JP5880675B2 - High frequency transmission line and antenna device - Google Patents

Description

  The present invention relates to a high frequency transmission line, and more particularly to a high frequency transmission line connected between an antenna end and a connector end.

  In an electronic device that handles a high-frequency signal such as a mobile communication terminal, a high-frequency transmission line that transmits the high-frequency signal to a signal processing unit is used. For example, 50Ω or 75Ω coaxial cables are used in mobile communication terminals.

  Such a coaxial cable is sometimes provided with a connector between the coaxial cable and the high-frequency signal processing unit as disclosed in Patent Document 1 and Patent Document 2, for example. FIG. 1 is a diagram showing an example thereof. 1A is a cross-sectional view of a coaxial cable, and FIG. 1B shows a state where a connector 40 is attached to one end thereof.

JP 2003-060425 A Japanese Patent Laid-Open No. 2004-064282

  For example, when an antenna is connected to the first end of a high-frequency transmission line such as a coaxial cable and a connector is connected to the second end, a high-frequency signal received by the antenna is transmitted through the coaxial cable and the connector. Sent to.

  However, the characteristic impedance of the antenna is usually lower than the characteristic impedance of the coaxial cable (usually 50Ω or 75Ω), whereas the characteristic impedance of the connector is higher than the characteristic impedance of the coaxial cable. Therefore, the coaxial cable resonates at a frequency at which a standing wave having an odd multiple of a quarter wavelength is generated.

  FIG. 1C is a diagram showing this state. In FIG. 1C, when the antenna is connected to the first end FP and the connector is connected to the second end SP, the first end is low impedance and the second end is high impedance. Resonance occurs at a frequency at which a standing wave is generated with the minimum voltage point (short-circuit end) and the second end being the maximum voltage point (open end).

Here, when one wavelength in the coaxial cable 100 is represented by λg, the length of the coaxial cable is represented by Lg, and the relative dielectric constant of the dielectric of the coaxial cable 100 is represented by εr, the resonance frequency of the fundamental wave that resonates at a quarter wavelength. fo is
fo = 1 / (4Lg√εr) × c (c: speed of light) (1)
Are in a relationship. If Lg = 9 [cm] and √εr = 1, resonance in the fundamental mode occurs at about 830 MHz. Therefore, the cutoff frequency of this coaxial cable is lower than about 830 MHz. In this case, for example, when transmitting a signal in the 900 MHz band, the insertion loss in the coaxial cable becomes a problem.

  In addition, none of the conventional high-frequency transmission lines has a special structure in consideration of bending.

  An object of the present invention is to provide a high-frequency transmission line and an antenna device that are highly flexible and can be bent easily.

(1) In the high frequency transmission line of the present invention, the first end is a low impedance end and the second end is a high impedance end.
A low impedance portion that is a strip line and a high impedance portion that is a microstrip line or a coplanar line, the characteristic impedance of which is higher than that of the low impedance portion, and
It is bent at the high impedance portion and is not bent at the low impedance portion .
(2) In the high frequency transmission line of the present invention, the first end is a low impedance end and the second end is a high impedance end.
A low impedance portion that is a strip line and a high impedance portion that is a microstrip line or a coplanar line, the characteristic impedance of which is higher than that of the low impedance portion, and
At least one of the ground electrodes constituting the stripline is not formed in the high impedance portion,
It is bent at the high impedance portion.
(3) In (1) or (2), the total length of the low impedance portions is preferably longer than the total length of the high impedance portions.

( 4 ) In any one of (1) to (3) , for example, the low impedance end is an antenna connection end, and the high impedance end is a connector connection end.

( 5 ) In any one of (1) to (4), the low impedance portion and the high impedance portion are formed of a laminate including a plurality of dielectric layers and line conductors, and the high impedance portion is It is preferable that the number of stacked dielectric layers is smaller than that of the low impedance portion.

( 6 ) An antenna device of the present invention includes the high frequency transmission line according to any one of (1) to (4) and an antenna element connected to the low impedance end, and the high frequency transmission line includes a plurality of dielectrics. It is comprised by the laminated body containing a body layer and a line conductor, The said antenna element is integrally provided with the said high frequency transmission line in the said laminated body.

( 7 ) The antenna device of the present invention includes the high-frequency transmission line according to ( 5 ) and an antenna element connected to the low impedance end, and the antenna element is integrated with the high-frequency transmission line in the laminate. It is provided in.

  According to the present invention, it is possible to obtain a high-frequency transmission line and an antenna device that are highly flexible and can be bent easily.

FIG. 1A is a cross-sectional view of a conventional coaxial cable, and FIG. 1B is a view showing a state where a connector 40 is attached to one end thereof. FIG. 1C is a diagram illustrating a state where a ¼ wavelength standing wave is generated in the coaxial cable. FIG. 2 is a cross-sectional view of each part of the high-frequency transmission line 101 of the first embodiment. FIG. 3 is an exploded perspective view of the high-frequency transmission line 101. FIG. 4A is a diagram illustrating characteristic impedance of each part of the high-frequency transmission line 101, and FIG. 4B is a diagram illustrating an example of a standing wave generated in the high-frequency transmission line 101. FIG. 4C is an equivalent circuit diagram in which the high-frequency transmission line 101 is represented by a lumped constant circuit. FIG. 5 is a diagram showing frequency characteristics of insertion loss of the high-frequency transmission line 101. FIG. 6 is a cross-sectional view of each part of the high-frequency transmission line 102 of the second embodiment. FIG. 7 is an exploded perspective view of the high-frequency transmission line 102 of the second embodiment. FIG. 8A is a diagram illustrating the characteristic impedance of each part of the high-frequency transmission line 102, and FIG. 8B is a diagram illustrating an example of a standing wave generated in the high-frequency transmission line 102. FIG. 8C is an equivalent circuit diagram in which the high-frequency transmission line 102 is represented by a lumped constant circuit. FIG. 9 is a cross-sectional view of each part of the high-frequency transmission line 103 of the third embodiment. FIG. 10 is an exploded perspective view of the high-frequency transmission line 103. 11A shows the characteristic impedance of each part of the high-frequency transmission line 103, and FIG. 11B shows an example of a standing wave generated in the high-frequency transmission line 103. FIG. FIG. 11C is an equivalent circuit diagram in which the high-frequency transmission line 101 is represented by a lumped constant circuit. FIG. 12 is an exploded perspective view of the high-frequency transmission line 104 of the fourth embodiment. FIG. 13A is a perspective view of the high-frequency transmission line 105 of the fifth embodiment, and FIG. 13B is an exploded perspective view thereof. FIG. 14A is a perspective view of the high-frequency transmission line 106 of the sixth embodiment, and FIG. 14B is an exploded perspective view thereof. FIG. 15 is a perspective view of the high-frequency transmission line 107 according to the seventh embodiment. FIG. 16 is a cross-sectional view of the vicinity of the bent portion FF1 among the bent portions FF1 to FF4. FIG. 17 is a partial plan view of the high-frequency transmission line 108 of the eighth embodiment. 18A is a perspective view of an antenna device 201 according to the ninth embodiment, and FIG. 18B is an exploded perspective view thereof. FIG. 19 is an equivalent circuit diagram of the antenna device 201.

<< First Embodiment >>
FIG. 2 is a cross-sectional view of each part of the high-frequency transmission line 101 of the first embodiment. FIG. 3 is an exploded perspective view thereof. FIG. 2A is a longitudinal sectional view of the high-frequency transmission line 101 in the longitudinal direction. 2B is a cross-sectional view of the stripline SL1 portion of FIG. 2A, FIG. 2C is a cross-sectional view of the microstrip line MSL portion of FIG. 2A, and FIG. FIG. 2A is a cross-sectional view of the strip line SL2 portion of FIG. 2A, and FIG. 2E is a cross-sectional view of the coplanar line CPL portion of FIG. 2A.

  As shown in FIG. 2A, the high-frequency transmission line 101 includes a first strip line SL1, a microstrip line MSL, a second strip line SL2, and a coplanar line CPL.

  As shown in FIG. 3, the high-frequency transmission line 101 includes four dielectric base materials 31a, 31b, 31c, and 31d (hereinafter simply referred to as base materials). A ground line G3 is formed on the upper surface of the base material 31a. A signal line S1 and two ground lines G2a and G2b are formed on the upper surface of the base material 31b. Two ground lines G1a and G1b are formed on the upper surface of the substrate 31c. Via conductors V1a and V1b connecting the ground line G1b and the ground lines G2a and G2b are formed on the base material 31b. Via conductors V2a and V2b connecting the ground line G3 and the ground lines G2a and G2b are formed on the base material 31a. The high-frequency transmission line 101 is a laminate of the base materials 31a, 31b, 31c and the base material 31d on which these various conductor lines are formed.

  The first strip line SL1 includes ground lines G1a and G3 and a signal line S1, and a strip line is constituted by these conductor lines and the dielectric layer of the base material. Similarly, the second strip line SL2 includes ground lines G1b and G3 and a signal line S1, and a strip line is constituted by these conductor lines and the dielectric layer of the base material. The microstrip line MSL includes a ground line G3 and a signal line S1, and the microstrip line is configured by these conductor lines and the dielectric layer of the base material. The coplanar line CPL includes ground lines G2a and G2b and a signal line S1, and these conductor lines and the dielectric layer of the base material constitute a coplanar line.

  FIG. 4A is a diagram illustrating characteristic impedance of each part of the high-frequency transmission line 101, and FIG. 4B is a diagram illustrating an example of a standing wave generated in the high-frequency transmission line 101.

  The characteristic impedances Za1 and Za2 of the strip lines SL1 and SL2 are 50Ω, respectively. The characteristic impedance Zb1 of the microstrip line MSL is 75Ω. The characteristic impedance Zb2 of the coplanar line CPL is 200Ω.

  When an antenna is connected to the first end FP of the high-frequency transmission line 101 and a connector is connected to the second end SP, the first end is a low impedance end and the second end is a high impedance end, so the first end FP Resonates at a frequency at which a standing wave is generated where the voltage is at the minimum voltage point (short-circuit end) and the second end is the voltage maximum point (open end). However, since the characteristic impedance Zb1 of the microstrip line MSL is higher than the characteristic impedance of the strip lines SL1 and SL2 (the relation of Zb1> (Za1, Za2)), the microstrip line as shown in FIG. A standing wave is generated such that the position of the MSL becomes the maximum voltage (antinode of the voltage intensity distribution). Further, since the characteristic impedance Zb2 of the coplanar line CPL is higher than the characteristic impedance of the strip line SL2 (the relation of Zb2> Za2), the position of the coplanar line CPL at a predetermined frequency is shown in FIG. A standing wave that has the maximum voltage (antinode of voltage intensity distribution) is generated.

  Therefore, the 1/4 wavelength resonance mode as shown in FIG. 1C does not occur. This is because the quarter-wave resonance mode does not have the maximum voltage in the microstrip line MSL portion. Therefore, the 3/4 wavelength resonance becomes a fundamental wave (lowest harmonic) mode, and an odd multiple resonance that is three times or more of the 1/4 wavelength resonance occurs. Therefore, resonance occurs in which the number of maximum voltage points Em (antinodes of the voltage intensity distribution) is 2 or more. In other words, the strip lines SL1 and SL2, the microstrip line MSL, and the coplanar line CPL are arranged so that the position where the voltage maximum point Em is located is the high impedance part of the transmission line and the region away from the position is the low impedance part. .

  FIG. 4C is an equivalent circuit diagram showing the high-frequency transmission line 101 as a lumped constant circuit. Near the voltage maximum point Em on the high-frequency transmission line 101, the electric field energy density is high and the magnetic field energy density is low. Therefore, the portion with high electric field energy density is represented by capacitors C1 and C2, and the portion with high magnetic field energy density is represented by inductors L1 and L2.

  FIG. 5 is a diagram showing frequency characteristics of insertion loss of the high-frequency transmission line 101. In FIG. 5, a curve C is a characteristic of the high-frequency transmission line whose characteristic impedance is constant over the entire length as in the example shown in FIG. A curve P is a characteristic of the high-frequency transmission line 101 of the first embodiment. Since the high frequency transmission line 101 acts as an equivalent low pass filter as shown in FIG. 4C, the frequency characteristic of the insertion loss of the high frequency transmission line 101 is similar to the frequency characteristic of the LC low pass filter as shown in FIG. It will be a thing.

  In FIG. 5, the resonance frequency by the 1/4 wavelength resonance by the high-frequency transmission line of the conventional structure is fo1, and the frequency fc1 that attenuates by 3 dB is the cut-off frequency. The resonance frequency due to 3/4 wavelength resonance of the high-frequency transmission line 101 is fo2, and the frequency fc2 that attenuates by 3 dB is the cutoff frequency. Thus, the cut-off frequency fc2 of the high-frequency transmission line 101 of the first embodiment is high, and a low insertion loss characteristic can be obtained over a wide band.

Here, when one wavelength on the line of the high-frequency transmission line 101 is represented by λg and the line length is represented by Lg, the resonance frequency fo2 of the 3/4 wavelength resonance is
fo2 = 3 / (4Lg√εr) × c (c: speed of light) (2)
Are in a relationship. Assuming that Lg = 9 [cm] and √εr = 1, 3/4 wavelength resonance occurs at a high frequency of about 2.5 GHz. Therefore, for example, the 900 MHz band is sufficiently lower than the cut-off frequency fc2, and the insertion loss of the signal is kept low.

  A slight impedance mismatch occurs at the boundary between the strip lines SL1, SL2 and the microstrip line MSL and at the boundary between the strip line SL2 and the coplanar line CPL. However, the reflection loss due to this impedance mismatch is not a problem compared to the above-described effect of reducing the insertion loss.

  Incidentally, as shown in FIG. 4, the vicinity of the center of the coplanar line CPL is the voltage maximum point Em, and therefore a position slightly inside the second end SP of the high-frequency transmission line 101 becomes an antinode of the voltage intensity distribution. Therefore, precisely, the lowest frequency at which a standing wave is generated is a slightly higher frequency than the expression (2).

<< Second Embodiment >>
FIG. 6 is a cross-sectional view of each part of the high-frequency transmission line 102 of the second embodiment. FIG. 7 is an exploded perspective view thereof. FIG. 6A is a longitudinal sectional view in the longitudinal direction of the high-frequency transmission line 102. 6B is a cross-sectional view of the first stripline SL1 portion of FIG. 6A, FIG. 6C is a cross-sectional view of the microstrip line MSL portion of FIG. 6A, and FIG. 6D is a cross-sectional view taken along the second strip line SL2 in FIG. 6A, FIG. 6E is a cross-sectional view taken along the first coplanar line CPL1 in FIG. 6A, and FIG. FIG. 6A is a cross-sectional view of the third strip line SL3 portion of FIG. 6A, and FIG. 6G is a cross-sectional view of the second coplanar line CPL2 portion of FIG. 6A.

  As shown in FIG. 6A, the high-frequency transmission line 102 includes a first strip line SL1, a microstrip line MSL, a second strip line SL2, a first coplanar line CPL1, a third strip line SL3, and a second strip line SL3. A coplanar line CPL2 is provided.

  As shown in FIG. 7, the high-frequency transmission line 102 includes four dielectric base materials 31a, 31b, 31c, and 31d. Ground lines G2a and G2b are formed on the upper surface of the base material 31a. A signal line S1 and four ground lines G3a, G3b, G4a, and G4b are formed on the upper surface of the base material 31b. Three ground lines G1a, G1b, and G1c are formed on the upper surface of the base material 31c. The ground lines G1b, G3a, G3b, G2a are connected by via conductors as shown in the figure. The ground lines G1c, G3a, G3b, G4a, G4b, and G2b are connected by via conductors as shown in the figure.

  The high-frequency transmission line 102 is a laminate of the base materials 31a, 31b, 31c and the base material 31d on which these various conductor lines are formed. However, the first coplanar line CPL1 is a laminated body of the base materials 31b and 31c, and is configured to be thinner than other line portions.

  FIG. 8A is a diagram illustrating the characteristic impedance of each part of the high-frequency transmission line 102, and FIG. 8B is a diagram illustrating an example of a standing wave generated in the high-frequency transmission line 102.

  The characteristic impedances Za1, Za2 and Za3 of the strip lines SL1, SL2 and SL3 are 50Ω, respectively. The characteristic impedance Zb1 of the microstrip line MSL is 75Ω. The characteristic impedances Zb2 and Zb3 of the coplanar lines CPL1 and CPL2 are 200Ω.

  When an antenna is connected to the first end FP of the high-frequency transmission line 102 and a connector is connected to the second end SP, the first end is a low impedance end and the second end is a high impedance end, so the first end FP Resonates at a frequency at which a standing wave is generated where the voltage is at the minimum voltage point (short-circuited end) and the second end is at the maximum voltage point (open end). However, since the characteristic impedance Zb1 of the microstrip line MSL is higher than the characteristic impedance of the strip lines SL1 and SL2 (the relation of Zb1> (Za1, Za2)), the microstrip line as shown in FIG. 8B. A standing wave is generated such that the position of the MSL becomes the maximum voltage (antinode of the voltage intensity distribution). Further, the characteristic impedances Zb2 and Zb3 of the coplanar lines CPL1 and CPL2 are higher than the characteristic impedances Za2 and Za3 of the strip lines SL2 and SL3 (there is a relationship of (Zb2, Zb3)> (Za2, Za3)). ), A standing wave is generated such that the position of the coplanar lines CPL1 and CPL2 becomes the maximum voltage (antinode of the voltage intensity distribution) at a predetermined frequency.

  Therefore, the 1/4 wavelength resonance mode as shown in FIG. 1C and the 3/4 wavelength resonance mode as shown in FIG. 4B do not occur. This is because these resonance modes do not have the maximum voltage in the microstrip line MSL portion and the coplanar lines CPL1 and CPL2. In the second embodiment, the 5/4 wavelength resonance in which the microstrip line MSL portion and the coplanar lines CPL1 and CPL2 portions are at the voltage maximum point Em is the fundamental wave (lowest harmonic) mode. In other words, the strip lines SL1, SL2, SL3, and micro are arranged so that the position where the voltage maximum point Em is in the state of 5/4 wavelength resonance is a high-impedance transmission line, and the region away from the position is a low-impedance transmission line. Strip line MSL and coplanar lines CPL1 and CPL2 are arranged, respectively.

  FIG. 8C is an equivalent circuit diagram showing the high-frequency transmission line 102 as a lumped constant circuit. Near the voltage maximum point Em on the high-frequency transmission line 102, the electric field energy density is high and the magnetic field energy density is low. Therefore, a portion with a high electric field energy density is represented by capacitors C1, C2, and C3, and a portion with a high magnetic field energy density is represented by inductors L1, L2, and L3.

According to the second embodiment, when one wavelength on the high-frequency transmission line 102 is represented by λg and the line length is represented by Lg, the resonance frequency fo3 of the 5/4 wavelength resonance is
fo3 = 5 / (4Lg√εr) × c (c: speed of light) (3)
Are in a relationship. If Lg = 9 [cm] and √εr = 1, then 5/4 wavelength resonance occurs at a high frequency of about 4.2 GHz. Therefore, the cutoff frequency of the high-frequency transmission line 102 is sufficiently higher than the cutoff frequency, for example, in the 2 GHz band, and even a signal in the 2 GHz band can be transmitted with a low insertion loss.

<< Third Embodiment >>
FIG. 9 is a cross-sectional view of each part of the high-frequency transmission line 103 of the third embodiment. FIG. 10 is an exploded perspective view thereof. FIG. 9A is a longitudinal sectional view in the longitudinal direction of the high-frequency transmission line 103. 9B is a cross-sectional view of the first stripline SL1 portion of FIG. 9A, FIG. 9C is a cross-sectional view of the microstrip line MSL portion of FIG. 9A, and FIG. FIG. 9D is a cross-sectional view taken along the second stripline SL2 in FIG.

  As shown in FIG. 9A, the high-frequency transmission line 103 includes a first strip line SL1, a microstrip line MSL, a second strip line SL2, and a connector 41.

  As shown in FIG. 10, the high-frequency transmission line 103 includes four dielectric base materials 31a, 31b, 31c, and 31d. A ground line G2 is formed on the upper surface of the base material 31a. A signal line S1 is formed on the upper surface of the substrate 31b. Two ground lines G1a and G1b are formed on the upper surface of the substrate 31c. A signal terminal 11 and ground terminals 21 and 22 are formed on the upper surface of the substrate 31d. In addition, a via conductor V22 that connects the ground line G2 and the ground terminal 22 is formed in the base materials 31b to 31d. A via conductor V11 that connects the signal line S1 and the signal terminal 11 is formed on the base materials 31c and 31d. A via conductor V21 connecting the ground line G1b and the ground terminal 21 is formed on the base 31d. The high-frequency transmission line 103 is a laminated body of base materials 31a, 31b, 31c, and 31d on which these various conductor lines are formed.

  In the third embodiment, the via conductors V11, V21, and V22 constitute a coplanar line CPL extending in the stacking direction (thickness direction) of the stacked body. The connector 41 is connected to the signal terminal 11 and the ground terminals 21 and 22.

  11A shows the characteristic impedance of each part of the high-frequency transmission line 103, and FIG. 11B shows an example of a standing wave generated in the high-frequency transmission line 103. FIG.

  The characteristic impedances Za1 and Za2 of the strip lines SL1 and SL2 are 50Ω, respectively. The characteristic impedance Zb1 of the microstrip line MSL is 75Ω. The characteristic impedance Zb2 of the coplanar line CPL is 200Ω.

  When an antenna is connected to the first end FP of the high-frequency transmission line 103 and a connector is connected to the second end SP, the first end is a low impedance end and the second end is a high impedance end, so the first end FP Resonates at a frequency at which a standing wave is generated where the voltage is at the minimum voltage point (short-circuit end) and the second end is the voltage maximum point (open end). However, as in the first embodiment, the characteristic impedance Zb1 of the microstrip line MSL is higher than the characteristic impedance of the strip lines SL1 and SL2 (Zb1> (Za1, Za2)), so that FIG. As shown in the figure, a standing wave is generated such that the position of the microstrip line MSL becomes the maximum voltage (antinode of the voltage intensity distribution). Further, since the characteristic impedance Zb2 of the coplanar line CPL is higher than the characteristic impedance of the stripline SL2 (the relation of Zb2> Za2), the position of the coplanar line CPL is the maximum voltage (voltage) as shown in FIG. A standing wave that becomes an antinode of the intensity distribution is generated.

  Therefore, as in the first embodiment, the 3/4 wavelength resonance is the fundamental wave (lowest harmonic) mode.

  FIG. 11C is an equivalent circuit diagram showing the high-frequency transmission line 101 as a lumped constant circuit. As in the first embodiment, the portion with high electric field energy density is represented by capacitors C1 and C2, and the portion with high magnetic field energy density is represented by inductors L1 and L2.

<< Fourth Embodiment >>
FIG. 12 is an exploded perspective view of the high-frequency transmission line 104 of the fourth embodiment. In the third embodiment, a single signal line S1 is provided, but in the fourth embodiment, four signal lines Sa to Sd are provided. That is, the ground line G2 is formed on the base material 31a, the four signal lines Sa to Sd are formed on the base material 31b, and the ground lines G1a and G1b are formed on the base material 31c. Signal terminals 11a to 11d and ground terminals 21 and 22 are formed on the base 31d. In addition, via conductors that connect the ground line G2 and the ground terminal 22 are formed in the base materials 31b to 31d. Via conductors that connect the signal lines Sa to Sd and the signal terminals 11a to 11d are formed on the base materials 31c and 31d. A via conductor that connects the ground line G1b and the ground terminal 21 is formed on the base 31d. The high-frequency transmission line 104 is a laminated body of base materials 31a, 31b, 31c, and 31d on which these various conductor lines are formed.

<< Fifth Embodiment >>
FIG. 13A is a perspective view of the high-frequency transmission line 105 of the fifth embodiment, and FIG. 13B is an exploded perspective view thereof. The configuration of the high-frequency transmission line 105 is the same as that of the high-frequency transmission line 101 shown in the first embodiment. The fifth embodiment particularly shows an example of a high-frequency transmission line having a bent structure.

  Since the microstrip line MSL portion of the high-frequency transmission line 105 only includes the ground line G3 and the signal line S1 as the conductor layer, it is more flexible than the stripline SL1 and SL2 portions and can be bent easily. .

  The high-frequency transmission line 105 is bent at the microstrip line MSL portion shown in FIG. 13A and incorporated in the electronic apparatus. Since the microstrip line MSL only includes the ground line G3 and the signal line S1 as the conductor layer, it is more flexible than the strip lines SL1 and SL2 and can be bent easily.

<< Sixth Embodiment >>
FIG. 14A is a perspective view of the high-frequency transmission line 106 of the sixth embodiment, and FIG. 14B is an exploded perspective view thereof.

  As shown in FIG. 14B, the high-frequency transmission line 106 includes four dielectric base materials 31a, 31b, 31c, and 31d. A ground line G2 is formed on the upper surface of the base material 31a. A signal line S1, a signal terminal 11, and a ground terminal 21 are formed on the upper surface of the base material 31b. Two ground lines G1a and G1b are formed on the upper surface of the substrate 31c. The high-frequency transmission line 106 is a laminate of the base materials 31a, 31b, 31c and the base material 31d on which these various conductor lines are formed. The ground lines G1a, G1b, G2 are connected by via conductors as shown in the figure. The ground terminal 21 is connected to the ground line G2 via a via conductor.

  The signal terminal 11 and the ground terminal 21 constitute a coplanar line CPL, and a connector is connected to this portion. Since the microstrip line MSL portion of the high-frequency transmission line 106 only includes the ground line G2 and the signal line S1 as the conductor layers, it is more flexible than the stripline SL1 and SL2 portions and can be bent easily. . The high-frequency transmission line 106 is bent at the microstrip line MSL portion shown in FIG. 14A and incorporated in the electronic apparatus.

<< Seventh Embodiment >>
FIG. 15 is a perspective view of the high-frequency transmission line 107 according to the seventh embodiment. In this example, the high-frequency transmission line 107 is bent at four bent portions FF1 to FF4. The bent portions FF1 to FF4 of the high-frequency transmission line 107 are microstrip lines or coplanar lines, and the other portions are strip lines. The high-frequency transmission line 107 includes two signal lines, and includes two signal terminals 11 a and 11 b and two ground terminals 21 and 22 at one end of the high-frequency transmission line 107.

  Basically, the microstrip line has two conductor layers, and the coplanar line has one conductor layer. Therefore, the microstrip line has higher flexibility than the strip line and can be bent easily.

  FIG. 16 is a cross-sectional view of the bent portions FF1 to FF4 in the vicinity of the bent portion FF1. The configuration in the vicinity of the other bent portions FF2 to FF4 is the same. In this example, the strip line SLa portion includes ground lines G1a and G2a and a signal line S1. The strip line SLc portion includes ground lines G1c and G2c and a signal line S1. The microstrip line MSLb portion includes a ground line G2b and a signal line S1. The microstrip line MSLb portion is formed thinner than the strip line SLa and SLc portions. However, the interval between the signal line S1 and the ground line G2b is determined so that the characteristic impedance of the microstrip line MSLb is higher than the characteristic impedance of the striplines SLa and SLc.

  In addition, you may comprise between the bending part FF1 to FF2 and between the bending part FF3 to FF4 by a microstrip line or a coplanar line, respectively.

<< Eighth Embodiment >>
FIG. 17 is a partial plan view of the high-frequency transmission line 108 of the eighth embodiment.

  In each of the embodiments shown so far, the transmission mode is converted by connecting transmission lines of different types as transmission lines having different characteristic impedances. However, the characteristic impedance of a predetermined location is changed with the same type of transmission lines. May be. In the example of FIG. 17, a high impedance coplanar line CPLa, CPLc and a low impedance coplanar line CPLb are connected in order. That is, the coplanar line CPLa including the signal line S1a and the ground lines G1a and G2a, the coplanar line CPLb including the signal line S1b and the ground lines G1b and G2b, the signal line S1c and the coplanar line CPLc including the ground lines G1c and G2c are sequentially connected. It is configured.

  Thus, a predetermined characteristic impedance may be obtained by setting the width of the signal line, the interval between the signal line and the ground line, and the like.

<< Ninth embodiment >>
18A is a perspective view of an antenna device 201 according to the ninth embodiment, and FIG. 18B is an exploded perspective view thereof. This antenna device is a device including the high-frequency transmission line 103 and the antenna element ANT shown in FIG. 9 in the third embodiment, that is, an antenna device including a high-frequency transmission line and a connector.

  The base portions 31a to 31d are respectively formed with extension portions 31ae to 31de that expand in a square shape, and spiral coil antennas Ab and Ac are formed as the antenna elements on the extension portions 31be and 31ce, respectively. The outer peripheral end of the coil antenna Ab is connected to the signal line S1, and the inner peripheral end thereof is connected to the outer peripheral end of the coil antenna Ac. The portions where the coil antennas Ab and Ac are formed are sandwiched between the extended portions 31ae and 31de.

  FIG. 19 is an equivalent circuit diagram of the antenna device 201. The characteristic impedance of the antenna element ANT is, for example, 1 to 25Ω, and the characteristic impedance of the connector 41 is, for example, 200Ω. As shown in the third embodiment, since the fundamental wave mode (lowest harmonic mode) on the high frequency transmission line 103 is a 3/4 wavelength resonance mode, the lowest cutoff frequency is a high frequency transmission line having a conventional structure. As compared with the above, the frequency is three times, and a low insertion loss characteristic can be obtained over a wide band.

<< Other embodiments >>
In each of the embodiments described above, a strip line, a microstrip line, and a coplanar line are given as examples of transmission lines having different characteristic impedances. In addition, a coplanar wave guide with ground (Coplanar Waveguide with Ground), a coplanar strip line ( Coplanar Strips) and transmission lines with slot lines can also be applied.

Ab, Ac ... Coil antenna ANT ... Antenna elements C1, C2, C3 ... Capacitors CPL, CPL1, CPL2 ... Coplanar lines CPLa, CPLb, CPLc ... Coplanar lines FF1 to FF4 ... Bending part Em ... Voltage maximum point FP ... First end G1a , G1b, G1c ... ground lines G2, G2a, G2b, G2c ... ground lines G3, G3a, G3b ... ground lines G4a, G4b ... ground lines L1, L2, L3 ... inductor MSL ... microstrip line MSLb ... microstrip line S1 ... Signal lines Sa to Sd ... Signal lines SL1, SL2, SL3 ... Strip lines SLa, SLc ... Strip line SP ... Second end V11 ... Via conductors V1a, V1b ... Via conductors V21, V22 ... Via conductors V2a, V2b ... Via Body 11, 11a, 11b ... Signal terminals 21, 22 ... Ground terminals 31a, 31b, 31c, 31d ... Base materials 31ae, 31be, 31ce, 31de ... Expansion portions 40, 41 ... Connectors 101-108 ... High frequency transmission line 201 ... Antenna apparatus

Claims (7)

In the high-frequency transmission line in which the first end is a low impedance end and the second end is a high impedance end,
A low impedance portion that is a strip line and a high impedance portion that is a microstrip line or a coplanar line, the characteristic impedance of which is higher than that of the low impedance portion, and
A high-frequency transmission line which is bent at the high impedance portion and not bent at the low impedance portion . In the high-frequency transmission line in which the first end is a low impedance end and the second end is a high impedance end,
A low impedance portion that is a strip line and a high impedance portion that is a microstrip line or a coplanar line, the characteristic impedance of which is higher than that of the low impedance portion, and
At least one of the ground electrodes constituting the stripline is not formed in the high impedance portion,
A high-frequency transmission line bent at the high impedance portion. The high-frequency transmission line according to claim 1, wherein a total length of the low impedance portions is longer than a total length of the high impedance portions. 4. The high-frequency transmission line according to claim 1, wherein the low impedance end is an antenna connection end, and the high impedance end is a connector connection end. 5. The low-impedance part and the high-impedance part are composed of a laminate including a plurality of dielectric layers and line conductors,
5. The high-frequency transmission line according to claim 1, wherein the high impedance portion has a smaller number of laminated dielectric layers than the low impedance portion. A high-frequency transmission line according to any one of claims 1 to 4 ,
An antenna element connected to the low impedance end,
The high-frequency transmission line is composed of a laminate including a plurality of dielectric layers and line conductors,
The antenna device, wherein the antenna element is provided integrally with the high-frequency transmission line on the laminate. The high-frequency transmission line according to claim 5 ,
An antenna element connected to the low impedance end,
The antenna device, wherein the antenna element is provided integrally with the high-frequency transmission line on the laminate.

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