JP2001267864A - Multiband high frequency amplification circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a multiband high frequency amplification circuit. SOLUTION: In a multiband high frequency amplification circuit provided with an amplification part 30 having plural active elements, an input matching circuit 10 and an output matching circuit 20, the operation point of at least one of plural active elements of the amplification part 30 can be changed and the matching frequencies of the input matching circuit 10 and the output matching circuit 20 are decided in accordance with the combination of the operation points of the active elements. In the multiband high frequency amplification circuit, the high frequency amplification circuit of plural frequency bands can be miniaturized and the bias of the amplification part 30 is changed. Thus, a desired frequency band operation is realized and the frequency band can be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-band high-frequency amplifier circuit for amplifying a high-frequency signal of, for example, 1 GHz or more.

[0002]

2. Description of the Related Art Recently, a single wireless device (operating in a plurality of frequency bands) corresponding to a service using multi-frequency wireless communication has been developed.

FIG. 12 shows one amplifier circuit for a plurality of frequency bands.
This is an example of a conventional multi-band high-frequency amplifier integrated on a chip. 1999 IEEE MIT-S International Microwav
It was announced at e Symposium.

In this configuration, an input terminal 1 for inputting a signal is provided.
A, an output terminal 2A for outputting a signal, an amplifier 30A having an active element for amplifying a signal, an input terminal 1A and an amplifier 30
An input matching circuit 10A for matching the impedance of A, an output terminal 2A and an output matching circuit 20A for matching the impedance of the amplifier 30A constitute a first amplifier circuit, an input terminal 1B for inputting a signal, and output of a signal. Output terminal 2B, amplifying section 30 having an active element for amplifying a signal
B, an input matching circuit 10B that performs impedance matching between the input terminal 1B and the amplifier 30B, and an output terminal 2B and the amplifier 30
An output matching circuit 20B that performs impedance matching of B constitutes a second amplifier circuit.

[0005] Then, these two amplifier circuits are simply synthesized on the same chip so as to operate in different frequency bands, and further, a bias control circuit 40A for the amplifier 30A,
A bias control circuit 40B for the amplifier 30B and a bias switch 50 for selecting one of the bias control circuits 40A and 40B are also synthesized on the same chip. 3 is a bias switch terminal, and 4A and 4B are bias control terminals. With this configuration,
By selectively operating the two amplifier circuits, a gain in a desired frequency band can be obtained.

FIG. 13 shows a conventional multi-band high-frequency amplifier circuit having a gain covering a plurality of frequency bands.
FIG. 2 is a diagram illustrating a negative feedback amplifier as one example. This includes an input terminal 1, an output terminal 2, an amplifier 30 'having an active element for amplifying a signal, an input matching circuit 10 for impedance matching between the input terminal 1 and the amplifier 30', and an output terminal 2 and an amplifier 30 '. Output matching circuit 20, which performs impedance matching of
And a feedback circuit 60.
This configuration is characterized in that the gain is reduced but the bandwidth is expanded, as shown in Chapter 3 of the Monolithic Microwave Integrated Circuit (published in 1997) by the Institute of Electronics, Information and Communication Engineers.

FIG. 14 is a diagram showing the frequency characteristics of the gain of the above two multi-band high-frequency amplifier circuits. The solid line shows the frequency characteristics of the high-frequency amplifier circuit shown in FIG. 12, and the broken line shows FIG. It is a frequency characteristic of a high frequency amplifier circuit. When the desired frequency is f ₁ and f _2, it is possible to obtain a gain at a desired frequency band by performing the changes and the bias control of the human output terminal in the amplifier circuit configuration of Figure 12. On the other hand, in the amplifier circuit having the configuration of FIG. 13, gain can be obtained in a wide band including a desired frequency.

[0008]

However, FIG.
In the example of the high-frequency amplifier circuit having the configuration described above, an input / output matching circuit, an amplifier, a bias control circuit, and the like corresponding to each frequency are required, and the chip area of the circuit becomes large even when integrated on one chip. there were. Further, there is a human output terminal adapted to each frequency, and there is a problem that connection to the outside becomes complicated.

Further, in the example of the high-frequency amplifier circuit having the configuration shown in FIG. 13, there is a problem that the level of the unnecessary wave becomes high because the high-frequency amplifier circuit has a gain outside the desired frequency band. Further, it is necessary to connect a filter circuit in order to suppress the unnecessary wave, and there is a problem that the size of the device itself is increased.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to realize a high-frequency amplifier circuit capable of changing an operating frequency band to solve the above-mentioned problems.

[0011]

According to a first aspect of the present invention, there is provided an amplifying section having a plurality of active elements, an input matching circuit provided between the amplifying section and a signal input terminal; In a multi-band high-frequency amplifier circuit including an output matching circuit provided between the active element and a signal output terminal, an operating point of at least one of the plurality of active elements can be changed, and a combination of operating points of the respective active elements is provided. , The matching frequencies of the input matching circuit and the output matching circuit are determined.

In a second aspect based on the first aspect, the plurality of active elements have the same size.

[0013] In a third aspect based on the first aspect, at least one of the plurality of active elements is different in size from other active elements.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Principle of the Present Invention] FIG. 1 is a diagram showing the principle configuration of a multi-band high-frequency amplifier circuit according to the present invention. This circuit includes an input terminal 1 for inputting a signal, an output terminal 2 for outputting a signal, and a plurality of FETs as active elements for amplifying the signal.
, 3i, an input matching circuit 10 for performing impedance matching between the input terminal 1 and the amplifying unit 30, and an output matching circuit 20 for performing impedance matching between the output terminal 2 and the amplifying unit 30. Have been.

Signals input to the high frequency amplifier circuit are a _in , a _out ,
A signal emanating from the high frequency amplifying circuit and b _in, b _out, a signal input to the input matching circuit _{10 a fin_1, a fin_2, ···} , a
_{fin_i} , signals output from the input matching circuit 10 are b _{fin_1} , b
_{, fin_2} ,..., b _{fin_i} , signals entering the output matching circuit 20 are a _{fout_1} , a _{fout_2} ,..., a _{fout_i} , and signals leaving the output matching circuit 20 are b _{fout_1} , b _{fout_2,.}
b _{fout_i} .

Assuming that the scattering matrices of the input matching circuit 10, the amplifying unit 30, and the output matching circuit 20 are Sin, Samp, and Sout, the input / output signals of the high-frequency amplifier circuit are obtained by the following relational expressions. Here, ω is a frequency.

[0017]

On the other hand, the amplifying unit 30 can be expressed as follows by using the scattering matrix of the FETs 31, 32,... The scattering matrix of the FET is Then, the scattering matrix of the amplifier 30 is as follows.

[0019]

This scattering matrix changes depending on the bias condition of the active element FET. From equations (1) to (3), the amplification unit 30
It can be understood that if the value of the scattering matrix Samp changes, the scattering matrices Sin and Sout of the input matching circuit 10 and the output matching circuit 20 change uniquely. That is, the boundary condition (load impedance) between the input matching circuit 10 and the output matching circuit 20 can be changed by changing the bias point (operating point) of the active element of the amplifying unit 30.
The matching frequency can be changed without changing the configuration of the 0 and the output matching circuit 20.

The scattering matrix S indicating the characteristics of the entire high-frequency amplifier circuit is expressed by the following relational expressions from equations (1) to (3) and (5).

Therefore, the frequencies ω1, ω2,.
, The bias condition of the amplifying unit 30 corresponding to the operating frequency is set, and for all the frequencies ω1, ω2,.
(Ωn), Sin (ωn), Sout (ω
By obtaining n), the multi-band compatible high-frequency amplifier circuit of the present invention can be realized.

[First Embodiment] FIG. 2 shows a configuration of a multi-band high-frequency amplifier circuit according to a first embodiment of the present invention. The high-frequency amplifier circuit according to the present embodiment includes an input terminal 1 for inputting a signal, an output terminal 2 for outputting a signal, an amplifier 30 having an active element for amplifying a signal, an input terminal 1 and an amplifier 3
An input matching circuit 10 performs impedance matching of 0, and an output matching circuit 20 performs impedance matching of the output terminal 2 and the amplifier 30. In the high-frequency amplifier circuit of the present embodiment, the amplifier 30 includes two FETs 301 and 302 as active elements.

With the configuration as shown in FIG. 2, when a signal is input from the input terminal 1, the input terminal 1 and the output terminal 2 are connected to the input matching circuit 10 at a desired frequency. Impedance matching with the amplifying unit 30 via the output matching circuit 20 and signal amplification at a desired frequency.

FIGS. 3 and 4 show the dependence of the input / output reflection characteristics (input / output impedance) of the FETs 301 and 302 constituting the amplifying unit 30 on the drain bias and the gate bias, respectively.

FIG. 3 shows the reflection characteristics when the drain bias is changed from 0 V to 2 V when the gate bias of the FETs 301 and 302 is 0 V and the frequency is 20 GHz, and S ₁₁ is the reflection on the gate side of the FET. characteristic (input impedance), S ₂₂ is a reflection characteristic of the drain side (output impedance). As shown in FIG. 3, by changing the drain bias, the reflection characteristics S ₁₁ and S ₂₂ (input / output impedance) of the FET can be largely changed. Especially in this case, the change in S ₂₂ is large.

FIG. 4 shows reflection characteristics when the gate bias is changed from -0.7 V to 0.2 V when the drain bias of the FETs 301 and 302 is 2 V and the frequency is 20 GHz. As shown in FIG. 4, by changing the gate bias, the reflection characteristics S ₁₁ and S ₂₂ of the FET are changed.
(Input / output impedance) can be greatly changed. Especially in this case, a large change in S _11.

As described above, the FE constituting the amplifying unit 30
The input and output impedances of T301 and 302 can be greatly changed by changing the bias point (operating point). F
By changing the bias point of ET, the matching frequency can be changed to a desired frequency. To change the bias point,
For example, a plurality of bias circuits may be configured in advance for each FET, and a specific bias circuit may be selected by an external control signal (not shown).

FIG. 5 shows a bias operation mode of the FETs 301 and 302 of the amplifier 30 of the high frequency amplifier circuit shown in FIG. ON is a gate bias of 0 V, OFF is a gate bias of −0.7 V, and each drain bias is 2 V.
V. In the present embodiment, F
Since two ETs are used, in the case of the above-mentioned bias condition, the case where the FETs are turned on one by one and the case where the two
When N is set, three operation modes 1, 2, and 3 can be realized.

In the input matching circuit 10 and the output matching circuit 20 of the high-frequency amplifier circuit of this embodiment, the operating frequencies of the high-frequency amplifier circuit are f ₁ and f in the three operation modes 1, 2, and 3, respectively. It is designed to be a _2, f _3. FIG. 6 shows characteristics of the high-frequency amplifier circuit in each operation mode. In the figure, S _{21 and} S ₁₁ are respectively shown.
_, Shows the S _22. Incidentally, S ₂₁ is the insertion loss. Looking at these S _21, S _{11, and} S ₂₂ , the operating frequency of the high-frequency amplifier circuit is adjusted in accordance with the operation modes 1, 2, and 3 shown in FIG.
f _1, it is seen that changing the f _2, f _3.

As described above, by changing the bias point (operating point) of the FET of the amplifying unit 30, the high-frequency amplifier circuit of the present embodiment can perform an amplifying operation corresponding to a multi-band.

In this embodiment, the combination of the gate bias of the FET at 0 V and -0.7 V has been described. However, other combinations of bias points may be used. Furthermore, a combination in which the drain bias is changed may be used. The configuration of the active element of the amplifier 30 may be a cascode-connected or Darlington-connected FET.

[Second Embodiment] FIG. 7 shows a configuration of a second embodiment of the present invention. The basic configuration of the high-frequency amplifier circuit according to the present embodiment is the same as that shown in FIG. 2, but here, the amplifying section 30 has three Fs as active elements.
ET 301, 302, 303.

With the configuration shown in FIG. 7, when a signal is input from the input terminal 1, the input terminal 1
And the output terminal 2 are impedance-matched with the amplifying unit 30 via the input matching circuit 10 and the output matching circuit 20, respectively.
Signal amplification can be performed at a desired frequency.

In this embodiment, the number of FETs in the amplifier 30 is three.
As shown in FIG. 8, seven operation modes 1 are provided by increasing the number of FETs to three.
To 7 can be realized.

Here, ON indicates a drain bias of 2 V and a gate bias of 0 V, and OFF indicates a drain bias of 2 V and a gate bias of -0.7 V. That is, only one FET is turned on, and the other two are turned off.
Three modes, two FETs are turned on,
It is possible to realize a total of seven modes including three modes in which the remaining one is OFF and one mode in which all three FETs are ON.

The input matching circuit 10 and the output matching circuit 10 of the high-frequency amplifier circuit of the present embodiment match the operating frequencies of the amplifier circuits to seven different frequencies in accordance with the bias conditions of the seven operating modes described above. Designed to

As described above, also in the high-frequency amplifier circuit of the present embodiment, the amplification operation corresponding to the multi-band can be performed by changing the bias point of the FET of the amplification section 30, and the high-frequency amplification circuit shown in FIG. The number of frequencies can be larger than in the case of a circuit.

Although the present embodiment has shown a combination in which the gate bias of the FET is set to 0 V and -0.7 V, other combinations of bias points may be used.
Furthermore, a combination in which the drain bias is changed may be used. The configuration of the active element of the amplification unit 30 is as follows.
A cascode-connected or Darlington-connected FET may be used.

[Third Embodiment] FIG. 9 shows the configuration of a third embodiment of the present invention. The high-frequency amplifier circuit of the present embodiment is basically the same as the high-frequency amplifier circuit shown in FIG. 7, but the amplifying unit 30 is configured using three FETs 311, 312, and 313 having different gate widths as active elements. Have been.

With the configuration shown in FIG. 9, when a signal is input from the input terminal 1, the input terminal 1
And the output terminal 2 are impedance-matched with the amplifying unit 30 via the input matching circuit 10 and the output matching circuit 20, respectively.
Signal amplification can be performed at a desired frequency.

In this embodiment, the FETs 311,
It is characterized in that the sizes of the FETs 312 and 313 are not the same, and thus, by changing the sizes of the FETs, the change range of the input / output impedance when the bias of the FETs is variable can be further increased. FIG.
0, FIG. 11 shows the gate width of the FET (from 50 μm to 400 μm).
Input reflection characteristics S ₁₁ (input impedance) and output reflection characteristics S ₂₂ (output impedance) that can be taken by the FET when both the bias point and the bias point are changed.
Is shown.

As shown in these figures, by changing the gate width in addition to the change of the bias point, the input reflection characteristic S of the FET is compared with the case of FIGS.
₁₁ (input impedance) and output reflection characteristics S ₂₂ (output impedance) can be set in a wide range.

Therefore, the high-frequency amplifier circuit according to the present embodiment can expand the boundary condition range (set range of the load impedance) between the input matching circuit 10 and the output matching circuit 20, thereby facilitating the multi-band input / output matching circuit. And the degree of freedom in setting the operating frequency can be increased.

In this embodiment, the number of FETs in the amplifying section 30 of the high-frequency amplifier circuit is three. However, if the number is increased to four or five, the frequency band to which this amplifier circuit can be applied increases as the number increases. Further, by changing the number of types of the gate width of the FET, the degree of freedom in setting the operating frequency can be further expanded. Further, the configuration of the active element of the amplifying unit may be a cascode-connected or Darlington-connected FET.

[0046]

As described above, in the high frequency amplifier circuit of the present invention, a multi-band compatible high frequency amplifier circuit can be realized in a small size, and a desired frequency band operation can be realized by changing the bias of the amplifier. There is an advantage that the frequency band can be changed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for explaining the principle of a multi-band high-frequency amplifier circuit according to the present invention.

FIG. 2 is a circuit diagram of the multi-band high-frequency amplifier circuit according to the first embodiment of the present invention.

FIG. 3 is an input / output reflection characteristic diagram showing the drain voltage dependence of the circuit of FIG. 2;

FIG. 4 is an input / output reflection characteristic diagram showing gate voltage dependence of the circuit of FIG. 2;

FIG. 5 is an explanatory diagram of an operation mode of the circuit of FIG. 2;

FIG. 6 shows S _21, S _{11, and} S _{11 in} each operation mode of the circuit of FIG.
It is a frequency characteristic diagram of the S _22.

FIG. 7 is a circuit diagram of a multi-band high-frequency amplifier circuit according to a second embodiment of the present invention.

8 is an explanatory diagram of an operation mode of the circuit in FIG.

FIG. 9 is a circuit diagram of a multi-band high-frequency amplifier circuit according to a third embodiment of the present invention.

FIG. 10 is an input / output reflection characteristic diagram showing the drain voltage dependency when the gate width of the circuit of FIG. 9 is changed.

11 is an input / output reflection characteristic diagram showing gate voltage dependence when the gate width of the circuit of FIG. 9 is changed. .

FIG. 12 is a circuit diagram of a conventional multi-band high-frequency amplifier circuit.

FIG. 13 is a circuit diagram of another conventional multiband high-frequency amplifier circuit.

FIG. 14 is a frequency characteristic diagram of the gain of a conventional multiband high-frequency amplifier circuit.

[Explanation of symbols]

 1, 1A, 1B: input terminal 2, 2A, 2B: output terminal 3: terminal for bias switch 4A, 4B: bias terminal 10, 10A, 10B: input matching circuit 20, 20A, 20B: output matching circuit 30, 30 ' : Amplifying units 31 to 3i, 301 to 303, 311 to 313: FETs 40A and 40B: Bias control circuit 50: Bias switch 60: Feedback circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J069 AA04 AA21 AA51 CA61 CA62 CA71 CA73 FA10 FA12 FA18 HA09 HA16 KA29 KA48 KA49 MA19 MA22 SA13 TA01 TA03 TA05 5J091 AA04 AA21 AA51 CA61 CA62 CA71 CA73 FA10 FA12 FA29 HA09 KA48 KA48 MA19 MA22 SA13 TA01 TA03 TA05

Claims (3)

[Claims] An amplifying section having a plurality of active elements, an input matching circuit provided between the amplifying section and a signal input terminal, and an output matching circuit provided between the amplifying section and a signal output terminal. In the multiband high-frequency amplifier circuit provided, an operating point of at least one of the plurality of active elements can be changed, and the input matching circuit and the output matching circuit can be changed according to a combination of operating points of the respective active elements. A multi-band high-frequency amplifier circuit, wherein the matching frequency of the multi-band high-frequency amplifier is determined. 2. The multi-band high-frequency amplifier circuit according to claim 1, wherein the plurality of active elements have the same size. 3. The multi-band high-frequency amplifier circuit according to claim 1, wherein at least one of the plurality of active elements has a different size from other active elements.