JPS5846569Y2 - Ultra high frequency transistor amplifier circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an impedance matching circuit structure for an amplifier in microwave and sub-millimeter wave bands using ultra-high frequency transistors.

In ultra-high frequency transistor amplifiers, especially crystallized quadratic amplifiers, (1) In addition to the small impedance resistance of the transistor, the reactance is also small, and as the frequency increases, the property changes from capacitive to inductive. 2) The higher the output, the larger the size of the transistor chip, and in the ultra-high frequency band the strip line wavelength of the matching circuit becomes shorter.As a result, the size of the transistor chip becomes equal to the strip line wavelength. This makes it difficult to excite the entire high-output transistor chip in the same electromagnetic phase, and as a result, the higher the output and the higher the frequency, the more difficult it becomes to realize a matching circuit.

FIG. 1 shows an example of the input and output chipedance locus with respect to frequency of a microwave high output GaA, S field effect transistor (hereinafter referred to as FET) on a Smith diagram.

FIG. 2 shows a conventional example of an input/output matching circuit for an amplifier in the C band (4 to 8 GHz) using a high output FET having such an impedance.

In the figure, a gate terminal 3 constituting an input terminal of an FET 2 brazed to a ground conductor 1 is connected to two lumped constant capacitors 6 formed on a high dielectric constant substrate 5 through a thin punching conductor wire 4. Furthermore, the lumped constant capacitor 6 is connected by a bonding conductor thin wire 7 to a microstrip line 9 having a characteristic impedance of 50Q formed on an alumina substrate 8.

On the other hand, the output matching circuit of the high output FET 2 is connected to the high output FET 2.
A transmission line 13 for phase shifting formed on an alumina substrate 12 is connected to a drain terminal 10 constituting the output terminal of the ET 2 by a thin bonding conductor wire 11, and a large capacitance for canceling the parallel reactance. The transmission line 14 constitutes a parallel stub.

The design of the input matching circuit begins with the punching conductor thin wire 4.
By adding an inductive component, the impedance of the FET is converted to approximately a normalized conductance of 1, and furthermore, the inductive reactance component is canceled by the parallel lumped capacitor 6 to achieve impedance matching.

Similarly, the design of the output circuit is such that the impedance of the FET is approximately converted to a normalized conductance of 1 using the bonding conductor thin wire 11 and the transmission line 13 for phase shifting, and the inductive reactance is canceled out using the capacitive parallel stub 14. can be decided.

In this example, a distributed constant line is not used as the input matching circuit, and two lumped constant capacitors 6 are arranged symmetrically to achieve input matching and to prevent the entire high-power FET 2, which has a large chip size, from electromagnetic waves. It is designed to excite in the same phase.

As the frequency increases, the reactance of the FET becomes inductive, as can be seen from the locus of the human input impedance of the high output FET with respect to frequency in Figure 1, and in the case of Figure 1, the normalized conductance is It becomes smaller than 1.

Therefore, in order to achieve input matching using the matching circuit shown in FIG. 2 in the high frequency range, after canceling the inductive reactance with the lumped constant capacitor 6 (the impedance at this time is only the resistance bone), (The value is larger than 1) It is necessary to convert the impedance to 1 using a half-wavelength impedance conversion circuit instead of the characteristic impedance 50Ω transmission line 9. In this case, in addition to the disadvantage that the frequency band characteristics become narrow, A drawback arises in that the characteristic impedance of the wavelength impedance conversion circuit becomes too high, the strip conductor width becomes narrow, and power loss increases.

On the other hand, regarding the output side matching circuit using the distributed constant line shown in Figure 2, since the frequency is high, the microstrip line wavelength is shortened, and as a result, in order to improve the design of the matching circuit, the transmission line As the length of the transmission line in the propagation direction is scaled down, it is necessary to scale down the width of the transmission line.

As a result, in order to keep the characteristic impedance of the transmission line constant, it is necessary to use a MIC substrate (an alumina substrate in the example in Figure 2).
must be made thinner.

Furthermore, matching with high-impedance transistors such as high-output FETs requires a low-impedance transmission line, so in order to keep the circuit compact, MIC
Making the substrate thinner is advantageous in terms of design.

However, like the MIC board of the output matching circuit, if the MIC board of the input side is made thinner, as mentioned above, the strip conductor width of the half-wavelength impedance conversion circuit on the input side becomes thinner and thinner, which not only increases power loss, but also increases the power loss. Due to side etching when realizing a thin strip line in manufacturing, a drawback arises in that variations in transmission line characteristics become large.

This problem becomes more serious as the frequency becomes higher.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultra-high frequency I transistor amplifier circuit equipped with an impedance matching circuit of a new structure that eliminates the above-mentioned drawbacks.

According to the present invention, in an MIC ultra-high frequency transistor amplifier in which a manual matching circuit is configured by a lumped capacitor and a half-wavelength impedance conversion circuit, the substrate thickness is thicker than the microstrip line substrate thickness constituting the output matching circuit. I) A super high frequency transistor amplifier circuit is obtained, characterized in that the + wavelength impedance conversion circuit is formed on a tube line substrate.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 3 is a schematic circuit diagram for explaining a quasi-millimeter-wave band high-power GaAs field-effect transistor amplifier, which is an embodiment of the ultra-high frequency transistor amplifier circuit of the present invention.
High power GaAs brazed to ground conductor 1 in the figure.
A gate terminal 3 constituting the input terminal of the FET 2 is connected to two lumped constant capacitors 6 formed on a high dielectric constant substrate 5 by a punching conductor thin wire 4, and the lumped constant capacitor 6 is connected to a bonding conductor thin wire 4. 7
It is connected to a high impedance microstrip line 16 forming a half-wavelength impedance conversion circuit formed on an alumina substrate 15 having a thickness of 0.635 mm.

On the other hand, the output matching circuit of the high-power GaAs FET 2 is formed on an alumina substrate 17 with a thickness of 0.26 mm, which is connected to the drain terminal 10 of the high-power FET 2 by a bonding conductor wire 11. Transmission line 1
3. and a transmission line 14 that constitutes a capacitive parallel stub for canceling the parallel reactance.

In this embodiment, the wavelength impedance conversion circuit (based on the high impedance line of the input matching circuit) is formed on a thick alumina substrate, so that the high impedance transmission line 16 can be realized with a wide strip conductor width. Power loss can be kept small.

In the embodiment of the present invention, a high-output GaAs field effect transistor amplifier was explained, but the transistor is not limited to a field effect transistor, but may also be a bipolar transistor, and a field effect transistor may also be used.
The material is not limited to aAs, but may be made of InP, Si, or the like.

Furthermore, the output matching circuit is not limited to one using capacitive parallel stubs, and the configuration of the output matching circuit is not limited to a specific one.

Further, the strip line is not limited to one constructed on an alumina substrate, but may be formed of other circuit board materials.

[Brief explanation of the drawing]

Figure 1 is a Smith diagram showing an example of the input/output impedance locus versus frequency of a microwave high output GaAs field effect transistor; Figure 2 is a schematic diagram of a conventional type microwave high output GaAs field effect I transistor amplifier circuit; FIG. 3 is a schematic diagram of a quasi-millimeter wave band high output GaAs field effect transistor amplifier circuit, which is an embodiment of the present invention. In the figure, 1 is a ground conductor, 2 is a high-power GaAs field effect transistor, 3 is a gate terminal of the field effect transistor 2, 4, 7, 11 . 5 is a bonding conductor thin wire, 5 is a high dielectric constant substrate, 6 is a lumped constant capacitor, 8.12 is an alumina substrate, 9 is a microstrip line with a characteristic impedance of 50β, and 10 is the field effect transistor 2.
13 is a transmission line for phase shifting, 14 is a transmission line for configuring a capacitive parallel stub, and 15 is a 0.5mm thick transmission line.
A 635 mm alumina substrate, 16 a microstrip line forming a wavelength impedance conversion circuit, and 17 an alumina substrate with a thickness Q, 2f) 111-m.

Claims (1)

[Scope of utility model registration request] MIC whose input matching circuit is composed of a lumped capacitor and a quarter-wavelength impedance conversion circuit.
In the ultra-high frequency transistor amplifier, the wavelength impedance conversion circuit is formed on a microstrip line substrate that is thicker than the microstrip line substrate that constitutes the output matching circuit. High frequency transistor amplifier circuit.