JP5246427B2 - Thin film balun - Google Patents

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, a magnetic 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 a 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 performed 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, the thin film balun of the present invention includes an unbalanced circuit, a balanced circuit magnetically coupled to the unbalanced circuit, and a capacitor connected to the unbalanced circuit, and constitutes an unbalanced circuit. A part of the line portion to be used also serves as one electrode of the capacitor.

  In such a configuration, a part of the line portion constituting the unbalanced circuit also serves as one electrode of the capacitor, whereby the capacitance C is introduced into the resonance circuit of the thin film balun, and the size and thickness can be reduced. In addition, as a result of intensive studies by the present inventors, when a part of the line portion is also provided as a capacitor electrode, the transmission frequency of the transmission signal is suppressed from increasing the resonance frequency and maintained within a desired range (specification). However, it has been found that the balance characteristics of the transmission signal can be adjusted.

  Although the details of the mechanism of action are still unclear, a part of the line section constituting the unbalanced circuit also serves as the electrode of the capacitor, so that the capacitor is placed close to the unbalanced circuit and directly. It is presumed that one of the factors is that not only the capacitance C is introduced but also a capacitance such as a stray capacitance is generated between the surrounding line portions and the effective capacitance on the unbalanced circuit side is increased. Is done. For this reason, it is assumed that the balance characteristics can be easily adjusted while maintaining the desired pass characteristics according to the specifications of the thin film balun by changing the position and area of the line portion that also serves as the electrode of the capacitor. Is done. However, the action is not limited to this.

  For example, the thin film balun of the present invention has an unbalanced transmission line and a balanced transmission line that is disposed opposite to the unbalanced transmission line and laminated so as to be magnetically coupled, and one end of the unbalanced transmission line serves as an unbalanced terminal. The other end is connected to the ground terminal via the C component, and the C component is constituted by a part of the line portion constituting the unbalanced transmission line and the counter electrode. As a more detailed example, the thin film balun of the present invention is disposed opposite to each of the unbalanced transmission line having the first line portion and the second line portion, and the first line portion and the second line portion, and A balanced transmission line having a third line portion and a fourth line portion to be magnetically coupled, an unbalanced terminal connected to the first line portion, and a ground connected to the second line portion via a C component A terminal and a counter electrode connected to the ground terminal and facing a part of the second line portion, and the C component is constituted by a part of the second line portion and the counter electrode. Even if it does in this way, the effect | action similar to having mentioned above is show | played.

  Preferably, the second line portion has an extending portion (extending from the line portion) extending from the line portion corresponding to the first line portion, and the counter electrode is an extension of the second line portion. The C component is constituted by the extended portion of the second line portion and the counter electrode. As described above, since the second line portion includes the extending portion, the magnetic coupling between the first line portion and the third line portion and the magnetic coupling between the second line portion and the fourth line portion are caused. By maintaining the equivalent and projecting from the region where the C component is directly coupled to the balanced transmission line, the capacitance is effectively introduced into the resonance circuit of the thin film balun, and the thin film can be reduced. As a result, it is presumed that both suppression of high resonance frequency and improvement of transmission signal balance characteristics can be achieved. However, the action is not limited to this.

  For example, the thin film balun according to the present invention includes a first coil part and a second coil part, and an unbalanced transmission line having a first coil part and a second coil part. A balanced transmission line having three coil parts and a fourth coil part; an unbalanced terminal connected to the first coil part; a ground terminal connected to the second coil part via a C component; And a counter electrode that is connected to the terminal and faces a part of the second coil part, and the C component is constituted by a part of the second coil part and the counter electrode. Even if it does in this way, the effect | action similar to having mentioned above is show | played.

  For example, the counter electrode is opposed to a part of the coil conductor closer to the outer coil conductor than the inner coil conductor in the second coil portion. Accordingly, the counter electrode can be appropriately separated from the coil opening through which the magnetic flux generated by the magnetic coupling between the second coil portion and the fourth coil portion passes. As a result, as described above, the magnetic coupling between the first coil portion and the third coil portion and the magnetic coupling between the second coil portion and the fourth coil portion are maintained in an almost equivalent state. It is estimated that the capacitance is effectively introduced into the resonance circuit of the thin film balun, and further, the suppression of the resonance frequency can be suppressed and the balance characteristic of the transmission signal can be improved. However, the action is not limited to this. In this case, preferably, the counter electrode opposes a part of the outer peripheral coil conductor in the second coil portion.

  Furthermore, as a result of further earnest studies, the present inventor has found various examples of more suitable counter electrode configurations. That is, as an example, the counter electrode is parallel to the extending direction of a part of the space between adjacent coil conductors constituting the second coil portion (in other words, along the extending direction). It is useful that the electrode is opposed to a part of the counter electrode on both sides of the space. Alternatively, the counter electrode is parallel to the extending direction of a part of the coil conductor constituting the second coil portion (in other words, provided along the extending direction) and one of the coil conductors is provided. It is also preferable that it is opposed to the part.

  According to the present invention, a part of the line portion constituting the unbalanced circuit also serves as one electrode of the capacitor connected to the unbalanced circuit, thereby maintaining the required characteristics of the balun and reducing the size and thickness. Can be realized.

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. 2 is a horizontal sectional view of a wiring layer M0 of a thin film balun 1. FIG. 2 is a horizontal sectional view of a wiring layer M1 of a thin film balun 1. FIG. 2 is a horizontal sectional view of a wiring layer M2 of a thin film balun 1. FIG. 2 is a horizontal sectional view of a wiring layer M3 of a thin film balun 1. FIG. It is a horizontal sectional view in wiring layer M0 of thin film balun 1A. It is a horizontal sectional view in wiring layer M0 of thin film balun 1B. 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 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. 3 is a horizontal sectional view of a wiring layer M0 of a thin film balun 2. FIG. 3 is a horizontal sectional view of a wiring layer M1 of a thin film balun 2. FIG. 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 horizontal sectional view in wiring layer M0 of thin film balun 2C. It is a horizontal sectional view in wiring layer M0 of thin film balun 2D. 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 a horizontal sectional view in wiring layer M0 of thin film baluns 1E and 1F. It is a horizontal sectional view in wiring layer M0 of thin film baluns 2-2B. 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. It is a horizontal sectional view in wiring layer B1 of thin film balun 4 (comparative example). It is a graph which shows the evaluation result of a passage characteristic.

  Hereinafter, embodiments of the present invention will be described 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. Further, the following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention only to the embodiments. Furthermore, the present invention can be variously modified without departing from the gist thereof.

  FIG. 1 is an equivalent circuit diagram showing the configuration of a preferred 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. Magnetic couplings are formed by the portions L4.

  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, and a part of the other end side of the coupling end of the line portion L2 with the line portion L1. Are connected to the ground terminal G (ground potential) via a capacitor D which is a C component (capacitance component). The capacitor D is configured such that an electrode D1 constituted by a part on the other end side of the line portion L2 and an electrode D2 (counter electrode) connected to the ground terminal G are disposed to face each other via an appropriate dielectric. is there. 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. Further, the connecting portion of the line portion L3 and the line portion L4 is grounded to the same potential as 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. The shape of the line portions L1 to L4 can be any shape as long as the magnetic coupling described above is formed. For example, the shape of 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. In the thin film balun 1, 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 magnetically coupled (first magnetic coupling), and the line portion L2 and the line portion L4 are magnetically coupled (second magnetic coupling), whereby the input unbalanced signal is input. Is converted into two balanced signals having a phase difference of 180 ° (π), and these two balanced signals are output from the balanced terminals BT1 and BT2, respectively. Note that the conversion operation from the balanced signal to the unbalanced signal is the reverse of the conversion operation from the unbalanced signal to the balanced signal described above.

  Next, the wiring structure 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 unbalanced transmission line UL described above is formed by the wiring layer M1, and the balanced transmission line BL is formed by the wiring layer M2. Insulating layers are formed between wirings in the same wiring layer and between different wiring layers. For example, an insulating layer 102 made of silicon nitride is formed between the wiring layers M0 and M1. For example, polyimide is used as the insulating layer 101 in other portions. However, the material is not limited to those described above, and may be not only an inorganic insulator such as silicon nitride, alumina or silica, but also an organic insulator such as polyimide or epoxy resin, which can be appropriately selected. The unbalanced terminal UT, the balanced terminals BT1 and BT2, and the ground terminal G are formed so as to penetrate all the insulating layers. Thus, the thin film balun 1 is composed of a thin film multilayer structure formed on the insulating substrate 100.

  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.

(First embodiment)
3 to 6 are horizontal sectional views schematically showing each wiring layer in the thin film balun 1 of the first embodiment. As shown in FIGS. 3 to 6, unbalanced terminals UT, balanced terminals BT1, BT2, and a ground terminal G are formed in all the wiring layers B1, M0 to M3, and the terminals UT to BT2, 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 electrode D2 of the capacitor D is formed at a position facing a part of the coil portion C2 of the wiring layer M1. The electrode D2 is connected to the ground terminal G. In the first embodiment, the electrode D2 of the capacitor D is a coil conductor on the outer periphery of the coil portion 2, and is parallel to the coil conductor extending from the ground terminal G toward the balanced terminal BT2.

  As shown in FIG. 4, the wiring layer M1 includes a coil part C1 (first coil part, first line part) and a coil part C2 (second coil part, second coil) constituting the unbalanced transmission line UL. 2 line portions) are formed adjacent to each other. 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. The outer end 12a of the coil conductor 12 is open, but a part of the outer coil conductor 12 also serves as the capacitor electrode D1 and faces the electrode D2 of the wiring layer M0.

  Furthermore, as shown in FIG. 5, the wiring layer M2 includes a coil part C3 (third coil part, third line part) and a coil part C4 (fourth coil part, constituting the balanced transmission line BL). (Fourth line portion) is formed adjacent to each other. 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 parts C3 and C4 of the balanced transmission line BL are respectively arranged to face the coil parts C1 and C2 of the unbalanced transmission line UL, and are magnetically coupled at the opposed parts 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.

  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 the present embodiment, two coil portions C1 and C2 constituting the unbalanced transmission line are formed in the wiring layer M1 which is one layer, and balanced in the wiring layer M2 which is another layer adjacent thereto. 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 1 constituting an equivalent circuit shown in FIG. 1 is obtained by a multilayer wiring structure in which an electrode D2 for constituting a capacitor D is formed opposite to a part of the capacitor D.

(1A embodiment)
FIG. 7 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 1A of the first embodiment A according to the present invention. The configuration other than the wiring layer M0 is the same as that of the first embodiment. In the thin film balun 1A shown in FIG. 7, the electrode D2 of the capacitor D is parallel to the extending direction of the coil conductor in the second row from the right of the coil portion C2 and faces a part of the coil conductor in plan view. Is arranged.

(1B embodiment)
FIG. 8 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 1B of the first embodiment according to the present invention. The configuration other than the wiring layer M0 is the same as that of the first embodiment. In the thin film balun 1B shown in FIG. 8, the electrode D2 of the capacitor D has an extended space between the coil conductor in the first row (outermost circumference) and the coil conductor in the second row from the right of the coil portion C2 in plan view. It is arranged so as to be parallel to the direction and to face part of the coil conductors on both sides of the space.

(1C embodiment)
FIG. 9 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 1C of the first C embodiment according to the present invention. The configuration other than the wiring layer M0 is the same as that of the first embodiment. In the thin film balun 1C shown in FIG. 9, the electrode D2 of the capacitor D is parallel to the extending direction of the coil conductor in the third row from the right of the coil portion C2 and faces a part of the coil conductor in plan view. Is arranged.

(1D embodiment)
FIG. 10 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 1D of the first D embodiment according to the present invention. The configuration other than the wiring layer M0 is the same as that of the first embodiment. The thin film balun 1D shown in FIG. 10 is obtained by shortening the length of the electrode D2 of the capacitor D of the thin film balun 1B of the first B embodiment. The length of the electrode D2 is shortened.

(Characteristic evaluation)
With respect to the thin film baluns 1 to 1D of each embodiment described above, the pass 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. 11 is a diagram showing the evaluation result of the pass characteristic, FIG. 12 is a diagram showing the evaluation result of the phase difference, and FIG. 13 is a diagram showing the evaluation result of the amplitude difference. In each figure, curves E1, E1A to E1D show the evaluation results of thin film baluns 1, 1A to 1D, respectively.

  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. 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 balun of each embodiment maintained excellent characteristics in terms of pass characteristics and phase balance. It was confirmed that the amplitude balance can be adjusted by the arrangement of the electrode D2 of the capacitor D. Among these, in the thin film baluns 1, 1 </ b> A, 1 </ b> B, and 1 </ b> D where the electrode D <b> 2 is opposed to a part of the coil conductor closer to the outer coil conductor than the inner coil conductor in the coil portion C <b> 2, the thin film balun 1 </ b> C is used. It was confirmed that the amplitude balance was superior to Furthermore, among these, the thin-film baluns 1, 1B, and 1D in which the electrode D2 is opposed to a part of the outer peripheral coil conductor in the coil portion C2 have excellent amplitude balance as compared with the thin-film balun 1A. Was confirmed. In particular, from the evaluation result for the thin film balun 1B, the passing characteristics of the thin film balun in which the electrode D2 of the capacitor D is arranged in parallel with the extending direction of the space between the adjacent coil conductors in the coil portion C2 in plan view and It was confirmed that the equilibrium characteristics were the best.

(Second Embodiment)
In the thin film balun 2 of the second embodiment, the coil part C2 is made longer than the coil part C1, and the electrode D2 of the capacitor D is disposed so as to face the extended part. 14 and 15 are horizontal sectional views schematically showing the wiring layers M0 and M1 in the thin film balun 2 of the second embodiment according to the present invention.

  As shown in FIG. 14, in the wiring layer M0, the electrode D2 of the capacitor D is connected to the ground terminal G and extends from the ground terminal G toward the unbalanced terminal UT.

  Further, as shown in FIG. 15, the coil part C2 formed in the wiring layer M1 is formed longer than the coil part C1, and the extending part 12c is within the same layer as the coil part C2 in the winding direction. It extends in the same direction as and extends out of the region facing the balanced transmission line. The extending portion 12c also serves as the electrode D1 of the capacitor D. The electrode D1, which is a part of the coil portion C2, faces the electrode D2 of the wiring layer M0. Other arrangements are the same as in the first embodiment.

(Second Embodiment A)
FIG. 16 is a horizontal cross-sectional view schematically showing a wiring layer M0 in the thin film balun 2A of the 2A embodiment according to the present invention. The configuration other than the wiring layer M0 is the same as that of the second embodiment. In the thin film balun 2A shown in FIG. 16, the electrode D2 of the capacitor D is parallel to the extending direction of the coil conductor in the second row from the bottom of the coil portion C2 and faces a part of the coil conductor in plan view. Is arranged.

(Second Embodiment)
FIG. 17 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 2B of the second B embodiment according to the present invention. The configuration other than the wiring layer M0 is the same as that of the second embodiment. In the thin film balun 2B shown in FIG. 17, the electrode D2 of the capacitor D is parallel to the extending direction of the space between the coil conductor in the second row and the coil conductor in the third row from the right of the coil portion C2 in plan view. And it arrange | positions so that a part of coil conductor of the both sides of the said space may be opposed.

(2C embodiment)
FIG. 18 is a horizontal sectional view schematically showing the wiring layer M0 in the thin film balun 2C of the second C embodiment according to the present invention. The configuration other than the wiring layer M0 is the same as that of the second embodiment. In the thin film balun 2C shown in FIG. 18, the electrode D2 of the capacitor D has a space between the coil conductor (extension part 12c) in the first row and the coil conductor in the second row from the bottom of the coil portion C2 in plan view. It is arranged so as to be parallel to the extending direction and to face part of the coil conductors on both sides of the space.

(2D embodiment)
FIG. 19 is a horizontal sectional view schematically showing a wiring layer M0 in the thin film balun 1B of the second D embodiment according to the present invention. The configuration other than the wiring layer M0 is the same as that of the second embodiment. A thin film balun 2D shown in FIG. 19 has an electrode D2 of a capacitor D arranged so as to face a plurality of coil conductors 21 in the lower right region of the coil portion C2. However, the area of the electrode D2 is the same as in the second to second C embodiments.

(Characteristic evaluation)
With respect to the thin film baluns 2 to 2D of each of the embodiments described above, the pass characteristic (insertion loss) and the balance characteristic (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. 20 is a diagram showing the evaluation result of the pass characteristics, FIG. 21 is a diagram showing the evaluation result of the phase difference, and FIG. 22 is a diagram showing the evaluation result of the amplitude difference. In each figure, curves E2, E2A to E2D show the evaluation results of thin film baluns 2, 2A to 2D, respectively.

  From these results, it was confirmed that the thin film balun of each embodiment maintained excellent characteristics in terms of pass characteristics and phase balance. It was confirmed that the amplitude balance can be adjusted by the arrangement of the electrode D2 of the capacitor D. From the evaluation results for the thin film baluns 2 to 2D, the shift of the peak value of the resonance frequency fr is small even if the position of the electrode D2 is adjusted by making the electrode D2 of the capacitor D face the extending part 12c of the coil part C2. Was confirmed. In particular, from the evaluation results for the thin film balun 2D, the amplitude balance of the thin film balun in which the electrode D2 of the capacitor D is disposed so as to face the plurality of coil conductors 21 in the lower right region of the coil portion C2 is the best in plan view. It was confirmed that

  Next, the difference of the passage characteristic and the balance characteristic by the presence or absence of the extension part in the coil part C2 was evaluated. For this evaluation, the thin film baluns of the following 1E, 1F and 2,2A, 2B embodiments were used.

(1E, 1F embodiment)
FIG. 23 is a horizontal sectional view schematically showing the wiring layer M1 in the thin film baluns 1E and 1F of the first and first embodiments according to the present invention. As shown in FIG. 23, in the thin film baluns 1E and 1F, the coil part C2 does not have an extending part. Although not shown, the thin film balun 1E has the same wiring layer M0 as the thin film balun 2A shown in FIG. 16, and the thin film balun 1F has the same wiring layer M0 as the thin film balun 2B shown in FIG. The configuration other than the wiring layers M0 and M1 is the same as that in the first embodiment.

(Second, 2A, 2B embodiments)
FIG. 24 is a horizontal sectional view positively showing the wiring layer M1 in the thin film baluns 2, 2A, 2B of the second, 2A, 2B embodiments according to the present invention described above. As shown in FIG. 24, the thin film baluns 2, 2 </ b> A, 2 </ b> B have an extending portion 12 c that becomes the electrode D of the capacitor D. As described above, the thin film balun 2 includes the wiring layer M0 illustrated in FIG. 14, the thin film balun 2A includes the wiring layer M0 illustrated in FIG. 16, and the thin film balun 2B includes the wiring layer M0 illustrated in FIG. The configuration other than the wiring layers M0 and M1 is the same as that in the first embodiment.

(Characteristic evaluation)
With respect to the thin film baluns 1E and 1F of each of the embodiments described above, the pass 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. 25 is a diagram showing evaluation results of pass characteristics, FIG. 26 is a diagram showing evaluation results of phase differences, and FIG. 27 is a diagram showing evaluation results of amplitude differences. In each figure, the results of the above-described thin film baluns 2, 2A, 2B are also shown. In each figure, curves E1E, E1F, E2, and E2A to E2B show the evaluation results of thin film baluns 1E, 1F, 2, and 2A to 2B, respectively.

  From the evaluation results for the thin film baluns 1E and 1F, the shift of the peak value of the resonance frequency fr is small even if the position of the electrode D2 is adjusted by making the electrode D2 of the capacitor D face the extending part 12c of the coil part C2. Was confirmed.

(Comparative example)
FIG. 28 is a horizontal sectional view schematically showing the wiring layer B1 in the thin film balun 4 of the comparative example. The wiring layer B1 is provided between the insulating substrate 100 and the wiring layer M0. As shown in FIG. 28, in the thin film balun 4 of the comparative example, the capacitor K is disposed in a region outside the range of the coil portion C2 in plan view. Although only the electrode K1 of the capacitor K is shown in the drawing, the counter electrode having the same shape as the electrode K1 (corresponding to the electrode D2 in the embodiment of the present invention) is provided at a position in the wiring layer M0 facing the electrode K1. Is formed). The electrode K1 is connected to the through hole P near the ground terminal G by the wiring 51, and is connected to the end 12a of the coil portion C2 of the wiring layer M1 through the through hole P. The counter electrode formed in the wiring layer M0 is connected to the ground terminal G by the wiring 52.

(Characteristic evaluation)
FIG. 29 shows the result of evaluating the transmission signal transmission characteristic (attenuation characteristic) by simulation for the thin film balun 4 of the above comparative example. In the simulation, the transmission target evaluation frequency (resonance frequency fr) of the transmission signal was set to 2400 to 2500 MHz, the attenuation in this frequency range was set to a target specification of less than 1 dB, and the pass characteristics of each thin film balun were evaluated.

  In FIG. 29, a curve R4 shows the evaluation result of the thin film balun 4. From these results, as shown in FIG. 29, the thin film balun 4 of the comparative example has a larger attenuation amount in the frequency range of the target specification in the pass characteristics than the thin film balun according to the present invention, and does not satisfy the target specification. There was found.

  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, 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. Further, the multilayer wiring structure constituting the thin film balun may be less than the number of layers shown or more than the number of layers shown. Furthermore, it is of course possible to have a structure in which the order of the wiring layers on the insulating substrate 100 is 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, a part of the line portion constituting the unbalanced circuit also serves as one electrode of the capacitor connected to the unbalanced circuit, thereby maintaining the required balun characteristics. In particular, wireless communication devices, apparatuses, modules, and systems that are required to be small and thin, as well as equipment provided with them, and can be widely applied to their manufacture. is there.

  1 to 1F, 2 to 2C ... thin film balun according to the present invention, 4 ... comparative thin film balun, 11, 12, 21, 22 ... coil conductors, 11a, 11b, 12a, 12b, 21a, 21b, 22a, 22b ... End part 31, 32 ... wiring, 51 ... wiring, B1, M0, M1, M2, M3 ... wiring layer, C1 ... coil part (first coil part, first line part), C2 ... coil part (first 2 coil part, 2nd line part), C3 ... coil part (3rd coil part, 3rd line part), C4 ... coil part (4th coil part, 4th line part), D ... Capacitor (C component, capacitance component), D1... Electrode, D2... Electrode (counter electrode), G .. ground terminal (ground potential), K .. capacitor, K1... Electrode, L1 .. line portion (first line portion), L2 ... Line part (second line part), L3 ... Line part (third line part), L4 ... Line part (first Line ...), P ... through hole, UL ... unbalanced transmission line (unbalanced circuit), BL ... balanced transmission line (balanced circuit), UT ... unbalanced terminal, BT1 ... balanced terminal (first balanced terminal), BT2... Balanced terminal (second balanced terminal).

Claims (4)

An unbalanced transmission line having a first coil portion and a second coil portion;
A balanced transmission line having a third coil portion and a fourth coil portion that are arranged opposite to each other and magnetically coupled to each of the first coil portion and the second coil portion;
An unbalanced terminal connected to the first coil portion;
A ground terminal connected to the second coil portion via a C component;
A counter electrode connected to the ground terminal and facing a part of the second coil portion;
With
The C component is constituted by a part of the second coil part and the counter electrode ,
The counter electrode is opposed to a part of the coil conductor that is closer to the outer coil conductor than the inner coil conductor in the second coil portion.
Thin film balun. The counter electrode is opposed to a part of the outer peripheral coil conductor in the second coil portion,
The thin film balun according to claim 1 . The counter electrode is parallel to the extending direction of a part of a space between adjacent coil conductors constituting the second coil portion, and faces a part of the counter electrode on both sides of the space. Yes,
The thin film balun according to claim 1 . The counter electrode is parallel to the extending direction of a part of the coil conductor constituting the second coil part and is opposed to a part of the coil conductor.
The thin film balun according to claim 1 .

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