JP2000165115A - Transmission line transducer and power amplifier using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily secure initial impedance and to facilitate fine adjustment of impedance by connecting a coaxial line to be connected nearer to an input terminal of each pattern at input side of first and second transmission lines more away from an output terminal at each pattern at output side. SOLUTION: In a semi-rigid cable 5 on the side of the first transmission line, a central conductor of an end part 5a on the input side is connected with a position closest to the input terminal 9 at a part in the vertical direction of a land pattern 1. An external conductor of the end part 5a on the input side of the semi-rigid cable 5 is connected with the part in the vertical direction of a land pattern 3. The central conductor is connected with the furthest place from an output terminal 10 at a part in the horizontal direction of the land pattern 3 at the end part 5b on the output side of the semi-rigid cable 5. The external conductor at the end part 5b on the output side is connected with a part on the horizontal direction of a land pattern 4 and a semi-rigid cable 6 on the side of the first transmission line is connected with a remote place from the input terminal 9 in comparison with the semi-rigid cable 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line transformer formed according to a method of connecting a plurality of coaxial lines and a power amplifier using the transmission line transformer.

[0002]

2. Description of the Related Art In general, in a high-frequency power amplifier composed of transistors, even when a high-frequency signal is supplied to a transistor as it is, the impedance of a signal source that supplies the high-frequency signal and the impedance of the load as viewed from the input of the transistor. Unless is matched, the traveling wave of the high-frequency signal is reflected at the input end of the transistor, so that only a part of the high-frequency signal is input to the transistor. Therefore, an impedance matching circuit is usually provided before and after the transistor. There are various circuits for this matching circuit, and one of them is a method of converting impedance using a transformer to perform matching. Among these types of transformers, there is a transmission line transformer composed of a transmission line such as a coaxial line such as a semi-rigid cable.

This transmission line transformer usually uses two coaxial lines having a length of λ / 4 and is formed by connecting the center conductor and the outer conductor to each other. λ is the effective wavelength of the high-frequency signal and is obtained by the following equation. λ = λo / √ (ε · μ) (1) where λo is the wavelength [m] of the electromagnetic wave propagating in vacuum, and c / f (c is the speed of light [m / s], f in vacuum) Is determined by the frequency [Hz] of the high-frequency signal. Ε is the dielectric constant of the transmission line, and μ is the magnetic permeability of the transmission line.

Here, a specific example of the transmission line transformer is shown in FIG.
Shown in First, the transmission line transformer shown in FIG.
A transmission line transformer having an impedance ratio of 4: 1 and a coaxial line (here, a semi-rigid cable) 100
And one end of the coaxial line 200 (the left end in the figure)
, The outer conductor of the coaxial line 100 (the hatched portion in FIG.
The same applies hereinafter) to the center conductor 2 of the coaxial line 200 by the wiring a.
01, and the outer conductor of the coaxial line 200 is connected to the center conductor 101 of the coaxial line 100 by the wiring b.

On the other hand, on the other end side (the right end in the figure) of the coaxial lines 100 and 200, the external conductor of the coaxial line 100 and the external conductor of the coaxial line 200 are connected to each other by a wiring c. Thus, the transmission line transformer has an impedance ratio of 4 (one end side): 1 (the other end side).

The transmission line transformer shown in FIG. 7 (b) is a transmission line transformer having an impedance ratio of 9: 1, and is provided at one end (the left end in FIG. 7) of the coaxial lines 150 and 250. The outer conductor of the coaxial line 150 is connected to the one end side center conductor 251 of the coaxial line 250 by a wiring d, and the outer conductor of the coaxial line 250 is connected to a wiring e.
To the center conductor 151 at one end of the coaxial line 150.

On the other hand, at the other end (the right end in the figure) of the coaxial line 150, the outer conductor of the coaxial line 150 is connected to the central conductor 1 at one end of the coaxial line 150 by a wiring f.
51, and similarly, the outer conductor of the coaxial line 250 is connected to the one end side center conductor 251 of the coaxial line 250 by the wiring g. As a result, the impedance ratio becomes 9
(One end side): 1 (Other end side) transmission line transformer.

In general, in a high-frequency power amplifier using a transistor, the output resistance Ro of the transistor decreases as the output power increases, as shown in the following equation. Ro [Ω] = (Vceds−Vsat) ² / Po / 2 (2) where Vceds is the collector-emitter voltage or drain-source voltage [V] of the transistor, and Vsat is the saturation voltage.
[V] and Po are output power [W].

Therefore, normally, when the output power exceeds about 10 watts, the output resistance Ro of the transistor becomes several ohms. On the other hand, since the impedance value of a general power load in a high-frequency circuit is 50Ω, the output resistance Ro of the transistor is one or two digits lower than the impedance of the power load.

As described above, when the difference between the output impedance of the high-frequency power amplifier and the impedance of the power load is remarkable, if the impedance is matched using a matching circuit constituted by the inductance L and the capacitor C, for example, one stage of L In a matching circuit of the type, since the Q value (sharpness) is increased and oscillation is likely to occur, a multistage matching circuit is often used to reduce the Q value of one L and C.
In an actual circuit, about one to three stages are often used for miniaturization. However, if the number of elements is large, there is a problem that the variation of each element and the number of adjustment points increase.

In any case, when the input / output impedance of the transistor is several Ω or less and the Q value of the matching circuit is high, the parasitic reactance of each circuit, the reactance of the matching circuit, the output load impedance, etc. The input impedance and the output impedance of the transistor tend to deviate to the negative resistance region outside the circle of the Smith chart, and the transistor easily oscillates.

As a method of achieving impedance matching while avoiding the multistage matching circuit as described above, there is a method using a quarter-wavelength transmission line. According to this method, between the input / output terminal of the power amplifier and the circuits before and after it,
By inserting a quarter-wavelength transmission line, the impedance Z of the front and rear circuits as viewed from the power amplifier side, or the impedance Z of the power amplifier as viewed from the front and rear circuits, is calculated according to the following equation. Is converted. Z = √ (Zc · Zλ) (3)

In the above equation (3), Zc is the impedance of the circuit (the input or output impedance of the power amplifier or the impedance of the circuit connected to the input or output of the power amplifier), and Zλ is a quarter wavelength. Is the impedance of the transmission line.

[0014] That is, Then, the above-described (3), for example, as shown in FIG. 8, the output impedance Zt is 20Ω transistor Tr, the load resistance Z _L is 50Ω
In the case of, when aligning the two impedance Zλ is a coaxial line of the quarter-wave at 25 [Omega], is inserted between the transistor Tr and the load resistance Z _L. Accordingly, the impedance Z _tL when the load resistance side is viewed from the output of the transistor Tr through the coaxial line is Z _tL = √ (50 · 25) = 35.35Ω from the equation (3). Therefore, the impedance Z _tL becomes lower than 50Ω, and approaches the output impedance Zt of the transistor Tr = 20Ω.

The impedance Z _Lt when the transistor Tr is viewed through the coaxial line from the load resistance side is:
From equation (3), Z _Lt = √ (20 · 25) = 22.36Ω. As a result, the impedance Z _Lt becomes higher than 20Ω and approaches the load resistance Z _L = 50Ω. And
If the impedance cannot be completely matched by this method, an impedance matching circuit constituted by an inductance L and a capacitor C is inserted between the transistor Tr and the coaxial line to adjust each constant strictly. Align.

Furthermore, the impedance between the transistor and the external circuit can be matched by appropriately selecting the characteristic impedance value of the coaxial line used in the transmission line transformer based on the principle described above.

[0017]

The characteristic impedance of the coaxial line shown in FIG. 8 is 25Ω,
The characteristic impedance of a coaxial cable generally distributed and sold is 50Ω or 75Ω. That is, a special coaxial line with a characteristic impedance of 25Ω
It is difficult to obtain, and there is a problem that it is expensive. Therefore, for example, in order to obtain a coaxial line having a characteristic impedance of 25Ω, as shown in FIG. 9, two coaxial cables having a characteristic impedance of 50Ω (here, semi-rigid cables) are connected in parallel. Note that the outer conductors of the two semi-rigid cables shown in FIG. 9 are electrically connected. Thereby, the impedance of the coaxial line can be set to 50 × 50 / (50 + 50) = 25Ω.

However, when a transmission line transformer is formed on a substrate for a high-frequency circuit using a plurality of coaxial lines connected in parallel, the method of attaching the coaxial line to the land pattern provided on the substrate, There is a problem that the impedance of the transmission line transformer fluctuates easily depending on the size and shape of the transmission line transformer. Therefore, it is difficult to obtain a desired impedance in the transmission line transformer, and as a result, there is a problem that it is difficult to perform an adjustment operation when impedance matching between high-frequency circuits is performed.

The present invention has been made in view of such circumstances, and a transmission line transformer and a transmission line transformer capable of easily obtaining an intended impedance and easily fine-adjusting the impedance. It is an object to provide a power amplifier using a transformer.

[0020]

According to a first aspect of the present invention, there is provided a transmission line transformer formed by a method of connecting a plurality of coaxial lines with each other using a plurality of coaxial lines. And a pattern in which four substantially L-shaped patterns, each of which is composed of an input-side pattern and an input-side pattern and an output-side pattern of the second transmission path, are arranged in a substantially cross shape at predetermined intervals on a substrate. Between the pattern and the input / output pattern on the first transmission line side of the land pattern,
And the length between the input / output patterns on the second transmission line side is λ / 4 (λ is the effective wavelength of the input high-frequency signal)
And a plurality of coaxial lines connected at least two each, and a coaxial line connected closer to an input end in each input side pattern in the first and second transmission lines,
Each output side pattern is characterized by being connected far from the output end.

Here, as the above-mentioned coaxial line, a flexible coaxial cable or a semi-rigid cable can be used. The above-mentioned predetermined intervals correspond to, for example, the intervals d1 and d2 shown in FIG. 2 of the embodiment, and generally have the same interval as the width of the land pattern. It is determined not to short circuit.

As described above, the more the coaxial line connected closer to the input end in each input side pattern in the first and second transmission lines, the farther the coaxial line is connected from the output end in each output side pattern. The sum of the distance from the input end of the pattern to the input end of the coaxial line and the distance from the output end of the coaxial line to the output end of the output pattern is almost equal in the path of each coaxial line. And the desired impedance value is easily obtained.

According to a second aspect of the present invention, in the transmission line transformer according to the first aspect, the impedance of the transmission line transformer is adjusted by changing a length of each of the plurality of coaxial lines. Features.

According to a third aspect of the present invention, in the transmission line transformer according to the first or second aspect, the impedance of the transmission line transformer is adjusted by changing a width of each pattern constituting the land pattern. It is characterized by:

[0025] The invention described in claim 4 is the invention according to claims 1 to 3.
In the transmission line transformer according to any one of the above, a miter is provided at an L-shaped right-angled portion in each of the land patterns. Here, the L-shaped right-angled portion in each pattern corresponds to, for example, a portion shown by a dotted line in FIG.

The invention described in claim 5 is the invention according to claims 1 to 3
In the transmission line transformer according to any one of the above, in each of the land patterns, a corner excluding an input end and an output end is formed by a curve. Here, the corners excluding the input end and the output end correspond to, for example, a portion indicated by a dotted line in FIG.

According to a sixth aspect of the present invention, there is provided a semiconductor device having a transistor for amplifying the power of an input high-frequency signal.
6. A high-frequency power amplifier, wherein the transmission line transformer according to claim 1 is provided on each of the input and output sides of the transistor. here,
The transmission line transformer according to any one of claims 1 to 5,
Balun, multiplier, filter, mixer, hybrid (3
It is also applicable to a circuit that has one or more input / output terminals and distributes or combines power to two or more circuits.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a top view showing one embodiment of a transmission line transformer according to the present invention. Also, the transmission line transformer shown in this figure uses two coaxial lines having a characteristic impedance of 50Ω connected in parallel to each other, as shown in FIG.
(The input / output relationship is reversed). Therefore, the transmission line transformer of FIG. 1 has an impedance of 25Ω and an impedance ratio of 1 (input): 9 (output).

In FIG. 1, reference numerals 1, 2, 3, and 4 denote substantially L-shaped land patterns provided on a substrate (not shown), respectively, and a land pattern 1 is an input-side land pattern of the first transmission line. The land pattern 2 is an input land pattern of the second transmission path, the land pattern 3 is an output land pattern of the first transmission path, and the land pattern 4 is an output land pattern of the second transmission path. Also, 5,6
7 and 8 each have a length of λ / 4 (where λ is the aforementioned (1)
(Effective wavelength determined by the formula), and the characteristic impedance is 50Ω. The coaxial lines 5 and 6 are on the first transmission line side, and the coaxial lines 7 and 8 are on the second transmission line side.
Here, a semi-rigid cable is used as the coaxial line.

Reference numeral 9 denotes a first transmission line transformer shown in FIG.
, And an end of the land pattern 1 indicated by an arrow corresponds thereto. Reference numeral 10 denotes an output terminal on the first transmission line side, and a land pattern 3
, The edge indicated by the arrow corresponds to this.
Reference numeral 9 'denotes an input end on the second transmission line side of the transmission line transformer shown in FIG. 1, and an end of the land pattern 2 indicated by an arrow corresponds thereto. 10 'is the second
, And an end of the land pattern 4 indicated by an arrow corresponds to the output end.

Next, the layout, dimensions, and the like of the above-described land patterns 1, 2, 3, and 4 will be described with reference to FIG.
FIG. 2 is a diagram showing only the land patterns 1, 2, 3, and 4 of the transmission line transformer shown in FIG. As shown in this figure, the land patterns 1, 2, 3, and 4 are arranged so as to have a substantially cross shape.

In the figures, the length L1 of the vertical portion and the length L2 of the horizontal portions of the output side patterns 3 and 4 in each land pattern correspond to the outer diameter and the number of coaxial lines attached to each land pattern. It is determined according to. Also,
Since the length L3 of the lateral portions of the input side patterns 1 and 2 is a microstrip line, its impedance depends on the width. Therefore, the length L3 is determined according to the mounting space such as a coaxial cable or a transistor lead.

Further, the width W _T in the width W _L and transverse portions in the longitudinal portion of the land pattern 1, 2, 3 and 4 are both the same size, these widths, the transmission line is basically desired Although it is determined according to the impedance of the transformer, the impedance of the microstrip line structure can be adjusted by changing its width because of the microstrip structure. As a result, the impedance error caused by the mounting position of the coaxial cable or the like and the dielectric protruding from the outer conductor of the coaxial cable to be mounted and the impedance of the inner conductor part deviating from the original coaxial cable impedance is reduced by the microstrip line structure. The correction can be made by changing the width of the land pattern.

Further, the horizontal arrangement distance d1 and the vertical arrangement distance d2 of each land pattern are as follows.
Land pattern not to each other so that a short circuit, and the land pattern width to less susceptible to electromagnetic coupling with each other W _L, W _T
It is desirable to keep the above distance, but it is also determined by mechanical connection factors such as the diameters and materials of the outer conductor and the inner conductor of the coaxial cable. Microstrip lines running in parallel interfere with each other and are called microstrip coupled lines. By setting the length to λ / 4,
It can be used in the same way as one coaxial cable. Note that the impedance in this case is determined by the width of the microstrip line.

Next, land patterns 1, 2, 3, 4
The connection relationship with the semi-rigid cables 5, 6, 7, and 8 will be described with reference to FIGS. First, the semi-rigid cable 5 on the first transmission line side is connected to the input end 5a.
A central conductor (a portion surrounded by a broken line in FIG. 1; the same applies hereinafter) is connected to the input terminal 9 in the vertical portion of the land pattern 1.
Connected to the nearest location. The outer conductor at the input end 5 a of the semi-rigid cable 5 is connected to the vertical portion of the land pattern 3.

On the other hand, at the output end 5 b of the semi-rigid cable 5, the center conductor is connected to the position farthest from the output end 10 in the lateral portion of the land pattern 3. Further, the external conductor at the output side end 5b is connected to a lateral portion of the land pattern 4.

Next, the semi-rigid cable 6 on the first transmission line side is connected at the input side end 6a to a position where the center conductor is further away from the input end 9 than the semi-rigid cable 5 in the vertical portion of the land pattern 1. Have been. The external conductor at the input end 6a is connected to the vertical portion of the land pattern 3.

On the other hand, at the output end 6 b of the semi-rigid cable 6, the center conductor is connected to the semi-rigid cable 7.
Of the land pattern 3 at a position closer to the output end 10 than the center conductor of the semi-rigid cable 5 with the output side end 7b of
Is connected to the lateral part of the Further, the output side end 6
The outer conductor at b is connected to a lateral portion of the land pattern 4.

Next, in the semi-rigid cable 7 on the second transmission line side, the center conductor of the input side end 7a is connected to a position closest to the input end 9 'in the vertical portion of the land pattern 2. The outer conductor of the input end 7 a of the semi-rigid cable 7 is connected to the vertical portion of the land pattern 4. On the other hand, at the output end 7 b of the semi-rigid cable 7, the center conductor is connected between the output end 5 b and the output end 6 b in the lateral portion of the land pattern 4. The external conductor at the output side end 7b is connected to a lateral portion of the land pattern 3.

Next, the semi-rigid cable 8 on the second transmission line side has a center conductor at the input end 8a at a position in the vertical direction of the land pattern 2 farther from the input end 9 'than the semi-rigid cable 7. It is connected. The external conductor at the input end 8 a of the semi-rigid cable 8 is connected to the vertical portion of the land pattern 4.

At the output end 8 b of the semi-rigid cable 8, the center conductor is connected to the semi-rigid cable 6.
Is connected to the lateral portion of the land pattern 4 at a position closer to the output end 10 ′ than the center conductor of the semi-rigid cable 7 with the output side end 6 b of the semi-rigid cable 7 interposed therebetween. Further, an external conductor at the output side end 8b is connected to a lateral portion of the land pattern 3.

In the connection relationship described above, for example, when attention is paid to the first transmission path side, the semi-rigid cable 5 connected closer to the input end 9 than the semi-rigid cable 7 is connected to the semi-rigid cable at the output end 10 side. 7 is connected to a position more distant from the input terminal 10. On the second transmission line side, the semi-rigid cable 7 connected closer to the input end 9 ′ than the semi-rigid cable 8 is connected at the output end 10 to a position farther from the input end 10 ′ than the semi-rigid cable 8. ing.

It is preferable that the portion where the semi-rigid cables overlap (for example, the portion surrounded by broken line A in FIG. 1) is electrically insulated. That is, the high-frequency traveling wave is
Transmission is performed between the inner conductor of the coaxial line and the outer conductor sandwiching the filled dielectric, and the input and output of the coaxial line are both ends of the inner conductor and the outer conductor, respectively. It can be regarded as a net. Therefore, even if the external conductor is in contact with (ie, short-circuited to) the external conductor of another coaxial line in the middle of the coaxial line, there should be no problem unless the external conductor is used on the ground side and used on the signal side. It is better to insulate to prevent the influence on the above and unexpected short circuit.

By connecting in this manner, for example, in the first transmission line, the distance from the input end 9 to the center conductor at the input end of the semi-rigid cable and the output from the center conductor at the output end of the semi-rigid cable The distance including the distance to the end 10 can be made substantially equal in the semi-rigid cables 5 and 6, and the desired impedance value can be easily obtained (the same applies to the second transmission line). .

Here, in the transmission line transformer shown in FIG. 1, the output side end of each semi-rigid cable is
5b, 7b, 6b, 8b in order of distance from 0 and 10 '
Is arranged, but may be arranged as 7b, 5b, 8b, 6b.

As described above, in the transmission line transformer shown in FIG. 1, two coaxial lines having a characteristic impedance of 50Ω and a length of λ / 4 are connected in parallel.
Same as the connection relationship shown in (b) (however, the input / output relationship is reversed)
Therefore, a transmission line transformer having a characteristic impedance of 25Ω and an impedance ratio of 1 (input): 9 (output) can be obtained.

Next, two coaxial lines each having three characteristic impedances of 50Ω connected in parallel are used, and FIG.
The connection is made in the same way as the transmission line transformer shown in (1), the impedance is 16.7Ω, and the impedance ratio is 9 (input)
FIG. 3 shows a top view of the transmission line transformer 1 (output).

In FIG. 3, 21, 22, 23, 24
Is an approximately L-shaped land pattern provided on a substrate (not shown), 21 is an input land pattern of the first transmission path, 22 is an input land pattern of the second transmission path, and 23 is Output side land pattern of the first transmission line, 2
Reference numeral 4 denotes an output land pattern of the second transmission line. Further, 25 to 30 are coaxial lines, 25, 26, and 27 are coaxial lines on the first transmission line side, and 28, 29, and 30 are coaxial lines on the second transmission line side. Here, each coaxial line is, like the coaxial line of the transmission line transformer shown in FIG.
A semi-rigid cable having a length of λ / 4 and a characteristic impedance of 50Ω is used.

Reference numeral 31 denotes an input end on the first transmission line side, and an end of the land pattern 21 indicated by an arrow corresponds thereto. Reference numeral 32 denotes an output end on the first transmission line side, and an end of the land pattern 23 indicated by an arrow corresponds thereto. Reference numeral 31 'denotes an input end on the side of the second transmission path, and an end of the land pattern 22 indicated by an arrow corresponds thereto. Reference numeral 32 'denotes an output end on the first transmission path side, and an end side of the land pattern 24 indicated by an arrow corresponds thereto.

Here, the land patterns 21, 22, 2
The conditions such as the shape and dimensions of 3 and 24 are the same as those described with reference to FIG. 2 in the transmission line transformer of FIG. The land patterns 21, 22, 23, 24 and the semi-rigid cable 2
Regarding the connection relationship with 5, 26, 27, 28, 29, 30 in the transmission line transformer of FIG. 1, one semi-rigid cable is added to each of the first and second transmission line sides, and the input / output relationship is changed. This is the same as the reverse case.

That is, when focusing on the first transmission path,
Of the semi-rigid cables 25, 26, 27, the semi-rigid cable 25 connected closest to the input end 31
Is connected to a position farthest from the output end 32 on the output side land pattern 23 of the first transmission line.
And, the closer the semi-rigid cable is connected to the input end on the input end side, the closer the output end side
They are sequentially connected to positions farther from the output end.

Here, similarly to the connection relationship at the output end of the transmission line transformer shown in FIG. 1, the input end 3 of each semi-rigid cable in FIG.
1, 31 ', the input end of the semi-rigid cable 25, the input end of the semi-rigid cable 28, the input end of the semi-rigid cable 26,
The input end of the semi-rigid cable 29, the input end of the semi-rigid cable 27, and the input end of the semi-rigid cable 30 are connected to the input end of the semi-rigid cable 28 and the input of the semi-rigid cable 25. Side end, semi-rigid cable 29
, The input end of the semi-rigid cable 26, the input end of the semi-rigid cable 30,
May be connected in this order.

As described above, in the transmission line transformer shown in FIG. 3, the length is λ / 4 and the characteristic impedance is 5
Fig. 7 (b) shows three 0Ω coaxial lines connected in parallel.
Therefore, a transmission line transformer having a characteristic impedance of 16.7Ω and an impedance ratio of 9: 1 can be obtained.

The lengths of the semi-rigid cables 5 to 8 and 25 to 30 shown in FIGS. 1 and 3 do not necessarily have to be the same (λ / 4). May be finely adjusted around λ / 4 to adjust the impedance of the transmission line transformer.

Further, the width W of the vertical portion in each of the land patterns 1-4 and 21-24 shown in FIGS.
_L and the width W _T of the horizontal portion (see FIG. 2) are the same, but the width of the vertical portion and the width of the vertical portion are changed according to the impedance difference between the circuits connected before and after the transmission line transformer in the present embodiment. The width of the lateral portion may be varied.

The land patterns 1-4 and 21-
Each of the shapes 24 is substantially L-shaped, and their arrangement is substantially cross-shaped. For example, as shown in FIG. The cuts of ゜ may be provided (portions indicated by “M” in FIG. 4A) to reduce the reflection of the high frequency signal at the right angle portion of each land pattern. Further, as shown in FIG. 4B, the corners of the land pattern excluding the input end and the output end may be formed in a curved line.

Further, the width of the vertical and horizontal portions of each land pattern may be changed, and the corners may be curved. For example, when the impedance of the input-side external circuit is low and the impedance of the output-side circuit is high, FIG.
As in the land patterns 41, 42, 43, and 44 shown in FIG. 7, the width of the input end may be widened and the width of the output end may be narrowed.

Next, FIG. 6 shows a circuit diagram when the transmission line transformer shown in FIGS. 1 and 3 is applied to a power amplifier having an input / output impedance of 50Ω. In this figure, 50
Is an input terminal of the power amplifier shown in FIG. 5, and receives a high-frequency signal from an external circuit (output impedance 50Ω) not shown. Reference numeral 51 denotes a single impedance matching coaxial line having a characteristic impedance of 50Ω and a length of λ / 4. One end of the central conductor is connected to the input terminal 50, and one end of the external conductor is grounded. I have. Here, it is assumed that a semi-rigid cable is used as the coaxial line 51.

C1 and C2 are coupling capacitors each having one terminal connected to the center conductor and the outer conductor at the other end of the coaxial line 51, respectively. Reference numeral 52 denotes the transmission line transformer shown in FIG. 1, and the input terminal 9 (the first transmission line side) is connected to the other end of the coupling capacitor C1.
The input terminal 9 '(second transmission path side) is connected to the other end of the coupling capacitor C2.

Reference numeral 53 denotes an impedance matching circuit.
It is constituted by inductances L1 and L2 and a capacitor C3. One end of an inductance L1 is connected to the output end 10 of the transmission line transformer 52, and one end of an inductance L2 is connected to the output end 10 'of the transmission line transformer 52. One end of the inductance L1 is connected to one end of the capacitor C3, and one end of the inductance L2 is connected to the other end of the capacitor C3.

Each of Tr1 and Tr2 is a MOSFET, and the gate of Tr1 is an impedance matching circuit 53.
Connected to the other end of the inductance L3 of the output matching circuit 54, connected to the other end of the high-frequency choke coil L on the DC power supply side, and connected to the drain of the power supply bypass capacitor C1. DC power supply V _DD is supplied via a source is grounded. Further, the gate of Tr2 is connected to the other end of the inductance L2 of the impedance matching circuit 53, and the drain is connected to the other end of the inductance L4 of the output matching circuit 54. _Are connected to the DC power supply V _{DD at} the drain of the power supply, the DC power supply V _DD is supplied, and the source is grounded.

Although not shown in this circuit, Tr
The same bias circuit as Tr1 may be added to Tr2 for both the gate and the drain of Tr1 and Tr2. Also, Tr
The input and output impedances of Tr1 and Tr2 are both set to 5Ω from the theoretical output resistance approximate calculation formula or the specification value at the maximum output of the manufacturer data, and the drain-source voltage Vce
ds is 12.5 V, and the saturation voltage Vsat is 4 V.

Reference numeral 54 denotes an impedance matching circuit.
It is constituted by inductances L3 and L4 and a capacitor C4. One end of an inductance L3 is connected to the drain of Tr1, and one end of an inductance L4 is connected to the drain of Tr2. Further, one end of a capacitor C4 is connected to the other end of the inductance L3, and the capacitor C4 is connected to the other end of the inductance L4.
Are connected to each other.

Reference numeral 55 denotes a transmission line transformer shown in FIG. 3, in which the input terminal 31 (the first transmission line side) is connected to the other end of the inductance L3 of the impedance matching circuit 54, and the input terminal 31 '(the second transmission line side). ) Are connected to the other end of the inductance L4 of the impedance matching circuit 54, respectively. C5 and C6 are coupling capacitors. One end of C5 is an output terminal 32 of the transmission line transformer 55.
One end of C6 is the output terminal 3 of the transmission line transformer 55.
2 'are connected to each other.

Reference numeral 56 denotes a coaxial line for impedance matching, and the center conductor at one end is a coupling capacitor C5.
The other end of the coupling capacitor C6 is connected to the other end of the coupling capacitor C6. The center conductor at the other end is the output terminal 5 of the high-frequency power amplifier.
7 and the outer conductor at the other end is grounded. Here, it is assumed that a single semi-rigid cable having a characteristic impedance of 50Ω and a length of λ / 4 is used as the coaxial line 56.

The other end of the high-frequency choke coil L whose one end is connected to the DC power supply V _GG is connected between the coupling capacitor C 1 and the input end 9 of the transmission line transformer 52. Is supplied with a DC power supply V _GG via the. Further, between the transmission line transformer 52 and the impedance matching circuit 53, a resistor R1 and a capacitor C7, which are connected in series, and a resistor R
2 and the capacitor C8.

Next, in the above-described high-frequency power amplifier, when the output power of the MOSFETs Tr1 and Tr2 is 10 W, the output resistance Ro is calculated from the above-mentioned equation (2) by Ro [Ω] = (12. 5-4) ^2/10/2 = 3.6125 the [Ω].

Further, since the impedance ratio of the transmission line transformer 52 is 1: 9, the impedance when each of Tr1 and Tr2 is viewed from the input side is given by the following equation (3). 5 × 9) = 33.54 [Ω]. In the above equation, MOSFET, Tr1, Tr
As the input impedance of 2, a specified value of 5 [Ω] is used.

The impedance when the input side is viewed from the Tr1 and Tr2 sides is と (25 × 50 × 1) = 35.35 [Ω], and can be almost matched.

The more strict impedance matching is performed by adjusting the inductance L of the impedance matching circuit 52.
1, L2 and the value of the capacitor C3 are appropriately adjusted.

On the other hand, on the output side of Tr1 and Tr2, the impedance ratio of the transmission line transformer 55 is 9: 1.
Therefore, the impedance when seeing Tr1 and Tr2 from the output side is √ (16.7 × 5 × 9) = 27.41 [Ω] according to the above-described equation (3). In the above equation, MOSFET, Tr
1, the output impedance of Tr2, the specified value of 5
[Ω] is used. For example, when the specification value is not clear,
When impedance matching is performed at a desired output power, the value of the output resistance Ro obtained from the above-described equation (2) may be used.

The impedance when the output side is viewed from the Tr1 and Tr2 sides is √ (16.7 × 50 × 1) = 28.89 [Ω], and can be almost matched.

The more strict impedance matching is performed by adjusting the inductance L of the impedance matching circuit 54.
3, by appropriately adjusting the values of L4 and capacitor C4.

The transmission line transformer of the present embodiment is
Not limited to the high-frequency amplifier described above, for example, a multiplier, a mixer (particularly, a double-balanced mixer and a single-balanced mixer), a balun, and a hybrid (having three or more input / output terminals and transmitting power to two or more circuits It can also be applied to a high-frequency circuit using a transformer at a high frequency, such as a circuit for distributing or synthesizing.

[0075]

As described above, according to the present invention, the closer the coaxial line is connected to the input end in each input-side pattern in the first and second transmission lines, the more the output end in each output-side pattern is. The distance from the input end of the input side pattern to the input end of the coaxial line and the distance from the output end of the coaxial line to the output end of the output side pattern, , Can be made substantially equal in the path of each coaxial line, and a desired impedance value can be easily obtained.

By appropriately adjusting the length of each coaxial line and the width of the land pattern, the impedance of the transmission line transformer can be easily adjusted, and as a result, impedance matching with an external circuit can be easily achieved.

Further, a miter is provided on the land pattern,
Alternatively, it is possible to reduce the reflection of the high-frequency signal by forming the corners of the land pattern in a curved line.

[Brief description of the drawings]

FIG. 1 is a top view showing one embodiment of a transmission line transformer according to the present invention.

FIG. 2 is a top view showing only a land pattern of the transmission line transformer shown in FIG.

FIG. 3 is a top view showing another embodiment of the transmission line transformer according to the present invention.

FIG. 4 is a top view showing another shape of the land pattern shown in FIG. 2;

FIG. 5 is a top view showing another shape of the land pattern shown in FIG. 2;

FIG. 6 is a circuit diagram showing a configuration of a high-frequency power amplifier using the transmission line transformer shown in FIGS. 1 and 3.

FIG. 7 is a connection diagram illustrating an example of a transmission line transformer.

FIG. 8 is an explanatory diagram for describing an impedance matching method using a coaxial line.

FIG. 9 is a connection diagram showing an example in which two coaxial lines are connected in parallel.

[Explanation of symbols]

1-4, 21-24, 41-44 Land pattern 5-8, 25-30 Semi-rigid cable (coaxial line) 9, 9 ', 31, 31' Input terminal 10, 10 ', 32, 32' Output terminal

Claims (6)

[Claims] 1. A transmission line transformer formed by using a plurality of coaxial lines and connecting the coaxial lines to each other, comprising: an input side and an output side pattern of a first transmission line; A land pattern in which four substantially L-shaped patterns are arranged on the substrate in a substantially cross shape at predetermined intervals from each other, and a land pattern on the first transmission path side of the land pattern. A plurality of patterns each having a length of λ / 4 (where λ is an effective wavelength of an input high-frequency signal) and being connected between at least two input / output patterns and between input / output patterns on the second transmission path side. In each of the input-side patterns in the first and second transmission lines, the closer the coaxial line is connected to the input end, the farther from the output end is in each output-side pattern. Transmission-line transformer to. 2. The transmission line transformer according to claim 1, wherein an impedance of the transmission line transformer is adjusted by changing a length of each of the plurality of coaxial lines. 3. The impedance of the transmission line transformer is adjusted by changing the width of each pattern constituting the land pattern.
Or the transmission line transformer according to 2. 4. The transmission line transformer according to claim 1, wherein a miter is provided at an L-shaped right angle portion in each of the land patterns. 5. The transmission line transformer according to claim 1, wherein in each of the land patterns, a corner excluding an input end and an output end is formed by a curve. . 6. A transmission line transformer according to claim 1, further comprising a transistor for amplifying the power of the input high-frequency signal, wherein the transmission line transformer according to claim 1 is connected to an input / output side of the transistor. A high-frequency power amplifier provided.