JPH0614495Y2 - High frequency oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high frequency oscillator, and more particularly to a high frequency oscillator using a coaxial resonator and an oscillating transistor.

(Prior Art) Conventionally, in a mobile communication device such as a car telephone, a coaxial resonator having a high Q ₀ is used as a high-frequency oscillator in order to prevent communication interference of an adjacent channel having a very narrow channel band. ing.

FIG. 3 is a plan view showing an example of such a conventional high frequency oscillator. In this high frequency oscillator 1, the circuit is
As shown in the figure, one end of the coaxial resonator 2 is grounded, the collector of the oscillation transistor 3 is grounded via a grounding capacitor 4, and the other end of the coaxial resonator 2 is connected via a coupling capacitor 5. It is connected to the base of the oscillation transistor 3.

(Problems to be Solved by the Invention) In this high-frequency oscillator 1, in order to use Q ₀ of the coaxial resonator 2 at a sufficiently high _value , the capacity of the coupling capacitor 5 may be reduced. When the capacitance of the capacitor 5 is reduced, the ratio (C / N) between the oscillation output level and the phase noise level of the sideband is improved, but the oscillation output level is decreased. On the other hand, if the capacitance of the coupling capacitor 5 is increased in order to increase the oscillation output level, the oscillation output level rises, but the phase noise level rises further, and as a result, the C / N deteriorates.

As described above, in the conventional high frequency oscillator, the C / N could not be improved without reducing the oscillation output level.

Therefore, the main purpose of this invention is to improve C / N without reducing the oscillation output level.
It is to provide a high frequency oscillator.

(Means for Solving the Problems) The present invention is directed to a substrate made of an insulating material, a first ground pattern formed on one main surface of the substrate, and a space between the first ground pattern and the first ground pattern on one main surface of the substrate. A second ground pattern formed by separating the two, a coaxial resonator having one end connected to the first ground pattern, and a base connected to the other end of the coaxial resonator via a coupling capacitor, An oscillating transistor whose collector is connected to the second ground pattern via a grounding capacitor and a second main surface side of the substrate,
A high-frequency oscillator, comprising: a conductor connecting the first ground pattern and the second ground pattern, wherein an inductance is formed by the conductor between the first ground pattern and the second ground pattern.

(Operation) A conductor provided on the other main surface side of the substrate between the first ground pattern that is the ground point at one end of the coaxial resonator and the second ground pattern that is the ground point on the collector side of the oscillation transistor Since an inductance is formed by this, the capacitance of the coupling capacitor is reduced accordingly. Then, C / N is improved. The oscillation output level rises for unknown reasons.

(Effect of the Invention) According to this invention, since the inductance is newly provided, the capacitance of the coupling capacitor must be reduced in order to obtain the same oscillation frequency as the conventional one. As a result, C
/ N was able to be improved.

Further, in the high-frequency oscillator according to the present invention, since the conductor connecting the first ground pattern and the second ground pattern is provided on the other main surface side of the substrate, one main surface of the substrate can be effectively used. Therefore, the overall size can be reduced.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments below with reference to the drawings.

(Embodiment) FIG. 1 is a plan view showing an embodiment of the present invention. The high frequency oscillator 10 includes a case 12 having a base portion made of a conductor and a cover portion. A substrate 14 made of an insulating material is attached on the base portion of the case 12.

On one main surface of the substrate 14, the first ground pattern 16a is provided on one end side and the second ground pattern 1 is provided on the other end side.
6b has conductor patterns 18a, 18b,
18c and 18d are formed at intervals. Further, the first ground pattern 16a has an end portion formed over one end surface of the substrate 14, and the end portion is connected to the base portion of the case 12 by, for example, soldering. The second ground pattern 16b also has an end portion formed over the other end surface of the substrate 14, and the end portion is connected to the base portion of the case 12 by, for example, soldering.

The outer conductor (one end) of the coaxial resonator 20 is connected to the first ground pattern 16a. The inner conductor (other end) of the coaxial resonator 20 is connected to one end of the coupling capacitor 22 by the conductor pattern 18a. The other end of the coupling capacitor 22 is connected to the base of the oscillation transistor 24 by the conductor pattern 18b.

Further, a capacitor 26 is provided between the base and the emitter of the oscillating transistor 24 so that the conductor patterns 18b and 1
8c is connected. The emitter of the oscillation transistor 24 is connected to the first ground pattern 16 via the capacitor 28.
connected to a. Further, the collector of the oscillation transistor 24 is connected to one end of the grounding capacitor 30 by the conductor pattern 18d, and the other end of the grounding capacitor 30 is connected to the second ground pattern 16b. That is, the collector of the oscillation transistor 24 is connected to the grounding capacitor 30.
Is connected to the second ground pattern 16b via. Therefore, the high frequency oscillator 10 is configured as a Colpitts oscillator.

In this high frequency oscillator 10, the ground point of the coaxial resonator 20 and the ground point of the collector side of the oscillation transistor 24 are the first.
Since they are connected via the ground pattern 16a, the second ground pattern 16b, and the case 12, the equivalent circuit thereof is as shown in FIG. Inductance L is formed between and. Therefore, in this high frequency oscillator 10, the value of the coupling capacitor 22 must be made smaller than that of the conventional example shown in FIG. 3 in order to obtain the same oscillation frequency.

According to an experiment conducted by the inventor, when the high-frequency oscillator 10 and the conventional example shown in FIG. 3 were oscillated at the same oscillation frequency (1500 MHz), the high-frequency oscillator 10 showed that the coupling capacitor 22 was Although the value was decreased, the oscillation output level increased by 2 dB. The reason for this has not been analyzed. The C / N ratio was improved as expected because the value of the coupling capacitor 22 was reduced.

Further, in the high frequency oscillator 10, the case 12 for connecting the first ground pattern 16a and the second ground pattern 16b is provided on the other main surface side of the substrate 14, so that one main surface of the substrate 14 can be effectively used. Available,
The overall size can be reduced.

The ground point of the coaxial resonator 20 and the oscillation transistor 2
In order to form the inductance L with the ground point of No. 4, a ground pattern is formed on the entire back surface of the substrate 14, and through holes are formed in the substrate 14 at intervals.
Then, those ground points may be used as a ground pattern through through holes. The point is that the ground point at one end of the coaxial resonator 20 and the ground point of the oscillation transistor 24 may be separated.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention. FIG. 2 is an equivalent circuit diagram of the embodiment shown in FIG. FIG. 3 is a plan view showing an example of a conventional high frequency oscillator which is the background of the present invention. FIG. 4 is a circuit diagram of the conventional example shown in FIG. In the figure, 10 is a high frequency oscillator, 12 is a case, and 14
Is a substrate, 16a is a first ground pattern, 16b is a second ground pattern, 18a to 18d are conductor patterns, 20 is a coaxial resonator, 22 is a coupling capacitor, and 24 is an oscillation transistor.

Claims (1)

[Scope of utility model registration request] 1. A substrate made of an insulating material, a first ground pattern formed on one main surface of the substrate, and a second ground pattern formed on one main surface of the substrate at a distance from the first ground pattern. Ground pattern, a coaxial resonator whose one end is connected to the first ground pattern, whose base is connected to the other end of the coaxial resonator through a coupling capacitor, and whose collector is connected through a grounding capacitor An oscillation transistor connected to the second ground pattern; and a conductor provided on the other main surface side of the substrate for connecting the first ground pattern and the second ground pattern, A high-frequency oscillator, wherein an inductance is formed by the conductor between a ground pattern and the second ground pattern.