JPH04145708A - Microwave oscillator - Google Patents

Abstract

PURPOSE:To miniaturize this oscillator by sharing at least a resistor element among plural resistor elements constituting an attenuator as a bias resistor of a source terminal of an oscillation FET. CONSTITUTION:A resistor element 1 is shared for a bias resistor at a source terminal 84 in a pi-type attenuator composed of a capacitive element 4 and resistor elements 1, 2, 3 connected to the source terminal 84 of an oscillator FET 81 via an output matching circuit 92 and a microstrip line 87. Thus, a high frequency element circuit required for connecting a bias resistor element to the circuit 92 is not required and the microwave oscillator is miniaturized. In this case, the capacitance of the element 4 is selected so as to be a sufficiently low impedance in comparison with the resistance of the elements 1-3 at the oscillating frequency and then the bias condition depends only on the element 1. Thus, the resistors 1-3 act as the pi-type attenuator with respect to a high frequency signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a microwave oscillator used in a local oscillator circuit of a wireless communication device, etc., and particularly relates to miniaturization of a microwave oscillator including a microstrip line. It is.

[Prior Art] FIG. 6 is a circuit diagram showing the configuration of a conventional microwave oscillator using a field effect transistor (FET) and a dielectric resonator. A drain terminal 82 of the FET 81 is grounded at high frequency by an open-ended microstrip line 85 having a length of about 1/4 wavelength of the oscillation frequency. A gate terminal 83 of the FET 81 is connected to one end of a microstrip line 86, and the other end of the line 86 is grounded via a resistive element 89. Dielectric resonator 88
is spatially coupled to the microstrip line 86 at a position a suitable distance away from the gate terminal 83 to determine the oscillation frequency. A source terminal 84 of the FET 81 is connected to a microstrip line 87 via an output matching circuit 92 made of a microstrip line. The microstrip line 87 has a resistor element 98°99° in order to reduce the influence of fluctuations in the load connected to the output terminal 101.
and a capacitor element 97 to an attenuator containing 100
connected via.

In the bias circuit of FET81, the drain terminal 8
2 to a terminal 9 via an inductor element 90 for a high frequency element.
1 to power supply voltage V. is applied, and the source terminal 84 is approximately 1
A high impedance microstrip line 93 having a length of /4 wavelengths and an open-ended microstrip line 9
It is grounded by a resistor element 96 through a high frequency element circuit 95 consisting of 4.

[Problems to be Solved by the Invention] However, in order to ground the source terminal 84 that is the output of the FET 81 using the bias resistor 96, the output matching circuit 92 and the bias resistor 96 must be connected to the high frequency It is necessary to connect via the element circuit 95. Since this high frequency element circuit 95 is constituted by two lines 93 and 94 having a length of about 1/4 wavelength, its shape is large, which is a cause of hindering miniaturization of the microwave oscillator.

In view of these problems in the prior art, it is an object of the present invention to provide a miniaturized microwave oscillator.

[Means for Solving the Problems] A microwave oscillator according to the present invention includes a microwave oscillation circuit including an oscillation transistor, a dielectric resonator, and a microstrip line, and an attenuator including a plurality of resistance elements. The present invention is characterized in that at least one of the resistive elements of the attenuator connected to the oscillation transistor by a microstrip line is shared as part of the bias circuit of the oscillation transistor.

[Function] In the microwave oscillator according to the present invention, at least one of the plurality of resistance elements constituting the attenuator is shared as the bias resistance of the source terminal of the FET, so that the source terminal and the bias resistance are connected. This eliminates the need for high-frequency element circuits, making it possible to downsize the microwave oscillator.

[Embodiments] FIGS. 1 to 5 are circuit diagrams showing microwave oscillators according to various embodiments of the present invention. In these figures, the same reference numerals as in FIG. 6 indicate the same components or corresponding parts as in the microwave oscillator of FIG.

Referring first to FIG. 1, a microwave oscillator according to a first embodiment of the invention is shown. In this first embodiment, an output matching circuit 92 is connected to the source terminal 84 of the FET 81.
and a resistance element l connected via a microstrip line 87, 2. Of the π-type attenuator constituted by capacitor element 4 and capacitor element 4, resistance element 1 is commonly used as a bias resistance of source terminal 84. Therefore, the bias resistance element 9 in the conventional example shown in FIG.
The high frequency element circuit 95 that was necessary for connecting the microwave oscillator 6 to the output matching circuit 92 is no longer necessary, and the microwave oscillator can be made smaller. At this time, as the capacitance of capacitor element 4, resistor elements 1.2 and 3
By selecting a value that provides a sufficiently low impedance compared to , the bias condition is determined only by the resistor element 1. And for high frequency signals, the resistive elements 1.2 and 3 act as a π-type attenuator.

FIG. 2 shows a microwave oscillator according to a second embodiment of the invention. In this second embodiment, the resistance element 1 of the π-type attenuator of the first embodiment is constructed by two resistance elements 10 and 11 connected in series and a bypass capacitor 14 connected in parallel to the resistance element 11. The configuration circuit has been changed. That is, in the second embodiment, a series circuit of two resistance elements 10 and 11 is used as a bias circuit. In this case, the resistance element 11 is bypassed for high frequency signals, and the resistance element 10
．． Since L2 and 13 act as π-type attenuators,
Bias circuit design becomes easier.

FIG. 3 shows a microwave oscillator according to a third embodiment of the invention. In this third embodiment, by selecting the capacitor element 23 to be of low impedance like the capacitor element 4 of the first embodiment, the series circuit of the two resistor elements 20 and 21 functions as a bias circuit, and the high frequency For the signal, resistive elements 20, 21 and 2
2 constitutes a T-type attenuator.

FIG. 4 shows a microwave oscillator according to a fourth embodiment of the invention. In this fourth embodiment, the resistor element 21 of the third embodiment is a circuit constituted by two resistor elements 31 and 32 connected in series and a bypass capacitor 34 connected in parallel to the resistor element 32. has been changed to.

That is, in the fourth embodiment, three resistance elements 30°31
and 32 series circuits are used as bias circuits. In this case, the resistive element 30
．． 31 and 33 act as T-type attenuators.

FIG. 5 shows a microwave oscillator according to a fifth embodiment of the invention. In this fifth embodiment, FET8
A dielectric resonator 42 is connected to both the microstrip line 40 whose one end is connected to the drain terminal 82 of 1 and the microstrip line 41 whose one end is connected to the gate terminal 83.
A feedback microwave oscillator is shown arranged to couple. In the fifth embodiment as well, the high frequency element circuit 95 as shown in FIG. 6 is not required by using the resistance element 43 as a bias resistor as in the first embodiment. Furthermore, for high frequency signals, the resistive elements 43, 44 and 45 act as π-type attenuators.

It is clear that attenuators similar to those shown in FIGS. 2 to 4 can also be used as the attenuators of the feedback microwave oscillation circuit shown in FIG.

[Effects of the Invention] As described above, according to the present invention, the microwave oscillator has the following effects:
At least one of the resistive elements in the attenuator connected to the oscillation transistor by a microstrip line is shared as part of the oscillation transistor's bias circuit, so no additional high-frequency blocking circuit is required for the bias circuit. becomes. Therefore, by slightly changing the configuration of the conventional attenuator, a miniaturized microwave oscillator can be provided easily and inexpensively.

[Brief explanation of the drawing]

1-5 are circuit diagrams illustrating microwave oscillators according to various embodiments of the present invention. FIG. 6 is a circuit diagram showing a conventional microwave oscillator. In the figure, 81 is an FET, 85, 86, 87, 93 and 94 are microstrip lines, 42 and 88 are dielectric resonators, and 92 is an output matching circuit. In each figure, the same reference numerals indicate the same contents or corresponding parts.

Claims (1)

[Claims] A microwave oscillator comprising a microwave oscillation circuit including an oscillation transistor, a dielectric resonator, and a microstrip line, and an attenuator including a plurality of resistance elements, the microwave oscillator being connected to the oscillation transistor by the microstrip line. A microwave oscillator characterized in that at least one of the resistive elements of the attenuator is shared as part of a bias circuit of the oscillation transistor.