JPH05288829A - Radar transmitter - Google Patents

Abstract

PURPOSE:To prevent a noise from being generated and to eliminate a need for a diode whose breakdown strength is high and whose electric current is large by a method wherein excess energy which is generated on the primary side of a pulse transformer is absorbed when the oscillation of a transmitting valve is stopped. CONSTITUTION:Pulses which are output from a pulse generation circuit 10 are amplified by using a transistor TR3 in an unsaturated manner; they are input to an PET 1 via a pair of transistors TR4, TR5 An FET 2 is added to the TR3; the pulses fall quickly by means of the FET 2. An FET 3 is connected to the primary side of a pulse transformer T1 via a resistor R2. It is turned on when the PFT 1 is turned off. It is turned off when the FFT 1 is turned on. When the oscillation of a tarnsmitting valve V1 is stopped and excess evergy is generated at the primary side of the pulse transformer T1, the energy is consumed by the resistor R2. As a result, it is possible, thanks to the FET 3, to prevent that following pulses become dull and that an inverse resonance is caused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar transmitter using a magnetron or the like as a transmission tube, and more particularly to improvement of a modulation circuit.

[0002]

2. Description of the Related Art FIG. 2 shows the structure of a radar transmitter according to a conventional example. The radar transmitter shown in this figure uses a magnetron V1 as a transmitter tube and is of a type called a line type pulsar.

This circuit has a thyristor CD1 which functions as a switch. The trigger input T is amplified by the transistors TR1 and TR2 and then supplied to CD1, which is triggered by T. The voltage VC is
It is a power source for TR1 and TR2.

The circuit also includes a pulse forming network (PFN) A1 for storing energy supplied from the power supply VH. PFN is used for C
This is because D1 is a device that cannot gate off.
A1 resonates with the charging choke L1 and is charged to about 2VH. The pulse width is given by PW.

When CD1 is turned on, a voltage is applied to the primary winding of the pulse transformer T1 by the energy stored in A1. The choke coil L2 has a low impedance when the CD1 is turned on, and is delayed so that the energy of A1 is added to T1. Here, the impedance of A1 and the primary impedance of T1 are set to be the same, and the primary side of T1 has about 1 of the voltage charged in A1.
A voltage of / 2 is applied. This voltage is boosted by T1 and drives V1. V1 thereby generates microwaves.

The impedance of V1 greatly differs between when oscillating and when not oscillating. The choke L3 absorbs the surplus energy of A1 when the oscillation of V1 is stopped. This is V1
This is because it is possible to prevent the excess energy of A1 accompanying the stop of the oscillation of (1) widens the trailing edge of the falling edge of the oscillation output pulse, and as a result, a noise ring is generated near the center point (own ship position) of the radar image.

Further, when the oscillation of V1 is stopped, the pulse output may swing in the positive direction due to the reverse resonance, and noise may be generated. In this circuit, the diode C
D2 and resistor R1 are inserted to prevent reverse resonance.

[0008]

As described above, in the conventional transmitter, since the thyristor is used, it is necessary to use the PFN because the off operation is required. Therefore, in order to prevent noise generation, a high withstand voltage on the secondary side of the pulse transformer,
A high current diode was needed.

The present invention has been made to solve the above problems, and an object of the present invention is to prevent the generation of noise and to eliminate the need for a diode having a high breakdown voltage and a large current.

[0010]

In order to achieve such an object, the first aspect of the present invention is that the primary side of the pulse transformer is connected in series to the primary side of the pulse transformer by applying a pulse signal to the gate. The first FET for applying the pulse voltage and the first side connected in parallel to the primary side of the pulse transformer
Means for turning on / off in a phase opposite to that of the FET and absorbing excess energy on the primary side of the pulse transformer when the FET is turned on.

According to a second aspect of the present invention, the first FET is connected in series to the primary side of the pulse transformer, and the first FET drives the first FET to apply the pulse voltage to the primary side of the pulse transformer by applying the pulse signal to the gate. And a second FET that is added to the amplifier and shapes the pulse signal.

A third aspect of the present invention is characterized by including a transistor pair for reducing the impedance so as to drive the first FET at high speed by the pulse signal.

[0013]

In the first aspect of the present invention, when the pulse signal is applied to the gate of the first FET, the pulse voltage is applied to the primary side of the pulse transformer. If excess energy is generated on the primary side of the pulse transformer when the oscillation of the transmission tube is stopped, this is absorbed by the excess energy absorbing means, and a high withstand voltage and a large current are applied to the secondary side of the pulse transformer to prevent reverse resonance. It is not necessary to provide a diode or the like.

Further, in claim 2, the second FE
The pulse signal is shaped by T. Therefore, rounding of rising and falling of the output is suppressed.

Further, in claim 3, the gate impedance of the first FET is lowered by the transistor pair, and the driving thereof is accelerated.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. The same components as those of the conventional example shown in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows a circuit configuration of a radar transmitter according to an embodiment of the present invention. In this embodiment, T is given to the pulse generating circuit 10 and the pulse width is given by PW. The pulse output from the pulse generation circuit 10 is unsaturatedly amplified by the transistor TR3, and is fed to the FET1 through the transistor pair TR4 and TR5.
Entered in. FET2 is added to TR3,
FET2 accelerates the fall of the pulse.

TR4 and TR5 have the function of lowering the impedance in order to drive the gate of the FET1 at high speed. Note that a similar transistor pair may be further added. When the FET1 is turned on, its impedance is low, and therefore VH charged in the capacitor C1 is added to the primary side of T1 almost as it is. Since the maximum voltage VH is added to the FET1, a withstand voltage lower than that of CD1 is sufficient. Therefore, the impedance of T1 need not be so low.

Further, the FET3 is connected to T1 via the resistor R2.
Is connected to the primary side of the FET1 and is turned on when the FET1 is off, and turned off when the FET1 is on. This eliminates the need to provide a high breakdown voltage, large current diode or resistor on the secondary side of T1. That is, even if excess energy is generated on the primary side of T1 when the oscillation of V1 is stopped, this energy is consumed by R2, so that FET3 prevents the trailing edge of the pulse from being blunted and the reverse resonance from occurring. In the low power transmitter, the FET 3 can be replaced with a diode and a damping resistor.

[0020]

As described above, according to the first aspect of the present invention.
According to this, excess energy generated on the primary side of the pulse transformer when the oscillation of the transmission tube is stopped can be absorbed, and on the secondary side of the pulse transformer to prevent reverse resonance, high price and high withstand voltage, It is not necessary to provide a high current diode or the like. As a result, price reduction and high reliability are realized.
According to the second aspect of the present invention, the pulse signal is shaped by the second FET, and the rounding of the rising and falling of the output is suppressed. Further, the pulse width can be easily switched by determining the pulse width of the pulse signal.

According to the third aspect, the gate impedance of the first FET is lowered by the transistor pair, and the driving thereof is accelerated.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a radar transmitter according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a radar transmitter according to a conventional example.

[Explanation of symbols]

 10 pulse generation circuit V1 magnetron T1 pulse transformer C1 capacitor TR3, TR4, TR5 transistor FET1, FET2, FET3 FET

Claims (3)

[Claims] 1. A radar transmitter comprising: a transmission tube that oscillates microwaves; and a pulse transformer that oscillates the transmission tube by applying a pulse voltage to the primary side, wherein the primary side of the pulse transformer is connected in series to a gate. The first FET that applies a pulse voltage to the primary side of the pulse transformer by applying the pulse signal of, and is connected in parallel to the primary side of the pulse transformer and turns on in a phase opposite to that of the first FET. And a means for absorbing excess energy of the radar transmitter. 2. A radar transmitter comprising a transmitter tube that oscillates microwaves and a pulse transformer that oscillates the transmitter tube by applying a pulse voltage to the primary side, wherein the primary side of the pulse transformer is connected in series to the gate. The first FET that applies a pulse voltage to the primary side of the pulse transformer by applying the pulse signal of, the amplifier that amplifies the pulse signal that drives the first FET, and the second FET that is added to the amplifier and shapes the pulse signal. FET
A radar transmitter comprising: 3. The radar transmitter according to claim 1, further comprising a transistor pair that reduces impedance so as to drive the first FET at high speed by a pulse signal.