4G challenge needs agile PA firms
GaAs companies competing in the 4G market must produce chips that combine efficiency and linearity over a wide range of frequencies in order to succeed.
That s according to Wavesat, a Canadian baseband chip vendor and system designer whose first 4G products will reach consumers in 2009.
Victor Menasce, Wavesat s chief technology officer, told compoundsemiconductor.net that the high data transmission rates central to the technology are a particular challenge to power amplifier (PA) engineering.
“As you go to the higher data rates, you re also getting into higher forms of modulation,” he said. “The amplifiers must be extremely linear, which is easy to do if you're willing to consume a lot of power.”
“If you want to be very power efficient and be linear, that s hard - there's only a very select number of vendors in the world who can achieve that.”
Rather than the better known Long-Term Evolution (LTE) and WiMAX fourth-generation wireless standards, Wavesat's first products will enter the XG-PHS network run by Japanese carrier Willcom.
The ability to cover the complete set of frequencies in which the various standards operate is a core selling point for the company's Odyssey 8500 baseband system-on-chip. It is also looking to match that flexibility when it selects which PAs will partner the Odyssey in its reference designs. They currently feature Anadigics and SiGe Semiconductor.
“I don t have to want to go to one vendor for this frequency and have to go to another PA vendor for another frequency,” Menasce said.
“I want to go to the guys that can cover enough of the waterfront that they re going to have similar performance and characteristics in different frequency bands.”
The need for one GaAs or SiGe firm to provide power efficiency across multiple frequencies becomes more important with 4G protocols that use multiple-input, multiple-output (MIMO) transmissions. These demand arrays of PAs with only small performance differences, but which can have a debilitating effect on battery life as they mount up.
Although the Odyssey 8500 largely sells on its ability to enable data transmission at different standards, its WiMAX experience has not yet seen PA proliferation.
“So far in most of the products that our customers are building, I m seeing one PA that will address a range of frequencies,” Menasce said.
This could mark a distinct shift from the current approach to 3G handsets, which today typically use several GaAs devices. Although this may ultimately mean that they sell fewer chips, Menasce says it s the PA manufacturing firms driving this trend.
“My belief is that it s going to be simpler, generally we re seeing the vendors make these amplifiers much more agile than they did in the past. I think we're seeing a significant improvement with each generation.”
