High-Resolution Analog-to-Digital Converters toward Software-Defined-Radio Receivers

Akira FUJIMAKI  Yoshinori NISHIDO  Akito SEKIYA  

IEICE TRANSACTIONS on Electronics   Vol.E89-C   No.2   pp.113-118
Publication Date: 2006/02/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e89-c.2.113
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Section on Superconducting High-frequency Devices)
analog-to-digital converter,  superconductor,  software-defined-radio,  single-flux-quantum,  

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We describe three types of software-defined-radio (SDR) receivers based on superconducting technologies. The superconducting analog bandpass filters are essential for all types of the receivers. Another key component is an analog-to-digital converters (ADCs), which are required to have high resolution with a broad band width. The complementary Δ ADC based on the single-flux-quantum circuit is a promising candidate for the SDR receivers because it has a practical nature together with above-mentioned requirements. The experimentally obtained signal-to-noise ratio (SNR) and sensitivity, which are closely related to the resolution, are 34 dB and 20 µA for a quarter of the full-scale input with a band width of about 20 MHz. If we use the optimum decimation filter, the ADC is expected to have the SNR of 82 dB and the sensitivity of 300 nA. These values meet the requirements of the easiest type of the SDR receiver. After new fabrication process has been introduced and the architecture of the ADC has been improved, all types of recievers could be realized based on superconductors.