JPS63244906A - Bias circuit - Google Patents

Abstract

PURPOSE:To obtain a bias circuit with low loss in an available frequency band area and superior reflection loss outside the band area, by branching and connecting a transmission line (Tme) with 1/4-wave to a high frequency signal line, and connecting an open stub with 1/4-wave and the Tme terminated by a terminating resistor to the tip of the Tme. CONSTITUTION:The bias circuit is constituted in such a way that branching is performed by connecting the Tme1 to the high frequency signal line, and the open stub 2 with 1/4-wave and the Tme3 terminated by the terminating resistor 4 are connected to the tip of the Tme 1. To the terminating resistor 4, a high frequency short-circuited capacitor 5 and a choke coil 6 are connected, and a bias power source Vs is connected. In such constitution, a passing characteristic and a reflection loss characteristic observed from a high frequency line 11 are released by the Tme1 and the open stub 2 with 1/4-wave at the available frequency band area, then, the passing characteristic disappears. Also, reflection resistance is improved by the Tme3, the terminating resistor 4, and the capacitor 5 outside the band area.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a bias circuit in a high frequency active circuit such as an amplifier, and particularly relates to a bias circuit that has low loss within the frequency band used and good return loss outside the band. .

[Conventional technology]

Conventionally, bias circuits connected to signal lines of high-frequency active circuits such as amplifiers have been configured with 1/4 transmission lines with shorted ends, choke coils, etc. in order to reduce the influence within the frequency band used and supply bias. taking it.

[Problem that the invention seeks to solve]

The conventional bias circuit described above has poor reflection loss outside the frequency band used, and in some cases may result in complete reflection. For this reason, when this type of bias circuit is used in an amplifier, etc., problems such as oscillation may occur, and in order to eliminate such out-of-band effects, a dedicated separate connection is required. has been done.

An object of the present invention is to provide a bias circuit that has low loss within the frequency band used and good reflection loss outside the band.

[Means for solving problems]

The bias circuit of the present invention branches and connects a 1/4 wavelength transmission line to a high frequency signal line.
The wavelength transmission line has a configuration in which a 1/4 wavelength open stub is connected to the tip of the wavelength transmission line and a 1/4 wavelength transmission line terminated by a terminating resistor. [Example] Next, the present invention will be explained with reference to the drawings. explain.

FIG. 1 is a diagram showing the configuration of a bias circuit according to the present invention.

As shown in the figure, a 1/4 wavelength transmission line 1 is connected to a high frequency signal line 11 to perform branching.
A 1/4 wavelength open stub 2 is placed at the tip of the /4 wavelength transmission line 1, and I is terminated by a terminating resistor 4.
/4 wavelength transmission line 3 is connected.

A high frequency short-circuit capacitor 5 and a choke coil 6 are connected to the terminal resistor 4, which is connected to a bias power source 8.

In this configuration, the transmission characteristics and reflection loss characteristics as seen from the high frequency signal line 11 are shown in FIG.

That is, the frequency band used is opened by the 1/4 wavelength transmission line 1 and the 1/4 wavelength open stub 2, and there is no passing loss (attenuation characteristic). Also, outside the band, there is a 1/4 wavelength transmission 3 and a terminating resistor 4. Reflection loss is improved by capacitor 5.

These allow band-limiting characteristics to be obtained.

Also, when designing, 1/4 wavelength transmission line 1
．． By arbitrarily setting the impedance of the 1/4 wavelength open stub 2, the bandwidth can be changed.

〔Effect of the invention〕

As explained above, the present invention provides a high-frequency signal line with a
The 4-wavelength transmission line is branched and connected, and this 1
A 1/4 wavelength open stub and a 1/4 wavelength transmission line terminated by a terminating resistor are connected to the tip of the 4 wavelength transmission line, so even when used in high frequency active circuits such as amplifiers, the operating frequency band can be maintained. In addition to having low loss within the band, it is effective in improving reflection tM loss outside the band and preventing effects outside the band such as out-of-band oscillation.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the bias circuit of the present invention, and FIG. 2 shows the amount of attenuation in the signal line. FIG. 3 is a frequency characteristic diagram of reflection loss. 1...1/4 wavelength transmission line, 2...
・1/4 wavelength open stub, 3...1/4 wavelength transmission line, 4...Terminal resistor, 5...High frequency short circuit capacitor, 6...Choke coil, 11.
...High frequency signal line. Figure 1 Funwo'funfu

Claims (1)

[Claims] (1) In a bias circuit connected to a high frequency signal line, a 1/4 wavelength transmission line is branch-connected to the high frequency signal line, and a 1/4 wavelength open stub and a terminating resistor are connected to the tip of this 1/4 wavelength transmission line. A bias circuit characterized by connecting a terminated 1/4 wavelength transmission line.