JPH06276038A - High frequency low noise amplifier - Google Patents

Abstract

PURPOSE:To satisfy the best values of a noise index and an input voltage standing wave ratio and to preclude an oscillation phenomenon wherein the operation of an FET becomes unstable in a frequency range higher than a necessary frequency band. CONSTITUTION:The high frequency low noise amplifier consisting of a microstrip line 9 which connects the source terminal 4 of an FET 1 to the ground is provided with a tip open line 12 composed of a lambda/4 microstrip line at the source terminal 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency low noise amplifier composed of a microwave integrated circuit using a field effect transistor (FET).

[0002]

2. Description of the Related Art Conventionally, in a microwave band amplifier, a FET is used as an active element, a matching circuit composed of a microstrip line is connected to each of a gate terminal and a drain terminal of the FET, and a source terminal is grounded. Low noise amplifiers of known construction are known.

FIG. 3 shows an embodiment of the high frequency low noise amplifier described above. In FIG. 3, 1 is a FET, 2 is the FE
T gate terminal, 3 FET drain terminal, 4 FET source terminal, 5 input matching circuit, 6 output matching circuit, 7 input terminal, 8 output terminal, 9 inductance component adding micro A strip line, 10 is a through hole for grounding, and 11 is a substrate for a high frequency circuit.

Next, the operation will be described. A negative DC voltage is applied to the gate terminal 2 of the FET 1 and a positive DC voltage is applied to the drain terminal 3. In this state, by the input matching circuit 5 and the output matching circuit 6, F in the required frequency band
If the input / output impedance of ET1 and the circuit connected to the outside are matched, the signal input from the input terminal 7 is efficiently amplified and output from the output terminal 8.

[0005]

In the conventional configuration, the FE
When T is directly grounded, the noise parameter Γ _opt ^* and the S parameter S ₁₁ are different. Therefore, an inductance component is added by a microstrip line between the source terminal of the FET and the ground, and the noise parameters Γ _opt ^* and S of the FET are added. Although the parameters S ₁₁ are made to coincide with each other and the best values of the noise figure (hereinafter referred to as NF) and the input voltage standing wave ratio (hereinafter referred to as VSWR) are satisfied at the same time, There is a problem that the FET becomes unstable in a high frequency region and an oscillation phenomenon is likely to occur. Further, since the source terminal is grounded, there is a problem that two types of DC voltage, that is, a DC negative voltage and a DC positive voltage must be applied to the gate terminal and the drain terminal of the FET, respectively.

The present invention has been made in order to solve the above-mentioned problems, and secures the stability of the amplifier while simultaneously satisfying the best values of NF and input VSWR, and operates with one kind of DC voltage. The aim is to obtain a possible high frequency low noise amplifier.

[0007]

A high-frequency low-noise amplifier according to the present invention is one in which an open-ended line is connected to the source terminal of an FET.

In the high frequency low noise amplifier according to the present invention, the FET short circuit line is connected to the input matching circuit,
The chip capacitor and the variable resistor are connected to the ground connection portion of the microstrip line that connects between the source terminal and the ground.

[0009]

The high frequency low noise amplifier according to the present invention is FE
FE to which an inductance component is added by a microstrip line between the source terminal of T and ground
By further connecting an open-ended line to the source terminal of T, the best value of NF and input VSWR can be satisfied at the same time, and the FET can be used in a frequency range higher than the required frequency band.
It prevents the oscillation phenomenon that the operation of becomes unstable and secures the stability of the amplifier.

The high-frequency low-noise amplifier according to the present invention is a high-frequency amplifier composed of a microstrip line connecting a source terminal of an FET and a ground, wherein a tip short-circuit line is connected to the input matching circuit, Also, by connecting the chip capacitor and the variable resistor to the space of the ground connection portion of the microstrip line that connects the source terminal of the FET and the ground,
F just by applying a positive DC voltage to the drain terminal of the FET
Allow ET to work.

[0011]

EXAMPLES Example 1. An embodiment of the present invention will be described below. In FIG. 1, 1 is FET, 2 is FET gate terminal, 3 is FET drain terminal, 4 is FET source terminal, 5 is input matching circuit, 6 is output matching circuit, 7 is input terminal, 8 is output terminal, Reference numeral 9 is a microstrip line for adding an inductance component, 10 is a through hole for grounding, 11 is a substrate for a high frequency circuit, and 12 is an open-ended line.

In the above embodiment, a negative DC voltage is applied to the gate terminal 2 of the FET 1 and a positive DC voltage is applied to the drain terminal 3, and in this state the input matching circuit 5 and the output matching circuit 6 are applied.
Therefore, if the input / output impedance of the FET 1 in the required frequency band and the circuit connected to the outside are matched, the high frequency signal input from the input terminal 7 is the FET.
The signal is amplified by the amplifying action of 1 and is output from the output terminal 8. By connecting the microstrip line 9 for adding an inductance component between the source terminal 4 of the FET 1 and the through hole for grounding, the noise parameter Γ of the FET is It is exactly the same as the conventional high frequency low noise amplifier in that _opt ^* and the S parameter S ₁₁ can be matched and the best values of NF and input VSWR can be satisfied at the same time.

However, in this conventional high frequency low noise amplifier, since the microstrip line 9 for adding the inductance component is connected between the source terminal 4 of the FET 1 and the through hole for grounding, the frequency band is higher than the required frequency band. In the frequency region, the FET becomes unstable and the oscillation phenomenon easily occurs. The thing to suppress this phenomenon is F
The open-ended line 12 is connected to the source terminal 4 of the ET1. This open-ended line 12 is composed of a λ / 4 microstrip line at a high frequency causing oscillation, and is a FET at a high frequency causing oscillation.
1 is grounded equivalently to stabilize the FET. At the required frequency, the open-ended line 12 has a length that can be almost ignored, so that the characteristics as a low noise amplifier are not affected at all, and the optimum NF is obtained.
And the input VSWR can always be obtained stably.

Example 2. 2 is a diagram showing another embodiment of the present invention. In FIG. 2, 1 is a FET, 2 is a FET gate terminal, 3 is a FET drain terminal, 4 is a FET source terminal, 5 is an input matching circuit, 6 is an output matching circuit, 7
Is an input terminal, 8 is an output terminal, 9 is a microstrip line for adding an inductance component, 10 is a through hole for ground grounding, 11 is a substrate for a high frequency circuit, 12 is a tip open line, 13 is a tip short circuit line, and 14 is a chip capacitor. ,
Reference numeral 15 is a variable resistor.

In the second embodiment, the conventional high frequency low noise amplifier has the source terminal of the FET 1 grounded and the gate terminal 2 connected.
A negative DC voltage and a positive DC voltage to the drain terminal 3 to bias the FET1 to operate, whereas the FE
F just by applying a positive DC voltage to the drain terminal 3 of T1
Allow ET1 to operate.

The specific method is to add a chip capacitor 14 having a capacitance that causes a short circuit at a required frequency to the space of the microstrip line 9 connected to add an inductance component, and to add a DC component to the source terminal. 4 is floated, and instead the tip short circuit 13 is added to the input matching circuit 5 to ground the gate terminal 2 with a DC component, and the variable resistor 15 is connected in parallel to the chip capacitor 14. As a result, when a DC positive voltage is applied to the drain terminal 3, a current flows through the variable resistor 15, and due to this voltage drop, the source terminal 4 becomes a positive potential and the tip short circuit 13
As a result, a negative voltage is applied to the gate terminal 2 which is grounded with respect to the source terminal, and by appropriately selecting the resistance value of the variable resistor 15, the FET 1 is biased in the same manner as the conventional one, and only a DC positive voltage is applied. Can work.

[0017]

As described above, according to the present invention, the FE
FE to which an inductance component is added by a microstrip line between the source terminal of T and ground
By further connecting an open-ended line to the source terminal of T, the best value of NF and input VSWR can be satisfied at the same time, and the FET can be used in a frequency range higher than the required frequency band.
This has the effect of preventing the oscillation phenomenon that the operation of becomes unstable and ensuring the stability of the amplifier.

Further, in a high frequency amplifier composed of a microstrip line connecting the source terminal of the FET and the ground, a tip short-circuit line is connected to the input matching circuit, and the source terminal of the FET is connected to the ground. By connecting the chip capacitor and variable resistor to the space of the ground connection part of the microstrip line,
The FET can be operated only by the DC positive voltage, and there is an effect that a small-sized and low-cost low-noise amplifier can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a high frequency low noise amplifier showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a high frequency low noise amplifier showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional high frequency low noise amplifier.

[Explanation of symbols]

 1 FET 2 Gate Terminal 3 Drain Terminal 4 Source Terminal 5 Input Matching Circuit 6 Output Matching Circuit 7 Input Terminal 8 Output Terminal 9 Microstrip Line 10 Ground Ground Through Hole 11 High Frequency Circuit Board 12 Tip Open Line 13 Tip Shorting Line 14 Chip Capacitor 15 Variable resistor

Claims (2)

[Claims] 1. A field effect transistor (FET), an input matching circuit connected to a gate terminal of the FET, and an output matching circuit connected to a drain terminal of the FET.
A high-frequency low-noise amplifier comprising a microstrip line connecting a source terminal of the FET and a ground, wherein the open-ended line is connected to the source terminal of the FET. 2. A field effect transistor (FET), an input matching circuit connected to a gate terminal of the FET, and an output matching circuit connected to a drain terminal of the FET.
A high-frequency low-noise amplifier including a microstrip line connecting a source terminal of the FET and a ground, wherein a tip short-circuit line connected to the input matching circuit and a source terminal of the FET and the ground are connected. A high-frequency low-noise amplifier comprising a chip capacitor and a variable resistor connected to a ground connection portion of a microstrip line for connecting to.