JPS6268306A - Electronic tuning oscillator - Google Patents

Abstract

PURPOSE:To obtain a wide band electronic tuning oscillator having a prescribed performance by connecting a negative resistive element to a resonance circuit so as to use the gain of the negative resistive element thereby reducing the loss of the resonance circuit and improving the reduction in the Q of the main resonator even when the resonance circuit is coupled densely. CONSTITUTION:Most of the loss of the resonance circuit comprising a varactor diode 4 and a transmission line 5 is compensated by the gain of the negative resistive element 4 (e.g., a bipolar transistor) so as to approach the circuit to a no loss circuit. That is, the gain of the negative resistive element 10 is made equal to the loss of the resonance circuit comprising the varactor diode 4 and the transmission line 5 or below thereby bringing the circuit close to the no loss circuit. Since a large Q is obtained in the main resonator 3 even when the circuit is coupled densely, the output fluctuation, noise and load fluctuation characteristic are improved even when the electronic tuning oscillator is operated at a wide band.

Description

[Detailed Description of the Invention] [Summary] An electronically tuned oscillator is composed of a variable capacitance diode and a transmission line, and by changing the capacitance value of this diode, the resonant frequency (
That is, a negative resistance element is connected to a resonant circuit that can change the oscillation frequency of the electronically tuned oscillator to reduce the loss of this circuit, so a broadband electronically tuned oscillator can be obtained.

[Industrial application field]

The present invention relates to improvements in electronically tuned oscillators.

Electronically tuned oscillators can change their oscillation frequency using an external control voltage, so they are used as modulators or voltage-controlled oscillators in microwave bands, for example, but when the oscillation frequency of this oscillator is varied over a wide range, , it is necessary that fluctuations in output power and noise components included in the output be small.

[Conventional technology]

FIG. 2 shows a circuit diagram of a conventional example, and FIG. 3 shows a characteristic diagram of FIG. 2.

Note that the transistor bias circuit is omitted.

As shown in FIG. 2, the main resonator (for example, the resonant frequency fo
3 is a dielectric resonator with a negative resistance element 1 at one end,
It is magnetically coupled at point a to the transmission line 2, which has the resistor 7 connected to its other end, and is also magnetically coupled to the transmission line 5, which has the variable capacitance diode 4 connected to its one end.

Therefore, when the applied voltage of the variable capacitance diode 4 is changed to change the capacitance value, the sub-resonant frequency (1) of the resonant circuit composed of this diode and the transmission line 5 is value) changes, the resonant frequency fo of the main resonator 3 changes, and the oscillation frequency of the electronically tuned oscillator composed of the transmission line 2, the main resonator 3, the negative resistance element 1, and the resonant circuit changes.

Note that point a is a point where fo is likely to oscillate.

Figure 3 shows the relationship between the voltage applied to the variable capacitance diode 4, the relative oscillation frequency, and the output power when the strength of the coupling between the resonant circuit and the main resonator 3 is changed in the circuit shown in Figure 2. A characteristic diagram is shown.

As shown in the figure, in order to greatly change the oscillation frequency of the electronically tuned oscillator, the coupling between the resonant circuit and the main resonator 3 is tightly (
solid line), the low Q variable capacitance diode 4
The Q of the main resonator 3 is lower than in the case of loose coupling due to the influence of the resonant circuit including .

Note that in the case of loose coupling, the characteristics are opposite to those in the case of tight coupling.

In FIG. 4, a resonant circuit composed of a variable capacitance diode 4 and a transmission line 8 is connected to a main resonator composed of a transmission line 9 via a DC blocking capacitor, so that the coupling is caused by a second
It is denser than the circuit configuration shown in the figure.

Note that since this circuit does not use a dielectric resonator as the main resonator, the Q of the main resonator coupled to the resonant circuit is lower than in the case of the circuit configuration shown in FIG.

For this reason, the oscillator is capable of wide-band oscillation, but as the Q decreases, the amount of noise included in the output power increases, and the oscillation frequency changes greatly when the oscillator load fluctuates.

Note that these electronically tuned oscillators use a microstrip line formed on an alumina substrate or a flow glass substrate as a transmission line, and a bipolar transistor, field effect transistor, Gunn diode,
It is constructed by connecting a negative resistance element such as an invat diode.

[Problem that the invention seeks to solve]

As explained in detail above, when the main resonator and the resonant circuit of an electronically tuned oscillator are closely coupled and the oscillation frequency is varied over a wide range, the output voltage fluctuation becomes large, or the noise and load fluctuation characteristics increase. There is a problem in that it is difficult to realize a broadband electronically tuned oscillator with a predetermined performance because of the deterioration.

[Means for solving problems]

The above problems are solved by the electronically tuned oscillation 2g of the present invention, which connects the intrinsic resistance element 10 to a resonant circuit and reduces the loss of the resonant circuit by the gain of the negative resistance element.

[Effect]

In order to operate the electronically tuned oscillator over a wide band, as can be seen from FIG. 3, the Q of the main resonator when tightly coupled should be made higher.

In the present invention, the loss imparted to the main resonator 3 is reduced by reducing the loss of the resonant circuit to make it close to a lossless circuit,
Even if the main resonator and the resonant circuit are tightly coupled, a higher Q can be obtained.

That is, a negative resistance element 10 is connected to one end of the transmission line 5,
The gain of this element 10 was set to be equal to or less than the loss of the resonant circuit including the variable capacitance diode 4 to reduce the loss of the resonant circuit, thereby making it a nearly lossless circuit.

Therefore, even if the resonant circuit and the main resonator are closely coupled, the Q of the main resonator can be made higher than before, so a broadband electronically tuned oscillator with a predetermined performance can be obtained.

〔Example〕

FIG. 1 shows a block diagram of an embodiment of the invention.

In addition, the same reference numerals indicate the same objects throughout the plan, the dotted line parts are the parts added in the present invention, 1 is a negative resistance element,
2 indicates a transmission line.

As shown in the figure, most of the loss in the resonant circuit composed of the variable capacitance diode 4 and the transmission line 5 is compensated for by the gain of the intrinsic resistance element (for example, a bipolar transistor), and this circuit is converted into a lossless circuit. It was close to.

That is, the gain of this negative resistance element 10 is changed by the variable capacitance diode 4. This circuit can be made close to a lossless circuit by making the loss equal to or less than the loss of the resonant circuit constituted by the transmission line 5.

Therefore, even if this circuit is tightly coupled, the Q of the main resonator 3 can have a larger value than the conventional one, so even if the electronically tuned oscillator is operated over a wide band, there will be no output fluctuations or noise.

Load fluctuation characteristics are improved.

〔Effect of the invention〕

As explained in detail above, even if the resonant circuits are closely coupled, the reduction in the Q of the main resonator can be improved, so there is an effect that a broadband electronically tuned oscillator with a predetermined performance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, Figure 2 is a circuit diagram of a conventional example. Figure 3 is the characteristic diagram of Figure 2, FIG. 4 shows a circuit diagram of another conventional example. In the figure, 1.10 is a negative resistance element, 2.5 and 8.9 are transmission lines, 3 is a dielectric resonator, 4 is a variable capacitance diode, 7 indicates a resistor. Another 7th subordinate-come A row / 7th class H Figure 4

Claims (1)

[Claims] A transmission line (2) connected to one end of a negative resistance element (1).
), a main resonator (3) coupled to the transmission line, and a resonant circuit composed of the variable capacitance element (4) and the transmission line (5) coupled to the main resonator. An electronically tuned oscillator, characterized in that a negative resistance element (10) is connected to the resonant circuit, and the loss of the resonant circuit is reduced by the gain of the negative resistance element (10).