JP2842483B2 - High frequency pulse power amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency pulse power amplifier using a grounded base type power amplifying transistor.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing a conventional high-frequency pulse power amplifier. In the figure, IN is an input terminal, 1 is a DC cut capacitor, 2 is an input side matching circuit, 3 is a base-grounded high-frequency transistor, 4 is an input side matching circuit, 5 is a DC cut capacitor, 6, 7 Is a high-frequency coil, 8 is a DC power supply, 9 is a power supply (capacitor) for supplying a pulse current to the transistor 3, 10 is a high-frequency capacitor, and OUT is an output terminal.

When amplifying a high-frequency and high-power pulse signal, a grounded base type amplifying transistor is generally used in class C operation, and the transistor is operated by an input signal.

The matching circuit 2 is a circuit for matching the impedance of the transmission line of the high-frequency input signal A with the transistor 3, whereby the input signal is input to the transistor 3 without reflection, and for the first time upon arrival of the input signal. The transistor 3 operates. The signal amplified by the transistor 3 undergoes impedance conversion by the matching circuit 4 in the same manner as on the input side, and is output from the output terminal OUT. The high-frequency coils 6 and 7 block a high-frequency signal and form a path through which a bias current (pulse current) necessary for the operation of the transistor 3 flows. The high-frequency capacitor 10 prevents a leakage signal from the high-frequency coil 7 from flowing into the DC power supply 8.

[0005]

In such a class C operation pulse amplifier, as shown in FIG. 6, a harmful noise spurious is generated when the pulse signal A rises and falls, particularly when the pulse signal A falls. As a method of reducing this noise spurious, there is a method of smoothly shaping the rising and falling edges of the input signal waveform.
The effect of the waveform shaping fades.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and it is possible to easily control ON / OFF of a class-C operation transistor by an external control signal, and to control the operation of the transistor when the high-frequency signal falls. It is an object of the present invention to provide a high-frequency pulse power amplifier capable of preventing noise spurious from occurring and obtaining a high-quality output.

[0007]

According to the present invention, there is provided a high-frequency pulse power amplifier having an input terminal to which a high-frequency input signal is coupled, a grounded base type power amplifying transistor, a driving power supply and an output terminal. , The emitter is connected to the negative side of the driving power source, a resistor is inserted between the connection point and the base, and an external control circuit is connected to the connection point. The operation of the transistor at the time of a signal falling is controlled.

According to a second aspect of the present invention, the external control circuit includes a capacitor charged by the external control input and a charging resistor, and the external control input is supplied immediately before the falling of the high frequency input signal.

According to a third aspect of the present invention, the external control circuit includes a capacitor, a power supply for charging the capacitor, and a switch for discharging, and the switch is turned on when a high-frequency input signal falls.

[0010]

According to the present invention, since the emitter potential of the transistor can be controlled by an external control input, the noise spurious can be reduced by smoothly controlling the emitter potential when the high-frequency input signal falls. .

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the emitter of the transistor 3 is connected to the negative side of the DC power supply 8 via the high-frequency coil 6. A resistor 11 is inserted between the connection point O and the base of the transistor 3. 12 is an external control input terminal IN
This is a charging resistor inserted between o and the connection point O. 1
A capacitor 3 is inserted between the connection point O and the ground. 14 is a high-frequency capacitor. Other configurations are the same as those in FIG.

In this configuration, as in the conventional case, the transistor 3 performs an amplifying function only when a high-frequency input signal arrives. The external control input terminal INo is shown in FIG.
As shown in the figure, t ₁ immediately before the falling time t ₀ of the high-frequency input signal.
Is supplied with a voltage signal Ec. As shown in FIG. 2B, the capacitor 13 is charged by the voltage signal Ec with a time constant determined by the capacitance and the resistance value of the charging resistor 12, so that when the voltage Vc of the capacitor 13 increases to a certain value, The state where the emitter and the base of the transistor 3 are reverse-biased is set, and the transistor 3 is turned off.

If the specifications are set so that the OFF timing of the transistor 3 is before the falling time t _{0 of} the high-frequency input signal, the operation of the transistor 3 is smooth with respect to the falling of the high-frequency input signal. And the occurrence of the noise spurious is prevented.

In the above embodiment, the high-frequency input signal is turned off.
Before turning off the transistor 3 smoothly, the turning off operation of the transistor 3 causes the high frequency input signal to be turned off steeply.
If it is not based on the waveform, the generation of noise spurious can be suppressed, and thus the circuit shown in FIG. 3 can be used.

In FIG. 3, 15 is a charging power source, 16 is a capacitor, and 17 is a discharging switch.

[0016] In this arrangement, leave charge the capacitor 16, as shown in (B) in FIG. 4, the falling just before t ₃ of the high frequency input signal, and ON the switch 17, the electric charge of the capacitor 16 Discharge. Thus, the emitter of the transistor 3 becomes a negative potential with respect to the base, the transistor 3 is turned ON at time t _2. As shown in FIG. 4C, if the specifications are set so that the high-frequency input signal falls during the ON period of the transistor 3, the occurrence of noise spurious can be prevented.

[0017]

As described above, according to the present invention, the emitter potential of the class C operation transistor can be controlled from the outside, and the operation of the transistor at the fall of the high-frequency signal is controlled to prevent the generation of noise spurious. High quality pulse output can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the embodiment.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a waveform chart for explaining the operation of the other embodiment.

FIG. 5 is a circuit diagram of a conventional high-frequency pulse amplifier.

FIG. 6 is a waveform chart for explaining a problem of the above conventional example.

[Explanation of symbols]

 1, 5 DC cut capacitor 2, 4 Matching circuit 3 Transistor 6, 7, 10 High frequency coil 8 DC power supply 9 Power supply capacitor 12 Charging resistor 13 Capacitor 14 High frequency coil 15 Charging power supply IN input terminal OUT output terminal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ identification code FI H04L 27/20 H04L 27/20 C (58) Investigated field (Int.Cl. ⁶ , DB name) H03K 3/80 H03C 1 / 36 H03F 1/32 H03F 3/189

Claims (3)

(57) [Claims] An input terminal for coupling a high frequency input signal;
In a high-frequency pulse power amplifier including a base-grounded power amplification transistor, a drive power supply and an output terminal, the emitter is connected to the negative electrode side of the drive power supply, and a resistor is inserted between the connection point and the base; A high-frequency pulse power amplifier, wherein an external control circuit is connected to the connection point, and the external control circuit controls the operation of the transistor when the high-frequency input signal falls. 2. The external control circuit according to claim 1, wherein the external control circuit comprises a capacitor charged by the external control input and a charging resistor, and the external control input is supplied immediately before the falling of the high-frequency input signal. High frequency pulse power amplifier. 3. The external control circuit according to claim 1, wherein the external control circuit has a capacitor, a power supply for charging the capacitor, and a switch for discharging, and the switch is turned on immediately before the fall of the high-frequency input signal. High frequency pulse power amplifier.