JP2001016053A - High frequency power amplifier - Google Patents

Abstract

(57) [Problem] To provide a conventional high-frequency power amplifier having a two-stage configuration, a harmonic control circuit must be added as a separate circuit from an amplifier circuit. SOLUTION: A high-frequency power amplifier Q11, an input matching circuit, an inter-stage matching circuit, an output matching circuit, a distributed constant line L12 connected to an output electrode of a preceding high-frequency power amplifier Q11, and A bias circuit E includes a pre-stage bias circuit E and a post-stage bias circuit including an inductor L17 connected in series. The pre-stage bias circuit E has a combined reactance component functioning as a part of an interstage matching circuit, and has a distributed constant line L12 and an inductor L17. Is a two-stage high-frequency power amplifier having a resonance point for higher-order harmonics.
Since the pre-stage bias circuit E also functions as a harmonic control circuit, it is not necessary to add a harmonic control circuit as another circuit, and the size can be further reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency power amplifier used for amplifying high-frequency power in a microwave band or the like in a mobile communication device such as a portable telephone.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for miniaturization, weight reduction and high efficiency, that is, low current consumption of semiconductor devices and electric components used in mobile communication device terminals such as mobile phones and wireless devices. Similarly, high-frequency power amplifiers used in these transmission units are also required to be reduced in size and weight. Above all, regarding high efficiency, since the high-frequency power amplifier consumes about half the current of the entire terminal equipment, low current is a major issue.

The circuit configuration of such a high-frequency power amplifier generally has a multi-stage configuration using two stages of a high-frequency power amplifier for power amplification, and includes an input / output circuit and a two-stage high-frequency power amplifier. The inter-stage circuit between them includes an inter-stage matching circuit for obtaining desired characteristics and a pre-stage bias circuit for supplying a direct current to the output electrode of the pre-stage high-frequency power amplifier.

FIG. 4 is a circuit diagram showing an example of a typical circuit configuration of such a conventional high-frequency power amplifier.

In FIG. 4, Q1 and Q2 are high-frequency power amplifiers having a two-stage configuration for performing power amplification. Here, a field effect transistor (FET) is shown. C1 and C6 are decoupling capacitors for cutting off the DC component between the high-frequency power amplifier and other circuits, and usually have a capacitance value such that the impedance becomes sufficiently low with respect to the fundamental frequency of the high-frequency signal. You.

C2 · L1 and C5 · L6, and C
4, L3 and L4 are high-frequency power amplifiers Q1 and Q, respectively.
And a distributed constant line, for example, a microstrip line, for optimizing the impedance of the high-frequency signal between the input / output circuit and the high-frequency power amplifiers Q1 and Q2 with respect to the fundamental frequency in order to bring out the performance of the second embodiment. The input matching circuit is formed by C2 · L1 and C5 · L1, respectively.
L6 forms an output matching circuit, and C4, L3, and L4 form an interstage matching circuit.

In the interstage matching of impedance, impedance matching is possible only with L3, and C4
・ L4 is not always required, C4 ・ L4
Is added according to the specifications of the high-frequency power amplifier and as necessary.

R1 and R2 are high-frequency power amplifiers Q
1. A resistor constituting a control bias circuit for supplying a control bias voltage to the gate of Q2 (control electrode as an input electrode).

L2 and L5 are high-frequency power amplifiers Q1
A distributed constant line that constitutes a pre-stage bias circuit and a post-stage bias circuit that supplies a current for drain and output of Q2, and is usually a quarter wavelength of the fundamental frequency, The impedance is set to be infinite when viewed from the drain (output electrode) side of the amplifiers Q1 and Q2, or set to a length that is negligibly large when viewed from the impedance of the circuit. In addition, this distributed constant line L2
L5 can be shorter than the line length and used as a reactance component of a part of the matching circuit.

C3 is a decoupling capacitor for preventing a direct current supplied from the pre-stage bias circuit to the high-frequency power amplifier Q1 from flowing into the high-frequency power amplifier Q2.
Normally, similarly to C1 and C6, the capacitance value is such that the impedance is sufficiently low when viewed from the fundamental frequency of the high-frequency signal.

C7 and C8 are bypass capacitors for alternating current grounding.

In the high-frequency power amplifier having such a circuit configuration, a certain amount of gain is obtained in the high-frequency power amplifier Q1 at the preceding stage, and the high-frequency power amplifier Q1 at the subsequent stage is obtained.
2 is dominant in other characteristics such as current consumption and distortion. For example, input power +5
Output power + 30.5dBm / dBm / Current consumption 500m
In the case of the high-frequency power amplifier A, the high-frequency power amplifier Q1
・ The gain of Q2 is about 15dB ・ 10dB, and the current is
It is about 100 mA / 400 mA.

Therefore, in order to increase the efficiency of the high-frequency power amplifier, it is essential to reduce the current of the high-frequency power amplifier Q2 at the subsequent stage. Regarding the impedance of the high-frequency signal with respect to the fundamental frequency, control for optimizing the impedance (low current) by load pull measurement or experimentally is generally performed. In addition, in the input matching circuit for the high-frequency power amplifier Q2 in the subsequent stage, that is, in the interstage matching circuit, the same control is performed on the higher harmonics of the fundamental frequency.

In a conventional high-frequency power amplifier, the control of higher-order harmonics of the fundamental frequency in the interstage matching circuit is performed by adding, for example, a distributed constant line, a capacitor as shown by D in FIG. This was done by adding a control circuit consisting of At this time, for example, it is set so as to have a series resonance point for a frequency twice as much as the fundamental frequency, so that the impedance appears to be zero with respect to the second harmonic of the fundamental frequency, and the state is set. Thereby, a harmonic control circuit for removing the second harmonic of the fundamental frequency is obtained.

[0015]

However, according to the conventional high frequency power amplifier shown in FIG. 4, since the interstage matching circuit controls the impedance with respect to the higher harmonic of the fundamental frequency of the high frequency signal. Since the circuit D is separately provided and added, it hinders downsizing of the high-frequency power amplifier, and there is a problem that it is not possible to cope with a further demand for downsizing of the high-frequency power amplifier.

The present invention has been devised in view of the above-mentioned problems in the prior art, and has as its object to provide a high-frequency signal in an interstage matching circuit in a high-frequency power amplifier using a two-stage high-frequency power amplifier. The control of the impedance for the higher-order harmonics of the fundamental frequency for controlling the impedance for the higher-order harmonics as viewed from the high-frequency power amplifier in the preceding stage and the impedance for the higher-order harmonics as viewed from the latter high-frequency power amplifier It is an object of the present invention to provide a high-frequency power amplifier having a harmonic control function, which does not need to add a circuit as a separate circuit, and can respond to a demand for further miniaturization.

[0017]

A high-frequency power amplifier according to the present invention comprises a two-stage high-frequency power amplifier for amplifying a high-frequency input signal supplied to an input electrode and outputting the amplified signal as a high-frequency output signal from an output electrode. An input matching circuit connected to the input electrode of the high-frequency power amplifying section for matching input impedance with respect to a fundamental frequency of the high-frequency input signal; An inter-stage matching circuit inserted between the input electrode of the amplifying unit and composed of a distributed constant line for impedance matching between the two-stage high-frequency power amplifying unit, and the output of the subsequent-stage high-frequency power amplifying unit An output matching circuit connected to the electrode, and connected to the output electrode of the pre-stage high-frequency power amplifier, for supplying a direct current to the pre-stage high-frequency power amplifier. A pre-stage bias circuit comprising a cloth constant line and an inductor connected in series to the distributed constant line, and the output electrode of the post-stage high-frequency power amplifier is connected to supply a DC current to the post-stage high-frequency power amplifier. And a post-stage bias circuit comprising a distributed constant line of the above, wherein the pre-stage bias circuit is provided for the fundamental frequency and high-order harmonics of the high-frequency input signal as viewed from the output electrode of the pre-stage high-frequency power amplification section to the post-stage side. A combined reactance component and the distributed constant line necessary for functioning as a part of the inter-stage matching circuit for impedance matching and impedance matching of the front-stage side from the input electrode of the high-frequency power amplification unit at the rear stage. And a resonance point with respect to the higher harmonic by the inductor and the inductor.

According to the high-frequency power amplifier of the present invention, the distributed constant line and the distributed constant line are connected as the pre-stage bias circuit connected to the output electrode of the pre-stage high-frequency power amplifier and supplying a DC current to the pre-stage high-frequency power amplifier. An inductor connected in series with the distributed constant line, having a combined reactance component necessary to function as a part of the interstage matching circuit due to the length of the distributed constant line and the inductance of the inductor, and Since a series resonance circuit is configured by a constant line and an inductor connected in series with the distributed constant line, and the series resonance frequency is configured to have a resonance point for a higher-order harmonic of a fundamental wave, This bias circuit achieves the original purpose of supplying a direct current to the high-frequency power amplifier in the preceding stage, and at the same time, partially reloads the interstage matching circuit. Function as a part of the interstage matching circuit as a reactance component, and impedance matching for the fundamental frequency and any higher harmonics of the high-frequency signal as seen from the output electrode of the high-frequency power amplifier at the previous stage In addition, impedance matching can be achieved for at least the fundamental frequency when the front side is viewed from the input electrode of the high-frequency power amplifying unit at the rear stage. It can be grounded from the point of view, thereby functioning also as a harmonic control circuit capable of removing any higher harmonics. As a result, there is no need to add a harmonic control circuit as a separate circuit, and a high-frequency power amplifier having a harmonic control function capable of responding to a demand for further miniaturization is provided.

Further, in this bias circuit, the combined reactance of the inductance of the inductor and the distributed constant line to which the inductor is connected in series and the inductance of the distributed constant line adjust the inductance of the inductor and the length of the distributed constant line, respectively. Therefore, it is possible to easily adjust the resonance frequency, that is, the resonance point, for any higher-order harmonic such as the second, third, fourth, or fifth order as a higher-order harmonic. It can be used for the purpose of removing spurious harmonics contained in the output of the high-frequency power amplifier.

Further, the inductance of the inductor connected in series to the distributed constant line of the bias circuit can be easily finely adjusted at the time of circuit configuration or after the circuit configuration, thereby finely adjusting the resonance point. Since it can be easily performed, it is possible to easily adjust the electrical characteristics of the harmonic power amplifier with high accuracy.

Further, when the distributed constant line is internally formed using a multilayer wiring board in response to the demand for downsizing of the high frequency power amplifier, it is possible to adjust the inductance of the inductor while downsizing the high frequency power amplifier. It is easily possible.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an example of a circuit configuration for explaining an example of an embodiment of a high-frequency power amplifier according to the present invention.

In FIG. 1, Q11 and Q12 are high-frequency power amplifiers for performing power amplification, which are used in a frequency range such as several hundred MHz to several GHz where a distributed constant line can be applied. A transistor (FET) is shown as an example.

C11 and C16 are decoupling capacitors for cutting off DC components from other circuits, respectively, and C13 is a DC component supplied to the high-frequency power amplifier Q11 in the preceding stage flowing into the high-frequency power amplifier Q12 in the subsequent stage. This is a decoupling capacitor that cuts off power. These decoupling capacitors C11, C13, C16 are usually set to have sufficiently low impedance when viewed from the fundamental frequency.
Input impedance matching for each fundamental frequency
It does not affect the interstage impedance matching and output impedance matching.

C12 and L11 denote a capacitor and a distributed constant constituting an input matching circuit for impedance matching between the high-frequency power amplifier Q11 in the previous stage and the input / output circuit in order to bring out the performance of the high-frequency power amplifier Q11 in the previous stage. A line, for example, a microstrip line. C15 ・ L16
Denotes a capacitor and a distributed constant line, for example, a microstrip line, which constitute an output matching circuit for matching so as to satisfy desired output characteristics, for example, distortion characteristics, output power, current consumption, etc. singly or simultaneously. These input matching circuits are connected to the gate (control electrode as an input electrode) of the high-frequency power amplifier Q11 at the preceding stage, and the output matching circuit is connected to the output electrode of the high-frequency power amplifier Q12 at the subsequent stage.

R11 and R12 are resistors constituting a bias circuit for supplying a bias voltage to the gates of the high-frequency power amplifier Q11 in the preceding stage and the high-frequency power amplifier Q12 in the subsequent stage.

L15 is a distributed constant line, for example, a microstrip line, which constitutes a bias circuit for supplying a current for output and a drain (output electrode) of the high-frequency power amplifier Q12 at the subsequent stage. Normally, the length is set to a quarter wavelength of the fundamental frequency so that the impedance looks infinite when viewed from the drain side of the high-frequency power amplifier Q12 at the subsequent stage, or from the viewpoint of the circuit impedance. The line length is set so as to have a negligible impedance.

C14 and L13 and L14 are a capacitor and a distributed constant line, for example, a microstrip line, for optimizing the impedance with respect to the fundamental frequency of the high-frequency signal between the two-stage high-frequency power amplifiers Q11 and Q12. These form an interstage matching circuit. In the impedance matching between the stages, impedance matching is possible only with L13, and L14 and C14 are not always necessary. L14 and C14 may be adjusted according to the specifications of the high-frequency power amplifier and as necessary. Will be added. L12 is a distributed constant line composed of, for example, a microstrip line or a stripline, which constitutes a bias circuit for supplying a DC current for output and a drain (output electrode) of the high-frequency power amplifier Q11 in the preceding stage;
Reference numeral 17 denotes an inductor connected in series to the distributed constant line L12, and is set to a length and an inductance such that the combined reactance of the distributed constant line L12 and the inductor L17 functions as a reactance component of a part of the interstage matching circuit. Have been.

The impedance of the distributed constant line L12 can be set to a length of a quarter wavelength of the fundamental frequency so that it looks infinite as an impedance, or it can be shorter than a quarter wavelength of the fundamental frequency. Also, instead of setting the length so that it is negligibly large from the viewpoint of the circuit impedance, such as 10 times or more the impedance at the fundamental frequency of the circuit, the impedance at the fundamental frequency of the circuit What is necessary is just to set it to a required value according to the design specification of the circuit within a range that can not be ignored and influences.

In this example, an inductor L17 is connected in series to the power supply side of the distributed constant line L12. By changing the inductance of the inductor L17, the impedance of the higher harmonic wave is changed to form an interstage matching circuit. Can be controlled.

Further, a series resonance circuit is constituted by the inductance of the inductor L17 and the capacitance component of the distributed constant line L12 to which the inductor L17 is connected in series, and the series resonance frequency is changed to an arbitrary higher-order harmonic of the fundamental frequency. By adjusting to the above, a resonance point is obtained for any higher-order harmonic of the fundamental frequency.

C17 and C18 are bypass capacitors for alternating current grounding. A bias circuit E enclosed by a dashed line in the figure is formed by a bypass capacitor C17, an inductor L17, and a distributed circuit L12 in which the inductor is connected in series to form a resonance circuit having a harmonic control function. Has formed.

According to such a high-frequency power amplifier of the present invention, the bias circuit E is provided with an arbitrary fundamental frequency by the resonance circuit section constituted by the distributed constant line L12 and the inductor L17 connected in series to the distributed constant line L12. Since it has a resonance point with respect to the higher-order harmonic, the impedance with respect to any higher-order harmonic as viewed from the high-frequency power amplifier unit Q11 in the preceding stage to the subsequent stage appears to be 0 and is grounded.

Here, since the inductance of the inductor L17 can be adjusted only by replacing the inductor, an arbitrary resonance point can be set by the resonance circuit section, whereby fine adjustment of the resonance point can be easily and accurately performed. Can be.

In addition, since any harmonic of the fundamental frequency can be removed without adding another harmonic control circuit, an extremely small high-frequency power amplifier can be obtained.

Next, FIG. 2A shows an example of the configuration of a pre-stage bias circuit of a high-frequency power amplifier according to the present invention, comprising a distributed constant line and an inductor connected in series to the distributed constant line.
To (c).

FIG. 2A is a circuit diagram showing a bias circuit section having the same configuration as the bias circuit section E of the preceding stage shown in FIG. In the figure, L22 is a distributed constant line composed of, for example, a strip line or a microstrip line. L27 is an inductor connected in series to the power supply side of the distributed constant line L22. Thereby, the distributed constant line L
The inductance of an inductor L27 connected in series with 22;
Distributed constant line L22 to which inductor L27 is connected in series
Are set so as to have a resonance point with respect to any higher harmonic of the fundamental frequency. C27 is a bypass capacitor similar to C17.

FIG. 2B is a plan view showing a bias circuit section having another configuration. In the figure, L32a and L32b are distributed constant lines similar to the distributed constant line L22, respectively.
It is formed as two distributed constant lines, and an inductor L37 is connected in series between them.
C37 is the same bypass capacitor as C17.

FIG. 2C is a plan view showing a bias circuit portion having still another configuration. In the figure, L42 is a distributed constant line similar to the distributed constant line L22, and an inductor L47 is connected in series on the high-frequency power amplifier side in the preceding stage. C47 is a bypass capacitor similar to C17.

As described above, the inductor connected in series to the distributed constant line in the bias circuit may be connected at any position before or after the distributed constant line when viewed from the interstage matching circuit side, or between the distributed constant lines. Absent.

In any case of FIG. 2, an arbitrary higher-order harmonic of the fundamental frequency is obtained by the inductance of the inductor connected in series with the distributed constant line and the capacitance component of the distributed constant line in the portion connected in series with the inductor. It is set to have a resonance point for the wave.

As the inductor in the bias circuit at the preceding stage of the high-frequency power amplifier of the present invention, for example, an insulating material is sandwiched between two electrodes, which is often used in a high-frequency circuit, and a conductor is wound around the surface of the insulating material. By using a chip inductor on which a line pattern is printed in a thin film, the inductance can be easily fine-tuned by arranging it on the surface of the substrate of the high-frequency power amplifier, and thereby the resonance point can be finely adjusted. In other words, in order to adjust the inductance of the inductor to set the resonance point of the resonance circuit portion to a desired value, for example, the inductor may be replaced with an inductor having a different inductance, or the inductance may be adjusted using a variable inductance inductor. Is also good.

Next, FIGS. 3 (a) and 3 (b) show a perspective view, an exploded perspective view and a sectional view, respectively, of a practical example of the circuit configuration of the substrate of the bias circuit in the preceding stage of the high-frequency power amplifier of the present invention. Indicated by

In FIG. 3A, B1 is a substrate, L52 is a microstrip line as a distributed constant line, L57 is a chip inductor, and the bias circuit E in FIG.
Is formed on the surface layer of the substrate. In this example, the impedance of the harmonic is changed by changing the inductance of the chip inductor L57.
The interstage matching circuit can be controlled.

In FIG. 3B, B11 is a substrate,
L62 is a strip line as a distributed constant line, L67 is a chip inductor, H1 is a through conductor such as a through-hole conductor or a via conductor for electrically connecting the distributed constant line L62 and the chip inductor L67, and the bias circuit shown in FIG. This is a case where the distributed constant line L12 of the portion E is formed in the inner layer of the substrate. As described above, by changing the inductance of the chip inductor L67 on the surface of the substrate instead of adjusting the distributed constant line L62 which cannot be adjusted in length because the layer is internally formed on the substrate, the impedance of the harmonic is changed and the interstage matching is performed. The circuit can be controlled.

As in these examples, by mounting only one chip inductor L57 / L67 for each bias circuit on the substrates B1 and B11, it is possible to adjust the impedance of the harmonic and to reduce the size. A high frequency power amplifier that can meet the requirements can be configured.

[0048]

According to the high frequency power amplifier of the present invention,
A distributed constant line and an inductor connected in series to the distributed constant line as a pre-stage bias circuit connected to the output electrode of the high-frequency power amplifier of the previous stage and supplying a direct current to the high-frequency power amplifier of the previous stage. An inductor having a combined reactance component necessary to function as a part of the interstage matching circuit due to the length of the distributed constant line and the inductance of the inductor, and the distributed constant line and the inductor connected in series to the distributed constant line And a series resonance circuit having a series resonance frequency having a resonance point with respect to the higher harmonic of the fundamental frequency. Function as a part of the interstage matching circuit while achieving the original purpose of supplying Impedance matching for the fundamental frequency and any higher harmonics of the high-frequency signal viewed from the input electrode on the subsequent stage can be achieved, and at least for the fundamental frequency viewed from the input electrode of the subsequent high-frequency power amplifier on the input stage. Impedance matching can be achieved, and it also functions as a harmonic control circuit that can remove an arbitrary higher-order harmonic from a high-frequency signal input to the subsequent stage. As a result, there is no need to add a harmonic control circuit as a separate circuit, and a high-frequency power amplifier having a harmonic control function capable of responding to a demand for further miniaturization is obtained.

Further, in this bias circuit, the inductance component of the inductor and the inductance component / capacitance component of the distributed constant line can be easily and accurately adjusted by adjusting the inductance of the inductor and the length of the distributed constant line, respectively. Because it is possible, it is possible to easily adjust the resonance point for any higher harmonic of the fundamental frequency.

Further, even when the distributed constant line forming the bias circuit is formed as an inner layer on the multilayer wiring board, the inductor connected in series with the distributed constant line can be easily replaced with a small chip inductor, etc. Can be changed, and the interstage matching circuit can be controlled.

Furthermore, a high-frequency power amplifier having a harmonic control function can be constructed without mounting a harmonic control circuit simply by mounting one inductor on the substrate for each bias circuit. It becomes a high-frequency power amplifier that can respond to the demands for conversion.

As described above, according to the present invention, the control of the impedance with respect to the higher-order harmonic of the fundamental frequency of the high-frequency signal in the interstage matching circuit in the high-frequency power amplifier using the two-stage high-frequency power amplifier section. It is not necessary to add a circuit for controlling the impedance with respect to the higher-order harmonics as viewed from the high-frequency amplifier of the preceding stage and the impedance with respect to the higher-order harmonics as viewed from the subsequent high-frequency power amplifier as a separate circuit. Thus, a high-frequency power amplifier having a harmonic control function capable of responding to a demand for miniaturization of a semiconductor device has been provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an example of a circuit configuration of a high-frequency power amplifier according to the present invention.

FIGS. 2A to 2C are circuit diagrams each showing a configuration example of a pre-stage bias circuit of a high-frequency power amplifier according to the present invention.

FIGS. 3A to 3C are perspective views each showing a configuration example of a pre-stage bias circuit of a high-frequency power amplifier according to the present invention.
It is an exploded perspective view and a sectional view.

FIG. 4 is a circuit diagram showing an example of a circuit configuration of a conventional high-frequency power amplifier.

[Explanation of symbols]

Q11 、 Q12 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ High frequency power amplifier E ・ ・ ・ ・ ・ ・ ・ ・ ・.Bias circuits L17, L27, L37, L47, L57, L67 ... Inductors L12, L22, L32a, L32b, L42, L52, L62 ... Distributed constant lines

Claims (1)

[Claims] 1. A high-frequency power amplifying section having a two-stage configuration for amplifying a high-frequency input signal supplied to an input electrode and outputting it as a high-frequency output signal from an output electrode; An input matching circuit for matching the input impedance to the fundamental frequency of the high-frequency input signal, inserted between the output electrode of the high-frequency power amplifier of the previous stage and the input electrode of the high-frequency power amplifier of the subsequent stage, An interstage matching circuit comprising a distributed constant line for impedance matching between the two-stage high-frequency power amplifiers, an output matching circuit connected to the output electrode of the subsequent high-frequency power amplifier, A distributed constant line connected to the output electrode of the high-frequency power amplifier, for supplying a direct current to the high-frequency power amplifier at the preceding stage, and a distributed constant line connected in series to the distributed constant line; A first-stage bias circuit including an inductor; and a second-stage bias circuit connected to the output electrode of the second-stage high-frequency power amplifier and including a distributed constant line for supplying a DC current to the second-stage high-frequency power amplifier. The first-stage bias circuit includes impedance matching with respect to a fundamental frequency and a higher-order harmonic of the high-frequency input signal as viewed from the output electrode of the first-stage high-frequency power amplifier, and the input of the second-stage high-frequency power amplifier. A synthetic reactance component required to function as a part of the inter-stage matching circuit and a resonance point for the higher-order harmonics caused by the distributed constant line and the inductor for impedance matching as viewed from the electrode to the previous stage. A high frequency power amplifier comprising: