JPH0522033A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To provide the oscillation circuit for a microwave band which can reduce a loss and can be miniaturized in a height-wise direction. CONSTITUTION:A local oscillation circuit 7 is composed of a Monolithic Microwave Integrated Circuit (MMIC) oscillator 9 equipped with an FET and a resonator 10 connected for stabilizing the oscillation frequency of the oscillator. This resonator 10 is ring-shaped and adjacently arranged in a distance from several mum to dozens of mum to the prescribed position of a microstrip line 16 constituting a feedback loop connected to the FET constituting the oscillator. Further the resonator is formed in the shape of a thin film by depositing a high temperature super-conductive material, and YBCO or niobium, etc., for example, is used for this high temperature super-conductive material. Moreover, one part of the microstrip line adjacent to the resonator is formed as a circular arc- shaped part 16a having the same center as that of the resonator and the central angle of 90 deg..

Description

Detailed Description of the Invention

[0001]

The present invention relates to an oscillator circuit,
More specifically, it relates to an oscillation circuit integrated into an IC in the microwave band.

[0002]

2. Description of the Related Art In recent years, with the rapid development of information network systems, the demand for satellite communication systems has increased rapidly, and the frequency band is becoming high frequency (microwave).
Along with this, there is an increasing demand for an oscillation circuit applied as a local oscillation circuit to a down converter that converts a high frequency signal into a low frequency signal.

In response to the demand for downsizing and cost reduction of such communication equipment, the above-mentioned oscillation circuit and the like also include a microwave integrated circuit MIC (microwave) mainly composed of a transmission line (microstrip line or the like) formed on a dielectric substrate. integrated cir
cuit).

By the way, in this type of oscillator circuit, a large Q cannot be obtained with a single semiconductor used. Therefore, in the case of a fixed frequency oscillator, a cylindrical or spherical dielectric resonator formed of a ceramic or the like having a high dielectric constant is used. A method of improving the frequency stability by bringing the feedback circuit close to the microstrip line is used.

[0005]

However, such a dielectric resonator has a size in the height direction of about several millimeters, although it depends on the resonance frequency. On the other hand, since the microstrip lines other than the dielectric resonator such as circuit wiring are formed by vapor deposition or the like, the thickness thereof is very thin. As a result, only the dielectric resonator portion protrudes upward, which is a bottleneck in downsizing the entire circuit (especially in the thickness direction).

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such a background, and an object thereof is to provide an oscillation circuit which has a small loss and can be miniaturized in the height direction. To do.

In order to achieve this object, in the oscillator circuit according to the present invention, the FET provided on the semi-insulating substrate and the superconducting material disposed close to the microstrip line of the feedback circuit wiring connected to the FET. And a portion of the microstrip line close to the resonator is formed in an arc shape of approximately 90 degrees parallel to the circumference of the resonator.

[0008]

The signal output from the oscillation circuit is totally reflected by the resonator in a frequency-selective manner, whereby an oscillation circuit with high stability is obtained. Since the resonator is formed in a ring shape, the radiation loss is small and the performance is improved. Furthermore, since such a resonator is formed of a superconductor thin film, the surface resistance is much lower than that of a normal conductor, and the resonator has a sharp characteristic with a higher Q and the stability of the oscillation frequency is improved.
Further, since it is composed of a thin film, the size in the height direction can be reduced. Moreover, since the predetermined position of the microstrip line is in an arc shape of approximately 90 degrees parallel to the resonator, the length of the arc shape is 1/4 of the circumferential length of the resonator.
Therefore, the resonance condition between the resonator and the microstrip Iran appears more strongly.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of an oscillator circuit according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1A shows an example of the overall configuration of a monolithic MIC (MMIC) formed by incorporating an oscillator circuit according to an embodiment of the present invention into a microwave circuit. This circuit constitutes a down converter circuit, and as shown in FIG.
Various elements are arranged on the aAs substrate 1. That is, the RF amplifier 2 is arranged at the end of the signal input side, the output side of the RF amplifier 2 is connected to one input side of the mixer 3, and the output side of the mixer 3 includes the preamplifier 4 and It is connected to an intermediate frequency amplifier (IF amplifier) 5 including a main amplifier 5. Then, on the other input side of the mixer 3,
A local oscillator circuit 7 according to the present invention is connected. The above elements are connected by a microstrip line 8.

The local oscillation circuit 7 is an MMI having an FET.
The C oscillator 9 and a resonator 10 connected to stabilize the oscillation frequency of the oscillator 9 are provided. The oscillator 9 has a drain of the FET 11 and a bias resistor 12 and a bypass capacitor 13 as shown in the equivalent circuit of FIG.
Via the bias resistor 14 to the power supply voltage Vcc and also to the T-type output matching circuit 15. A feedback circuit including the resonator 10 is inserted between the drain and the gate. By properly setting the installation position of the resonator 10 (distance from the FET), feedback is applied only at the resonance frequency, and stable oscillation can be obtained.

In this example, the resonator 10 is formed in a ring shape, and is arranged close to a predetermined position of the microstrip line 16 forming the feedback loop at a distance of several μm to several tens of μm. Further, the resonator 10 is formed by depositing a high temperature superconducting material. And
As the high temperature superconducting material, for example, yttrium-based (YBCO) or niobium-based material is used.

Furthermore, the microstrip line 1
6 is a circular arc-shaped portion close to the resonator 10. As shown in an enlarged view in FIG. 1B, the arc-shaped portion 16a has the same center as the resonator 10, and the central angle of the arc is 90 degrees. Thereby, the arc-shaped portion 16a
Will be wired in parallel along the outer peripheral edge of the resonator 10, and the length of the arcuate portion 16a will be one fourth of the circumferential length of the resonator 10.

The microstrip line 16 is also provided.
Also, the characteristics are better when formed by using a high temperature superconducting material, but such a material is not always necessary. In this example, it is formed by depositing gold having a low resistance.

Reference numeral 17 in FIG. 1 is a bias adjusting resistor, reference numeral 18 in FIG. 2 is a feedback capacitance between the drain and ground of the FET 11, and reference numeral 19 is an FET.
11 is a bypass capacitor inserted between the source of 11 and the ground.

FIG. 3 shows the characteristic results of the oscillation circuit when a signal is input from the non-reflection end side of the microstrip line 16 forming the feedback loop. However, in this experimental result, the shape of the microstrip line 16 does not have the arcuate portion 16a as described above, but is measured linearly as shown in FIG.

FIG. 3A shows that the frequency of the input signal is 2 GHz.
It shows the reflection loss when changing from z to 18 GHz, that is, the change of S11 which is one of the S parameters. In the figure, the vertical axis represents loss [dB], which is 1
The span is 5 dB. And, as is clear from the figure, the loss at the resonance frequency (10.32 GHz) is −
It is a very small value of 2.47 dB. As a result, it is possible to efficiently oscillate in a stable state. Then, as can be seen from this result, when the predetermined portion of the microstrip line is formed in an arc shape as in the present invention, the coupling such as resonance between the microstrip line and the resonator becomes stronger, so that the loss at the resonance frequency is reduced. Is approximately −
It becomes about 1.5 to -1.0 dB, and the performance is further improved.

Similarly, FIG. 3 (B) shows the frequency characteristic of S21 indicating the forward transmission coefficient which is one of the S parameters, which was similarly tested by using a linear microstrip line. As shown in the figure, it can be seen that the resonance frequency sharply decreases. And even in this characteristic,
It can be inferred that the steepness can be obtained by using an arcuate microstrip line as in the present invention.

The present invention may be applied to various forms of the oscillation circuit composed of a hybrid MIC or an oscillation circuit composed of a monolithic MIC, and moreover, as in the above-mentioned embodiment, it is locally applied. It is needless to say that the present invention is not limited to the oscillator circuit and can be applied to various types of oscillator circuits.

[0019]

As described above, in the oscillation circuit according to the present invention, since the ring-shaped resonator is used as the resonator attached to the feedback circuit, the radiation loss is small and the performance is improved. Moreover,
Since such a resonator is formed of a superconductor thin film, the resonator has a surface resistance much lower than that of a normal conductor, a resonator having a high Q and steep characteristics, and the stability of the oscillation frequency can be improved. it can. Further, since the resonator is formed of a thin film by vapor deposition or other means like other microstrip lines, the size in the height direction can be reduced.

Moreover, since the predetermined position of the microstrip line is in the shape of an arc of approximately 90 degrees parallel to the resonator, the length of the arc is 1/4 of the circumferential length of the resonator.
Therefore, the resonance state between the resonator and the microstrip Iran appears more strongly, and it is possible to manufacture an oscillation circuit with less loss and good characteristics.

[Brief description of drawings]

FIG. 1A is a diagram showing a preferred embodiment of an oscillator circuit according to the present invention. (B) is an enlarged plan view showing a portion near the resonator.

FIG. 2 is an equivalent circuit diagram showing a main part thereof.

FIG. 3 is a graph showing frequency characteristics of S parameters of an oscillation circuit that demonstrates the effect of the present invention.

FIG. 4 is a diagram showing a main part of a circuit used in the experiment.

[Explanation of symbols]

 10 ... Resonator 11 ... FET 16 ... Microstrip line 16a ... Arc-shaped portion

Claims (1)

Claims: 1. A FET provided on a semi-insulating substrate,
A thin film ring-shaped resonator made of a superconducting material disposed in the vicinity of a microstrip line of feedback circuit wiring connected to the FET, and a portion of the microstrip line in the vicinity of the resonator is resonated. An oscillator circuit, which is formed in an arc shape of approximately 90 degrees parallel to the circumference of the container.