19 July 2016 Development of digital sideband separating down-conversion for Yuan-Tseh Lee Array
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Abstract
This report presents a down-conversion method involving digital sideband separation for the Yuan-Tseh Lee Array (YTLA) to double the processing bandwidth. The receiver consists of a MMIC HEMT LNA front end operating at a wavelength of 3 mm, and sub-harmonic mixers that output signals at intermediate frequencies (IFs) of 2–18 GHz. The sideband separation scheme involves an analog 90° hybrid followed by two mixers that provide down-conversion of the IF signal to a pair of in-phase (I) and quadrature (Q) signals in baseband. The I and Q baseband signals are digitized using 5 Giga sample per second (Gsps) analog-to-digital converters (ADCs). A second hybrid is digitally implemented using field-programmable gate arrays (FPGAs) to produce two sidebands, each with a bandwidth of 1.6 GHz. The 2 x 1.6 GHz band can be tuned to cover any 3.6 GHz window within the aforementioned IF range of the array. Sideband rejection ratios (SRRs) above 20 dB can be obtained across the 3.6 GHz bandwidth by equalizing the power and delay between the I and Q baseband signals. Furthermore, SRRs above 30 dB can be achieved when calibration is applied.
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Chao-Te Li, Chao-Te Li, Derek Kubo, Derek Kubo, Jen-Chieh Cheng, Jen-Chieh Cheng, John Kuroda, John Kuroda, Ranjani Srinivasan, Ranjani Srinivasan, Solomon Ho, Solomon Ho, Kim Guzzino, Kim Guzzino, Ming-Tang Chen, Ming-Tang Chen, "Development of digital sideband separating down-conversion for Yuan-Tseh Lee Array", Proc. SPIE 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, 99140E (19 July 2016); doi: 10.1117/12.2230961; https://doi.org/10.1117/12.2230961
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