The radio frequency power amplifier protects the design and application of the controlling circuit
Summary: Have recommended the power of power amplifier of the radio frequency of communication radio station of ultrashort wave to protect function and operating principle of the controlling circuit, and provide the basic circuit.
Modern military, civil ultrashort wave communication radio station, in order to meet its communication distance far requirement, its radio frequency is large in output power, the general work of power amplifier of the radio frequency is in the heavy current, heavy-duty state, in order to make the circuit of power amplifier work safely and reliably, protect the automatic control circuit in circuit setting of power amplifier more complete power amplifier, include the high-pressure standing-wave ratio to protect, the built-in high temperature protects and the protective circuit of power of low voltage drop, make the work discharging of radio frequency of the transmitting set export the large radio frequency power under guaranteeing the safe prerequisite.
Protective circuit of specific power of standing wave of a voltage
1. A function
When the transmitter antenna breaks down, the radio frequency power that the transmitting set exports can’t get effective transmission, will produce very large transmitted power, serious shadow
Security of the loud work discharging. So, set up the protective circuit of high-pressure standing-wave ratio in the controlling circuit of the transmitting set, comparing with the time of higher than the certain valueing, control the output power of the radio frequency to lower the power amplifier circuit of valid protection in the voltage standing wave, its circuit.
1. 2 circuit theories
Fig. 1 is that the specific power of standing wave of the voltage protects the basic circuit. Its operating principle is measured the voltage of back power outputted by the directional coupler in the power amplifier Ausgang of the transmitting set, after the relevant circuit in the stabilized voltage supply of power amplifier are dealt with, send to the transmitting set controlling circuit XP1/ 12A, then measure the compensator circuit of the voltage through the back power and add the amplifier to N20B, add to the in-phase input end of N20A through N20B, when the terminal voltage of this input is up to about 300mV, (when the power amplifier is exported with the mismatching of aerial impedance, the voltage standing wave ratio is greater than 2. 5: 1),N23A output voltage greater than 6. 2V, makes VD5 regulator tube and V3 turned on. It makes VD6 turned on that V3 turns on, makes the level of N23B in-phase input end reduce in this way, the voltage of N23B Ausgang is reduced too, the direct-current control voltage of power of Vx input end so as to be added to the analog multiplier unit N24 drops to a certain level, make the output power of power amplifier of the radio frequency reduce to a certain number value finally, the radio frequency power amplifier be protected.
As the voltage standing wave ratio is not greater than 2. 5: At 1 o’clock, the back power measures the voltage minorly, the voltage that N23A outputs is not enough to make VD5 turned on, so, VD6 ends because of reversal of biasing, loses only direct-current control voltage of power that the normal front panel sets up that people’s end adds in N23B equal phase, the voltage added of analog multiplier unit Vx input end is the normal value, the normal output power of power amplifier of the transmitting set radio frequency too.
Built-in high-temperature power 2 is protected
The radio station of the double-frequeny-range has temperature sensors in work discharging and power amplifier voltage regulation module of the radio frequency, when the built-in temperature exceeds 65 , rotate with higher speed from controlling the module microcomputer controlled air blower; Exceed at 80 , control high temperature lower in the circuit of power work in the the intersection of computer and the intersection of control transmitter and controlling circuit, make the radio frequency export the decrease of power. The built-in high temperature lowers the electrical schematic diagram of the power.
Can find out from 2 Fig. built-in high temperature lower power control is Tx (transmitting set) actually Direct-current control voltage of power that the power control potentiometer RP11 of the front panel sets up, pass R168 and D10 some all the way ‘ Or how much way) The switch puts through the resistance (R175- 178) connected Carry on partial pressure deal with, make, send stepping down of voltage of end, Vx of analog multiplier unit, into, thus make the radio frequency export the decrease of power.
D10( MC14066) It is simulation electronic beam switches of No. four of a film, its control end (A, B, C) Accept that controls the machine format control of binary scale that the computer of the module outputted through the interface circuit of the TX data. If the temperature is raising constantly, the binary number increases gradually, thus make the resistance that D10 is being put through increase, the output power of the radio frequency drops gradually.
What D end controlled is built-in high-temperature indicating circuit. When D end is the high level ‘ Built-in high temperature) ,V5 is open, make VD9 luminescent diode point out the high temperature.
Power of 3 low voltage drop
In the controlling circuit of the transmitting set, there is mains voltage that monitors the circuit (on dealing with the circuit diagram in the audio frequency) ,Once detect the stepping down of voltage of power, enable the stepping down of voltage of direct current control of the power, thus make the radio frequency export the decrease of power. Its electrical schematic diagram.
We can see from Fig. 3 the intersection of base and the intersection of voltage regulation and (voltage regulation), + 3 0V of power supply, Voltage, after controlling the module, send to XP2/ 4A of the transmitting set voice-operated control board module. This + 30V voltage produces pressure drop on R113, fetches pressure drop (about 1 on R113 in RP10, R110. 51V) ,Add to the intersection of N19B and the intersection of oppisite phase and input end of voltage comparator by R114 ‘ Have V2) ; The voice-operated control of the transmitting set is stiff inside + 10 volts (voltage regulation) The voltage passes R111( 18k) ,R112( 1. 8k) Partial pressure, fetch voltage (about 0 on R112. 87V) Add in-phase input end of N19B to ‘ Have V3) . When the mains voltage is normal, it enables V2> V3 to adjust RP10, then N19B exports the low level, this level receives D10/ 13 (see Fig. 2) ,Enable D10/ 1. 2 feet are disconnected, the radio frequency power of normal output of the transmitting set; As the stepping down of voltage of power, the voltage on R113 is reduced too, enable V2<V3, N19B exports the high level, this level enables D10/ 1. 2 feet are put through, supply the analog multiplier unit VX input end with after R168 and R175 partial pressure the direct-current control voltage of the power, make VX reduce, thus the decrease of power of radio frequency that makes the transmitting set output.
The electric capacity C52 in Fig. 3 just enables V2<V3 of N19B while guaranteeing to confirm the stepping down of voltage of power. But the not stable mains voltage fluctuation is filtrated. VD1 and R114 to guarantee N19B voltage comparator turn over, work and set up rapidly, R115 play a regenerative role, VD1 offers the passway for the discharging fast of C52.
4 conclusions
The radio frequency power amplifier circuit proves, this circuit is novel in design through real application, the circuit is simple and practical, of power on the heavy-duty state of the heavy current and present impedance mismatching of the radio frequency, built-in temperature great and three kinds of situations of stepping down of voltage of power o, can automatically control and protect the amplifying circuit of radio frequency power, has increased reliability and life time of the work of radio station.
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