JP2008283473A - Power amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power amplifier which can reduce insertion loss and power consumption and can be prevented from being made large in size. <P>SOLUTION: The power amplifier 1 includes: a power distributor 2 for dividing an input signal into a plurality of signals and outputting them; a plurality of phase shifters 3 which are individually connected to the power distributor 2 and shift respective phases of the plurality of signals outputted from the power distributor 2 and output the plurality of phase shifted signals; unit amplifiers 4 individually connected to the plurality of phase shifters 3; a power synthesizer 5 connected to the plurality of unit amplifiers 4; and a potential supplier 6 connected to the plurality of phase shifters 3. Each phase shifter includes a signal line where a signal outputted from the power distributor flows, and a plurality of electrostatic capacitive micromachine switches arranged in a direction of extension of the signal line. The potential supplier 6 supplies potentials to be given to the plurality of micromachine switches, to the plurality of phase shifters 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power amplifier that amplifies a signal, and more particularly, to a power amplifier that amplifies a high-frequency signal.

  Power amplifiers are used in various electronic devices such as antenna devices mounted on aircraft, ships, automobiles, and the like as satellite communication devices. The power amplifier includes a power distributor that distributes and outputs an input signal, a plurality of phase shifters individually connected to the power distributor, and a plurality of unit amplifiers individually connected to the phase shifters. (Amplifying elements), a power combiner connected to these unit amplifiers, and a controller connected to each phase shifter (see, for example, Patent Document 1).

  In such a power amplifier, an input signal is distributed to a plurality of signals by a power distributor, and the plurality of distributed signals are changed to predetermined phases and amplitudes by a phase shifter and a unit amplifier, respectively, and then by a power combiner. Combine and output as output signal. At this time, if the phase amounts of the signals passing through the unit amplifiers are different due to individual differences or manufacturing accuracy of the unit amplifiers, a loss occurs when the signals are combined by the power combiner. For this reason, each phase amount of each phase shifter is adjusted so that the loss is minimized.

Usually, the phase shifter includes a plurality of signal lines having different lengths and a plurality of changeover switches for controlling the connection thereof. This phase shifter changes the total length of the signal line in accordance with on / off of the changeover switch by the controller, and changes the phase of the signal passing through the signal line. Examples of such a phase shifter include a line switching type phase shifter, a loaded line type phase shifter, and a hybrid coupled type phase shifter.
JP 2001-196870 A

  However, in the above-described phase shifter, in order to change the phase amount of the signal passing through the signal line, it is necessary to provide a plurality of signal lines having different lengths. The number will also increase. This increases insertion loss and power consumption, and further increases the size of the power amplifier.

  The present invention has been made in view of the above, and an object of the present invention is to provide a power amplifier that can suppress insertion loss and power consumption and can prevent an increase in size.

  According to the embodiment of the present invention, in a power amplifier, a power distributor that divides an input signal into a plurality of signals and outputs, and a plurality of signals that are individually connected to the power distributor and output from the power distributor A plurality of phase shifters that respectively output a plurality of signals with different phases, respectively, and a plurality of signals that are individually connected to the plurality of phase shifters and output from the plurality of phase shifters Connected to a plurality of unit amplifiers, a plurality of unit amplifiers, a power combiner that combines and outputs a plurality of signals output from the plurality of unit amplifiers, and a plurality of phase shifters A plurality of phase shifters, a signal line through which a signal output from the power distributor flows, and a direction in which the signal line extends with respect to the signal line. Capacitance type micros arranged in a row And comprising thin switch and each potential supplier is to supply respectively the potential applied to the plurality of micromachine switches to a plurality of phase shifters.

  According to the present invention, it is possible to provide a power amplifier capable of suppressing insertion loss and power consumption and further preventing an increase in size.

  Embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a power amplifier 1 according to an embodiment of the present invention includes a power distributor 2 that distributes and outputs an input signal, and a plurality (for example, two) connected to the power distributor 2 individually. ), A plurality of (for example, two) unit amplifiers 4 individually connected to the phase shifters, a power combiner 5 connected to the unit amplifiers 4, and each phase shifter 3 and a potential supply 6 connected to 3. Note that one phase shifter 3 and one unit amplifier 4 constitute amplification units Z1 and Z2.

  The power distributor 2 includes one input terminal 2a to which a signal is input and a plurality of (for example, two) output terminals 2b to which a signal is output. The input terminal 2 a of the power distributor 2 is connected to the input terminal 1 a of the power amplifier 1. Such a power distributor 2 distributes an input signal input from the input terminal 1a of the power amplifier 1, that is, a signal input to the input terminal 2a, to each output terminal 2b, and outputs it as a plurality of signals.

  Each phase shifter 3 includes one input terminal 3a to which a signal is input and one output terminal 3b to which a signal is output. Each input terminal 3 a of these phase shifters 3 is connected to each output terminal 2 b of the power distributor 2. Each of these phase shifters 3 changes the phase of the plurality of signals output from the power distributor 2 and outputs each signal with the changed phase from each output terminal 3b. The phase amount of each phase shifter 3 is determined by the potential supplied from the potential supplier 6.

  Each unit amplifier 4 includes one input terminal 4a to which a signal is input and one output terminal 4b to which a signal is output. Each input terminal 4 a of these unit amplifiers 4 is connected to each output terminal 3 b of each phase shifter 3. Each such unit amplifier 4 amplifies a plurality of signals output from each phase shifter 3 and outputs the amplified signal from each output terminal 4b.

  The power combiner 5 includes a plurality of (for example, two) input terminals 5a to which signals are input and one output terminal 5b to which signals are output. Each input terminal 5 a of the power combiner 5 is connected to each output terminal 4 b of each unit amplifier 4. The output terminal 5 b of the power combiner 5 is connected to the output terminal 1 b of the power amplifier 1. Such a power combiner 5 combines a plurality of signals output from the unit amplifiers 4 and outputs them as output signals from the output terminal 5 b, that is, the output terminal 1 b of the power amplifier 1.

  The potential supplier 6 is a device that supplies a potential to each phase shifter 3. That is, the potential supplier 6 supplies a predetermined potential to each phase shifter so that the difference in the phase amount of each signal passing through each phase shifter 3 is reduced. Thereby, each phase amount of each phase shifter is set.

  Next, the phase shifter 3 will be described in detail.

  As shown in FIG. 2, the phase shifter 3 includes a mounting substrate 11, a signal line 12 provided on the substrate 11 through which a signal such as a high frequency signal flows, and a direction perpendicular to the direction in which the signal line 12 extends. A pair of ground conductors 13, 14 provided on the substrate 11 so as to sandwich the signal line 12 from the substrate, and a capacitance type lined up in a direction in which the signal line 12 extends with respect to the signal line 12 on the substrate 11 A plurality of micromachine switches 15 are provided.

  The substrate 11 is formed of an insulating substrate such as a glass substrate, a high-resistance silicon substrate, a semi-insulating GaAs substrate, or the like. An insulating film (not shown) such as a silicon oxide film is provided on the surface of the silicon substrate or GaAs substrate.

  The signal line 12 is a signal line (transmission line) for a signal such as a high-frequency signal, and is arranged from one side (left side in FIG. 2) to the other side (right side in FIG. 2) facing the substrate 11. ing. The signal line 12 is formed of, for example, a Ti / Au film. The left end (in FIG. 2) of the signal line 12 is connected to the input terminal 3a, and the right end (in FIG. 2) of the signal line 12 is connected to the output terminal 3b.

  The pair of ground conductors 13 and 14 are positioned on both sides in the direction perpendicular to the extending direction of the signal line 12, and are provided in a region on the substrate 11 at a predetermined distance from the signal line 12. These ground conductors 13 and 14 together with the signal line 12 constitute a coplanar transmission line. Further, the plurality of DC cut capacitors 16 are respectively disposed on both sides of the pair of ground conductors 13 and 14 in the extending direction of the signal line 12. Here, the impedance as the coplanar transmission line can be adjusted by changing the separation distance between the pair of ground conductors 13 and 14 and the signal line 12. The pair of ground conductors 13 and 14 are formed of, for example, a Ti / Au film.

  As shown in FIGS. 3 and 4, each micromachine switch 15 includes a dielectric 15 a provided on the signal line 12 and a movable piece formed so as to be movable in a direction facing and separating from the dielectric 15 a. 15b. These micromachine switches 15 are switches for adjusting the phase of a signal passing through the signal line 12 and are arranged on the signal line 12 at a predetermined interval (pitch interval) s along the extending direction. . Here, when the frequency of the signal is a high frequency band, it is preferable to use the micromachine switch 15 having a small loss. Note that the phase shifter 3 in which a plurality of micromachine switches 15 are arranged on the signal line 12 at predetermined intervals in this way is called a distributed phase shifter. As a micromachine switch used in this distributed phase shifter, it is preferable to use a capacitance type micromachine switch 15 from the viewpoints of simple structure and ease of manufacture.

The dielectric 15a is provided in a thin film shape on the signal line 12, and faces the movable piece 15b. The dielectric 15a is formed of, for example, a single layer film of a silicon oxide (SiO ₂ ) film or a silicon nitride (Si ₃ N ₄ ) film, or a composite film obtained by stacking them. In the present embodiment, a silicon nitride film having a high dielectric constant and capable of forming dielectric 15a stably in production is used.

  The movable piece 15b is provided on the dielectric 15a so as to be separated from the dielectric 15a, and is formed so as to be deformable in a direction in contact with the dielectric 15a by voltage application. The movable piece 15b is formed in a flexible plate shape, and is fixed to the pair of ground conductors 13 and 14 by a double-supported beam structure. More specifically, one end of the movable piece 15 b is fixed to the ground conductor 13, and the other end of the movable piece 15 b is fixed to the ground conductor 14. Thereby, the movable piece 15 b is electrically connected to the pair of ground conductors 13 and 14. In addition, the movable piece 15b is disposed so as to be separated from the dielectric 15a by a gap (interval) g of several μm. The movable piece 15b is formed of a metal having plasticity and excellent electrical conductivity, such as a Ti / Au film or a Ti / Au / Ti film.

  Such a movable piece 15b is deformed in a direction in contact with the dielectric 15a by voltage application (application of supply voltage). At this time, the gap g between the dielectric 15a and the movable piece 15b varies depending on the magnitude of the supply voltage. When a voltage is applied between the movable piece 15b and the signal line 12, the movable piece 15b bends and deforms toward the signal line 12, moves toward the dielectric 15a on the signal line 12, and the voltage application is stopped. By the restoring force, it is deformed in the direction away from the dielectric 15a on the signal line 12, and returns to the original position. At the time of voltage application, a supply voltage is supplied by the potential supplier 6, and a gap g between the dielectric 15a and the movable piece 15b is set.

Here, in the phase shifter 3 described above, when one micromachine switch 15 is used as one unit, an equivalent circuit as shown in FIG. 5 is required. The capacitance Cb of the micromachine switch 15 is C _b = ε ₀ Ww / (g + t _d / ε _r ). Ε ₀ is the dielectric constant of vacuum, ε _r is the relative dielectric constant of the dielectric 15a, t _d is the thickness of the dielectric 15a, and g is the gap between the dielectric 15a and the movable piece 15b. Yes, W is the width of the signal line 12, and w is the width of the movable piece 15b (width in the direction in which the signal line 12 extends).

The impedance when the supply voltage is 0 V is ZA = √sL / (sC + C _b0 ), and the impedance when the supply voltage is XV is ZB = √sL / (sC + C _bX ). Here, s is the pitch interval of the movable piece 15b, L is the inductance, C _b0 is the capacitance of the micro machine switch 15 when the supply voltage is 0V, C _bX if the supply voltage is XV Of the micromachine switch 15. That is, when the supply voltage changes, the gap g changes, so the capacitance Cb of the micromachine switch 15 also changes.

In addition, the amount of phase change at the micromachine switch 15 site is Δφ [rad. / M] = sωZ _0f √ε _eff / c (1 / ZA−1 / ZB). Here, s is a pitch interval of each movable piece 15b, ω is 2πf, f is a desired frequency, Z _0f is a characteristic impedance of the coplanar transmission line, and ε _eff is an effective dielectric constant of the substrate 11 And c is the transmission speed in vacuum. Note that the pitch interval s of the movable piece 15b, that is, the micromachine switch 15, is one of the parameters for determining the impedances ZA and ZB and the phase change amount Δφ of the phase shifter 3.

  FIG. 6 shows an example of a change of the capacitance Cb of the micromachine switch 15 with respect to the supply voltage. As shown in FIG. 6, the capacitance (capacitance) Cb increases monotonically like an exponential function until the supply voltage is 0V to about 60V, that is, the gap g is changed from L to L / 3, and the supply voltage is about 60V. 35 fF. Thereafter, when the supply voltage exceeds about 60 V, the gap g becomes 0 (a state where the dielectric 15a and the movable piece 15b are in contact), and the capacitance (capacitance) Cb becomes about 500 fF. Here, the gap g when the supply voltage is 0 V to about 12 V is L (μm), and the gap g when the supply voltage is about 60 V is L / 3 (μm). When the gap g is L, the movable piece 15b is in the initial position (for example, the state shown in FIG. 4). Thus, since the capacitance Cb of the micromachine switch 15 changes according to the supply voltage, the phase amount of the signal flowing through the signal line 12 can be changed by changing the supply voltage.

  As shown in FIG. 7, the phase change amount of the phase shifter 3 changes according to the supply voltage. The relationship between the supply voltage and the phase change amount when the frequency of the input signal is f1 is a curve A1, and the relationship between the supply voltage and the phase change amount when the frequency of the input signal is f2 is a curve A2. The relationship between the supply voltage and the amount of phase change when the frequency of the input signal is f3 is a curve A3. Here, the relationship of f1 <f2 <f3 is established. As shown in FIG. 7, the amount of phase change increases monotonically as the supply voltage increases. Further, the amount of phase change increases as the frequency of the input signal increases.

  For example, when the frequency of the input signal is f2 and the phase change amount of the phase shifter 3 needs to be set to −20 °, the supply voltage is set to 35V. When the frequency of the input signal is f2 and the phase change amount of the phase shifter 3 needs to be set to −40 °, the supply voltage is set to 55V. At this time, it is necessary to set the phase change amount of each phase shifter 3 so that the difference between the phase amounts of each phase shifter 3 becomes small, and the supply voltage is determined for each phase shifter 3. These supply voltages (potentials) are supplied to each phase shifter 3 by the potential supply 6.

  Next, the operation of the power amplifier 1 described above, particularly the operation of the phase shifter 3 will be described.

  An input signal input to the input terminal 1 a of the power amplifier 1 is input to the power distributor 2 from the input terminal 2 a of the power distributor 2. The input signal is distributed to each output terminal 2b by the power distributor 2, and is output from each output terminal 2b as a plurality of signals. Each output signal is input to each phase shifter 3 from each input terminal 3 a of each corresponding phase shifter 3. The phase of the signal input to the phase shifter 3 is changed by the phase shifter 3 and is output from the output terminal 3b. At this time, the phase amount of each phase shifter 3 is set so that the difference in the phase amount of each signal becomes small.

  Thereafter, the plurality of signals output from the respective output terminals 3 b of the respective phase shifters 3 are input to the respective unit amplifiers 4 from the respective input terminals 4 a of the corresponding respective unit amplifiers 4. These signals are amplified by each unit amplifier 4 and output from each output terminal 4b. The plurality of output signals are input to the input terminals 5 a of the power combiner 5. These signals are combined by the power combiner 5 and output as an output signal from the output terminal 5b, that is, the output terminal 1b of the power amplifier 1.

  At this time, a predetermined potential is supplied to each phase shifter 3 by the potential supplier 6. The phase shifter 3 determines the capacitance of each micromachine switch 15 in accordance with the potential supplied from the potential supplier 6 and sets the phase amount of the signal passing through the signal line 12. More specifically, each micromachine switch 15 of the phase shifter 3 is in an initial state where the movable piece 15b and the dielectric 15a are separated when a supply voltage is applied between the movable piece 15b and the signal line 12. From the state where the gap g is L, the movable piece 15b is deformed to bend and deform toward the dielectric 15a side, that is, the signal line 12 side. Accordingly, the gap g between the dielectric 15a and the movable piece 15b changes to a predetermined gap value, and the phase amount of the phase shifter 3 becomes a predetermined value. Thereby, the phase of the signal passing through the signal line 12 is changed by a predetermined phase amount. At this time, since a predetermined supply voltage is supplied to each phase shifter 3 so that the difference between the phase amounts of the respective signals becomes small, the loss caused when the signals passing through different signal paths are combined is minimized. Can be.

  As described above, according to the power amplifier 1 according to the embodiment of the present invention, as the plurality of phase shifters 3, the signal line 12 through which the signal output from the power distributor 2 flows and the signal line 12 are used. The phase shifters 3 having a plurality of capacitance type micromachine switches 15 arranged in the direction in which the signal lines 12 extend are provided, and potentials applied to the respective micromachine switches 15 are supplied to the phase shifters 3 respectively. As a result, it is not necessary to provide multiple signal lines with different lengths in order to change the signal phase amount as in the past, and it is possible to prevent an increase in the number of signal lines and an increase in the number of changeover switches accordingly. become. Thereby, insertion loss and power consumption can be suppressed, and further increase in size can be prevented.

  In addition, each micromachine switch 15 is provided on the dielectric 15a spaced apart from the dielectric 15a provided on the signal line 12, and can be deformed in a direction in contact with the dielectric 15a by applying a voltage. The micromachine switch 15 can be constructed with a simple structure in which the movable piece 15b is provided on the signal line 12 via the dielectric 15a.

  Next, a method for manufacturing the phase shifter 3, particularly a method for manufacturing the micromachine switch 15, will be described with reference to FIGS. 8 to 15.

  First, the substrate 11 is prepared. The substrate 11 is formed of an insulating substrate or a semiconductor substrate. As the substrate 11, for example, a glass substrate, a sapphire substrate, a silicon substrate having a silicon oxide film, or the like is used.

  As shown in FIG. 8, a conductive layer 21 is formed on the entire surface of the substrate 11. Here, the conductive layer 21 is formed of, for example, a Ti / Au film. Subsequently, as shown in FIG. 8, a patterning photoresist film 22 is formed on the conductive layer 21. The photoresist film 22 is used as a mask for patterning the shapes of the signal line 12 and the pair of ground conductors 13 and 14.

  Next, the conductive layer 21 is etched using the photoresist film 22, and then the photoresist film 22 is removed. As shown in FIG. 9, the signal line 12 and a pair of grounds are formed on the substrate 11 from the conductive layer 21. Conductors 13 and 14 are formed.

Next, as shown in FIG. 10, a dielectric layer 23 covering the signal line 12 and the pair of ground conductors 13 and 14 is formed on the entire surface of the substrate 11. For example, a silicon nitride film (Si ₃ N ₄ ) is used as the dielectric layer 23. Subsequently, as shown in FIG. 10, a photoresist film 24 for patterning is formed on the dielectric layer 23. The photoresist film 24 is provided on the signal line 12 in order to leave the dielectric layer 23 on the signal line 12.

  Next, the dielectric film 23 is etched using the photoresist film 24, and then the photoresist film 24 is removed to form a dielectric 15a on the signal line 12 from the dielectric layer 23 as shown in FIG.

  Next, as shown in FIG. 12, a sacrificial layer 25 for forming a plurality of movable pieces 15 b is formed on the entire surface of the substrate 11. As the sacrificial layer 25, for example, a photoresist film is used. The sacrificial layer 25 is provided with a plurality of openings K1 and K2 for forming a connection portion between each movable piece 15b and the pair of ground conductors 13 and 14. Each opening K1 is provided on a straight line along the ground conductor 13, and each opening K2 is also provided on a straight line along the ground conductor 14.

  Next, as shown in FIG. 13, a metal layer 26 is formed on the sacrificial layer 25, and a patterning photoresist film 27 is formed on the metal layer 26. This photoresist film 27 is used as a mask for patterning the movable piece 15b.

  Next, the metal layer 26 is etched using the photoresist film 27, and then the photoresist film 27 is removed to form a plurality of movable pieces 15b from the metal layer 26 as shown in FIG. Finally, as shown in FIG. 15, the sacrificial layer 25 is removed. Thereby, the phase shifter 3 having a plurality of micromachine switches 15 as shown in FIGS. 3 and 4 is completed (see FIG. 2).

  As described above, according to the manufacturing method according to the embodiment of the present invention, a phase shifter having a plurality of micromachine switches 15 easily using an existing semiconductor manufacturing process without using a special manufacturing method. 3 can be manufactured.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  For example, in the above-described embodiment, both ends of the movable piece 15b are fixed to the pair of ground conductors 13 and 14, and the movable piece 15b is provided on the substrate 11 with a double-supported beam structure. Alternatively, for example, only one end of the movable piece 15b may be fixed to one of the pair of ground conductors 13 and 14, and the movable piece 15b may be provided on the substrate 11 by a cantilever structure.

  In the above-described embodiment, a predetermined potential (predetermined supply voltage) is supplied to each phase shifter 3 by the potential supply 6. However, the present invention is not limited to this. You may make it supply to each phase shifter 3 by the supplier 6 changing the electric potential given according to the frequency of an input signal, respectively. In this case, the potential supplier 6 changes the potential based on frequency information indicating the frequency of the input signal.

  Finally, in the above-described embodiment, various numerical values are listed, but these numerical values are merely examples and are not limited.

1 is a block diagram showing a schematic configuration of a power amplifier according to an embodiment of the present invention. It is a top view which shows schematic structure of the phase shifter with which the power amplifier shown in FIG. 1 is provided. It is a top view which shows schematic structure of the micromachine switch with which the phase shifter shown in FIG. 2 is provided. FIG. 3 is a cross-sectional view taken along line F1-F1 of FIG. FIG. 5 is a circuit diagram showing an equivalent circuit of the micromachine switch shown in FIGS. 3 and 4. It is explanatory drawing for demonstrating the relationship between a supply voltage and the capacity | capacitance (capacitance) of a micromachine switch. It is explanatory drawing for demonstrating the relationship between a supply voltage and the phase variation of a phase shifter. FIG. 6 is a first process cross-sectional view for explaining the manufacturing method of the micromachine switch shown in FIGS. 3 and 4. It is 2nd process sectional drawing. It is 3rd process sectional drawing. It is a 4th process sectional view. FIG. 10 is a fifth process cross-sectional view. It is 6th process sectional drawing. It is 7th process sectional drawing. It is 8th process sectional drawing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Power amplifier, 2 ... Power divider, 3 ... Phase shifter, 4 ... Unit amplifier, 5 ... Power synthesizer, 6 ... Potential supply, 12 ... Signal line, 15 ... Micromachine switch, 15a ... Dielectric, 15b ... movable piece

Claims (2)

A power divider that divides an input signal into a plurality of signals and outputs;
A plurality of phase shifters that are individually connected to the power distributor, change the phase of each of the plurality of signals output from the power distributor, and output the plurality of signals that have been changed in phase;
A plurality of unit amplifiers individually connected to the plurality of phase shifters and amplifying and outputting a plurality of signals output from the plurality of phase shifters;
A power combiner connected to the plurality of unit amplifiers for synthesizing and outputting a plurality of signals output from the plurality of unit amplifiers;
A potential supply connected to the plurality of phase shifters and supplying a potential to the plurality of phase shifters;
With
The plurality of phase shifters include a signal line through which the signal output from the power distributor flows, and a plurality of capacitance-type micromachine switches arranged in a direction in which the signal line extends with respect to the signal line. Each with
The potential amplifier supplies potentials to be supplied to the plurality of micromachine switches to the plurality of phase shifters, respectively. The plurality of micromachine switches are:
A dielectric provided on the signal line;
A movable piece that is provided on the dielectric material apart from the dielectric material and is deformable in a direction in contact with the dielectric material by applying a voltage;
The power amplifier according to claim 1, further comprising:

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