JPH01200804A - Voltage controlled type oscillator - Google Patents

Abstract

PURPOSE:To compensate the lowering of the Q value of a resonator due to the influence of the series resistance of a variable capacity element and to cause a phase noise characteristic to be satisfactory by providing a feedback loop composed of an amplifier and input side and output side coupling lines to the resonator coupled to an active element. CONSTITUTION:To the resonator composed of a resonator 7 to have an active element 1 and a resonance frequency variable means 6, the feedback loop composed of input side and output side coupling lines 8 and 13, input side and output side branching circuits 9 and 12, an amplifier 10 and a variable phase shifter 11 is provided. A variable phase shifter control signal generating means 14 controls a phase between the input and output of the feedback loop so as to make it in-phase by impressing a control signal to the variable phase shifter 11. An active filter to be used for an oscillator is composed of a main line 20, an input terminal 21, an output terminal 22, an inductive resonator 23, strip lines 24 and 25 and an amplifier 27. By the feedback loop composed of the amplifiers 10 and 27 and the line 25, the signal of the resonance frequency components of the resonator 7 is amplified and fed back. At such a time, a line length is selected so as to cause the lengths of the input and output coupling lines to be in-phase between the input and output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage controlled oscillator that has low noise and can have a wide frequency variable range.

[Conventional technology]

FIG. 6 shows an example of the configuration of a conventional voltage controlled oscillator.

In the figure, (a) shows an example of the configuration when a dielectric resonator is used as the resonator, and (b) shows an inductor and lumped element composed of a strip line and a varactor loaded at its tip. An example of a configuration using a series resonant circuit using a capacitor is shown.

In the figure, 51 is an FET which is an active element, 52 is a distributed constant line composed of a slip line, 53 is a varactor as a variable capacitance element, 54 is a terminating resistor, 55 is a dielectric resonator, and 56 is an output terminal. , 57 represent capacitors.

In the figure, if the impedance when looking at the FETl1tll from the a-a' plane is Zo, and the impedance on the load side when looking at the resonator side is ZL, then the oscillation condition is Z L +Z o = 0...
...(1).

Now, Z L = RL + J X L t Z o
= Ro + jX.

Then, the formula (1) is RL=RD (
2) X L = −X o ・・・・・・・・・
... It is expressed as (3).

The oscillation frequency is controlled by changing the bias of the variable capacitor 53 constituted by a varactor.

[Problem to be solved by the invention]

In the case of the conventional voltage controlled oscillator as mentioned above,
When a varactor is closely coupled to a resonator, the resistance component of the varactor deteriorates the Q of the resonator system, resulting in poor phase noise characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a voltage-controlled oscillator with good phase 2I sound characteristics by externally compensating for a decrease in the Q value of a resonator system due to the effect of the series resistance of a variable capacitance element.

(Means for Solving Problem 0) According to the present invention, the above-mentioned object is achieved by the means described in the claims.

FIG. 1 is a diagram showing the principle of the present invention, (a
) indicates a configuration corresponding to claim 1 described in the claims, 1 is an active element, 2 is a resonator, 3 is an input side coupling line, 4 is an amplifier, and 5 is an output side coupling line. ing.

Further, FIG. 1(b) is a diagram showing a vl configuration corresponding to claim 2 described in the claims, in which 1 is an active element,
6 is a resonant frequency variable means, 7 is a resonator, 8 is an input side coupling line, 9 is an input side branch circuit, 10 is an amplifier, 11 is a variable phase shifter, 12 is an output side branch circuit, 13 is an output side coupling line It represents.

[For production]

As shown in Fig. 1, the present invention connects the resonator system of an oscillator with a line that takes out the signal of the resonant frequency component, amplifies the signal, and then couples it back to the resonator and returns it in the same phase ( It is characterized by reducing the noise of the oscillator by increasing the Q value of the resonator equivalently by applying positive feedback. In particular, in the invention of claim 2, for example, The input/output coupled lines are branched by in-phase and 90-degree branch circuits, each branch signal is multiplied, and after passing through a low-pass filter, the signal controls the variable phase shifter inserted in the feedback loop. By doing so, even if the frequency is made variable (voltage controlled oscillator) using a varactor in the resonator system, for example, feedback is always applied in the same phase.

〔Example〕

The tjS2 diagram shows an example of the configuration of a resonator composed of an active filter used in the oscillator of the present invention.
0 is the main line consisting of a strip line, and 21
2 represents the main line, that is, the input terminal of the resonator, and 22 represents the output terminal.

Further, 23 represents a dielectric resonator, 24 and 25 represent a strip line coupled to the resonator, 27 represents an amplifier, and 10, 27, and 25 constitute a feedback loop. This feedback loop amplifies and feeds back the signal of the resonant frequency component of the resonator. At that time, if the length of the input/output coupling line is selected so that the input and output are in the same phase, the loss of the resonator will be compensated by this external feedback circuit, and the apparent Q value will increase ( Reference H, MaLsumu
ra and Y, Konishi,” An
active microwave filter w
ith dielectricresonator
” (see IEEE MTT-81979).

Further, FIG. 3 also shows an example of the configuration of an active filter based on the same principle, but in this case, the resonator is configured by a series resonant circuit consisting of a lumped constant inductor 28 and a capacitor 29. , for painting, during the day, by Hattori et al., 4 using bibolar transnosta
00 MHz Band 7-Tape Band Removal Filter "1986 Institute of Electronics, Information and Communication Engineers Semiconductor/Materials Division National Conference
219).

Figure 4 shows the characteristics of this type of active filter. When the feedback loop mentioned above is added, the filter characteristics as a band-rejection filter become steep, and the equivalent Q value of the resonator increases. I know it's going up.

FIG. 5 is a diagram showing the structure of an embodiment of the present invention, and shows an example of the structure of a voltage-controlled oscillator when each of the above types of active filters is used as a resonator.

In the figure, (a) shows a case where a dielectric resonator is used as a resonator (a resonator without a feedback loop), and (b) shows a strip line and a varactor 38 loaded at its tip. (c) shows a configuration in which a series resonant circuit including a lumped element inductor and a varactor 38 is used.

In each example, positive feedback is provided to the resonator by a feedback loop formed by a strip line 30, 31 connected to the resonator connected to each active element FET 37, an amplifier 27, and a variable phase shifter 36. This increases the Q value of the resonator.

And the strip line 30.31 coupled with the resonator
90 degree branch circuits 32 and in-phase branch circuits 33, respectively.
are provided, each branch output is multiplied by a multiplier 34, and the variable phase shifter 36 is controlled by a signal obtained by passing the output through a low-pass filter 35.

With this configuration, the lengths at the connection point of the resonator and the strip line 30, 31 and the branch circuit 32 or 33* are made equal, and the output of the branch circuit 32 including the variable phase shifter 36 and the amplifier 27 is connected to the branch circuit 33. If the path length is selected so that the phase difference θ between the input and output quantities on the path to the input is -90°<θ<90° in the operating frequency band, even when the resonant frequency of the resonator is made variable, At all frequencies, positive feedback is applied to the resonator and the Q value can be increased.

Therefore, a low noise voltage controlled oscillator with variable frequency can be constructed.

〔Effect of the invention〕

As explained above, since the oscillator according to the present invention can have a high equivalent Q value of the resonator system in all frequency ranges, it is possible to easily realize a voltage-controlled oscillator with good phase noise characteristics. There are possible advantages.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the basic configuration of the present invention, Fig. 2 is a diagram showing an example of the configuration of a resonator composed of seven tape filters, and Fig. 3 is a diagram showing the configuration of a resonator composed of an active filter. 4 is a diagram showing an example of the characteristics of an active filter, FIG. 5 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 6 is a diagram showing the configuration of a conventional voltage controlled oscillator. It is a figure which shows an example. 1...active element, 2.7...
Resonator, 3.8... Input side coupling line,
4. 10.27 ......Amplifier, 5.13
・・・・・・Output side coupling line, 6 ・・・・・・
・Resonant frequency variable means, 9...Input side branch circuit, 11.27.36...Variable phase shifter, 12...Output side branch circuit, 14
......Variable phase shifter control signal generation means, 20
, 24. 25.30. 31... Strip line, 21... Input terminal, 22...
・Output terminal, 23...Dielectric resonator,
28...Inductor, 29
・・・・・・ Capacitor, 32 ・・・・・・ 90
degree branch circuit, 33... common mode branch circuit, 34... multiplier, 35...
...Low pass filter, 37 ...-FE
T, 38 ... Varacta agent Patent attorney Takashi Honma (a) <b) An example of the configuration of Kyodoro which is composed of diagrams/diagrams showing the fundamental configuration of tree entanglement A. Anatomy diagrams, etc. 2 Diagram n Consisting of acte 4 bufuwa ref Resonance benefit horizontal admonition ear second 1 scale scale 3 Diagram active fi λ letter's M nature example Seat scale diagram graduation 4 eyes σσ Mizuryo (C) Figure 5 shows the example of Mizuarai Moe's example of senpai reprimand (Figure 5 is No. 2)

Claims (1)

[Claims] 1. An oscillator comprising an active element (1) and a resonator (2) coupled to the active element (1), the resonator (2) being coupled to the active element (1).
) for extracting the resonant frequency component, and an amplifier (4) for amplifying the resonant frequency component.
) and a feedback loop consisting of an output side coupling line (5). 2. An oscillator comprising an active element (1) and a resonator (7) coupled to the active element (1) and having a resonant frequency variable means (6), the oscillator being coupled to the resonator (7). an input side coupling line (8) for extracting the resonant frequency component, an input side branch circuit (9), an amplifier (10), a variable phase shifter (11), an output side branch circuit (12), The resonator (
7), and a feedback loop consisting of an output side coupling line (13) coupled to the input side branch circuit (13).
9) and means (14) for detecting the phase difference between the branch output of the output side branch circuit (12) and generating a signal for controlling the variable phase shifter (11); A voltage controlled oscillator characterized in that the input and output phases of the feedback loop are controlled to be in phase by applying voltage to a variable phase shifter (11).