JP2953394B2 - Design method of high frequency power amplifier circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matching circuit required for a microwave power amplifying circuit for realizing class F operation using a semiconductor device, and more particularly to a matching circuit in consideration of control of a second harmonic. .

[0002]

2. Description of the Related Art In a radio transmitter, most of the power consumption is consumed by a high output power amplifier. Energy that is not converted to transmission power is consumed as heat. When the efficiency of the high output power amplifier is low, the amount of heat generated increases,
In order to maintain the performance of the device, a radiator corresponding to the increased heat value must be installed. In addition, operating a semiconductor device at a high temperature shortens its life and lowers its reliability. In particular, when the heat radiator cannot be enlarged even in the space space where the exhaust heat environment is severe or in the terrestrial use, it becomes a major problem in the structural design.

[0003] For these reasons, it is necessary to increase the efficiency of the amplifier and to suppress the heat generation. Various circuits have been studied for increasing the efficiency of the amplifier, and a class F amplifier is one of them.

In the class F amplifier, the output terminal of the amplifying element is opened to the fundamental wave and odd-order harmonics of the input signal, and short-circuited to the even-order harmonics, so that even-order harmonics generated inside the amplifier are short-circuited. The power consumption of the even-order harmonic is almost eliminated by canceling out the reflected wave from the point.

FIGS. 1 to 3 are block diagrams of a conventional class F amplifier. 1 is a semiconductor amplifying element, 2 is an output terminal of the amplifying element, 3 is a fundamental wave matching circuit, 4 is a harmonic control circuit that is short-circuited by the 2nth harmonic of the fundamental wave, such as a short stub or open stub. It is composed of a distributed constant circuit by strip lines.

FIG. 1 shows a short circuit of the harmonic control circuit.
Shown below is the case of realizing with a stub. If the harmonic control circuit is made of a short stub, it is necessary to provide a capacitor 5 at the tip of the stub as shown in FIG. This capacitor and stub are usually connected by a gold wire, but this gold wire acts as an inductor, and parasitic components are generated between the gold wire and the capacitor, and between the gold wire and the stub, so the operation analysis of the short stub is complicated. Becomes

Therefore, in this configuration, the fundamental wave is infinite,
It is not so easy to realize an impedance that is short-circuited by even-order harmonics. Further, in the even-order harmonics, the stub length lambda _0/4 with respect to the fundamental wave; for a (lambda ₀ the wavelength of the fundamental wave), increases as compared to the open stub is difficult miniaturization.

[0008] FIGS. 3, in case of realizing the harmonic control circuit in an open stub, the fundamental wave λ _0/8 (λ
₀ ; wavelength of the fundamental wave). When making an open stub, parasitics do not occur because without a capacitor, a small since the length of the stub is lambda _0/8 with respect to the fundamental wave. Therefore, it is preferable to use an open stub rather than a short stub to make the short-circuit point.

This open stub becomes a capacitive load due to the fundamental wave.
In this case, the matching circuit for the fundamental wave deviates from the design value by this amount of capacitance. However, for this shift,
There is no literature that describes what phase should be used for designing. Therefore, the circuit design is easier in the configuration of FIG. 3 in which the open stub is connected after the fundamental wave matching circuit.

[0010] Conventionally, the same configuration as FIG. 3, provided fundamental matching circuit consisting of lambda _0/4 on the output side of the semiconductor element,
Configured whereby a harmonic control circuit comprising a parallel resonance circuit which resonates at the fundamental wave f ₀ to the output terminal of the fundamental wave matching circuit is known. In this configuration, the parallel resonance circuit is opened by the fundamental wave, short-circuited by the second harmonic, and short-circuited by the third harmonic, thereby realizing class F operation. When using a distributed constant circuit lambda _0/4 as a fundamental wave matching circuit, since the fundamental wave matching circuit is lambda / 2 with respect to the second harmonic, the output end of the as fundamental matching circuit is a short circuit If so, the input terminal is also short-circuited.

However, regardless of whether the harmonic control circuit is connected to the input terminal or the output terminal of the fundamental wave matching circuit, from the connection point to the actual output terminal of the FET, a gold wire or the short-circuit portion is required. Strip line and so on, FE accurately
This does not mean that the output terminal of the T element is short-circuited.

[0012]

SUMMARY OF THE INVENTION Based on such a viewpoint, the present invention exists between a short-circuit point of a harmonic control circuit and an actual output terminal of a semiconductor device (FET), which has not been considered in the prior art. Focusing on the phase difference, adjust the length (phase) of the transmission line from the output end of the semiconductor element to the short-circuit point so that the second harmonic is short-circuited at the actual output end of the semiconductor element (FET). And the second generated inside the semiconductor element
The harmonic wave and the reflected wave from the short-circuit point just cancel each other.

[0013]

According to a method of designing a microwave power amplifier circuit of the present invention, a short-circuit point for a second harmonic is provided at an input terminal or an output terminal of an output-side fundamental wave matching circuit of a semiconductor device. In a microwave power amplifying circuit for connecting an open stub and inverting the phase of a reflected wave from the short-circuit point in the semiconductor element to suppress the second harmonic of the semiconductor element, the open stub and the transmission line (microstrip. A plurality of T-shaped strip lines (stub substrates) having different coupling points with the output end of the package including the semiconductor and the output side. By individually connecting the input terminals of the fundamental wave matching circuit or the output terminals of the output side fundamental wave matching circuit one by one and measuring the power efficiency of the amplifier circuit, The T-shaped strip line (stub substrate) having the optimum power efficiency taking into account the effect of stray impedance in the package existing between the conductor element and the short-circuit point is obtained, and the obtained T-shaped strip line is obtained. Wherein a circuit that suppresses the second harmonic is configured in a shape corresponding to the above, and the phase between the output terminal of the package including the semiconductor and the open stub is adjusted so as to have optimal power efficiency. . Further, the semiconductor element is F
ET, and the amplifier circuit is of class F.

[0014]

The microwave power amplifying circuit according to the present invention comprises: an input terminal of an output-side fundamental wave matching circuit of a semiconductor amplifying element;
Alternatively, a harmonic control circuit that short-circuits the second harmonic is connected at the output end so that the second harmonic generated inside the semiconductor amplifying element (FET) and the reflected wave from the short-circuit point cancel each other. By adjusting the reflection phase of the harmonic control circuit, the power efficiency of the semiconductor element can be maximized.

[0016]

1 to 3 show a basic configuration of the present invention. 1 and 2 show a fundamental wave matching circuit 3.
This is an example in which a harmonic control circuit is provided before. FIG.
Using a Ω line (microstrip line) and a short stub, the harmonic control circuit shown in FIGS. 2 to 3 is composed of a 50 Ω line and an open stub.

FIG. 3 shows an example in which a harmonic control circuit (open stub) is provided after the fundamental wave matching circuit 3. The configuration of FIG. 3 is more preferable as the basic configuration of the present invention because the open stub has less influence on the fundamental wave matching circuit than the configuration of FIG.

However, the present invention can be applied not only to FIG. 3 but also to FIG. 1 using a short stub and FIG. 2 using an open stub connected before a fundamental wave matching circuit.

The above basic configuration is conventionally known. However, these conventional examples are correct in principle, but when a microwave power amplifier circuit is specifically made, the power efficiency is not so much improved as compared with a circuit without a second harmonic short circuit. There was a disadvantage.

In an actual microwave power amplifying circuit, a gold wire (lead wire) is provided between a short-circuit point by the harmonic control circuit and an amplifying portion of a semiconductor amplifying element (FET).
Or the presence of a transmission line (strip line), and the second harmonic is not exactly in opposite phase in the amplifying portion of the semiconductor amplifying device (FET) due to the influence of the gold wire or the inductance of the transmission line. It is caused. The reflection phase of the harmonic wave is such that the wave traveling through the 50Ω line is open.
It is determined by the transmission distance before being reflected by the stub and returning to the signal source.

Focusing on this point, as shown in FIG. 4, the present invention provides a T-shaped strip line in which the connection point between the open stub and the microstrip line is changed ((A) and (B) in FIG. 4). ) a plurality making, the T-shaped strip line between the lambda _0/4 microstrip line to form a package and fundamental matching circuit including an FET element, or with the fundamental matching circuit and an output terminal And the power efficiency was measured.

In FIG. 4, 7 to 9 are dielectric substrates, 11
Is a 50Ω microstrip line, 1 is a semiconductor element (FET), 3 and 10 are fundamental wave matching circuits, 12 is an input terminal, 13 is an output terminal, and 14 and 15 are bias circuits.
An open stub is formed in a T-shape on the dielectric substrate 7, and the dielectric substrate 7 is formed as described above in FIG.
As shown in (b), a plurality of samples with different intervals D are prepared, and the power efficiency is measured after various replacements. FIG. 6 shows the result.

The operation of this circuit is as follows. The fundamental wave and the harmonic generated by the semiconductor element become traveling waves and enter the harmonic control circuit. Since the harmonic control circuit has a small insertion loss with respect to the fundamental wave, the fundamental wave is slightly attenuated and most components pass. On the other hand, the harmonic is reflected by the harmonic control circuit and returns to the semiconductor device as a reflected wave. The harmonic traveling wave from the semiconductor element and the reflected wave from the harmonic control circuit cancel each other out when the phase is 180 °, and strengthen each other when the phase difference is 0 °. In order to achieve high efficiency, the phase must be such that the even-order harmonics cancel each other (short), and the phase of the odd-order harmonics strengthens (open).

Since the microwave power amplifying circuit normally operates in class B, it has a half-wave rectified waveform, and the harmonics are only even-order harmonics, and almost no odd-order harmonic components are generated.

FIG. 6 shows a semiconductor device having an output power of 1 W class.
It is an example to which the present invention is applied. In FIG. 6, the vertical axis shows the power efficiency, and the horizontal axis calculates the electrical length of the second harmonic from the output end of the package including the FET element to the short-circuit point, and displays the phase of the second harmonic at the output end of the package. It was done.

As is apparent from FIG. 6, there is an optimum point in the power efficiency using the length (phase) of the transmission line from the output end of the semiconductor element to the short-circuit point as a parameter. This is clearly a gold wire (lead) or a transmission line (strip) between the short-circuit point and the amplifying part of the semiconductor amplifier (FET).
This is due to the fact that the second harmonic is not exactly in opposite phase in the amplifying part of the semiconductor amplifying element (FET) due to the presence of the gold wire or the inductance of the transmission line.

It is considered that the peak value is around -20 ° due to the influence of the lead wire from the FET element in the package to the inner wall of the package. FIG. 5 shows an embodiment in which an open stub is connected after the fundamental wave matching circuit in the same configuration as in FIG. The description of the bias circuit is omitted. With this configuration, an open stub can be provided immediately after the fundamental wave matching circuit, and the overall width of the housing can be reduced.

FIG. 7 shows experimental results of power added efficiency using the input power as a parameter when the harmonic control is not performed and when the harmonic control is performed. However, the harmonic control circuit has an open stub connected to the output side of the fundamental wave matching circuit. In the case of an output power of 1 W class, an amplifier without harmonic control has a maximum power added efficiency of about 62%,
The maximum power added efficiency is 72 in the amplifier with harmonic control.
~ 73% was obtained. However, the maximum output and the linear gain are not related to the presence or absence of harmonic control.

FIG. 8 shows that the output impedance is 10
Experimental results obtained by applying the present invention to a W-class semiconductor device with the same configuration as that of FIG. 7 are shown. As is clear from the figure, similarly to the case of the output power of 1 W class, the power added efficiency is improved by about 10%.

[0030]

According to the present invention, as described above, the second
By connecting a harmonic control circuit, which is a short-circuit point for the harmonic, to the transmission line and adjusting the length (phase) of the transmission line from the semiconductor element to the short-circuit point, the maximum power added efficiency is reduced by the harmonic. A remarkable effect of about 10% improvement as compared with the case where the wave control is not performed was shown.

As described above, power efficiency is improved, power consumption is reduced, heat generation is reduced, thermal design is facilitated, weight is reduced, and the reliability of the semiconductor device is reduced by lowering the temperature of the semiconductor element. Improved. At this time, it was confirmed that the maximum output power and the linear gain did not decrease.

Further, an open circuit is provided as a harmonic control circuit.
When a stub is used, the impedance for the fundamental wave is also kept close to 50Ω, so that there is an advantage that the design of the fundamental wave matching circuit is facilitated.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a conventional class F amplifier, and is a diagram illustrating an example of a basic configuration of the present invention.

FIG. 2 is a diagram showing a configuration of a conventional class F amplifier, and showing another example of a basic configuration of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional class F amplifier and showing an example of a preferred basic configuration of the present invention.

FIG. 4 is a diagram showing an embodiment of a high frequency power amplifier circuit of the present invention.

FIG. 5 is a diagram showing another embodiment of the high-frequency power amplifier circuit of the present invention.

FIG. 6 is a diagram showing experimental results when the present invention is applied to a semiconductor device having an output power of 1 W class.

FIG. 7 is a diagram showing a comparison of power added efficiency when the present invention is applied to a semiconductor device having a 1 W-class output power and when the present invention is not applied.

FIG. 8 is a diagram showing a comparison of power added efficiency when the present invention is not applied to a semiconductor device having an output power of 10 W class.

[Explanation of symbols]

Reference Signs List 1 semiconductor element 2 output terminal of semiconductor element 3 fundamental wave matching circuit 4 harmonic control circuit (short stub) 5 capacitor 6 harmonic control circuit (open stub) 7 length of transmission line from semiconductor element to the short-circuit point (Dielectric substrate) 8-9 Dielectric substrate 10 Basic wave matching circuit 11 50Ω microstrip line 12 Input terminal 13 Output terminal 14, 15 Bias circuit

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H03F 3/60 JOIS

Claims (2)

(57) [Claims] 1. An open stub, which is a short-circuit point for a second harmonic, is connected to an input terminal or an output terminal of an output-side fundamental wave matching circuit of a semiconductor element, and a reflected wave of the semiconductor element from the short-circuit point is connected. The phase of the semiconductor device is
In a microwave power amplifier circuit for suppressing harmonics, the open stub and a transmission line (microstrip
Strip line <br/> down T-shaped with different points of attachment of the line) (stub substrate) a plurality making, the output of the package containing the semiconductor and the T-shaped strip line (stub substrate) by measuring the power efficiency of the amplifier circuit connected to an output terminal or between the output side fundamental matching circuit on the input end of the output side fundamental matching circuit and an end one at individually, with the semiconductor element The semiconductor present between the short-circuit points
T-shaped strip line (star ) with optimum power efficiency taking into account the effect of stray impedance in the body package.
Seeking Breakfast substrate) constitute a suppressing circuit the second harmonic in a shape corresponding to the strip line of the T-shaped found the the output end of the package containing the semiconductor O
Adjust phase between punt stubs for optimal power efficiency
A method for designing a microwave power amplifier circuit, comprising: 2. The method for designing a microwave power amplifier circuit according to claim 1, wherein said semiconductor element is an FET and said amplifier circuit is of class F.