Patent Application
20240405427
This disclosure relates generally to a millimeter wave (mmWave) antenna and, more particularly, to a mmWave phased array antenna including a structure of microvias provided between power layers.
Cellular telecommunications companies began deploying fifth generation (5G) radio technology standard for cellular networks in 2019. The 5G radio standard utilizes a higher frequency spectrum than previous generations of commercial communications technologies. MmW phased array antennas are being designed and developed for the 5G protocol that provides increased performance over 4G systems while also reducing costs. 5G mmWave antennas typically require precise manufacturing of printed circuit boards (PCBs) because antenna features on the order of a wavelength are at the limits of manufacturing tolerance of the PCB fabrication process.
5G mmWave antennas are characteristically challenged with both high heat conditions and simultaneously supporting high current application specific integrated circuits (ASIC) requirements that collectively are comparable to high performance microprocessors. This causes a number of concerns about providing adequate copper within a PCB assembly that supports the ASICs used for beamforming integrated circuits (ICs) and at the same time, the increased copper weight reduces accuracy of PCB etching levels typically required for mmWave frequency RF components to be implemented in a PCB suitable for high volume low cost manufacturing. PCB surface area is a premium design consideration, where the aperture of the antenna is to be maximized, while at the same time the overall size of the PCB is to be minimized as a cost reduction effort.
The PCB for mmWave antennas is generally a composition of laminate materials and copper together. The different weights of copper are of different physical thickness, and subsequently the heavier the weight, the greater the current carrying capacity of the layer. Typically, the PCB used for mmWave is fabricated using a solid core, and the repetitively bonding prepreg layers in sequential steps to build up the layers of the PCB. For a typical PCB fabrication, the use of plated through hole (PTH) vias is implemented by drilling through the entire PCB, and plating the hole. This provides an interconnect between layers, but the amount of copper between the top and bottom layers remains constant. In this case, cores and prepregs are alternated throughout the structure, and there is a single pressing of the cores and laminates to fabricate the overall PCB.
The following discussion discloses and describes a mmWave phased array antenna that has particular application to be used in a 5G radio. The antenna includes a PCB structure having a plurality of layers that include a thick copper power layer, a first prepreg layer formed on one side of the thick power layer, a signal layer formed on a side of the first prepreg layer opposite to the thick power layer, a second prepreg layer formed on a side of the signal layer opposite to the first prepreg layer and a thin copper power layer formed on a side of second prepreg layer opposite to the signal layer. A plurality of microvias extend through the first prepreg layer that electrically couple the thick copper layer to the signal layer and a plurality of microvias extend through the second prepreg layer that electrically couple the thin copper layer to the signal layer, where the number of microvias extending through the first prepreg layer is less than the number of microvias extending through the second prepreg layer.
Additional features of the disclosure will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.
The following discussion of the embodiments of the disclosure directed to a mmWave phased array antenna including a structure of microvias provide between power layers is merely exemplary in nature, and is in no way intended to limit the disclosure or its applications or uses. For example, the discussion herein refers to the antenna as being part of a phased array antenna for a 5G radio. However, as will be appreciated by those skilled in the art, the antenna will have other applications.
A signal layer 36 is provided between two prepreg layers 38 and 40, where the layer 38 is adjacent to the power layer 22 and the layer 40 is adjacent to the power layer 24. An array of microvias 42 extend through the prepreg layer 38 and electrically couple the thick power layer 22 to the signal layer 36 and an array of microvias 44 extend through the prepreg layer 40 and electrically couple the thin power layer 24 to the signal layer 36, where the number of the vias 42 is less than the number of the vias 44. By using the microvias 42 between layers of thicker copper, i.e., the layers 22 and 36, the number of the microvias 42 can be reduced, which minimizes the footprint of the transition on the thick power layer 22, and then the microvia density is increased on the thin copper layer 24 to provide more copper to support the high currents typically required for mmWave phased array antennas.
Microvias are implemented individually on each layer in a sequential pressing process. Thus, it is possible to scale up or down the number of vias to compensate for the thickness of copper on each layer. Layers that have thick copper on the dielectric material can use less vias, and thus cause a minimal footprint of the layer transition structure. When transitions approach a layer with thinner copper thickness, the number of microvias can be increased to provide increased surface area and thus lower the current density introduced by the transition onto the thinner copper layer. Since high performance RF materials are characteristically easier to delaminate the copper, this method of increasing the microvia density onto thinner weight layers also provides increased mechanical support through the thermal cycling of the PCB structure, thus increasing the longevity of the PCB structure comparatively. Furthermore, the increase of microvia density to a thinner copper layer adds robustness to the PCB design to protect it from mechanical stress during thermal cycling of the typically high temperature levels of mmWave phased array antennas. This approach can offset the characteristically easier delamination of copper from materials that are low loss at mmWave.
The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/076551 | 9/16/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63261489 | Sep 2021 | US |
