JP4542531B2 - Transmission mode conversion structure - Google Patents

Description

  The present invention relates to a transmission mode conversion structure. Specifically, in order to mount a semiconductor element inside the dielectric waveguide, a TEM mode line is formed integrally with the dielectric waveguide, and the TE mode which is a fundamental mode of the dielectric waveguide It relates to the structure to be joined.

  A dielectric waveguide is a low-loss and small-sized transmission line, and its application to resonators, filters, antennas, and the like has been studied and is being put to practical use. When a high-frequency module is configured using a dielectric waveguide, the dielectric waveguide is a TE mode waveguide, whereas the input / output lines of semiconductor elements and the like are TEM mode conductors such as microstrip and coplanar lines. Since it is a waveguide, it is necessary to provide a connection structure with a planar circuit of a wiring board in a filter or the like composed of a dielectric waveguide. Through this connection structure, the semiconductor device is mounted and connected to a planar circuit on the same wiring board.

  However, since this connection structure becomes a module configuration method using the printed wiring board technology, that is, a connection structure, the advantage of the low loss property of the dielectric waveguide cannot be utilized. Particularly in the millimeter wave band, the use of a macrostrip line or a coplanar line formed on a printed wiring board has a problem that radiation loss increases. If a semiconductor element can be mounted (built in) inside the dielectric waveguide, a high-frequency module that makes the best use of the low-loss characteristics of the dielectric waveguide can be obtained.

For this purpose, it is necessary to integrally form the TEM mode waveguide and the mode conversion structure inside the dielectric waveguide. Until now, the TEM mode waveguide integrally formed inside the dielectric waveguide. Has not been put into practical use, nor has it been proposed.
JP 2005-217601 A JP 2004-187224 A Japanese Patent Laid-Open No. 2002-113112

  The present invention realizes a module having a small monolithic structure utilizing the low loss property of a dielectric waveguide. That is, the present invention provides a mode conversion structure in which a TEM mode waveguide and a mode conversion structure are integrally formed inside a dielectric waveguide, and a semiconductor element can be mounted (incorporated) in the dielectric waveguide.

The present invention solves the above-described problems by forming a dielectric waveguide by bonding dielectric substrates and forming a TEM waveguide and a conversion structure by a conductor pattern formed on the bonding surfaces thereof. . That is, in a transmission mode conversion structure in which four dielectric substrates having conductor patterns formed on the bonding surface are bonded , a coplanar line drawn to one end is provided between two thin dielectric substrates positioned inside. A conductor strip to be formed is converted from a coplanar line to a slot line on the center side, and includes a first conductor pattern in which the width of the slot is widened toward the other end side , and two thin dielectric substrates and outside of them The present invention is characterized in that second and third conductor patterns serving as ground conductors are respectively provided at positions facing the coplanar line of the first conductor pattern between the thick dielectric substrate to be disposed.

  The TEM mode propagating through the coplanar line-shaped waveguide formed inside the dielectric waveguide is converted to the TE mode, which is the fundamental mode of the dielectric waveguide, through the slot line. Since all the lines are covered with the external electrodes of the dielectric waveguide, there is no radiation loss and low-loss conversion is performed. Since a TEM mode waveguide is provided inside the dielectric waveguide, semiconductor elements such as diodes, transistors, and MMICs can be mounted thereon. Since this TEM mode waveguide has a coplanar line shape, it is compatible with flip chip mounting. Since the waveguide portion of the TEM mode is sandwiched between two shield patterns, only the TEM mode can be propagated, so that deterioration of characteristics due to the mixture of a plurality of modes can be prevented.

  Embodiments of the present invention will be described below with reference to the drawings. The transmission mode conversion structure according to the present invention is a dielectric waveguide in which a TEM mode coplanar line is built, and has a rectangular parallelepiped dielectric block 10 as shown in FIG. FIG. 1 is an exploded perspective view of the dielectric block, which includes four dielectric substrates 11 to 14 and three conductor patterns 15-17, 18, and 19 formed therebetween. The dielectric substrate consists of two thick dielectric substrates 11 and 12 located on the outer side and two thin dielectric substrates located on the inner side, and bonded after conductor patterns 15 to 19 are printed on the bonding surface. Are integrated into a block.

  FIG. 2 shows a front view of three conductor patterns. The conductor patterns 15 to 17 located in the center and the two conductor patterns 18 and 19 facing each other across the both sides are between the dielectric substrates. Formed. The conductor patterns 15 to 17 located in the center are formed of three conductor patterns on the left side of the figure. A structure comprising a conductor pattern including a conductor strip 15 and conductor patterns 16 and 17 sandwiching the conductor pattern 15 from both sides in a plane is adopted. The conductor strip 15 located at the center is bent at the center and pulled out to one outer side, and connected to the ground conductor after joining. The conductor patterns 18 and 19 are formed so as to sandwich the conductor strip 15 from both sides at the position of the conductor strip 15 on the left side of the figure, and are present as thin conductor patterns only near the both sides on the right side from the position where the conductor strip 15 disappears. Yes.

  The conductor patterns 15 to 17 provided at the central joint between the dielectric substrates 13 and 14 are regarded as a coplanar line on the left side of the drawing, and can be regarded as a structure converted into a slot line on the way. On the right side from the slot converted position, the slot width is gradually increased in order to obtain matching with the TE mode of the dielectric waveguide. Conductor patterns 18 and 19 provided on other joint surfaces are connected to a ground conductor that covers the dielectric block, and are shielded so as to cover the coplanar line portion, so that only the TEM mode is applied to the coplanar line portion. Can be propagated. By forming a conductor pattern on the bonding surface of the dielectric substrate by printing or the like and then bonding it, a dielectric block having a conductor pattern inside is formed.

  FIG. 4 is a schematic diagram of the electric field distribution seen in the cross section of the waveguide formed inside the dielectric waveguide. (A) shows the TEM mode, and (b) shows the TE mode. In the present invention, the left coplanar line portion shown in FIGS. 1 to 3 is a TEM mode waveguide similar to the coaxial line, and the electric field spreads radially from the central conductor. On the other hand, since the center conductor does not exist in the dielectric waveguide on the right side, the TEM mode does not propagate and becomes a TE mode waveguide, and the electric field mainly includes a vertical component.

  FIG. 5 shows the calculation results of the phase constants of the first and second propagation modes for the case where there is no shield pattern in the cross-sectional structure of FIG. It can be seen that by providing the shield pattern, the high-order mode is cut off at a frequency of 28 GHz or less, and only the first mode (TEM mode) can propagate.

  Moreover, the result of having calculated the characteristic of the conversion structure by electromagnetic field analysis is shown in FIG. In this calculation example, it can be seen that a broadband conversion characteristic with a reflection loss of 20 dB or more is obtained in the frequency range of 20 GHz to 26 GHz. In these calculation examples, a dielectric material having a dielectric constant of 4.5 is used as the dielectric substrate, the thickness of the two dielectric substrates in the center is 0.3 mm, and the thickness of the outer two dielectric substrates is 2.1 mm. As a result, the long side dimension of the dielectric waveguide (block) cross section is 4.8 mm. The short side dimension is 2.5 mm.

  By providing a coplanar line-shaped TEM mode waveguide, a semiconductor element such as a diode, a transistor, or an MMIC can be mounted (built in) inside the dielectric waveguide. FIG. 7 shows an example in which a chip-like semiconductor element 20 is mounted. In this case, a structure is shown in which a part of the dielectric substrate is cut out so that the semiconductor chip can be accommodated in the dielectric waveguide.

The present invention is not limited to the above example, coplanar line in the dielectric block can be applied as long as the slot line and the dielectric waveguide is formed integrally with further dielectric waveguide to coplanar waveguide The wave tube can be connected to other elements and lines.

  According to the present invention, it is possible to use a dielectric waveguide for a high-frequency module, and it becomes easy to realize a small and low-loss high-frequency module in which a semiconductor element is incorporated in the dielectric waveguide.

The exploded perspective view which shows the Example of this invention Front view of conductor pattern The perspective view which shows the Example of this invention Explanation of mode Illustration of phase constant Illustration of conversion characteristics The perspective view which shows the other Example of this invention.

Explanation of symbols

10: Dielectric block
11-14: Dielectric substrate
15-19: Conductor pattern
20: Semiconductor element

Claims (2)

In the transmission mode conversion structure in which four dielectric substrates having conductor patterns formed on the bonding surfaces are bonded,
Between the two thin dielectric substrates located on the inner side, the conductor strip constituting the coplanar line drawn to one end side is converted from the coplanar line to the slot line on the central side, and the width of the slot increases toward the other end side. A first conductor pattern formed,
Between the two thin dielectric substrates and the thick dielectric substrate arranged outside them, the second and third conductor patterns serving as the ground conductors are disposed at positions facing the coplanar lines of the first conductor patterns. A transmission mode conversion structure characterized by having each of them. In the transmission mode conversion structure in which four dielectric substrates having conductor patterns formed on the bonding surfaces are bonded,
Between two thin dielectric substrate located inside the conductor strip constituting the coplanar line is converted from the coplanar line to the slot line, a first conductor width of the slot toward the opposite side of the coplanar line spreads With patterns,
Between the two thin dielectric substrates and the thick dielectric substrate arranged outside them, the second and third conductor patterns serving as the ground conductors are disposed at positions facing the coplanar lines of the first conductor patterns. A transmission mode conversion structure characterized by having each of them.

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