JP2011044962A - Thin-film balun - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and thin-film balun that maintains various required balun characteristics. <P>SOLUTION: The thin-film balun 1 includes: an unbalanced transmission line UL; a balanced transmission line BL facing and magnetically coupled to the unbalanced transmission line UL; a capacitor electrode DE1 facing a part of the unbalanced transmission line UL facing the balanced transmission line BL and constituting a capacitor D1: and an unbalanced terminal UT connected to the unbalanced transmission line UL and the capacitor electrode DE1. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a balun (balun transformer) that performs unbalanced-balanced signal conversion, and more particularly to a thin film balun formed by a thin film process that is advantageous for miniaturization and thinning.

  The wireless communication device includes various high frequency elements such as an antenna, a filter, an RF switch, a power amplifier, an RF-IC, and a balun. Among these, resonant elements such as antennas and filters handle unbalanced signals based on the ground potential (perform signal transmission), but RF-ICs that generate and process high-frequency signals are balanced types. Therefore, when the two are electromagnetically connected, a balun that functions as an unbalanced-balanced converter is used.

  Recently, as a balun used in mobile communication devices such as mobile phones and mobile terminals, wireless LAN devices, and the like, further downsizing and thinning are desired. As such a balun, an electromagnetic coupling is formed by an unbalanced transmission line and a balanced transmission line arranged opposite to each other, one end of the unbalanced transmission line is connected to an unbalanced terminal, and the other end is connected via a capacitor. A device having a configuration connected to a ground terminal (Patent Document 1) has been proposed.

JP 2006-270444 A

By the way, as a passing characteristic of the thin film balun, its resonance frequency is expressed by the following formula (1)
fr = 1 / {2π (L · C) ^1/2 } (1),
It is represented by Here, fr represents the resonance frequency, L (L component) represents the equivalent inductance of the resonance circuit formed by the unbalanced transmission line and the balanced transmission line portion, and C (C component) is It shows the same capacitance.

  However, in order to reduce the size and thickness of the balun, the number of turns and the line length of the coils forming the unbalanced transmission line and the balanced transmission line are inevitably reduced, so that the inductance L of the resonance circuit is lowered. As is clear from Equation (1), the resonance frequency fr (passband frequency) is increased. Usually, the pass characteristics (attenuation characteristics of a predetermined frequency) of the frequency of a balun used in wireless communication and the like are determined from the configuration, standards, specifications, etc. of the communication equipment and system in which the balun is installed. It is particularly important as a property. Specifically, for example, a numerical value such that the peak value of the resonance frequency fr is 2400 to 2500 MHz (2.4 GHz band) is specified as the pass characteristic, and the specification design is made so that the attenuation in the frequency band is sufficiently low. The However, as described above, when the resonance frequency fr is increased by reducing the size and thickness of the balun, it is difficult to satisfy the required specifications with the configuration of the chip-type balun described in Patent Document 1. .

  Therefore, from the above equation (1), the resonance frequency fr can be prevented from increasing by increasing the capacitance C of the resonance circuit, but according to the knowledge of the present inventor, the balun described in the above-mentioned Patent Document 1 is used. If the capacitor is provided and the capacitance C is simply increased, a desired pass characteristic for the input signal and a desired balance characteristic for the output signal (amplitude difference or phase difference of the output signal) cannot be obtained. It may be difficult to meet the required specifications.

  Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a thin film balun that can be reduced in size and thickness while maintaining the required characteristics of the balun.

  In order to solve the above problems, a thin film balun according to the present invention includes an unbalanced transmission line, a balanced transmission line facing the unbalanced transmission line and electromagnetically coupled, and a part of the unbalanced transmission line facing the balanced transmission line. The capacitor electrode which opposes and comprises a capacitor | condenser, and the unbalanced transmission line and the unbalanced terminal connected to the capacitor electrode are provided.

  In such a configuration, since the capacitor is introduced into the resonance circuit of the thin film balun, the resonance frequency of the thin film balun is shifted to the low frequency side. Therefore, the increase in the resonance frequency accompanying the downsizing of the thin film balun is suppressed. It was also found that the balance characteristics of the thin film balun can be improved by providing the capacitor electrode so as to face a part of the unbalanced transmission line facing the balanced transmission line of the capacitor.

  The details of the mechanism of action are still unknown, but are estimated as follows. Part of the unbalanced transmission line facing the balanced transmission line of the capacitor is a part where electromagnetic coupling (coupling) with the balanced transmission line is dominant, and the capacitor electrode is opposed to this part to constitute the capacitor. This can significantly change the coupling state of the unbalanced transmission line with the balanced transmission line. That is, by introducing a capacitor (capacitance) at a predetermined position of the unbalanced transmission line, the part itself contributing to the coupling with the balanced transmission line in the unbalanced transmission line can be changed. Further, by introducing the capacitor in this way, the characteristic impedance of the entire transmission line can be changed. And it is estimated that the balance characteristic of a thin film balun is suitably improved due to the change of the site | part which contributes to this coupling, and the change of characteristic impedance. However, the action is not limited to this.

  The above-described configuration of the present invention includes a case where the other capacitor electrode connected to the unbalanced transmission line is disposed between a part of the unbalanced transmission line and the capacitor electrode facing the unbalanced transmission line. It is more useful that a part of the unbalanced transmission line also serves as the other capacitor electrode. This eliminates the need for a new layer for disposing the other capacitor electrode, leading to a reduction in the number of man-hours in the manufacturing process, thereby improving productivity and simplifying process management.

  Moreover, in order to solve the said subject, the thin film balun of this invention is opposite to each of the unbalanced transmission line which has a 1st line part and a 2nd line part, and a 1st line part and a 2nd line part. And a balanced transmission line having a third line portion and a fourth line portion that are electromagnetically coupled to each other and a part of the second line portion that faces the fourth line portion, and constitutes a capacitor And an unbalanced terminal connected to the first line portion and the capacitor electrode. Even if it does in this way, the effect | action similar to having mentioned above is show | played.

  Preferably, it further includes a capacitor electrode that constitutes a capacitor, facing a part of the first line portion that faces the third line portion, and the unbalanced terminal includes the first line portion and the second line portion. The capacitor electrode facing a part of the line part and the capacitor electrode facing a part of the first line part are connected. With such a configuration, in addition to the coupling between the fourth line portion and the second line portion, the portion contributing to the coupling between the third line portion and the first line portion can change. Therefore, it is presumed that the two couplings can be adjusted by such a configuration, which further contributes to the improvement of the equilibrium characteristics of the thin film balun. However, the action is not limited to this.

  Furthermore, in order to solve the above problems, the thin film balun of the present invention includes an unbalanced terminal, an unbalanced circuit having one end connected to the unbalanced terminal and the other end being an open end, and a balanced circuit electromagnetically coupled to the unbalanced circuit. The capacitor is connected to a part of the unbalanced circuit excluding the open end, and the capacitor is also connected to the unbalanced terminal.

  In such a configuration, since a capacitor is introduced into the resonance circuit of the thin film balun, the resonance frequency of the thin film balun is shifted to a lower frequency side, so that an increase in the resonance frequency associated with the miniaturization of the thin film balun is suppressed. The Also, the area inside the open end of the unbalanced transmission line is a part where electromagnetic coupling (coupling) with the balanced transmission line is relatively stronger than the open end, and the capacitor electrode is opposed to this part. By configuring the capacitor, the part contributing to the coupling with the balanced transmission line in the unbalanced transmission line can be changed. Furthermore, the characteristic impedance of the entire transmission line can be changed by introducing a capacitor. Thus, it is presumed that the change in site and the change in characteristic impedance contributing to the coupling contribute to the improvement of the equilibrium characteristics of the thin film balun. However, the action is not limited to this.

  According to the present invention, by introducing a capacitor between a part of the unbalanced transmission line facing the balanced transmission line and the unbalanced terminal, the high-frequency of the thin film balun associated with miniaturization is suppressed, and the thin film balun is suppressed. Thus, it is possible to further reduce the size and thickness of the thin film balun.

It is an equivalent circuit diagram which shows the structure of one Embodiment of the thin film balun of this invention. It is a vertical sectional view showing the configuration of an embodiment of a thin film balun. It is a horizontal sectional view in wiring layer M0 of thin film balun 1A. It is a horizontal sectional view in wiring layer M1 of thin film balun 1A. It is a horizontal sectional view in wiring layer M2 of thin film balun 1A. It is a horizontal sectional view in wiring layer M3 of thin film balun 1A. It is a horizontal sectional view in wiring layer M0 of thin film balun 1B. It is a graph which shows the evaluation result of a passage characteristic. It is a horizontal sectional view in wiring layer M0 of thin film balun 1C. It is a horizontal sectional view in wiring layer M0 of thin film balun 1D. It is a horizontal sectional view in wiring layer M0 of thin film balun 1E. It is a horizontal sectional view in wiring layer M0 of thin film balun 1F. It is a graph which shows the evaluation result of a passage characteristic. It is a graph which shows the evaluation result of phase difference. It is a graph which shows the evaluation result of an amplitude difference. It is an equivalent circuit diagram which shows the structure of other embodiment of the thin film balun of this invention. It is a horizontal sectional view in wiring layer M0 of thin film balun 2A. It is a horizontal sectional view in wiring layer M0 of thin film balun 2B. It is a graph which shows the evaluation result of a passage characteristic. It is a graph which shows the evaluation result of phase difference. It is a graph which shows the evaluation result of an amplitude difference.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, positional relationships such as up, down, left and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention only to the embodiments. Further, the present invention can be variously modified without departing from the gist thereof.

(First embodiment)
FIG. 1 is an equivalent circuit diagram showing the configuration of the first embodiment according to the thin film balun of the present invention. The thin film balun 1 includes an unbalanced transmission line (unbalanced circuit) UL in which a line portion L1 (first line portion) and a line portion L2 (second line portion) are connected in series, and a line portion L3 (third Line portion) and a line portion L4 (fourth line portion) and a balanced transmission line (balanced circuit) BL connected in series. The line portion L1, the line portion L3, and the line portion L2, the line portion. The portions L4 form electromagnetic couplings.

  In the thin film balun 1, the other end of the coupling end of the line portion L1 with the line portion L2 is connected to the unbalanced terminal UT. Further, the other end of the coupling end with the line portion L1 in the line portion L2 is an open end, and a part other than the open end is connected to the unbalanced terminal UT via the capacitor D1. Further, the other ends of the coupling portions in the line portion L3 and the line portion L4 are connected to the balanced terminal BT1 and the balanced terminal BT2. Furthermore, the coupling end of the line portion L3 and the line portion L4 is connected to the ground terminal G.

  The lengths of the line portions L1 to L4 described above vary depending on the specifications of the thin film balun 1, and may be set to be a 1/4 wavelength (λ / 4) resonator circuit of a transmission signal to be converted, for example. it can. In addition, the shape of the line portions L1 to L4 can be any shape as long as the above-described electromagnetic coupling is formed, for example, a spiral shape (coil shape), a meandering shape, a linear shape, a curved shape, or the like. Is mentioned.

  The basic operation of the thin film balun 1 will be described below with reference to FIG. When an unbalanced signal is input to the unbalanced terminal UT, the unbalanced signal propagates through the line portion L1 and the line portion L2. Then, the line portion L1 and the line portion L3 are electromagnetically coupled (first electromagnetic coupling), and the line portion L2 and the line portion L4 are electromagnetically coupled (second electromagnetic coupling), whereby the input unbalanced signal is input. Is converted into two balanced signals having the same frequency as that of the unbalanced signal and a phase different by 180 ° (π), and these two balanced signals are output from the balanced terminals BT1 and BT2, respectively. Conversely, when two balanced signals having the same magnitude and a phase difference of 180 ° and having a predetermined frequency are input to the balanced terminals BT1 and BT2, an unbalanced signal having the same frequency as the balanced signal is output from the unbalanced terminal UT. Is done.

  Next, the wiring structure in one embodiment of the thin film balun will be described. FIG. 2 is a vertical sectional view schematically showing the wiring structure of the thin film balun 1. As shown in FIG. 2, wiring layers M0, M1, M2, and M3 are formed in this order from the insulating substrate 100 side such as alumina. For example, the capacitor electrode DE1 described above is formed by the wiring layer M0, the unbalanced transmission line UL is formed by the wiring layer M1, the balanced transmission line BL is formed by the wiring layer M2, and the balanced transmission line BL and the unbalanced transmission line UL. A connection wiring for connecting the line portions inside is formed by the wiring layer M3. Dielectric layers 101 to 105 are formed between the wirings in the same wiring layer and between different wiring layers. The dielectric layer 102 between the wiring layer M0 and the wiring layer M1 in which the capacitor D is formed, and between the wiring layer M1 and the wiring layer M2 in which electromagnetic coupling between the unbalanced transmission line UL and the balanced transmission line BL is formed. For example, silicon nitride is used for the dielectric layer 104. For example, alumina is used as the dielectric layers 101 and 103 covering the wiring layer M0 and the wiring layer M1. Further, for example, polyimide is used as the dielectric layer 105 covering the wiring layers M2 and M3. The materials of these layers are not limited to those described above, and may be selected as appropriate, not only inorganic insulators such as silicon nitride, alumina, and silica but also organic insulators such as polyimide and epoxy resin. The unbalanced terminal UT, the balanced terminals BT1 and BT2, and the ground terminal G are formed so as to penetrate all the dielectric layers. Thus, the thin film balun 1 is composed of a thin film multilayer structure formed on the insulating substrate 100.

  As shown in FIG. 2, in the present embodiment, the capacitor D described above includes a wiring layer M1 including the unbalanced transmission line UL, and a capacitor electrode DE1 disposed to face the wiring layer M1 via the dielectric layer 102. It is formed between the wiring layer M0.

Example 1A
Next, the patterns of the wiring layers M0, M1, M2, and M3 in one embodiment of the thin film balun will be described in detail. In the following embodiments, coil portions are used as the line portions L1 to L4.

  3 to 6 are horizontal sectional views schematically showing each wiring layer in the thin film balun 1A. As shown in FIGS. 3 to 6, unbalanced terminals UT, balanced terminals BT1 and BT2, and a ground terminal G are formed in all the wiring layers M0 to M3, and the terminals UT, BT1, BT2, and so on are formed. G is electrically connected between different layers via through holes P. In addition, in all the through holes P shown in FIGS. 3 to 6, metal conductors for electrically connecting the upper and lower layers are formed by plating. Hereinafter, the configuration of each wiring layer will be described in detail.

  As shown in FIG. 3, in the wiring layer M0 on the insulating substrate 100, the capacitor electrode DE1 of the capacitor D1 is formed at a position facing a part of the coil portion C2 of the wiring layer M1. The capacitor electrode DE1 is connected to the unbalanced terminal UT. The capacitor electrode DE1 of the capacitor D1 is disposed so as to face the coil conductor 12 in the first row from the left of the coil portion C2 in plan view.

  Further, as shown in FIG. 4, the wiring layer M1 is formed with a coil part C1 (first line part) and a coil part C2 (second line part) that constitute the unbalanced transmission line UL adjacent to each other. Yes. Each coil part C1, C2 comprises what is corresponded to a 1/4 wavelength ((lambda) / 4) resonator. The outer end portion 11a of the coil conductor 11 constituting the coil portion C1 is connected to the unbalanced terminal UT, and the inner end portion 11b of the coil conductor 11 is connected to the through hole P. On the other hand, the inner end portion 12b of the coil conductor 12 constituting the coil portion C2 is connected to the through hole P, and the outer end portion 12a (open end) of the coil conductor 12 is opened. A part of the coil conductor 12 excluding the outer end 12a of the coil part C2 also serves as the capacitor electrode of the capacitor D1, and faces the capacitor electrode DE1 of the wiring layer M0. Further, as shown in FIG. 4, the width of the coil conductor 12 constituting the coil portion C2 is wider than the width of the coil conductor 11 constituting the coil portion C1. This is because, as a result of diligent research by the present inventor, when the capacitor D1 is inserted so that a part of the coil portion C2 also serves as an electrode of the capacitor, the width of the coil conductor 12 is increased compared to the width of the coil conductor 11. This is because it was confirmed that better pass characteristics and equilibrium characteristics were obtained. However, the width and the number of turns of the coil conductor 12 and the coil conductor 11 are not limited, and the width and the number of turns of the coil conductor 12 and the coil conductor 11 may be the same or different.

  Furthermore, as shown in FIG. 5, in the wiring layer M2, a coil part C3 (third line part) and a coil part C4 (fourth line part) constituting the balanced transmission line BL are formed adjacent to each other. ing. Each coil part C3, C4 comprises what is corresponded to a 1/4 wavelength ((lambda) / 4) resonator similarly to coil part C1, C2. These coil portions C3 and C4 of the balanced transmission line BL are respectively arranged to face the coil portions C1 and C2 of the unbalanced transmission line UL, and electromagnetically couple at the opposed portions to constitute a coupler. The outer end portion 21a of the coil conductor 21 constituting the coil portion C3 is connected to the balanced terminal BT1, and the inner end portion 21b of the coil conductor 21 is connected to the through hole P. On the other hand, the outer end 22a of the coil conductor 22 constituting the coil portion C4 is connected to the balanced terminal BT2, and the inner end 22b of the coil conductor 22 is connected to the through hole P. As shown in FIG. 5, the width of the coil conductor 22 is wider than the width of the coil conductor 21, and the number of turns of the coil conductor 22 is smaller than that of the coil conductor 21. In the same manner as described above, when the capacitor D1 is inserted so that a part of the coil portion C2 also serves as an electrode of the capacitor, the coil conductors 21 and 22 are as described above. This is because it has been confirmed that excellent pass characteristics and balance characteristics can be obtained by setting the number of windings and the width. However, the width and the number of turns of the coil conductor 22 and the coil conductor 21 are not limited, and the width and the number of turns of the coil conductor 22 and the coil conductor 21 may be the same or different.

  Then, as shown in FIG. 6, in the wiring layer M3, a wiring 31 for connecting the coil part C3 and the coil part C4 to the ground terminal G and a wiring 32 for connecting the coil part C1 and the coil part C2 are provided. Is formed. The wiring 31 is a branch wiring formed so as to connect the two through holes P and the ground terminal G. The wiring 31 is connected to the end portion 21b of the coil conductor 21 and the end portion 22b of the coil conductor 22 formed in the wiring layer M2 through two through holes P. On the other hand, the wiring 32 is connected to the end portion 11b of the coil conductor 11 and the end portion 12b of the coil conductor 12 formed in the wiring layer M1 through the through hole P.

  As described above, in this embodiment, the two coil portions C1 and C2 constituting the unbalanced transmission line are formed in the wiring layer M1 which is one layer, and the wiring layer M2 which is another layer adjacent thereto is balanced. Two coil portions C3 and C4 constituting the transmission line are formed, and the coil portions C1 and C2 are connected to a wiring layer M3 which is another layer opposite to the wiring layer M1 adjacent to the wiring layer M2. The wiring 32 and the wiring 31 that connects the coil portions C3 and C4 are formed, and the coil conductor 12 in the coil portion C2 is connected to the wiring layer M0 on the opposite side of the wiring layer M2 adjacent to the wiring layer M1. A thin film balun 1A constituting the equivalent circuit shown in FIG. 1 is obtained by the multilayer wiring structure in which the capacitor electrode DE1 for constituting the capacitor D1 is formed so as to face a part of the thin film balun.

(Example 1B)
FIG. 7 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 1B of Example 1B of the present invention. Configurations other than the wiring layer M0 are the same as in Example 1A. In the thin film balun 1B shown in FIG. 7, the length of the capacitor electrode DE1 (substantially the length of the portion that contributes as the capacitor electrode) is half that of Example 1A. Thus, in the thin film balun shown in Example 1B, the capacitance introduced into the resonance circuit of the thin film balun is set to half that of Example 1A.

(Characteristic evaluation)
For the thin film baluns 1A and 1B described above, pass characteristics (insertion loss) were obtained by simulation. The evaluation target frequency (resonance frequency fr) of the transmission signal was set to 2400 to 2500 MHz. FIG. 8 is a diagram illustrating evaluation results of pass characteristics. In each figure, curves E1A and E1B show the evaluation results of the thin film baluns 1A and 1B, respectively. A curve R0 in FIG. 8 shows the evaluation result of the thin film balun of the comparative example that does not include the capacitor electrode DE1. The pass characteristic indicates how much the signal is allowed to pass without being lost in the evaluation target frequency region, and 0 dB is an ideal pass characteristic in the evaluation target frequency region.

  From the results shown in FIG. 8, it is confirmed that the thin film baluns 1A and 1B of the present example including the capacitor D1 are shifted in the resonance frequency to the low frequency side as compared with the balun of the comparative example not including the capacitor. It was. Furthermore, it was confirmed that the shift amount is influenced by the capacitance of the capacitor D1 to be introduced.

(Example 1C)
FIG. 9 is a horizontal cross-sectional view schematically showing the wiring layer M0 in the thin film balun 1C of Example 1C of the present invention. Configurations other than the wiring layer M0 are the same as in Example 1A. In the thin film balun 1C shown in FIG. 9, the capacitor electrode DE1 is arranged to extend in the vertical direction so as to face the second row of coil conductors 12 from the left of the coil portion C2 in plan view. The area of the capacitor electrode DE1 in the part facing the coil part C2 (substantially contributing area as a capacitor electrode) is set to be the same as that of the example 1A.

(Example 1D)
FIG. 10 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 1D of Example 1D of the present invention. Configurations other than the wiring layer M0 are the same as in Example 1A. In the thin film balun 1D shown in FIG. 10, the capacitor electrode DE1 is arranged extending in the left-right direction so as to face the first row of coil conductors 12 from below the coil portion C2 in plan view. The area of the capacitor electrode DE1 in the part facing the coil part C2 (substantially contributing area as a capacitor electrode) is set to be the same as that of the example 1A.

(Example 1E)
FIG. 11 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 1E of Example 1E of the present invention. Configurations other than the wiring layer M0 are the same as in Example 1A. In the thin film balun 1E shown in FIG. 11, the capacitor electrode DE1 is arranged to extend in the vertical direction so as to face the second row of coil conductors 12 from the right of the coil portion C2 in plan view. The area of the capacitor electrode DE1 in the part facing the coil part C2 (substantially contributing area as a capacitor electrode) is set to be the same as that of the example 1A.

(Example 1F)
FIG. 12 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 1F of Example 1F of the present invention. Configurations other than the wiring layer M0 are the same as in Example 1A. In the thin film balun 1F shown in FIG. 12, the capacitor electrode DE1 is arranged to extend in the vertical direction so as to face the open end portion of the coil conductor 12 constituting the coil portion C2 in plan view. The area of the capacitor electrode DE1 in the part facing the coil part C2 (substantially contributing area as a capacitor electrode) is set to be the same as that of the example 1A.

(Characteristic evaluation)
With respect to the thin film baluns 1C to 1F described above, pass characteristics (insertion loss) and balance characteristics (phase difference and amplitude difference of balanced signals) were obtained by simulation. The evaluation target frequency (resonance frequency fr) of the transmission signal was set to 2400 to 2500 MHz. FIG. 13 is a diagram illustrating the evaluation result of the pass characteristics, FIG. 14 is a diagram illustrating the evaluation result of the phase difference, and FIG. 15 is a diagram illustrating the evaluation result of the amplitude difference. In each figure, curves E1A and E1C to E1F show the evaluation results of thin film baluns 1A and 1C to 1F, respectively.

  Since the phase difference is the phase difference between the two balanced signals output from the balanced terminal BT1 and the balanced terminal BT2, 180 deg is a more ideal phase balance. Since the amplitude difference is an amplitude difference between two balanced signals output from the balanced terminal BT1 and the balanced terminal BT2, 0 dB is a more ideal output balance.

  From these results, it was confirmed that the thin film baluns of Examples 1A and 1C to 1F maintained excellent characteristics in both pass characteristics and equilibrium characteristics. Further, among the embodiments, the thin film baluns 1A and 1C to 1E in which the capacitor electrode DE1 is opposed to a portion other than the open end of the coil conductor 12 are compared with the thin film balun 1F in which the capacitor electrode DE1 is opposed to the open end of the coil portion C2. Thus, it was confirmed that the balance characteristic is excellent.

(Second Embodiment)
FIG. 16 is an equivalent circuit diagram showing the configuration of the second embodiment according to the thin film balun of the present invention. In the thin film balun 2 of the second embodiment, in addition to the capacitor D1 being introduced between the unbalanced terminal UT and the line portion L2, the capacitor D2 is introduced between the unbalanced terminal UT and the line portion L1. It is a thing.

(Example 2A)
Next, the pattern of the wiring layer M0 in one embodiment of the thin film balun having the circuit configuration shown in FIG. 16 will be described in detail. FIG. 17 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 2A of the embodiment 2A of the present invention. Configurations other than the wiring layer M0 are the same as in Example 1A. In the thin film balun 2A shown in FIG. 17, two capacitor electrodes DE1 and DE2 connected to the unbalanced terminal UT are formed, and the arrangement of one capacitor electrode DE1 is the same as in Example 1E. The other capacitor electrode DE2 is arranged to extend in the vertical direction so as to face the coil conductor 11 in the second row from the left of the coil portion C1 in plan view.

(Example 2B)
FIG. 18 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 2B of Example 2B of the present invention. Configurations other than the wiring layer M0 are the same as in Example 1A. In the thin film balun 2B shown in FIG. 18, two capacitor electrodes DE1 and DE2 connected to the unbalanced terminal UT are formed, and the arrangement of one capacitor electrode DE1 is the same as that in the embodiment 1E. The other capacitor electrode DE2 is branched, and the electrode area of the capacitor DE2 is enlarged compared to Example 2A.

(Characteristic evaluation)
With respect to the thin film baluns 2A and 2B described above, the passage characteristics (insertion loss) and the balance characteristics (phase difference and amplitude difference of the balanced signal) were obtained by simulation. The evaluation target frequency (resonance frequency fr) of the transmission signal was set to 2400 to 2500 MHz. FIG. 19 is a diagram showing the evaluation result of the pass characteristics, FIG. 20 is a diagram showing the evaluation result of the phase difference, and FIG. 21 is a diagram showing the evaluation result of the amplitude difference. In each figure, curves E2A and E2B show the evaluation results of the thin film baluns 2A and 2B, respectively. In addition, the curve E1E in each figure shows the evaluation result of the thin film balun curve of Example 1E which does not have the capacitor electrode DE2.

  From the results shown in FIGS. 20 and 21, it was confirmed that the thin film baluns of Examples 2A and 2B exhibited excellent equilibrium characteristics as compared with the thin film balun of Example 1E. From the results shown in FIG. 19, it was confirmed that the resonance frequency of the thin film balun of Example 2B was slightly shifted to the low frequency side as compared with the thin film balun of Example 1E.

  In addition, as above-mentioned, this invention is not limited to said each embodiment, A various deformation | transformation is possible in the limit which does not change the summary. For example, in the present embodiment, an example in which a part of the coil portions C1 and C2 constituting the unbalanced transmission line UL also serves as a capacitor electrode has been described. However, a coil portion is interposed between the coil portions C1 and C2 and the capacitor electrode DE1. Separate capacitor electrode layers connected to C1 and C2 may be formed. Further, for example, the arrangement of the unbalanced terminal UT, the balanced terminals BT1 and BT2, and the ground terminal G is not limited to the illustrated position. Of course, the order of the wiring layers on the insulating substrate 100 may be reversed. Furthermore, various coil arrangements can be employed without departing from the scope of the present invention.

  According to the thin film balun of the present invention, by introducing a capacitor between a part of the unbalanced transmission line facing the balanced transmission line and the unbalanced terminal, the thin balun can maintain the required characteristics of the balun. In particular, the present invention can be widely applied to wireless communication devices, devices, modules, and systems that are required to be small and thin, as well as equipment provided with them, and further to their manufacture.

  1, 1A to 1F, 2, 2A, 2B ... thin film balun, 11, 12, 21, 22 ... coil conductor, 11a, 11b, 12a, 12b, 21a, 21b, 22a, 22b ... end, 31, 32 ... wiring M0, M1, M2, M3 ... wiring layer, C1 ... coil part (first line part), C2 ... coil part (second line part), C3 ... coil part (third line part), C4 ... Coil part (fourth line part), D1, D2 ... capacitor, DE1, DE2 ... capacitor electrode, G ... ground terminal, L1 ... line part (first line part), L2 ... line part (second line part) ), L3 ... line part (third line part), L4 ... line part (fourth line part), P ... through hole, UL ... unbalanced transmission line (unbalanced circuit), BL ... balanced transmission line (balanced) Circuit), UT ... unbalanced terminal, BT1 ... balanced terminal, BT2 ... balanced terminal.

Claims (5)

An unbalanced transmission line;
A balanced transmission line opposed to and electromagnetically coupled to the unbalanced transmission line;
A capacitor electrode which is opposed to a part of the unbalanced transmission line facing the balanced transmission line and constitutes a capacitor;
An unbalanced terminal connected to the unbalanced transmission line and the capacitor electrode;
A thin film balun. A part of the unbalanced transmission line doubles as a capacitor electrode;
The thin film balun according to claim 1. An unbalanced transmission line having a first line portion and a second line portion;
A balanced transmission line having a third line part and a fourth line part facing and electromagnetically coupling to each of the first line part and the second line part;
A capacitor electrode facing a part of the second line portion facing the fourth line portion and constituting a capacitor;
An unbalanced terminal connected to the first line portion and the capacitor electrode;
A thin film balun. A capacitor electrode which is opposed to a part of the first line portion facing the third line portion and constitutes a capacitor;
The unbalanced terminal is connected to the first line portion, the capacitor electrode facing a part of the second line portion, and the capacitor electrode facing a part of the first line portion. Being
The thin film balun according to claim 3. An unbalanced terminal;
An unbalanced circuit in which one end is connected to the unbalanced terminal and the other end is an open end;
A balanced circuit electromagnetically coupled to the unbalanced circuit;
With
A capacitor is connected to a part of the unbalanced circuit excluding the open end, and the capacitor is also connected to the unbalanced terminal.
Thin film balun.

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