JP2003347859A - High-frequency amplifier - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To suppress variations in input impedance in a wide frequency band and to secure the stability of an unstable high-frequency amplifier in a low-frequency region. SOLUTION: An input matching circuit 5A of a high-frequency amplifier is constituted by a series circuit of a series capacitor 51, a series inductor 52, a parallel inductor 53, and a resistor 54 of 2Ω or more and less than 15Ω. By adding a series resistor 54 to the parallel inductance 53, the variation of the input impedance is suppressed in a wide band, the passage outside the desired frequency band is suppressed, the stability index K of the entire band is set to 1 or more, and the noise figure is reduced. Improve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-frequency amplifier using a field-effect transistor or a bipolar transistor as a high-frequency power transistor.

[0002]

2. Description of the Related Art As a conventional example of a high-frequency amplifier, there is a circuit configuration as shown in FIG. 9, this high-frequency amplifier includes an input terminal 1, an input matching circuit 5, a power high-frequency transistor 3, an output matching circuit 7, an output terminal 2, a bias terminal 4, and a bias circuit 6. ing.

[0005] The input terminal 1 is connected to the gate (base in the case of a bipolar transistor) of the high frequency power transistor 3 via an input matching circuit 5. The bias terminal 4 is connected to the gate of the high frequency power transistor 3 via the bias circuit 6. The output terminal 3 is connected to the drain of the high-frequency power transistor 3 via the output matching circuit 7.

The input matching circuit 5 shown in FIG. 9 usually has a capacitor having an effect of preventing the bias current and bias voltage of the power high-frequency transistor 3 from leaking to the signal source side, and passes only a desired frequency. A bandpass circuit 56 composed of a capacitor and an inductor, and a parallel inductor 53 having an inductance value L1 for impedance adjustment. It should be noted that the capacitor of the band-pass circuit 56 serves as a bias current of the power high-frequency transistor 3,
The capacitor also serves as a capacitor having an effect of preventing the bias voltage from leaking to the signal source side.

As a general circuit, for example, as shown in FIG. 10, an input matching circuit 5 in a high-frequency amplifier includes a low-frequency block for preventing a bias current and a bias voltage of a high-frequency power transistor 3 from leaking to a signal source side. And a series capacitor 51 having a capacitance value C1 for use with the series capacitor 51 and an inductance value L2 provided to form a band-pass circuit 56 with the series capacitor 51 so as to pass only a desired frequency.
And a parallel inductor 53 having an inductance value L1 for converting the impedance seen from the power high-frequency transistor 3 from the conjugate impedance of the power high-frequency transistor 3 to 50Ω.

The output matching circuit 7 has, for example, a configuration as shown in FIG. In FIG. 13, reference numeral 71 denotes a bias terminal, 72 denotes a bias circuit, 73 to 75 denote strip lines, and 76 to 78 denote capacitors.

[0007]

The input matching circuit 5 of the above-mentioned conventional high-frequency amplifier includes an input impedance of the power high-frequency transistor 3 in a desired frequency band and an output impedance of a circuit connected to the input terminal 1 of the high-frequency amplifier. (Usually 50Ω) to bring out the characteristics of the power high-frequency transistor 3. Therefore, in order to stably operate the power high-frequency transistor 3, it is necessary to make the input impedance of the high-frequency amplifier seen from the outside be 50Ω over a wider band.

Further, in order to avoid the oscillation operation of the power high-frequency transistor 3, it is necessary to sufficiently suppress the gain other than the desired frequency band and make the stability index K larger than 1.

Here, the stability index K is an index indicating the stability of a two-port circuit such as an amplifier. The stability is determined by the two-terminal pair circuit and the circuit conditions added to the input side and the output side, and is expressed by the following equation from the S parameter.

K = ｛1 + │Δ│ ² −│S ₁₁ │ ² −│S ₂₂ │
_{^{2} / (2 · │S 21}} · S 12 │ 2) │Δ│ = │S 11 · S 22 / S 21 · S 12 │ high frequency amplifier is connected to the input terminal 1 and output terminal 2, any impedance Conditions that are also stable are K> 1 and | Δ | <1.

Since the three-terminal elements such as the power high-frequency transistor 3 usually satisfy | Δ | <1, the stability can be determined by the value of K. That is, when K> 1, the condition is unconditionally stable, and no oscillation occurs for any value of the input impedance and the output impedance. However, when K <1, it is conditionally stable, which suggests that a circuit-like unstable operation such as oscillation may occur depending on the values of the input impedance and the output impedance.

Formula of stability index K consisting of S parameters
Therefore, to increase the stability index K, S _{twenty one}And S₁₂Is small
It can be seen that it should be done. This is an unstable frequency region
Reducing the gain of a region increases the stability of that region
It is shown that.

In order to secure the stability of the high-frequency amplifier by increasing the stability index K, a method for suppressing the passage outside the desired frequency band includes, for example, the parallel inductor 5.
3 or reduce the capacitance value C1 of the series capacitor 51,
This can be realized by a combination that increases the inductance value L2 of the series inductor 52.

However, when the inductance value L1 of the parallel inductor 53 is reduced, the input impedance becomes 50%.
It will deviate from Ω. When the capacitance value C1 of the series capacitor 51 is reduced and the inductance value L2 of the series inductor 52 is increased,
The sensitivity of the variation of the input impedance with respect to the capacitance value C1 of the series capacitor 51 increases, which causes the input impedance to vary greatly. The above-described variation in input impedance causes variation in characteristics of the high-frequency amplifier, which is disadvantageous in terms of productivity.

An object of the present invention is to reduce the frequency characteristic change by making the input impedance close to 50Ω in a wider band, and to reduce the variation of the input impedance, thereby reducing the dependence of the input impedance on the capacitance value of the series capacitor. A wideband that enables a combination of reducing the capacitance value of the series capacitor and increasing the inductance value of the series inductor, and simultaneously suppressing the passage outside the desired frequency band to stably operate the high-frequency power transistor. An object of the present invention is to provide a high-frequency amplifier.

[0016]

According to a first aspect of the present invention, there is provided a high-frequency amplifier, a high-frequency transistor, an input matching circuit connected to an input side of the high-frequency transistor, and an output connected to an output side of the high-frequency transistor. And a matching circuit. The input matching circuit has a band-pass circuit for passing a desired frequency and a parallel inductor for impedance adjustment. The parallel inductor includes a series resistance component of 2Ω or more and less than 15Ω.

In particular, a parallel inductor for converting the impedance seen from the high-frequency transistor from the conjugate impedance of the high-frequency transistor to, for example, 50 Ω contains a series resistance component of 2 Ω or more and less than 15 Ω. A parallel inductor including a series resistance component of 2Ω or more and less than 15Ω can be configured as, for example, one chip component having a multilayer structure.

According to this configuration, the parallel inductor has a resistance of 2Ω.
Since a series resistance component of less than 15 Ω is included, the input impedance can be made close to 50 Ω in a wide band, and the variation in the frequency characteristic can be reduced to suppress the variation in the input impedance. As a result, a combination of a series capacitor and a series inductor for suppressing a gain in a low frequency region becomes possible, the stability index of the high-frequency amplifier can be made larger than 1, and the high-frequency transistor also operates stably. Further, since the passage of noise outside the desired frequency region can be suppressed by the series resistance component, it is possible to simultaneously improve the noise level outside the desired frequency region.

A high frequency amplifier according to a second aspect of the present invention comprises:
It comprises a high-frequency transistor, an input matching circuit connected to the input side of the high-frequency transistor, and an output matching circuit connected to the output side of the high-frequency transistor. The input matching circuit includes a band-pass circuit for passing a desired frequency, a parallel inductor for impedance adjustment, and 2Ω or more.
A series circuit of resistors having a resistance value of less than Ω.

According to this configuration, since a resistor having a resistance value of 2 Ω or more and less than 15 Ω is provided in series with the parallel inductor, the input impedance can be made close to 50 Ω in a wide band, and the frequency characteristic change can be reduced. Variation in input impedance can be suppressed. As a result, a combination of a series capacitor and a series inductor for suppressing a gain in a low frequency region becomes possible, the stability index of the high-frequency amplifier can be made larger than 1, and the high-frequency transistor also operates stably. Further, since the passage of noise outside the desired frequency region can be suppressed by the series resistance component, it is possible to simultaneously improve the noise level outside the desired frequency region.

According to a third aspect of the present invention, there is provided a high-frequency amplifier comprising:
It comprises a high-frequency transistor, an input matching circuit connected to the input side of the high-frequency transistor, and an output matching circuit connected to the output side of the high-frequency transistor. The input matching circuit has a band-pass circuit for passing a desired frequency and a parallel inductor for impedance adjustment. The parallel inductor includes a parallel resistance component of 50Ω or more and less than 1 kΩ.

In particular, a parallel inductor for converting the impedance viewed from the high-frequency transistor from the conjugate impedance of the high-frequency transistor to, for example, 50Ω includes a parallel resistance component of 50Ω or more and less than 1 kΩ. Note that a parallel inductor including a parallel resistance component of 50Ω or more and less than 1 kΩ can be configured as, for example, one multilayer chip component.

According to this configuration, 50 parallel inductors are used.
Since a parallel resistance component of Ω or more and less than 1 kΩ is included,
The input impedance can be made close to 50Ω over a wide band, and the variation in the frequency characteristics can be reduced to suppress the variation in the input impedance. As a result, a combination of a series capacitor and a series inductor for suppressing a gain in a low frequency region becomes possible, the stability index of the high-frequency amplifier can be made larger than 1, and the high-frequency transistor also operates stably. Further, since the passage of noise outside the desired frequency region can be suppressed by the parallel resistance component, it is possible to simultaneously improve the noise level outside the desired frequency region.

A high frequency amplifier according to a fourth aspect of the present invention comprises:
It comprises a high-frequency transistor, an input matching circuit connected to the input side of the high-frequency transistor, and an output matching circuit connected to the output side of the high-frequency transistor. The input matching circuit includes a band-pass circuit for passing a desired frequency, a parallel inductor for impedance adjustment, and 50Ω or more.
and a parallel circuit of resistors having a resistance value of less than kΩ.

According to this configuration, since a resistor having a resistance value of 50 Ω or more and less than 1 kΩ is provided in parallel with the parallel inductor, the input impedance can be made close to 50 Ω in a wide band, and the change in frequency characteristics can be reduced. Variation in input impedance can be suppressed. As a result, a combination of a series capacitor and a series inductor for suppressing a gain in a low frequency region becomes possible, the stability index of the high-frequency amplifier can be made larger than 1, and the high-frequency transistor also operates stably. Further, since the passage of noise outside the desired frequency region can be suppressed by the parallel resistance component, it is possible to simultaneously improve the noise level outside the desired frequency region.

According to a fifth aspect of the present invention, there is provided a high-frequency amplifier comprising:
The high frequency amplifier according to claim 2, wherein the series circuit of the parallel inductor and the resistor is configured as one chip component having a multilayer structure.

According to this configuration, a series circuit of a parallel inductor and a resistor can be realized with a simple configuration of one chip component having a multilayer structure, and the input impedance can be close to 50Ω in a wide band without increasing the number of components. Thus, the change in the frequency characteristic can be reduced, and the variation in the input impedance can be suppressed. Others are the same as in claim 2.

The high-frequency amplifier according to claim 6 of the present invention comprises:
A high frequency amplifier according to claim 4, wherein the parallel circuit of the parallel inductor and the resistor is configured as one chip component having a multilayer structure.

According to this configuration, a parallel circuit of a parallel inductor and a resistor can be realized with a simple configuration of one chip component having a multilayer structure, and the input impedance can be made close to 50Ω in a wide band without increasing the number of components. Thus, the change in the frequency characteristic can be reduced, and the variation in the input impedance can be suppressed. Others are the same as in claim 4.

The high-frequency amplifier according to claim 7 of the present invention comprises:
7. The high-frequency amplifier according to claim 1, wherein the high-frequency transistor comprises one or more cascade-connected field-effect transistors.

According to this configuration, claims 1, 2, 3,
It has the same function as the high-frequency amplifier described in 4, 5, or 6.

The high-frequency amplifier according to claim 8 of the present invention comprises:
The high-frequency amplifier according to claim 1, 2, 3, 4, 5, or 6, wherein the high-frequency transistor comprises one or more cascade-connected bipolar transistors.

According to this configuration, claims 1, 2, 3,
It has the same function as the high-frequency amplifier described in 4, 5, or 6.

According to a ninth aspect of the present invention, there is provided a high frequency amplifier comprising:
The high frequency amplifier according to claim 1, 2, 3, 4, 5, 6, 7, or 8, wherein the input matching circuit has a function of making the stability index of the high frequency amplifier larger than 1 in a desired frequency band. Features.

According to this structure, since the function of making the stability index of the high-frequency amplifier larger than 1 in the desired frequency band is provided, the high-frequency amplifier can be unconditionally stabilized regardless of the values of the input impedance and the output impedance. Can be.

[0036]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, a case of a high-frequency amplifier having a desired pass frequency band of 0.9 GHz to 1 GHz will be described as an example, but the pass frequency band is not limited to the above frequency band.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a circuit diagram illustrating a high-frequency amplifier according to the embodiment. Referring to FIG. 1, an input matching circuit 5A includes a series capacitor 51 having a capacitance value C1 and a series inductor L2 having an inductance value L2 inserted in series in a signal line from an input terminal 1 to an output terminal 2; It comprises a series circuit of a parallel inductor 53 having an inductance value L1 and a resistor 54 having a resistance value R1 inserted in parallel with a signal line reaching the output terminal 2. Other configurations are the same as the conventional example.

In the input matching circuit 5A of FIG. 1, since the frequency band to be passed is in the 0.9 GHz to 1 GHz band, the inductance value L1 of the parallel inductor 53 is set to 3.
7 nH, the capacitance value C1 of the series capacitor 51 is 1.5 pF, and the inductance value L of the series inductor 52 is
2 is set to 15 nH.

In order to make the circuit equivalent to the input matching circuit 5 of the high frequency amplifier according to the prior art shown in FIG.
4 may be set to 0Ω. By doing so, the same operation as that of FIG. 10 can be realized.

FIG. 3 shows that the resistance value R1 of the resistor 54 is 0
The return loss characteristics (S ₁₁ ) of the high-frequency amplifier at Ω and 5Ω are shown. The smaller the return loss, the closer the input impedance of the high-frequency amplifier viewed from the outside is to 50Ω. FIG. 3 shows that the resistance 5 of the input matching circuit 5A
It is understood that the return loss of the high-frequency amplifier can be reduced in a wide band by changing the resistance value R1 of No. 4 from 0Ω to 5Ω.

FIG. 11A shows the return loss (S) of 200 samples in the transmission frequency band 893 MHz used in the PDC system of the portable telephone when the resistance value R1 of the resistor 54 is 0Ω and 5Ω, respectively. ₁₁ ) is the measurement result. FIG. 11B shows the resistance value R1 of the resistor 54.
Is 0Ω and 5Ω respectively, the transmission frequency band 9
It is a measurement result of the return loss (S ₁₁₎ of each 200 samples in 58 MHz. 11A and 11B, “no input resistance” is a measurement result of 200 samples when the resistance value R1 is 0Ω, and “input resistance insertion” is 200 when the resistance value R1 is 5Ω. It is a measurement result of this sample.

The return loss (S ₁₁ ) shown in FIGS. 11 (a) and 11 (b) is obtained by changing the resistance value R1 of the resistor 54 from 0Ω to 5Ω to obtain a transmission frequency band 893 MHz used in the PDC system of a portable telephone. , 958 MHz are improved by about 2 to 5 dB, and the variation in input impedance is reduced.

After all, since the input impedance of the high-frequency amplifier viewed from the outside is close to 50Ω in a wide band, the capacitance value C of the series capacitor 51 of the input matching circuit 5A is determined.
The variation of the input impedance with respect to the variation of 1 can be reduced. This enables the combination of reducing the capacitance value C1 of the series capacitor 51 and increasing the inductance value L2 of the series inductor 52, which is the object of the present invention. It is possible to provide a wide-band high-frequency amplifier that operates stably.

FIG. 4 shows the pass characteristic (S ₂₁ ) of the input matching circuit 5A shown in FIG. As shown in FIG. 4, by changing the resistance R1 of the resistor 54 of the input matching circuit 5A from 0Ω to 5Ω, it is possible to suppress the passage in a low frequency region.

FIG. 5 shows the frequency characteristic of the stability index K of the high-frequency amplifier using the input matching circuit 5A shown in FIG. FIG.
As shown in (1), when the resistance value R1 of the resistor 54 is 0Ω, there is a frequency region where the stability index K is less than 1 and there is a possibility of performing an unstable operation. However, as shown in FIG. 4, the resistance value R1 of the resistor 54 of the input matching circuit 5A is set to 0.
By changing from Ω to 5Ω, it is possible to suppress the passage in an unstable low frequency region. For this reason, the stability index K is set to 1 or more in all frequency regions, and a wideband and stable high-frequency amplifier is provided.

Furthermore, as shown in FIG. 4, since the transmission in the low frequency region can be suppressed, the noise level in that region can be improved. For example, by changing the resistance R1 of the resistor 54 of the input matching circuit 5A from 0Ω to 5Ω,
As shown in the frequency characteristic of the gain in FIG. 12, since the passage in a low frequency region can be suppressed, the noise in the reception band 885 MHz used in the PDC system of the mobile phone is reduced to about 2 dBm / Hz.
Can be improved. Here, the resistance value R1 is 5
Although a resistor of Ω was used, the above effect is further enhanced by using a resistor having a larger resistance value. However, when a resistor of 15Ω or more is used, it is necessary to pay attention to a decrease in gain at a desired frequency.

The reason is that when a resistor is inserted in the input matching circuit 5A, the gain always drops as shown in FIG. In the circuit configuration of the present embodiment, the gain in the pass band cannot be increased beyond the decrease due to the resistance of the components (capacitor and inductor) other than the resistance.

FIGS. 14 and 15 show the return loss and gain characteristics of the high-frequency amplifier when the resistance value R1 of the resistor 54 of the input matching circuit 5A is changed. Generally, a return loss characteristic required for a high-frequency amplifier is -6 dB or less, and a gain characteristic is 24 dB or more. 14 and 15 showing the return loss characteristic and the gain characteristic show that the resistance value range satisfying this characteristic is in the range of 2Ω to 15Ω, and the resistance value in this range can be used.

The above resistance value range of 2Ω to 15Ω corresponds to FIG.
Range of -6 dB or less in the return loss characteristic of
This is a resistance value range that satisfies both 31Ω and a range of 0Ω to 15Ω of 24 dB or more in the gain characteristic of FIG. That is, the lower limit is defined by the lower limit of 2Ω in the return loss characteristic, and the upper limit is defined by the upper limit of 15Ω in the gain characteristic.

Further, since the resistance component having a size of 1 mm × 0.5 mm, which is commercially available as a normal chip inductor component, is about 50 mΩ to 300 mΩ, the above effect can be realized only by the inductor 53 of the conventional circuit technology shown in FIG. Can not. However, if an inductor having a large resistance value (effective at 2 Ω or more) is included in series with the inductor as a single chip component, or if an inductor having a multi-layer structure added can be used, the component can be compared with the conventional example. A high frequency amplifier having the same function as the input matching circuit 5A of FIG. 1 can be realized without increasing the number of points.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
FIG. 3 is a circuit diagram illustrating a high-frequency amplifier according to the embodiment. Referring to FIG. 2, the input matching circuit 5B includes a series capacitor 51 having a capacitance value C1 and a series inductor 52 having an inductance value L2 inserted in series in a signal line extending from the input terminal 1 to the output terminal 2. It comprises a parallel circuit of a parallel inductor 53 having an inductance value L1 and a resistor 55 having a resistance value R2 inserted in parallel to a signal line reaching the output terminal 2. Other configurations are the same as the conventional example.

In the input matching circuit 5B of FIG. 2, as in the case of FIG.
Since it is in the 1 GHz band, the inductance value L1 of the parallel inductor 53 is set to 4.7 nH,
Is set to 1.5 pF, and the inductance value L2 of the series inductor 52 is set to 15 nH.

In order to make the circuit equivalent to the input matching circuit 5 of the conventional high-frequency amplifier shown in FIG.
By setting the resistance value R2 of No. 5 to a value sufficiently larger than the impedance of the parallel inductor 53, the same operation as that of FIG. 10 can be realized. Since the resistance component of an inductor commercially available as a normal chip component is approximately 50 mΩ to 300 mΩ, if a resistor having a resistance value R2 of 1 KΩ is used as the resistor 55, the input matching circuit 5 having no resistance component of the related art is used. The same function as can be realized.

FIG. 6 shows that the resistance value R2 of the resistor 55 is 1
The return loss characteristics (S ₁₁ ) of the high-frequency amplifier when KΩ and 100Ω are shown. The smaller the return loss, the closer the input impedance of the high-frequency amplifier viewed from the outside is to 50Ω. FIG. 6 shows that the return loss of the high-frequency amplifier can be reduced over a wide band by changing the resistance value R2 of the resistor 55 of the input matching circuit 5B from 1 KΩ to 100Ω.

After all, since the input impedance of the high-frequency amplifier viewed from the outside is close to 50Ω in a wide band, the capacitance value C of the series capacitor 51 of the input matching circuit 5B is determined.
The variation of the input impedance with respect to the variation of 1 can be reduced. This enables the combination of reducing the capacitance value C1 of the series capacitor 51 and increasing the inductance value L2 of the series inductor 52, which is the object of the present invention. It is possible to provide a wide-band high-frequency amplifier that operates stably.

FIG. 7 shows the pass characteristic (S ₂₁ ) of the input matching circuit 5B shown in FIG. As shown in FIG. 7, the resistance value R2 of the resistor 55 of the input matching circuit 5B is changed from 1 KΩ to 100Ω.
, It is possible to suppress passage outside the desired frequency range.

FIG. 8 shows the frequency characteristic of the stability index K of the high-frequency amplifier using the input matching circuit 5B shown in FIG. FIG.
As shown in (1), when the resistance value R2 of the resistor 55 is 1 KΩ, there is a frequency region where the stability index K is less than 1 and there is a possibility of performing an unstable operation. However, as shown in FIG. 7, the resistance value R2 of the resistor 55 of the input matching circuit 5B is set to 1
By changing from KΩ to 100Ω, it is possible to suppress the passage in an unstable low frequency region. For this reason, the stability index K is set to 1 or more in all frequency regions, and a wideband and stable high-frequency amplifier is provided.

Further, by changing the resistance value R2 of the resistor 55 of the input matching circuit 5B from 1 KΩ to 100Ω, it is possible to suppress the passage in a low frequency region, thereby improving the noise level in that region. Here, the resistance 5
Although a resistor having a resistance value R2 of 100Ω is used as 5, the effect is further increased by using a smaller resistor. However, when a resistance of less than 50Ω is used, it is necessary to pay attention to a decrease in gain at a desired frequency.

FIGS. 16 and 17 show the return loss and gain characteristics of the high-frequency amplifier when the resistance value R2 of the resistor 55 of the input matching circuit 5B is changed. Generally, a return loss characteristic required for a high-frequency amplifier is -6 dB or less, and a gain characteristic is 24 dB or more. 16 and 17 showing the return loss characteristic and the gain characteristic indicate that the resistance value range satisfying this characteristic is in the range of 50Ω to 1000Ω, and the resistance value in this range can be used.

The above resistance value range of 50 Ω to 1000 Ω
The range of −6 dB or less of 20Ω to 1000Ω in the return loss characteristic of FIG.
This is a resistance value range that satisfies both the range of not less than dB and not less than 50Ω. In other words, the lower limit is the lower limit value 50Ω in the gain characteristics.
The upper limit is the upper limit value 1 in the return loss characteristics.
000Ω.

If a resistance component (about 100 Ω to 1 KΩ) is included in parallel with the inductor as one chip component, or if an inductor having a multilayer structure added can be used, the number of components is increased as compared with the conventional example. A high-frequency amplifier having the same function as the input matching circuit 5B of FIG.

In the above embodiment, the field effect transistor is used as the high frequency power transistor.
Bipolar transistors can also be used.

[0063]

According to the high-frequency amplifier according to the first aspect of the present invention, the parallel inductor in the input matching circuit contains a series resistance component of 2 Ω or more and less than 15 Ω, so that the input impedance approaches 50 Ω in a wide band. Thus, a change in frequency characteristics can be reduced, and variations in input impedance can be suppressed. As a result, a combination of a series capacitor and a series inductor for suppressing a gain in a low frequency region becomes possible, the stability index of the high-frequency amplifier can be made larger than 1, and the high-frequency transistor also operates stably. Further, since the series resistance component can suppress the passage of noise outside the desired frequency range,
Improving the noise level outside the desired frequency range can also be achieved at the same time. Therefore, it is possible to obtain a high-frequency amplifier having a stable operation in a wide band that cannot be obtained by the conventional band broadening method, a gain and distortion characteristic with a small variation, and a good noise level.

According to the high-frequency amplifier according to the second aspect of the present invention, the high-frequency amplifier is connected in series with the parallel inductor in the input matching circuit.
Since a resistor having a resistance value of Ω or more and less than 15 Ω is provided, the same effect as that of the high-frequency amplifier according to claim 1 can be obtained.

According to the high-frequency amplifier of the third aspect of the present invention, the parallel inductor in the input matching circuit contains a parallel resistance component of 50Ω or more and less than 1 kΩ. Variations in characteristics can be reduced, and variations in input impedance can be suppressed. As a result, a combination of a series capacitor and a series inductor for suppressing a gain in a low frequency region becomes possible, the stability index of the high-frequency amplifier can be made larger than 1, and the high-frequency transistor also operates stably. Furthermore, since the passage of noise outside the desired frequency range can be suppressed by the parallel resistance component,
Improving the noise level outside the desired frequency range can also be achieved at the same time. Therefore, it is possible to obtain a high-frequency amplifier having a stable operation in a wide band that cannot be obtained by the conventional band broadening method, a gain and distortion characteristic with a small variation, and a good noise level.

According to the high-frequency amplifier according to the fourth aspect of the present invention, 5 parallel to the parallel inductor in the input matching circuit.
Since a resistor having a resistance value of 0 Ω or more and less than 1 kΩ is provided, the same effect as the high frequency amplifier according to the third aspect is obtained.

According to the high-frequency amplifier according to the fifth aspect of the present invention, the effect of the first aspect can be achieved without increasing the number of components.

According to the high-frequency amplifier according to the sixth aspect of the present invention, the effect of the third aspect can be achieved without increasing the number of components.

According to the high-frequency amplifier according to the seventh aspect of the present invention, the same effects as those of the high-frequency amplifier according to the first, second, third, fourth, fifth or sixth aspect are obtained.

According to the high-frequency amplifier according to the eighth aspect of the present invention, the same effect as that of the high-frequency amplifier according to the first, second, third, fourth, fifth or sixth aspect is obtained.

According to the ninth aspect of the present invention, the high frequency amplifier has a function of making the stability index of the high frequency amplifier larger than 1 in a desired frequency band. Regardless, it can be stabilized unconditionally.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a high-frequency amplifier according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a high-frequency amplifier according to a second embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a return loss characteristic (S ₁₁ ) of the high-frequency amplifier according to the first embodiment.

FIG. 4 is a characteristic diagram showing pass characteristics (S ₂₁ ) of the high-frequency amplifier according to the first embodiment.

FIG. 5 is a characteristic diagram illustrating frequency characteristics of a stability index K of the high-frequency amplifier according to the first embodiment.

FIG. 6 is a characteristic diagram showing a return loss characteristic (S ₁₁ ) of the high-frequency amplifier according to the second embodiment.

FIG. 7 is a characteristic diagram showing pass characteristics (S ₂₁ ) of the high-frequency amplifier according to the second embodiment.

FIG. 8 is a characteristic diagram showing characteristics of a stability index K of the high-frequency amplifier according to the second embodiment.

FIG. 9 is a circuit diagram illustrating an example of a conventional high-frequency amplifier.

FIG. 10 is a circuit diagram of a conventional high-frequency amplifier.

FIG. 11 is a graph showing a return loss characteristic (S ₁₁ ) of the high-frequency amplifier according to the first embodiment.

FIG. 12 is a graph showing a pass characteristic (S ₂₁ ) of the high-frequency amplifier according to the first embodiment.

FIG. 13 is a circuit diagram showing a circuit example of an output matching circuit.

FIG. 14 is a characteristic diagram illustrating resistance-return loss characteristics according to the first embodiment.

FIG. 15 is a characteristic diagram showing resistance-gain characteristics in the first embodiment.

FIG. 16 is a characteristic diagram illustrating resistance-return loss characteristics according to the second embodiment.

FIG. 17 is a characteristic diagram illustrating resistance-gain characteristics according to the second embodiment.

[Explanation of symbols] 1 input terminal 2 Output terminal 3 High frequency transistors for power 4 Bias terminal 5,5A, 5B input matching circuit 6. Bias circuit 7 Output matching circuit 51 Series capacitor 52 series inductor 53 parallel inductor 54 resistor

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kazuki Tateoka             Matsushita Electric, 1006 Kadoma, Kazuma, Osaka             Sangyo Co., Ltd. F-term (reference) 5J091 AA04 AA41 CA21 CA41 CA62                       CA92 FA00 FA20 HA09 HA25                       HA29 HA33 KA12 KA29 KA68                       TA01 TA02 TA03                 5J092 AA04 AA41 CA21 CA41 CA62                       CA92 FA00 FA20 HA09 HA25                       HA29 HA33 KA12 KA29 KA68                       TA01 TA02 TA03 VL08                 5J500 AA04 AA41 AC21 AC41 AC62                       AC92 AF00 AF20 AH09 AH25                       AH29 AH33 AK12 AK29 AK68                       AT01 AT02 AT03 LV08

Claims (9)

[Claims] 1. A high-frequency amplifier comprising a high-frequency transistor, an input matching circuit connected to an input side of the high-frequency transistor, and an output matching circuit connected to an output side of the high-frequency transistor, wherein the input matching circuit is Is a high-frequency amplifier having a band-pass circuit for passing a desired frequency and a parallel inductor for impedance adjustment, wherein the parallel inductor contains a series resistance component of 2Ω or more and less than 15Ω. 2. A high-frequency amplifier comprising a high-frequency transistor, an input matching circuit connected to an input side of the high-frequency transistor, and an output matching circuit connected to an output side of the high-frequency transistor, wherein the input matching circuit is Is a band-pass circuit for passing a desired frequency, a parallel inductor for impedance adjustment, and 2
A series circuit of a resistor having a resistance value of not less than Ω and less than 15 Ω. 3. A high-frequency amplifier comprising a high-frequency transistor, an input matching circuit connected to an input side of the high-frequency transistor, and an output matching circuit connected to an output side of the high-frequency transistor, wherein the input matching circuit A high-frequency amplifier having a band-pass circuit for passing a desired frequency and a parallel inductor for impedance adjustment, wherein the parallel inductor contains a parallel resistance component of 50Ω or more and less than 1 kΩ. 4. A high-frequency amplifier comprising a high-frequency transistor, an input matching circuit connected to an input side of the high-frequency transistor, and an output matching circuit connected to an output side of the high-frequency transistor, wherein the input matching circuit Are a band-pass circuit for passing a desired frequency, a parallel inductor for impedance adjustment, and 5
A parallel circuit of resistors having a resistance value of 0Ω or more and less than 1 kΩ. 5. The high-frequency amplifier according to claim 2, wherein the series circuit of the parallel inductor and the resistor is configured as one chip component having a multilayer structure. 6. The high-frequency amplifier according to claim 4, wherein the parallel circuit of the parallel inductor and the resistor is configured as one chip component having a multilayer structure. 7. The high-frequency transistor has one stage or two stages.
7. The high-frequency amplifier according to claim 1, wherein the high-frequency amplifier is constituted by field-effect transistors cascaded in stages. 8. The high-frequency transistor has one stage or two stages.
7. The high-frequency amplifier according to claim 1, wherein the high-frequency amplifier comprises bipolar transistors cascaded in stages or more. 9. The input matching circuit according to claim 1, wherein the input matching circuit has a function of making the stability index of the high-frequency amplifier larger than 1 in a desired frequency band. 9. The high-frequency amplifier according to 8.