JPH10335954A - Wide-band feedback amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct phase deviations, even in a millimeter wave band and to form a feedback configuration in a wide band by providing a phase shifter of 180 deg. wide-band, which unites micro-strip lines and a slot line. SOLUTION: A micro-strip slot line converting part is formed by combining a slot line 8 which has a slot line release plane 5 and micro-strip lines 6 and 7 and is operated as a phase shifter that has 180 deg. phase characteristic of a wide band. A signal is inputted from a signal input end 2 of a micro-strip line 2' to an amplifier, amplified by an amplification element 1 and after that, is outputted to an output terminal. Although passing phase of the element 1 is close to 180 deg. in a millimeter wave band, the feedback amount of a part of it is adjusted with a resistance 11 for feedback amount decision, the phase is further shifted by 180 deg. by the phase shifter and it is feedbacked to the end 2. Then, it is possible to perform negative fedback amplification of a wide band even in a millimeter wave band, and a distortion characteristic and the stability of an operation in the millimeter wave band are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedback amplifier, and more particularly to a feedback amplifier in a high frequency band such as a millimeter wave band in which a signal passing through an amplification element has a value in the vicinity of 90 to 0 °. About.

[0002]

2. Description of the Related Art Conventionally, in a high-frequency band such as a millimeter wave, when an attempt is made to construct a negative feedback amplifier, for example, in the case of a common source type amplifier, a satisfactory open loop gain cannot be obtained. Had not been realized.

However, in recent years, communication with a large amount of information such as multimedia has been demanded, and communication in the millimeter wave band, which can provide a wide bandwidth, has been required.

Accordingly, device characteristics have been improved,
Ones with a maximum oscillation frequency of 200 GHz, HEMT
(High Electron Mobolity Transistor), HBT
Devices having high S21 (scattering parameter) such as (Heterojunction Bipolar Transistor) have become available.

[0005] When such a device is realized, a broadband circuit has been required.

A negative feedback amplifier is considered as an application of a circuit at a low frequency.

However, as can be seen from the characteristics shown in FIG.
Broadband feedback amplifiers have been put into practical use in the millimeter wave band due to the fact that the passing phase shifts greatly compared to 180 ° at low frequencies, and the circuit that constitutes the feedback circuit has a longer electrical length of the connecting line. It has not been. In addition, FIG.
It is a figure which shows the magnitude | size (absolute value) (passing gain) of S21 (scattering parameter) of HEMT, and an example of the frequency characteristic of a phase.

FIG. 3 shows a conceptual diagram of the simplest negative feedback amplifier constructed when the passing phase of the device is approximately 180 degrees at a relatively low frequency. Amplifying element (F
ET) The resistance element 11 is connected from the drain electrode of 1 to the gate electrode.
Are connected to form a negative feedback loop, and a part of the signal output from the drain is returned to the gate electrode in the opposite phase. Note that, in FIG. 3, a DC power supply unit and the like are omitted.

[0009]

If a millimeter-wave band feedback amplifier is formed with this conventional circuit, positive feedback is applied and the circuit oscillates or becomes unstable.

As another conventional technique of a feedback amplifier in a microwave band, there is a configuration method proposed in, for example, Japanese Patent Application Laid-Open No. 6-216670. In the configuration proposed in the above publication, a directional coupler operating at the frequency of the second harmonic is provided in the feedback path, and only the second harmonic is fed back to cancel the generated harmonic.

FIG. 4 is a circuit diagram for explaining the principle of the high-output amplifier proposed in the above-mentioned Japanese Patent Application Laid-Open No. 6-216670. Referring to FIG. 4, in a high power amplifier including a signal amplification transistor 22 in a signal line strip line 21, an output side of the transistor 22 is connected to the strip line 21 and a strip on an input side of the transistor 22. A feedback strip line 24 is connected to the line 21 via a directional coupler 23 and has a line length long enough to suppress harmonics. In FIG. 4, 25 is a stub, 26a, 2
6b is a feedback amount changing resistor; 29 is a level detection circuit;
1 denotes a gate bias circuit, and 32 denotes a terminating resistor.

However, this configuration has an advantage that the efficiency of the fundamental wave does not decrease. However, since a stub, a filter, or the like having frequency characteristics is used in the feedback circuit, the usable frequency is determined by those characteristics. There is a problem that it becomes.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a device in which a passing phase of an amplifying element greatly deviates from 180 ° in a millimeter wave band, for example, a phase of about 90 to 0 °. However, an object of the present invention is to provide an amplifier capable of forming a wideband negative feedback amplifier.

[0014]

According to the present invention, there is provided an amplifier for grounding a source electrode of a field effect transistor, inputting a signal from a gate electrode, and outputting a signal from a drain electrode. And a feedback circuit for extracting a part of the data and returning it to the gate electrode.

In the present invention, it is preferable that the feedback circuit is constituted by two sets of microstrip lines, a slot line converter, and the converters connected by a slot line. .

Further, in the present invention, preferably,
The microstrip line, the slot line converter, and the slot line connecting the two converters are provided on a semiconductor substrate.

[0017]

Embodiments of the present invention will be described below. The amplifier of the present invention, in a preferred embodiment thereof, has an amplifying element formed on a semiconductor substrate and a microstrip line and a slot line formed by multilayer wiring as a feedback path, and has a wide band of 180 degrees. It includes a phaser.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an amplifier according to an embodiment of the present invention. FIG. 1A is a plan view, and FIG.
FIG. 2 is a sectional view taken along line AA ′ of FIG.

Referring to FIG. 1, reference numeral 1 denotes a field effect transistor (hereinafter referred to as "FET") having a source electrode grounded, and an amplifying element such as a HEMT.
T1 is a signal input terminal, 2 'is a microstrip line connected to the signal input terminal 2, and 3 is an FET such as a drain electrode.
A signal output terminal 3 'is a microstrip line connected to the signal output terminal 3. 4 is a ground plane, 5 is a slot line release plane, and 6 and 7 are microstrips.
Microstrip line constituting a slot line conversion part, 8 is a slot line, 9 is a via hole, 10
Is a through hole and 11 is a feedback amount determining resistor. These are formed on the same semiconductor substrate 14 such as a GaAs substrate. Although a line for DC power supply is actually required, it is omitted in the figure.

The back surface of the semiconductor substrate 14 is metallized, and the microstrip lines 2 'and 3' are formed as microstrip lines using the semiconductor substrate 14 as a dielectric and the back metal 13 as a ground plane. .

The ground plane 4 is a conductor plane provided on the surface of the semiconductor substrate 14, and the back plane metal 13 is formed in the via hole 9.
Is connected to

The microstrip lines 6 and 7 constituting the microstrip-slotline conversion portion are:
Each is configured below the ground plane 4 with an insulating layer interposed therebetween.

The microstrip lines 6, 7 are:
Although it has a triplate structure sandwiched between the back metal 13 as well, the distance from the conductor surface 4 is shorter, and the conductor surface 4 operates as a microstrip line viewed as a ground plane.

Microstrip lines 2 and 6, 3 and 7
Are connected to each other by a through hole 10.

The feedback amount determining resistor 11 is connected to the semiconductor substrate 14
Above is formed by a monolithic integration process.

Incidentally, the fact that a favorable 180 ° phase shifter can be constructed by combining a microstrip line and a slot line is described in, for example, a document (KC GUPATA).
Author, "MICROSTRIP LINES AND S
LOTLINES ", ARTECH, 1979, p. 250).

This phase shifter does not operate from the DC region due to its structure, but has an operation lower limit frequency.

Therefore, in FIG. 1, the phase is converted by 180 degrees by the microstrip composed of 5, 6, 7 and 8 and the slot line conversion. This characteristic has a broad-band 180 degree phase characteristic.

An actual signal is input from the microstrip line 2 ′ and the signal input terminal 2 to the amplifying element 1, amplified, and then output to the signal output terminal 3.

In a millimeter wave band or the like, the passing phase of the amplifying element 1 is close to 180 degrees as shown in FIG. One part of the microstrip line 7 passes through the feedback amount determining resistor 11, and the microstrip line 7, the slot line 8, and the microstrip line 6
Then, the phase is further shifted by 180 degrees and fed back to 2.

Since there is a phase shift due to the line length of the slot line 8, it is necessary to select the slot line 8 to have a negligible length. However, since the wavelength shortening rate of the slot line 8 is larger than that of the microstrip (the equivalent wavelength is longer at the same frequency), even in the millimeter wave band, the degree of freedom is smaller than that of the microstrip line (the phase shift is small).

Therefore, even in the millimeter wave band, a wideband negative feedback amplifier can be formed, the distortion characteristics such as the reduction of the cross modulation characteristics can be improved, and the operation stability in the millimeter wave band can be improved.

In the low band, the internal passing phase 18 of the amplifying element 1
Positive feedback may occur at 180 degrees of the microstrip-slot conversion portion in addition to 0 degrees. However, since the microstrip-slot conversion has a low cutoff frequency, this frequency is reduced to a frequency at which positive feedback can be ignored. With the above setting, positive feedback in a low frequency range can be prevented. This low cutoff frequency is generally determined by the size of the slot line release surface 5.

The amount of negative feedback is determined by the amount of coupling between the microstrip lines 6 and 7 and the slot line 8 or the resistance formed on the semiconductor substrate.

As shown in FIG. 1, when an open stub of a microstrip line in a slot line-microstrip line conversion portion is used, the signal input terminal 2 and the signal output terminal 3 are separated from each other in a DC manner. Therefore, the feedback circuit does not require a capacitor 16 (see FIG. 3) for DC separation, such as an MIM (metal-insulating film-metal) configuration, and has an advantage that the configuration is simplified.

In order to finely adjust the phase of the signal that is negatively fed back, a phase shift circuit may be inserted in the negative feedback path. It is clear that an HBT (hetero bipolar transistor) or the like can provide the same or better effect as an amplifying element to be used in addition to the field effect transistor and the HEMT.

[0037]

As described above, according to the present invention,
Since a wide-band 180-degree phase shifter can be configured, there is an effect that a wide-band negative feedback amplifier can be realized in a millimeter wave band. In particular, in an HBT or the like, S21 is larger than a HEMT or the like, and the effect is particularly remarkable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention;
(A) is a plan view, and (b) is a cross-sectional view taken along line AA 'of (a).

FIG. 2 is a diagram illustrating an example of the magnitude (absolute value) of S21 (scattering parameter) and phase characteristics of the HEMT.

FIG. 3 is a conceptual diagram of a negative feedback amplifier used in a low frequency band.

FIG. 4 is a diagram for explaining a circuit of a high-power amplifier described in Japanese Patent Application Laid-Open No. 6-216670.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 amplifying element 2 signal input 3 signal output 4 slot line ground plane 5 slot line release plane 6, 7 strip line, microstrip line of slot line conversion unit 8 slot line 9 via hole 10 through hole 11 feedback amount determining resistor 12 Interlayer insulating film 13 Back conductor 14 Semiconductor substrate 16 DC blocking capacitor 17 Ground 21 Signal line strip line 22 Signal amplification transistor (FET) 23 Directional coupler 24 Feedback strip line 25 Stub 26a, 26b Feedback amount changing resistor 29 Level detection circuit 31 Harmonic suppression control circuit (Harmonic suppression control means) 32 Termination resistor

Claims (5)

[Claims] An amplifier for grounding a source electrode of a field effect transistor, inputting a signal from a gate electrode, and outputting a signal from a drain electrode, comprising: a feedback circuit for extracting a part of an output signal from the drain electrode and returning it to the gate electrode. A feedback amplifier characterized in that: 2. The feedback circuit according to claim 1, wherein said feedback circuit comprises two sets of microstrip line-slot line converters and these two converters are connected by a slot line. A feedback amplifier as described. 3. The feedback amplifier according to claim 2, wherein said microstrip line-slot line converter and a slot line connecting said two converters are provided on a semiconductor substrate. 4. A feedback amplifier comprising a 180.degree. Phase shifter using a microstrip line-slot line converter on a semiconductor substrate in a feedback circuit of an amplifying element in an MMIC in a millimeter wave band or the like. . 5. The microstrip line on the input side and the output side of the amplifying element and each microstrip line forming the microstrip line-slot line converter are connected by a through hole. Each microstrip line constituting the slot line converter is formed on the front surface of the semiconductor substrate, and is connected to a metal on the back surface of the semiconductor substrate via a via hole via an insulating film thereon, and a conductor surface having a slot line. 5. The feedback amplifier according to claim 4, further comprising a resistor for adjusting a feedback amount and a phase adjusting circuit in a feedback path as required.