JPS6024603B2 - FET oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the configuration of a microwave FET (field effect transistor) oscillator that oscillates by inserting a resonant circuit into its gate, and to temperature compensation of its oscillation frequency.

F to a planar circuit whose basic configuration is a microstrip line
The circuit shown in FIG. 1 is well known as an oscillator with an ET bonded thereto. A resonator 3 having a length approximately equal to the desired oscillation frequency of the gate 2 of the FET element 1 is connected, and a gate voltage is applied to the gate 2 from a choke bias circuit 4. Further, a feedback circuit 6 is connected to the source 5 of the FETI and grounded, an output line 8 and a choke bias circuit 9 are connected to the drain 7, and the output line 8 is cut off in terms of DC by a capacitor 10. . When this configuration is used, feedback is generated between the gate 2 and the drain 7 through the source feedback circuit 6, the FETI oscillates at the frequency of the gate resonator 3, and the oscillation output is taken out from the drain output line 8.

This FET oscillator has good oscillation efficiency and large output. Further, normally, the gate 2 is driven with a negative voltage, and the oscillation frequency has a characteristic that changes by changing the voltage applied to the gate. but,
The oscillation frequency of this oscillator is determined by the impedance of the FEHI seen from the gate 2 and the impedance of the resonator 3, so in order to satisfy the oscillation conditions at multiple frequencies, the oscillation frequency may jump to another frequency or change due to temperature changes. Since the impedance of the FETI seen from the gate 2 changes and the oscillation frequency changes, the oscillation frequency has a disadvantage of poor temperature stability. The actual value of the temperature stability of this oscillation frequency is 100 to 20 rudder PM/. It is 0.

FIG. 2 shows a conventional example of an FET oscillator that outputs from an output line 11 connected to a source 5 with a drain 7 grounded.

In this configuration, since the amount of internal feedback between the source 5 and the gate 2 is large, there is no need to form a feedback circuit externally, and when the resonator 3 is attached to the gate 2, oscillation occurs.

However, bias circuits 4 and 12 require negative voltage. The oscillator with this configuration also has the same drawbacks as shown in FIG. SUMMARY OF THE INVENTION An object of the present invention is to provide an FET oscillator which eliminates the above-mentioned drawbacks of the prior art, has a simple configuration, and has improved oscillation frequency jump and temperature stability.

The configuration of the present invention is to connect a dummy resistor in parallel with the resonator connected to the gate, supply a gate voltage by dividing the voltage between this dummy resistor and a resistor inserted between the power supply and the gate, and connect the dummy resistor to the resistor. It is constructed by inserting a V heat-sensitive semiconductor such as a varistor in series with a resistor inserted between the power source and the gate.

As a result, at frequencies other than the resonant frequency of the resonator, oscillation does not occur because the gate is terminated with a dummy resistor. Therefore,
There is no jump in the oscillation frequency, and since the terminal voltage of semiconductors such as varistors inserted in the bias circuit changes when the ambient temperature changes, the gate voltage also changes, which has the effect of keeping the oscillation frequency constant).

Hereinafter, the present invention will be explained in detail according to embodiments shown in the drawings.

FIG. 3 shows an embodiment of the present invention. A dummy resistor 13 (resistance value is r) is connected via a line 14 in parallel with the resonator 13 connected to the gate 2 of the conventional example shown in FIG.
A resistor 1 is connected between the gate bias choke 14 and the power supply terminal.
7 (resistance value is R) and a varistor 16 are inserted in series. At frequencies other than the resonant frequency of the resonator 13, the dummy resistor 15 is visible in the impedance of the resonator 13 and the line 14 seen from the gate 2, and the oscillation condition is not satisfied. Therefore, the oscillation frequency does not oscillate at frequencies other than the resonant frequency of the resonator 13, so there is no jump in the oscillation frequency. FIG. 4 shows the gate voltage supply V supply circuit in FIG. 3.

As can be seen from FIG. 4, since the gate is driven with a negative voltage, the voltage Vc applied to the terminal 19 of the gate 2 is (- V+VB)r VG=R+r.

Now, if the terminal voltage VB of the varistor 16 changes by △VB due to a change in ambient temperature, the gate voltage V'c becomes V'G
=←V+V8△VBX←V+VB)rJukai≦SheepR+r
= R+r, and the gate voltage changes by the amount.

Normally, while the terminal voltage outside the varisse changes by -3 V/°C, the gate voltage changes by approximately -3 V/°C.

Furthermore, the change in oscillation frequency when the gate voltage VG is changed is △L, and the change in oscillation frequency due to ambient temperature is △f2.
If the gate voltage VG changes with respect to the ambient temperature so that Δf, 0, Δf2=0, the oscillation frequency will be kept constant even if the ambient temperature changes.

The actual measured values of the FET oscillator in the normal HZ band are that △L is 15MHZ/V, and △f2 is -0.8MHZ/00
Met.

Therefore, the change in oscillation frequency due to the change in gate voltage with respect to the change in ambient temperature becomes MHZ no °C, and this is △f
2 and 0.8 MHZ·°C, which has the opposite characteristic. Therefore, in order to increase the change in the gate voltage VG, a plurality of varistors 16 may be inserted in series as shown in FIG.

Now, if n varistors are used, the change in gate voltage due to a change in ambient temperature will be n times greater, and the following equation: O.
By selecting R, r, and n so that 5M town no.degree. C. holds true, it is possible to construct an FET oscillator whose oscillation frequency does not change even if the ambient temperature changes.

The present invention is based on the drain grounded FE shown in the conventional example shown in FIG.
It is clear that the T oscillator has a similar effect. Further, as shown in FIG. 6, if a positive voltage is applied to the source 5 using the capacitor 22, choke 21, etc., the gate can be driven with a positive voltage.

In this case, in order to keep the oscillation frequency constant against changes in ambient temperature, a varistor 23 must be inserted in place of the dummy resistor 15.

At this time, the dummy resistor 15 may be grounded using the capacitor 24 at high frequency.

Using this configuration, it can be seen from FIG. 7, which shows the gate voltage supply circuit in this case, that the gate voltage changes as the ambient temperature changes.
V'G=W-VB-△V8×10 V80△V8)={S
Poison damage and 10 V8} 10 times ≦ R + r, and the change in the terminal voltage of the varistor is a negative coefficient, so the changes in the oscillation frequency with respect to the ambient temperature can be canceled out from Figures 3 to 5. As explained in , it is from Ming.

If you want to use a small dummy resistor 15 to prevent jumps in the oscillation frequency, but a large one to compensate for the temperature of the oscillation frequency, divide the dummy resistor 15 as shown in Figure 8, and add a high-frequency capacitor in the middle. Even if 24 is short-circuited, the effect of the present invention is the same.

Although the present embodiment has been described using a bar J star, the present invention is not limited to this, and the effects of the present invention are the same even in a heat-sensitive semiconductor whose terminal voltage changes depending on changes in ambient temperature.

Further, in this embodiment, an open-ended line is used as the gate resonator, but the line is not limited to this, and as shown in FIG.
5, the effect of the present invention is the same.

As described above, according to the present invention, since oscillation is not caused by the first resistor, which is a dummy resistor, at frequencies other than the resonant frequency of the resonator, jumps in the oscillation frequency can be prevented, and the varistor inserted in the gate voltage supply circuit can be Since the terminal voltage changes with the ambient temperature, the voltage applied to the gate changes, which has the effect of keeping the oscillation frequency constant regardless of changes in the ambient temperature.

[Brief explanation of drawings]

Figure 1 is a diagram showing a follow-up example of a source-grounded FET oscillator with a resonator at the gate, and Figure 2 is a diagram showing a follow-up example of a source-grounded FET oscillator with a resonator at the gate.
A diagram showing a conventional example of a drain-grounded FET oscillator, FIG. 3 is a connection diagram showing an embodiment of the present invention, and FIGS. 4 and 5 are gate voltage supply circuit diagrams for explaining the operation of FIG. 3. ,
Figure 6 is a connection diagram of another embodiment of the present invention, Figures 7 and 8.
This figure is a gate voltage supply circuit diagram for explaining the operation of FIG. 6, and FIG. 9 is a connection diagram of still another embodiment of the present invention. 2: FET gate, 15: first resistor (dummy resistor),
16: Varistor, 17: Second resistor, 18: Power supply terminal,
19: Gate terminal, 23: Varistor. O'muscle O Z figure O 4 figure ge 3 figure J figure gum figure talented Wa figure is J figure O? figure

Claims (1)

[Claims] 1. In an oscillator in which an FET is provided in a planar circuit whose basic configuration is a microstrip line, a resonant circuit is provided at the gate of the FET, a dummy resistor is connected to this gate in parallel with the resonant circuit, and the dummy resistor is At frequencies apart from the resonant frequency of the resonant circuit, the impedance connected to the gate has a resistance value approximately determined by this dummy resistor, and the bias circuit that supplies bias voltage to the gate includes the dummy resistor. 1. A FET oscillator characterized in that the bias circuit is provided with a heat-sensitive semiconductor.