JP5603893B2 - High frequency semiconductor amplifier - Google Patents

Description

  Embodiments described herein relate generally to a high-frequency semiconductor amplifier.

  A high power added efficiency is required for an amplifier used in a radio communication device, a mobile communication base station, a radar device, or the like at a high frequency of 1 GHz or more.

  When the harmonic impedance viewed from the output electrode of the semiconductor amplifying element is close to the open impedance, the power load efficiency can be increased.

  At a frequency of 1 GHz or higher, the output impedance of a semiconductor amplifying element such as a HEMT (High Electron Mobility Transistor) or an FET (Field Effect Transistor) is capacitive in the fundamental wave. In order to efficiently extract the signal amplified by the semiconductor amplifying element, it is necessary for the fundamental wave that the output impedance of the semiconductor amplifying element and the external load are impedance matched.

  For this reason, in order for impedance matching between the semiconductor amplifying element and the external load, it is necessary that the impedance of the fundamental wave viewed from the semiconductor amplifying element to the load side is a desired inductive impedance. On the other hand, in order to increase the power added efficiency, it is necessary that the impedance viewed from the semiconductor element to the load side in the second harmonic is in the vicinity of the open impedance.

  If a high-order harmonic processing circuit using a stub is provided in the vicinity of the chip in order to make the impedance viewed from the semiconductor amplifying element at the second harmonic close to the open impedance, a matching circuit is provided via the high-order harmonic processing circuit. Cascade connection increases insertion loss and narrows the bandwidth.

JP 2009-207060 A Japanese Patent Laid-Open No. 6-204764

  Provided is a high frequency semiconductor amplifier capable of easily realizing high power added efficiency and a wide band.

The high-frequency semiconductor amplifier according to the embodiment includes a semiconductor amplifying element, an input matching circuit, and an output matching circuit. The high-frequency semiconductor amplifier has an output terminal connected to an external load and a predetermined frequency band. The semiconductor amplifying element has an input electrode and an output electrode, and has a capacitive output impedance in the frequency band. The input matching circuit is connected to the input electrode. The output matching circuit includes a bonding wire and a first transmission line. In the output matching circuit, the bonding wire has a first end and a second end opposite to the first end, and the first end is connected to the output electrode. Connected and the second end is connected to one end of the first transmission line. The first transmission line has a first characteristic impedance and a first electrical length that is 90 degrees or less at an upper limit frequency of the frequency band. In the fundamental wave, the output matching circuit matches the capacitive output impedance of the semiconductor amplifying element and the impedance of the external load, and sees the output matching circuit in which the external load is connected to the semiconductor amplifying element. The harmonic impedance has a frequency locus that approaches the open impedance while maintaining inductivity.

It is a schematic diagram which shows the structure of the high frequency semiconductor amplifier concerning 1st Embodiment. 2A is an impedance diagram when the load side is viewed from the first reference plane, and FIG. 2B is an impedance diagram when the load side is viewed from the second reference plane. It is a graph explaining a frequency band. It is a schematic diagram which shows the structure of the high frequency semiconductor amplifier circuit concerning 2nd Embodiment. 5A is an impedance diagram viewed from the first reference plane on the load side, FIG. 5B is an impedance diagram viewed from the third reference plane, and FIG. 5C is an impedance diagram viewed from the second reference plane. . It is a schematic diagram which shows the structure of the high frequency semiconductor amplifier concerning 3rd Embodiment. 7A is an impedance diagram viewed from the first reference plane on the load side, FIG. 7B is an impedance diagram viewed from the third reference plane, FIG. 7C is an impedance diagram viewed from the fourth reference plane, FIG. (D) is the impedance figure seen from the 2nd reference plane.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the configuration of the high-frequency semiconductor amplifier according to the first embodiment.
The high-frequency semiconductor amplifier has an input terminal 10, an input matching circuit 12, a semiconductor amplifying element 14, an output matching circuit 20, and an output terminal 18, and is housed in a package, for example. A DC circuit that supplies a voltage to the semiconductor amplifying element 14 is omitted. It is assumed that the external load is Z _L (Ω) when viewed from the output terminal 18. Z _L can be set to 50Ω, for example.

  The input matching circuit 12 is a matching circuit for the input impedance of the semiconductor amplifying element 14 in the fundamental wave.

  The semiconductor amplifying element 14 may be a GaAs FET, a GaAs HEMT (High Electron Mobility Transistor), a GaN HEMT, or the like. For example, when a GaN HEMT using a wide band gap material is used, the breakdown voltage can be increased, and a high output can be obtained in a wavelength range from microwave to millimeter wave.

  When the harmonic impedance on the load side is sufficiently high as viewed from the output electrode (not shown) of the semiconductor amplifying element 14, it can be operated with high power added efficiency. In other words, the output matching circuit 20 matches the output impedance of the semiconductor amplifying element 14 in the fundamental wave while maintaining a high impedance with respect to the harmonics. The first embodiment includes an output matching circuit 20 that increases the impedance of the second harmonic among the harmonics. The output impedance Zout of the semiconductor amplifying element 14 can be obtained, for example, by measuring the impedance during operation.

In the configuration of FIG. 1, the external load Z _L is connected to the output terminal 18 of the output matching circuit 20. In the first embodiment, the output matching circuit 20 includes a bonding wire 15 and a first impedance conversion circuit 16. The first impedance conversion circuit 16 including the first transmission line can be, for example, a microstrip line having a characteristic impedance Z _C1 and an electrical length L1. The electrical length of the microstrip line, the upper limit frequency f _H of the band of the amplifier is greater than 0 degrees and 90 degrees or less.

  The electrical length L is obtained by the following equation. However, in FIG. 1, the position bonded by the wire from the output electrode of the semiconductor amplifying element 14 is the first reference plane P <b> 1, so that the effective transmission line length M is the physical length of the first impedance conversion circuit 16. Slightly shorter than the length.

L = 360 ° × M / λeff
Where M: effective transmission line length λeff: effective wavelength at a given frequency

  The output electrode of the semiconductor amplifying element 14 and the first impedance conversion circuit 16 are connected by a bonding wire 15. On the line pattern of the first impedance conversion circuit 16, the bonding position is defined as a first reference plane P1 when the load side impedance is viewed. Further, the bonding position on the output electrode of the semiconductor amplifying element 14 is set as a second reference plane P2 when the impedance on the load side is viewed.

2A is an impedance diagram when the load side is viewed from the first reference plane, and FIG. 2B is an impedance diagram when the load side is viewed from the second reference plane.
In the present specification, Smith diagram denote the normalized impedance to the characteristic impedance Z _CC and 3 [Omega]. That is, the normalized impedance z with respect to the impedance Z (= R + jX) is expressed by the following equation.

z = Z / Z _CC = (R + jX) / Z _CC = r + jx

As shown in FIG. 2A, the load impedance is indicated by z _L and the characteristic impedance of the first impedance conversion circuit 16 is indicated by z _{C1 on} the impedance diagram.

The impedance viewed from the load side draws a clockwise impedance locus along the dot line as the load leaves. In a first embodiment, the first impedance conversion circuit 16 is larger than 0 degree is an electrical length L1 of the upper limit frequency f _H of the frequency band, and 90 degrees or less. Therefore, in the frequency band f _L (lower limit) to f _H (upper limit), the fundamental wave impedance z _P1 viewed from the first reference plane P1 on the load side is f _H (upper limit) as shown in FIG. It is converted to the vicinity of the real axis (x = 0) having the same resistance value as the output impedance of the semiconductor amplifying element. Further, the in capacitive _{f L} (lower limit) ~f _H (upper limit). Further, the second harmonic impedance _zP12 is inductive.

Further, in FIG. 2B, when the inductance of the bonding wire 15 is added,
Fundamental wave impedance _{z P2} viewed the load side of the frequency f is the fundamental wave impedance _{z P1} in the first reference plane P1, becomes plus 2 [pi] f × Lw / ZCC comprising reactance due to the inductance Lw of the bonding wire 15, induced The output impedance zout of the semiconductor amplifying element 14 can be matched while turning to.

The fundamental wave impedance _{z P2} seen the load _{side, z} P2 = zout ^{* (*} denotes a complex conjugate) and a. zout because determined by the semiconductor amplifying element 14, by appropriately selecting the characteristic impedance Z _C1 and an electrical length L1, it is possible to approximate the fundamental wave impedance z _P2 to the output impedance zout ^*.

At this time, the second harmonic impedance z _P22 is obtained by adding a reactance component of 4πf × Lw / Z _CC to the second harmonic impedance z _P12 maintained inductive on the first reference plane P1, so that the open impedance ( (Infinite impedance).

  Even if a stub circuit is provided in the vicinity of the semiconductor amplifying element 14, the impedance viewed from the load side can be brought close to the open impedance. However, in this case, the insertion loss increases. In addition, the fundamental wave impedance is lower than the chip end face of the semiconductor amplifying element, and it may be difficult to match the fundamental wave impedance over a wide band. On the other hand, in the first embodiment, broadband matching is possible while suppressing an increase in insertion loss.

FIG. 3 is a graph for explaining the power added efficiency of the high-frequency semiconductor amplifier according to the first embodiment.
The frequency band is, for example, any range within 1 to 20 GHz. Output matching circuit 20, is consistent with respect to the fundamental wave, and when a high impedance close to the open impedance to the second harmonic, power between a lower limit frequency f _L of the frequency band, and the upper limit frequency f _H, Use frequency band with high additional efficiency can be obtained.

In the first embodiment, the upper limit frequency f _H, and the electrical length L1 of the first impedance conversion circuit 16 is 90 degrees or less. If the second harmonic impedance moves away from the open impedance, the second harmonic component that leaks without being reflected by the semiconductor amplifying element increases, and the power added efficiency decreases as indicated by the broken line.

FIG. 4 is a schematic diagram showing the configuration of the high-frequency semiconductor amplifier circuit according to the second embodiment.
The output matching circuit 20 according to the second embodiment includes a bonding wire 15, a first impedance conversion circuit 16, and a second impedance conversion circuit 21 including a second transmission line. The second impedance conversion circuit 21 has a characteristic impedance Z _C2 (Z _C1 <Z _C2 <Z _L ) and an electrical length L2 of greater than 0 degrees and 90 degrees or less.

5A is an impedance diagram viewed from the third reference plane on the load side, FIG. 5B is an impedance diagram viewed from the first reference plane, and FIG. 5C is an impedance diagram viewed from the second reference plane. . In FIG. 5A, the characteristic impedance Z _C2 of the second impedance conversion circuit 21 can be made higher than the characteristic impedance of the first impedance conversion circuit 16 in the first embodiment.

In FIG. 5B, the characteristic impedance Z _C1 (Z _C1 <Z _C2 <Z _L ) of the first impedance conversion circuit 16 can be set lower than the characteristic impedance of the first impedance conversion circuit 16 in the first embodiment. . The fundamental wave impedance z _P1 viewed from the first reference plane P1 on the load side is converted to the vicinity of the real axis (x = 0) having the same resistance value as the output impedance of the semiconductor amplifying element 14. Further, second harmonic impedance _{z P12} is induced is maintained.

By using an impedance conversion circuit of a multi-stage, as shown in FIG. 5 (c), the fundamental wave impedance z _P2 whose inductance seen the load side from the second reference plane P2 that applied the bonding wire 15, the frequency band f _L ~f The change range of the impedance locus at _H becomes narrow, and matching with the output impedance zout of the semiconductor amplifying element 14 becomes easy. For this reason, the frequency characteristic of the gain can be made flatter. Even with the impedance conversion circuit of a multi-stage, by maintaining the first reference plane P1 to second harmonic impedance z _P12 viewing the load side to the inductive, second harmonic impedance z _P22 is the inductance of the bonding wire 15 Since it is added, it can be brought closer to the open impedance, and the power added efficiency can be further increased.

  The suppression effect of the second harmonic depends on the electrical length L1 of the first impedance conversion circuit 16 and the electrical length L2 of the second impedance conversion circuit 21, respectively. Table 1 shows the dependency.

For each case, the second electrical length L2 in the lower limit frequency f _L, the reflection coefficient of the fundamental wave in the third reference plane P3 gamma, the reflection coefficient of the second harmonic of the first reference plane P1 gamma, the first electrical The length L1 and the reflection coefficient Γ of the second harmonic wave on the second reference plane P2 are shown.

In an ideal case, the upper limit frequency _{f H,} the second electrical length L2 is 90 degrees, the first electrical length L1 is 90 degrees. At this time, the band ratio is 20% at the lower limit frequency _{f L,} the second electrical length L2 is 73 degrees, the first electrical length L1 is 73 degrees, a. In the third reference plane P3, the reflection coefficient Γ of the fundamental wave is 0.56 or less, the reflection coefficient Γ of the second harmonic wave is 0.84 or more, and the reflection coefficient Γ of the second harmonic wave is the reflection coefficient Γ of the fundamental wave. Is much larger than. Further, in the second reference plane P2, the reflection coefficient Γ of the second harmonic is as high as 0.9 or more, which indicates that it is close to the open impedance as viewed from the semiconductor amplifying element 14.

Case 1 is at the upper limit frequency _{f H,} degrees a second electrical length L2 74, 85 degrees the first electrical length L1, is. At this time, if the band ratio is 20% at the lower limit frequency _{f L,} the second electrical length L2 is 60 degrees, the first electrical length L1 is 69 degrees, a. In the third reference plane P3, the reflection coefficient Γ of the fundamental wave is 0.71 or less, the reflection coefficient Γ of the second harmonic wave is 0.71 or more, and the reflection coefficient of the second harmonic wave is the same as the reflection coefficient of the fundamental wave. It is. Further, in the second reference plane P2, the reflection coefficient Γ of the second harmonic is as high as 0.9 or more, which indicates that it is close to the open impedance as viewed from the semiconductor amplifying element 14.

Case 2 is the upper limit frequency _{f H,} degrees a second electrical length L2 44, the first electrical length L1 88 degrees, and. At this time, the band ratio is 20% at the lower limit frequency _{f L,} the second electrical length L2 is 36 degrees, the first electrical length L1 is 72 degrees. In the third reference plane P3, the reflection coefficient Γ of the fundamental wave is 0.81 or less, the reflection coefficient Γ of the second harmonic is about 0.37 or more, and the reflection coefficient of the second harmonic is higher than the reflection coefficient of the fundamental wave. Is also getting smaller. In the second reference plane P2, the reflection coefficient Γ of the second harmonic is about 0.58.

In the third reference plane P3, in Case 1, the maximum value in the band of the reflection coefficient Γ of the fundamental wave is substantially equal to the minimum value in the band of the reflection coefficient of the second harmonic wave. On the other hand, in case 2, the reflection coefficient Γ of the second harmonic is smaller than the reflection coefficient Γ of the fundamental wave. That is, the second electrical length L2 is more preferably 60 degrees or more at the lower limit frequency f _L. Since it is not easy to increase the reflection coefficient once lowered, it is preferable to always keep the reflection coefficient Γ of the second harmonic wave large.

FIG. 6 is a schematic diagram showing the configuration of the high-frequency semiconductor amplifier according to the third embodiment.
The output matching circuit 20 of the third embodiment includes a bonding wire 15, a first impedance conversion circuit 16, a second impedance conversion circuit 21, and a third impedance conversion circuit 22 including a third transmission line. . The third impedance conversion circuit 22 has a characteristic impedance of Z _C3 (Z _C1 <Z _C2 <Z _C3 <Z _L ) and an electrical length L3 of greater than 0 degrees and 90 degrees or less.

  7A is an impedance diagram viewed from the fourth reference plane on the load side, FIG. 7B is an impedance diagram viewed from the third reference plane, FIG. 7C is an impedance diagram viewed from the first reference plane, FIG. (D) is the impedance figure seen from the 2nd reference plane.

In FIG. 7 (b), the fundamental wave impedance z _P3 viewing the load side from the third reference plane P3 is converted into the vicinity of the central portion of the impedance Figure. In addition, the second harmonic impedance _zP32 is maintained inductive.

In FIG. 7 (c), the fundamental wave impedance z _P1 viewing the load side from the first reference plane P1 is the real axis (x = 0) of the same resistance value and the output impedance of the semiconductor amplifying element 14 can be the neighborhood. Further, second harmonic impedance _{z P12} is induced is maintained.

By using a multi-stage impedance conversion circuit, as shown in FIG. 7D, the fundamental wave impedance z _P2 viewed from the second reference plane P2 to which the inductance of the bonding wire 15 is added is seen in the frequency band f _{L to} f. The change range of the impedance locus at _H becomes narrow, and matching with the output impedance zout of the amplifying element 14 becomes easy. For this reason, the frequency characteristic of the gain can be made flatter. Even with the impedance conversion circuit of a multi-stage, by maintaining the first reference plane P1 to second harmonic impedance z _P12 viewing the load side to the inductive, second harmonic impedance z _P22 is the inductance of the bonding wire 15 Since it is added, it can be brought closer to the open impedance, and the power added efficiency can be further increased. In the third embodiment, as in the second embodiment, and more preferably to 60 degrees or more in a third impedance lower limit frequency f _L of the electrical length L3 of the conversion circuit 22 side of the output terminal 18.

  In general, a class F amplifier has a high-order harmonic processing circuit in which matching circuits are connected in cascade on the output side in the vicinity of the semiconductor amplifying element, and power is added by confining the high-order harmonic components in the semiconductor amplifying element. Increases efficiency.

  On the other hand, in the first to third embodiments, an impedance conversion circuit composed of a transmission line is cascaded on the output side of the semiconductor amplifying element 14 without using a high-order harmonic processing circuit. In this case, the fundamental wave impedance and the double wave impedance can be converted into desired ranges by changing the characteristic impedance and the electrical length of the transmission line, respectively. For this reason, it is possible to match the fundamental impedance to the output impedance zout of the semiconductor amplifying element 14 while keeping the second harmonic impedance open. As a result, the high-frequency semiconductor amplifier can sufficiently ensure the required power added efficiency while having a simple structure.

  According to the first to third embodiments, a high-frequency semiconductor amplifier capable of realizing high power added efficiency and a wide band is provided. Such a high-frequency semiconductor amplifier can be widely used in a radio communication device, a mobile communication base station, a radar device, etc. at a high frequency of 1 GHz or more.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

12 input matching circuit, 14 semiconductor amplifying element, 15 bonding wire, 16 first impedance conversion circuit (transmission line), 18 output terminal, 20 output matching circuit, 21 second impedance conversion circuit (transmission line), 22 third impedance conversion Circuit (transmission line), Z _L external load, Z _C1 , Z _C2 , Z _C3 (transmission line) characteristic impedance, L1, L2, L3 electrical length, f _L lower limit circumference, f _C center frequency, f _H upper limit frequency

Claims (5)

A high-frequency semiconductor amplifier having an output terminal connected to an external load and having a predetermined frequency band,
A semiconductor amplifying element having an input electrode and an output electrode and having a capacitive output impedance in the frequency band;
An input matching circuit connected to the input electrode;
An output matching circuit having a bonding wire and a first transmission line, wherein the bonding wire has a first end and a second end opposite to the first end. The first end is connected to the output electrode and the second end is connected to one end of the first transmission line, and the first transmission line is a first characteristic impedance. And an output matching circuit having a first electrical length of 90 degrees or less at the upper limit frequency of the frequency band;
With
The output matching circuit matches the capacitive output impedance of the semiconductor amplifying element and the impedance of the external load in a fundamental wave ,
The high frequency semiconductor amplifier having a frequency locus in which the second harmonic impedance viewed from the semiconductor amplifying element to the output matching circuit to which the external load is connected approaches the open impedance while maintaining inductivity . The output side matching circuit further includes a second transmission line having a second characteristic impedance higher than the first characteristic impedance and a second electrical length that is 90 degrees or less at the upper limit frequency,
The high-frequency semiconductor amplifier according to claim 1, wherein the second transmission line is provided between the first transmission line and the output terminal.   The high-frequency semiconductor amplifier according to claim 2, wherein the second electrical length is 60 degrees or more at a lower limit frequency of the frequency band. The output matching circuit further includes a third transmission line having a third characteristic impedance higher than the second characteristic impedance and a third electrical length that is 90 degrees or less at the upper limit frequency;
The high-frequency semiconductor amplifier according to claim 2, wherein the third transmission line is provided between the second transmission line and the output terminal.   The high-frequency semiconductor amplifier according to claim 4, wherein the third electrical length is 60 degrees or more at a lower limit frequency of the frequency band.

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