docomo Newsletter Mobility 33
Less Is More: DOCOMO’s Mobile Phone Power Amp Cuts Space, Adds Flexibility
June. 15, 2011
The increasing functionality of smartphones and feature phones is forcing manufacturers to cram more and more circuits and components within the confined space of mobile handsets, adding to the challenge of producing highly functional yet small, lightweight devices.
At present, mobile handsets equipped for multi-band operation use sets of power amplifiers, one for each frequency band. With the worldwide launch of LTE services and accompanying increase in frequency bands (see graphic), efforts to offer multi-market handsets seemed destined to result in larger and more costly devices.
Thanks to the research efforts of DOCOMO, however, manufacturers can breathe a collective sigh of relief. On May 20, 2011, the company announced that its newly developed prototype power amplifier for six frequency bands between 1.5 GHz and 2.5 GHz is smaller than sets of single-band power amplifiers conventionally bundled onto one chip.
Spectral Dilemma
All mobile phones employ power amplifiers to raise each frequency band to the level needed for transmission. DOCOMO’s FOMA™ 3G service launched with one band, 2GHz, but now uses 800MHz, 1.7GHz and 2GHz, requiring handsets to have power amplifiers for each band. GSM support also has been incorporated to enable users to roam internationally. As a result, additional power amps have had to be installed, increasing the cost and size of newer handsets.
To solve the dilemma, DOCOMO foresaw the need for a power amplifier unit that could support the growing range of frequency bands and wireless systems. The company began working on the development of a band-switchable matching circuit that would enable a single power amplifier to work with multiple frequency bands.
DOCOMO’s Innovative Solution
DOCOMO’s newly announced prototype power amplifier accommodates six frequency bands between 1.5 GHz and 2.5 GHz, yet only takes up 8.05mm x 6.2mm. Since a typical single-band configuration requires about 3mm x 3mm for each frequency, the svelte six-band solution uses less space to provide the same function. As a result, the module can help to minimize handset size and weight.
But how did researchers achieve this remarkable breakthrough?
The solution was a proprietary “one-chain” methodology that uses a single chain of input and output terminals for all frequency bands. By contrast, single-band models use more than two chains (see graphic).
Powering the Mobile Evolution
DOCOMO’s new multi-band prototype means manufacturers can use a single power amplifier module in smartphones and other handsets for multiple markets, enabling them to reduce development time and cost, as well as minimize device size and weight.
Moreover, for Japanese manufacturers, the new power amplifier will enable products to be equipped easily for compatibility with overseas networks.
The envisioned commercial version of the prototype is expected to accelerate the global introduction of LTE services and corresponding devices. In the foreseeable future, commercialization of DOCOMO’s multi-band power amplifier could play a key role in the development of handsets worldwide.
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