JP2013065938A - High frequency amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency amplification circuit that enables high precision and short time oscillation suppression.SOLUTION: In an embodiment, the high frequency amplifier includes: an amplifying element divided into a plurality of regions; as many input matching circuits as the division number of the amplifying element; as many output matching circuits as the division number; a first resistance group interconnecting adjacent input matching circuits which includes one or more removable resistances; and a second resistance group interconnecting adjacent output matching circuits which includes one or more removable resistances.

Description

  Embodiments described herein relate generally to a high-frequency amplifier used in a communication system or the like.

  In recent years, high-frequency amplifiers used in communication systems have been required to be small in size and low in power consumption. At the same time, in order to ensure good communication quality, performance gains such as high gain, high efficiency and low distortion have also been achieved. There are strict requirements.

  Internal amplification type FET (field effect transistor) amplifier for power amplification used for terrestrial microwave communication and satellite communication divides a plurality of FET chips and FET chips into a plurality of amplification regions, and these amplification regions are divided into a plurality of amplification regions. Generally, power amplification is performed by arranging them in parallel. In such a configuration, the input signal is evenly distributed to the plurality of amplification regions, and the output signals of the amplification regions are combined.

  However, the drive balance between multiple amplification regions deteriorates due to variations in characteristics among multiple FET chips or unit cells in an FET chip, and impedance mismatching or loss in peripheral circuits such as a distribution / synthesis circuit. Oscillation may occur.

  In order to suppress abnormal oscillation, there is one in which resistors for suppressing oscillation are formed between the input matching circuit and the output matching circuit of each amplification element to which an input signal is distributed (for example, Patent Document 1). However, the resistance value adjustment amount for suppressing oscillation varies depending on the characteristics variation of individual amplifier elements. For amplifier elements with greatly different characteristics, a separate input / output matching circuit board with different resistance values is prepared. It needs to be replaced.

Japanese Patent No. 3735270

  The problem to be solved by the present invention is to provide a high-frequency amplifier circuit that solves the above-described problems and that can perform adjustment work for suppressing oscillation with high accuracy and in a short time without replacing the input / output matching circuit board. .

  In order to achieve the above object, an RF amplifier circuit according to an embodiment is adjacent to an amplification element divided into a plurality of regions, an input matching circuit having the number of sections of the amplification element, and an output matching circuit having the number of sections. A first resistor group including one or more removable resistors that connect the input matching circuits, and a second resistor group including one or more removable resistors that connect the adjacent output matching circuits And having.

The block block diagram of the high frequency amplifier which concerns on 1st Embodiment. The block block diagram of the high frequency amplifier which concerns on 2nd Embodiment. The equivalent circuit schematic of the amplifier circuit which concerns on the same embodiment. The module external view of the high frequency amplifier which concerns on the same embodiment. The block diagram of the input-output matching circuit board which concerns on the same embodiment. (A) is a top view, (b) is a sectional view. The process figure of air bridge resistance formation concerning the embodiment. The example of arrangement | positioning of the 1st air bridge resistance which concerns on 3rd Embodiment. The example of arrangement | positioning of the 2nd air bridge resistance which concerns on the same embodiment. The relationship between the parallel synthetic resistance value which concerns on the same embodiment, and the number of air bridge resistances. The example of arrangement | positioning of the 3rd air bridge resistance which concerns on the embodiment.

  Hereinafter, embodiments for carrying out the invention will be described in detail with reference to FIGS. 1 to 10.

(First embodiment)
FIG. 1 shows a block configuration of the high-frequency amplifier according to the first embodiment. As shown in FIG. 1, the high-frequency amplifier 1 of this embodiment corresponds to a high-frequency distribution circuit 10 that branches a high-frequency signal input from an input IN into N (N is an integer of 2 or more) signals, and a branched signal. N input matching circuits 11a to 11d (N number is represented by four symbols), amplification element 12 similarly divided into N amplification regions (12a to 12d), N output matching circuits 13a ˜13d and a high frequency synthesis circuit 14 that synthesizes the N amplified signals, and outputs a high frequency signal from the output OUT.

  The high-frequency distribution circuit 10 and the high-frequency synthesis circuit 14 generally use tournament structures, but may use structures using other methods.

  Each input matching circuit 11 includes resistor groups 15a to 15d (for example, between adjacent input matching circuits 11a and 11b) including one or more removable resistors between adjacent input matching circuits (for example, 11a and 11b, 11c and 11d, etc.). The resistor group to be arranged in (5) is connected to 15a).

  Similarly, each output matching circuit 13 is connected between adjacent output matching circuits (for example, 13a and 13b, 13c and 13d, etc.) by resistor groups 16a to 16d including one or more removable resistors.

  Further, the high-frequency distribution circuit 10, the input matching circuit 11, the high-frequency amplification element 12, the output matching circuit 13, and the high-frequency synthesis circuit 14 include bonding means 17a to 17d, 18a to 18d, such as wires or ribbons, for each divided amplification region. Connected at 19a to 19d and 20a to 20d.

  When the input high frequency signals are evenly distributed and synthesized, it is preferable that the number of branches N of the high frequency distribution circuit 10 and the high frequency synthesis circuit 14 is usually a power of 2. Further, the number of branches N is set to an optimum number of branches that is unlikely to cause odd mode oscillation or the like from the simulation result using the S parameter, thereby preventing abnormal oscillation described later.

  Similarly, the input matching circuit 11 and the output matching circuit 13 are also divided into N branches, and the input matching circuits 11a to 11d and the output matching circuits 13a to 13d are connected to the amplification regions 12a to 12d, respectively. For impedance matching, a capacitor, and an inductor (including a strip line).

  The high-frequency amplifying element 12 uses a monolithic FET chip in which a plurality of unit cell FETs composed of several to tens of gate electrodes are arranged in parallel, or a plurality of monolithic FET chips are arranged in parallel. Thus, an amplification region mounted in a hybrid may be formed.

  Normally, the input / output impedances of the amplification regions 12a to 12d can be adjusted by adjusting the values of the resistors, capacitors, and inductors included in each input matching circuit 11 and each output matching circuit 13, thereby suppressing abnormal oscillation. . However, work such as adjusting the length of the bonding wires 17, 18, 19, and 20 and the resistance value connected between the matching circuits is often performed based on personal intuition and know-how. The place depends on the skill. In the worst case in which oscillation cannot be suppressed, the input / output matching circuits 11 and 13 need to be replaced with another one.

  In particular, abnormal oscillation is often caused by an imbalance in amplification characteristics of adjacent amplification regions such as between adjacent FET chips or between adjacent cells of the FET chip. Oscillation suppression resistor groups 15 and 16 including one or more removable resistors are formed between the output matching circuits 13 so that a necessary number of resistors for suppressing oscillation can be removed. The oscillation suppression resistor groups 15 and 16 can consume sneak currents between the adjacent input matching circuits 11 and the adjacent output matching circuits 13 which are the main causes of abnormal oscillation. Then, by measuring the amplification characteristics such as the S parameter while removing the resistors in the resistor groups 15 and 16 one by one, the high frequency amplifier 1 can be adjusted to a stable point where abnormal oscillation can be suppressed.

  Note that the sneak current between the input matching circuits 11 and the output matching circuit 13 is also generated between matching circuits that are not adjacent to each other. However, as a first step, resistance adjustment is performed to suppress oscillation between adjacent matching circuits. It is desirable. In addition, it is preferable that the static characteristics (threshold value Vth, mutual conductance gm, etc.) of 12a to 12d in the amplification region are measured in advance and the resistance adjustment is performed from the point where the characteristic variation is large. By performing such adjustment, a stable amplification characteristic can be obtained.

  Therefore, according to the first embodiment, the unbalance between the amplification regions (amplifying elements) can be eliminated by mechanically removing the plurality of oscillation suppression resistance groups arranged between the input / output matching circuits. Therefore, it is possible to flexibly cope with oscillation suppression.

(Second Embodiment)
In the present embodiment, the configuration of the high-frequency amplifier circuit that further embodies the first embodiment and divides and amplifies the high-frequency signal into four parts and then outputs the synthesized signal will be described.

  FIG. 2 is a block configuration of the high-frequency amplifier according to this embodiment. The high-frequency amplifier 2 of this embodiment includes a four-branch high-frequency distribution circuit board 20 formed on a dielectric substrate, and an input matching circuit board 21 in which four capacitor regions (21a to 21d) are formed on the same dielectric substrate. Amplifying element 22 divided into four amplifying regions (22a to 22d), output matching circuit substrate 23 in which four capacitor regions are formed on the same dielectric substrate, and four high frequency signals are combined into one output signal. The high-frequency synthesis circuit board 24 is formed on a dielectric substrate, and the respective signal paths are connected by bonding wires 27, 28, 29, and 30. The amplifying element 22 is assumed to be an FET, but may be an amplifying element such as a bipolar transistor.

  In the input matching circuit 21, resistor groups 25a to 25c including one or more removable resistors are connected between the capacitor regions 21a to 21d, and the structure of the resistor groups 25a to 25c has an air bridge structure.

  Similarly to the input matching circuit 21, in the output matching circuit 23, resistor groups 26a to 26c including one or more removable resistors are connected between the capacitor regions 23a to 23d, and the resistor groups 26a to 26c are connected to each other. The structure has an air bridge structure. These resistance groups 25 and 26 of the air bridge structure can be removed. As a method for removing the resistance, for example, mechanical removal with a fine needle such as a probe, or burning by laser irradiation or the like can be considered.

  A flow of the high-frequency signal branched into four from the input terminal IN will be described. An input matching circuit is formed by the bonding wire 27a, the capacitor region 21a, and the bonding wire 28a, and after passing through this input matching circuit, the amplification region 22a Input to the gate. The high frequency signal output from the source of the amplification region 22a passes through the output matching circuit formed by the bonding wire 29a, the capacitor region 23a, and the bonding wire 30a, and is input to one of the four ports of the high frequency synthesis circuit 24. The

  FIG. 3 shows the configuration of the above high-frequency amplifier 2 by an equivalent circuit. Here, for example, an input matching circuit 31a formed by the bonding wire 27a, the capacitor region 21a and the bonding wire 28a, and an output matching circuit 32a formed by the bonding wire 29a, the capacitor region 23a and the bonding wire 30a are specified. Further, the removable resistor groups 25a to 25c and 26a to 26c are shown as variable resistors.

  FIG. 4 shows an external view of a module on which the high-frequency amplifier circuit shown in FIG. 2 is mounted. The module 4 includes a high-frequency distribution circuit 20, an input matching circuit 21, an amplification element 22, an output matching circuit 23, and a high-frequency synthesis circuit 24 (not shown) on a heat-dissipating metal base 40 such as gold-plated Cu (copper). The input IN and output OUT are connected to feedthrough type input / output terminals 41 and 42, respectively. The amplifying element 22 is hermetically sealed by a frame 43 and a lid 44 to ensure its reliability. In order to fix the package to a housing or the like, a fixing flange 45 is configured to be integrated with the metal base 40 for heat dissipation. By fixing the fixing flange 45 to the housing with screws, high-frequency ground and heat dissipation are ensured. The high-frequency amplifier configured in this way is called an internal matching power amplifier.

  FIG. 5 shows a top view (a) of the input matching circuit board 21 and a cross-sectional view (b) along A-A ′ shown in FIG. 2. In addition, in order to show the resistance cross section of an air bridge structure, it has illustrated from the direction rotated 90 degree | times with FIG. Further, the structure of the output matching circuit board 23 is exactly the same except that the resistance value of the bridge structure formed is different. Therefore, the input matching circuit board 21 will be described.

  In the input matching circuit substrate 21, a lower metal layer 51 is formed of a metal such as Au on the bottom surface of a dielectric substrate 50 such as ceramic, and the lower metal layer 51 serves as a high-frequency ground. Upper metal layers 52 a to 52 d for forming capacitor regions 21 a to 21 d are formed on the upper surface of the dielectric substrate 50 by being divided by the number of amplification regions (N = 4) of the amplification element 22. 21a to 21d are formed.

  Further, resistors 25a to 25c having an air bridge structure are formed so as to bridge between the upper metal layers 52a to 52d (hereinafter referred to as air bridge resistors).

  In FIG. 5B, an adhesive layer 53 is shown as a layer structure for adhering the upper metal layers 52a to 52d and the air bridge resistors 25a to 25c. By adjusting the height of the gap formed by the resistors 25a to 25c and the dielectric substrate 50, the air bridge resistor 25 is easily removed mechanically, and the parasitic capacitance of the air bridge resistor 25 is reduced. However, the adhesive layer 53 is not essential and is adopted as necessary.

  When the resistance layer is formed in close contact with a high dielectric constant substrate such as alumina as in the prior art, a capacitance with a high frequency ground is generated. If this parasitic capacitance is present, the capacitance value changes every time the resistor is removed in order to stop abnormal oscillation. Therefore, the impedance matching values of the input matching circuits 31a to 31d and the output matching circuits 32a to 32d also change. Not good.

  Therefore, if the air bridge resistor of the present embodiment is used, the capacitance with the high frequency ground can be almost ignored, so that the impedance matching values of the input matching circuits 31a to 31d and the output matching circuits 32a to 32d are not changed, and the accuracy is high. Abnormal oscillation can be controlled.

  Next, a process for forming the air bridge resistor 25 will be described with reference to FIG. Here, it is assumed that the upper metal layer 52 and the lower metal layer 51 are already formed on the dielectric substrate 50 on the input matching circuit board 21 and the output matching circuit board 23.

  In FIG. 6A, patterning is performed by the first resist 61 in a region where the air bridge resistors 25 and 26 between the upper metal layers 52a to 52d are formed. Further, in FIG. 6B, patterning is performed by the second resist 62 in a region where the air bridge resistance of the upper metal layers 52a to 52d is not formed. The dotted line in the second resist 62 indicates that the second resist 62 is formed in the depth direction with respect to the air bridge resistors 25 and 26 to be formed. Since the second resist 62 uses a technique such as lift-off as will be described later, a resist having a relatively thick film and having a sharp edge can be used.

  In FIG. 6C, a thin film resistance layer 63 is formed on the entire surface using a technique such as vapor deposition of a metal such as NiCr.

  In FIG. 6D, the second resist 62 is removed using a technique such as lift-off. At this time, a portion of the resistance layer 63 where the air bridge resistors 25 and 26 are not formed is removed together with the second resist 62 by lift-off. When the lift-off method is used, the first resist 61 needs to be a resist that does not dissolve during the lift-off.

  In FIG. 6E, the first resist 61 is removed using a technique such as ashing. By adopting such a formation process, the air bridge resistors 25a to 25c (26a to 26c) can be formed on the dielectric substrate 50 such as ceramic. In addition, when the upper metal layers 52a to 52d and the resistance layer 63 cannot be directly bonded, a process of forming the adhesive layer 53 in a necessary portion is added.

  As described above, according to the second embodiment, since the resistance layer of the air bridge structure can be formed on the dielectric substrate such as ceramic, it is easy to mechanically remove these resistance layers. Abnormal oscillation can be suppressed with high accuracy.

(Third embodiment)
In this embodiment, an arrangement example of air bridge resistors for suppressing abnormal oscillation will be described. FIG. 7 shows a first arrangement example. Of the capacitor regions 21a to 21d (23a to 23d) formed on the input matching circuit substrate 21 or the output matching circuit substrate 23, the adjacent capacitor regions are described as 70a and 70b. A plurality of air bridge resistors are arranged as a resistor group between the capacitor regions 70a and 70b, and all of the five air bridge resistors 71 to 75 illustrated here have the same resistance value. As shown in FIG. 6, when the resistance layer 63 is formed by normal vapor deposition or the like, the sheet resistance values are substantially equal. Therefore, when the resistance values of the air bridge resistors 71 to 75 are equal, The bridge resistors 71 to 75 have the same size.

  In this configuration, the power consumed by the air bridge resistor can be adjusted by the number of air bridge resistors (an integral multiple conductance value) with respect to the unbalanced voltage ΔV generated between the capacitor regions 70a and 70b. The unbalanced voltage ΔV is caused by variations in the threshold value (Vth) and mutual conductance (gm) of each amplification region.

  A second arrangement example is shown in FIG. In this arrangement example, by removing the air bridge resistors 81 to 85 in order from the right, the increase in the parallel combined resistance value can be made equal.

  That is, assuming that the combined resistance value of the air bridge resistors 81 to 85 is Rt, the resistance value of the air bridge resistor 81 is 5 Rt, the resistance value of the air bridge resistor 82 is 20 Rt, the resistance value of the air bridge resistor 83 is 12 Rt, and the air bridge resistor An air bridge resistor group having a resistance value 84 of 6 Rt and a resistance value of the air bridge resistor 85 of 2 Rt is arranged.

  In this example, when no air bridge resistor is removed, the combined resistance value of all the air bridge resistors 81 to 85 is Rt. When the air bridge resistor 85 is removed, the combined resistance value is 2Rt. Next, when the air bridge resistor 84 is removed, the combined resistance value becomes 3Rt. Further, when the air bridge resistor 83 is removed, the combined resistance value is 4 Rt, and when the air bridge resistor 82 is removed, the combined resistance value is 5 Rt.

  FIG. 9 shows this state in a graph. The horizontal axis represents the number of parallel resistors, and the vertical axis represents the change in the parallel combined resistance value normalized by the parallel combined resistance value when no air bridge resistor is removed. Thereby, it turns out that parallel synthetic | combination resistance value changes linearly by removing the air bridge resistors 81-85 in order.

  In order to suppress abnormal oscillation, the parallel combined resistance value between the capacitor regions 70a and 70b is larger than the resistance of the input impedance or output impedance of each amplification region, and the impedance wraps around between adjacent high frequency distribution circuits or between high frequency synthesis circuits. Since it is effective to make the resistance value smaller than the resistance value of the resistor, by removing the air bridge resistor in order within the resistance value range of these impedances, the optimum resistance value is set for oscillation suppression. Is possible. In each resistor group arranged between the matching circuits, the resistance value adjustment range, the number of adjustment resistors, and the resistance value are set by simulation.

  FIG. 10 is a third arrangement example of air bridge resistors. In this arrangement example, the conductance of the air bridge resistors 101 to 105 is increased by a power of 2 as the resistor arranged on the left with respect to the air bridge resistor 105 serving as a reference. That is, the conductance of the air bridge resistor 104 is twice that of the air bridge resistor 105, the conductance value of the air bridge resistor 103 is four times, the conductance of the air bridge resistor 102 is eight times, and the conductance of the air bridge resistor 101 is sixteen times. It has become.

  In such an arrangement example, if the conductance value to be adjusted to suppress oscillation is known, conductance can be set in a wide range of 1 to 31 steps.

  In the input matching circuit board 21 or the output matching circuit board 23, the resistor arrangement between the individual capacitor regions 70a and 70b can take any combination of the arrangement examples of the air bridge resistors as described above. .

  In the present embodiment, the number of resistors constituting the resistor group is described as five. However, the number of resistors may be any number of one or more. Resistances that cannot be removed may be included in the resistance group.

  As described above, according to the present embodiment, in the high frequency amplifier such as the internal matching FET amplifier, the abnormal oscillation of the high frequency amplifier is suppressed by mechanically removing the air bridge resistor connecting the matching circuits. Is possible. Since the removable resistor is arranged, it is not necessary to replace the matching circuit board, and oscillation can be suppressed in a state where the high frequency amplifier circuit is mounted in the module.

  In addition, since the resistance value of the resistor group is arranged according to a predetermined rule, a resistance value necessary for suppressing the oscillation can be selected, so that the oscillation can be suppressed with high accuracy and high stability. Also, the adjustment time can be shortened.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... High frequency distribution circuit 11 ... Input matching circuit 12 ... Amplifying element 13 ... Output matching circuit 14 ... High frequency synthesis circuit 15, 16 ... Resistor groups 17, 18, 19, 20 ... Bonding means 20 ... High frequency distribution circuit board 21 ... Input matching Circuit boards 21a, 21b, 21c, 21d ... capacitor region 22 ... FET
23 ... Output matching circuit boards 23a, 23b, 23c, 23d ... Capacitor region 24 ... High frequency synthesis circuit boards 25, 26 ... Air bridge resistor groups 27, 28, 29, 30 ... Bonding wires

Claims (7)

An amplifying element divided into a plurality of regions;
An input matching circuit of the number of sections of the amplifying element;
The number of output matching circuits; and
A first group of resistors including one or more removable resistors connecting adjacent input matching circuits;
A second group of resistors including one or more removable resistors connecting between the adjacent output matching circuits;
A high frequency amplifier.   The high-frequency amplifier according to claim 1, wherein the first and second resistor groups include an air bridge resistor having an air bridge structure.   3. The high frequency amplifier according to claim 2, wherein the plurality of input matching circuits and the plurality of output matching circuits are formed on the same dielectric substrate.   The resistance value of the air bridge resistor is set so that the amount of change in the combined resistance value increases approximately linearly every time the air bridge resistor in the first and second resistor groups is removed. 3. The high frequency amplifier according to 3.   4. The high frequency amplifier according to claim 3, wherein the air bridge resistors in the first and second resistor groups all have equal resistance values.   4. The high-frequency amplifier according to claim 3, wherein the plurality of air bridge resistors in the first and second resistor groups are set to conductance values that sequentially become powers of 2 with respect to a basic conductance value.   The air bridge resistor is formed on the dielectric substrate by forming a first resist layer in a region where the air bridge resistor is formed and forming a second resist layer in a region where the air bridge resistor is not formed. 4. The high-frequency amplifier according to claim 3, wherein a resistance layer is formed on the entire surface of the dielectric substrate, the resistance layer on the second resist layer is removed together with the second resist, and then the first resist layer is removed. .

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