A Novel Filter Construction Utilizing HTS Reaction-Type Filter to Improve Adjacent Channel Leakage Power Ratio of Mobile Communication Systems

Takashi HIKAGE

IEICE TRANSACTIONS on Electronics   Vol.E92-C    No.3    pp.307-314
Publication Date: 2009/03/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E92.C.307
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Superconducting Analog Devices and Their Applications)
Category: Microwaves
adjacent channel leakage power ratio,  high-temperature superconductor,  intermodulation distortion,  power handling capability,  reaction-type filter,  

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We propose a new band selective stop filter construction to decrease the out of band intermodulation distortion (IMD) noise generated in the transmitting power amplifier. Suppression of IMD noise directly improves the adjacent channel leakage power ratio (ACLR). A high-temperature superconducting (HTS) device with extremely high-Q performance with very small hybrid IC pattern would make it possible to implement the proposed filter construction as a practical device. To confirm the effectiveness of the HTS reaction-type filter (HTS-RTF) in improving ACLR, investigations based on both experiments and numerical analyses are carried out. The structure of a 5-GHz split open-ring resonator is investigated; its targets include high-unload Q-factor, low current densities, and low radiation. A designed 5-GHz HTS-RTF with 4 MHz suppression bandwidth and more than 40 dB MHz-1 sharp skirt is fabricated and experimentally investigated. The measured ACLR values are improved by a maximum of 12.8 dB and are constant up to the passband signal power of 40 dBm. In addition, to examine the power efficiency improvement offered by noise suppression of the HTS-RTF, numerical analyses based on measured results of gallium nitride HEMT power amplifier characteristics are conducted. The analyzed results shows the drain efficiency of the amplifier can be improved to 44.2% of the amplifier with the filter from the 15.7% of the without filter.