CN220874595U - Transmitter output power limiting circuit - Google Patents
Transmitter output power limiting circuit Download PDFInfo
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- CN220874595U CN220874595U CN202322628902.7U CN202322628902U CN220874595U CN 220874595 U CN220874595 U CN 220874595U CN 202322628902 U CN202322628902 U CN 202322628902U CN 220874595 U CN220874595 U CN 220874595U
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- 238000012544 monitoring process Methods 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
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Abstract
The utility model provides a transmitter output power limiting circuit, which comprises an exciter output power sampling circuit, a transmitter whole machine output power sampling circuit, a comparison amplifying circuit and a radio frequency signal attenuation circuit, wherein the exciter output power sampling circuit is used for collecting an exciter output power sampling voltage; the transmitter complete machine output power sampling circuit is used for collecting the transmitter complete machine output power sampling voltage; the comparison amplifying circuit is used for comparing the output power sampling voltage of the exciter with the output power sampling voltage of the whole transmitter and determining whether the output power of the radio frequency signal of the transmitter is limited or not; and the radio frequency signal attenuation circuit is used for limiting the output power of the radio frequency signal of the transmitter. The scheme provided by the utility model overcomes the defect of small control range of the negative feedback circuit in the transmitter, can reduce the output power when the negative feedback circuit in the transmitter cannot correct the abnormally-increased output power, avoids damaging the transmitter, and has stable and reliable circuit.
Description
Technical Field
The utility model relates to the technical field of television transmitters, in particular to a transmitter output power limiting circuit.
Background
In the operation process of the television transmitter, the television transmitter is inevitably influenced by the aging of components or external factors, so that the output power is changed. The transmitter itself is designed with an automatic gain control circuit, the control mode is based on an internal negative feedback circuit, but the disadvantage is that the control range is small.
The original method for improving the power of the internal negative feedback circuit is as follows: at the moment of starting up, the environment temperature is lower, the temperature of components of the transmitter is also low, the amplification factors of all stages of amplifying circuits are high, the output power is high, the transmitter works for a period of time, the temperatures of an exciter and an amplifying module of the whole transmitter start to rise, the amplification factors of all amplifying circuits in the transmitter gradually decrease, the output power is also slowly reduced, and a negative feedback circuit is started to re-boost the lost power.
The original method for reducing the power of the internal negative feedback circuit is as follows: because the matching circuit is unbalanced or the attenuator of a certain part in the transmitter is abnormal, the amplification factor of a certain stage of amplifying circuit is suddenly increased, the output power is abnormally increased, the output power of another module which is in parallel operation with the amplifying circuit is not matched, the load resistor of the synthesizer absorbs excessive loss to generate heat, and the negative feedback circuit is started to reduce the increased power, so that the transmitter can safely operate.
The original power lifting method looks perfect, but in actual work, the abnormal low or high output power of the transmitter often occurs, the negative feedback circuit cannot correct the output power, and if the output power is too low, the transmitter is not damaged, but bad broadcasting accidents are caused; if the output power is too high, related components are damaged directly, and then a transmitter is damaged, so that serious equipment accidents are caused.
Disclosure of utility model
In order to solve the above problems, the present utility model provides a transmitter output power limiting circuit, which includes an exciter output power sampling circuit, a transmitter overall output power sampling circuit, a comparison amplifying circuit and a radio frequency signal attenuation circuit;
The exciter output power sampling circuit is provided with a voltage comparison amplifier U1, the exciter output power is sent to the input end of the exciter output power sampling circuit through a directional coupler, a capacitor C1 is coupled to a rear detection diode CR1, a resistor R1 plays a role in matching with a preceding stage, after being filtered by the capacitor C2 and the capacitor C3, the exciter output power is sent to an impedance matching circuit formed by the resistors R2, R3 and R4, and then the exciter output power is sent to the non-inverting input end of the voltage comparison amplifier U1 for buffer amplification, and the output voltage of the voltage comparison amplifier U1 is regulated by a potentiometer R7 and then is output to the comparison amplification circuit;
The transmitter whole output power sampling circuit is provided with a voltage comparison amplifier U2, the transmitter output power is sent to the input end of the transmitter whole output power sampling circuit through a directional coupler on an output feed pipe of a final synthesizer, a capacitor C4 is coupled to a rear detection diode CR2, a resistor R11 plays a role in matching with a preceding stage, after being filtered by the capacitor C5 and the capacitor C6, the transmitter output power is sent to an impedance matching circuit consisting of the resistors R12, R13 and R14, and then the transmitter output power is sent to the non-inverting input end of the voltage comparison amplifier U2 for buffer amplification, and the output voltage of the voltage comparison amplifier U2 is regulated by a potentiometer R17 and then is output to the comparison amplification circuit;
The comparison amplifying circuit is provided with two voltage comparison amplifiers U3 and U4, the output power sampling voltage of the exciter is transmitted to the inverting input end of the voltage comparison amplifier U3, the output power sampling voltage of the whole transmitter is transmitted to the non-inverting input end of the comparison amplifier U3, the output end of the buffer amplification is output from the output end of the voltage comparison amplifier U3, the output end of the voltage comparison amplifier U3 is connected with a resistor R21, the other end of the resistor R21 is connected with a switch S1, one end of the resistor R22 and one end of the resistor R23 are connected with a-12V power supply, the other end of the resistor R21 is connected with a switch S1, when the switch S1 is connected to the end of the resistor R21, the light emitting diode DS1 is turned on, when the S1 is connected to the end of the R22, the light emitting diode DS1 is turned off, the other side of the switch S1 is connected with the voltage comparison amplifier U4, and the voltage comparison amplifier U4 outputs the voltage to the radio frequency signal attenuation circuit;
The radio frequency signal attenuation circuit comprises two parallel thermistors, a Darlington composite tube Q1, a 3dB phase shift mixer U5, diodes CR3, CR4, CR5, CR6, resistors R34, R35, R36, R37 and diode networks formed by inductors L1 and L2, wherein the two parallel thermistors are connected with the resistor R31 in parallel, the output voltage from the comparison amplifying circuit is connected into the base electrode of the Darlington composite tube Q1 through the resistor R31, the emitter electrode of the Darlington composite tube Q1 is connected with the diode networks, the two output ends of the diode networks are connected with a first port and a second port of the 3dB phase shift mixer U5, the third port of the 3dB phase shift mixer U5 receives the whole transmitter output signal, and the fourth port outputs the adjusted transmitter output signal.
Compared with the prior art, the utility model has the following beneficial effects:
1. The defect that the control range of the negative feedback circuit in the transmitter is small is overcome, when the negative feedback circuit in the transmitter cannot correct the abnormally-increased output power, the output power is reduced through the transmitter output power limiting circuit, the transmitter is prevented from being damaged, the circuit is stable and reliable, and the using effect is very good;
2. The application range is wide, and the transmitter station or the rebroadcast station in the field of broadcast television can be used on a television transmitter, and a frequency modulation transmitter can be used after the sampling parameters are changed;
3. The circuit has simple structure, the integrated circuit and the Darlington tube are convenient for configuring peripheral components, and the circuit has simple debugging and stable operation.
It should be understood that the description of the utility model above is not intended to limit key or critical features of embodiments of the utility model, nor to limit the scope of the utility model. Other features of the present utility model will become apparent from the description that follows.
Drawings
In order to more clearly illustrate the embodiments of the present utility model or the technical solutions of the prior art, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it will be obvious that the drawings in the following description are some embodiments of the present utility model, and that other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art.
FIG. 1 is a block diagram of an exciter output power sampling circuit;
FIG. 2 is a diagram of a transmitter overall output power sampling circuit;
FIG. 3 is a diagram of a comparison amplifying circuit;
fig. 4 is a block diagram of a radio frequency signal attenuation circuit.
Detailed Description
Embodiments of the present utility model will be described in more detail below with reference to the accompanying drawings. While the utility model is susceptible of embodiment in the drawings, it is to be understood that the utility model may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather are provided to provide a more thorough and complete understanding of the utility model. It should be understood that the drawings and embodiments of the utility model are for illustration purposes only and are not intended to limit the scope of the present utility model.
The technical scheme of the utility model is described in detail below by specific examples. The following embodiments may be combined with each other, and some embodiments may not be repeated for the same or similar concepts or processes.
The embodiment of the disclosure provides a transmitter output power limiting circuit, which comprises an exciter output power sampling circuit, a transmitter whole machine output power sampling circuit, a comparison amplifying circuit and a radio frequency signal attenuation circuit;
As shown in fig. 1, the output power sampling circuit of the exciter is provided with a voltage comparison amplifier U1, the output power of the exciter is sent to a point a through a directional coupler, the output power is coupled to a rear detection diode CR1 through a capacitor C1, the rear end of the detection diode CR1 is provided with a measuring point TP1, a resistor R1 plays a role in matching with a previous stage, after filtering through capacitors C2 and C3, a high-frequency signal detected and output by the detection diode CR1 is shorted to ground, so that an output signal only remains an envelope signal voltage greater than 0.7V, the envelope signal voltage is sent to a non-inverting input end of the voltage comparison amplifier U1 for buffer amplification after passing through an impedance matching circuit consisting of resistors R2, R3 and R4, a potentiometer R7 adjusts the sampling voltage of the exciter, the voltage is sent to the comparison amplifying circuit from a point B, and a measuring point TP2 is arranged in front of the point B for monitoring the sampling voltage value of the exciter;
As shown in fig. 2, the output power sampling circuit of the whole transmitter is provided with a voltage comparison amplifier U2, the output power of the transmitter is sent to a point C through a directional coupler on an output feed tube of a final synthesizer, the output power is coupled to a rear detection diode CR2 through a capacitor C4, a measuring point TP3 is arranged at the rear end of the detection diode CR2, a resistor R11 plays a role in matching with a previous stage, after filtering through the capacitors C5 and C6, a high-frequency signal detected and output by the detection diode CR2 is shorted to the ground, so that an output signal only remains an envelope signal voltage greater than 0.7V, the envelope signal voltage is sent to an in-phase input end of the voltage comparison amplifier U2 for buffer amplification after passing through an impedance matching circuit consisting of resistors R12, R13 and R14, a potentiometer R17 adjusts the sampling voltage of an exciter and is sent to the comparison amplifying circuit from a point D, and a measuring point TP4 is arranged in front of the point D for monitoring the sampling voltage value of the transmitter;
As shown in fig. 3, the comparison amplifying circuit is provided with two voltage comparison amplifiers U3 and U4, the exciter output power sampling voltage is transmitted to the inverting input end of the voltage comparison amplifier U3, the transmitter whole machine output power sampling voltage is transmitted to the non-inverting input end of the comparison amplifier U3, the buffer amplified output is output from the output end of the voltage comparison amplifier U3, the output end of the voltage comparison amplifier U3 is connected with a resistor R21, the other end of the resistor R21 is connected with a switch S1, one end of the resistor R22 and one end of the resistor R23 are connected with a-12V power supply, the other end of the resistor R23 is connected with a switch S1, when the switch S1 is connected to the end of the resistor R21, the light emitting diode DS1 is lighted to indicate that the output power limiting circuit starts working, the output voltage of the voltage comparison amplifier U3 can be transmitted to the next stage, when the switch S1 is connected to the end of the resistor R22, the light emitting diode DS1 is extinguished to indicate that the output power limiting circuit stops working, the resistors R22 and R23 obtain the direct current voltage division voltage from-12V are transmitted to the circuit, the next stage buffer amplifier is blocked, meanwhile, a point TP5 is set to measure whether the radio frequency attenuation of the signal of the exciter output power sampling voltage and the transmitter output power sampling voltage is attenuated from the output voltage of the voltage U4 is controlled by the voltage of the comparison amplifier U4;
As shown in FIG. 4, the radio frequency signal attenuation circuit comprises two thermistors connected in parallel, a Darlington composite tube Q1, a 3dB phase shift mixer U5, and a diode network composed of diodes CR3, CR4, CR5, CR6, resistors R34, R35, R36, R37 and inductors L1 and L2, wherein the two thermistors are used for measuring the temperature of a power synthesizer component of a transmitter, when the power amplifying module of the transmitter fails, part of the output power of the module is abnormally increased or a plurality of amplifier modules are closed, the synthesizer isolation absorbing resistor absorbs dissipation power to cause the isolation absorbing resistor module to generate heat, therefore, the two thermistors are designed, when the output power is abnormally increased, the output power is reduced to ensure the safety of the transmitter, the two parallel thermistors are arranged to prevent one from being abnormal, the other can still monitor the change of the temperature, the two thermistors are resistors with negative temperature coefficients, the resistance value is reduced along with the temperature rise, the two thermistors connected in parallel are connected with the resistor R31 in parallel, the output voltage from the comparison amplifying circuit is connected into the base electrode of the Darlington composite tube Q1 through the resistor R31, the emitter electrode of the Darlington composite tube Q1 is connected with a diode network, the two output ends of the diode network are connected with a first port and a second port of the 3dB phase shift mixer U5, the third port of the 3dB phase shift mixer U5 receives the output signal of the whole transmitter, the fourth port outputs the regulated output signal of the transmitter, when the temperature rises, the resistance value of the thermistors is reduced, the total resistance value connected with the resistor R31 in parallel is reduced, the base potential of the Darlington composite tube Q1 is increased, the resistance value between the base electrode and the emitter electrode is reduced, the bias voltage of the diode network is increased, the attenuation of the 3dB phase shift mixer U5 is increased, the output power decreases.
Adjusting the output power sampling level of the exciter and the transmitter: firstly, S1 is connected to a resistor R22 end, a radio frequency signal attenuation circuit is closed, the output power of an exciter is slowly increased through a button of a front panel of the exciter, the rated power reaches 10KW on a display panel of the whole output power of the transmitter, at the moment, the measured detection voltage is about 1V on a test point TP1 of an output power sampling circuit of the exciter, and the measured detection voltage is about 1V on a test point TP3 of the output power sampling circuit of the transmitter; then the switch S1 is connected to the resistor R21 end, the control voltage of the output end of the voltage comparison amplifier U3 is connected to the next stage buffer amplifying circuit to control, the exciter output power sampling voltage adjusting potentiometer R7 and the transmitter whole machine output power sampling adjusting potentiometer R17 are debugged repeatedly, the voltage of the test point TP5 of the comparison amplifying circuit is measured to be about-1V, the output power is increased to 12KW, at the moment, the output end of the voltage comparison amplifier U4 outputs a high level, the base potential of the Darlington composite tube Q1 is increased, the resistance between the base and the emitter is reduced, the bias voltage of the diode network is increased, the attenuation of the 3dB phase shift mixer U5 is increased, the output power is reduced, the power distributed to the power amplifier is reduced, the total power after synthesis is reduced, the whole machine output power is effectively limited, and the safe operation of the transmitter is ensured.
The exemplary implementation of the transmitter output power limiting circuit according to the present utility model has been described in detail hereinabove with reference to preferred embodiments, however, it will be understood by those skilled in the art that various modifications and adaptations may be made to the specific embodiments described above and that various combinations of the technical features and structures of the present utility model may be made without departing from the scope of the utility model, which is defined in the appended claims.
Claims (1)
1. The transmitter output power limiting circuit is characterized by comprising an exciter output power sampling circuit, a transmitter whole machine output power sampling circuit, a comparison amplifying circuit and a radio frequency signal attenuation circuit;
The exciter output power sampling circuit is provided with a voltage comparison amplifier U1, the exciter output power is sent to the input end of the exciter output power sampling circuit through a directional coupler, a capacitor C1 is coupled to a rear detection diode CR1, a resistor R1 plays a role in matching with a preceding stage, after being filtered by the capacitor C2 and the capacitor C3, the exciter output power is sent to an impedance matching circuit formed by the resistors R2, R3 and R4, and then the exciter output power is sent to the non-inverting input end of the voltage comparison amplifier U1 for buffer amplification, and the output voltage of the voltage comparison amplifier U1 is regulated by a potentiometer R7 and then is output to the comparison amplification circuit;
The transmitter whole output power sampling circuit is provided with a voltage comparison amplifier U2, the transmitter output power is sent to the input end of the transmitter whole output power sampling circuit through a directional coupler on an output feed pipe of a final synthesizer, a capacitor C4 is coupled to a rear detection diode CR2, a resistor R11 plays a role in matching with a preceding stage, after being filtered by the capacitor C5 and the capacitor C6, the transmitter output power is sent to an impedance matching circuit consisting of the resistors R12, R13 and R14, and then the transmitter output power is sent to the non-inverting input end of the voltage comparison amplifier U2 for buffer amplification, and the output voltage of the voltage comparison amplifier U2 is regulated by a potentiometer R17 and then is output to the comparison amplification circuit;
The comparison amplifying circuit is provided with two voltage comparison amplifiers U3 and U4, the output power sampling voltage of the exciter is transmitted to the inverting input end of the voltage comparison amplifier U3, the output power sampling voltage of the whole transmitter is transmitted to the non-inverting input end of the comparison amplifier U3, the output end of the buffer amplification is output from the output end of the voltage comparison amplifier U3, the output end of the voltage comparison amplifier U3 is connected with a resistor R21, the other end of the resistor R21 is connected with a switch S1, one end of the resistor R22 and one end of the resistor R23 are connected with a-12V power supply, the other end of the resistor R21 is connected with a switch S1, when the switch S1 is connected to the end of the resistor R21, the light emitting diode DS1 is turned on, when the S1 is connected to the end of the R22, the light emitting diode DS1 is turned off, the other side of the switch S1 is connected with the voltage comparison amplifier U4, and the voltage comparison amplifier U4 outputs the voltage to the radio frequency signal attenuation circuit;
The radio frequency signal attenuation circuit comprises two parallel thermistors, a Darlington composite tube Q1, a 3dB phase shift mixer U5, diodes CR3, CR4, CR5, CR6, resistors R34, R35, R36, R37 and diode networks formed by inductors L1 and L2, wherein the two parallel thermistors are connected with the resistor R31 in parallel, the output voltage from the comparison amplifying circuit is connected into the base electrode of the Darlington composite tube Q1 through the resistor R31, the emitter electrode of the Darlington composite tube Q1 is connected with the diode networks, the two output ends of the diode networks are connected with a first port and a second port of the 3dB phase shift mixer U5, the third port of the 3dB phase shift mixer U5 receives the whole transmitter output signal, and the fourth port outputs the adjusted transmitter output signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202322628902.7U CN220874595U (en) | 2023-09-27 | 2023-09-27 | Transmitter output power limiting circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202322628902.7U CN220874595U (en) | 2023-09-27 | 2023-09-27 | Transmitter output power limiting circuit |
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| Publication Number | Publication Date |
|---|---|
| CN220874595U true CN220874595U (en) | 2024-04-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202322628902.7U Active CN220874595U (en) | 2023-09-27 | 2023-09-27 | Transmitter output power limiting circuit |
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| CN (1) | CN220874595U (en) |
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2023
- 2023-09-27 CN CN202322628902.7U patent/CN220874595U/en active Active
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