Avago Technologies's Articles
Integrated RF Modules for Saving Time and Space
Applications for portable wireless data communications are on the rise with the advent of initiatives such as smart power and with rapid growth in markets for portable devices such as tablet PCs. To be successful in these applications, however, designs need to have multiple higheffi ciency, low-noise RF channels in as small a space as possible. By adopting integrated RF modules, designers can achieve such superior coexistence faster and more efficiently than by using discrete component designs.
Wireless is becoming the preferred method for consumer and commercial data communications of all kinds. WiFi networks abound in the home, supporting such devices as PCs, tablets, smartphones, gaming systems, and even televisions. Public WiFi “hotspots” are also plentiful, used for web surfi ng, messaging, and creating femtocells for the off -load of cellular network IP traffic.
There are also many other wireless data links in use beyond WiFi, including Bluetooth for remote headsets, Zig-Bee for home automation networks, WiMAX and LTE for wireless broadband, and cellular telephony. In addition, transportation and utility industries are working to employ many of these same network technologies for applications such as the smart power grid and traffi c management. Similarly, other industries seek to employ wireless networks for machine-to-machine communications to automate various elements in production and commerce.
This growing dependence on wireless data communications places a two-fold burden on equipment developers. First, their designs must provide extremely high quality transmit and receive channels. Transmit channels must meet strict power, spectral, and linearity standards, providing sharp bandwidth filtering while avoiding amplifier distortions and the reflections caused by impedance mismatches. Receive channels must be efficient to avoid signal loss and must eliminate as much noise as possible in order to maximize data rates while dealing with very low received signal strengths.
Figure 1 Using an Avago integrated front-end module can reduce a complex discrete RF design to a single component, saving board space, easing design eff orts, and reducing cost.
While addressing these RF design challenges developers must also deal with the burden of channel coexistence. Many systems need not one but two or more wireless links, each corresponding to diff erent standards. A laptop computer, for instance, might incorporate both WiFi and WiMAX connectivity in its design. A smartphone will include WiFi with Bluetooth as well as GSM, 3G, and LTE. Such portable systems also require the RF designs for the various channels to be as compact as possible and the diff erent channels are typically interwoven on the circuit board.
These various wireless links that must coexist in the same design typically operate on narrowly-spaced frequency bands using co-located or even shared antennas. This physical and spectral proximity places stringent demands on receive fi lters. For example, a WiFi design may need to operate over a 2.4 – 2.5 GHz band while rejecting signals from a nearby 3G transmitter at 2.1 GHz. Such tight frequency spacing requires fi lters with extremely steep roll-offs.
Figure 2 Amplifi ers, switches, and fi lters are all encapsulated in a shielded package for simple layout.
But developers have an ally in meeting the many challenges of these compounding design burdens: integrated front-end modules (FEM) for RF coexistence from Avago Technologies. These integrated modules provide independent transmit and receive paths with in-line fi lters and amplifi ers along with signal switches for sharing antenna connections. Utilizing an integrated module rather than pursuing a discrete-component design allows developers to signifi cantly reduce their design eff ort and costs while creating highly precise and effi cient RF subsystems. The modules save board space, as well, compared to discrete designs (Figure 1).