A 5 GHz high-temperature superconducting reaction-type transmitting filter based upon split open-ring resonators

概要

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A new kind of high-temperature superconducting (HTS) transmitting filter based on a reaction-type resonator is presented. The purpose of an HTS reaction-type filter (HTS-RTF) is to eliminate the intermodulation distortion noise generated by microwave power amplifiers such as those employed in mobile base stations. An HTS-RTF enables both higher power handling capability and sharper cutoff characteristics compared to existing planar-type HTS transmitting filters, since a reaction-type resonator does not resonate with high-power fundamental signals. To achieve steep skirt characteristics and high-power handling capability simultaneously, a 5-GHz three-pole HTS-RTF using split open-ring resonator is designed. This split open-ring resonator offers low maximum current densities and a high-unloaded Q-factor with low radiation. The designed prototype filter has Chebyshev characteristics with a centre frequency of 4.95 GHz and a bandwidth of 1.5 MHz. The HTS-RTF is fabricated using a double-sided YBa_2C_3O_[7-δ] thin film deposited on a 0.5 mm thick MgO substrate. The measured filter shows an insertion loss of less than 0.1 dB and a third intermodulation distortion value of - 56.7 dBc for a 40 dBm passband signal. In addition, adjacent channel leakage power ratio (ACLR) measurements using an actual Wideband CDMA signal confirm an ACLR improvement of about 10 dB for a four-carrier signal with power of up to 40 dBm.
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