The Best Paper Award
Low-Loss Matching Network Design for Band-Switchable Multi-Band Power Amplifier
Atsushi Fukuda , Takayuki Furuta , Hiroshi Okazaki , Shoich Narahashi (NTT DOCOMO),
Toshio Nojima (Hokkaido University)
（英文論文誌C　平成24年7月号掲載）
Atsushi Fukuda Takayuki Furuta Hiroshi Okazaki Shoich Narahashi Toshio Nojima  
　There has　been　an　increase　in　the　number　of　frequency　bands　allocated　to　mobile　communication　services　provided all over the world. Radio frequency (RF) circuits that are incorporated in future mobile terminals will be expected to function over multiple bands. A commonly used scheme for RF circuits operating over multiple bands is “unit selection”. This scheme includes several units each of which operates in a single band. The total circuit size basically increases in proportion to the number of units. A power amplifier (PA) is a key device in RF circuits. The PA has a much greater impact on power consumption than any other component in the RF circuits for mobile terminals. Therefore, matching networks are needed which offer low loss even when they have to cover multiple bands, where the upper and lower frequency limits are far apart, because the PA must achieve a high level of operating efficiency in order to maximize the battery life of mobile terminals.
　The authors have proposed band switchable matching networks (BS-MNs) that change their frequency response using switch devices. This structure represents a promising solution because it uses a reasonably sized circuit configuration, considering multiple band operation, while providing optimal matching conditions in each band. However, there are some issues that need to be addressed in applying practical switches, i.e., switches that have insertion losses and insufficient isolation characteristics, to the BS-MN. This paper presents a novel design scheme for configuring the BS-MNs with a lower power consumption. This paper also describes numerical quantitative analysis results of the power consumption of the proposed BS-MN. These analysis results yield design parameters to achieve a low loss BS-MN. Adopting these design parameters for the BS-MN, a 3-stage PA, with 9 bands ranging from 0.7-2.5 GHz and 4-V operation voltage, has been newly designed and fabricated. The experimental results of the 9-band PA show a gain exceeding 30 dB for each frequency band. The PA achieves an output power exceeding 33 dBm with a maximum power added efficiency of over 40% in the targeted bands.
　This paper has been highly appreciated because the practical design scheme for highly efficient multi-band PAs has been validated thorough fabricating and testing. Furthermore, it is expected that the design scheme will be applied to various multi-band RF circuits for which there is a strong demand.

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