OPINION RF FRONT-END COMPONENTS
Left: The RF front end for mobile devices such as smartphones is becoming increasingly complex as a growing number of bands are added to support 2G/3G/4G voice and data services, as well as global roaming. This is driving demand for superior efficiency, as well as high- performance filters
Right: TriQuint’s multi- mode, multi-band power amplifier module (MMPA) mixes GaAs and silicon technologies to achieve best-in-class performance
applications where a superior cost or size tradeoff can be achieved by integrating the switch with a GaAs PA die, rather than using two separate die.
Providing control and biasing circuits within amplifier modules is one area where silicon has been used for many years. In addition, power detectors, temperature sensors and regulators have a long silicon history. These silicon circuits often comprise one die within a multiple-die module. Recently, module control has been transitioning from a few dedicated functional digital pins to a control bus architecture. This change is driven by the increasing number of bands and functions in front-end modules, as well as the desire to minimize the required control pins out of the transceiver or baseband. Silicon will remain the preferred choice for control buses as the MIPI front end interface becomes more widely adopted.
One of the trends within cellular technology has been a steady increase in the number of frequency bands. This has made it more challenging to achieve good radiated performance in
compact form factors, due to the expanded bandwidth. Making matters even worse, there is a desire for multiple antennas in MIMO (multiple-input and multiple-output) applications, and this is pushing space constraints. To address all of this, designers are exploring tuning technologies to optimize antenna performance. There are several competing variations in the RF space, including some silicon-based components; the market has yet to throw its weight behind one particular technology.
Filtering out the noise Filters play a crucial role in the RF front end, because they selectively pass certain frequencies while rejecting unwanted noise. Unlike PAs, which can cover multiple bands, filters are band specific, so growth in phone band counts leads directly to growth in the number of filters or duplexers within each device.
Many of the new bands allocated for LTE present tough, technical problems associated with filter design. Amid a global spectrum crunch, new 4G bands are being squeezed next to pre-existing bands, often with minimal guard bands. To mitigate the resulting interference issues, it is essential to employ advanced filter technology. Traditional surface acoustic wave (SAW) technologies have been adequate in the past, but the most challenging 3G/4G frequency bands need advanced filter technologies, such as bulk acoustic wave (BAW) or temperature-compensated SAW – we offer all three.
In addition, service providers want to increase network capacity through the introduction of aggregation techniques, and high- performance filters can make this possible. Due to the rapid deployment of LTE, shipments of filters for the RF front-end are forecast to outpace the growth in PA content. These filters can be discrete components, or they can be integrated as filter banks or filter banks with switches. They also have the potential to be combined in components with higher levels of front-end integration. This represents an expanding market opportunity for III-V suppliers with advanced filter technologies – they are the key to delivering a complete RF solution.
The deployment of 4G LTE networks is driving band counts and increasing demand for high-performance filter technologies like BAW and TC-SAW
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www.compoundsemiconductor.net June 2013
© 2013 Angel Business Communications. Permission required.
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