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Instrumentation Research

Digital sideband separating down-conversion for YTLA
Image Credit: Chao-Te Li
Digital sideband separating down-conversion for YTLA
A down-conversion method involving digital sideband separation is adopted for the Yuan-Tseh Lee Array (YTLA) to double the processing bandwidth. The sideband separation scheme includes 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 × 1.6 GHz band can be tuned to cover any 3.2 GHz window within the 2-18 GHz IF of the array. Sideband rejection ratios (SRRs) above 30 dB can be achieved when calibration is applied.
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