JPS6029214Y2 - microwave transistor oscillator - Google Patents

Description

[Detailed description of the invention] The invention is based on the emitter-collector parasitic capacitance C8c and the base-emitter parasitic capacitance C1 of the microwave transistor.
This invention relates to a microwave oscillator that uses l:B as a return path.

In general, microwave transistor oscillators use packaged transistors, so the parasitic capacitance of the transistors can be used as a feedback circuit. Colpitts-type oscillators or Clapp-type oscillators are used as oscillation circuit configurations in the microwave frequency band field. It has been used and liked.

A typical conventional microwave transistor oscillator circuit is shown in FIG.

The oscillation circuit of this microwave transistor oscillator is a Clapp type microwave transistor oscillator, numeral 1 is a microwave transistor, and the collector is directly grounded.

The base is grounded through a series circuit of a distributed constant circuit element 9 and a variable capacitor 10, and a base bias voltage is supplied to one end of the variable capacitor 10 from the VEE terminal via a variable resistor 5 and a choke coil 7. The variable terminal is grounded via a resistor 8, and the base bias is supplied by resistor division.

On the other hand, the emitter is connected to -V through a series circuit consisting of a choke coil 2 and a stabilizing resistor 4.

Connected to E.

Capacitors 3 and 6 are high frequency bias capacitors for the emitter circuit and base bias circuit.

In the circuit shown in FIG. 1, the oscillation frequency is determined by the distributed constant circuit element 9 and the capacitor 10 on the base side of the microwave transistor 1, and the oscillation output is taken out from the output terminal 12.

The capacitor 11 is used for impedance matching with a load (not shown) connected to the output terminal 12.

In such a conventional microwave transistor oscillator, in order to obtain optimal oscillation conditions, the variable resistor 5 is adjusted to apply an optimal DC bias voltage to the base of the microwave transistor 1.

This has the advantage that the oscillation conditions of the microwave transistor 1 can be easily controlled by the variable resistor 5.

However, it is extremely difficult to design an oscillator to obtain stable oscillation operation over a wide range of changes in the power supply voltage VEH of a microwave transistor, or to sustain oscillation over a wide temperature range, and the oscillator configuration is complicated. They also have disadvantages, such as being large and expensive, making them expensive.

In this way, the application of a DC base bias voltage by an external adjustment circuit has the disadvantage that it also has an element of instability as an oscillator, such as an unstable oscillation state even if the temperature or power supply voltage is slightly changed depending on the bias voltage conditions. He was inviting me.

Also, for the emitter and collector of the microwave transistor,
There is also a microwave transistor oscillator that applies a DC bias voltage using a dual source of il I - Vmtzt + Vcc, but even with such an oscillator, it is possible to use a microwave transistor oscillator that applies a DC bias voltage using the dividing resistor shown in Figure 1. Similarly, it has the disadvantage that the oscillation state tends to become unstable due to fluctuations in temperature and power supply voltage.

An object of the present invention is to provide a microwave oscillator which has a simple configuration and which oscillates stably against fluctuations in power supply voltage, temperature, etc.

Next, the present invention will be explained with reference to the drawings.

In the embodiment of the present invention shown in FIG. 2, the collector of the microwave transistor 1 is directly grounded, and a variable capacitor 26 and a resonant coil 25 are connected in parallel between the base and the ground to form a parallel resonant circuit.

However, the ground of the coil 25 is a high frequency ground via the bias capacitor 6, and the ground side end of this coil is grounded in a direct current manner through a base bias resistor 28.

Furthermore, a series circuit of a distributed constant circuit element 9 and a variable capacitor 10 is taken out from the base as in FIG. There is.

On the other hand, on the emitter side, there is a variable capacitor 24 for parallel resonance.
and a parallel resonant circuit of the parallel coil 23 are connected.

However, the ground side end of the coil is connected to the high frequency ground via the bias capacitor 3, and is further connected to the -VEE terminal 21 via the stabilizing resistor 22 in terms of direct current.

The circuit shown in FIG. 2 also oscillates at a frequency determined by the distributed constant circuit element 9 and the capacitor 10, but the important thing about this circuit is that the coil 23 and capacitor 24 connected to the emitter side of the microwave transistor 1 a parallel resonant circuit configured with a capacitor 26 and a coil 25 connected to the base side of the microwave transistor 1, and a resistor 28 connected to the coil 25.

The resonant frequency of the parallel resonant circuit composed of the above-mentioned coil and capacitor is adjusted to be tuned to the oscillation frequency oscillated by the microwave transistor 1, the distributed constant circuit element 9, and the capacitor 10. In the early days,
(Actually, for a very short period of time), the high frequency equivalent circuit shown in FIG. 3 oscillates.

The oscillation circuit is a Colpitts type oscillation circuit, and 31 is the base-emitter capacitance C6II1 of the microwave transistor 1.
132 is the emitter-collector capacitance Csc, and the capacitance CEB
gCEC and the capacitor 24 serve as a feedback capacitor and constitute an oscillation circuit.

The oscillation state of the oscillation circuit shown in FIG. 3 is due to the instability of the self-bias voltage of the resistor 28 on the base side of the microwave transistor 1 shown in FIG. It becomes stable.

(Actually, in the experiment, a white noise-like oscillation state occurred.

) Due to this initial unstable oscillation, the oscillation state changes as shown in Fig. 4 due to the dynamic capacitance between the base and collector of the microwave transistor 1 caused by fluctuations in the self-bias voltage of the resistor 28, feedback capacitance, and 24, 31, and 32. Let's move on to the high frequency equivalent oscillation circuit.

The high frequency equivalent oscillation circuit shown in FIG. 4 is generally called a Clapp oscillation circuit.

By oscillating with the oscillation circuit shown in FIG. 4, the coil 23, capacitor 24, coil 25, and capacitor 26 shown in FIG.
The parallel resonant circuit composed of the microwave transistor 1 and the distributed constant circuit element 9 has an infinite impedance.
, the capacitor 10 oscillates.

FIG. 5 shows the characteristics of the 3 GHz band microwave transistor oscillator obtained with the above configuration.

The horizontal axis of FIG. 5 shows the power supply voltage, and the vertical axis shows the oscillation force and the fluctuation of the oscillation frequency due to the fluctuation of the power supply.

As is clear from FIG. 5, it operates normally and stably even at very low power supply voltages.

Furthermore, stable oscillation was achieved at an operating temperature of -30 to +70 DEG C., and the frequency stability was about 1.times.10@-4.

It has also been revealed that noise-like oscillation occurs when the power supply voltage is about 0 to 4V.

This shows that, as explained in FIG. 3, there is a transition to stable oscillation after passing through the region of unstable oscillation.

As is clear from the embodiments described above, according to the present invention, a base voltage variable resistor or the like is used by connecting the resonant circuit of a coil and a capacitor and the resistor 28 to the emitter and base sides of the microwave transistor. Without incident,
A stable microwave transistor oscillator can be obtained.

Further, in the present invention, the coil and capacitor are described as lumped constant elements, but it goes without saying that they can also be constructed as distributed constant circuits.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional oscillator, FIG. 2 is a circuit diagram of an embodiment of the present invention, FIG. 3 is an equivalent circuit diagram of the circuit in FIG. FIG. 5 is an equivalent circuit diagram of the circuit shown in FIG. 2 during stable operation. FIG. 5 is a curve diagram of the oscillation output characteristics and oscillation frequency characteristics of the circuit shown in FIG. 2 with respect to changes in the power supply voltage. 1...Microwave transistor, 9. Curved/distributed constant circuit element, 10...Series circuit capacitor,
23.24... Coil and capacitor for emitter side parallel resonant circuit, 25, 26... Coil and capacitor for base side parallel resonant circuit, 28... Base bias resistor.

Claims (1)

[Scope of utility model registration request] A microwave transistor whose collector is grounded, a parallel resonant circuit consisting of a coil and a capacitor that can be tuned to a desired oscillation frequency, which are connected between the base and ground of this transistor and between the emitter and ground, respectively, and between the base and ground. 1. A microwave transistor oscillator comprising: a series circuit of a distributed constant circuit element and a capacitor connected to the base; and a base resistor connected via an AC blocking means between the base and ground.