JPH10303661A - Low noise amplifier employing microwave monolithic ic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent noise figure characteristic by decreasing a parasitic resistive component, in an input matching circuit in a form of not much disturbing monolithic IC processing. SOLUTION: An integrated circuit 16 is provided with an input matching circuit 17 or the like having an amplifier FET 1 and a series spiral inductor 7, and an externally mounted inductor component 18 is placed at the outside of the integrated circuit 16 as a component of the input matching circuit 17 in place of a conventional parallel spiral inductor. Thus, the parasitic resistive component of the parallel inductor 18 in the input matching circuit 17 is reduced more than that of the conventional parallel spiral inductor and the noise figure is greatly enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave monolithic integrated circuit (MMIC) low-noise amplifier, and more particularly to an integrated circuit capable of suppressing insertion loss in an input matching circuit of a low-noise amplifier.

[0002]

2. Description of the Related Art Microwave monolithic ICs (Microwav
e Monolithic IC) circuit is a microwave integrated circuit (Mic
rowave IC), and an MMIC-based low-noise amplifier has a configuration as shown in FIG.

FIG. 3 shows an example of a conventional MMIC-based low noise amplifier, in which a field effect transistor (hereinafter referred to as FET) 1 is arranged as an amplifying transistor.
One source (electrode) is connected to ground via a DC preventing capacitor 2 and a self-bias resistor 3 connected in parallel. An input matching circuit 5 is connected between the gate of the FET 1 and the input terminal 4, and a direct current preventing capacitor 6 and a A series spiral inductor 7 is connected in series, and a parallel spiral inductor 8 is connected between a connection point between the capacitor 6 and the series spiral inductor 7 and the ground.

An output matching circuit 10 is connected between the drain of the FET 1 and the output terminal 9. The output matching circuit 10 includes a series connection between the drain of the FET 1 and the output terminal 9. The spiral inductor 11 and the DC preventing capacitor 12 are connected in series, and a parallel spiral inductor 14 is connected between a connection point between the series spiral inductor 11 and the capacitor 12 and the drain bias terminal 13.

In such a low-noise amplifier, the noise figure is determined by the impedance of the input matching circuit 5 and the insertion loss thereof (the effect of the output matching circuit 10 is not so large). The capacitors 6 in the input matching circuit 5,
The value of each element of the series spiral inductor 7 and the parallel spiral inductor 8 is set.

[0006]

However, in the microwave monolithic IC low-noise amplifier, the parasitic resistance components present in the spiral inductors 7 and 8 of the input matching circuit 5 are other inductor elements such as a single chip inductor. This large parasitic resistance component causes a considerable loss of a high-frequency signal. That is, since the insertion loss of the input matching circuit 5 increases as the parasitic resistance component increases, the noise figure of the noise figure increases in accordance with the increase in the parasitic resistance component due to the use of the spiral inductors 7 and 8. There is a problem that deterioration occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce the parasitic resistance component of an inductor in an input matching circuit so as not to hinder the formation of a monolithic IC. An object of the present invention is to provide a microwave monolithic IC low-noise amplifier capable of obtaining an exponential characteristic.

[0008]

In order to achieve the above object, the present invention provides a microwave monolithic IC low-noise amplifier comprising a microwave monolithic IC including an input matching circuit and an amplifying transistor. The matching circuit is characterized in that a parallel inductor, one end of which is connected to a high-frequency ground, is disposed outside the microwave monolithic IC chip as an external inductor component (element).

As shown in the conventional circuit of FIG. 3, a series inductor and a parallel inductor are provided in the input matching circuit. However, when the amplifying transistor is viewed from the input side, the impedance of the series inductor is high in a high-frequency signal. The influence of the impedance of the parallel inductor is greater than that of the parallel inductor, and the parasitic resistance of the parallel inductor has a greater effect on the noise figure among these parasitic resistances. Therefore, the present invention uses only a parallel inductor as an external component so that the parasitic resistance of the parallel inductor is reduced, and thereby a good noise figure can be obtained.

[0010]

FIG. 1 shows an example of a microwave monolithic IC-based low noise amplifier according to an embodiment. A circuit surrounded by 16 in FIG. 1 is an integrated circuit (MMI).
C). This integrated circuit 16 has F
An ET (field effect transistor) 1 is arranged, and the FE
A parallel DC preventing capacitor 2 and a self-bias resistor 3 are connected between the source of T1 and the ground. Further, an input terminal 4 and an output terminal 9 are provided, an input matching circuit 17 is connected between the input terminal 4 and the gate of the FET1, and an output matching circuit is connected between the drain of the FET1 and the output terminal 9. 10 is connected.

In the output matching circuit 10, a series spiral inductor 11, a DC preventing capacitor 12, and a parallel spiral inductor 14 are provided, and the other terminal of the spiral inductor 14 is connected to a drain bias terminal 13. . Then, one input matching circuit 1
7, a DC preventing capacitor 6 and a series spiral inductor 7 are arranged as shown in FIG.
Are not formed.

In the embodiment, in the input matching circuit 17, instead of the conventional spiral inductor, an external inductor element (chip inductor) 18 is provided outside the integrated circuit 16 as shown in FIG. It is provided between the connection point between the DC preventing capacitor 6 and the series spiral inductor 7 and the ground.

According to the MMIC-based low-noise amplifier, impedance matching at the time of inputting microwaves is performed by the input matching circuit 17, and the microwave signal amplified by the FET 1 is output by the output matching circuit 10 at the time of output. Is performed. In the input matching circuit 17 described above, since the external inductor element 18 having a small parasitic resistance component is mounted as a parallel spiral inductor, the entire parasitic resistance component of the input matching circuit 17 is reduced.

For example, while the parasitic resistance component of the parallel spiral inductor (8) in the conventional circuit of FIG. 3 is about 5Ω, the parasitic resistance component of the external inductor element 18 is about 0.35Ω. Therefore, in the circuit of the embodiment, the insertion loss is significantly improved as compared with the circuit of FIG.
Thus, an amplified signal with low loss and low noise can be obtained.

FIG. 2 shows the frequency characteristic of the noise figure of the amplifier of FIG. 1 compared with the amplifier of FIG. 3, and the curve A is the characteristic of the example of FIG. Curve C of the conventional example 3 is a characteristic when the series spiral inductor 7 in the input matching circuit 17 of FIG. 1 is also replaced with an external chip inductor. Comparing the curves A and B, it is understood that the noise figure of the example is significantly improved in the band centered on the design frequency f0 as compared with the conventional example.

Furthermore, low noise characteristics are obtained which are almost equal to those of the curve C in which the parallel and series spiral inductors are replaced with external inductor elements. This is because, as described above, when the FET 1 is viewed from the input terminal 4, the impedance of the parallel inductor 16 has a greater effect on the high-frequency signal than the impedance of the series inductor 7, and the parasitic resistance of only the parallel inductor 16 is reduced to about 0.1. This is because the noise figure can be satisfactorily reduced by reducing the value to 35Ω. Further, from a different point of view, externally providing both the parallel and series inductors leads to an increase in the number of components and impedes the promotion of integrated circuit, which is not preferable.

Further, the above parallel inductor is integrated with an integrated circuit 1
The external inductor element 18 of FIG. 6 also has the following advantages. That is, the frequency f0 at which the noise figure becomes minimum in the curve A in FIG. 2 can be changed by the impedance value in the input matching circuit 17. For example, when the impedance of the external inductor element 18 is increased, the noise figure becomes minimum. The position moves to a frequency f01 lower than f0, and conversely, if the impedance is reduced, the minimum position moves to a higher frequency f02. Therefore, by changing the impedance value of the external inductor element 18 as needed, a low noise figure in a target frequency band can be easily obtained.

[0018]

As described above, according to the present invention,
In an input matching circuit of a low noise amplifier made into a microwave monolithic IC, a parallel inductor whose one end is connected to a high-frequency ground is used as an external inductor component.
Since it is located outside the chip, the parasitic resistance component of the parallel inductor can be reduced without significantly hindering the use of a monolithic IC. This greatly improves the noise figure characteristics compared to the case of using a spiral inductor. This has the effect of being achieved.

Further, by using an external inductor element, there is an advantage that it can be easily replaced with another inductor element having a different impedance value, and it is possible to easily cope with a change in a target frequency band.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a microwave monolithic IC-based low noise amplifier according to an example of an embodiment of the present invention.

FIG. 2 is a graph showing frequency characteristics of noise figure of the low noise amplifier of FIG. 1 in comparison with the amplifier and the like of FIG. 3;

FIG. 3 is a circuit diagram showing an example of a conventional microwave monolithic IC low noise amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... FET, 4 ... Input terminal, 5,17 ... Input matching circuit, 7,11 ... Series spiral inductor, 8,14 ... Parallel spiral inductor, 9 ... Output terminal, 10 ... Output matching circuit, 16 ... Integrated circuit, 18 ... External inductor element.

Claims (1)

[Claims] 1. A low-noise amplifier comprising a microwave monolithic IC including an input matching circuit and an amplifying transistor, wherein the input matching circuit includes a parallel inductor having one end connected to a high-frequency ground, and an external inductor. A low-noise amplifier having a microwave monolithic IC, wherein the low-noise amplifier is arranged as a component outside the microwave monolithic IC chip.