Patent Description:
In some cases, the radio communication device and the radar device each include a high-frequency amplifier that amplifies a high-frequency signal. The high-frequency amplifier includes, for example, a common-source multi-finger field effect transistor (FET), and the common-source FET amplifies a high-frequency signal.

An output power of the high-frequency amplifier increases with an increase in voltage applied to the drain of the FET. However, since the FET has a withstand voltage, the drain voltage of the FET is limited.

Patent Literature <NUM> below discloses a high-frequency amplifier in which a drain of a common-source FET is connected to a source of a common-gate FET whose gate is grounded via a capacitor.

In the high-frequency amplifier disclosed in Patent Literature <NUM>, a plurality of gate fingers included in the common-gate FET are bundled by a gate bus bar. One end of the capacitor is connected to the gate bus bar, and the other end of the capacitor is grounded.

Patent Literature <NUM> discloses in one embodiment a high-frequency amplifier comprising:.

In a high-frequency amplifier disclosed in Patent Literature <NUM>, if the capacitance value of a capacitor is appropriately set, there is a possibility that a voltage twice as high as that of a high-frequency amplifier including only one common-source FET can be applied to the drain of the common-source FET.

However, in the high-frequency amplifier disclosed in Patent Literature <NUM>, the distances from the respective gate fingers of the common-gate FET to the capacitor are different from each other, and thus parasitic components between the respective gate fingers and common-gate capacitance are different from each other. Since the parasitic components between the respective gate fingers and the common-gate capacitance are different from each other, there is an imbalance between the amplification operations of the respective gate fingers. Since there is an imbalance between the amplification operations of the respective gate fingers, the combined loss of high-frequency signals amplified by the gate fingers increases, so that there is a problem that the output power decreases.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to obtain a high-frequency amplifier capable of suppressing an imbalance between amplification operations of a plurality of gate fingers.

A high-frequency amplifier according to the present disclosure is defined in the appended independent claim.

According to the present disclosure, the high-frequency amplifier is configured in such a way that the capacitors are arranged at respective positions where the impedances obtained by looking toward the capacitors from the respective gate fingers of the common-gate transistor are equal to each other. As a result, the high-frequency amplifier according to the present disclosure can reduce the imbalance between the amplification operations of the gate fingers.

Hereinafter, in order to describe the present disclosure in more detail, modes for carrying out the present disclosure will be described with reference to the accompanying drawings.

<FIG> is a configuration diagram illustrating a radio communication device including a high-frequency amplifier <NUM> according to a first embodiment.

The high-frequency amplifier <NUM> included in the radio communication device illustrated in <FIG> amplifies a high-frequency signal as a signal to be amplified, and outputs the amplified high-frequency signal to a transmission antenna <NUM>.

The transmission antenna <NUM> radiates a radio wave related to the high-frequency signal output from the high-frequency amplifier <NUM> into space.

<FIG> is a configuration diagram illustrating a radar device including the high-frequency amplifier <NUM> according to the first embodiment.

The high-frequency amplifier <NUM> included in the radar device illustrated in <FIG> amplifies a radar signal as a signal to be amplified, and outputs the amplified radar signal to a transmission antenna <NUM>.

The transmission antenna <NUM> radiates a radio wave related to the radar signal output from the high-frequency amplifier <NUM> into space.

<FIG> is a configuration diagram illustrating the high-frequency amplifier <NUM> according to the first embodiment.

<FIG> is an equivalent circuit diagram illustrating the high-frequency amplifier <NUM> according to the first embodiment.

A signal input terminal <NUM> is a terminal to which a high-frequency signal, a radar signal, or a reception signal is applied as a signal to be amplified, from the outside. Here, for the convenience of description, it is assumed that a high-frequency signal is applied to the signal input terminal <NUM>.

In the high-frequency amplifier <NUM> illustrated in <FIG>, although not illustrated, the signal input terminal <NUM> is connected to an input-side matching circuit.

A common-source transistor <NUM> includes a gate electrode 12a, a drain electrode 12b, and a source electrode 12c.

The gate electrode 12a of the common-source transistor <NUM> is connected to the signal input terminal <NUM>.

The drain electrode 12b of the common-source transistor <NUM> is connected to a source electrode 32a of a common-gate transistor <NUM> to be described later.

The source electrode 12c of the common-source transistor <NUM> is connected to the ground.

The common-source transistor <NUM> amplifies a high-frequency signal applied to the gate electrode 12a, and outputs the amplified high-frequency signal from the drain electrode 12b to the source electrode 32a of the common-gate transistor <NUM>.

As the common-source transistor <NUM>, for example, a GaN multi-finger transistor made of gallium nitride (GaN) formed on a monolithic microwave integrated circuit (MMIC) is used.

The gate electrode 12a includes a gate bus bar <NUM> and gate fingers <NUM>-<NUM> to <NUM>-<NUM>.

In the high-frequency amplifier <NUM> illustrated in <FIG>, the gate electrode 12a includes eight gate fingers <NUM>-<NUM> to <NUM>-<NUM>. However, the gate electrode 12a is only required to have a plurality of gate fingers <NUM>, and is not limited to a gate electrode having the eight gate fingers <NUM>-<NUM> to <NUM>-<NUM>.

The gate bus bar <NUM> is connected to the signal input terminal <NUM>.

One end of each of the gate fingers <NUM>-<NUM> to <NUM>-<NUM> is connected to the gate bus bar <NUM>.

The drain electrode 12b includes drain fingers <NUM>-<NUM> to <NUM>-<NUM>.

The drain finger <NUM>-<NUM> is disposed between the gate finger <NUM>-<NUM> and the gate finger <NUM>-<NUM> in parallel with each of the gate fingers <NUM>-<NUM> and <NUM>-<NUM>.

The source electrode 12c includes source fingers <NUM>-<NUM> to <NUM>-<NUM>.

The source finger <NUM>-n (n=<NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) is a source electrode with an individual source via (ISV) structure having a via hole <NUM>-n.

The source finger <NUM>-<NUM> is disposed on the left of the gate finger <NUM>-<NUM> in <FIG> in parallel with the gate finger <NUM>-<NUM>.

The source finger <NUM>-<NUM> is disposed between the gate finger <NUM>-<NUM> and the gate finger <NUM>-<NUM> in parallel with each of the gate fingers <NUM>-<NUM> and <NUM>-<NUM>.

The source finger <NUM>-<NUM> is disposed on the right of the gate finger <NUM>-<NUM> in <FIG> in parallel with the gate finger <NUM>-<NUM>.

One end of the via hole <NUM>-n is connected to the source finger <NUM>-n, and the other end of the via hole <NUM>-n is connected to the ground.

A bus bar <NUM> is connected to the drain fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-source transistor <NUM>, and is also connected to source fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-gate transistor <NUM>.

A gate terminal <NUM> includes gate terminals <NUM>-<NUM> and <NUM>-<NUM>.

The gate terminal <NUM> is a terminal to which a gate bias is applied.

Each of the gate terminals <NUM>-<NUM> and <NUM>-<NUM> is connected to a gate bus bar <NUM> to be described later.

The common-gate transistor <NUM> includes the source electrode 32a, a drain electrode 32b, and a gate electrode 32c.

The source electrode 32a of the common-gate transistor <NUM> is connected to the drain electrode 12b of the common-source transistor <NUM>.

The drain electrode 32b of the common-gate transistor <NUM> is connected to a signal output terminal <NUM> to be described later.

The gate electrode 32c of the common-gate transistor <NUM> is connected to the gate terminal <NUM> and a capacitor <NUM>. The capacitor <NUM> is any one of capacitors <NUM>-<NUM> to <NUM>-<NUM> to be described later.

The common-gate transistor <NUM> amplifies a high-frequency signal output from the drain electrode 12b of the common-source transistor <NUM>, and outputs the amplified high-frequency signal from the drain electrode 32b to the signal output terminal <NUM>.

As the common-gate transistor <NUM>, for example, a GaN multi-finger transistor made of GaN formed on the MMIC is used.

The source electrode 32a includes the source fingers <NUM>-<NUM> to <NUM>-<NUM>.

One end of each of the source fingers <NUM>-<NUM> to <NUM>-<NUM> is connected to the bus bar <NUM>.

The drain electrode 32b includes drain fingers <NUM>-<NUM> to <NUM>-<NUM>.

One end of each of the drain fingers <NUM>-<NUM> to <NUM>-<NUM> is connected to a drain bus bar <NUM> to be described later.

The drain finger <NUM>-<NUM> is disposed between a gate finger <NUM>-<NUM> to be described later and a gate finger <NUM>-<NUM> to be described later in parallel with each of the gate fingers <NUM>-<NUM> and <NUM>-<NUM>.

The gate electrode 32c includes the gate fingers <NUM>-<NUM> to <NUM>-<NUM>.

The gate finger <NUM>-<NUM> is disposed between the source finger <NUM>-<NUM> and the drain finger <NUM>-<NUM> in parallel with each of the source finger <NUM>-<NUM> and the drain finger <NUM>-<NUM>.

The gate finger <NUM>-<NUM> is disposed between the drain finger <NUM>-<NUM> and the source finger <NUM>-<NUM> in parallel with each of the drain finger <NUM>-<NUM> and the source finger <NUM>-<NUM>.

The drain bus bar <NUM> is connected to each of the drain fingers <NUM>-<NUM> to <NUM>-<NUM> and the signal output terminal <NUM>.

The signal output terminal <NUM> is connected to the drain bus bar <NUM>.

The signal output terminal <NUM> is a terminal for outputting the high-frequency signal amplified by the common-gate transistor <NUM> to the outside.

In the high-frequency amplifier <NUM> illustrated in <FIG>, although not illustrated, the signal output terminal <NUM> is connected to an output-side matching circuit.

The gate bus bar <NUM> is connected to each of the gate terminals <NUM>-<NUM> and <NUM>-<NUM>, the gate fingers <NUM>-<NUM> to <NUM>-<NUM>, and the capacitors <NUM>-<NUM> to <NUM>-<NUM> to be described later.

One end of each of the capacitors <NUM>-<NUM> to <NUM>-<NUM> is connected to the gate bus bar <NUM>.

The other end of each of the capacitors <NUM>-<NUM> to <NUM>-<NUM> is connected to the ground.

The capacitor <NUM>-<NUM> is provided on the source finger <NUM>-<NUM>.

The capacitor <NUM>-<NUM> is provided on the source finger <NUM>-<NUM>, and the capacitor <NUM>-<NUM> is also provided on the source finger <NUM>-<NUM>.

The capacitors <NUM>-<NUM> to <NUM>-<NUM> are arranged at respective positions where impedances obtained by looking toward the capacitor <NUM> from the respective gate fingers <NUM>-m (m=<NUM>, <NUM>,. , <NUM>) of the common-gate transistor <NUM> are equal to each other. The impedance obtained by looking toward the capacitor <NUM> is a combined impedance obtained by looking toward all the capacitors <NUM>-<NUM> to <NUM>-<NUM>.

That is, the capacitors <NUM>-<NUM> to <NUM>-<NUM> are arranged at positions where distances Lm from the respective gate fingers <NUM>-m of the common-gate transistor <NUM> to one capacitor <NUM>-m related to the respective gate fingers <NUM>-m of the common-gate transistor <NUM> among the capacitors <NUM>-<NUM> to <NUM>-<NUM> are the same as each other. L1 = L2 = L3 = L4 = L5 = L6 = L7 = L8.

Among the capacitors <NUM>-<NUM> to <NUM>-<NUM>, one related capacitor <NUM>-m is a capacitor that has a correspondence relationship with the gate finger <NUM>-m, that is, a capacitor closest to the gate finger <NUM>-m. That is, among the capacitors <NUM>-<NUM> to <NUM>-<NUM>, the capacitor related to the gate finger <NUM>-m is the capacitor <NUM>-m.

In the high-frequency amplifier <NUM> illustrated in <FIG>, the capacitors <NUM>-<NUM> to <NUM>-<NUM> are arranged at positions where L1 = L2 = L3 = L4 = L5 = L6 = L7 = L8. However, it is only required that the impedances obtained by looking toward the capacitor <NUM> from the respective gate fingers <NUM>-m are equal to each other within a range that does not cause a practical problem. Therefore, strictly speaking, L1 = L2 = L3 = L4 = L5 = L6 = L7 = L8 does not need to be satisfied, and a case where the distances L1 to L8 are substantially equal to each other is also included. The impedance obtained by looking toward the capacitor <NUM> includes the impedance of the capacitor <NUM>.

Next, an operation of the high-frequency amplifier <NUM> illustrated in <FIG> will be described.

A direct-current drain voltage is applied to the signal output terminal <NUM> in order to enable both the common-source transistor <NUM> and the common-gate transistor <NUM> to operate.

In order to enable the common-source transistor <NUM> to operate, a direct-current gate voltage is applied to the signal input terminal <NUM>.

Furthermore, in order to enable the common-gate transistor <NUM> to operate, a direct-current gate voltage is applied to the gate terminal <NUM>, which is one of the gate terminal <NUM>-<NUM> and the gate terminal <NUM>-<NUM>.

When a high-frequency signal is applied to the signal input terminal <NUM> as a signal to be amplified, the high-frequency signal is distributed to the gate fingers <NUM>-<NUM> to <NUM>-<NUM> by the gate bus bar <NUM>.

When the high-frequency signals distributed by the gate bus bar <NUM> are respectively applied to the gate fingers <NUM>-<NUM> to <NUM>-<NUM>, the common-source transistor <NUM> amplifies each of the high frequency signals.

The common-source transistor <NUM> then outputs the amplified high-frequency signals to the drain fingers <NUM>-<NUM> to <NUM>-<NUM>.

The amplified high-frequency signals output to the drain fingers <NUM>-<NUM> to <NUM>-<NUM> are distributed to the source fingers <NUM>-<NUM> to <NUM>-<NUM> by the bus bar <NUM>.

When the high-frequency signals distributed by the bus bar <NUM> are respectively applied to the source fingers <NUM>-<NUM> to <NUM>-<NUM>, the common-gate transistor <NUM> amplifies each of the high frequency signals.

The common-gate transistor <NUM> then outputs the amplified high-frequency signals to the drain fingers <NUM>-<NUM> to <NUM>-<NUM>.

The amplified high-frequency signals output to the drain fingers <NUM>-<NUM> to <NUM>-<NUM> are combined by the drain bus bar <NUM>, and the combined high-frequency signal is output to the signal output terminal <NUM>.

When the capacitance of the capacitors <NUM>-<NUM> to <NUM>-<NUM> connected to the gate electrode 32c changes, the voltage amplitude between the gate electrode 32c and the source electrode 32a in the common-gate transistor <NUM> changes.

In the high-frequency amplifier <NUM> illustrated in <FIG>, when a high-frequency signal is applied to the signal input terminal <NUM>, capacitances C1 to C8 of the capacitors <NUM>-<NUM> to <NUM>-<NUM> are set in such a way that the voltage amplitude between the gate electrode 12a and the source electrode 12c in the common-source transistor <NUM> is equal to the voltage amplitude between the gate electrode 32c and the source electrode 32a. When the capacitances C1 to C8 of the capacitors <NUM>-<NUM> to <NUM>-<NUM> are set as described above, the common-source transistor <NUM> and the common-gate transistor <NUM> ideally operate in phase and with the same amplitude.

In the high-frequency amplifier <NUM> illustrated in <FIG>, the capacitances C1 to C8 of the capacitors <NUM>-<NUM> to <NUM>-<NUM> are set to C1 = C2 = C3 = C4 = C5 = C6 = C7 = C8.

The high-frequency amplifier <NUM> in a case where the common-source transistor <NUM> and the common-gate transistor <NUM> operate in phase and with the same amplitude can apply a drain voltage twice as high as that of a high-frequency amplifier including only one common-source transistor to the signal output terminal <NUM>. Therefore, the high-frequency amplifier <NUM> in the case of operating in phase and with the same amplitude can obtain output power twice as large as the high-frequency amplifier including only one common-source transistor.

In the high-frequency amplifier disclosed in Patent Literature <NUM>, since the parasitic components of the gate fingers of the common-gate FET are different from each other, there is an imbalance between the amplification operations of the gate fingers.

In the high-frequency amplifier <NUM> illustrated in <FIG>, the capacitors <NUM>-<NUM> to <NUM>-<NUM> are arranged at positions where the distances Lm from the gate finger <NUM>-m to the capacitor <NUM>-m are the same as each other. As illustrated in <FIG>, the impedances obtained by looking toward the capacitor <NUM>-m from the gate finger <NUM>-m are equal to each other.

Therefore, the imbalance between the amplification operations of the gate fingers <NUM>-<NUM> to <NUM>-<NUM> is eliminated. By eliminating the imbalance between the amplification operations, the combined loss of the high-frequency signals amplified by the gate fingers <NUM>-<NUM> to <NUM>-<NUM> is reduced.

<FIG> is an explanatory diagram illustrating the impedance each obtained by looking toward the capacitor <NUM>-m from the gate finger <NUM>-m (m=<NUM>, <NUM>,. In <FIG>, an arrow indicates a portion constituting the parasitic impedance between the gate finger <NUM>-m and the capacitor <NUM>-m.

In the high-frequency amplifier <NUM> illustrated in <FIG>, the impedances obtained by looking toward the capacitor <NUM>-m from the gate fingers <NUM>-m are substantially equal to each other. However, the impedances obtained by looking toward the capacitor <NUM>-m from the gate fingers <NUM>-m may be shifted from each other within a range that does not cause a practical problem. If each impedance is a shift that causes a phase shift of, for example, about ± <NUM>° or less with respect to an operation frequency, there is no practical problem.

In the high-frequency amplifier <NUM> illustrated in <FIG>, the capacitors <NUM>-<NUM> to <NUM>-<NUM> are connected to the gate bus bar <NUM>. However, this is only an example, and as illustrated in <FIG>, capacitors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> may be connected to the gate bus bar <NUM>.

<FIG> is a configuration diagram illustrating another high-frequency amplifier <NUM> according to the first embodiment.

The capacitor <NUM>-<NUM> is a capacitor obtained by combining the capacitor <NUM>-<NUM> and the capacitor <NUM>-<NUM>, and is related to each of the gate finger <NUM>-<NUM> and the gate finger <NUM>-<NUM>.

When the capacitance of the capacitor <NUM>-<NUM> is C11, the capacitance of the capacitor <NUM>-<NUM> is C12, and the capacitance of the capacitor <NUM>-<NUM> is C13, the capacitance C1 of the capacitor <NUM>-<NUM> and the capacitance C8 of the capacitor <NUM>-<NUM> are each half the capacitance C11, C12, or C13 as indicated by the following expression (<NUM>).

In the high-frequency amplifier <NUM> illustrated in <FIG>, the capacitance C1 of the capacitor <NUM>-<NUM> and the capacitance C8 of the capacitor <NUM>-<NUM> are each half the capacitance C11, C12, or C13. However, the capacitance C1 of the capacitor <NUM>-<NUM> and the capacitance C8 of the capacitor <NUM>-<NUM> are not limited to half of the capacitance C11, C12, or C13.

The high-frequency signals provided from the drain fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-source transistor <NUM> to the source fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-gate transistor <NUM> may not be completely in phase. In addition, in examples not falling within the scope of the claimed invention, the impedances obtained by looking toward the signal output terminal <NUM> from the respective gate fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-gate transistor <NUM> may not be equal to each other.

In these cases not according to the claimed invention, by adjusting the capacitances C1 to C8 of the capacitors <NUM>-<NUM> to <NUM>-<NUM>, the imbalance between the amplification operations of the gate fingers <NUM>-<NUM> to <NUM>-<NUM> is eliminated. For example, in a case where the parasitic inductances in the gate finger <NUM>-<NUM> and the gate finger <NUM>-<NUM> are larger than the parasitic inductances in the gate fingers <NUM>-<NUM> to <NUM>-<NUM>, the imbalance is eliminated if the capacitance C1 of the capacitor <NUM>-<NUM> and the capacitance C8 of the capacitor <NUM>-<NUM> are made to be smaller than half of the capacitance C11, C12, or C13.

In the first embodiment described above, the high-frequency amplifier <NUM> includes the common-source transistor <NUM> that includes the gate fingers <NUM>-<NUM> to <NUM>-<NUM>, the drain fingers <NUM>-<NUM> to <NUM>-<NUM>, and the source fingers <NUM>-<NUM> to <NUM>-<NUM>, amplifies a signal to be amplified applied to each gate finger <NUM>-m (m=<NUM>, <NUM>,. , <NUM>), and outputs the amplified signal from each drain finger <NUM>-j (j=<NUM>, <NUM>, <NUM>, and <NUM>), and the common-gate transistor <NUM> that includes the source fingers <NUM>-<NUM> to <NUM>-<NUM> connected to the drain fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-source transistor <NUM>, the drain fingers <NUM>-<NUM> to <NUM>-<NUM>, and the gate fingers <NUM>-<NUM> to <NUM>-<NUM>, and amplifies the amplified signal output from each drain finger <NUM>-j of the common-source transistor <NUM>. The high-frequency amplifier <NUM> also includes the gate bus bar <NUM> connected to the gate fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-gate transistor <NUM>, and the capacitors <NUM>-<NUM> to <NUM>-<NUM> each of which has one end connected to the gate bus bar <NUM> and the other end grounded. The high-frequency amplifier <NUM> is configured in such a way that the capacitors <NUM>-<NUM> to <NUM>-<NUM> are arranged at positions where the impedances obtained by looking toward the capacitor <NUM> from the respective gate fingers <NUM>-m of the common-gate transistor <NUM> are equal to each other. As a result, the high-frequency amplifier <NUM> can reduce the imbalance between the amplification operations of the gate fingers <NUM>-<NUM> to <NUM>-<NUM>.

In the high-frequency amplifiers <NUM> illustrated in <FIG> and <FIG>, the common-source transistor <NUM> and the common-gate transistor <NUM> are separate transistors. However, this is only an example, and for example, as illustrated in <FIG>, it is possible to use a dual gate transistor in which the common-source transistor <NUM> and the common-gate transistor <NUM> are implemented in one transistor cell.

<FIG> is a configuration diagram illustrating still another high-frequency amplifier <NUM> according to the first embodiment.

The high-frequency amplifier <NUM> illustrated in <FIG> includes drain source fingers <NUM>-<NUM> to <NUM>-<NUM>. The drain source fingers <NUM>-<NUM> to <NUM>-<NUM> are fingers in which the drain fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-source transistor <NUM> and the source fingers <NUM>-<NUM> to <NUM>-<NUM> of the common-gate transistor <NUM> are integrated.

In the high-frequency amplifier <NUM> illustrated in <FIG>, the gate fingers <NUM>-<NUM> to <NUM>-<NUM>, the source fingers <NUM>-<NUM> to <NUM>-<NUM>, the drain source fingers <NUM>-<NUM> to <NUM>-<NUM>, the drain fingers <NUM>-<NUM> to <NUM>-<NUM>, and the gate fingers <NUM>-<NUM> to <NUM>-<NUM> are arranged in parallel with each other.

The high-frequency amplifier <NUM> illustrated in <FIG> includes the capacitors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> similarly to the high-frequency amplifier <NUM> illustrated in <FIG>, but does include the capacitors <NUM>-<NUM> to <NUM>-<NUM> similarly to the high-frequency amplifier <NUM> illustrated in <FIG>.

When the common-source transistor <NUM> and the common-gate transistor <NUM> are implemented as a dual gate transistor, a high-frequency amplifier having a higher frequency or a wider band than the high-frequency amplifiers <NUM> illustrated in <FIG> and <FIG> can be implemented.

If the gate of the common-source transistor <NUM> and the gate of the common-gate transistor <NUM> are in the same channel, the drain source fingers <NUM>-<NUM> to <NUM>-<NUM> may be omitted.

In the high-frequency amplifier <NUM> illustrated in <FIG>, one end of each of the capacitors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> is connected to the gate bus bar <NUM>. Alternatively, one end of each of the capacitors <NUM>-<NUM> to <NUM>-<NUM> is connected to the gate bus bar <NUM>.

However, this is only an example, and for example, as illustrated in <FIG>, one end of the capacitor <NUM>-m (m=<NUM>, <NUM>,. , <NUM>) may be connected to each gate finger <NUM>-m of the common-gate transistor <NUM> via an air bridge <NUM>-m.

<FIG> is a configuration diagram illustrating yet another high-frequency amplifier <NUM> according to the first embodiment.

<FIG> is a cross-sectional view taken along line A<NUM>-A<NUM> in <FIG>.

One end of the air bridge <NUM>-m (m=<NUM>, <NUM>,. , <NUM>) is connected to the gate finger <NUM>-m, and the other end of the air bridge <NUM>-m is connected to one end of the capacitor <NUM>-m.

In the configuration in which one end of the capacitor <NUM>-m is connected to the gate finger <NUM>-m via the air bridge <NUM>-m, the parasitic component between the gate finger <NUM>-m and the capacitor <NUM>-m is smaller than that in the configuration in which one end of the capacitor <NUM>-m is connected to the gate bus bar <NUM>.

In a second embodiment, a high-frequency amplifier <NUM> including shunt feedback capacitors <NUM>-<NUM> to <NUM>-<NUM> will be described.

<FIG> is a configuration diagram illustrating the high-frequency amplifier <NUM> according to the second embodiment. In <FIG>, the same reference numerals as those in <FIG> and <FIG> denote the same or corresponding parts, and thus description thereof is omitted.

In the high-frequency amplifier <NUM> illustrated in <FIG>, the shunt feedback capacitors <NUM>-<NUM> to <NUM>-<NUM> are applied to the high-frequency amplifier <NUM> illustrated in <FIG>. However, this is only an example, and the shunt feedback capacitors <NUM>-<NUM> to <NUM>-<NUM> may be applied to the high-frequency amplifier <NUM> illustrated in <FIG>.

<FIG> is an equivalent circuit diagram illustrating the high-frequency amplifier <NUM> according to the second embodiment. In <FIG>, the same reference numerals as those in <FIG> denote the same or corresponding parts, and thus description thereof is omitted.

The shunt feedback capacitor <NUM> is any one of the shunt feedback capacitors <NUM>-<NUM> to <NUM>-<NUM>.

One end of the shunt feedback capacitor <NUM>-j (j=<NUM>, <NUM>, <NUM>, and <NUM>) is connected to the drain finger <NUM>-j via an air bridge <NUM>-j.

The other end of the shunt feedback capacitor <NUM>-j is connected to the drain finger <NUM>-j.

One end of the air bridge <NUM>-j is connected to the drain finger <NUM>-j, and the other end of the air bridge <NUM>-j is connected to one end of the shunt feedback capacitor <NUM>-j.

As the high-frequency amplifier <NUM> includes the shunt feedback capacitors <NUM>-<NUM> to <NUM>-<NUM>, impedance matching between the common-source transistor <NUM> and the common-gate transistor <NUM> can be implemented.

Since the shunt feedback capacitors <NUM>-<NUM> to <NUM>-<NUM> are arranged in a distributed manner for each of the drain fingers <NUM>-j, an imbalanced operation of the drain fingers <NUM>-<NUM> to <NUM>-<NUM> is suppressed.

In the high-frequency amplifiers <NUM> illustrated in <FIG>, the common-source transistor <NUM> and the common-gate transistor <NUM> are separate transistors. However, this is only an example, and for example, as illustrated in <FIG>, it is possible to use a dual gate transistor in which the common-source transistor <NUM> and the common-gate transistor <NUM> are implemented in one transistor cell.

<FIG> is a configuration diagram illustrating another high-frequency amplifier <NUM> according to the second embodiment.

The high-frequency amplifier <NUM> illustrated in <FIG> includes the capacitors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> similarly to the high-frequency amplifier <NUM> illustrated in <FIG>, but may include the capacitors <NUM>-<NUM> to <NUM>-<NUM> similarly to the high-frequency amplifier <NUM> illustrated in <FIG>.

When the common-source transistor <NUM> and the common-gate transistor <NUM> are implemented as a dual gate transistor, a high-frequency amplifier having a higher frequency or a wider band than the high-frequency amplifiers <NUM> illustrated in <FIG> can be implemented.

In the high-frequency amplifier <NUM> according to the first and second embodiments, the capacitors <NUM>-<NUM> to <NUM>-<NUM> or the capacitors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> are implemented by metal insulator metal (MIM) capacitors. The capacitors <NUM>-<NUM> to <NUM>-<NUM> and <NUM>-<NUM> to <NUM>-<NUM> are not limited to MIM capacitors, and may be implemented by, for example, interdigital capacitors.

In the high-frequency amplifier <NUM> according to the first and second embodiments, each of the capacitors <NUM>-<NUM> to <NUM>-<NUM> and the like is formed on any of the source fingers <NUM>-<NUM> to <NUM>-<NUM>. However, this is only an example, and it is only required that each of the capacitors <NUM>-<NUM> to <NUM>-<NUM> and the like is disposed between each of the gate fingers <NUM>-<NUM> to <NUM>-<NUM> and each of the source fingers <NUM>-<NUM> to <NUM>-<NUM>. Each of the capacitors <NUM>-<NUM> to <NUM>-<NUM> and the like may be formed on the gate bus bar <NUM> and then connected to the ground via an air bridge.

In the high-frequency amplifier <NUM> according to the first and second embodiments, each of the common-source transistor <NUM> and the common-gate transistor <NUM> is implemented by a GaN multi-finger transistor. However, this is only an example, and each of the common-source transistor <NUM> and the common-gate transistor <NUM> may be a transistor formed on a substrate whose material is GaAs (gallium arsenide) or the like.

Further, each of the common-source transistor <NUM> and the common-gate transistor <NUM> may be implemented by a bipolar transistor instead of a field effect transistor.

In the high-frequency amplifier <NUM> according to the first and second embodiments, each capacitor <NUM> is disposed at a position sandwiched between two gate fingers <NUM> or a position adjacent to one gate finger <NUM>.

The capacitors <NUM>-<NUM> to <NUM>-<NUM> and the like are only required to be arranged at positions where the impedances obtained by looking toward the capacitor <NUM> from the respective gate fingers <NUM>-m are equal to each other, and are not limited to those arranged as illustrated in <FIG> or <FIG>. In examples not falling within the scope of the claimed invention, the capacitors <NUM> may be dispersedly arranged in every several gate fingers <NUM>, and the effect of reducing the imbalance is obtained.

In the high-frequency amplifier <NUM> according to the first and second embodiments, the common-source transistor <NUM> and the common-gate transistor <NUM> are cascade-connected as two transistors. However, this is only an example, and three or more transistors may be cascade-connected.

The present disclosure is suitable for a high-frequency amplifier that amplifies a high-frequency signal.

The present disclosure is suitable for a radio communication device including the high-frequency amplifier.

The present disclosure is suitable for a radar device including the high-frequency amplifier.

Claim 1:
A high-frequency amplifier (<NUM>) comprising:
a common-source transistor (<NUM>) that has a plurality of gate fingers (<NUM>-<NUM> to <NUM>-<NUM>), a plurality of drain fingers (<NUM>-<NUM> to <NUM>-<NUM>), and a plurality of source fingers (<NUM>-<NUM> to <NUM>-<NUM>), and that is configured to amplify a signal applied to each of the gate fingers (<NUM>-<NUM> to <NUM>-<NUM>) as a signal to be amplified, and configured to output an amplified signal from each of the drain fingers (<NUM>-<NUM> to <NUM>-<NUM>);
a common-gate transistor (<NUM>) that has a plurality of source fingers (<NUM>-<NUM> to <NUM>-<NUM>) connected to the drain fingers (<NUM>-<NUM> to <NUM>-<NUM>) of the common-source transistor (<NUM>), a plurality of drain fingers (<NUM>-<NUM> to <NUM>-<NUM>), and a plurality of gate fingers (<NUM>-<NUM> to <NUM>-<NUM>), and that is configured to amplify the amplified signal output from each of the drain fingers of the common-source transistor (<NUM>);
a gate bus bar (<NUM>) connected to the gate fingers (<NUM>-<NUM> to <NUM>-<NUM>) of the common-gate transistor (<NUM>); and
a plurality of capacitors (<NUM>-<NUM> to <NUM>-<NUM>) each having a first end connected to the gate bus bar (<NUM>) and a second end grounded,
wherein the capacitors (<NUM>-<NUM> to <NUM>-<NUM>) are arranged at respective positions where distances from the respective gate fingers (<NUM>-<NUM> to <NUM>-<NUM>) of the common-gate transistor (<NUM>) to the respective capacitors (<NUM>-<NUM> to <NUM>-<NUM>) related to the respective gate fingers (<NUM>-<NUM> to <NUM>-<NUM>) of the common-gate transistor (<NUM>) are equal to each other, wherein impedances obtained by looking toward the respective capacitors (<NUM>-<NUM> to <NUM>-<NUM>) from the respective gate fingers (<NUM>-<NUM> to <NUM>-<NUM>) of the common-gate transistor (<NUM>) are equal to each other, and
wherein each of the capacitors (<NUM>-<NUM> to <NUM>-<NUM>) is disposed between each of the gate fingers (<NUM>-<NUM> to <NUM>-<NUM>) of the common-gate transistor (<NUM>) and each of the source fingers (<NUM>-<NUM> to <NUM>-<NUM>) of the common-source transistor (<NUM>),
wherein each of the source fingers (<NUM>-<NUM> to <NUM>-<NUM>) of the common-source transistor (<NUM>) is a source electrode with an individual source via, ISV, structure having a via hole, and
wherein each of the capacitors (<NUM>-<NUM> to <NUM>-<NUM>) are provided on the corresponding source electrode.