Experimental Investigations of Intermodulation Distortion in Tunable Ferroelectric Phase Shifters

Dongsu KIM
James Stevenson KENNEY

Publication
IEICE TRANSACTIONS on Electronics   Vol.E88-C    No.12    pp.2310-2315
Publication Date: 2005/12/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.12.2310
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Wireless Technologies and Computational Electromagnetics)
Category: Devices
Keyword: 
ferroelectrics,  barium strontium titanate (BST),  phase shifters,  intermodulation distortion,  

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Summary: 
This paper investigates intermodultation distortion in ferroelectric phase shifters depending on bias voltage. Two analog phase shifters based on barium-strontium-titantate (BST) coated sapphire substrates have been fabricated with interdigital capacitors (IDCs) which have 2 and 4 µm spacing between adjacent fingers. In case of the phase shifter with 4 µm-spaced IDCs, a phase shift of more than 121was obtained with a maximum insertion loss of 1.8 dB from 2.4 to 2.5 GHz over a bias voltage range of 0-140 V. The phase shifter with 2 µm-spaced IDCs exhibited a phase shift of more than 135with a maximum insertion loss of 2.37 dB in the same frequency range. In this case, a bias voltage of 80 V was used. Using 2 and 4 µm-spaced phase shifters, a third-order intermodulation (IM3) measurement was carried out with a two-tone cancellation setup to investigate nonlinearity, resulting in an input third-order intercept point (IIP3) of about 30.5 dBm and 38.5 dBm, respectively.