WO2009052029A1

WO2009052029A1 - Multi-layer compact, embedded antennas using low-loss substrate stack-up for multi-frequency band applications

Info

Publication number: WO2009052029A1
Application number: PCT/US2008/079561
Authority: WO
Inventors: Debabani Choudhury; Seong-Youp Suh
Original assignee: Intel Corporation
Priority date: 2007-10-18
Filing date: 2008-10-10
Publication date: 2009-04-23
Also published as: CN101828301A; EP2201642A1; JP2011501570A; JP5212871B2

Abstract

Multi-band Front End Modules (FEMs) incorporate a multi-layer plastic substrate stack-up where metal layers are patterned on substrate layers in the stack-up to provide a compact, monopole-type antenna.

Description

MULTI-LAYER COMPACT, EMBEDDED ANTENNAS USING LOW-LOSS SUBSTRATE STACK-UP FOR MULTI-FREQUENCY BAND APPLICATIONS

Technological developments permit digitization and compression of large amounts of voice, video, imaging, and data information. The need to transfer data between devices in wireless mobile radio communication requires reception of an accurate data stream at a high data rate. It would be advantageous to provide antennas that allow radios to handle the increased capacity while providing an improved quality that operate in accordance with different standards and frequency bands. It would also be advantageous to provide mobile internet devices with an increasing smaller form factor that incorporate integrated, compact, good performance antennas.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

FIG. 1 shows a wireless communications device that includes one or more antenna in accordance with the present invention that allows radio communication;

FIG. 2 and 3 illustrate a compact, multi-layer monopole-type antenna structure using low-loss, low-cost plastic substrate stack-up for multi-band applications; FIG. 4 shows the return loss data in dB and illustrates that the antenna is well matched for dual-band applications;

FIG. 5 is a far-field plot at 2.45 GHz for the monopole antenna structure with good gain and radiation efficiency;

FIG. 6 illustrates three-metal-layer antenna designs with S-parameter and 3D- gain (dBi) plots; and

FIG. 7 shows the schematic for an ultra-compact, embedded antenna structure using multi-layers of metal patterns and thru-metal vias on a low-loss, low-cost plastic substrate stack-up.

It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.

The present invention as described herein shows multi-band Front End Modules (FEMs) incorporating a multi-layer plastic substrate technology for wireless applications. The FEM includes the PA, required matching and filtering, and Transmit/Receive (T/R) modules for broadband or dual direction applications. The plastic substrate stack-up provides a positive impact on the module overall size, cost, and functionality.

The embodiment illustrated in FIG. 1 shows a wireless communications device 10 that includes one or more antenna structures 14 fabricated on the multi-layer plastic substrate that allow radios to communication with other over-the-air communication devices. Antenna structure 14 in accordance with the present invention is an embedded antenna(s) using the multi-metal layers from RF front-end module packaging substrate stack-up that result in an ultra-small form size. As such, communications device 10 may operate as a cellular device or a device that operates in wireless networks such as, for example, Wireless Fidelity (Wi-Fi) that provides the underlying technology of Wireless Local Area Network (WLAN) based on the IEEE 802.11 specifications, WiMax and Mobile WiMax based on IEEE 802.16-2005, Wideband Code Division Multiple Access (WCDMA), and Global System for Mobile Communications (GSM) networks, although the present invention is not limited to operate in only these networks. The radio subsystems collocated in the same platform of communications device 10 provide the capability of communicating with different frequency bands in an RF/location space with other devices in a network.

The simplistic embodiment illustrates the coupling of antenna structure 14 to the transceiver 12 to accommodate modulation/demodulation. In general, analog front end transceiver 12 may be a stand-alone Radio Frequency (RF) discrete or integrated analog circuit, or transceiver 12 may be embedded with a processor having one or more processor cores 16 and 18. The multiple cores allow processing workloads to be shared across the cores and handle baseband functions and application functions. Data may transfer through an interface between the processor and memory storage in a system memory 20. FIG. 2 illustrates a compact, multi-layer monopole-type antenna structure 14 using a low-loss, low-cost substrate stack-up that is useful for multi-band applications. The multi-layer substrate stack-up can be a low-loss plastic substrate stack-up, a polymer substrate stack-up, or a thin material organic substrate stack-up suitable for FEMs. Whereas multi-metal layers from a high-performance substrate stack-up traditionally have been used for embedded lumped elements such as, for example, inductors and capacitors, etc, the present invention uses similar metal structures to show small high-performance antenna structures that maintain multi-band antenna characteristics. The ultra-compact antennas described in the present invention have excellent gain and an input matching that is desirable for ultra-mobile device type small- form factor environments.

As shown in the figure, the substrate stack-up includes a number of substrates 212, 214, ..., 216, etc., having patterned metal layer lines formed on surfaces of the substrates. The intermediate dielectrics between the metal layers have low-loss characteristics and are suitable for high-performance antenna applications. The monopole-type antenna structure utilizes the patterns and ground plane from the radio- front-end board as well as grounds from different parts of the small form-factor mobile wireless device-type mechanical structures. Any ground surface from a small-form- factor platform or radio design may be utilized to embed these antennas. The grounds for these very small-size antennas can be accessed by using insulated metal thru-via structures. FIG. 3 illustrates several layers of the substrate stack-up to show metal lines on surfaces of different substrate layers that may be connected by thru- and blind- vias 226 to form the antenna structures. It should be noted that different embodiments may use substrate stack-ups having two, three, four, five, or six metal layers to achieve the multi- frequency band operation, although the number of substrate layers in the stack-up and the number of metal layers used to form the antenna structures is not limiting to the present invention. The combination of the metal layers patterned on the various substrates produces a structure that may be used, for example, to achieve multi-band, high-gain performance antennas with sizes less than 30 sq.mm on a 0.5 mm substrate stack-up for WLAN type applications. In the exemplary structure shown in the figure, two metal layers are used in the antenna design on multi-layer plastic packaging substrate stack-up. Potentially, the multi-layer plastic substrate stack-up is well suited for future generation low-cost multi- radio front-end modules. A first metal layer line 222 is patterned on substrate 212 and a second metal layer line 224 is patterned on a substrate 214. A via 226 is etched or formed in substrate 212 to provide the low impedance electrical connection of the first metal layer line 222 to the second metal layer line 224. Mutual inductances and capacitances between the multi-metal-layer lines such as lines 222 and 224 are utilized to define an operating frequency and an optimum bandwidth in multi-layer antenna structure 14. FIG. 4 shows the return loss data in dB for the multi-layer monopole antenna structure and illustrates that the antenna is well matched for dual-band WLAN applications. The line widths of first metal layer 222 and second metal layer 224 (briefly see FIG. 3) and the spacing between the lines can be optimized to achieve good radiation patterns at desired frequency bands in a small form-factor environment. Metal transmission line structures with 50 ohm impedances excite the antenna input, and results show that an antenna size of approximately 6.5 x 6.6 x 0.5 cubic mm size provides multi-frequency band operation and operates at both 2.4 GHz and 5.5 GHz frequency bands. The bandwidth can be increased by modifying the metal line widths and the metal patterns of this antenna structure.

FIG. 5 is a far-field plot at 2.45 GHz for the monopole antenna structure 14 with 6.14 dBi gain and excellent radiation efficiency. The performance presented in this figure is for a two-layer antenna structure illustrated in FIGs. 3 and 4. The antenna structure exhibits radiation at the fringing fields that results in a certain far-field radiation pattern. This radiation pattern shows that the antenna radiates more power in a certain direction than another direction. The antenna is said to have certain directivity as is commonly expressed in dB.

FIG. 6 illustrates three-metal-layer Wi-Fi and WiMax antenna designs with S- parameter and 3D- gain (dBi) plots. The figure presents an antenna with 2.5 GHz and 5.5 GHz Wi-Fi dual-bands achieving a gain of 2.58 dBi at 2.5 GHz. The figure also presents a 3-layer antenna for the 3.5 GHz WiMax band with 3.7 dBi gain. The antennas cover the entire bandwidth of the Wi-Fi and WiMAX bands and demonstrate a return loss of less than -10 dB.

FIG. 7 shows the electromagnetic simulation schematic for an ultra-compact, embedded antenna structure using 4-layers of metal patterns and thru-metal vias on a low-loss, low-cost plastic substrate stack-up. The figure shows the metal patterns and connecting metal-vias that form the 4-layer antenna.

In an alternate embodiment to using the multi-layer organic plastic substrate stack-up, Low Temperature Co-fired Ceramic (LTCC) substrate stack-ups may be used. However, LTCC materials have a higher dielectric-constant that impacts the radiation efficiency and impedance bandwidth of an antenna because of pronounced surface wave excitations in higher dielectric material, resulting in degradation in radiation patterns. Further, the loss characteristics of LTCC materials are higher than or comparable to the organic plastic substrate materials due to the screen printed Ag metal definition.

By now it should be apparent that embodiments of the present invention allow low-cost antennas to operate on different platforms and be integrated with multi-radio System-On-Packages (SOP). Future wireless systems will include multiple radios and integration of multiple-band antennas to handle WLAN, WiMax, BT, GPS, DVBH, among others. These thin and light mechanical casings will require ultra-small antenna architectures integrated with the radio. These antennas can be monolithically integrated with the front-end-modules (FEM) of the multi-radio architectures for ultra-small form factor mobile device type applications to reduce cost and enhance performance. While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

Claims:

1. A Front End Module (FEM) for multi-frequency band applications, comprising: a monopole-type antenna formed in a multi-layer organic based plastic substrate stack-up for the FEM by a first metal layer patterned on a surface of a first substrate in the stack-up and connected by a via in the first substrate to a second metal layer patterned on a surface of a second substrate in the stack-up.

2. The FEM of claim 1 , wherein the monopole-type antenna is formed using multiple metal layers on plastic packaging substrates.

3. The FEM of claim 1 , wherein the substrate stack-up includes low-loss dielectric characteristics.

4. The FEM of claim 1 , wherein the monopole-type antenna formed in the multi-layer organic plastic substrate covers multiple frequency bands.

5. The FEM of claim 1 , wherein the first metal layer and second metal layer are connected by thru- and blind- vias to form antenna structures.

6. The FEM of claim 1 , wherein the first metal layer and second metal layer are used in a multi-layer organic plastic substrate stack-up to achieve the multi-frequency band operation.

7. The FEM of claim 1 , wherein a combination of metal layers patterned on the multi-layer organic plastic substrate stack-up is used to achieve multi- band antennas for small form factor communication device applications.

8. A multi-layer antenna structure for multi-frequency band applications, comprising: first and second metal layers in a multi-layer substrate stack-up to form the multi-layer antenna structure.

9. The multi-layer antenna structure of claim 8 wherein the multi-layer substrate stack-up is a plastic substrate stack-up.

10. The multi-layer antenna structure of claim 8 wherein the multi-layer substrate stack-up is an organic substrate stack-up.

11. The multi-layer antenna structure of claim 8 wherein the multi-layer substrate stack-up is a polymer substrate stack-up.

12. The multi-layer antenna structure of claim 8 wherein the multi-layer substrate stack-up includes the first metal layer patterned on a surface of a low- loss first substrate in the multi-layer substrate stack-up that is connected through a via in the first low-loss substrate to a second metal layer patterned on a surface of a second low-loss substrate in the multi-layer substrate stack-up.

13. The multi-layer antenna structure of claim 8 wherein mutual inductances and capacitances between the first and second metal layers define an operating frequency and a bandwidth in the multi-layer antenna structure.

14. A portable device, comprising: a Front End Module (FEM) for multi-frequency band applications; and a multi-layer antenna structure formed in a multi-layer plastic substrate stack-up and coupled to the FEM, the multi-layer antenna structure in the multilayer plastic substrate including a first metal layer patterned on a first substrate in the multi-layer plastic substrate stack-up and connected by a via to a second metal layer patterned on a second substrate in the multi-layer plastic substrate stack-up.

15. A portable device of claim 14, wherein the first and second metal layers are included in the multi-layer plastic substrate stack-up.

16. The portable device of claim 14, wherein the multi-layer antenna structure is formed using multiple metal layers on low-loss plastic packaging substrates.

17. The portable device of claim 14, wherein the multi-layer plastic substrate stack-up includes low-loss dielectric characteristics.

18. The portable device of claim 14, wherein the multi-layer antenna structure formed in the multi-layer plastic substrate stack-up covers dual frequency bands.

19. A wireless device having multi-frequency band communication, comprising: multiple radios in a Front End Module (FEM); multiple processor cores coupled to the FEM; and first and second antennas formed in a multi-layer plastic substrate stack- up of the FEM by a first metal layer patterned on a surface of a first substrate in the stack-up and connected by a via to a second metal layer patterned on a surface of a second substrate in the stack-up.

20. The wireless device of claim 19 wherein the antennas are formed on the multi-layer plastic substrate stack-up having low-loss substrate characteristics.

21. The wireless device of claim 19 wherein the antennas formed in the multi-layer plastic substrate stack-up cover dual frequency bands.

22. The wireless device of claim 19 wherein an organic or polymer plastic material is stacked to form the multi-layer plastic substrate stack-up.