JP2010245971A - High frequency interruption circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency interruption circuit for performing the high density layout of a high frequency circuit. <P>SOLUTION: This high frequency interruption circuit is provided with: a coupling line 30 formed of a pair of transmission lines 3 and 4 arranged in parallel with their both edges as input terminals 1, 2, 9 and 10, which has the length of 1/2 wavelength in the fundamental wave components of a high frequency signal propagating through a high frequency circuit; and open stubs 5, 6, 7 and 8 formed so as to be connected to each of the input terminals 1, 2, 9 and 10, which has the length of 1/4 wavelength in the fundamental wave components. Thus, it is possible to suppress the propagation of fundamental wave components and odd harmonic components before and after the joint of the transmission lines 3 and 4 and the open stubs 5, 6, 7 and 8, and it is possible to suppress the coupling of the fundamental wave components, the odd harmonic components, and even harmonic components in a coupling line 30 acting as a directional coupler, and it is possible to suppress the leakage of the fundamental wave components, the even harmonic components and the odd harmonic components between the input terminals 1 and 2 and the input terminals 9 and 10 faced to each other in the coupling line 30. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a high-frequency cutoff circuit that is used in a high-frequency circuit such as a microwave circuit or a millimeter-wave circuit, and that has a property of blocking a high-frequency signal propagating through the high-frequency circuit.

  In a high frequency circuit such as a microwave circuit or a millimeter wave circuit, for example, a fundamental wave component of a high frequency signal or a harmonic component of the fundamental wave leaks to a drain bias circuit of an amplifier using an FET (Field Effect Transistor). When coupled to the gate bias circuit, a feedback loop is formed between the drain bias circuit and the gate bias circuit, and loop oscillation may occur, which may cause unstable operation of the amplifier. For this reason, it is necessary to prevent leakage of the fundamental wave component and the harmonic component of the high frequency signal to the gate bias circuit and the drain bias circuit.

  In addition, as a document disclosing a technique for adjusting a center frequency of a parallel-band band-stop filter formed of a microstrip line conductor in a high-frequency circuit such as a microwave circuit or a millimeter wave circuit, there is Patent Document 1 below. .

  In this Patent Document 1, a capacitive stub is formed by bending a resonance line having a length of ½ wavelength of a signal at the center and bringing a portion having a length of ¼ wavelength from the end in parallel to the main transmission line. In the band rejection filter with the remaining 1/4 wavelength length as an open stub, a slit is provided in the bent portion at the center, and the slit is filled with a conductive plate or conductive paste, thereby resonating the resonance line. A technique for adjusting the frequency and adjusting the center frequency of the band rejection filter is disclosed.

JP-A-53-128248

  However, in the technique disclosed in Patent Document 1, it is necessary to configure a plurality of band rejection filters whose center frequencies are set to a fundamental wave and a plurality of harmonics of a high-frequency signal, which increases the circuit scale. there were. Further, for example, when applied to a gate bias circuit and a drain bias circuit of an amplifier, when the main transmission lines of the band rejection filters are arranged close to each other, a coupling line is formed and set by the two main transmission lines. Harmonic components in bands other than the frequency may be combined and loop oscillation may occur. For this reason, in order to operate the amplifier stably, there is a problem in that the main transmission lines of the band rejection filters must be arranged apart from each other, resulting in a large circuit area.

  The present invention has been made in view of the above, and an object thereof is to obtain a high-frequency cutoff circuit that enables a high-density layout of a high-frequency circuit.

  In order to solve the above-described problems and achieve the object, the present invention provides a dielectric substrate, a ground conductor provided on the lower surface of the dielectric substrate, and a microstrip line conductor provided on the upper surface of the dielectric substrate. A high-frequency cutoff circuit of a high-frequency circuit comprising: a pair having a length of ½ wavelength in a fundamental wave component of a high-frequency signal propagating through the high-frequency circuit and arranged in parallel with both ends as input ends A coupled line formed of a transmission line of the above, and an open stub having a length of ¼ wavelength in the fundamental wave component and connected to one of the input ends and the other of the input ends. It is characterized by that.

  According to the present invention, two transmission lines having a wavelength of ½ wavelength in the fundamental wave component are arranged in parallel to form a coupled line, and 1% of the fundamental wave component is provided at each end of the two transmission lines. By connecting open stubs with a length of / 4 wavelength, propagation of the fundamental wave component and odd harmonic components is suppressed before and after the junction between the transmission line and the open stub, and it acts as a directional coupler. Since coupling of the fundamental wave component, odd harmonic component, and even harmonic component is suppressed in the coupled line, the fundamental wave component, even harmonic component, and odd harmonic component between the input terminals facing each other in the coupled line Leakage can be prevented and a high-density layout of the high-frequency circuit can be achieved.

FIG. 1 is a diagram illustrating an example of a high-frequency cutoff circuit according to the first embodiment. FIG. 2 is a diagram of an example of the high-frequency cutoff circuit according to the second embodiment.

  Embodiments of a high-frequency cutoff circuit according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
In a high-frequency circuit such as a microwave circuit or a millimeter-wave circuit, when a plurality of high-frequency circuits are arranged close to each other, a fundamental wave component (hereinafter simply referred to as “fundamental wave component”) of a high-frequency signal propagating through the high-frequency circuit and its harmonics There is a risk that coupling of components (hereinafter simply referred to as “harmonic components”) may occur and cause unstable operation of the high-frequency circuit. For example, if the fundamental wave component and the harmonic component leak to the drain bias circuit of the amplifier using the FET and are coupled to the gate bias circuit, a feedback loop is formed between the drain bias circuit and the gate bias circuit, and loop oscillation occurs. It becomes a factor to occur. Therefore, in the first embodiment, even when applied to a drain bias circuit and a gate bias circuit of an FET, for example, the fundamental wave component and the harmonic component are prevented from leaking between the gate and the drain.

FIG. 1 is a diagram illustrating an example of a high-frequency cutoff circuit according to the first embodiment. First, the configuration of the high-frequency cutoff circuit according to the first embodiment will be described with reference to FIG. In FIG. 1, a high-frequency cutoff circuit 100 includes a transmission line 3 and a transmission line 4 that have a characteristic wavelength Z ₀ having a length of ½ wavelength in the fundamental component, and are arranged in parallel to form a coupling line 30. . Open stubs 5, 6, 7, 8 having a length of ¼ wavelength in the fundamental wave component are connected to each end (both ends) of each transmission line 3, 4. The transmission lines 3 and 4 and the open stubs 5, 6, 7, and 8 can be formed of a microstrip line conductor on a dielectric substrate (not shown).

  In the high-frequency cutoff circuit 100 configured in this manner, the junction between the transmission line 3 and the open stub 5 is the input end 1, the junction between the transmission line 4 and the open stub 7 is the input end 2, and the transmission line 3 and the open stub. 6 is the input end 9, and the junction between the transmission line 4 and the open stub 8 is the input end 10. The coupled line 30 functions as a directional coupler.

  Next, the functional operation of the high-frequency cutoff circuit 100 will be described with reference to FIG. Here, in a high frequency circuit (not shown) connected to the input terminal 1, a fundamental wave component, a harmonic component of 1 / (2N) wavelength (N is an integer of 1 or more) (hereinafter, “even harmonic component”). And leakage from the input terminal 1 to each of the input terminals 2, 9, 10 when dealing with a signal including a harmonic component of 1 / (2N + 1) wavelength (hereinafter referred to as “odd harmonic component”) The prevention function will be described.

  First, the leakage prevention function of the fundamental wave component and the odd harmonic component will be described. In the fundamental wave component and the odd harmonic component, since the junction between the transmission line 3 and the open stub 5 can be regarded as a ground point, it is totally reflected by a high-frequency circuit (not shown) connected to the input terminal 1. However, since it is difficult to make the junction between the transmission line 3 and the open stub 5 as an ideal ground, in reality, the reflection line 3 is not totally reflected, and part of the fundamental wave component and the odd harmonic component are transmitted. Propagate to.

  The fundamental wave component and the odd harmonic component propagated to the transmission line 3 can be regarded as the double wave of the signal having a wavelength twice that of the fundamental wave, and the odd harmonic component is twice the wavelength of the fundamental wave. 2 (2N + 1) harmonics (where N is an integer equal to or greater than 1), the transmission line 30 is transmitted when the coupled line 30 acts as an ideal directional coupler with matching even-odd mode electrical lengths. Although no coupling occurs between the line 3 and the transmission line 4, it is difficult to make the transmission lines 3 and 4 an ideal directional coupler. Some of them are coupled and propagate to the transmission line 4.

  The fundamental wave component and the odd harmonic component propagated to the transmission line 4 are totally reflected on the transmission line 4 side because the junction between the transmission line 4 and the open stub 7 can be regarded as a ground point. However, since it is difficult to make the junction between the transmission line 4 and the open stub 7 as an ideal ground, actually, total reflection is not caused, and part of the fundamental wave component and the odd harmonic component are input to the input terminal 2. Propagate to.

  That is, in the process in which the fundamental wave component and the odd harmonic component propagate from the input terminal 1 to the input terminal 2, the joint between the transmission line 3 and the open stub 5, the coupling line 30 acting as a directional coupler, and the transmission line 4 By passing through the junction between the open stub 7 and the input stub 7, the fundamental wave component and the odd harmonic component that propagate from the input terminal 1 to the input terminal 2 can be attenuated step by step.

  Further, the fundamental wave component and the odd harmonic component propagated to the transmission line 3 are totally reflected on the transmission line 3 side because the junction between the transmission line 3 and the open stub 6 can be regarded as a ground point. However, since it is difficult to make the junction between the transmission line 3 and the open stub 6 to be ideally grounded, actually, total reflection is not caused, and part of the fundamental wave component and the odd harmonic component are input to the input terminal 9. Propagate to.

  That is, in the process in which the fundamental wave component and the odd harmonic component propagate from the input end 1 to the input end 9, they pass through the junction between the transmission line 3 and the open stub 5 and the junction between the transmission line 3 and the open stub 6. Thus, the fundamental wave component and the odd harmonic component propagating from the input terminal 1 to the input terminal 9 in a stepwise manner can be attenuated.

  Furthermore, the fundamental wave component and the odd harmonic component propagated to the transmission line 4 are totally reflected on the transmission line 4 side because the junction between the transmission line 4 and the open stub 8 can be regarded as a ground point. However, since it is difficult to make the junction between the transmission line 4 and the open stub 8 as an ideal ground, in reality, there is no total reflection, and part of the fundamental wave component and the odd harmonic component are input to the input terminal 10. Propagate to.

  That is, in the process in which the fundamental wave component and the odd harmonic component propagate from the input end 1 to the input end 10, the joint between the transmission line 3 and the open stub 5, the coupling line 30 acting as a directional coupler, and the transmission line 4 And the open stub 8 pass through the junction, the fundamental wave component and the odd harmonic component propagating from the input terminal 1 to the input terminal 10 in stages can be attenuated.

  Next, a function for preventing leakage of even harmonic components will be described. Since the even harmonic component can be regarded as a 2N harmonic of the fundamental wave (N is an integer of 1 or more), when the coupled line 30 functions as an ideal directional coupler, the transmission line 3 and the transmission line 4 is not coupled, but it is difficult to make the coupled line 30 an ideal directional coupler, so in practice, some even harmonic components are coupled and propagated to the transmission line 4. To do. The even harmonic component propagated to the transmission line 4 passes through the junction between the transmission line 4 and the open stub 7 and propagates to the input end 2.

  That is, in the process in which the even harmonic component propagates from the input end 1 to the input end 2, the even harmonic component propagates from the input end 1 to the input end 2 by passing through the coupling line 30 that acts as a directional coupler. Can be attenuated.

  The even harmonic component propagated to the transmission line 4 passes through the junction between the transmission line 4 and the open stub 8 and propagates to the input end 10.

  That is, in the process in which the even harmonic component propagates from the input end 1 to the input end 10, the even harmonic component propagates from the input end 1 to the input end 10 by passing through the coupling line 30 acting as a directional coupler. Can be attenuated.

  On the other hand, the even harmonic component passes through the junction between the transmission line 3 and the open stub 5 and the junction between the transmission line 3 and the open stub 6 and propagates to the input end 9. That is, there is no leakage prevention function for even harmonic components propagating from the input terminal 1 to the input terminal 9.

  The high-frequency cutoff circuit 100 has the same configuration when viewed from any of the input terminals 1, 2, 9, and 10, so that the input terminals 1 to 9, 10, and the input terminal 9 to the input terminal 1. , 2, 10, and the leakage prevention function from the input terminal 10 to the input terminals 1, 2, 9 are the same as the leakage prevention function from the input terminal 1 to the input terminals 2, 9, 10.

  As described above, according to the high frequency cutoff circuit of the first embodiment, two transmission lines having a length of ½ wavelength in the fundamental wave component are arranged in parallel to form a coupled line, and both ends of the coupled line are formed. By connecting an open stub with a quarter wavelength in the fundamental wave component to the part, the propagation of the fundamental wave component and the odd harmonic component is suppressed before and after the junction between the coupled line and the open stub. In the coupled line that acts as a directional coupler, the coupling of the fundamental wave component, odd harmonic component, and even harmonic component is suppressed. Leakage of wave components and odd harmonic components can be prevented.

  Therefore, by applying the high frequency cutoff circuit according to the first embodiment to a gate bias circuit and a drain bias circuit of an amplifier using, for example, an FET, the fundamental wave component, the even harmonic component, and the odd harmonic from the drain bias circuit. Loop oscillation due to the wave component being coupled to the gate bias circuit can be prevented.

  Thus, since leakage of the fundamental wave component, the even harmonic component, and the odd harmonic component between the input terminals facing each other in the coupled line can be prevented, a high-density layout of the high-frequency circuit is possible. In addition, the dielectric substrate can be miniaturized by a high-density layout.

Embodiment 2. FIG.
In the high-frequency cutoff circuit according to the first embodiment, two transmission lines having a length of ½ wavelength in the fundamental wave component are arranged in parallel to form a coupled line, and a basic line is formed at each end of the two transmission lines. By connecting open stubs with a quarter wavelength length in the wave component, the propagation of the fundamental wave component and odd harmonic component is suppressed before and after the junction between the transmission line and the open stub, and directional coupling is achieved. By suppressing the coupling of the fundamental component, odd harmonic component, and even harmonic component in the coupled line that acts as a coupler, the fundamental component, even harmonic component, and odd harmonic between the input terminals facing each other in the coupled line In the high-frequency cutoff circuit according to the second embodiment, the fundamental wave component and the odd harmonic component that have leaked into each transmission line are attenuated by a fixed resistor. Further configured to improve the leakage preventing effect of the fundamental wave component and harmonic components between an input end facing the line.

FIG. 2 is a diagram of an example of the high-frequency cutoff circuit according to the second embodiment. First, the configuration of the high-frequency cutoff circuit according to the second embodiment will be described with reference to FIG. 2, high-frequency cutoff circuit 200 is coupled line 40 consisting of transmission lines 11 and 12 the characteristic impedance _{Z 0} by the length of a quarter wavelength at the fundamental wave component, the quarter wavelength at the fundamental wave component length in the coupling line 60 of characteristic impedance _{Z 0} and consisting of the transmission line 13, 14 comprising coupling line 50 and the transmission line 15 and 16 the characteristic impedance _{Z 0} by the length of a quarter wavelength at the fundamental component, is formed The The coupled line 40, the coupled line 50, and the coupled line 60 are connected in series to form a 3/4 wavelength long coupled line.

There are a junction between the transmission line 11 and the transmission line 13, a junction between the transmission line 12 and the transmission line 14, a junction between the transmission line 13 and the transmission line 15, and a junction between the transmission line 14 and the transmission line 16. , is connected one end of the fixed resistor 17, 19, 21, 23 of the respective impedance _{Z 0,} respectively, the other end of the fixed resistor 17, 19, 21, 23 are open length of a quarter wavelength at the fundamental wave component Stubs 18, 20, 22, and 24 are connected to each other. Connected to the other ends of the transmission lines 11, 12, 15, and 16 are open stubs 5, 6, 7, and 8 each having a quarter wavelength in the fundamental wave component. Note that the transmission lines 11, 12, 13, 14, 15, 16 and the open stubs 5, 6, 7, 8, 18, 20, 22, 24 are microstrip line conductors on a dielectric substrate (not shown). Can be formed.

  In the high-frequency cutoff circuit 200 configured in this way, the junction between the transmission line 11 and the open stub 5 is the input end 1, the junction between the transmission line 12 and the open stub 7 is the input end 2, and the transmission line 15 and the open stub. 6 is the input end 9, and the junction between the transmission line 16 and the open stub 8 is the input end 10. The coupled line 40, the coupled line 50, and the coupled line 60 each function as a directional coupler.

  Next, the functional operation of the high-frequency cutoff circuit 200 will be described with reference to FIG. Here, in a high frequency circuit (not shown) connected to the input terminal 1, a fundamental wave component, an even harmonic component of 1 / (2N) wavelength (N is an integer of 1 or more), and 1 / (2N + 1) wavelength A function for preventing leakage from the input terminal 1 to each of the input terminals 2, 9, 10 when a signal including odd harmonic components is handled will be described.

  First, the leakage prevention function of the fundamental wave component and the odd harmonic component will be described. In the fundamental wave component and the odd harmonic component, since the junction between the transmission line 11 and the open stub 5 can be regarded as a ground point, it is totally reflected by a high-frequency circuit (not shown) connected to the input terminal 1. However, since it is difficult to make the junction between the transmission line 11 and the open stub 5 as an ideal ground, actually, total reflection is not caused, and part of the fundamental wave component and the odd harmonic component are transmitted. Propagate to.

  The fundamental wave component and the odd harmonic component propagated to the transmission line 11 are coupled to the transmission line 12 and a part of the fundamental wave component and the odd harmonic component are propagated to the transmission line 12, and the fundamental wave component and the odd harmonic component are transmitted. Part of the signal propagates to the transmission line 13. Here, since the junction between the fixed resistor 17 and the open stub 18 can be regarded as a ground point with respect to the fundamental wave component and the odd harmonic component propagated to the transmission line 11, the fundamental wave component and the odd harmonic component are Part of the energy is terminated by the fixed resistor 17. Therefore, the energy of the fundamental wave component and the odd harmonic component propagating to the transmission line 13 is attenuated. Further, since the energy of the fundamental wave component and the odd harmonic component reflected at the junction between the fixed resistor 17 and the open stub 18 is also reduced, the energy of the fundamental wave component and the odd harmonic component propagating to the transmission line 12 is also attenuated. To do.

  The fundamental wave component and the odd harmonic component propagated to the transmission line 12 are totally reflected on the transmission line 12 side because the junction between the transmission line 12 and the open stub 7 can be regarded as a ground point. However, since it is difficult to make the junction between the transmission line 12 and the open stub 7 an ideal ground, actually, total reflection is not caused and part of the fundamental wave component and the odd harmonic component are input to the input terminal 2. Propagate to.

  On the other hand, the fundamental wave component and the odd harmonic component propagated to the transmission line 13 are coupled to the transmission line 14, and part of the fundamental wave component and the odd harmonic component propagate to the transmission line 14. Here, with respect to the fundamental wave component and the odd harmonic component propagated to the transmission line 14, the junction between the transmission line 12 and the open stub 7 is a ground point when viewed from the junction between the transmission line 14 and the fixed resistor 19. At first glance, since the transmission line 12 acts as a short stub, the transmission line 12 appears to be open. Further, the junction between the fixed resistor 19 and the open stub 20 can be regarded as a grounding point for the fundamental wave component and the odd harmonic component propagated to the transmission line 14. Therefore, the fundamental wave component and the odd harmonic component propagated to the transmission line 14 are terminated by the fixed resistor 19 and propagated to the input terminal 2.

  That is, in the process in which the fundamental wave component and the odd harmonic component propagate from the input terminal 1 to the input terminal 2, most of the energy of the fundamental wave component and the odd harmonic component leaked into the input terminal 1 is caused by the fixed resistors 17 and 19. By being terminated, the fundamental wave component and the odd harmonic component propagating from the input terminal 1 to the input terminal 2 can be attenuated.

  Further, with respect to the fundamental wave component and the odd harmonic component propagated to the transmission line 13, the junction between the transmission line 15 and the open stub 6 is seen as a ground point when viewed from the junction between the transmission line 13 and the fixed resistor 21. Since the transmission line 15 acts as a short stub, the transmission line 15 appears to be open. Further, the junction between the fixed resistor 21 and the open stub 22 can be regarded as a ground point for the fundamental wave component and the odd harmonic component propagated to the transmission line 13. Therefore, the fundamental wave component and the odd harmonic component propagated to the transmission line 13 are terminated by the fixed resistor 21 and propagated to the input terminal 9.

  That is, in the process in which the fundamental wave component and the odd harmonic component propagate from the input terminal 1 to the input terminal 9, most of the energy of the fundamental wave component and the odd harmonic component leaked into the input terminal 1 is caused by the fixed resistors 17 and 21. By being terminated, the fundamental wave component and the odd harmonic component propagating from the input terminal 1 to the input terminal 9 can be attenuated.

  Similarly, with respect to the fundamental wave component and the odd harmonic component propagated to the transmission line 14, the junction between the transmission line 16 and the open stub 8 as viewed from the junction between the transmission line 14 and the fixed resistor 23 is the ground point. At first glance, since the transmission line 16 acts as a short stub, the transmission line 16 appears to be open. Further, the junction between the fixed resistor 23 and the open stub 24 can be regarded as a ground point with respect to the fundamental wave component and the odd harmonic component propagated to the transmission line 14. Therefore, the fundamental wave component and the odd harmonic component propagated to the transmission line 14 are terminated by the fixed resistor 23 and propagated to the input terminal 10.

  That is, in the process in which the fundamental wave component and the odd harmonic component propagate from the input terminal 1 to the input terminal 10, most of the energy of the fundamental wave component and the odd harmonic component leaked into the input terminal 1 is caused by the fixed resistors 17 and 23. By being terminated, the fundamental wave component and the odd harmonic component propagating from the input terminal 1 to the input terminal 10 can be attenuated.

  Next, a function for preventing leakage of even harmonic components will be described. The even harmonic component passes through the junction between the transmission line 11 and the open stub 5 and propagates to the transmission line 11, passes through the junction between the transmission line 11 and the transmission line 13, and propagates to the transmission line 13. Propagating to the transmission line 15 through the joint between the transmission line 13 and the transmission line 15.

  When the coupled line 40, the coupled line 50, and the coupled line 60 act as ideal directional couplers for the even harmonic component, the transmission line 13 and the transmission line 13 Although no coupling occurs between the transmission line 14 and between the transmission line 15 and the transmission line 16, it is difficult to make the coupling line 40, the coupling line 50, and the coupling line 60 into an ideal directional coupler. In reality, some of the even harmonic components are coupled from the transmission line 11 to the transmission line 12 and propagated to the transmission line 12, and from the transmission line 13 to the transmission line 14 and propagated to the transmission line 14. The transmission line 15 is coupled to the transmission line 16 and propagates to the transmission line 16. Even harmonic components propagated to the transmission line 12, the transmission line 14, and the transmission line 16 are the junction between the transmission line 16 and the transmission line 14, the junction between the transmission line 14 and the transmission line 12, and the open stub 7. Propagates to the input end 2 through the joint.

  That is, in the process in which the even harmonic component propagates from the input end 1 to the input end 2, it passes from the input end 1 to the input end by passing through the coupling line 40, the coupling line 50, and the coupling line 60 acting as a directional coupler. Even harmonic components propagating to 2 can be attenuated.

  Further, the even harmonic components propagated to the transmission line 12, the transmission line 14, and the transmission line 16 are the junction between the transmission line 12 and the transmission line 14, the junction between the transmission line 14 and the transmission line 16, and the open stub 8. And propagates to the input end 10.

  That is, in the process in which the even harmonic component propagates from the input terminal 1 to the input terminal 10, it passes from the input terminal 1 to the input terminal by passing through the coupling line 40, the coupling line 50, and the coupling line 60 acting as a directional coupler. The even harmonic component propagating to 10 can be attenuated.

  On the other hand, the even harmonic components are the junction between the transmission line 11 and the open stub 5, the junction between the transmission line 11 and the transmission line 13, the junction between the transmission line 13 and the transmission line 15, and the transmission line 15 and the open. It passes through the junction with the stub 6 and propagates to the input end 9. That is, there is no leakage prevention function for even harmonic components propagating from the input terminal 1 to the input terminal 9.

  The high-frequency cutoff circuit 200 has the same configuration when viewed from any of the input terminals 1, 2, 9, and 10. Therefore, the input terminal 2 to the input terminals 1, 9, and 10, and the input terminal 9 to the input terminal 1. , 2, 10, and the leakage prevention function from the input terminal 10 to the input terminals 1, 2, 9 are the same as the leakage prevention function from the input terminal 1 to the input terminals 2, 9, 10.

  As described above, according to the high frequency cutoff circuit of the second embodiment, three coupled lines composed of two transmission lines each having a quarter wavelength in the fundamental wave component are connected in series to obtain a 3/4 wavelength. A coupling line having a length is formed, a fixed resistor is connected to the junction of each transmission line, and an open stub having a quarter wavelength in the fundamental component is connected to the other end of the fixed resistance, and three couplings are made. By connecting open stubs of 1/4 wavelength in the fundamental wave component to both ends of a 3/4 wavelength long coupled line in which the lines are connected in series, the transmission line and the open stub Suppresses the propagation of fundamental and odd harmonic components before and after the junction, suppresses coupling of even harmonic components in the coupling line that acts as a directional coupler, and further suppresses fundamental and odd harmonic components by a fixed resistor. To attenuate Since the relative first embodiment, it is possible to further improve the leakage prevention effect of the fundamental wave component and odd harmonic components between an input end facing the coupling line.

  Therefore, by applying the high-frequency cutoff circuit according to the second embodiment to a gate bias circuit and a drain bias circuit of an amplifier using, for example, an FET, the fundamental wave component, the even harmonic component, and the odd harmonic from the drain bias circuit. Loop oscillation due to the wave component being coupled to the gate bias circuit can be prevented.

  Thus, since leakage of the fundamental wave component, the even harmonic component, and the odd harmonic component between the input terminals facing each other in the coupled line can be prevented, a high-density layout of the high-frequency circuit is possible. In addition, the dielectric substrate can be miniaturized by a high-density layout.

  Note that the configuration shown in the above embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part thereof is omitted without departing from the gist of the present invention. Needless to say, it is possible to change the configuration.

  Further, in the embodiment, the contents of the invention are described for the gate bias circuit and the drain bias circuit of the amplifier using the FET, but the application field is not limited to this, and various microwave circuits are used. Needless to say, it can be applied to high-frequency circuits such as millimeter wave circuits.

  As described above, the high-frequency cutoff circuit according to the present invention is useful as an invention capable of enabling a high-density layout of a high-frequency circuit, and in particular, a fundamental wave component that propagates through a high-frequency circuit between input ends of a transmission line. It is suitable for preventing leakage of harmonic components.

DESCRIPTION OF SYMBOLS 1 Input end 2 Input end 3 Transmission line 4 Transmission line 5 Open stub 6 Open stub 7 Open stub 8 Open stub 9 Input end 10 Input end 11 Transmission line 12 Transmission line 13 Transmission line 14 Transmission line 15 Transmission line 16 Transmission line 17 Fixed Resistor 18 open stub 19 fixed resistor 20 open stub 21 fixed resistor 22 open stub 23 fixed resistor 24 open stub 30 coupled line 40 coupled line 50 coupled line 60 coupled line 100 high frequency cutoff circuit 200 high frequency cutoff circuit 200

Claims (2)

A high-frequency cutoff circuit of a high-frequency circuit composed of a dielectric substrate, a ground conductor provided on the lower surface of the dielectric substrate, and a microstrip line conductor provided on the upper surface of the dielectric substrate,
A coupled line formed of a pair of transmission lines having a length of ½ wavelength in a fundamental wave component of a high-frequency signal propagating through a high-frequency circuit and arranged in parallel with both ends as input ends;
An open stub having a length of ¼ wavelength in the fundamental wave component and formed connected to one and the other of each of the input ends;
A high-frequency cutoff circuit comprising: A high-frequency cutoff circuit of a high-frequency circuit composed of a dielectric substrate, a ground conductor provided on the lower surface of the dielectric substrate, and a microstrip line conductor provided on the upper surface of the dielectric substrate,
A coupled line formed of a pair of transmission lines having a length of 3/4 wavelength in a fundamental wave component of a high-frequency signal propagating through a high-frequency circuit and having both ends as input ends;
A first open stub having a length of ¼ wavelength in the fundamental wave component and connected to one and the other of the respective input ends;
A fixed resistor having one end connected to and disposed at one and the other of the positions having a length of ¼ wavelength from each input end in the coupling line;
A second open stub having a length of ¼ wavelength in the fundamental wave component and having one end connected to the other end of each fixed resistor;
A high-frequency cutoff circuit comprising:

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