JP4506094B2 - Voltage controlled oscillator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency voltage-controlled oscillator in the microwave band.
[0002]
[Prior art]
A conventional voltage-controlled oscillator in the microwave band is disclosed in Non-Patent Document 1, for example. The disclosed voltage controlled oscillator utilizes a field effect transistor. Specifically, a feedback circuit is provided just before the gate terminal of the field effect transistor is used as an input terminal, the source terminal is grounded, and the drain terminal to the output terminal. This feedback circuit is provided with a microstrip line that is connected to the drain terminal and has the same phase as the input side, and this microstrip line is connected to the input terminal. By providing the feedback circuit in the field effect transistor in this way, the noise generated at the gate terminal is output to the drain terminal, and is fed back by the feedback circuit to cause oscillation.
[0003]
[Non-Patent Document 1]
Hiroyuki Abe, etc., "A High-Power Microwave GaAs FET Oscillator", IEEE ISSCC Digest of Technical Papers, p.164-165; 1976
[0004]
[Problems to be solved by the invention]
In this conventional voltage controlled oscillator, the output from the drain terminal of the field effect transistor enters the feedback circuit side directly connected to the line by power distribution according to the impedance value of the output side line and the feedback circuit side line. There was a problem that power loss occurred and the output efficiency decreased.
[0005]
The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a voltage-controlled oscillator with low power loss and high output.
[0008]
[Means for Solving the Problems]
The voltage controlled oscillator according to the first aspect of the present invention is a field effect transistor having a source terminal grounded and a gate terminal connected to an input terminal, an input port connected to the drain terminal of the field effect transistor, and an output port serving as an output terminal A directional coupler having an isolation port open, and one end connected to the coupler port of the directional coupler, and the other end connected to the gate terminal of the field effect transistor. A microstrip line group formed by series connection, a plurality of varactor diodes having one end connected between each microstrip line in the microstrip line group and the other end grounded, and a gate of the field effect transistor A varactor diode having one end connected to a terminal and the other end grounded is provided.
[0009]
A voltage controlled oscillator according to the invention of claim 2 is a field effect transistor having a source terminal grounded and a gate terminal connected to an input terminal, an input port connected to the drain terminal of the field effect transistor, and an output port connected to an output terminal A directional coupler having an isolation port open, and one end connected to the coupler port of the directional coupler, and the other end connected to the gate terminal of the field effect transistor. A microstrip line group formed by series connection and a plurality of varactor diode pairs in which two varactor diodes are connected in series with opposite polarities, and one anode end is connected between each microstrip line in the microstrip line group. A plurality of varactor diode pairs each connected and having the other anode end grounded, and two varactor dies Connected in series over de polarity opposite, in which one of the anode terminal connected to the gate terminal of the field effect transistor, and a varactor diode pairs grounded and the other of the anode end.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
A voltage controlled oscillator according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the voltage controlled oscillator according to the first embodiment. In FIG. 1, 1 is an input terminal, 2 is a ground terminal, and 3 is an output terminal. 4 is a field effect transistor, 5 is a directional coupler, and 6 is a termination resistor. The gate terminal of the field effect transistor 4 is connected to the input terminal 1, the source terminal is connected to the ground terminal 2, and the drain terminal is connected to the input port of the directional coupler 5. The output port of the directional coupler 5 is connected to the output terminal 3, and the isolation port of the directional coupler 5 is grounded via the termination resistor 6. Next, 7 is a microstrip line, and 8 is a varactor diode. The coupler port of the directional coupler 5 is connected to one end of the microstrip line 7, and the other end of the microstrip line 7 is connected to the input terminal 1. A grounded varactor diode 8 is connected to the other end of the microstrip line 7.
[0011]
Next, the operation of the voltage controlled oscillator will be described. Noise is generated at the gate terminal of the field effect transistor 4 and is output to the drain terminal. The output from the drain terminal is indirectly coupled by the directional coupler 5 and input to the feedback circuit, that is, the microstrip line 7 from the coupler port. The line length of the microstrip line 7 is set so as to be in phase on the input side in terms of RF (the line length is assumed to be θ1). The varactor diode 8 is a variable capacitance diode, and functions as a variable capacitance capacitor whose capacitance changes depending on the applied voltage. Also, impedance matching is achieved by attaching a terminating resistor 6 to the isolation port of the directional coupler 5. In this manner, the drain output of the field effect transistor is coupled by the directional coupler 5 and fed back to the gate terminal via the microstrip line 7 to cause oscillation. In the indirect feedback loop using the directional coupler 5, the drain terminal output of the field effect transistor 4 passes most of the power to the output terminal 3 and is coupled by the directional coupler 5 to reduce the power returned ( Therefore, it is possible to obtain a voltage controlled oscillator with reduced power loss and good output efficiency.
[0012]
Embodiment 2. FIG.
A voltage controlled oscillator according to Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 2 is a block diagram showing the configuration of the voltage controlled oscillator according to the second embodiment. The voltage controlled oscillator in FIG. 2 is obtained by removing the termination resistor 6 as compared with the voltage controlled oscillator shown in FIG. The higher the microwave output is, the higher the termination resistance 6 is, the more the power is required and the larger the termination resistance 6 tends to be. Therefore, the size of the entire voltage controlled oscillator can be reduced by the configuration in which the termination resistor 6 connected to the isolation port is not provided. The configuration and operation for feeding back the output to the drain terminal of the field effect transistor in the second embodiment to the gate terminal are the same as in the first embodiment. Since the termination resistor 6 is not provided, the line length of the microstrip line 7 is set to θ2 different from θ1 in the first embodiment.
[0013]
Further, as shown in FIG. 3, a terminating resistor 8 surrounded by a broken line A is provided, the oscillation circuit is set in a non-oscillating state, and the bias of the field effect transistor 4 is set in this state. You may make it remove a part. By doing so, the bias setting of the field effect transistor 4 can be performed in a stable state, and an oscillation circuit can be formed after removing the portion indicated by the broken line A. 2 and 3, parts or components denoted by the same reference numerals as those in FIG. 1 indicate parts or parts equivalent or equivalent to those in FIG. 1. However, the line length of the microstrip line 7 in FIG. 1 is different from that in FIGS. 2 and 3.
[0014]
Embodiment 3 FIG.
A voltage controlled oscillator according to Embodiment 3 of the present invention will be described with reference to FIGS.
FIG. 4 is a block diagram showing the configuration of the voltage controlled oscillator according to the third embodiment. In FIG. 4, 9 is a plurality of microstrip lines, which form a line group. 10a to 10d are varactor diodes. From the output port of the directional coupler 5 toward the feedback circuit, a varactor diode 10a having the other end grounded is connected to a microstrip line 9 that is separated from the wavelength by about a quarter of the wavelength. A varactor diode 10b with the other end grounded is connected to the microstrip line 9 that is one distance away. From the position where the varactor diode 10b is connected to the microstrip line 9, the varactor diode 10c with the other end grounded is connected on the microstrip line 9 which is further about 1/4 of the wavelength toward the input terminal 1 side. Further, a varactor diode 10d having the other end grounded is connected to the microstrip line 9 that is about one quarter of the wavelength away. In FIG. 4, parts or parts denoted by the same reference numerals as those in FIG. 1 indicate parts or parts equivalent or equivalent to those in FIG. 1.
[0015]
In the voltage controlled oscillator shown in FIG. 4, the drain terminal output of the field effect transistor 4 is indirectly coupled by the directional coupler 5 to feed back the microstrip line 9 and input to the gate terminal of the field effect transistor 4. It oscillates. Here, in FIGS. 1 to 3 described in the first embodiment and the second embodiment, there is one varactor diode 8. However, in FIG. 4 described in the third embodiment, the varactor diode is used. Four 10 are used. Next, advantages of providing a plurality of varactor diodes will be described.
[0016]
FIGS. 5A and 5B are block diagrams showing a configuration in which one and three varactor diodes are provided on a microstrip line (feedback circuit). FIGS. 6A and 6B are schematic diagrams showing the relationship between the frequency and the phase in the voltage change corresponding to the block configurations of FIGS. 5A and 5B. . Since a feedback circuit using a plurality of varactor diodes has a wider variable capacitance than a circuit using a single varactor diode, the feedback circuit can be configured to respond to changes in voltage (feedback circuit and thus the DC voltage applied to the varactor diode). The change in electrical length can be increased. Comparing FIG. 6 (a) and FIG. 6 (b), it can be seen that the frequency range with respect to voltage change is expanded in FIG. 6 (b). Further, when looking at the amount of change in frequency depending on the phase when the voltage is changed, in FIG. 6A, the amount of change in frequency varies depending on the position of the phase. ) Shows that the difference in the amount of frequency change depending on the phase position is small. By increasing the number of varactor diodes in this way, the frequency tuning range due to voltage change can be widened.
[0017]
Embodiment 4 FIG.
A voltage controlled oscillator according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 7 is a block diagram showing the configuration of the voltage controlled oscillator according to the fourth embodiment. In FIG. 7, 11 a to 11 d are each formed by connecting two varactor diodes in series with opposite polarities, grounding the anode end as one end, and forming the anode end as the other end by the microstrip line 9. A pair of varactor diodes connected to a feedback circuit. Reference numerals 12a to 12d denote control voltage terminals connected between the two varactor diodes of each of the varactor diode pairs 11a to 11d. From the output port of the directional coupler 5 toward the feedback circuit, a varactor diode pair 11a having the other end grounded is connected to a microstrip line 9 that is separated from the wavelength by about a quarter of the wavelength. A varactor diode pair 11b whose other end is grounded is connected to the microstrip line 9 which is one distance apart. From the position where the varactor diode pair 11b is connected to the microstrip line 9, further toward the input terminal 1, the varactor diode pair 11c with the other end grounded is placed on the microstrip line 9 which is about a quarter of the wavelength away. Further, a varactor diode pair 11d having the other end grounded is connected to the microstrip line 9 which is separated by about a quarter of the wavelength. In FIG. 7, the parts or parts denoted by the same reference numerals as those in FIG. 4 indicate parts or parts equivalent or equivalent to those in FIG.
[0018]
Since the varactor diode pairs 11a to 11d are connected in series with opposite polarities, non-linear noise can be suppressed, and the power resistance can be increased by increasing the number of varactor diodes.
[0021]
【The invention's effect】
According to the first aspect of the present invention, a plurality of stages of microstrip lines are provided in series in the feedback circuit, and the varactor diode with the anode terminal grounded is connected between the microstrip lines. The tuning range can be expanded.
[0022]
According to the invention of claim 2 of the present invention, two varactor diodes are connected in series with opposite polarity in the feedback circuit, and the anode end is grounded and connected between the microstrip lines, thereby suppressing nonlinear noise. In addition, the withstand power can be increased by increasing the number of varactor diodes.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a voltage controlled oscillator according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a voltage controlled oscillator according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing another configuration of the voltage controlled oscillator according to the second embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a voltage controlled oscillator according to a third embodiment of the present invention.
FIG. 5 is a block diagram showing a configuration in which one and three varactor diodes are provided on a microstrip line.
FIG. 6 is a schematic diagram showing the relationship between frequency and phase in voltage change.
FIG. 7 is a block diagram showing a configuration of a voltage controlled oscillator according to a fourth embodiment of the present invention.
[Explanation of symbols]
4 Field Effect Transistor 5 Directional Coupler 6 Termination Resistor 7, 9 Microstrip Line 8, 10 Varactor Diode 11 Varactor Diode Pair

Claims (2)

  A field effect transistor in which the source terminal is grounded, the gate terminal is connected to the input terminal, and the input port is connected to the drain terminal of the field effect transistor, the output port is connected to the output terminal, and the isolation port is opened. A coupler, and a microstrip line group formed by a multi-stage series connection in which one end is connected to the coupler port of the directional coupler and the other end is connected to the gate terminal of the field effect transistor; One end is connected between each microstrip line in the microstrip line group, the other end is connected to the gate terminal of the field effect transistor, and the other end is connected to the plurality of varactor diodes having the other end grounded. A voltage-controlled oscillator comprising a grounded varactor diode.   A field effect transistor in which the source terminal is grounded, the gate terminal is connected to the input terminal, and the input port is connected to the drain terminal of the field effect transistor, the output port is connected to the output terminal, and the isolation port is opened. A coupler and a microstrip line group formed by a plurality of stages connected in series, one end connected to the coupler port of the directional coupler and the other end connected to the gate terminal of the field effect transistor; A plurality of varactor diode pairs in which a plurality of varactor diodes are connected in series with opposite polarities, one anode end being connected between each microstrip line in the microstrip line group, and the other anode end being grounded A pair of varactor diodes and two varactor diodes in series with opposite polarity, The de end connected to the gate terminal of the field effect transistor, a voltage controlled oscillator, characterized in that a varactor diode pairs grounded and the other of the anode end.

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