JPH11239012A - Resonator circuit and oscillator circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resonator circuit which has wide resonance frequency variable width and an oscillator circuit which has wide oscillation frequency variable width without increasing the phase angle change quantity of a variable capacitive element. SOLUTION: This circuit connects a line in which a variable impedance circuit is connected to a dielectric resonator so as to vary a resonance frequency by the impedance of the variable impedance circuit. In such a case, a capacitive element 6 which grounds one end, is connected to a line 2 and a transmission line 5' is provided as an inductance element between a variable capacitive element 4 having one end grounded and the line 2. This increases the susceptance change of an LC parallel resonator circuit due to the capacitance value change of the element 4 and expands the charge width of the resonance frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonator and an oscillator used in a high frequency band, particularly in a millimeter wave region.

[0002]

2. Description of the Related Art Hitherto, a dielectric resonator has been used in a voltage controlled oscillator (hereinafter referred to as a VCO), a filter, and the like used in a high frequency band in order to improve the phase noise characteristic and the frequency stability. ing.

In an apparatus using such a dielectric resonator, when the resonance frequency of the dielectric resonator is changed by a control signal, a line loaded with a capacitance (hereinafter simply referred to as a capacitance) is connected to the dielectric resonator. This is done by coupling to a resonator and changing its capacitance.

FIG. 11 shows a configuration example of a conventional VCO. In FIG. 11, reference numeral 1 denotes a dielectric resonator, and two coupling lines 2 and 3 coupled to the dielectric resonator 1 are arranged. The coupling line 3 is a band reflection coupling line (hereinafter referred to as “main line”), and a terminating resistor 8 is connected to one end. A negative resistance circuit is connected to the other end. The coupling line 2 is a frequency adjustment coupling line (hereinafter referred to as “sub-line”).
And one end is open, and the variable capacitance element 4 is connected to the other end.

The VCO depends on the distance from the negative resistance circuit connected to the main line 3 to the coupling position of the dielectric resonator 1 to the main line 3, the reflection phase of the negative resistance circuit, and the reflection phase of the resonance circuit. Oscillation at an oscillation frequency that satisfies the oscillation conditions determined by Further, the reflection phase of the resonance circuit changes depending on the load capacity of the sub-line 2 coupled to the dielectric resonator 1, and the load capacity changes depending on the capacitance value of the variable capacitance element 4. The oscillation frequency is controlled by voltage control.

[0006]

As described above, the frequency variable width of the VCO using the variable capacitance element includes the phase angle change amount of the variable capacitance element 4, the impedance of the sub-line 2, and the sub-line 2 and the dielectric resonator 1. Is proportional to the amount of binding. Therefore, in order to obtain a VCO having a wide frequency variable width, it is only necessary to use the variable capacitance element 4 having a large phase angle change amount or to increase the degree of coupling between the sub-line and the dielectric resonator. However, the coupling amount between the sub-line 2 and the dielectric resonator is limited by the coupling structure.
The impedance of the sub-line 2 is also limited by the shape of the line. Therefore, in order to increase the frequency variable width, it is necessary to use a variable capacitance element having a large phase angle variation.

However, the amount of change in the phase angle of the variable capacitance element is limited by the characteristics (physical property values) of the variable capacitance element and the parasitic components (series parasitic inductance and parallel parasitic capacitance) due to the package of the variable capacitance element. In this case, it was difficult to increase the amount of phase angle change of the variable capacitance element.

That is, generally, the phase angle φ of a variable capacitance element is expressed by the following equation.

Tan φ = 2ωC / (ω ² C ² -1) where ω = 2πf, f is the frequency, and C is the capacitance of the variable capacitance element. Therefore, when the capacitance value C of the variable capacitance element increases, the phase angle φ approaches 180 °, and the change in the phase angle decreases even when the capacitance change increases. On the other hand, the higher the frequency, the larger the susceptance of the variable capacitance element, and the smaller the susceptance change, the smaller the phase angle change. Therefore, as the frequency increases, a variable capacitance element having a smaller capacitance value is required, but there is a limit to the achievable capacitance value. Further, when the variable capacitance element is mounted on the dielectric plate, a parasitic inductance is generated between the variable capacitance element and the ground electrode, and the parasitic inductance also acts in a direction to reduce the phase angle change.

Due to the various factors described above, when an attempt is made to form a resonance circuit in a high frequency band, it is difficult to increase the change in the phase angle of the variable capacitance element, so that the variable width of the resonance frequency cannot be increased.

An object of the present invention is to provide a resonance circuit having a wide resonance frequency variable width without increasing a phase angle change amount of a variable capacitance element.

It is another object of the present invention to provide an oscillation circuit having a wide oscillation frequency variable width using a resonance circuit having a large resonance frequency change amount.

[0013]

According to the present invention, even if the change of the capacitance value (capacitance susceptance) of the variable capacitance element is small,
In order to make the phase angle change due to the susceptance change look large, a resonance system is introduced into the variable impedance circuit portion. According to the first aspect of the present invention, in a resonance circuit including a dielectric resonator, a line coupled to the dielectric resonator, and a variable impedance circuit connected to the line, the variable impedance circuit has one end. It is composed of a capacitance element connected to the line and having the other end grounded, a variable capacitance element having one end grounded, and an inductance element connected between the other end of the variable capacitance element and one end of the capacitance element. .

Thus, an LC parallel resonance circuit is obtained in which the inductance of the inductance element is L and the capacitance of the variable capacitance element is C, which is obtained by combining the variable capacitance element and the inductance element.
Therefore, the value of C is set so that the susceptance change of the variable impedance circuit portion becomes large with respect to the change of L near the resonance frequency of the LC parallel resonance circuit. Then, a slight change in the capacitance value of the variable capacitance element appears as a large phase angle change.

[0015] The inductance element may be constituted by a transmission line formed on a dielectric substrate.

The newly added capacitive element may be configured as a line (open stub) having one end connected to the line and the other end open.

Further, a variable capacitance element such as a varactor diode may be used as the capacitance element to be newly added.

According to a fifth aspect of the present invention, there is provided a dielectric resonator, wherein the change in phase angle is seen to be large when the change in susceptance of the variable impedance circuit is small. In a resonance circuit composed of a line coupled to a device and a variable impedance circuit connected to the line, the variable impedance circuit is
It comprises a capacitance element having one end connected to the line, a variable capacitance element having one end grounded, and a transmission line connected between the other end of the variable capacitance element and the other end of the capacitance element.

With this configuration, an LC series resonance circuit mainly including a variable capacitance element C and an inductance element L is configured. Therefore, the value of L is set so that the reactance change becomes large with respect to the change of C near the resonance frequency of the LC series resonance circuit. Then, a slight change in the capacitance value of the variable capacitance element appears as a large phase angle change.

As described above, a resonance circuit whose resonance frequency is greatly changed by the capacitance value of the variable capacitance element is obtained. In the case of configuring a resonance circuit device using the change in the resonance frequency of the resonance circuit, another line is provided as described in claim 6, which is coupled to the dielectric resonator and has one end grounded and the other end an output end. Just do it.

Further, when a voltage controlled oscillator or the like is configured, a negative resistance circuit is connected to the output terminal and an oscillation signal is output by the negative resistance circuit and the resonance circuit. An output unit is provided.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a resonance circuit according to a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing the structure of a resonance circuit.
(A) is a perspective view of the main part, and (B) is an exploded sectional view. In this figure, reference numeral 10 denotes a dielectric plate, an electrode 1 having circular electrode openings 13 and 14 on both main surfaces thereof.
1, 12 are provided. This structure allows the electrode opening 1
The portions 3 and 14 function as a TE010 mode dielectric resonator. A circuit board 15 in the form of a dielectric sheet provided with coupling lines and the like is laminated on the upper surface of the dielectric plate 10 constituting such a dielectric resonator in the drawing. The electrode 11 is also used as a ground electrode of the circuit board 15.

In FIG. 1A, reference numeral 1 denotes a dielectric resonator. Reference numerals 2 and 3 denote coupling lines respectively coupled to the dielectric resonator 1, and here, 2 is a sub line and 3 is a main line. A terminating resistor 8 is connected to one end of the main line 3. A variable impedance circuit 2 including a variable capacitance element 4, a capacitance element 6, and an inductance element
0.

FIG. 2 is a plan view showing the configuration of the variable impedance circuit. In this figure, reference numeral 4 denotes a variable capacitance element, which is connected between the ground electrode 7 connected to the ground electrode 11 through the through hole and one end of the sub-line 2. Further, a capacitance element 6 is connected between a predetermined position of the sub-line 2 and the ground electrode 7. The variable capacitance element 4 is, for example, a chip-shaped varactor diode, and is mounted between the end of the sub-line 2 and the ground electrode 7. The capacitance element 6 is, for example, a chip capacitor, and is mounted between the sub-line 2 and the ground electrode 7. Note that an interdigital capacitor or a capacitor formed of a microstrip line may be used instead of the chip capacitor.

FIG. 4 shows an equivalent circuit of the above resonance circuit. In FIG. 4, reference numeral 5 'denotes a transmission line from the connection point of the capacitive element 6 to the sub-line 2 to the variable capacitive element 4. One end 18 of the main line 3 is used as an output terminal.

FIG. 3 shows a change in phase angle due to a change in capacitance of the variable capacitance element on an admittance Smith chart.

If the relative permittivity of the dielectric plate 10 is 24, the thickness of the dielectric plate 10 is 0.76 mm, and the diameter of the electrode opening is 3.0 mm, the TE010 mode resonance occurs at approximately 30 GHz. A body resonator is obtained. Circuit board 1
As 5, a dielectric sheet having a relative dielectric constant of 3.5 can be used. As shown in FIG. 2, the transmission line 5 'from the connection point A of the capacitive element 6 to the sub-line 2 to the variable capacitive element 4 is used as an inductance element. Here, the length of the transmission line 5 ′ is a microstrip line of 1.2 mm, and the capacitance change of the variable capacitance element 4 is 0.2 pF to 0.2 μF.
2.0 pF. At this time, the admittance in the variable capacitance element changes from A to B in FIG. This corresponds to a change in the phase angle of -124 to -174 °. The admittance of the circuit as viewed from the point A to the side of the variable capacitance element changes from the point C to the point D in FIG. This results in a change of 170 to 120 ° in phase angle.
The scale of the susceptance axis at point C in FIG.
1.75. Here, the center of the chart is 1/50
Ω, that is, 20 mS, the susceptance of the circuit as viewed from the point A to the variable capacitance element side is −11 * 20 mS =
It changes from -220 mS to -1.75 * 20 mS = -35 mS.

Assuming that the capacitance of the capacitive element 6 connected in parallel to the point A shown in FIG. 2 is 0.1 pF, the admittance of the entire variable impedance circuit is 0.1 pF at points C and D in FIG. However, the point changes to a point moved clockwise on the equal conductance curve, that is, points E and F in FIG. This is a susceptance of -200mS to -16mS
Up to 169-76 ° in phase angle,
Original phase angle change when no capacitive element 6 is provided -124 to
It can be seen that the change width is larger than -174 °.
In other words, this means that the resonance frequency variable width of the resonance circuit has increased.

Instead of the transmission line 5 ', for example, 2
When an inductance element having an inductance of 50 pH is connected in series, a variable capacitance element of 0.2 pF to
A change of 2.0 pF corresponds to a change in phase angle of 164 to 96 °. Thus, substantially the same effect can be obtained whether the inductance element portion is a transmission line or an inductor.

Next, FIG. 5 shows the configuration of the main part of the resonance circuit according to the second embodiment. In the example shown in FIG.
The capacitor 6 is connected between the predetermined position and the ground electrode 7. In the example shown in FIG. 5, instead of such a capacitor having one end grounded, an open stub formed by a line having a predetermined length opened at one end is used. 9 is provided at a predetermined position on the sub-line 2. Assuming that the wavelength on the line is λ, an open stub shorter than λ / 4 usually indicates a capacitance, so the line length of the line 9 is determined so as to have a predetermined equivalent capacitance value within that range. For example, when a circuit board having a relative dielectric constant of 3.5 and a thickness of 0.3 mm is used and the length of the line 9 is set to 0.9 mm, the capacitance value is about 0.1 pF, which is different from that of the above embodiment. Similar effects can be obtained.

FIG. 6 is a diagram showing a configuration of a main part of a resonance circuit according to the third embodiment. The structure is the same as that shown in FIG. 2, but here, a variable capacitance element 6 ′ is connected between a predetermined position of the sub-line 2 and the ground electrode 7. Here, the variable capacitance element 4 is called a first variable capacitance element, and the variable capacitance element 6 'is called a second variable capacitance element.

In FIG. 6, when the first variable capacitance element 4 changes from the low capacitance value (CS) to the high capacitance value (CL), the circuit of the first variable capacitance element 4 viewed from the point A is viewed. susceptance varies between B _CS .about.B _CL, a relationship of B _CS <B _CL (where _{B CS, B CL <0)} . Further, since the second variable capacitance element 6 'is directly connected to the sub-line, it has a capacitive susceptance (B _CS2 , B _CL2 > 0), and the second variable capacitance element 6' has a low capacitance. By changing from the value (CS) to the high capacitance value (CL), the susceptance becomes
It changes between B _{CS2 and} B _CL2 (B _CS2 <B _CL2 ).

The susceptance taking into account both the first and the second is (B _CS +
B _CS2 ) and (B _CL + B _CL2 ), but when the second variable capacitance element 5 ′ has a low capacitance value, the susceptance of the variable impedance circuit due to the parallel connection of the second variable capacitance element 5 ′ The change is small, and when the second variable capacitance element 5 'has a high capacitance value, the susceptance change of the variable impedance circuit due to the connection of the second variable capacitance element 5' in parallel becomes large.

That is, B _CS corresponds to point C in FIG. 3, and B _CL corresponds to point D in FIG. On the other hand, since the position immediately adjacent to the second variable capacitance element 6 '(point A in FIG. 6) is used as a reference point, the susceptance change B of the second variable capacitance element 6'
_CS2 .about.B _CL2, in the first embodiment shown in FIG. 2, equal to admittance (susceptance) change of varactor diodes 4, B _CS2 corresponds to point A in FIG. 3, B
_CL2 corresponds to point B in FIG.

The sum of the above susceptances (B _CS + B _CS2 ) is (susceptance at point C) + (susceptance at point A) in FIG. 3, and is a large negative susceptance (−in FIG. 3).
10) and a small positive susceptance (+2 in FIG. 3), the value is -8, and the amount of movement from the point C is small. On the other hand, the sum of the above susceptances (B _CL + B
_CL2 ) is (susceptance at point D) + (susceptance at point B) in FIG. 3, and is a small negative susceptance (−
1.8) and a large positive susceptance (+20), the value is almost 18, and the sum is positive. This means that the point F shown in FIG. 3 further rotates clockwise and goes around the point B in the lower half area beyond the upper half area. Therefore,
In the example shown in FIG. 6, a larger change is obtained than the change at points E to F in FIG.

Next, as a fourth embodiment, an example of the configuration of an oscillation circuit will be described with reference to FIGS.

FIG. 7 is an equivalent circuit diagram of the oscillation circuit. In this oscillation circuit, a negative resistance circuit is connected to the output terminal 18 of the resonance circuit shown in FIG. 4 to constitute an oscillation circuit as a whole. That is, in FIG.
This is an FET having an AsHEMT structure, which is used as a negative resistance circuit, and is connected to one end of the main line 3 to constitute a band reflection type oscillation circuit. The oscillation frequency is the resonance frequency of the dielectric resonator 1, the dielectric resonator 1 and the main line 3
The oscillation signal is extracted from the output terminal 17 depending on the distance from the coupling position to the negative resistance circuit and the variable impedance circuit.

FIG. 8 shows the relationship between the control voltage applied to the variable capacitance element 4 and the oscillation frequency in the oscillation circuit shown in FIG. In the figure, N denotes A when the capacitance element 6 is not connected.
Indicates the case of connection. By connecting the capacitive element to the predetermined position of the sub line in this way,
The frequency variable width spreads about twice.

Next, FIG. 9 shows the configuration of a variable impedance circuit used in the resonance circuit according to the fifth embodiment. In each of the above-described embodiments, the capacitive element is provided between the predetermined position of the sub-line 2 and the ground electrode. In the example shown in FIG. 9, the capacitive element 6 is connected to one end of the sub-line 2. One end of the variable capacitance element 4 is grounded, and the other end of the variable capacitance element 4 and the other end of the capacitance element 6 are connected by a transmission line 5 '. That is, it can be said that the capacitance element 6 is connected to the sub-line 2 in series.

In FIG. 9, if the capacitance change of the variable capacitance element 4 is 0.2 pF to 2.0 pF, this is -1 in phase angle.
Corresponds to a change of 24-174 °. Assuming that the length of the transmission line 5 'is 1.6 mm and the phase angle of the circuit viewed from the point A changes from 6 to 50 [deg.] Due to a change in the capacitance value of the variable capacitance element 4, this is 1000 to 95 as reactance.
Corresponds to changes in Ω. Then, by connecting the capacitive element 6 of 0.1 pF in series to the point A, the reactance of the variable impedance circuit changes in the range of 950 to 42Ω. This corresponds to a change in the phase angle of 6 to 100 °, and it can be seen that the change width is larger than the original phase angle change of −124 to −174 °. As a result, the variable width of the resonance frequency can be increased.

FIG. 10 shows an equivalent circuit diagram of an oscillation circuit using the resonance circuit shown in FIG. As described above, the main line 3 is coupled to the dielectric resonator 1 together with the sub-line 2, one end of the main line 3 is terminated by the terminating resistor 8, and the FE is connected to the other end.
An oscillation circuit can be configured by connecting a negative resistance circuit based on T16.

[0043]

According to the first aspect of the present invention, when the capacitance of the variable capacitance element is C and the inductance of the inductance element is L near the resonance frequency of the LC parallel resonance circuit, the variable impedance changes with respect to the change of C. If the value of L is set so that the susceptance change of the circuit portion becomes large, a large change in the phase angle can be obtained by a slight change in the capacitance value of the variable capacitance element.

According to the second aspect of the present invention, the inductance element can be easily constituted by a transmission line formed on a dielectric substrate.

According to the third aspect of the present invention, the newly added capacitive element can be easily constituted by a transmission line formed on a dielectric substrate.

According to the fourth aspect of the present invention, the resonance frequency variable width can be made wider.

According to the fifth aspect of the present invention, the value of L is changed so that the reactance change becomes large with respect to the change of C around the resonance frequency of the LC series resonance circuit mainly including the variable capacitance element as C and the inductance element as L. If the value is set, a large change in the phase angle can be obtained by a slight change in the capacitance value of the variable capacitance element.

According to the sixth aspect of the present invention, there is provided a resonance circuit device using a resonance circuit whose resonance frequency varies greatly depending on the capacitance value of the variable capacitance element.

According to the seventh aspect of the present invention, a negative resistance circuit is connected to the output terminal, and an output section for outputting an oscillation signal by the negative resistance circuit and the resonance circuit is provided, so that the oscillation frequency can be varied. A wide oscillation circuit can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view and an exploded cross-sectional view illustrating a configuration of a resonance circuit according to a first embodiment.

FIG. 2 is a diagram showing a configuration of a variable impedance circuit portion in the resonance circuit.

FIG. 3 is a diagram showing an example of an admittance change due to the addition of a capacitive element;

FIG. 4 is an equivalent circuit diagram of a resonance circuit.

FIG. 5 is a configuration diagram of a variable impedance circuit portion in a resonance circuit according to a second embodiment.

FIG. 6 is a configuration diagram of a variable impedance circuit portion in a resonance circuit according to a third embodiment.

FIG. 7 is an equivalent circuit diagram of an oscillation circuit according to a fourth embodiment.

FIG. 8 is a diagram showing an example of an oscillation frequency change with respect to a control voltage of the oscillation circuit.

FIG. 9 is a configuration diagram of a variable impedance circuit portion in a resonance circuit according to a fifth embodiment.

FIG. 10 is an equivalent circuit diagram of an oscillation circuit using the resonance circuit.

FIG. 11 is an equivalent circuit diagram of a conventional oscillation circuit.

[Explanation of symbols]

 1-dielectric resonator 2-coupling line (sub-line) 3-coupling line (main line) 4-variable capacitance element (varactor diode) 5-inductance element 5'-transmission line 6-capacitance element 6'-variable capacitance element 7-ground electrode 8-terminating resistor 9-line (open stub) 10-dielectric plate 11,12-electrode 13,14-electrode opening 15-circuit board 16-FET 17,18-output terminal 20-variable impedance circuit

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yasuo Fujii 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Inside Murata Manufacturing Co., Ltd. (72) Kenichi Iio 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Stock Company Murata Manufacturing

Claims (7)

[Claims] 1. A resonance circuit comprising a dielectric resonator, a line coupled to the dielectric resonator, and a variable impedance circuit connected to the line, wherein the variable impedance circuit has one end connected to the line. , A capacitance element having the other end grounded, a variable capacitance element having one end grounded, and an inductance element connected between the other end of the variable capacitance element and one end of the capacitance element. Resonant circuit. 2. The resonance circuit according to claim 1, wherein said inductance element is constituted by a transmission line formed on a dielectric substrate. 3. The resonance circuit according to claim 1, wherein the capacitive element is configured as a line having one end connected to the line and the other end open. 4. The resonance circuit according to claim 1, wherein said capacitance element comprises a variable capacitance element. 5. A resonance circuit comprising a dielectric resonator, a line coupled to the dielectric resonator, and a variable impedance circuit connected to the line, wherein one end of the variable impedance circuit is connected to the line. A resonance circuit comprising: a capacitance element; a variable capacitance element having one end grounded; and a transmission line connected between the other end of the variable capacitance element and the other end of the capacitance element. 6. A resonance circuit according to claim 1, wherein one end is grounded and the other end is an output end, and another line different from said line coupled to said dielectric resonator is provided. A resonance circuit characterized by that. 7. An oscillation circuit, wherein a negative resistance circuit is connected to the output terminal according to claim 6, and an output section for outputting an oscillation signal from the negative resistance circuit and the resonance circuit is provided. .