JP4058004B2 - Electrical matching network with transmission lines - Google Patents

Description

  Electrical components often require an electrical matching network to match their circuit environment. Such a matching network can include inductance, capacitance, transmission lines, and is used to substantially match the impedance of the component to the external environment. Such matching networks are often configured as passive integrated networks, and the discrete elements that form the network are integrated together on a substrate. This substrate advantageously forms a support substrate for the component. It is also possible to form the ceramic component from ceramic, attach a compatible element to the ceramic body, and integrate with the component.

  Electrical transmission lines as components of matching networks are often realized on multilayer ceramic substrates. Other elements can be integrated on the ceramic substrate as will be described later. The transmission line is used, for example, in a front-end module for a mobile communication terminal, and can be used as a component of a Pin diode circuit. And here, when combined with others, a phase shift of about 90 ° is achieved. Furthermore, such a transmission line must have the best possible compatibility under a given source impedance and load impedance. The transmission line can also be used in a duplexer. A duplexer is also used in a mobile communication terminal, and connects an antenna to a transmission path and a reception path of the terminal.

  For example, a further requirement for a transmission line in a mobile communication terminal is to make the required area and space as small as possible. In the front end module, for example, the size is much smaller than the fraction of the wavelength on the ceramic substrate, and the phase is shifted by that amount. Since the phase shift should be performed only by lines having a predetermined geometric length, the currently used transmission lines are convoluted and are partly composed of multiple layers. Convolutions and multi-layer configurations that cause line section overlap result in capacitive and inductive coupling between different sections of the line. This changes the suitability and causes an additional phase shift for a single unconvolved ideal line of the same geometric length. Furthermore, the area used and the position of the connection point where the transmission line is connected to the component or other matching network cannot be arbitrarily selected. This is because the area and the position of the connection point depend on other elements of the circuit portion to be integrated.

  An exemplary configuration of the transmission line is a so-called triplate line. In this triplate line, the folded line is guided between two shield earth layers, i.e. two metal planes, and is separated from each of these planes by a ceramic layer. The distance between the upper shield ground plane and the lower shield ground plane is selected accordingly because it affects the impedance characteristics. Due to technical requirements and the need to integrate other elements on a common substrate, the thickness of the ceramic layer cannot be chosen arbitrarily, from a limited number of usable and appropriate layer thicknesses. Must be selected. Therefore, optimal matching is impossible.

  In a known transmission line that saves space, the conductor path is composed of, for example, two layers in a meander shape. The symmetrical arrangement of the two surfaces through which the conductor track extends is selected so that the line impedance is equal on the two conductor track surfaces and corresponds to the source and load impedances. Coupling between individual sections of a conductor track is minimized by: That is, the sections of the conductor paths extending in parallel have a sufficient distance from each other. This spacing is usually larger than the width of the conductor track. Coupling between conductor track sections on different conductor track surfaces is minimized by: That is, the overlapping sections of the two layers are arranged at right angles to each other, or the conductor path section of one conductor path surface overlaps the projection of the conductor path section of the other surface. In order to increase the phase rotation of the transmission line, the geometric length of the conductor track can be increased. This is only possible by bringing the individual sections of the conductor track close to each other when the area is limited. However, this increases the coupling at the line section and degrades the compatibility between the source and the load.

The object of the present invention is to improve the network with transmission lines and to be suitable for further miniaturized components, for example to achieve the desired suitability of 10 dB or more .

  This problem is solved by a network comprising the features of claim 1. Advantageous configurations of the invention are described in the dependent claims.

  The present invention provides a network comprising a transmission line formed on a substrate, the transmission line having a predetermined electrical length. In order to make effective use of the usable area for the transmission line, the conductor path is convoluted, the sections are configured in a straight line, and are connected at right angles to each other. The per se disadvantages resulting from the joining of adjacent sections of the conductor track are taken into account in the present invention by: In other words, the width of the conductor path is different in each section. The inventor recognizes that coupling is affected by changing the width of the individual conductor track sections as desired. Therefore, desired matching can be achieved by appropriately selecting the conductor path width in each section. For example, consider two conductor track segments that are capacitively or inductively coupled to each other, inductive coupling is mitigated by increasing the conductor track width in one of the two conductor track segments. Increasing the conductor path width in one section may further increase parasitic capacitive coupling to adjacent conductor path sections, which itself becomes an obstacle. Therefore, the electrical compatibility of the transmission line is improved by changing the conductor path width of each conductor path section. By selecting the widths of all conductor track sections appropriately and independently of each other, the compatibility can be optimized and precisely adjusted to a desired value. Conventional circuit environments may require matching to, for example, 50Ω.

  According to the present invention, the electrical matching of the transmission line and the network for matching the electric component as a whole can be accurately optimized to a desired value, and the required area of the transmission line is increased. Nor. Further, according to the present invention, even a configuration that causes a coupling that is unacceptable in a known transmission line and thus deteriorates compatibility can be balanced by the present invention. This further reduces the required area of the transmission line and, alternatively or additionally, enables a transmission line geometry that could not be realized before because of its drawbacks. Thus, according to the present invention, the usable area of the substrate can be used more effectively. The reason why the required area does not increase in the present invention is that the geometric length (usually also the electrical length) of the conductor path that is decisive for the degree of phase shift does not change significantly.

  A section of a conductor track is understood to be any part of a conductor track having a predetermined length. Usually, it is easy to define a section between two corner points of a convoluted conductor path for both calculation and transmission line structure.

  Like the conventional transmission line, the transmission line of the present invention can also be constituted by a conductor path that is convoluted with two conductor path surfaces. The two conductor tracks are separated from each other by an insulator, preferably a ceramic layer. A further insulating layer, in particular another ceramic layer, separates the conductor track surface from the shield surface connected to ground.

  The transmission line can also be configured as a triplate line. In this triplate line, the conductor road surface is disposed between two ground surfaces. According to the present invention, an insulating layer that separates two conductor road surfaces can be made thinner than in the case of a known transmission line. The faulty coupling resulting therefrom can be compensated by the present invention. Two conductor track portions extending on different conductor track surfaces are connected to each other by through contact connections.

  The section parallel to the two conductor road surfaces is configured not to overlap. The sections parallel to each other are offset from each other in two planes by at least the minimum length. Intersections between sections on different conductor track surfaces are preferably performed away from the end of the section, preferably in the middle of the conductor track section. If the width of the conductor track changes in individual sections, the ambient conditions are advantageously maintained. Thus, for example, the width of the conductor track sections, as well as the spacing between the conductor track sections parallel to one another, should be kept at a technically minimal value. This value is selected to be 100 μm, for example. However, this minimum distance and minimum width are not the subject of the present invention, and are merely taken into account during optimization as a peripheral condition, and appear as an accurate configuration of the transmission line. Other ambient conditions and minimum values can also be maintained.

  The geometric length of the conductor path of the transmission line is selected so that its electrical length corresponds to a λ / 4 line. The λ / 4 line is necessary when the circuit state must change between “SHORT” and “OPEN”. However, the transmission line of the network of the present invention produces a phase shift different from λ / 4.

  An advantageous impedance matching is 50Ω. This value is necessary in many circuit environments. However, transmission lines and networks can be adapted to other circuit environments other than 50Ω. Impedance matching can be performed in the triplate line by changing the distance between the shield surface and the conductor road surface. However, if the usable layer thickness is not sufficient to adjust the desired impedance on a given substrate, additional separate impedance transformations can be performed and corresponding elements can be provided in the network.

  The network according to the invention is preferably integrated in a multilayer ceramic. This is preferably an LTTC ceramic and is optimized for minimal shrinkage. With such a non-shrinkable ceramic in the LTC configuration (= low temperature cofired ceramic), the network elements can be integrated with high density, and in some cases, the original elements can be integrated into the ceramic. This is because this technique allows to obtain high value ceramics and low loss conductor tracks, and at the same time accurately reproduce the component geometry or network geometry. Usually, however, the substrate of the network is a support substrate for the component, on which the component is fixed and connected in contact, for example made in one step by the SMD process. If the component is an element that operates by acoustic waves, a flip chip configuration can be selected.

  A substrate for a network that can be an integrated network is simultaneously a substrate for a module, in which a plurality of components and the associated network are integrated.

The invention and the method for optimizing the network of the invention will now be described in detail with reference to the drawings and embodiments.
FIG. 1 is a schematic plan view of a known transmission line having a conductor path convoluted in two planes.
FIG. 2 is a schematic cross-sectional view of a transmission line configured as a triplate line.
FIG. 3 is a Smith diagram of a known transmission line.
FIG. 4 is a schematic plan view showing a conductor path of the transmission line of the present invention.
FIG. 5 is a Smith diagram of the transmission line of the present invention.

  A known transmission line will be described in detail with reference to FIGS. These figures are used for illustration only and the scale is not accurate. The known triplate configuration comprises first and second conductor road surfaces LE1, LE2, which are separated from one another by a ceramic intermediate layer. Above and below the first and second conductor road surfaces, shield surfaces ME1 and ME2 that are similarly separated by a ceramic intermediate layer and connected to the ground are arranged, and the shield surfaces are, for example, metallized surfaces. (See FIG. 2). The conductor track surface and the shield surface are preferably arranged symmetrically with respect to each other, so that the distance between the shield surface ME and the adjacent conductor track surface LE is both equal to dE. The distance dE can be different from the distance dL between the two conductor road surfaces LE1 and LE2. In a known transmission line, for example, dE = 125 μm and dL = 95 μm. FIG. 1 shows a state in which the conductor path LE1 is folded on the first conductor path surface. What is indicated by a broken line is a projection of the conductor path LE2 convoluted with the second conductor path surface. This conductor path is composed of a plurality of straight sections, and these sections are connected at right angles. The sections are two conductor road surfaces LE1 and LE2, and are arranged so that straight sections that are parallel to each other do not overlap. The two portions LE1 and LE2 of the entire line are connected to each other in both planes through the through connection DK. At two terminal points T1 and T2, the conductor or transmission line is connected to an external circuit environment, for example a network or a component. The conductor tracks have the same width d0.

  FIG. 3 shows the suitability calculated from a known transmission line in the Smith diagram. The suitability of known transmission lines is clearly inferior to 15 dB when the impedance matching is about 35Ω.

  In the present invention, the width of the individual conductor path sections of one or two conductor path surfaces LE1, LE2 has changed and is particularly increased. As a result, the coupling with the adjacent conductor path section of the conductor path surface LE2 not shown in FIG. 4 which is the same as or below the corresponding conductor path section A1 to A6 is reduced, or the characteristics thereof change. . By increasing the width of the conductor path section A, inductive coupling can be reduced, and conversely, capacitive coupling can be increased. As an example, the widths d3, d4, d5, d6 of the conductor track sections are shown for the corresponding conductor track sections A3, A4, A5, A6. The virtual “original” width of the conductor track is indicated by d0. The optimum matching of the conductor tracks is usually obtained when the widths dx of all the variable conductor track sections Ax take different values. However, the individual conductor track sections may have the same width. This is especially true when the conductor track section does not change relative to the original structure. FIG. 4 shows only the conductor road surface LE1, below which there is a second conductor road surface LE2, which is changed accordingly. As a result, conductor path sections having different widths also exist there.

  FIG. 5 shows a Smith diagram belonging to the transmission line shown in FIG. Comparison with FIG. 3 shows that the electrical compatibility of the transmission line of the present invention is remarkably improved. The present invention has a phase shift of, for example, exactly λ / 4 at about 50Ω. However, the degree of phase shift can be changed correspondingly by extending or shortening the geometric length of the conductor track in one or two planes, and thus the electrical length. Therefore, a phase shift with a value different from λ / 4 is possible.

  The optimization method for matching transmission lines of the present invention is performed as follows. Starting from a conductor track having a section with a constant width, its electrical characteristic value is calculated or simulated. Subsequently, the width of the section is changed, and the electrical characteristic value is newly calculated. The action obtained by this (= matching shift in the Smith diagram as a vector) is stored as the matching degree for the changed section. Subsequently, based on the start structure, the width of the further section is changed, and the electrical characteristic value is newly calculated. In this way, a further matching degree can be obtained. Depending on the problem present and on the action achieved by the individual matching degrees, in some cases there are already two matching degrees (this matching degree is obtained by interpolating the action of each interval and the correspondingly changed width). The desired or necessary matching can be achieved by further varying in efficiency). For a demanding fit, it is necessary to calculate further matching degrees for another interval or for all intervals, the desired matching being formed by addition from the individual matching degrees. In some cases, further matching is finally required for the structure thus obtained. This is because the degree of matching calculated individually may have a reciprocal effect.

  The network of the present invention with a novel transmission line can be used to match any electrical component. It can advantageously be used for passive integrated networks, which are absolutely necessary for further miniaturization of electrical components. A particularly advantageous use for the network of the invention is to electrically match the elements of the front-end module in a wireless communication terminal, for example a mobile phone. Here, in order to maintain the external dimensions already achieved, they must be integrated on the component substrate or front end module substrate.

  In order to accommodate additional network components and to serve their function as component substrates, the substrate is augmented with another layer relative to the layer sequence shown in FIG. The thickness of the substrate and the number of layers required for it depends on the number of network elements and components to be integrated on the substrate. Depending on the components to be realized in the substrate ceramic, the material for the corresponding ceramic layer is also selected.

  In this embodiment, an electrically insulated ceramic is used for the intermediate layer between the two conductor road surfaces LE1 and LE2, and the advantageously low dielectric constant of the ceramic determines the impedance of the line. Since the dielectric constant of the intermediate layer is low, the coupling between the conductor road surfaces is also relaxed. However, according to the present invention, such bonds can be relaxed or used advantageously. The ceramic layer between the conductor road surface LE1 and the shield surface ME1 connected to the ground is also electrically insulated and manufactured. Again, attention should be paid to the corresponding dielectric constant values. Usually, the same ceramic is used for all ceramic layers, including the intermediate layer. However, according to the invention, a ceramic different from the other ceramic layers can be used for the intermediate layer. This is especially to adjust the coupling, which may be desired in the present invention, to the desired value.

  The area used for an individual component is usually determined by other elements that are present or implemented in the same plane as the feedthrough. The present invention provides good matching to any shape area that can be used.

FIG. 1 is a schematic plan view of a known transmission line having a conductor path convoluted in two planes.

FIG. 2 is a schematic cross-sectional view of a transmission line configured as a triplate line.

FIG. 3 is a Smith diagram of a known transmission line.

FIG. 4 is a schematic plan view showing a conductor path of the transmission line of the present invention.

FIG. 5 is a Smith diagram of the transmission line of the present invention.

Claims (11)

A network for electrically matching electrical components, having a transmission line configured on a substrate,
The transmission line has a predetermined electrical length and a plurality of bent electrical conductor paths (LE),
A plurality of linear sections (A 1 to A 6 ) of the electric conductor path (LE) are connected to each other at right angles,
The width of the conductor track in each section is different ,
The electrical conductor path (LE) has two parts (LE1, LE2),
The two parts extend on two planes separated by a ceramic intermediate layer, and the two parts are connected to each other via a through connection (DK) network. The individually width of the interval conductor tracks in (A 1~A6) (LE), disorders coupling between different conductor sections is compensated, the network of claim 1, wherein. The conductor path (LE) bent back multiple times extends in the first plane,
3. A network according to claim 1 or 2, wherein the first plane is parallel to the first plane by at least one ceramic layer and is separated from a shield plane connected to ground. The conductor paths mutually parallel a plurality of sections of (A 1~A6) do not overlap vertically, the section (A 1~A6) as displaced from each other by at least a predetermined minimum length into two planes The network of claim 1 being guided. Are arranged in different planes, with respect to deviation of mutually parallel a plurality of sections (A 1~A6), they are arranged in one plane, being adjacent and mutually parallel plurality of sections (A1 The network according to claim 4 , wherein a minimum length of 100 μm is maintained even for a distance of ~ A6) . All the sections (A 1~A6) has a width (d) corresponding to at least a minimum length, any one network as claimed in claim 1 to 5 of the conductor paths. The transmission line is configured as a triplate line having two shield surfaces (ME) connected to ground,
The network according to any one of claims 3 to 6 , wherein the two ceramic layers arranged between the conductor track surface and the shield surface have the same thickness (dE). Transmission line is configured as a lambda / 4 line, any one network as claimed in claims 1 to 7. Transmission line is matched to 50 [Omega, any one network as claimed in claims 1 to 8. Substrate is a multilayer ceramic and forms a support for the components or modules, any one network as claimed in claims 1 to 9. 11. A network according to claim 10 , wherein the component or module comprises at least one component that operates by acoustic waves.

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