阅读说明：本技术 用于波导的复合基底以及制造复合基底的方法 (Composite substrate for waveguide and method of manufacturing the same ) 是由 S·布尔加 R·F·科普夫 P·鲁里科斯基 M·诺劳齐亚拉布 于 2018-04-27 设计创作，主要内容包括：一种用于具有信号频率的RF信号的波导的复合基底,其中所述复合基底包括至少介电材料的第一层和介电材料的第二层、以及被布置在所述第一层与所述第二层之间的导电材料的至少一个导体层,其中所述至少一个导体层的层厚度小于在所述导体层的所述导电材料内的所述RF信号的趋肤深度的约120％。(A composite substrate for a waveguide of an RF signal having a signal frequency, wherein the composite substrate comprises at least a first layer of dielectric material and a second layer of dielectric material, and at least one conductor layer of conductive material arranged between the first layer and the second layer, wherein a layer thickness of the at least one conductor layer is less than about 120% of a skin depth of the RF signal within the conductive material of the conductor layer.)

1. A composite substrate (100; 100a) for a waveguide (MS1) for a radio frequency, RF, signal (RFS) signal having a signal frequency, wherein the composite substrate (100; 100a) comprises at least a first layer (110) of a dielectric material and a second layer (120) of a dielectric material, and at least one conductor layer (130; 131, 132) of an electrically conductive material arranged between the first layer (110) and the second layer (120), wherein a layer thickness (h 2; h21, h22) of the at least one conductor layer (130; 131, 132) is less than about 120% of a skin depth of the RF signal (RFS) within the electrically conductive material of the conductor layer (130; 131, 132).

2. The composite substrate (100; 100a) according to claim 1, wherein the layer thickness (h 2; h21, h22) of the at least one conductor layer (130; 131, 132) is less than about 50% of the skin depth of the RF signal (RFS) within the conductive material of the conductor layer (130; 131, 132).

3. The composite substrate (100; 100a) according to any one of the preceding claims, wherein the layer thickness (h 2; h21, h22) of the at least one conductor layer (130; 131, 132) is in a range of between about 2% to about 40% of the skin depth of the RF signal (RFS) within the conductive material of the conductor layer (130; 131, 132).

4. A composite substrate (100; 100a) for wave guiding of RF signals, wherein the composite substrate (100; 100a) comprises at least a first layer (110) of dielectric material and a second layer (120) of dielectric material, and at least one conductor layer (130; 131, 132) of electrically conductive material arranged between the first layer (110) and the second layer (120), wherein the layer thickness (h 2; h21, h22) of the at least one conductor layer (130; 131, 132) is less than about 7.8 μm.

5. The composite substrate (100; 100a) according to claim 4, wherein the layer thickness (h 2; h21, h22) of the at least one conductor layer (130; 131, 132) is less than about 100 nm.

6. The composite substrate (100; 100a) according to any one of the preceding claims, wherein the layer thickness (h 2; h21, h22) of the at least one conductor layer (130; 131, 132) is greater than about 2% of the polymeric layer thickness of the at least first layer of dielectric material (110) and second layer of dielectric material (120), or wherein the polymeric conductor layer thickness of the conductor layer (131, 132) is greater than about 2% of the polymeric layer thickness of the at least first layer of dielectric material (110) and second layer of dielectric material (120), if more than one conductor layer (131, 132) is provided.

7. The composite substrate (100; 100a) according to any one of the preceding claims, wherein the at least one conductor layer (130; 131, 132) comprises at least one of the following materials: copper, silver, aluminum, gold, nickel.

8. The composite substrate (100; 100a) according to any one of the preceding claims, wherein the layer thickness (h11, h12) of the first layer of dielectric material (110) and/or the second layer of dielectric material (120) is in a range between about 5nm to about 1000 nm.

9. The composite substrate (100; 100a) according to any one of the preceding claims, wherein a layer thickness of the first layer (110) of dielectric material and/or the second layer (120) of dielectric material is less than about 120% of a skin depth of the RF signal within the conductive material of the conductor layer (130).

10. A waveguide (MS1) for an RF signal (RFS), comprising: the composite substrate (100; 100a) according to any one of the preceding claims, a first conductor (20) arranged on a first surface (102) of the composite substrate (100; 100a), and a second conductor (21) arranged on a second surface (104) of the composite substrate (100; 100 a).

11. A method of manufacturing a composite substrate (100; 100a) for a waveguide for RF signals having a signal frequency, wherein the method comprises the steps of: providing (200) a first layer (110) of dielectric material, providing (210) a second layer (120) of dielectric material, and providing (220) at least one conductor layer (130) of conductive material arranged between the first layer (110) and the second layer (120), wherein a layer thickness of the at least one conductor layer (130) is less than about 120% of a skin depth of the RF signal within the conductive material of the conductor layer (130).

12. A method of manufacturing a composite substrate (100; 100a) for a waveguide for RF signals having a signal frequency, wherein the method comprises the steps of: providing (200) a first layer (110) of a dielectric material having a predetermined first layer thickness (h11), providing (210) a second layer (120) of a dielectric material having a predetermined second layer thickness (h12), and providing (220) at least one conductor layer (130) of an electrically conductive material arranged between the first layer (110) and the second layer (120), wherein the layer thickness (h2) of the at least one conductor layer (130) is determined according to the following equation: h _2 ═ h _11+ h _12) ((epsilon _ eff)/re (epsilon _1)), where h _2 is the layer thickness (h2) of the at least one conductor layer (130), where h _11 is the first layer thickness (h11), where h _12 is the second layer thickness (h12), where re (epsilon _ eff) is the real part of the desired effective permittivity of the composite substrate (100; 100a), where re (epsilon _1) is the real part of the permittivity of the first layer (110) of dielectric material and the second layer (120) of dielectric material.

13. A method of manufacturing a composite substrate (100; 100a) for a waveguide for RF signals having a signal frequency, wherein the method comprises the steps of: -providing (200) a first layer (110) of dielectric material, -providing (210) a second layer (120) of dielectric material, and-providing (220) at least one conductor layer (130) of electrically conductive material arranged between the first layer (110) and the second layer (120), wherein the layer thickness (h 2; h21, h22) of the at least one conductor layer (130; 131, 132) is less than about 7.8 μm.

14. The method according to any of claims 11 to 13, wherein the layer thickness (h 2; h21, h22) of the at least one conductor layer (130; 131, 132) is less than about 100 nm.

15. The method according to any of claims 11 to 14, wherein the layer thickness (h11, h12) of the first layer of dielectric material (110) and/or the second layer of dielectric material (120) is in the range of about 5nm to about 1000 nm.

16. The method according to any of claims 11 to 15, wherein a plurality of conductor layers (131, 132) and at least one additional layer (140) of dielectric material are provided between the first layer (110) and the second layer (120).

Technical Field

The present disclosure relates to a composite substrate for waveguides of Radio Frequency (RF) signals. The present disclosure also relates to a method of manufacturing a composite substrate for a waveguide for RF signals.

Background

Conventional single-layer substrate materials for RF waveguides (such as microstrip lines, etc.) are typically provided by their fabrication with a standard set of dielectric properties, e.g., relative dielectric constant (e)_r) From 2 to 10. This limitation is determined by the costs associated with the development of a substrate having customized values of its dielectric and electrical properties. Disadvantageously, this forces RF designers to choose the appropriate substrate for their own design not based on the "best suited substrate," but rather based on the "worst substrate" for the particular design.

This problem can be somewhat ameliorated by using a multi-layer RF dielectric substrate, where different thicknesses of constituent substrates (dependent substrates), or layers, are stacked together to achieve "effective" dielectric properties of the multi-layer substrate that are appropriate for a particular design/project. Even though this approach may be effective in the development of a range of useful dielectric substrates, it imposes severe limitations on the availability of constitutive substrates, which increases production costs. Furthermore, the conventional multilayer substrates obtained in this way are limited by the attainable value of the dielectric constant, which is determined by the minimum and maximum dielectric constants of the layered stack and their respective heights.

There is therefore a strong need for substrates for RF waveguides having precisely controllable dielectric properties, in particular specific values of their relative dielectric constant, which do not have the above-mentioned disadvantages.

Disclosure of Invention

Various embodiments provide a composite substrate for a waveguide of a radio frequency, RF, signal having a signal frequency, wherein the composite substrate comprises at least a first layer of dielectric material and a second layer of dielectric material, and at least one conductor layer of conductive material disposed between the first layer and the second layer, wherein a layer thickness of the at least one conductor layer is less than about 120% of a skin depth of the RF signal within the conductive material of the conductor layer.

According to applicants' analysis, this configuration can provide a new family of novel dielectric substrates whose dielectric properties can be tailored without being limited by conventional multilayer dielectric substrates. Advantageously, as with conventional multilayer dielectric substrates, the maximum value of the effective dielectric constant (i.e., "macroscopic," total dielectric constant) of the composite substrate media according to embodiments is not limited, for example, by the individual dielectric constants of the constituent dielectric substrates (e.g., silicon dioxide). Therefore, by controlling the layer thickness of the conductor layer, a desired effective relative dielectric constant (. epsilon.) of the composite substrate can be obtained_r)。

According to one embodiment, the signal frequency of the RF signal is the operating frequency at which the composite substrate may be used or conforms to the target system with which the substrate will be used. As an example, a composite substrate according to embodiments may be used as a target system in a microstrip transmission line, and the microstrip transmission may be provided to transmit RF signals at a certain operating frequency (e.g., 20 GHz). In this case, as an example, the composite substrate according to the embodiment may be designed according to the principle based on the embodiment, considering the operating frequency of 20GHz as the "frequency of RF signal" to determine the corresponding skin depth.

According to further embodiments, if a specific operating frequency range of a target system for a composite substrate is considered, a center frequency of the specific operating frequency range or a frequency value within the specific operating frequency range may be used as the "frequency of RF signal" to determine a corresponding skin depth.

As is well known, skin depth (skin depth) is defined as the depth below the surface of an electrical conductor where the current density has dropped to 1/e compared to the current density at the surface of the electrical conductor. It is also well known that skin depth can be determined using the following equation:

where ρ represents electricityThe resistivity of the conductor, where ω denotes the angular frequency of the signal or current, respectively (where ω ═ 2 π f, where f is the signal frequency), where μ ═ f₀μ_rWherein mu₀Is the permeability of free space, where_rIs the relative permeability of the conductor, where ε ═ ε₀ε_rIn which epsilon₀Is the dielectric constant of free space, and wherein_rIs the relative dielectric constant of the conductor.

In some cases, especially for materials significantly smaller than

The equation a1 can also be simplified to:

as an example, using a composite substrate according to embodiments, a waveguide for RF signals may be provided for transmitting RF signals in a range between about 100MHz to about 200GHz or higher.

According to an embodiment, the layer thickness of the at least one conductor layer is less than about 50% of the skin depth of the RF signal within the conductive material of the conductor layer.

According to a further embodiment, the layer thickness of the at least one conductor layer is in a range between about 2% to about 40% of the skin depth of the RF signal within the conductive material of the conductor layer.

A further embodiment features a composite substrate for a waveguide of an RF signal, wherein the composite substrate includes at least a first layer of dielectric material and a second layer of dielectric material, and at least one conductor layer of conductive material disposed between the first layer and the second layer, wherein a layer thickness of the at least one conductor layer is less than about 7.8 μm (microns). According to the applicant's analysis, this configuration surprisingly makes it possible to provide a novel composite substrate for RF signal waveguides, in which in particular the effective relative permittivity of the substrate can be precisely controlled. Further surprisingly, the integration of the at least one conductor layer with a layer thickness of less than about 7.8 μm enables to provide a substrate for a waveguide comprising a relatively large relative permittivity which is in particular not limited by the relative permittivity of the first layer of dielectric material and the second layer of dielectric material of conventional substrates.

A further embodiment features a composite substrate, wherein the layer thickness of the at least one conductor layer is less than about 100 nm.

A further embodiment features a composite substrate wherein the layer thickness of the at least one conductor layer is greater than about 2% of the polymeric layer thickness of the at least first layer of dielectric material and the second layer of dielectric material. According to applicants' analysis, the effective relative permittivity of the composite substrate may be increased, even significantly increased, with such an arrangement compared to a conventional multilayer arrangement of several electrical layers (i.e. without conductor layers).

According to a further embodiment, if more than one conductor layer is provided, it is proposed that the polymeric conductor layer thickness of said conductor layers is more than about 2% of said polymeric layer thickness of said at least first layer of dielectric material and second layer of dielectric material. In the present embodiment, the polymeric layer thickness means a resultant thickness obtained as a sum of thicknesses of respective layers of the same type of material (i.e., conductive or dielectric). For example, if there are two conductor layers in the proposed composite substrate, the polymeric conductor layer thickness corresponds to the sum of the individual thicknesses of the conductor layers. Similarly, if there are 3 dielectric layers in the proposed composite substrate, the polymeric layer thickness of the electrical material corresponds to the sum of the individual thicknesses of the layers of dielectric material.

A further embodiment features a composite substrate, wherein the at least one conductor layer includes at least one of the following materials: copper, silver, aluminum, gold, nickel. It should be noted that these conductor materials relate to the exemplary embodiments. According to further embodiments, other conductor materials may also be used for forming the at least one conductor layer.

A further embodiment features a composite substrate, wherein a layer thickness of the first layer of dielectric material and/or the second layer of dielectric material is in a range between about 5nm and about 1000 nm. According to further embodiments, the layer thickness of the first layer of dielectric material and/or the second layer of dielectric material is not limited to the above ranges, but may comprise other values. According to some embodiments, silicon dioxide may be used as the dielectric material. According to further embodiments, for example, alumina may be used as the dielectric material. According to further embodiments, a ceramic material may be used as the dielectric material. It should be noted that the present disclosure is not limited to these exemplary listed dielectric materials. According to further embodiments, other dielectric materials may also be used to form the dielectric layer.

According to a further embodiment, the layer thickness of the first layer of dielectric material and/or the second layer of dielectric material (or optionally further layer(s) of dielectric material provided) is less than about 120% of the skin depth of the RF signal within the conductive material of the conductor layer. As an example, for determining the skin depth at the respective signal frequency of the RF signal, to determine the dielectric layer thickness as defined above, the above remarks further relating to the operating frequency range of the target system may be used.

A further embodiment features a waveguide for an RF signal that includes a composite substrate according to an embodiment, a first conductor disposed on a first surface of the composite substrate, and a second conductor disposed on a second surface of the composite substrate. As an example, the waveguide may be configured as a microstrip transmission line, wherein the first conductor is a signal conductor, and wherein the second conductor represents a ground plane of the microstrip transmission line.

Advantageously, the field of application of the composite substrate according to the embodiments is not limited to use within microstrip or other RF transmission line configurations. Rather, the composite substrate according to embodiments may be used in any target system where a dielectric substrate is required whose relative permittivity may be adjusted or controlled in the sense of the embodiments.

A further embodiment features a method of manufacturing a composite substrate for a waveguide of an RF signal having a signal frequency, wherein the method includes the steps of: providing a first layer of dielectric material, providing a second layer of dielectric material, and providing at least one conductor layer of conductive material disposed between the first layer and the second layer, wherein a layer thickness of the at least one conductor layer is less than about 120% of a skin depth of the RF signal within the conductive material of the conductor layer. It should be noted that the order of the method steps does not necessarily correspond to the order described above. As an example, first, a first dielectric layer may be provided, then, the conductor layer may be provided over the first dielectric layer, and then, a second dielectric layer may be provided over the conductor layer. Other orders are possible according to further embodiments.

According to some embodiments, preferably, before providing the layers, a frequency range or a center frequency may be determined depending on a frequency of an RF signal for which the composite substrate is to be used, and a layer thickness of at least one of the dielectric layers may be selected depending on the frequency range or the center frequency, respectively. It is also advantageous to take the frequency range or the center frequency into account for determining the layer thickness of the at least one conductor layer, since the skin depth within the conductor material depends on the signal frequency.

In other words, according to a preferred embodiment, in a first step, the frequency range or the center frequency of the target system (e.g. microstrip line) into which the composite substrate according to an embodiment is to be integrated can be determined. Optionally, a specific material for the at least one conductor layer (and optionally also for the dielectric layer) may also be selected, for example copper. Depending on this, the skin depth of the RF signal, e.g. within the frequency range or at the center frequency within the conductor material, may be determined, e.g. by using equation a1 or equation a2 as described above. Thereafter, layer thicknesses of the conductor layers may be determined according to some embodiments, and a composite substrate according to embodiments may be formed by providing the first layer of dielectric material, the second layer of dielectric material, and the at least one conductor layer having the specified thickness determined above.

According to one example, the following fabrication methods and techniques may be used to provide a composite substrate: the dielectric and/or metal layers may be deposited and patterned using standard semiconductor processing techniques. Deposition may be performed using, but is not limited to, the following techniques: chemical vapor deposition, electron beam evaporation, sputter deposition, electroplating, and the like. The layer may be patterned using photolithography techniques and then plasma or wet etched, or deposited and stripped, etc.

A further embodiment features a method of manufacturing a composite substrate for a waveguide of an RF signal having a signal frequency, wherein the method includes the steps of: providing a first layer of a dielectric material having a predetermined first layer thickness, providing a second layer of a dielectric material having a predetermined second layer thickness, and providing at least one conductor layer of a conductive material disposed between the first layer and the second layer, wherein the layer thickness of the at least one conductor layer is determined according to the following equation: h _2 ═ h _11+ h _12) × (re (epsilon _ eff)/re (epsilon _1)), where h _2 is the layer thickness of the at least one conductor layer, where h _11 is the first layer thickness, where h _12 is the second layer thickness, where re (epsilon _ eff) is the real part of the desired effective permittivity of the composite substrate, where re (epsilon _1) is the real part of the permittivity of the first layer of the dielectric material and the second layer of the dielectric material.

A further embodiment features a method of manufacturing a composite substrate for a waveguide of an RF signal, wherein the method includes the steps of: providing a first layer of dielectric material, providing a second layer of dielectric material, and providing at least one conductor layer of conductive material disposed between the first layer and the second layer, wherein a layer thickness of the at least one conductor layer is less than about 7.8 μm.

The dependent claims provide further advantageous embodiments.

Drawings

Other features, aspects, and advantages of the illustrative embodiments are presented in the following detailed description, with reference to the drawings, in which:

figure 1 schematically illustrates a front view of a composite substrate according to one embodiment,

figure 2 schematically shows a front view of a waveguide for radio frequency signals according to one embodiment,

figure 3 schematically shows a side view of the composite substrate according to figure 1,

figure 4 schematically shows a simplified flow diagram of a method according to an embodiment,

figure 5A schematically shows the relative permittivity with frequency according to one embodiment,

figure 5B schematically shows the loss tangent with frequency according to one embodiment,

figure 6 schematically illustrates a front view of a composite substrate according to another embodiment,

FIG. 7 schematically shows a front view of a conventional multilayer substrate, an

FIG. 8 shows a table including dielectric constants according to one embodiment.

Detailed Description

Fig. 1 schematically shows a front view of a composite substrate 100 for waveguide of a radio frequency RF signal. The composite substrate 100 comprises a first layer 110 of a dielectric material, a second layer 120 of a dielectric material, and at least one conductor layer 130 of a conductive material arranged between said first layer 110 and said second layer 120. The layer thickness h2 of the at least one conductor layer 130 is less than about 120% of the skin depth of the RF signal within the conductive material 130 of the conductor layer. This advantageously enables the provision of a composite substrate 100 having an effective relative permittivity that can be controlled within a relatively large range of values, as opposed to conventional multilayer substrates comprising a plurality of dielectric layers. Also, advantageously, as with conventional substrates, the maximum value of the effective relative permittivity of the composite substrate 100 is not limited by the properties of the dielectric material layer, but may be affected by altering the properties of the conductor layer 130.

Fig. 2 schematically shows a front view of a waveguide MS1 for RF signals according to one embodiment. Currently, the waveguide MS1 is configured as a microstrip transmission line that includes a first conductor 20 disposed on a first surface 102 (e.g., the top surface in fig. 2) of the composite substrate 100, and a second conductor 21 disposed on an opposing second surface 104 (e.g., the bottom surface in fig. 2). The first conductor 20 may form a signal conductor, as is known in the art, and the second conductor 21 may form a ground plane, as is known in the art. Since the dielectric properties, in particular the relative dielectric constant, of the composite substrate 100 according to embodiments can be flexibly and precisely configured in a wide range of values, the microstrip waveguide MS1 can be flexibly adapted to the desired field of application. In particular, by controlling the relative permittivity of the composite substrate 100 employed within the waveguide MS1 according to fig. 2, the characteristic impedance of the waveguide MS1 may also be flexibly configured in accordance with the principles of the embodiments.

Returning to fig. 1, according to a preferred embodiment, the layer thickness h2 of the conductor layer 130 may be less than about 50% of the skin depth of RF signals within the conductive material of the conductor layer 130. According to further embodiments, the layer thickness h2 may even be in the range of about 2% to about 40% of the skin depth of RF signals within the conductive material of the conductor layer 130.

As an example, if the composite substrate 100 according to fig. 1 is to be provided to a microstrip transmission line MS1 as exemplarily shown in fig. 2, and if the microstrip transmission line MS1 is to be used for transmission of RF signals transmitted at a frequency of 1GHz (gigahertz), further assuming that copper is used as the conductive material of the conductor layer 130 (fig. 1), the skin depth of the 1GHz RF signal within the copper material may be determined to be about 2.06 μm. Thus, according to an exemplary embodiment, the layer thickness h2 is selected to be 120% by 2.06 μm — 2.472 μm. According to another exemplary embodiment, the layer thickness h2 may be selected to be 10% x 2.06 μm-0.206 μm-206 nm (nanometers). Of course, other values of layer thickness may be provided according to further embodiments.

According to further exemplary embodiments, the layer thickness h2 of the conductor layer 130 may be selected to be about 10% of the corresponding skin depth.

Fig. 3 schematically shows a side view of the microstrip transmission line MS1 according to fig. 2. From this side view, the first conductor 20 and the ground plane conductor 21 may be identified, as well as the composite substrate 100 according to the embodiment arranged therebetween. Also indicated in fig. 3 in the form of block arrows is a radio frequency signal RFS, which may for example comprise a signal frequency of about 2 GHz.

In general, by employing principles in accordance with embodiments, a composite substrate 100 suitable for RF signals in a frequency range of about 100MHz (megahertz) to about 200GHz or higher may be provided.

According to another embodiment, the layer thickness h2 of the conductor layer 130 (fig. 1) may be less than about 7.8 μm, which yields suitable results for an effective relative permittivity over a wide frequency range of RF signals.

Further particularly preferred embodiments provide for a layer thickness h2 of the at least one conductor layer 130 of less than about 100 nm.

According to a further embodiment, the layer thickness h11 of said first layer 110 (fig. 1) of dielectric material is in a range between about 5nm and about 1000 nm. According to a further embodiment, the layer thickness h12 of said second layer 120 (fig. 1) of dielectric material is in a range between about 5nm to about 1000 nm.

According to some embodiments, the at least two layers 110, 120 of dielectric material of the composite substrate 100 may comprise the same or at least similar thickness values, i.e. h 11-h 12.

According to further embodiments, the at least two layers 110, 120 of dielectric material of the composite substrate 100 may comprise different thickness values h11, h 12.

Further embodiments provide that the layer thickness h2 (fig. 1) of the at least one conductor layer 130 is greater than about 2% of the polymeric layer thickness of the at least first layer 110 of dielectric material and the second layer 120 of dielectric material. According to applicants' analysis, for this range of thicknesses of the conductor layer 130, a significant change in the effective relative permittivity of the composite substrate 100 can be achieved. For example, if the thickness of the conductor layer 130 is greater than about 30% of the thickness of the polymeric layer of the dielectric layers 110, 120, the effective relative permittivity of the composite substrate 100 thus obtained may even be increased. However, according to other embodiments, as described above, the layer thickness h2 of the conductor layer 130 may preferably not exceed 120% of the skin depth for the RF signal frequencies and the particular conductor material under consideration.

However, according to further embodiments, the layer thickness h2 of the conductor layer 130 may exceed 120% of the skin depth for the RF signal frequencies and the particular conductor material under consideration.

As an example, if the dielectric layers 110, 120 each comprise a layer thickness of 20nm, the polymeric layer thickness of the dielectric layers 110, 120 amounts to 40 nm. According to this embodiment, a layer thickness h2 of more than about 2% of 40nm is proposed, i.e. h2 > 0.8 nm.

According to further embodiments, more than one conductor layer may be provided to the composite substrate. This is exemplarily illustrated by a further embodiment 100a according to fig. 6.

The composite substrate 100a includes a first (i.e., top) layer 110 of dielectric material and a second (i.e., bottom) layer 120 of dielectric material, similar to the configuration 100 of fig. 1. In contrast to fig. 1, however, the composite substrate 100a according to fig. 6 comprises at least two conductor layers 131, 132, wherein at least one further dielectric layer 140 is provided between the at least two conductor layers 131, 132.

Bracket 150 indicates that additional conductor layers and/or additional dielectric layers may also be provided within composite substrate 100a according to additional embodiments.

According to a preferred embodiment, when providing a composite substrate having more than three layers, as shown in fig. 6, additional layers are preferably added such that for each additional conductor layer 132, a further dielectric layer 140 is provided which is arranged adjacent to said further conductor layer 132. However, according to further embodiments, this need not be the case. In other words, according to further embodiments, two or more conductor layers may also be arranged within the composite substrate directly adjacent to each other. Similarly, according to further embodiments, two or more dielectric layers may also be arranged within the composite substrate directly adjacent to each other. This also applies to the top and bottom layers. In other words, adjacent to the dielectric layer 110 and/or the bottom dielectric layer 120, instead of placing a conductor layer directly adjacent to the first layer 110 and/or the second layer 120, further dielectric layers may be provided.

According to another preferred embodiment, if more than one conductor layer 131, 132 is provided, see for example fig. 6, it is proposed that the polymeric conductor layer thickness h21+ h22 of said conductor layers 131, 132 is greater than about 2% of said polymeric layer thickness h11+ h12+ h13 of said at least first layer of dielectric material 110 and second layer of dielectric material 120 (currently, three dielectric layers 110, 120, 140 are present, so the polymeric layer thickness of said dielectric layers amounts to h11+ h12+ h 13).

According to a further embodiment, the at least one conductor layer comprises at least one of the following materials: copper, silver, aluminum, gold, nickel, etc. (other conductive or metallic materials are also possible according to further embodiments). According to some embodiments, the respective conductor layers 131, 132 may also be provided using different said or even other conductive materials.

When providing a composite substrate according to such embodiments that takes into account the skin depth of the RF signal within the conductive layers 130, 131, 132, the respective resistivity or conductivity of the conductive material used may be taken into account to determine the skin depth as well as the frequency (or center frequency) of the RF signal.

Fig. 4 schematically shows a simplified flow diagram of a method according to an embodiment. The method comprises the following steps: providing 200 a first layer 110 (fig. 1) of a dielectric material, providing 210 a second layer 120 of a dielectric material, and providing 220 at least one conductor layer 130 of a conductive material disposed between the first layer 110 and the second layer 120, wherein a layer thickness of the at least one conductor layer 130 is less than about 120% of a skin depth of the RF signal within the conductive material of the conductor layer 130. As mentioned above, another sequence of providing steps 200, 210, 220 is also contemplated, such as first providing the second dielectric layer 120 as a bottom layer of a composite substrate, then providing the at least one conductor layer 130 on a top surface of the second dielectric layer 120, and then providing the first dielectric layer 110 on a top surface of the conductor layer 130. Other orders of providing steps are also possible according to further embodiments.

According to a preferred embodiment, preferably before providing any of the steps 200, 210, 220, a further optional step 198 may be performed, the step 198 comprising: the frequency range or center frequency is determined according to the frequency of the RF signal for which the composite substrate 100, 100a to be manufactured is to be used, and optionally the layer thickness of at least one of the dielectric layers may be selected according to the frequency range or the center frequency, respectively. Also optionally, in the above step 198, the frequency range or the center frequency may be taken into account to determine the layer thickness of the at least one conductor layer, since the skin depth within the conductor material depends on the signal frequency.

In other words, according to a preferred embodiment, in said optional step 198, the frequency range or the center frequency of the target system (e.g. the microstrip line MS1) into which the composite substrate 100 according to an embodiment is to be integrated may be determined. Optionally, a specific material for the at least one conductor layer 130, such as copper, may also be selected. Depending on this, the skin depth of the RF signal RFs within the frequency range or at the center frequency, e.g. within the conductor material, may be determined, e.g. by using equation a1 or equation a2 as described above. Thereafter, layer thicknesses of the conductor layers may be determined according to embodiments, and a composite substrate according to embodiments may be formed by providing the first layer of dielectric material, the second layer of dielectric material, and the at least one conductor layer having a specified thickness as determined above.

According to further embodiments, the determination of the layer thickness of the conductor layer 130 may also be performed within the associated step 220 of providing said conductor layer. As an example, the dielectric layers 110, 120 may be provided before the step 220, and at this stage, the layer thickness of the conductor layer 130 does not have to be provided or determined already.

According to a further particularly preferred embodiment, the layer thickness of at least one dielectric layer 110, 120 of the composite substrate 100 or the polymeric layer thickness of some or all of the dielectric layers 110, 120, 140 is taken into account when determining the layer thickness of the conductor layer 130.

Some embodiments feature a method of manufacturing a composite substrate for a waveguide of an RF signal having a signal frequency, wherein the method includes the steps of: providing 200 a first layer 110 of a dielectric material having a predetermined first layer thickness h11, providing 210 a second layer 120 of a dielectric material having a predetermined second layer thickness h12, and providing 220 at least one conductor layer 130 of a conductive material arranged between the first layer 110 and the second layer 120, wherein the layer thickness h2 of the at least one conductor layer 130 (fig. 1) is determined according to the following equation: h _2 ═ h _11+ h _12) × (re (epsilon _ eff)/re (epsilon _1)), where h _2 is the layer thickness (h2) of the at least one conductor layer 130, where h _11 is the thickness h11 of the first layer, where h _12 is the thickness h12 of the second layer, where re (epsilon _ eff) is the real part of the desired effective permittivity of the composite substrate 100, where re (epsilon _1) is the real part of the permittivity of the first layer 110 of dielectric material and the second layer 120 of dielectric material.

A further embodiment features a method of manufacturing a composite substrate 100 for a waveguide of an RF signal, wherein the method includes the steps of: providing 200 a first layer 110 of a dielectric material, providing 210 a second layer 120 of a dielectric material, and providing 220 at least one conductor layer 130 of a conductive material arranged between the first layer 110 and the second layer 120, wherein the layer thickness of the at least one conductor layer 130 is less than about 7.8 μm.

Further embodiments provide that the layer thickness h2, h21, h22 of the at least one conductor layer 130, 131, 132 is less than about 100 nm.

Further embodiments provide that the layer thickness h11, h12 of the first layer of dielectric material 110 and/or the second layer of dielectric material 120 is in the range between about 5nm to about 1000 nm. According to a further embodiment, other value ranges of the layer thicknesses h11, h12 of the first layer 110 of dielectric material and/or the second layer 120 of dielectric material (within and/or outside of, and/or overlapping with, the above ranges) are also possible.

Further embodiments provide that a plurality of conductor layers 131, 132 and at least one additional layer 140 of dielectric material are provided between the first layer 110 and the second layer.

As mentioned above, the order of the method steps of the method of manufacturing a composite substrate according to embodiments may be changed with respect to each other, wherein it may be preferred to compose a composite substrate 100, 100a comprising a plurality of layers from a bottom layer to a top layer, and vice versa, depending on the specific technology used for the manufacturing.

In the following, the theory of dielectric substrates and the propagation of electromagnetic waves in relation to conductors comprising composite materials for such waveguides and the waveguide MS1 (fig. 2) is discussed.

First, consider a conventional multilayer substrate MLS1 as shown on the left side of FIG. 7. It can be seen that up to n dielectric layers are stacked on top of each other, wherein each layer is formed by its thickness hi and its dielectric properties epsilon_riAnd tan (delta)_i) Definitions, where i ═ 1, … …, n.

On the right half of fig. 7, a front view of a substrate MLS1 'is shown, wherein the substrate MLS1' is single-layered, i.e. composed of a single-layered dielectric material, and has the same macroscopic dielectric properties as the multi-layered substrate MLS 1. In particular, the effective relative permittivity of the substrate MLS1' is the same as that of the multilayer substrate MLS 1.

According to one example, the effective macroscopic dielectric properties of the multilayer dielectric substrate MLS1 of fig. 7 can be found by applying gauss's law. Mathematically, the dielectric constant of the layered substrate is expressed as:

wherein the content of the first and second substances,

the loss tangent corresponding to the complex dielectric constant is

And

as can be seen from (equation 1), the combination of substrate layers having different dielectric properties and/or substrate heights can provide a customized dielectric substrate. However, this conventional solution has been toThe cost is high since it requires a variety of different constituent dielectric materials, which limits its usefulness. Furthermore, the multilayer substrate MLS1 obtained in this way is limited by the attainable value of the dielectric constant, which is determined by the minimum and maximum dielectric constants of the stack and their respective heights.

Therefore, a method capable of solving the above two disadvantages is required. The method is provided in the form of an embodiment as described above and as described in further detail below.

To further explain the details of the idea behind the embodiments, the propagation constant in the conductor is first considered. According to one embodiment, the expression for the propagation constant in a conductor is given below

Wherein

Representing skin depth, see also equation a2 above. The skin depth represents the depth below the conductor surface where the current density has dropped to 1/e (0.37) of its value at the conductor surface. The relationship shown by (equation 2) indicates that a wave propagating in a conductor varies in both amplitude and phase. The total variation in the propagation characteristics depends on the thickness of the metal, i.e.,

γ_t＝γ_m·d_m(equation 3) of the above-mentioned formula,

wherein d is_mRepresenting the thickness of the conductor. As an example, if the thickness of a conductor is much greater than the skin depth, an electromagnetic wave passing through the conductor is not only greatly attenuated, but its phase constant is also greatly affected according to (equation 2). As yet another example, for practical purposes, a conductor thickness between 3 δ and 5 δ is sufficient to almost completely attenuate EM waves. However, this presents a problem: as the examples suggest, what will the EM waves happen if the conductor thickness is well below the skin depth?

To provide a satisfactory answer to this problem and to explain the principle according to an embodiment, consider the real part of the equivalent permittivity of (equation 2), which can be written as:

it can be understood from (equation 4) that the dielectric constant of the conductor is not constant but depends on various parameters. That is, it depends linearly on the electrical conductivity σ and the magnetic permeability μ, whereas it depends inversely linearly on the angular frequency. At lower frequencies, the dielectric constant of standard conductors is high. The table as shown in fig. 8 summarizes the dielectric constants obtained using (equation 4) for different metals (silver, copper, and aluminum) at frequencies of 1GHz, 5GHz, and 20GHz according to some exemplary embodiments.

From this table, it can be seen that the obtained value of the dielectric constant is very high. In view of equation (1), according to embodiments, this may have a large effect on the effective dielectric constant of the multilayer substrate according to embodiments without significantly affecting the overall loss tangent. To demonstrate this, consider below a three-layer structure, i.e. a composite substrate, similar to fig. 1.

The contemplated structure based on fig. 1 shows that the two dielectric layers 110, 120 are "sandwiched" on a relatively thin, preferably subcutaneous, depth conductor 130. The structure of the figure is used to derive the composite EM propagation characteristics according to the embodiments, from which the effective dielectric properties of the medium formed in this way are derived. The composite substrate 100 of fig. 1 may also be considered as a parallel plate waveguide PPWG, which according to one embodiment may be entirely determined by its thickness, while for the following considerations (and in this respect deviating from the actual composite structure 100 according to an embodiment) it is assumed that its x and y dimensions are infinite (the x dimension corresponds to the horizontal direction of fig. 1 and the y dimension corresponds to the direction perpendicular to the drawing plane of fig. 1). According to one embodiment, the final expression for the composite effective dielectric properties was found for the TM wave (c:

) Of the Helmholtz equation in a passive medium

After a lengthy derivation (the individual steps of which are omitted here for the sake of clarity), a solution can be obtained for an effective medium according to the present embodiment consisting of two dielectric layers 110, 120 and one thin conductor layer 130.

Wherein

(ε₀Is the dielectric constant of a vacuum), and k₀Is the propagation constant in free space

Where c is the speed of light.

As an example of the possibility of tuning the dielectric properties using the subcutaneous depth conductor 130 according to some embodiments, fig. 5A shows when the dielectric material for the layers 110, 120 is of thickness h11, h12 of 10nm and

and the effective dielectric constant characteristic obtainable in the case when the thickness h2 of the copper layer 130 varies between 10nm and 50 nm. Of course, other dielectric materials for the layers 110, 120, 140 may be used according to further embodiments. Additionally, according to further embodiments, other conductors may be used for layer 130, such as gold, nickel, aluminum, or other conductors.

Curve C1 of fig. 5A shows the effective dielectric constant with frequency f of GHz of the composite substrate 100 (fig. 1) for a conductive layer thickness h2 of 10nm (nanometers). Curve C2 shows the effective dielectric constant with frequency for a conductive layer thickness h2 of 20nm, curve C3 for h 2-30 nm, curve C4 for h 2-40 nm, and curve C5 for h 2-50 nm. As is apparent from fig. 5A, the dielectric properties of an effective multilayer substrate 100 according to an embodiment remain substantially constant over the indicated frequency range. It is important to note that according to one embodiment, the dielectric properties of the active substrate 100 may be modified, for example, by varying the thickness h2 of the conductor layer 130 (fig. 1), without significantly affecting the loss tangent of the overall dielectric medium 100.

The loss tangent tan _ delta (same scaling as in fig. 5A) with frequency is exemplarily shown for the above five conductor thickness values ranging from 10nm (see curve C1 'of fig. 5B) to 50nm (see curve C5' of fig. 5B).

Further, advantageously, the upper limit value of the effective dielectric constant of the substrate according to the embodiment is not limited by the dielectric constant of the constituent dielectric substrate (silicon dioxide in this case), as in the case of the conventional multilayer dielectric substrate MLS1 (see fig. 7). In contrast, according to embodiments, the dielectric constants of the constituent dielectric substrates 110, 120 only indicate the lowest possible value of the effective dielectric constant of the entire composite substrate 100, while its loss tangent may be assumed to be the overall loss tangent of the proposed effective dielectric substrate.

Thus, a new family of novel dielectric substrates 100, 100a is shown in accordance with the principles of the embodiments, the dielectric properties of which can be tailored without the limitations imposed by the conventional multilayer dielectric substrate MLS1 of FIG. 7.

Equation (6) may also be simplified where the dielectric loss tangent of the constituent dielectric layers is low (below 1e-4 in the present case), according to some embodiments. In this case, the effective dielectric constant of the multilayer substrate becomes

According to these embodiments, the loss tangent of the obtained composite substrate may be substantially equal to the loss tangent of the constituent dielectric substrates 110, 120. Equation (7) obtained according to some embodiments is important because it carries the following statement: of particular importance to the manipulation of the dielectric properties of the composite structure 100 according to some embodiments is the ratio of the thickness or cross-sectional area (e.g., h) of the layers 130 and 110, 120₂/2h₁) Rather than the conductivity of the conductor layer 130. If a thicker dielectric base is desiredThis may be of great significance since according to a further embodiment, see fig. 6, several or more relatively thin dielectric and conductor layers may be deposited, for example one after the other, until the desired total substrate thickness is obtained. In these embodiments, the composite dielectric properties are determined by the ratio of the total cross-sectional surface area occupied by the dielectrics 110, 120, 140 and the conductor 130.

In summary, the following aspects may be achieved in particular according to the principles of the embodiments:

1. the dielectric properties of the multilayer substrate 100, 100a are effectively manipulated by using relatively thin (e.g., subcutaneous depth or a range up to about 120% of skin depth) conductors 130.

2. According to applicants' analysis, the dielectric properties of the multilayer substrate 100 according to some embodiments depend primarily on the ratio of the total cross-sectional surface area of the dielectric and conductor (or, if all layers comprise the same width, the corresponding layer thickness), rather than the electrical conductivity of the conductor.

3. According to some embodiments, the conductor layers may preferably have a thickness of less than 120% of the skin depth, more preferably less than the skin depth (i.e. less than 100% of the skin depth), and according to further embodiments their thickness (not to be confused with the ratio of the cross-sectional areas of the dielectric and the conductor) may affect the higher frequencies until they can be used.

According to a particularly preferred example, the higher frequency of the RF signal RFs to be used with the substrate according to this example should be a frequency at which the conductor thickness h2 is about 10% of its skin depth at that particular frequency. As another particularly preferred example, a copper conductor layer 130 having a thickness h2 of 20nm may correspond to 10% of the skin depth of 200nm at 100GHz, for example.

In summary, principles according to embodiments allow for the creation of custom RF substrates 100, 100a with low insertion loss (low loss tangent) and arbitrary values of dielectric constant, without the limitations of the constituent dielectric layers, whereas existing conventional multilayer dielectric solutions are particularly limited in their ability to produce high and low loss tangent values. The principles according to the embodiments do not have such limitations. For example, the loss tangent of the effective multilayer substrate 100, 100a obtained according to the embodiment is the loss tangent of the constituent dielectric 110, 120, 140, and the effective dielectric constant thereof can be controlled by the thickness h2(h21, h22) of the conductive layer 130, 131, 132.

Furthermore, according to some embodiments, a relatively thick substrate stack 100a may be obtained by providing several or more conductive layers 131, 132, for which the above principles apply, and preferably an intermediate dielectric layer 140 therebetween.

The specification and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.

It will be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

Those skilled in the art will readily recognize that the steps of the various above-described methods may be performed by a programmed computer. Some embodiments are also intended herein to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions for performing some or all of the steps of the above-described methods. The program storage device may be, for example, a digital memory, a magnetic storage medium such as a magnetic disk and magnetic tape, a hard disk drive, or an optically readable digital data storage medium. Embodiments are also intended to cover computers programmed to perform the steps of the above-described methods.

It will be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.