JP2002368539A - Voltage-controlled oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a voltage-controlled oscillator for enhancing loop gain and increasing the electric power of an oscillator output. SOLUTION: An FET 17 having a peak reflection gain at the oscillation frequency is connected to an FET 12 via a micro-strip line 16. Then the capacity of a variable capacity diode 20 is changed so as to change the oscillation frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator used in a transceiver system of a microwave or millimeter wave band or a radar system.

[0002]

2. Description of the Related Art FIG. 14 is a block diagram showing a conventional voltage controlled oscillator. In FIG. 14, 1 is an output terminal, 2 is a field effect transistor (hereinafter referred to as FET) which is an oscillation element having a negative resistance component, Reference numeral 3 denotes a resonator connected to the FET 2, 4 denotes a 90-degree inverter line, and 5 denotes a desired frequency 1.
/ 2 wavelength main resonator, 6 is inductor, 7 is FE
A variable capacitance diode for changing the oscillation frequency of T2, 8
Is a voltage control terminal of the variable capacitance diode 7.

Next, the operation will be described. The voltage-controlled oscillator creates a loop gain by connecting the resonator 3 to the FET 2 having a negative resistance component, and amplifies power by performing superposition of the loop in phase to perform oscillation operation. Do. A variable capacitance diode 7 is mounted on the resonator 3, and the DC voltage supplied to the variable capacitance diode 7 is controlled to change the capacitance of the variable capacitance diode 7, thereby changing the oscillation frequency of the FET 2.

[0005] Here, as shown in FIG. 15, the FET 2 and the resonator 3 are separated at a connection point, and the reflection on the resonator 3 side is S 1.
1. Assuming that the reflection on the FET2 side is S22, S11 is as shown in FIG.
As shown in FIG. 6, the amplitude has a loss at the center frequency fo. On the other hand, S22 is designed so as to have a gain at the center frequency fo, as shown in FIG. The sum of these is the loop gain, which has a gain at the center frequency fo as shown in FIG. As shown in FIG. 19, the phase of the loop satisfies the oscillation condition at the point where it becomes 0 degree (that is, the same phase), so that the center frequency fo becomes 0 degree by inserting an appropriate line length. Design.

[0005] These arrangements are described in A in 1998.
sia Pacific Microwave Con
TU3A-1, “AV-band”
MMIC VCO with a Sub-Reson
ator Coupledby a 90-degre
e inverter ".

[0006]

Since the conventional voltage-controlled oscillator is constructed as described above, the peak of the reflection gain is determined by the peak point of the reflection gain of the FET 2, but is supplied to the variable capacitance diode 7. Even if the DC voltage is changed to change the resonance frequency on the resonator 3 side, only the loop phase changes (the oscillation frequency changes) but the peak of the loop gain does not change. For this reason, the Q value of the resonator 3 is maximized at the time of the peak of the loop gain, but there is a problem that the Q value of the FET 2 is reduced except at the center frequency fo, and the desired phase noise is reduced. In addition, the loop gain cannot be increased due to the loss of the resonator 3, and if the DC voltage supplied to the variable capacitance diode 7 is changed, the loop gain is reduced and the power characteristic of the oscillation output is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain a voltage controlled oscillator that can increase the loop gain and increase the power of the oscillation output.

[0008]

According to the voltage controlled oscillator of the present invention, a resonance means having a peak reflection gain at an oscillation frequency is connected to the oscillation means, and a variable capacitance means is connected to the resonance means. The frequency is changed.

In a voltage controlled oscillator according to the present invention, a resonance means having a peak reflection gain at an oscillation frequency is connected to an oscillation means, and a variable capacitance means is connected to the oscillation means to change the oscillation frequency. It was done.

In a voltage controlled oscillator according to the present invention, a resonance means having a peak reflection gain at an oscillation frequency is connected to an oscillation means, and a variable capacitance means is connected to the oscillation means and the resonance means to change the oscillation frequency. It is intended to be.

In the voltage controlled oscillator according to the present invention, the resonance means is constituted by using a field effect transistor, and the variable capacitance means is connected to the source electrode of the field effect transistor.

In the voltage controlled oscillator according to the present invention, the resonance means is constituted by using a field effect transistor, and the variable capacitance means is connected to the drain electrode of the field effect transistor.

In the voltage controlled oscillator according to the present invention, the oscillating means is constituted by using a field effect transistor, and the variable capacitance means is connected to the source electrode of the field effect transistor.

In the voltage controlled oscillator according to the present invention, the resonance means is constituted by using the first field-effect transistor, and the oscillation means is constituted by using the second field-effect transistor. The variable capacitance means is connected to the source electrode of the effect transistor.

In the voltage controlled oscillator according to the present invention, the oscillation means and the resonance means are constituted by using active elements.

In the voltage controlled oscillator according to the present invention, the resonance means is constituted by using active elements, and the oscillation means is constituted by using active elements different from the active elements.

In the voltage controlled oscillator according to the present invention, a reflection circuit capable of handling from the fundamental wave to the (N-1) th harmonic is connected to the output terminal.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a configuration diagram showing a voltage controlled oscillator according to a first embodiment of the present invention. In the figure, reference numeral 11 denotes an output terminal, 12 denotes a field effect transistor (oscillation means) having a peak reflection gain at an oscillation frequency, Hereinafter, the field effect transistor 12 is referred to as an FET. 13
Is an inductor, 14 is an open stub, 15 is FET1
2 is a resonator connected.

Reference numeral 16 denotes a microstrip line designed so that the phase of the FET 12 and the phase of the resonator 15 are in phase. Reference numeral 17 is connected to the FET 12 via the microstrip line 16 and has a peak reflection gain at the oscillation frequency. This is a field-effect transistor (resonance means), and the field-effect transistor 17 is hereinafter referred to as an FET. 18
Is an open stub, 19 is an inductor, 20 is a variable capacitance diode for changing the oscillation frequency, 21 is an applied power supply for the variable capacitance diode 20, and 22 is a low-pass filter in which a desired oscillation frequency is a cutoff band. The variable capacitance diode 20, the applied power source 21 and the low-pass filter 22 constitute a variable capacitance means.

Next, the operation will be described. First, FET
The inductor 13 and the open stub 14 are designed such that the FET 12 has a reflection gain near the oscillation frequency.
The inductor 19 and the open stub 18 are designed so that 17 has a reflection gain near the oscillation frequency.
The microstrip line 16 is designed so that the phase of the FET 12 and the phase of the resonator 15 are the same.

The DC voltage supplied to the variable capacitance diode 20 is supplied from an applied power supply 21 and grounded through a low-pass filter 22. Since the low-pass filter 22 has a characteristic of blocking a desired oscillation frequency, the FET 12 can oscillate at a desired frequency. In addition,
By controlling the DC voltage supplied to the variable capacitance diode 20 to change the capacitance of the variable capacitance diode 20, F
The oscillation frequency of the ET 12 can be changed.

Here, the reflection gain when the resonator 15 is viewed from the boundary between the FET 12 and the resonator 15 is represented by S11,
Assuming that the reflection gain when looking at the 12 side is S22, FIGS.
An amplitude characteristic as shown in FIG. 7 is obtained. FIG. 5 shows the reflection gain S1 when the capacitance of the variable capacitance diode 20 is changed.
FIG. 6 shows the reflection gain S22 of the FET 12, which does not change even if the capacitance of the variable capacitance diode 20 is changed. FIG. 7 shows the sum of these values to calculate the loop gain.

As is apparent from a comparison between FIG. 7 and FIG. 18 of the conventional example, the loop gain according to the first embodiment is twice or more higher than the conventional loop gain, so that the power of the oscillation output is improved. Low phase noise can be achieved. In addition, since a plurality of peaks of the loop gain appear, the band can be widened.

As is clear from the above, the first embodiment
According to this, the FET 17 having the peak reflection gain at the oscillation frequency is connected to the F
Since it is connected to the ET 12 to change the oscillation frequency by changing the capacitance of the variable capacitance diode 20, there is an effect that the loop gain can be increased and the power of the oscillation output can be increased.

Embodiment 2 FIG. 2 is a configuration diagram showing a voltage controlled oscillator according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and a description thereof will not be repeated. 23 is a short stub.

In the first embodiment, the case where the variable capacitance diode 20 is connected to the source electrode of the FET 17 has been described. However, the variable capacitance diode 20 may be connected to the drain electrode of the FET 17. The same effect as that of No. 1 can be obtained. In addition, FET
When the variable capacitance diode 20 is connected to the drain electrode 17, the voltage of the variable capacitance diode 20 can be grounded through the short stub 23, so that there is an advantage that the low-pass filter 22 becomes unnecessary.

Embodiment 3 In the first embodiment, F
Although the case where the variable capacitance diode 20 is connected to the source electrode of the ET 17 has been described, as shown in FIG.
The variable capacitance diode 20 may be connected to the twelfth source electrode, and the same effect as in the first embodiment can be obtained.

Here, the reflection gain when viewing the resonator 15 side from the boundary between the FET 12 and the resonator 15 is represented by S11,
Assuming that the reflection gain when looking at the 12 side is S22, FIGS.
An amplitude characteristic as shown in FIG. 10 is obtained. Figure 8 shows FET
17 and the variable capacitance diode 20
There is no change even if the capacity is changed. FIG. 9 shows the behavior of the reflection gain S22 when the capacitance of the variable capacitance diode 20 is changed. FIG. 10 shows the result when the loop gain is calculated by adding these.

As is apparent from a comparison between FIG. 10 and FIG. 18 of the conventional example, the loop gain according to the third embodiment is twice or more higher than the conventional loop gain, so that the power of the oscillation output is improved. Low phase noise can be achieved. In addition, since a plurality of peaks of the loop gain appear, the band can be widened.

Embodiment 4 In the first embodiment, F
Although the variable capacitance diode 20 is connected to the source electrode of the ET 17, as shown in FIG.
The variable capacitance diode 20 may be connected to the source electrode of the FET 17 and the variable capacitance diode 20 may be connected to the source electrode of the FET 12, and the same effects as in the first embodiment can be obtained.

Here, the reflection gain when the resonator 15 is viewed from the boundary between the FET 12 and the resonator 15 is represented by S11,
Assuming that the reflection gain when looking at the side 12 is S22, FIG.
13 are obtained. FIG. 11 shows the behavior of the reflection gain S11 when the capacitance of the variable capacitance diode 20 is changed, and FIG.
The movement of the reflection gain S22 when the capacitance of 0 is changed is shown. FIG. 13 shows the sum of these values to calculate the loop gain.

As is apparent from a comparison between FIG. 13 and FIG. 18 of the conventional example, the loop gain according to the fourth embodiment is twice or more higher than the conventional loop gain, so that the power of the oscillation output is improved. Low phase noise can be achieved. In addition, since a plurality of peaks of the loop gain appear, the band can be widened. Since the change in the loop gain when the DC voltage supplied to the variable capacitance diode 20 is changed can be reduced, the voltage dependence of the output power and the phase noise can be reduced.

Embodiment 5 FIG. Instead of the FET 12 in the first to fourth embodiments, a bipolar transistor or H
The oscillator 15 may be formed by using an active element such as BT or HEMT, and the resonator 15 may be formed by using an active element such as a bipolar transistor or HBT or HEMT instead of the FET 17. ~
The same effect as that of No. 4 can be obtained.

Embodiment 6 FIG. In the fifth embodiment, F
Although an example using an active element instead of the ETs 12 and 17 has been described, an active element used instead of the FET 12 and an active element used instead of the FET 17 may be different. For example, an active element having a large reflection gain is applied to the active element used on the resonator 15 side, and an active element used on the oscillation element side is 1 /.
It is conceivable to apply an active element having low f noise. As a result, phase noise can be further reduced and oscillation power can be further improved as compared with the case where a single active element is used.

Embodiment 7 FIG. In the first to sixth embodiments, although not particularly mentioned, the reflection circuit capable of handling from the fundamental wave to the N-1 harmonic is connected to the output terminal 11 to output the N harmonic of the oscillation frequency. You may do so. Thereby, there is an effect that the oscillation frequency can be increased.

[0036]

As described above, according to the present invention, the resonance means having the peak reflection gain at the oscillation frequency is connected to the oscillation means, and the variable capacitance means is connected to the resonance means to reduce the oscillation frequency. Since the configuration is changed, the loop gain can be increased and the power of the oscillation output can be increased.

According to the present invention, the resonance means having a peak reflection gain at the oscillation frequency is connected to the oscillation means,
Since the variable capacitance means is connected to the oscillation means to change the oscillation frequency, there is an effect that the loop gain can be increased and the power of the oscillation output can be increased.

According to the present invention, the resonance means having the peak reflection gain at the oscillation frequency is connected to the oscillation means,
A variable capacitance means is connected to the oscillation means and the resonance means,
Since the configuration is such that the oscillation frequency is changed, there is an effect that the loop gain can be increased and the power of the oscillation output can be increased.

According to the present invention, since the resonance means is constituted by using the field effect transistor and the variable capacitance means is connected to the source electrode of the field effect transistor, the oscillation frequency can be easily changed. There is an effect that can be done.

According to the present invention, since the resonance means is constituted by using the field effect transistor and the variable capacitance means is connected to the drain electrode of the field effect transistor, the oscillation frequency can be easily changed. There is an effect that can be done.

According to the present invention, the oscillating means is formed by using the field effect transistor, and the variable capacitance means is connected to the source electrode of the field effect transistor. Therefore, the oscillation frequency can be easily changed. There is an effect that can be done.

According to the present invention, the resonance means is constituted by using the first field-effect transistor, and the oscillation means is constituted by using the second field-effect transistor. Since the variable capacitance means is connected to the source electrode, the oscillation frequency can be easily changed.

According to the present invention, since the oscillating means and the resonating means are constituted by using the active elements, the structure of the oscillating means and the resonating means can be simplified.

According to the present invention, the resonance means is constituted by using the active element, and the oscillation means is constituted by using the active element different from the active element, so that the phase noise can be reduced and the oscillation power can be reduced. There is an effect that improvement can be achieved.

According to the present invention, since the reflection circuit capable of handling from the fundamental wave to the N-1 harmonic is connected to the output terminal, there is an effect that the oscillation frequency can be increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a voltage controlled oscillator according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a voltage controlled oscillator according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a voltage controlled oscillator according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a voltage controlled oscillator according to a fourth embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a reflection gain S11.

FIG. 6 is an explanatory diagram showing a reflection gain S22.

FIG. 7 is an explanatory diagram showing a loop gain.

FIG. 8 is an explanatory diagram showing a reflection gain S11.

FIG. 9 is an explanatory diagram showing a reflection gain S22.

FIG. 10 is an explanatory diagram showing a loop gain.

FIG. 11 is an explanatory diagram showing a reflection gain S11.

FIG. 12 is an explanatory diagram showing a reflection gain S22.

FIG. 13 is an explanatory diagram showing a loop gain.

FIG. 14 is a configuration diagram showing a conventional voltage controlled oscillator.

FIG. 15 is an explanatory diagram showing an operation of a conventional voltage controlled oscillator.

FIG. 16 is an explanatory diagram showing a reflection gain S11.

FIG. 17 is an explanatory diagram showing a reflection gain S22.

FIG. 18 is an explanatory diagram showing a loop gain.

FIG. 19 is an explanatory diagram showing a loop phase.

[Explanation of symbols]

11 output terminal, 12 FET (oscillation means), 13 inductor, 14 open stub, 15 resonator, 16
Microstrip line, 17 FET (resonance means), 18 open stub, 19 inductor, 20
Variable capacitance diode (variable capacitance means), 21 applied power supply (variable capacitance means), 22 low-pass filter (variable capacitance means), 23 short stub.

Claims (10)

[Claims] An oscillation means having a peak reflection gain at an oscillation frequency, a resonance means connected to the oscillation means and having a peak reflection gain at the oscillation frequency,
A voltage-controlled oscillator connected to the resonance means and comprising a variable capacitance means for changing the oscillation frequency. 2. An oscillation means having a peak reflection gain at an oscillation frequency, a resonance means connected to the oscillation means and having a peak reflection gain at the oscillation frequency,
A voltage controlled oscillator comprising: a variable capacitance means connected to the oscillation means for changing the oscillation frequency. 3. An oscillating means having a peak reflection gain at an oscillation frequency, a resonance means connected to the oscillation means and having a peak reflection gain at the oscillation frequency,
A voltage controlled oscillator comprising: a variable capacitance means connected to the oscillation means and the resonance means for changing the oscillation frequency. 4. The voltage controlled oscillator according to claim 1, wherein the resonance means is constituted by using a field effect transistor, and a variable capacitance means is connected to a source electrode of the field effect transistor. 5. The voltage controlled oscillator according to claim 1, wherein the resonance means is formed using a field effect transistor, and a variable capacitance means is connected to a drain electrode of the field effect transistor. 6. The voltage controlled oscillator according to claim 2, wherein the oscillating means is formed using a field effect transistor, and a variable capacitance means is connected to a source electrode of the field effect transistor. 7. A resonating means is constituted by using a first field-effect transistor, and an oscillating means is constituted by using a second field-effect transistor, and a source electrode of the first and second field-effect transistors is provided. 4. The voltage controlled oscillator according to claim 3, wherein a variable capacitance means is connected. 8. The voltage controlled oscillator according to claim 1, wherein the oscillation means and the resonance means are constituted by using active elements. 9. The method according to claim 1, wherein the resonance means is formed using an active element, and the oscillation means is formed using an active element different from the active element. The voltage controlled oscillator according to the item. 10. The voltage controlled oscillator according to claim 1, wherein a reflection circuit capable of handling from the fundamental wave to the N-1 harmonic is connected to the output terminal. .