JP3129274B2 - High frequency circuit impedance conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for converting impedance at a signal input terminal of a high-frequency active element to which a bias voltage is supplied together with a high-frequency signal.

[0002]

2. Description of the Related Art FIG. 3 is a plan view showing the periphery of an amplifier circuit constituted by high-frequency active elements. High frequency active element 10
2 is, for example, a field effect transistor (FET)
And constitutes a high-frequency signal amplifier circuit. The signal input terminal 104 (gate) is connected to a strip line 108 formed on a circuit board 106 made of an insulating material.

A bias circuit 1 is also provided on a circuit board 106.
The bias circuit 110 includes an inductance element 112, a chip capacitor 114, and a 1/4 wavelength open stub 116. The inductance element 112 is formed of a pattern made of a conductive material (also referred to as a conductive pattern) formed on the circuit board 106, and has a length substantially equal to a quarter wavelength of the high-frequency signal. One end of the inductance element 112 is connected to a location near the signal input terminal 104 of the strip line 108, and the other end is connected to the power supply connection point 1.
18. The chip capacitor 114 is for a low frequency, has a relatively large capacitance so as to have a sufficiently low impedance at a low frequency, and has one end connected to the power supply connection point 118 and the other end formed on the circuit board 106. Connected to the ground pattern 120.
The 波長 wavelength open stub 116 is formed of a conductive pattern formed on the circuit board 106, has a length substantially equal to １ ／ wavelength of the high frequency signal, and has one end connected to the power supply connection point 1.
18.

In such a configuration, a strip line 10 is connected to a signal input terminal 104 of the high-frequency active element 102.
An appropriate bias voltage is applied from the bias circuit 110 through 8, and the high-frequency signal supplied via the strip line 108 is amplified by the high-frequency active element 102.

Here, since the inductance element 112 has a low impedance with respect to the bias voltage and the chip capacitor 114 has a high impedance with respect to the bias voltage, the bias voltage supplied to the power supply connection point 118 is Inductance element 112, chip capacitor 114, and 1/4 wavelength open stub 11
High-frequency active element 10 without being affected by 6
2 signal input terminals. On the other hand, the inductance element 112 has a high impedance with respect to the high-frequency signal, and the power supply connection point 118 is equivalently opened with respect to the high-frequency signal by the action of the open stub 116. Is for low frequency, and the function as a capacitor deteriorates for high frequency signals and becomes high impedance, so that the bias circuit 110 does not affect high frequency signals.

[0006]

However, the power supply connection point 1
When low-frequency noise is mixed in the bias voltage supplied from the
Is not always sufficiently suppressed, and low-frequency noise may be input to the high-frequency active element 102 through the low-impedance inductance element 112 and adversely affect the low-frequency noise. In particular, in recent years, since the output of the high-frequency active element 102 has been increased and the bias current has been increased, the power level of low-frequency noise mixed into the bias has also been increased.
As a result, the bias circuit 110 and the high-frequency active element 1
There is a problem that the bias voltage applied to the high-frequency active element 102 oscillates at a low frequency due to the resonance 02, and adversely affects the high-frequency signal. One way to solve this problem is to reduce the impedance from the power supply connection point 118 to the signal input terminal 104 as much as possible, while this impedance must be high for high frequency signals. It is difficult to lower the impedance from the power supply connection point 118 to the signal input terminal 104 while satisfying the conditions.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to suppress a low frequency noise mixed in a bias voltage and prevent a bias voltage from oscillating at a low frequency. An object of the present invention is to provide an impedance conversion circuit for a circuit.

[0008]

In order to achieve the above object, the present invention provides a circuit for converting impedance at a signal input terminal of a high-frequency active element to which a bias voltage is supplied together with a high-frequency signal. Comprising one or more series circuits, wherein the series circuit is connected between the signal input terminal and ground,
The inductance element is formed of a conductive pattern formed on a circuit board made of an insulating material, the length of the conductive pattern is substantially equal to a quarter wavelength of the high-frequency signal, and the capacitor is connected to the high-frequency signal. Exhibiting an impedance substantially equal to a short circuit at a lower frequency and having one end connected to one end of the inductance element,
The signal input terminal is supplied with the high-frequency signal through a strip line formed on the circuit board, the bias voltage is supplied from a bias circuit, and the bias circuit is connected to a power supply provided on the circuit board. A point, which is formed on the circuit board, connects the power supply connection point to the strip line, and has a length of one of the high-frequency signals.
A second conductive pattern substantially equal to パ タ ー ン wavelength, and a second capacitor connected between the ground pattern formed on the circuit board and the power supply connection point. I do. Since the inductance element has a high impedance with respect to a high-frequency signal, even if the series circuit is connected to the signal input terminal of the high-frequency active element, there is no effect on the high-frequency signal. Further, since the series circuit includes a capacitor and does not flow a bias current, there is no influence such as a fluctuation of a bias voltage. However, since the inductance element has low impedance for low-frequency noise and the capacitor has low impedance as well, the signal input terminal has low impedance for low-frequency noise, and it is shorted to ground. Become equivalent. As a result, low frequency noise is prevented from being input to the high frequency active element,
Low frequency vibration caused by low frequency noise can be prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a plan view showing the periphery of a high-frequency active element to which an example of an impedance conversion circuit of a high-frequency circuit according to the present invention is connected. In the figure,
The same elements as those in FIG. 3 are denoted by the same reference numerals, and a detailed description thereof will be omitted here. FIG. 1 is FIG.
The difference is that the impedance conversion circuit 2 of the high-frequency active element 102 is added.

The impedance conversion circuit 2 of this high-frequency circuit is a circuit for converting the impedance at the signal input terminal 104 of the high-frequency active element 102 to which the bias voltage is supplied together with the high-frequency signal. The series circuit 8 includes a signal input terminal 104 of the high-frequency active element 102.
And the ground pattern 1 formed on the circuit board 106
0. The high-frequency signal is, for example, a signal in a microwave band or a millimeter-wave band.
Is a field effect transistor in this embodiment, and constitutes an amplifier circuit in this embodiment. The signal input terminal 104 is a gate of the high-frequency active element 102. Note that the high-frequency active element 102 may be a bipolar transistor, in which case the signal input terminal 104 serves as a base.

The inductance element 4 is formed of a conductive pattern formed on a circuit board 106 made of an insulating material, and the length of the conductive pattern is 1 / the length of a high-frequency signal input to the high-frequency active element 102. It is almost equal to 4 wavelengths. The chip capacitor 6 has a relatively large capacitance so as to have a sufficiently low impedance at a low frequency.

In such a configuration, since the inductance element 4 has a high impedance to a high-frequency signal, the series circuit 8 (that is, the high-frequency active element 102
Of the high-frequency active element 102
Connected to the signal input terminal 104 has no effect on the high-frequency signal. Further, since the series circuit includes the chip capacitor 6 and therefore does not flow the bias current, there is no influence such as a change in the bias voltage.
However, since the inductance element 4 has low impedance and the chip capacitor 6 also has low impedance with respect to low frequency noise included in the bias voltage from the bias circuit 110, the impedance at the signal input terminal 104 is low frequency noise. , And becomes equivalent to a state in which the signal input terminal 104 is short-circuited to the ground. As a result, low-frequency noise is prevented from being input to the high-frequency active element 102, and low-frequency vibration caused by low-frequency noise can be prevented.

In this embodiment, only one series circuit of the inductance element 4 and the chip capacitor 6 is connected, but as shown in FIG. By connecting a plurality of series circuits 8 therebetween, the impedance at the signal input terminal 104 against low-frequency noise can be further reduced, and a further vibration prevention effect can be obtained.

[0014]

As described above, the present invention relates to a circuit for converting impedance at a signal input terminal of a high-frequency active element to which a bias voltage is supplied together with a high-frequency signal, wherein one or more of an inductance element and a capacitor are provided. Wherein the series circuit is connected between the signal input terminal and the ground, and the inductance element is formed by a conductive pattern formed on a circuit board made of an insulating material; The length of the capacitor is substantially equal to a quarter wavelength of the high-frequency signal, the capacitor has an impedance substantially equal to a short circuit at a lower frequency than the high-frequency signal, and one end is connected to one end of the inductance element. The high-frequency signal through a strip line formed on the circuit board. The bias voltage is supplied from a bias circuit, and the bias circuit includes a power supply connection point provided on the circuit board, a power supply connection point formed on the circuit board, and the strip line. A second conductive pattern connected and having a length substantially equal to a quarter wavelength of the high frequency signal, and a second capacitor connected between a ground pattern formed on the circuit board and the power supply connection point And characterized in that: Since the inductance element has a high impedance with respect to the high-frequency signal, even if the series circuit is connected to the signal input terminal of the high-frequency active element, there is no effect on the high-frequency signal. Further, since the series circuit includes a capacitor and does not flow a bias current, there is no influence such as a change in a bias voltage. However, since the inductance element has low impedance for low-frequency noise and the capacitor has low impedance as well, the signal input terminal has low impedance for low-frequency noise, and it is shorted to ground. Become equivalent. As a result, low-frequency noise is prevented from being input to the high-frequency active element, and low-frequency vibration caused by low-frequency noise can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view showing a periphery of a high-frequency active element to which an example of an impedance conversion circuit of a high-frequency circuit according to the present invention is connected.

FIG. 2 is a plan view showing another embodiment of the present invention.

FIG. 3 is a plan view showing the periphery of an amplifier circuit constituted by high-frequency active elements.

[Explanation of symbols]

2 ... impedance conversion circuit, 4 ... inductance element, 6 ... chip capacitor, 8 ... series circuit, 10
... Ground pattern, 102 high-frequency active element, 1
04 ... signal input terminal, 106 ... circuit board, 108 ...
... strip line, 110 ... bias circuit, 112
...... Inductance element 114 114 Chip capacitor 116 1/4 wavelength open stub 118
Power supply connection point, 120: ground pattern.

Claims (6)

(57) [Claims] 1. A circuit for converting impedance at a signal input terminal of a high-frequency active element to which a bias voltage is supplied together with a high-frequency signal, comprising: one or more series circuits of an inductance element and a capacitor; is connected between said signal input terminal and ground, the inductance element, the circuit board made of an insulating material
The conductive pattern formed on the conductive pattern,
The length of the conductive pattern is approximately 1/4 wavelength of the high frequency signal.
The capacitors are approximately equal at a lower frequency than the high frequency signal.
Has the same impedance as a short circuit and one end
The signal input terminal is connected to one end of the inductance element, and the signal input terminal is connected to a switch formed on the circuit board.
The high-frequency signal is supplied through a trip line, and the bias voltage is supplied from a bias circuit.
The bias circuit is a power supply connection point provided on the circuit board.
And the power supply connection point formed on the circuit board and the
Connected to a strip line and the length is one of the high frequency signals
A second conductive pattern substantially equal to ４ wavelength;
Ground pattern formed on the circuit board and the power connection
An impedance conversion circuit for a high-frequency circuit, comprising a second capacitor connected between the point and a second capacitor . 2. The impedance conversion circuit according to claim 1, wherein the high-frequency signal is a signal in a microwave band or a millimeter wave band. 3. The impedance conversion circuit according to claim 1, wherein the high-frequency active element is a transistor. 4. The impedance conversion circuit according to claim 3, wherein the signal input terminal is a base or a gate of the transistor. 5. The impedance conversion circuit according to claim 3, wherein the transistor forms an amplification circuit. 6. The impedance conversion circuit according to claim 1, wherein said capacitor is a chip capacitor.