EP3236530A1 - Substrate-integrated hollow line filter - Google Patents

Abstract

The invention relates to a substrate-integrated waveguide filter (1) comprising: a substrate-integrated waveguide, formed from a substrate (40), which in each case has a metallic coating (11, 13) on its two flat sides, as well as metallic boundary structures (12) at its lateral edges, - Within the substrate-integrated waveguide several groups of plated-through holes (50) between the metallic coatings (11, 13) of the two flat sides, a metallic coating (11) of one of the two flat sides, which is structured such that it has a plurality of regions (11a) isolated from the surrounding coating (11b), the individual isolated regions (11a) corresponding to the individual groups of Vias (50) are associated such that a single isolated region (11 a) is conductively connected to all vias (50) of the associated group, - A removable metallic lid (20) for covering the structured metallic coating (11), wherein depending on the use of the lid (20) of the SIW filter (1) allows two functions: either a filter function when covering the structured metallic coating (11) by the lid (20) or a transmission function when the lid (20) does not cover the structured metallic coating (11).

Description

The invention relates to a substrate-integrated waveguide filter (English: Substrate Integrated Waveguide (SIW) filter) for use in microwave technology.

With the extension of surface mount technology (SMT) to high frequencies up to the Ka band and beyond, SIW filters have gained in importance, with SMT directly upgrading Surface Mount Device (SMD) surface mount technology PCBs means (eg SMD processors, resistors and circuits).

SIW filters are derived from the basic form of a waveguide. Waveguides as a form of waveguide, such as these are used in particular in radar technology or telecommunications, are increasingly being implemented as a substrate-integrated waveguide (hereinafter "SIW").

The construction of a SIW takes place directly in the board. In this case, the waveguide is bounded with waveguide walls of conductive material, for example, an upper and a lower waveguide wall are each part of a metallization applied above or below the platinum substrate. The height of the waveguide is limited to the height of the substrate. Lateral waveguide walls are formed, for example, by means of plated-through holes, so-called vias or else by internally metallized trenches, so-called grooves, or by a metallization of the outside, provided that the waveguide space coincides with the edge of the board.
Frequently, the board is designed as a multi-layer board (eg tri-plate) and comprises several substrate layers each of a dielectric material between each of which a layer of an electrically conductive material, such as copper, is arranged.

In this way, a stack is formed, wherein the substrate layers can be made of different materials.
In high frequency applications, such as radar, typically at least one substrate layer of RF substrate is provided. Additional substrate layers may be conventional platinum substrates, in particular fiber-reinforced epoxy resin.

Filters are used to avoid unwanted signals or to adjust the signal. From the literature these are known for rectangular waveguides from:

Yi-Chi Shih, "Design of Waveguide E-Plane Filters with All-Metal Inserts," in IEEE Transactions on Microwave Theory and Techniques, vol. 32, no. 7, pp. 695-704, Jul 1984. doi: 10.1109 / TMTT.1984.1132756 , Shih describes for waveguides a simple design process for E-plane filters with all-metal inserts inside the waveguide.

R. Vahldieck, J. Bornemann, F. Arndt and D. Grauerholz, "Optimized Waveguide E-plane Metal Insert Filters For Millimeter-wave Applications," in IEEE Transactions on Microwave Theory and Techniques, vol. 31, no. 1, pp. 65-69, Jan. 1983. Doi: 10.1109 / TMTT.1983.1131430 also describes a design theory for rectangular waveguides with metal feed filters, the application being explained for center frequencies in the range of 15, 33, 68, 75 GHz and for their measured added bandwidth losses for the center frequencies of 15, 33 and 76 GHz 0.2, 06 and 0 , 7 dB.

It is an object of the invention to provide a SIW filter with variable transmission characteristics.

This object is achieved with the SIW filter according to claim 1. Advantageous embodiments of the invention are the subject of dependent claims.

The SIW filter according to the invention comprises: a substrate-integrated waveguide which forms from a substrate which has a metallic coating, eg a copper layer, on its two flat sides, as well as metallic delimiting structures at its lateral edges, eg in the form of vias or grooves / Put. Within the SIW several groups of plated-through holes are arranged between the metallic coatings of the two flat sides. In this case, the metallic coating of one of the two flat sides is structured in such a way that it has several regions insulated from the coating surrounding it, ie the metallic coating has isolated regions in the form of individual metallic islands (hereinafter "island regions") the remaining coating on this flat side have no electrical connection. These individual isolated regions are associated with the individual groups of vias such that a single region is electrically connected to all vias of the associated group.
In other words, all vias of a group are connected to exactly one island region and thus connected to one another via the island region, but there is no electrical connection to the remaining metallic coating on this flat side of the substrate.

• eine Filterfunktion bei Abdeckung der strukturierten metallischen Beschichtung durch den Deckel,
• eine Transmissionsfunktion, wenn der Deckel die strukturierte metallische Beschichtung nicht abdeckt.

In addition, a removable metallic cover is provided to cover the coating structured in this way, and depending on the use of the cover, the SIW filter has two functions:

• a filter function when the structured metallic coating is covered by the lid,
• a transmission function when the lid does not cover the structured metallic coating.

The SIW filter according to the invention has a bandpass characteristic, wherein the filter characteristic is created only by adding a metallic, conductive cover. Without this cover, however, the component has a high transmission. It is thus possible to operate the filter according to the invention in two states and to switch between them in a simple manner.

Fig. 1

einen erfindungsgemäßen SIW-Filter mit seinen Hauptelementen

Fig. 2

eine Detaildarstellung der Umgebung eines isolierten Bereichs der metallischen Beschichtung des erfindungsgemäßen SIW-Filters

Fig. 3

einen erfindungsgemäßen SIW-Filter mit aufgesetztem Deckel

Fig. 4

einen Querschnitt durch den isolierten Bereich des SIW-Filters aus Fig. 2

Fig. 5

einen Längsschnitt durch den isolierten Bereich des SIW-Filters aus Fig. 2

Fig. 6

die Filtercharakteristik eines erfindungsgemäßen SIW-Filters mit aufgelegtem Deckel

Fig. 7

das Transmissionsverhalten eines erfindungsgemäßen SIW-Filters ohne Deckel.

The invention will be described with reference to a concrete embodiment with reference to Fig. 1 to 7 explained in more detail. Show it:

Fig. 1

a SIW filter according to the invention with its main elements

Fig. 2

a detailed representation of the environment of an isolated region of the metallic coating of the SIW filter according to the invention

Fig. 3

a SIW filter according to the invention with an attached lid

Fig. 4

a cross section through the isolated region of the SIW filter Fig. 2

Fig. 5

a longitudinal section through the isolated region of the SIW filter Fig. 2

Fig. 6

the filter characteristic of a SIW filter according to the invention with a lid on

Fig. 7

the transmission behavior of a SIW filter according to the invention without cover.

The basic structure of a SIW filter 1 according to the invention is shown in FIG Fig. 1 shown. Fig. 1 shows the two main modules, the main body 10 of the SIW filter 1 and the lid 20th

The main body 10 of the SIW filter 1 comprises a substrate-integrated waveguide. The SIW includes a substrate 40 (see Fig. 4 ), which has on its two flat sides a metallic coating 11, 13, and metallic boundary structures 12 at its lateral edges.
Such a SIW could, for example, be constructed from the substrate material RO3003 from Rogers Corporation, which comprises an HF substrate with a copper coating its flat sides, wherein the lateral boundary is achieved by vias or by an additional metallization on the side.

The metallic coating 11 on one of the flat sides of the substrate has a structuring as in FIG Fig. 1 shown on. The structuring is designed such that a plurality of isolated regions 11a are formed, wherein the isolated regions 11a provide electrical separation from the surrounding metallization 11b (see FIG Fig. 2 ) on the common flat side. The isolated areas 11a may be understood as a kind of island, which are separated from the remaining areas of the metallic coating on this flat side. The isolated portions 11a are formed in the illustrated embodiment in the form of rectangles having rounded corners. Depending on the field of application and purpose, the shape, number and size of these island areas may differ from the example shown and will be made by the person skilled in the art in accordance with the purpose of the invention.

The fabrication of the isolated areas 11a on the flat side of the board may e.g. by an etching process for producing the structures on the board or by printing these structures on the substrate.

In the cavity formed by the SIW, a plurality of spatially separated groups of plated-through holes 50 are provided to obtain the filter characteristic (see FIG Fig. 4 and 5 ) between the metallic coatings 11, 13 of the two flat sides. In the present example, a Ka-band E-Plane filter was designed using conventional design techniques for a RWG28 waveguide and modified into a SIW filter 1. As will be explained in detail below, the individual groups of vias 50 are each connected to one of the isolated regions 11a. The isolated regions 11a thus virtually form a covering of the vias 50, so that they are in the Fig. 1 are not recognizable. Relative differences in the lengths of the isolated regions 11a correspond to a different number of the underlying vias 50. The isolated regions 11a on the vias 50 form capacitive structures which give the desired filter behavior when the cover 20 is placed on and the behavior of the main body 10 without the cover 20 allow as transmission line.

Fig. 2 shows as a section A of Fig.1 a single insulated area 11a of the metallic coating 11. The isolated area 11a is surrounded by the surrounding metallic coating 11b by a circumferential insulation 60, on which no metallic coating is present, electrically isolated. In the area of the peripheral insulation 60, the substrate 40 present under the metallization 11 is exposed.

In addition, the vias 50 are indicated on the isolated region 11a. With vias, several traces of a printed circuit board can be electrically interconnected. The vias 50 form within the SIW several spatially separated groups between the metallic coatings 11 and 13 of the two flat sides. Each group is connected to one of the isolated areas 11a. In the present case, the vias 50 thus connect the insulated region 11a with the metallic coating 13 on the other flat side of the substrate 40, the vias 50 being connected to one another via the insulated region 11a.

In this case, the vias 50 can be embodied as internally metallized bores or as bores completely filled with conductive material, and this also applies to the lateral boundary structures of the SIW, provided they are designed with vias.

Fig. 3 shows the SIW filter 1 in a state in which a filter function is achieved (with a characteristic according to FIG Fig. 6 ). For this purpose, the lid 20 is placed on the base body 10, specifically on its structured metallic coating 11, whereby an electrical connection between the isolated areas 11a and the surrounding metallization 11b is produced.
When the lid 20 is removed, the characteristic of the structure changes. He now shows a transmission behavior over a wide frequency range. An example of this is in the Fig. 7 shown.

The lid 20 may be formed as a pure metallic layer or have a metallization on that flat side, with which it is placed on the base body 10. The lid 20 may be constrained, e.g. via appropriate hinges or freely placed and removed again.

In the FIGS. 4 and 5 Below, the structure of the SIW filter 1 according to the invention in accordance with the sections Fig. 2 explained. The Fig. 4 shows the cross section B - B of the SIW filter 1 through the insulated area 11 a for the case with the lid 20 attached (bottom figure) and without cover 20 (upper figure).
It can be seen the metallizations 11, 13 on the flat sides of the substrate 40, wherein the upper metallization 11 is structured and in the isolated area 11 a and they surrounding metallization 11 b is divided. This separation is realized by the circumferential insulation 60.
At the lateral edges there is another metallization 12 for forming a closed cavity of the SIW. Alternatively, this metallization could also be achieved by additional vias arranged along the edges of the substrate 40.

The via 50 connects lower 13 and upper 11 metallization levels in the isolated region 11a. It can be seen in the case without cover 20 that there is no electrical connection between the isolated area 11a and the adjacent metallization 11b. This is first produced by the cover 20, which is placed on the upper metallization 11.

Fig. 5 shows the longitudinal section CC Fig. 2B , wherein all vias 50 of an associated group of an isolated area 11a are now recognizable. They respectively connect the lower metallization 13 to the same isolated area 11a. Again, one recognizes the circumferential insulation 60 which separates the isolated region 11a from the remainder of the upper metallization 11. However, this separation is bridged by the cover 20. The distance of an isolated area 11a to the adjacent isolated area (this is in Fig. 5 not shown) - or according to the distance between adjacent groups of vias 50 - is set depending on the wavelength. The vias 50 are surrounded by the substrate 40.

The inventive SIW filter 1 allows two functions, depending on whether this is operated with or without cover 20. In Fig. 6 the associated filter characteristic is shown, where 220 indicates the degree of reflection and 210 the degree of transmission. It can be seen that the graph of the reflection 220 has a high attenuation outside the passband of about 29-30GHz.

In Fig. 7 the characteristic of the SIW filter 1 is shown when used without cover 20 (ie only with the base body 10), wherein 120 indicates the degree of reflection and 110 the degree of transmission. It can be seen that very good transmission over a wide frequency range, in this case over the entire Ka band, is achieved by the structuring according to the invention of one of the two flat sides with the isolated regions 11a. In general, the transmission function of the SIW filter 1 makes it possible to transmit signals across the stop band in the filter function. For example, the filter allows transmission for the entire Ka band, such as out Fig. 7 seen.

Thus, in addition to a selective filter function, the SIW filter 1 according to the invention allows increased flexibility in the application, which can not be achieved by known SIW filters.

With the invention, it is possible to enable in a circuit the choice between low insertion losses and high isolation for defined regions of a spectrum merely by adding or omitting a cover.

In addition, with the invention it is possible to modify the bandwidths in a circuit only by adding or omitting the cover, in which a filter according to the invention is connected in series with a second, conventional filter.

By switching from the filter to the transmission state, any disturbance signal interference within a circuit whose component is the SIW filter 1 according to the invention can be observed.

Claims (6)

Substrate-integrated waveguide filter (1) comprising: a substrate-integrated waveguide, formed from a substrate (40), which in each case has a metallic coating (11, 13) on its two flat sides, as well as metallic boundary structures (12) at its lateral edges, - Within the substrate-integrated waveguide several groups of plated-through holes (50) between the metallic coatings (11, 13) of the two flat sides, characterized in that
the metallic coating (11) of one of the two flat sides is structured in such a way that it has a plurality of regions (11a) insulated from the surrounding coating (11b), wherein the individual isolated regions (11a) correspond to the individual groups of plated-through holes (50). are assigned such that a single isolated area (11a) is conductively connected to all vias (50) of the associated group, and that a removable metallic lid (20) is provided to cover the patterned metallic coating (11), depending on the application the lid (20) of the SIW filter (1) allows two functions: a filter function when the structured metallic coating (11) is covered by the cover (20), - A transmission function when the lid (20) does not cover the structured metallic coating (11). SIW filter (1) according to the preceding claim, characterized in that the transmission function allows a transmission of signals over the entire stop band of the filter function. SIW filter (1) according to the preceding claim, characterized in that the transmission function allows a transmission of signals over the entire Ka band. SIW filter (1) according to one of the preceding claims, characterized in that the cover (20) the insulated areas (11a) with the surrounding metallic coating (11 b) conductively connect. SIW filter (1) according to one of the preceding claims, characterized in that the filter characteristic is set by the arrangement of the individual groups of the plated-through holes (50). SIW filter (1) according to one of the preceding claims, characterized in that the metallic boundary structures (12) are formed by a metallization of the substrate (40) on its side surfaces or by further plated-through holes.

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