JP3173593B2 - Microwave resonance circuit and microwave oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a microwave oscillator realized in the form of a microwave monolithic integrated circuit (MMIC) or the like, and more particularly to a configuration of a resonance circuit suitable for a microwave oscillator using an MMIC.

[0002]

2. Description of the Related Art FIG. 20 is a circuit diagram showing a first example of a conventional microwave oscillator. This conventional microwave oscillator uses a field effect transistor (hereinafter referred to as “FET”).
This is a series feedback type oscillator in which a feedback short-circuit stub 2 is connected to one source terminal. The gate terminal is connected to the gate bias circuit 3 via a parasitic oscillation prevention resistor 14 to connect D to the gate terminal.
A C bias is provided. A DC bias is supplied to the drain terminal by the drain bias circuit 4. Each of the bias circuits 3 and 4 includes a 波長 wavelength line 5, a capacitor 6, and a DC power supply 7. The oscillation output is taken out to the load resistor 10 via the output matching circuit 8. The output matching circuit 8 includes a transmission line 11 and an open stub 12 for matching.

FIG. 21 shows a second example of a conventional microwave oscillator.
FIG. 4 is a circuit diagram showing an example of the embodiment. This microwave oscillator is different from the conventional microwave oscillator shown in FIG. 20 in that a transmission line resonance circuit 9 constituted by a 波長 wavelength open end stub 25 is provided.
Is added. Examples of such an oscillator to which a transmission line resonator using a half-wavelength open-ended stub is added are described in the IEICE Spring Conference C-43 in 1994 or the IEICE C-44 in 1993. ing.

FIG. 22 shows a third conventional microwave oscillator.
FIG. 4 is a circuit diagram showing an example of the embodiment. This microwave oscillator is different from the conventional microwave oscillator shown in FIG. 20 in that a transmission line resonance circuit 9 having a 1/4 wavelength tip short-circuit stub 26 is provided.
Is added.

FIG. 23 shows a fourth example of a conventional microwave oscillator.
FIG. 4 is a circuit diagram showing an example of the embodiment. In this microwave oscillator, a resonance circuit 9 is configured by replacing a capacitor used for high-frequency grounding with a 波長 wavelength open stub 27 in the conventional microwave oscillator shown in FIG. Examples of such an oscillator to which a transmission line resonator using a 波長 wavelength open-ended stub is added are described in the IEICE Spring Conference C-73 in 1994 or the IEICE C-60 in 1992. ing.

FIG. 24 shows a fifth example of the conventional microwave oscillator.
FIG. 4 is a circuit diagram showing an example of the embodiment. This microwave oscillator is obtained by adding a resonance circuit 9 including a coupling transmission line 28 and a dielectric resonator 29 to the conventional microwave oscillator shown in FIG. An example of an oscillator using such a dielectric resonator is IEEE TRANSACTIONS ON MICROWAVE THEOR.
Y AND TECHNIQUES, VOL.MTT-31, p.312.

[0007]

In the first example of the conventional microwave oscillator shown in FIG. 20, since the circuit does not include an element having a steep frequency characteristic, the Q value of the circuit is small and the phase noise is low. There was a problem that was large.

On the other hand, in the example of the conventional microwave oscillator shown in FIGS. 21 to 23, the Q factor of the circuit is increased by adding a transmission line resonance circuit in which one end of the transmission line is opened or short-circuited. The aim is to reduce phase noise. Although these transmission line resonators can be realized simply and compactly with a planar circuit, there is a problem that the no-load Q value is not so large and a sufficient phase noise reduction effect cannot be obtained.

On the other hand, in the example of the conventional microwave oscillator shown in FIG. 24, a dielectric resonator 29 is connected to a coupling transmission line 28.
The phase noise is reduced by using a resonance circuit 9 that magnetically couples. Dielectric resonator has very large no-load Q
However, there is a problem that the circuit and the device are increased in size and the manufacturing cost is increased.

The present invention has been made in view of the above points, and has as its object to provide a small, low-cost microwave oscillator having excellent phase noise characteristics.

[0011]

In order to achieve the above object, a microwave oscillator according to the present invention has a (2n-1) / 4 wavelength (n = 1, 2,...) Determined by a certain phase constant β. Having a length smaller than the phase constant β, and having an open end stub having a phase constant smaller by an amount sufficiently smaller than the phase constant β, and having the same length as the open end stub, It is characterized by having a resonance circuit in which an open-end stub having a phase constant larger than the above-mentioned phase constant β by an amount sufficiently smaller than the above-mentioned phase constant β is connected in parallel.

The microwave oscillator according to the present invention has an n / 2 wavelength (n = 1, 2,...) For a certain phase constant β.
A tip short-circuit stub having a phase constant smaller than the phase constant β by a sufficiently small amount compared to the phase constant β, and having the same length as the tip short-circuit stub, It is characterized by having a resonance circuit in which a tip short-circuit stub having a phase constant larger than the phase constant β by a sufficiently small amount compared with the phase constant β is connected in parallel.

Further, the resonance circuit for a microwave oscillator according to the present invention is characterized in that the open-end stubs or the short-circuited stubs having different phase constants are realized by microstrip lines having different center line widths.

Further, the resonance circuit for a microwave oscillator according to the present invention is characterized in that the open-end stubs or the short-circuited stubs having different phase constants are realized by coplanar waveguides having different center line widths.

Further, in the resonance circuit for a microwave oscillator according to the present invention, the open-ended stub or the short-circuited stub having different phase constants are realized by coplanar waveguides having different lengths of the gap between the center line and the ground metal. It is characterized by doing.

Further, in the resonance circuit for a microwave oscillator according to the present invention, the open-ended stub or the short-circuited stub having different phase constants may be provided on a semiconductor or semi-insulating substrate under and around one of the stubs. Is realized by forming

Further, the resonance circuit for a microwave oscillator according to the present invention is characterized in that the open-ended stub or the short-circuited stub having different phase constants is provided with a projection on a semiconductor or semi-insulating substrate under and around one of the stubs. Is realized by forming

Further, in the resonance circuit for a microwave oscillator according to the present invention, the open-ended stub or the short-circuited stub having the different phase constants may be formed by recessing the stub under one of the stubs and the back surface of the semiconductor or semi-insulating substrate. Is realized by forming

Further, in the resonance circuit for a microwave oscillator according to the present invention, the open-end stub or the short-circuited stub having the different phase constants may be formed by projecting a lower portion of one of the stubs and a peripheral surface of a semiconductor or semi-insulating substrate. It is characterized by being realized by forming a part.

[0020]

FIG. 1 is a circuit diagram of a microwave oscillator according to a first embodiment of the present invention. The microwave oscillator according to the present embodiment is a series feedback type oscillator in which a feedback short-circuit stub 2 is connected to the source terminal of the FET 1. A DC bias is supplied to the gate terminal via the parasitic oscillation prevention resistor 14 by the gate bias circuit 3. A DC bias is supplied to the drain terminal by the drain bias circuit 4. The bias circuits 3 and 4
It comprises a / 4 wavelength line 5, a capacitor 6, and a DC power supply 7.

The oscillation output is taken out to a load resistor 10 via an output matching circuit 8 and a resonance circuit 9. The output matching circuit 8 includes a transmission line 11 and an open stub 12 for matching. The resonance circuit 9 is formed by connecting the open-end stubs 13a and 13b in parallel. The open-end stub 13a and the open-end stub 13b have a length of 1/4 wavelength determined by a certain phase constant β, and the phase constant of each stub changes before and after the above-mentioned β by an amount sufficiently smaller than β. Let me do it.

Next, the operation of the microwave oscillator according to the first embodiment of the present invention will be described with reference to FIGS.

FIG. 2 is a circuit diagram of a portion including the resonance circuit 9 and the load resistor 10 of the microwave oscillator shown in FIG. In the figure, Z _0i and γ _i (i = 1, 2) are the characteristic impedance and the propagation constant of the open stub 13a and the open stub 13b. R ₀ is a load resistance value. To write the impedance in anticipation of load resistance side from the transmission line and Z _L as shown in the figure, the impedance Z _i of the two-terminal circuit shown in FIG. 2 is represented by the following equation (1).

[0024]

(Equation 1) Here, for the sake of simplicity, assuming that the open-end stubs 13a and 13b and the transmission line have no loss and that the characteristic impedance of the transmission line is equal to the load resistance and Z ₀ = R ₀ , (1)
The equation is equation (2).

[0025]

(Equation 2) Here, R _0i and β _i (i = 1, 2) are the characteristic impedance and the phase constant of the open-end stubs 13a and 13b. Now, the open-end stub 13a and the open-end stub 1
The line length 3b of 3b is set to 波長 wavelength determined by a certain phase constant β. That is,

[0026]

(Equation 3) And Here, ω ₀ is the angular frequency of the fundamental wave, and L and C are the inductance and capacitance per unit length of the transmission line having the phase constant β. At this time, β _i l
If (i = 1, 2) is expressed as a function of the detuning angular frequency Δω from the fundamental frequency angular frequency ω ₀ , β _i1 is given by equation (4).

[0027]

(Equation 4)Where L_i, C_i(I = 1, 2) is the open-end stub 1
3a, Inductor per unit length of open end stub 13b
And capacitance. First, the two tips
The characteristic impedances of the open stubs 13a and 13b are equal.
I.e., R ₀₁= R₀₂Consider the case This place
The phase constant of the two open stubs

[0028]

(Equation 5) That is, when it is determined that β ₁ + β ₂ = β (6) or β ₁ = β−δβ, β ₂ = β + δβ (7), Δω = 0 for the fundamental wave.
Therefore, β _i1 (i = 1, 2) is symmetric with respect to π / 2.

Therefore, the value in the parentheses of the expression (2) becomes 0 due to the odd symmetry of the tangent function with respect to π / 2, and the resonance circuit does not affect the fundamental wave component under the lossless approximation. on the other hand,
For frequencies near the fundamental, Δω is not zero, so
β _i l _(i = 1,2) is not symmetrical with respect to [pi / 2. At this time, the value in parentheses in the expression (2) is not 0, and δβ is replaced by β
If the value is sufficiently small as compared with, the value has a sharply large value reflecting a sharp change in the vicinity of π / 2 of the tangent function.
Therefore, the two-terminal circuit shown in FIG. 2 has a steep frequency characteristic. In this case, in order to keep the characteristic impedances of the two open-end stubs equal, in addition to equation (5),

[0030]

(Equation 6) Needs to be satisfied.

Next, the two open-end stubs 13a, 13
Consider the case where the characteristic impedances of b are not equal. This
In the case of the characteristic impedance of two open stubs
R ₀₁, R₀₂And the phase constant β₁, Β₂The following
Equation (9)

[0032]

(Equation 7) Is satisfied, and (β−β ₁ ) and (β ₂ −β) are determined to be sufficiently smaller than β, whereby resonance characteristics at the fundamental wave frequency can be obtained by the same principle as in the above case.

In an actual design, since the loss of the transmission line must be considered, it is necessary to rewrite the above discussion into a form in which the loss is considered. The reason why the circuit shown in FIG. Is approximately understood as described above.

FIG. 3 is a graph showing a calculation result of the frequency dependence of the absolute value of the impedance Zi of the two-terminal circuit shown in FIG. In this calculation, the open end stub 1
3a, 13b, conductor loss and dielectric loss of the transmission line are taken into account. FIG. 21 shows a first example of a conventional microwave oscillator having no resonance circuit shown in FIG.
The same calculation results are also shown for the second example of the conventional microwave oscillator having the half-wavelength open-end stub resonator shown in FIG. From the graph, it can be seen that steep frequency characteristics can be obtained by using the resonance circuit of the present invention when no resonance circuit is used, as compared with the case where a half-wavelength open-end stub resonator is used.

FIG. 4 shows a microwave oscillator according to the first embodiment of the present invention, a conventional microwave oscillator having no resonance circuit shown in FIG. 20, and a half-wavelength open-end stub shown in FIG. FIG. 9 is a graph illustrating a comparison and calculation of phase noise of a conventional microwave oscillator having a resonator using a harmonic balance method. FIG. From the graph, it can be seen that while the suppression of the phase noise by the 波長 wavelength tip short-circuit stub is about 5 dB / Hz, the use of the resonance circuit of the present invention can reduce the phase noise by about 10 dB / Hz. Understand.

FIG. 5 is a circuit diagram of a microwave oscillator according to a second embodiment of the present invention. The microwave oscillator according to this embodiment is characterized in that a resonance circuit including an open-end stub 13a and an open-end stub 13b is connected to the gate terminal side of the FET.

The open-end stub 13a and the open-end stub 13b have a length of 1/4 wavelength determined by a certain phase constant β, and the phase constant changes before and after the above-mentioned β by an amount sufficiently smaller than β. Let me do it.

FIG. 6 is a circuit diagram of a microwave oscillator according to a third embodiment of the present invention. The microwave oscillator according to this embodiment is characterized by using a resonance circuit configured by connecting a tip short-circuit stub 36a and a tip short-circuit stub 36b in parallel. Tip short stub 36
a and 36b have a half wavelength length determined by a certain phase constant β, and the phase constant is changed before and after the above β by an amount sufficiently smaller than β.

Next, the operation of the microwave oscillator according to the third embodiment of the present invention will be described. FIG. 7 is a circuit diagram of a portion including the resonance circuit and the load resistance of the microwave oscillator shown in FIG. Z _0i and γ _i (i = 1, 2) in FIG.
Is the characteristic impedance and propagation constant of the tip short-circuit stubs 36a and 36b. R ₀ is a load resistance value. To write the impedance in anticipation of load resistance side from the transmission line and Z _L as shown in the figure, the impedance Zi of the two-terminal circuit shown in FIG. 6 is represented by the following equation (10).

[0040]

(Equation 8) Here, for the sake of simplicity, assuming that the tip short-circuit stubs 36a and 36b and the transmission line are lossless and that the characteristic impedance of the transmission line is equal to the load resistance and Z ₀ = R ₀ , (1)
The equation (0) becomes the following equation (11).

[0041]

(Equation 9) Here, R _0i and β _i (i = 1, 2) are the tip short-circuit stub 3
6a and 36b are characteristic impedances and phase constants. Now, the line length l of the tip short-circuit stubs 36a and 36b
At a half wavelength determined by a certain phase constant β. That is, the line length l is

[0042]

(Equation 10) It is expressed as

Here, ω ₀ is the angular frequency of the fundamental wave, L, C
Is the inductance and capacitance per unit length of the transmission line having the phase constant β. At this time, β _i
If l (i = 1, 2) is represented as a function of the detuning angular frequency Δω from the angular frequency ω ₀ of the fundamental wave, the following equation (13) is obtained.

[0044]

[Equation 11] Here, Li and Ci (i = 1, 2) are the tip short-circuit stub 3
6a and 36b show the inductance and capacitance per unit length.

First, consider the case where the characteristic impedance of the two tip short-circuit stubs is equal, that is, R ₀₁ = R ₀₂ . In this case, the phase constant of the two tip short-circuit stubs is

[0046]

(Equation 12) That is, when it is determined that β ₁ + β ₂ = β (15) or β ₁ = β−δβ, β ₂ = β + δβ (16), Δω = 0 for the fundamental wave.
Therefore, β _i1 (i = 1, 2) is symmetric with respect to π.

Therefore, due to the odd symmetry of the cotangent function with respect to π, the value in the parentheses of the equation (11) becomes 0, and the resonance circuit does not affect the fundamental wave component under the lossless approximation. On the other hand, for frequencies near the fundamental wave, Δω is not 0, so β
il (i = 1, 2) is not symmetric about π. At this time, if the value in parentheses in the expression (11) is not 0 but δβ is sufficiently smaller than β, the value of the cotangent function has a sharply large value reflecting a sharp change near π / 2. . Therefore, the two-terminal circuit shown in FIG. 7 has a steep frequency characteristic.

In this case, in order to keep the characteristic impedance of the two tip short-circuit stubs equal, in addition to equation (14),

[0049]

(Equation 13) Needs to be satisfied.

Next, consider the case where the characteristic impedances of the two tip short-circuit stubs are not equal. In this case, 2
Characteristic impedance _R 01 of the short-circuited end stubs, R
₀₂ and the phase constants β ₁ and β ₂ are determined so that the following expression (18) is satisfied and (β−β ₁ ) and (β ₂ −β) are sufficiently smaller than β. According to the same principle, resonance characteristics at the fundamental frequency can be obtained.

[0051]

[Equation 14] In an actual design, it is necessary to consider the loss of the transmission line, so the above discussion needs to be rewritten in consideration of the loss. However, the reason why the circuit shown in FIG. Is understood as described above.

FIG. 8 is a plan view showing an example in which the microwave oscillator according to the first embodiment of the present invention is realized in the form of an MMIC (microwave monolithic integrated circuit) using a microstrip line as a transmission line. is there. The monolithic microwave oscillator shown in FIG. 8 has a semiconductor substrate 15 having a ground conductor on the back surface, an FET 1, a feedback short-circuit stub 2, an epi-resistor 16, a quarter-wave line 5, a bias pad 17, an MIM capacitor 18, a via hole. 19, a transmission line 11, a matching open end stub 12, an open end stub 13a, an open end stub 13b, and an output pad 20. The FET 1 includes a gate electrode 21, a drain electrode 22, a source electrode 23, and an active layer 24.

By connecting the open-end stubs 13a and 13b in parallel, a resonance circuit is formed. The open-end stubs 13a and 13b have different line widths (w1 and w2 in the figure), and have a length of 1/4 wavelength determined by a certain phase constant β. By changing the line width, the phase constant is changed before and after the above-mentioned β by an amount sufficiently smaller than β.

FIG. 9 is a plan view showing an example in which the microwave oscillator according to the first embodiment of the present invention is realized in the form of an HIC (hybrid integrated circuit) using a microstrip line as a transmission line. The hybrid microwave oscillator shown in FIG.
1, FET chip 32, feedback short-circuit stub 2, thin-film resistor 34, 1/4 wavelength line 5, chip capacitor 33,
MIM capacitor 18, transmission line 11, open stub for matching 12, open stub 13a, open stub 1
3b, an output pad 20. FET chip 3
2 includes a gate electrode 21, a drain electrode 22, a source electrode 23, and an active layer 24.

By connecting the open-end stubs 13a and 13b in parallel, a resonance circuit is formed. The open-end stubs 13a and 13b have different line widths (w1, w1 in the figure).
w2), and has a length of １ ／ wavelength determined by a certain phase constant β. By changing the line width, the phase constant is changed before and after the above-mentioned β by an amount sufficiently smaller than β.

FIG. 10 shows an MMIC (microwave monolithic integrated circuit) in which a microwave oscillator according to the first embodiment of the present invention uses a coplanar waveguide as a transmission line.
FIG. 13 is a plan view showing an example of a case where the present invention is realized in the form of FIG. FIG.
The monolithic microwave oscillator shown in FIG. 0 includes a semiconductor substrate 15, an FET1, a feedback short-circuit stub 2, and an epi-resistor 1.
6, 1/4 wavelength line 5, bias pad 17, MIM capacitor 18, transmission line 11, matching open stub 1
2. The stub 13a includes an open stub 13a, an open stub 13b, and an output pad 20. FET 1 has a gate electrode 21, a drain electrode 22, a source electrode 23, an active layer 24.
And a ground metal 42.

A resonance circuit is formed by connecting the open-end stubs 13a and 13b in parallel. The open-end stubs 13a and 13b have different line widths (w1, w1 in the figure).
w2), and has a length of １ ／ wavelength determined by a certain phase constant β. By changing the line width, the phase constant is changed before and after the above-mentioned β by an amount sufficiently smaller than β.

FIG. 11 is a plan view showing another example in which the microwave oscillator according to the first embodiment of the present invention is realized in the form of an MMIC (microwave monolithic integrated circuit) using a coplanar waveguide as a transmission line. FIG.

Also in this embodiment, as in FIG.
A resonance circuit is formed by connecting the open-end stubs 13a and 13b in parallel. The open-end stubs 13a and 13b have a length of 1/4 wavelength determined by a certain phase constant β, and have different values of the gap between the center line and the ground plane (S1, S2 in the figure). By changing the gap, the phase constant is changed before and after the above β by an amount sufficiently smaller than β.

FIG. 12 is a plan view showing another example in which the microwave oscillator according to the first embodiment of the present invention is realized in the form of an MMIC (microwave monolithic integrated circuit) using a microstrip line as a transmission line. FIG. FIG. 13 is a sectional view taken along line AA of FIG.

A resonance circuit is formed by connecting the open ends stubs 13a and 13b in parallel. The open-end stub 13a and the open-end stub 13b have a certain phase constant β
の 長 wavelength length determined by Open end stub 1
A dielectric film 37 having a dielectric constant different from that of the semiconductor substrate 15 is deposited between the semiconductor substrate 15 and 3b to change the effective dielectric constant. Thus, the phase constants of the two open-end stubs are changed before and after the above-mentioned β by an amount sufficiently smaller than β.

FIG. 14 is a plan view showing another example in which the microwave oscillator according to the first embodiment of the present invention is realized in the form of an MMIC (microwave monolithic integrated circuit) using a microstrip line as a transmission line. FIG. FIG. 15 is a sectional view taken along line AA of FIG.

Open end stub 13a and open end stub 1
By connecting 3b in parallel, a resonance circuit is formed. The open-end stubs 13a and 13b have a length of 1/4 wavelength determined by a certain phase constant β. Semiconductor substrate 15
The surface projection 39 is formed by etching or the like at the portion where the open-end stub 13b is formed to change the substrate thickness. Thus, the phase constants of the two open-end stubs are changed before and after the above-mentioned β by an amount sufficiently smaller than β.

FIG. 16 is a plan view showing another example in which the microwave oscillator according to the first embodiment of the present invention is realized in the form of an MMIC (microwave monolithic integrated circuit) using a microstrip line as a transmission line. FIG. FIG. 17 is a sectional view taken along line AA of FIG.

Open end stub 13a and open end stub 1
By connecting 3b in parallel, a resonance circuit is formed. The open-end stubs 13a and 13b have a length of 1/4 wavelength determined by a certain phase constant β. Semiconductor substrate 15
A concave portion 40 is formed on the rear surface of the rear surface by etching or the like in a portion where the open-end stub 13b is formed to change the thickness of the substrate. Thus, the phase constants of the two open-end stubs are changed before and after the above-mentioned β by an amount sufficiently smaller than β.

FIG. 18 is a plan view showing another example in which the microwave oscillator according to the first embodiment of the present invention is realized in the form of an MMIC (microwave monolithic integrated circuit) using a microstrip line as a transmission line. FIG. FIG. 19 is a sectional view taken along line AA of FIG.

Open end stub 13a and open end stub 1
By connecting 3b in parallel, a resonance circuit is formed. The open-end stubs 13a and 13b have a length of 1/4 wavelength determined by a certain phase constant β. Semiconductor substrate 15
A rear surface projection 41 is formed by etching or the like on a portion of the back surface where the open-end stub 13b is formed to change the substrate thickness. Thus, the phase constants of the two open-end stubs are changed before and after the above-mentioned β by an amount sufficiently smaller than β.

In the above embodiment, F is used as a basic element.
Although ET is used, it goes without saying that the present invention can be applied to a microwave oscillator using any type of device such as a bipolar transistor and a diode.

In the above embodiments, only a specific type of series feedback type oscillator is shown as a circuit type of the oscillator. However, the present invention is applied to microwave oscillators of all kinds of circuit types including a parallel feedback type oscillator. It goes without saying that it can be applied.

In the above embodiments, a microstrip line and a coplanar waveguide are used as transmission lines. However, the present invention uses any type of transmission lines such as a slot line, a suspended strip line, and a strip line. Needless to say, the present invention can be applied to a microwave oscillator that has been used.

Embodiments of the present invention will be described below with reference to the drawings.

The microwave oscillator of the present invention shown in FIG. 1 is a series feedback type 60 GHz band oscillator in which a feedback short-circuit stub 2 is connected to the source terminal of a heterojunction FET 1 having a gate width of 100 μm and a gate length of 0.15 μm. It is.
The feedback short-circuit stub 2 has a characteristic impedance of 50
Ω, and the line length is 450 μm.

The gate terminal is connected to a gate bias circuit 3 through a resistor 14 for preventing parasitic oscillation of 100 Ω.
A bias is provided. A DC bias is supplied to the drain terminal by the drain bias circuit 4. Each of the bias circuits 3 and 4 includes a 波長 wavelength line 5, a capacitor 6 having a capacitance of 1 pF, and a DC power supply 7. A DC voltage of -0.5 V is applied to the gate and a DC voltage of 4 V is applied to the drain.

The oscillation output is taken out to a 50 Ω load resistor 10 via an output matching circuit 8 and a resonance circuit 9. The output matching circuit 8 includes a transmission line 11 and an open stub 12 for matching. The resonance circuit 9 includes an open-end stub 13a and an open-end stub 13b. The open-end stubs 13a and 13b have a length of 436 μm at a quarter wavelength determined by a phase constant β = 3.6 rad / mm at 60 GHz, and the phase constants at 60 GHz are 3.2 rad / mm and 4.0 rad, respectively. / M
m.

In the microwave oscillator of the present invention shown in FIG. 5, the phase constant β at 60 GHz is β = 3.6 rad / m
has a length of 436 μm which is determined by
The phase constant at 3.2 Hz is 3.2 rad / m
m, 4.0 rad / mm, open end stub 13a
And a resonance circuit composed of the open-end stub 13b is connected to the gate terminal side of the heterojunction FET1.

The microwave oscillator according to the present invention shown in FIG. 6 has a phase constant β = 3.6 rad / m at 60 GHz.
has a length of 872 μm which is determined by
The phase constant at 3.2 Hz is 3.2 rad / m
m, 4.0 rad / mm
And a resonance circuit composed of a tip short-circuit stub 36b.

The monolithic microwave oscillator shown in FIG. 8 has a ground conductor made of
A semiconductor substrate 15 made of GaAs having a thickness of 0 μm, a heterojunction FET 1, a feedback short-circuit stub 2 made of gold having a thickness of 2 μm and a width of 30 μm, GaAs and A doped with Si
Epi-resistance 16 made of u / Ge / Ni / Au ohmic metal, 1/4 wavelength line made of 2 μm thick gold 5, 2 μm
Bias pad 17, made of thick gold, 1000 S thick
MIM capacitors 18 and 30 using iNx film as dielectric film
A transmission line 11 made of gold having a thickness of 30 μm and having a thickness of 2 μm, a matching open stub 12 made of gold having a thickness of 30 μm and having a thickness of 2 μm, and an open stub 13 a made of gold having a thickness of 2 μm and having a thickness of 2 μm An open-end stub 13b made of gold is constituted by an output pad 20 made of 2 μm thick gold.

The heterojunction FET 1 has a gate width of 100 μm.
m, gate electrode 2 made of Al with a gate length of 0.15 μm
1. Drain electrode 22 and source electrode 23 made of Au / Ge / Ni / Au ohmic metal, active layer 24 made of AlGaAs electron supply layer, InGaAs channel layer, etc.
It is composed of The line length of the open end stub 13a and the open end stub 13b is 436 μm. The line width of the open end stub 13a is w1 = 15 μm, and the line width of the open end stub 13b is w2 = 40 μm.

The hybrid microwave oscillator shown in FIG. 9 comprises a metal block 30 made of 5 mm thick copper plated with gold and an insulating substrate 3 made of 100 μm thick alumina.
1. a 40 μm thick GaAs FET chip 32;
Feedback short-circuit stub 2 made of 2 μm gold, thin film resistor 34, １ ／ wavelength line 5 made of 2 μm gold, chip capacitor 33, MIM capacitor 18, transmission line 11 made of 2 μm gold, matching Open end stub 12,
It comprises a stub 13a, a stub 13b, and an output pad 20.

The FET chip 32 includes a gate electrode 21, a drain electrode 22, a source electrode 23, and an active layer 24. The insulating substrate 31, the FET chip 32, and the chip capacitor 33 are fixed on the metal block 30 with a material such as AuSn, and are electrically connected to each other by bonding wires 35 made of gold having a diameter of about 10 μm. The line length of the open-end stub 13a and the open-end stub 13b is 453 μm. The line width of the open end stub 13a is w1 = 40 μm, and the open end stub 1
The line width of 3b is w2 = 90 μm.

The monolithic microwave oscillator shown in FIG. 10 is a semiconductor substrate 1 made of GaAs having a thickness of 600 μm.
5. Heterojunction FET1, 2 μm thick feedback tip short-circuiting stub 2, Si-doped GaAs and A
Epi-resistance 16 made of u / Ge / Ni / Au ohmic metal, 1/4 wavelength line made of 2 μm thick gold 5, 2 μm
Bias pad 17, made of thick gold, 1000A thick S
MIM capacitor 18, 2μ using iNx film as dielectric film
a transmission line 11 made of gold having a thickness of 30 m and a thickness of 30 m;
An open-end stub 13 a made of 2 μm-thick gold and an open-end stub 13 b made of 2 μm-thick gold are formed of an output pad 20 made of 2 μm-thick gold.

The FET 1 has a gate electrode 21 made of Al having a gate width of 100 μm, a gate length of 0.15 μm, and an Au /
Drain electrode 22 and source electrode 23 made of Ge / Ni / Au ohmic metal, AlGaAs electron supply layer, I
An active layer 24 made of an nGaAs channel layer or the like and a ground metal 39 made of gold having a thickness of 2 μm. The line length of the open end stub 13a and the open end stub 13b is 440.
μm. The center line width of the open end stub 13a is w1
= 15 μm, the center line width of the open end stub 13b is w2
= 40 μm. The gap between the center lines of the open-end stubs 13a and 13b and the ground metal 42 is 20 μm.

In the monolithic microwave oscillator shown in FIG. 11, the open end stub 13a and the open end stub 13b each have a line length and a center line width of 440 μm.
m, 30 μm. The gap between the center line of the open end stub 13a and the ground metal is S1 = 10 μm, and the gap between the center line of the open end stub 13b and the ground metal is S2 =
40 μm.

In the monolithic microwave oscillator shown in FIG. 12, an open-end stub 13b made of Au having a thickness of 2 μm is used.
A dielectric film 37 made of 2.5 μm thick SiO 2 is deposited between the semiconductor substrate 15 made of GaAs and 40 μm thick. The line length and line width of the open-end stub 13a and the open-end stub 13b are 445 μm and 30 respectively.
μm.

In the monolithic microwave oscillator shown in FIG. 14, a semiconductor substrate 15 made of GaAs having a thickness of 40 μm is used.
Open-end stub 13 of 2 μm thick Au on the surface of
A surface protrusion 39 having a thickness of 4 μm is formed by etching or the like at the portion where b is to be formed.

In the monolithic microwave oscillator shown in FIG. 16, a semiconductor substrate 15 made of GaAs having a thickness of 40 μm is used.
Open stub 13 made of 2 μm thick Au on the back surface of
In the portion where b is to be formed, a back surface concave portion 40 having a depth of 10 μm is formed by etching or the like.

In the monolithic microwave oscillator shown in FIG. 18, a semiconductor substrate 15 made of GaAs having a thickness of 40 μm is used.
Open stub 13 made of 2 μm thick Au on the back surface of
On the portion where b is to be formed, a 5 μm-thick rear projection 41 is formed by etching or the like.

[0087]

According to the present invention, a certain phase constant β determines (2
an open-end stub having a length of n-1) / 4 wavelength and having a phase constant smaller than the phase constant β by a sufficiently small amount as compared with the phase constant β; Since a resonance circuit having the same length and having an open end stub having a phase constant larger than the phase constant β by a sufficiently small amount compared to the phase constant β is used in parallel, a small size is used. Thus, a microwave oscillator having low phase noise characteristics can be realized.

Further, the present invention has a length of n / 2 wavelength determined by a certain phase constant β, and a phase constant smaller than the above phase constant β by an amount sufficiently smaller than the above phase constant β. Having a tip stub having the same length as the tip open stub, and having a phase constant β
Since a resonance circuit is used in which an open-end stub having a phase constant that is sufficiently smaller than that of an open-end stub is connected in parallel, a small-sized microwave oscillator having low phase noise characteristics can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for explaining a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a resonance circuit according to the first embodiment of the present invention.

FIG. 3 is a graph for explaining resonance characteristics according to the first embodiment of the present invention.

FIG. 4 is a graph for explaining a phase noise characteristic according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram for explaining a second embodiment of the present invention.

FIG. 6 is a circuit diagram for explaining a third embodiment of the present invention.

FIG. 7 is a diagram for explaining a resonance circuit according to a third embodiment of the present invention.

FIG. 8 is a plan view showing an example in which the first embodiment of the present invention is configured by a microstrip line.

FIG. 9 is a plan view showing an example in which the first embodiment of the present invention is configured by a hybrid integrated circuit using a microstrip line as a transmission line.

FIG. 10 is a plan view showing an example in which the first embodiment of the present invention is configured by a coplanar waveguide.

FIG. 11 is a plan view showing another example in which the first embodiment of the present invention is configured by a coplanar waveguide.

FIG. 12 is a plan view showing another example in which the first embodiment of the present invention is constituted by microstrip lines.

FIG. 13 is a cross-sectional view of FIG. 12 taken along the line AA.

FIG. 14 is a plan view showing another example in which the first embodiment of the present invention is configured by a microstrip line.

FIG. 15 is a cross-sectional view of FIG. 14 taken along line AA.

FIG. 16 is a plan view showing another example in which the first embodiment of the present invention is constituted by microstrip lines.

FIG. 17 is a cross-sectional view of FIG. 16 taken along line AA.

FIG. 18 is a plan view showing another example in which the first embodiment of the present invention is constituted by microstrip lines.

FIG. 19 is a cross-sectional view of FIG. 18 taken along line AA.

FIG. 20 is a circuit diagram illustrating a conventional microwave oscillator.

FIG. 21 is a circuit diagram for explaining a conventional microwave oscillator to which a half-wavelength open-end stub resonator is added.

FIG. 22 is a circuit diagram for explaining a conventional microwave oscillator to which a 1 / wavelength tip short-circuit stub resonator is added.

FIG. 23 is a circuit diagram for explaining a conventional microwave oscillator to which a 波長 wavelength open end stub resonator is added.

FIG. 24 is a circuit diagram illustrating a microwave oscillator loaded with a conventional dielectric resonator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Field effect transistor (FET) 2 Feedback short-circuit stub 3 Gate bias circuit 4 Drain bias circuit 5 1/4 wavelength line 6 Capacitor 7 DC power supply 8 Output matching circuit 9 Resonance circuit 10 Load resistance 11 Transmission line 12 Opening tip for matching Stubs 13a, 13b Open-end stub 14 Parasitic oscillation preventing resistor 15 Semiconductor substrate 16 Epi-resistance 17 Bias pad 18 MIM capacitor 19 Via hole 20 Output pad 21 Gate electrode 22 Drain electrode 23 Source electrode 24 Active layer 25 1/2 wavelength open end Stub 26 1/4 wavelength tip short-circuit stub 27 1/4 wavelength tip open stub 28 Coupling transmission line 29 Dielectric resonator 30 Metal block 31 Insulating substrate 32 FET chip 33 Chip capacitor 34 Thin film resistor 35 Bonding wire 36a, 36b leading-end short stub 37 ground metal 38 dielectric film 39 surface protrusions 40 back surface recess 41 rear surface protrusion 42 ground metal

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2000-114870 (JP, A) JP-A-62-23501 (JP, A) JP-A-3-73602 (JP, A) 1990 Society, C-2-3, p32 IEICE Fall 1988, C-351, pC-1-233 IEICE Transactions on Science Vol. J77-CINO. 11 NOVEMBER 1994, pp 633-639 (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01P 7/08 H01P 3/02 H01P 3/08 H03B 5/18 H01P 5/02 JICST file (JOIS)

Claims (12)

(57) [Claims] 1. (2n-1) / determined by a certain phase constant β
An open-end stub having a length of four wavelengths (n = 1, 2,...) And having a phase constant smaller than β by a sufficiently small amount δβ compared to the value of the phase constant β; Having the same length and characteristic impedance as the open-end stub of the above, and comparing the value of the phase constant β with the value of the β by the δβ
A microwave resonance circuit, wherein an open-ended stub having a larger phase constant is connected in parallel. 2. (2n-1) / determined by a certain phase constant β
Having a length of 4 wavelengths (n = 1, 2,...) And a phase constant
Tip with β ₁ and real part R ₀₁ of characteristic impedance
It has the same length as the open stub and the open end stub.
And the real part R _{02 of} the phase constant β ₂ and the characteristic impedance
That the open-end stub with the value of
A microwave resonance circuit characterized by the above constant
β, β ₁ , β ₂ , R ₀₁ , and R ₀₂ represent And (β−β ₁ ) and (β ₂ −β)
Microwave resonance characterized by being sufficiently small compared to β
circuit. 3. An n / 2 wavelength (n) determined by a certain phase constant β.
= 1, 2,...) And having a phase constant smaller than β by a sufficiently small amount δβ compared to the value of the phase constant β; A microwave resonance circuit having a tip short-circuit stub having the same length and characteristic impedance as above, and having a phase constant larger than the value of β by δβ compared to the value of the phase constant β. . 4. An n / 2 wavelength (n) determined by a certain phase constant β.
= 1,2, has a length of ...), phase constant beta ₁ and Japanese
-End short-circuit stub with real part R ₀₁ of the directional impedance
Having the same length as the tip short-circuit stub, and a phase constant
has the value of β ₂ and the real part R ₀₂ of the characteristic impedance
Ma characterized that you a short-circuited stub connected in parallel
An electromagnetic wave resonance circuit, wherein the constants β, β ₁ ,
β ₂ , R ₀₁ , and R ₀₂ are as _follows : And (β−β ₁ ) and (β ₂ −β)
Microwave resonance characterized by being sufficiently small compared to β
circuit. 5. The microwave resonance according to claim 2 , wherein the open-end stubs or the short-circuited stubs having different phase constants are formed of microstrip lines having different center line widths. circuit. 6. The microwave resonance according to claim 2 , wherein the open-end stubs or the short-circuited stubs having different phase constants are formed of coplanar waveguides having different center line widths. circuit. 7. The different open stub or short-circuited stub of the phase constant from each other, the length of the gap between the center line and the ground metal is characterized by being configured by different coplanar waveguide, according to claim 2 or Contract
The microwave resonance circuit according to claim 4 . 8. An open-ended stub or a short-circuited stub having a different phase constant from each other by forming a dielectric film on a semiconductor or semi-insulating substrate below and around one of the open-ended stubs or the short-circuited stub. 5. The microwave resonance circuit according to claim 2 , wherein the microwave resonance circuit is configured. 9. An open-end stub or a short-circuited stub having a different phase constant from each other by forming a projection on a semiconductor or semi-insulating substrate below and around one of the open-end stubs or short-circuited stubs. 5. The microwave resonance circuit according to claim 2 , wherein the microwave resonance circuit is configured. 10. An open-ended stub or a short-circuited stub having a different phase constant from each other by forming a concave portion on the lower surface of one of the open-ended stubs or the short-circuited stub and on the back surface of a semiconductor or semi-insulating substrate. 5. The microwave resonance circuit according to claim 2 , wherein the microwave resonance circuit is configured. 11. An open-end stub or a short-circuited stub having a different phase constant from each other, and a projection formed on a lower surface of one of the open-end stubs or the short-end stub and on the back surface of a semiconductor or semi-insulating substrate. 5. The microwave resonance circuit according to claim 2 , wherein the microwave resonance circuit is realized by: 12. A microwave oscillator comprising the microwave resonance circuit according to any one of claims 1 to 11 .