JP4472652B2 - High frequency suppression circuit - Google Patents

Description

  The present invention relates to a high-frequency suppression circuit that suppresses harmonics contained in an output signal of a high-frequency circuit used in a communication system or the like.

  In a high-frequency circuit such as a microwave high-power amplifier, a harmonic signal other than the fundamental wave is generated. Therefore, it is necessary to suppress the harmonics without affecting the characteristics of the high-power amplifier or the like at the fundamental wave.

As a method for suppressing such harmonics, for example, as shown in Patent Document 1, a short stub or an open stub that realizes a short state with respect to the harmonics is connected to the output side of the semiconductor element, and the harmonics are reduced. There was a way to reflect.
For example, as shown in Patent Document 2, a method of reflecting a harmonic by providing a coupling line that resonates with a harmonic in the transmission line on the output side of the semiconductor element has been used.

Japanese Patent Laid-Open No. 2001-53510 JP-A-8-139535

  In the conventional method of connecting an open stub or a short stub that realizes a short state with respect to the harmonics as described above, generally, for the second harmonic, the wavelength of the fundamental wave is λ, and λ / By connecting a short stub having a length of 4, a circuit that realizes an open state for the fundamental wave and a short state for the double wave can be configured. Therefore, a circuit that does not affect the fundamental wave can be realized. However, for the third harmonic, a short state is realized for the third harmonic by connecting an open stub having a length of λ / 12 or a short stub having a length of λ / 6. Since the fundamental wave is not in an open state, the fundamental wave is affected by this third harmonic wave suppression stub, and there is a problem that it is necessary to regain impedance matching.

  In addition, in the method of providing a coupling line that resonates with harmonics in the main line and reflecting the harmonics, the characteristic of the fundamental wave is not affected, but a resonator having a high Q value is obtained. Therefore, there is a problem that it is difficult to apply to a high-frequency circuit having a wide band.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a high-frequency suppression circuit capable of suppressing the second harmonic and the third harmonic without affecting the fundamental wave. .

The high-frequency suppression circuit according to the present invention includes a main line through which an output signal of the high-frequency circuit flows, a fundamental wave branched from the main line, and grounded at a position having a length of λ / 4 with respect to the fundamental wave wavelength λ. A short stub for suppressing the double wave that suppresses the double frequency and a grounding point at a length of λ / 12 in the main line direction with a predetermined distance from the ground point of the short stub for suppressing the double wave. The first third harmonic coupling line for suppressing the frequency three times the fundamental wave and the second harmonic suppressing short stub have a predetermined interval on the same side as the first third harmonic coupling line. Installed at a distance from the main line and placed at a length of λ / 12 in the direction of the ground point of the double wave suppression short stub and grounded the main line side to suppress the frequency three times the fundamental wave. and a second triple-wave coupling line, three times the frequency of the fundamental wave If the length set to lambda _3, the first triple-wave coupling line, to the main line, it becomes the open stub length of 3 [lambda] _3/4, second third harmonic coupling line, the main line relative, is obtained as the open stub length of λ _3/4.

The high-frequency suppression circuit of the present invention has a short stub for second harmonic suppression having a length of about λ / 4, a predetermined interval so that the third harmonic is coupled to the short stub for second harmonic suppression , and Since a plurality of third harmonic coupling lines having one end grounded and a line length of about λ / 12 are provided on the same side , the second harmonic and the third harmonic are suppressed without affecting the fundamental wave. I can do it.

Embodiment 1 FIG.
1 is a block diagram showing a high-frequency suppression circuit according to Embodiment 1 of the present invention.
In the figure, the high-frequency suppression circuit includes a gate side bias circuit 1, a high output FET 2, a drain side bias circuit 3, a DC cut capacitor 4, a main line 5, a second harmonic suppression short stub 6, and a third harmonic coupling line 7. I have.

  The gate side bias circuit 1 to the DC cut capacitor 4 constitute a high frequency circuit such as a microwave high output amplifier, and the gate side bias circuit 1 is a bias circuit on the gate side of the high output FET 2. The drain side bias circuit 3 is a drain side bias circuit. The high-power FET 2 is a semiconductor element that performs high-frequency signal amplification, and its source side is grounded. The DC cut capacitor 4 is connected to the output side of the high output FET 2 and is a capacitor for removing a direct current component from the output signal. The main line 5 is a line through which the output signal of the high frequency circuit flows.

  The second harmonic suppression short stub 6 is a short stub connected to the main line 5 and has a length of about λ / 4 when the wavelength of the fundamental wave is λ. Further, the third harmonic wave coupling line 7 is a line having a length of about λ / 12, which is installed beside the second harmonic wave suppressing short stub 6 with a predetermined interval. The third harmonic wave coupling line 7 is arranged with a length of about λ / 12 from the ground point of the second harmonic wave suppressing short stub 6 in the direction of the main line 5, and the main line 5 side is grounded. In practice, a matching circuit may be required on the input / output side of the high-power FET 2, but it is omitted here.

Next, the harmonic suppression operation of the high frequency suppression circuit configured as described above will be described.
FIG. 2 is an explanatory diagram of the principle, in which (a) shows the case of the fundamental wave, (b) the second harmonic, and (c) the third harmonic.

  As shown in FIG. 2 (a), the length of the third harmonic wave coupling line 7 is sufficiently short, about λ / 12, with respect to the fundamental wave (wavelength λ), so that it can be ignored without any influence. it can. The second harmonic suppression short stub 6 is a short stub having a length of λ / 4, and is opened at the connection portion with the main line 5, and this circuit also does not affect the fundamental wave.

Next, 2 for the harmonic (wavelength lambda ₂ = lambda / 2), as shown in FIG. 2 (b), 3 harmonic length of the coupling line 7 lambda _2/6 degrees and the second harmonic for short with respect to the wavelength lambda _2, little effect without giving, the short stub 6 for second harmonic suppression in short stub length of lambda _2/2, becomes short at the junction with the main line 5, The second harmonic can be suppressed.

However, 3 with respect to the harmonic (wavelength lambda ₃ = lambda / 3), as shown in FIG. 2 (c), the length of the third harmonic wave coupling line 7 significantly influence the lambda _3/4 of about it binds to the second harmonic suppression short stub 6, looked like 3 [lambda] _3/4 length open stub is connected to the main line 5, becomes short at the junction with the main line 5, 3 times Waves can be suppressed.

  Therefore, with such a configuration, it is possible to suppress the second harmonic and the third harmonic without affecting the fundamental wave.

  Further, since a short stub is used as a method of suppressing the second harmonic, a suppression circuit having a wider band than that described in Japanese Patent Laid-Open No. 8-139535 is obtained for the second harmonic, and a high frequency with a wide band. It can also be applied to circuits.

  In addition, when the suppression frequency of the short stub deviates, it is generally impossible to adjust the length by shaving the short stub, so it is impossible to adjust the suppression frequency of the short stub. In the embodiment, since the second harmonic suppression short stub 6 and the third harmonic coupling line 7 are coupled, the interval between the second harmonic suppression short stub 6 and the third harmonic coupling line 7 is adjusted. Thus, the suppression frequency can be adjusted.

  The relationship between the suppression frequency and the interval (pattern interval) between the second harmonic suppression short stub 6 and the third harmonic coupling line 7 is as follows. That is, when the pattern interval is narrowed, the suppression frequency of the second harmonic changes to a lower one, and the suppression frequency of the third harmonic changes to a higher one. Conversely, if the pattern interval is widened, the suppression frequency of the second harmonic changes to the higher side, and the suppression frequency of the third harmonic changes to the lower side.

  Further, when such a pattern interval is changed, not only the suppression frequency but also the suppression amount changes. For example, when the pattern interval is narrowed, the degree of coupling between the second harmonic suppression short stub 6 and the third harmonic coupling line 7 increases, so that the third harmonic suppression amount increases, but the second harmonic suppression amount. Is somewhat smaller because of the influence of the third harmonic coupling line 7. On the contrary, when the pattern interval is increased, the influence of the third harmonic coupling line 7 is reduced, so that the suppression amount of the third harmonic is reduced and the suppression amount of the second harmonic is increased.

  As described above, according to the high frequency suppression circuit of the first embodiment, the main line through which the output signal of the high frequency circuit flows is used for the second harmonic suppression having a length of about λ / 4 with respect to the wavelength λ of the fundamental wave. A short stub is provided, and at the side of the second harmonic suppression short stub, one end is grounded so that the third harmonic is coupled to the second harmonic suppression short stub and the third harmonic coupling having a line length of about λ / 12 is provided. Since the service lines are arranged with a predetermined interval, the second harmonic and the third harmonic can be suppressed without affecting the fundamental wave.

Further, according to the high frequency suppression circuit of the first embodiment, the third harmonic coupling line is arranged in the main line direction from the ground point of the second harmonic suppression short stub, and the main line side is grounded. , 3 for the harmonic (lambda _3), looks like the open stub length of 3 [lambda] _3/4 is connected to the main line, becomes short at the junction with the main line, suppressing the third harmonic I can do it.

Embodiment 2. FIG.
FIG. 3 is a configuration diagram of the high-frequency suppression circuit according to the second embodiment.
The high-frequency suppression circuit according to the second embodiment includes a gate side bias circuit 1, a high output FET 2, a drain side bias circuit 3, a DC cut capacitor 4, a main line 5, a second harmonic suppression short stub 6, and a third harmonic coupling line. It consists of eight. Here, since the configuration other than the third harmonic coupling line 8 is the same as that of the first embodiment, the corresponding parts are denoted by the same reference numerals and the description thereof is omitted.

  The third harmonic wave coupling line 8 is separated from the main line 5 by an appropriate distance beside the second harmonic wave suppression short stub 6 so that the third harmonic wave is coupled. The coupling line is arranged in the direction with a length of about λ / 12 and the main line 5 side is grounded.

In the high-frequency suppression circuit configured as described above, the fundamental principle and the second harmonic are the same as those in the first and second embodiments. Further, 3 with respect to the harmonic (wavelength lambda ₃ = lambda / 3), the length of the third harmonic wave coupling line 8 becomes lambda _3/4 approximately, combined with second harmonic suppression short stub 6, lambda _3/4 length open stub of appear to be connected to the main line 5, becomes short at the junction with the main line 5, it is possible to suppress the third harmonic wave.

As described above, according to the high frequency suppression circuit of the second embodiment, the third harmonic coupling line is disposed in the direction of the ground point of the second harmonic suppression short stub with a predetermined interval from the main line, Since the main line side is grounded, the second harmonic and the third harmonic can be suppressed without affecting the fundamental wave. Further, the third harmonic (lambda ₃₎ is an open stub length of lambda _3/4 is seen to be connected to the main line, it is short at the junction with the main line, to suppress the third harmonic I can do it.

Embodiment 3 FIG.
FIG. 4 is a configuration diagram of the high-frequency suppression circuit according to the third embodiment.
The high-frequency suppression circuit according to the third embodiment includes a gate side bias circuit 1, a high output FET 2, a drain side bias circuit 3, a DC cut capacitor 4, a main line 5, a second harmonic suppression short stub 6, and a third harmonic coupling line. 9,10. Here, since the configuration other than the third harmonic coupling lines 9 and 10 is the same as that of the first and second embodiments, the corresponding parts are denoted by the same reference numerals and the description thereof is omitted.

  The third harmonic wave coupling lines 9 and 10 are lines provided on both sides of the second harmonic wave suppressing short stub 6 so that the third harmonic wave is coupled. 10 is arranged with a predetermined distance from the second harmonic suppression short stub 6 and with a length of about λ / 12 from the ground point of the second harmonic suppression short stub 6 in the direction of the main line 5. It is configured to ground the 5 side.

According to the present embodiment, as shown in the first embodiment, it is possible to suppress the second harmonic and the third harmonic without affecting the fundamental wave. Further, by making a difference in the lengths of the third harmonic wave coupling lines 9 and 10, the frequencies coupled to the third harmonic wave coupling lines 9 and 10 are different. having a resonance point, it looks like the open stub length of 3 [lambda] _3/4 are connected. Therefore, the band for suppressing the third harmonic can be expanded.

Further, as a configuration in which a plurality of third-harmonic coupling lines are provided, the configurations of the first and second embodiments may be combined as shown in FIG.
In FIG. 5, the gate-side bias circuit 1 to 2nd harmonic wave suppression short stub 6 is the same as in the first and second embodiments, and the 3rd harmonic wave coupling line 11 (first 3rd harmonic wave coupling line) is: The configuration is the same as that of the third harmonic wave coupling line 7 in the first embodiment. The third harmonic wave coupling line 12 (second third harmonic wave coupling line) has the same configuration as the third harmonic wave coupling line 8 in the second embodiment.

In the high-frequency suppression circuit configured as described above, the fundamental principle and the second harmonic are the same as those in the first and second embodiments. Further, 3 with respect to the harmonic (wavelength lambda ₃ = lambda / 3), appear to the open stub length of 3 [lambda] _3/4, the open stub length of lambda _3/4 are both connected .

Moreover, if the changed slightly the length of the third harmonic wave coupling line 11 and 12, the third harmonic coupling line 11 (= the 3 [lambda] _3/4 at a frequency that resonates at a length of 3 times the wave coupling line 11 visible length open stub) is significantly, the third harmonic wave coupling line 12 (= lambda _3/4 length open stub) appear significantly in the frequency that resonates with a length of 3 times the wave coupling line 12 . For this reason, two resonance points can be formed, and a high frequency suppression circuit having a wide band of the third harmonic suppression frequency can be realized.

On the other hand, if it is equal in length triple wave coupling line 11, 12, 3 [lambda] _3/4 length and open stub, since the open stub is visible both the length of lambda _3/4 at a frequency that resonates The amount of suppression can be increased.

  As described above, according to the high frequency suppression circuit of the third embodiment, since a plurality of third harmonic coupling lines are provided, the second harmonic and the third harmonic can be suppressed without affecting the fundamental wave. I can do it. Further, it is possible to configure a harmonic suppression circuit having a wide suppression frequency band even for the third harmonic.

Embodiment 4 FIG.
FIG. 6 is a configuration diagram of the second harmonic suppressing short stub 6 and the third harmonic coupling line 13 according to the fourth embodiment.
In the first to third embodiments, the third harmonic coupling line is provided on the grounding point side of the second harmonic suppression short stub 6 or on the main line 5 side. A third harmonic wave coupling line 13 having a length of about / 12 is arranged at a predetermined interval in the middle position of the second harmonic wave suppressing short stub 6. The ground point of the third harmonic wave coupling line 13 is on the ground point side of the second harmonic wave suppressing short stub 6.

In the high-frequency suppression circuit configured in this way, as shown in FIG. 6, the third harmonic coupling line 13 is short-circuited on the ground point side and open on the main line 5 side. It becomes short-circuited, and the third harmonic suppression effect can be obtained. In this case, lambda _3/2 Length: Short stub appears to be connected to the main line 5.

  As described above, in the high-frequency suppression circuit according to the fourth embodiment, the third-harmonic coupling line is arranged with a predetermined interval from the middle portion of the second-harmonic suppression short stub, and the second-harmonic suppression short circuit. Since the ground point side of the stub is grounded, the second harmonic and the third harmonic can be suppressed without affecting the fundamental wave.

It is a block diagram which shows the high frequency suppression circuit by Embodiment 1 of this invention. It is explanatory drawing which shows the principle of the high frequency suppression circuit by Embodiment 1 of this invention. It is a block diagram which shows the high frequency suppression circuit by Embodiment 2 of this invention. It is a block diagram which shows the high frequency suppression circuit by Embodiment 3 of this invention. It is a block diagram which shows the other example of the high frequency suppression circuit by Embodiment 3 of this invention. It is a principal part block diagram which shows the high frequency suppression circuit by Embodiment 4 of this invention.

Explanation of symbols

1 Gate side bias circuit, 2 High output FET, 3 Drain side bias circuit, 4 DC cut capacitor, 5 Main line, 6 Double harmonic suppression short stub, 7, 8, 9, 10, 11, 12, 13 3 times Wave coupling line.

Claims (2)

The main line through which the output signal of the high-frequency circuit flows, and the double that suppresses twice the frequency of the fundamental wave, branched from this main line and grounded at a position of λ / 4 length with respect to the fundamental wavelength λ The frequency of the fundamental wave is 3 times the fundamental wave, grounded at a position of λ / 12 in the main line direction, with a predetermined distance from the grounding point of the wave suppression short stub and the double wave suppression short stub. The first third harmonic wave coupling line to be suppressed and the second harmonic wave suppressing short stub are installed on the same side as the first third harmonic wave coupling line with a predetermined distance from the main line. A second triple that suppresses a frequency that is three times the fundamental wave with an interval, placed at a length of λ / 12 in the direction of the grounding point of the second harmonic wave suppression short stub and grounded on the main line side and a wave coupling line, and a wavelength of 3 times the frequency of the fundamental wave lambda ₃ If the first triple-wave coupling line, relative to the main line, become the open stub length of 3 [lambda] _3/4, the second triple-wave coupling line is the main line against it, lambda _3/4 length frequency suppression circuit was set to be the open stub. The main line through which the output signal of the high-frequency circuit flows, and the double that suppresses twice the frequency of the fundamental wave, branched from this main line and grounded at a position of λ / 4 length with respect to the fundamental wavelength λ The frequency of the fundamental wave is 3 times the fundamental wave, grounded at a position of λ / 12 in the main line direction, with a predetermined distance from the grounding point of the wave suppression short stub and the double wave suppression short stub. The first third harmonic wave coupling line to be suppressed and the second harmonic wave suppressing short stub are installed on the same side as the first third harmonic wave coupling line with a predetermined distance from the main line. A second 3 which suppresses a frequency three times that of the fundamental wave which is spaced apart and arranged in the ground point direction of the second harmonic suppression short stub with a length shorter than λ / 12 and grounds the main line side. And a wavelength for a frequency three times that of the fundamental wave. _{If 3} were, the first triple-wave coupling line, relative to the main line, become the open stub length of 3 [lambda] _3/4, the second triple-wave coupling line, the main relative line, lambda _3/4 as a short length open stub from a high-frequency suppression circuit to widen the band of the third harmonic suppression frequency which suppresses 3 times the frequency for the fundamental wave.

Images