3) and a retransmission antenna (4), The donor antenna (1) which mainly receives the digital TV signal from the main transmitting station is connected to the input end of the tower top amplifier (2) through a coaxial cable; the power booster host (3) is controlled by the first channel filter (5) , second channel filter (6), low noise amplifier (7), intermediate frequency processing (8), power amplification unit (9), CPU control unit (10) and power supply (11), wherein the first channel filter (5), low-noise amplifier (7), intermediate frequency processing (8), power amplifying unit (9) and the second channel filter (6) are connected successively, and the output terminal of the tower top amplifier (2) is filtered with the first channel The input end of the device (5) is connected, the output end of the second channel filter (6) is connected with the retransmission antenna (4) through the coaxial cable; the CPU control unit (10) is respectively connected with the low noise amplifier (7) , the intermediate frequency processing (8) and the power amplifying unit (9) are connected. 2. The power booster system for digital television co-frequency forwarding according to claim 1, wherein: said tower-mounted amplifier (2) is made up of an input filter and a low-noise amplifier. The digital TV signal can only be enabled when the signal strength is lower than a certain value. The low-noise amplifier includes the first stage and the AGB3300 high linearity low noise amplifier tube (Q4), one of the 3dB directional coupler (CPO) is used as the distribution of two SPF-2086TK low noise amplifier tubes (Q2, Q3), and the other 3dB directional coupler (CP1) is used as two Synthesis of SPF-2086TK low-noise amplifier tubes (Q2, Q3). 3. The power booster system for co-frequency forwarding of digital TV according to claim 1 or 2, characterized in that: the power supply of the tower mount amplifier (2) is from the power booster host (3) (11) directly supply power to it through the coaxial cable, and the CPU control unit (10) in the main unit (3) of the power booster directly controls the on-off of the power supply (11). 4. The power booster system for digital television co-frequency forwarding according to claim 1, characterized in that: the intermediate frequency processing (8) is a cavity filter, the leftmost and the most of the cavity (18) The rightmost cavity is the absorption cavity, and these two cavities together with the metal cylinder (19) and the tuning screw (20) in it constitute the absorption resonance unit, the metal cylinder (19) is a hollow structure, and the tuning screw (20) is inserted into it; the other cavities The main resonance unit is formed with the metal cylinder (19) and the tuning screw (20) located therein, and one end of an input-output coupling line (17) is connected to the input connector (15) through a hole in the cavity (18), and the other One end is connected to the first metal cylinder of the main resonance unit; one end of the other input-output coupling line (17) is connected to the output connector (16) through the hole in the cavity (18), and the other end is connected to the main resonance unit The last section of the metal cylinder is connected; the screw (21) is located between two adjacent cavities of the cavity, and is used to adjust the coupling coefficient between the cavities. 5. the power booster system that is used for digital TV co-frequency forwarding according to claim 1, is characterized in that, the bottom side input and output end of power booster main frame (3) respectively has an input and output connector (12), There is a two-color indicator light (13) for indicating the working state of the host at the bottom input end, and a power connector (14) for power supply at the bottom output end.

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