JPH09307301A - High frequency circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency circuit capable of reducing reflection from a main constituting circuit and provided with a bias circuit. SOLUTION: The circuit is provided with the main constituting circuit 10 with a transmission cable and the bias circuit of a λ/4 length for applying bias voltage to an active element through this main constituting circuit 10. The tip of the main constituting circuit 10 where both of the AC current density of the main constituting circuit 10 and that of the bias circuit 14 are minimized and equal to each other is made a connecting point 20 between the bias circuit 14 and the main constituting circuit 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency circuit having a bias circuit.

[0002]

2. Description of the Related Art In an electric circuit including a conventional high frequency circuit, a DC voltage is applied to an active element via a bias circuit connected to a transmission line of a main constituent circuit of the high frequency circuit. Then, by making this bias circuit have a high impedance of 100Ω or more, a state close to a lossless line is achieved and the influence of disturbance noise is reduced. The length of the bias circuit is about a quarter of the wavelength of the signal propagating through the transmission line of the main constituent circuit (hereinafter also referred to as λ / 4) in order to reduce reflection from the main constituent circuit. It had been. In a high-frequency circuit including a conventional bias circuit, one end of a bias circuit having a length of λ / 4 is AC short-circuited, and the other end connected to the main constituent circuit is AC short-circuited. It was designed on the premise of an ideal state of being open.

[0003]

However, in reality, since a standing wave due to a signal propagating through the main constituent circuit exists in the main constituent circuit, the ideal state which is the premise of the above-mentioned design is Not realized. Therefore, it is difficult to reduce the reflection from the main constituent circuit simply by making the bias circuit have a high impedance.

Therefore, it has been desired to realize a high frequency circuit having a bias circuit which can reduce reflection from the main constituent circuits.

[0005]

According to the high frequency circuit of the invention of the present application, a main constituent circuit having a transmission line and a transmission circuit for applying a bias voltage to an active element via the main constituent circuit are provided. In a high-frequency circuit configured with a bias circuit including a line, the AC current density of this main constituent circuit and the AC current density of this bias circuit at the connection between this main constituent circuit and this bias circuit Characterized by equality.

According to the high frequency circuit of the present invention, reflection can be reduced by making these alternating current densities equal to each other. As a result, impedance matching between the main constituent circuit and the bias circuit can be achieved.

Further, preferably, the length of the bias circuit is set to about a quarter of the wavelength of the signal propagating through the main constituent circuit, and at this connection portion, the AC current density of the main constituent circuit and the AC current of the bias circuit. It is desirable that each of the current densities be minimum.

Further, preferably, the length of the bias circuit is set to about one half of the wavelength of the signal propagating through the main constituent circuit, and at this connection portion, the AC current density of the main constituent circuit and the AC current of the bias circuit. It is desirable that each density be maximum.

When a stub is connected to the bias circuit, the distance between the connection with the stub and the connection with the main constituent circuit is the length of the bias circuit.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a high frequency circuit according to the invention of this application will be described below with reference to the drawings. It should be noted that the drawings referred to merely schematically show the size, shape, and arrangement of each component so that the present invention can be understood. Therefore, the present invention is not limited to the illustrated example.

(First Embodiment) A high-frequency circuit according to the first embodiment will be described with reference to FIG. FIG.
FIG. 3 is a schematic top view for explaining the high-frequency circuit according to the first embodiment.

The high-frequency circuit of this embodiment comprises a main constituent circuit 10 having a transmission line which is used as a distributed constant circuit for propagating a signal of microwave, millimeter wave or higher frequency and a main constituent circuit thereof. It comprises a bias circuit 14 with a transmission line for applying a bias voltage to the active element 12 via the circuit 10.

The length of the bias circuit 14 is a quarter (λ /) of the wavelength (λ) of the signal propagating through the main constituent circuit 10.
It is about 4). In this embodiment, the bias circuit 14 is provided with the stub 16. For this reason,
The length of the bias circuit 14 is the connection point 18 with the stub 16.
From the connection portion 2 between the main constituent circuit 10 and the bias circuit 14.
It is represented by the length of the signal line up to zero.

The main constituent circuit 10 and the bias circuit 14 are composed of microstrip lines. Therefore, in the schematic top view of FIG. 1, the signal lines forming the microstrip line are shown.

Further, in this embodiment, as the active element 12, the resonance circuit 12 composed of a variable capacitance diode for changing the resonance frequency is connected to both ends of the microstrip line of the main constituent circuit. In addition, both resonance circuits 1
The characteristics of 2 are the same.

Further, in this embodiment, the connecting portion 20 is provided at the end of the microstrip line of the main constituent circuit 10.

By the way, in the bias circuit 14, the connection point 18 of the stub 16 is short-circuited in a high frequency (when a high-frequency signal propagates in the main constituent circuit), so that the AC current density is the maximum in a high frequency. Has become. On the other hand, the connecting portion 20 separated from the connecting point 18 by λ / 4 is open in terms of high frequency, and therefore the AC current density is minimum in terms of high frequency.

On the other hand, at both ends of the main constituent circuit 10, the AC current density is minimum at high frequencies. Therefore, if the end of the main constituent circuit 10 is the connection point 20, the AC current density of the main constituent circuit 10 and the AC current density of the bias circuit 14 are both minimum and equal to each other. Therefore, the connecting portion 2
The reflection from 0 can be reduced.

(Second Embodiment) Next, a high-frequency circuit according to a second embodiment will be described with reference to FIG.
FIG. 2 is a schematic top view for explaining the high-frequency circuit according to the second embodiment.

The high-frequency circuit of this embodiment includes a main circuit 10 having a transmission line and a bias circuit having a transmission line for applying a bias voltage to the active element 12 via the main circuit 10. It is configured with 24.

The length of the bias circuit 24 is half the wavelength (λ) of the signal propagating through the main constituent circuit 10 (λ /
It is about 2). In this embodiment, the bias circuit 24 is provided with the stub 16. For this reason,
The length of the bias circuit 24 is the connection point 18 with the stub 16.
From the connecting portion 2 between the main constituent circuit 10 and the bias circuit 24.
It is represented by lengths up to 6.

The main constituent circuit 10 and the bias circuit 24 are constituted by microstrip lines. Therefore, in the schematic top view of FIG. 2, the signal lines forming the microstrip line are shown.

Further, in this embodiment, as the active element 12, the resonance circuit 12 composed of a variable capacitance diode for changing the resonance frequency is connected to both ends of the microstrip line of the main constituent circuit. In addition, both resonance circuits 1
The characteristics of 2 are the same.

In this embodiment, the connecting portion 26 is provided at the central portion (equal distance from both ends) of the microstrip line of the main constituent circuit 10.

By the way, in the bias circuit 24, the connection point 18 of the stub 16 is short-circuited at high frequency (when a high-frequency signal propagates through the main constituent circuit), so that the AC current density becomes maximum at high frequency. Has become. Further, the connecting portion 26 separated from the connecting point 18 by λ / 2 is also short-circuited in terms of high frequency, so that the AC current density becomes maximum in terms of high frequency.

On the other hand, since the resonant circuits 12 having the same characteristics are connected to both ends of the main constituent circuit 10, respectively.
In the central portion of the main constituent circuit 10, the AC current density is maximum at high frequencies. Therefore, if the central portion of the main constituent circuit 10 is used as the connecting portion 26, the AC current density of the main constituent circuit 10 and the AC current density of the bias circuit 24 both become maximum and equal to each other. Therefore, the reflection from the connecting portion 26 can be reduced.

When the characteristics of the resonance circuits (capacitance of the variable capacitance diode) connected to both ends of the main constituent circuit 10 are not equal to each other, for example, the internal division ratio on the signal line of the main constituent circuit is It is conceivable to use a position where the reciprocal of the capacitance ratio of the variable capacitance diode is equal to the connection portion.

In each of the above-described embodiments, examples in which these inventions are configured under specific conditions have been described. However, many modifications and variations can be made to these inventions. For example, in the above-described embodiment, the transmission line of the high frequency circuit is configured by the microstrip line, but in the present invention, the type of transmission line is not limited to this,
For example, the transmission line may be a strip line or a coplanar line.

[0029]

According to the high frequency circuit of the invention of this application, the main constituent circuit and the bias circuit are connected at a position where the AC current density of the main constituent circuit and the AC current density of the bias circuit are equal. . Therefore, it becomes possible to suppress the reflection and apply the voltage from the bias circuit to the main constituent circuit.

[Brief description of drawings]

FIG. 1 is a schematic top view for explaining a first embodiment.

FIG. 2 is a schematic top view for explaining the second embodiment.

[Explanation of symbols]

 10: Main configuration circuit 12: Active element (resonant circuit) 14: Bias circuit 16: Stub 18: Connection point 20: Connection part 24: Bias circuit 26: Connection part

Claims (3)

[Claims] 1. A high-frequency circuit configured by a main constituent circuit having a transmission line and a bias circuit having a transmission line for applying a bias voltage to an active element via the main constituent circuit. In the high frequency circuit, the AC current density of the main constituent circuit is equal to the AC current density of the bias circuit in the connection portion between the main constituent circuit and the bias circuit. 2. The high-frequency circuit according to claim 1, wherein the bias circuit has a length of about a quarter of a wavelength of a signal propagating through the main constituent circuit, and the connecting portion has the main constituent. A high-frequency circuit characterized in that the alternating current density of the circuit and the alternating current density of the bias circuit are respectively minimum. 3. The high frequency circuit according to claim 1, wherein the bias circuit has a length of about one half of a wavelength of a signal propagating through the main constituent circuit, and the main constituent circuit is provided in the connection portion. The high-frequency circuit is characterized in that the AC current density and the AC current density of the bias circuit are respectively maximum.