研究成果藝廊 > 李遠哲陣列望遠鏡計畫(YTLA, 原簡稱AMiBA)

研究成果藝廊

李遠哲陣列望遠鏡計畫(YTLA, 原簡稱AMiBA)

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In-Phase/Quadrature Down Converter Prototype Plate, YTLA Project

圖片來源: Derek Kubo

Early prototype of in-phase/quadrature down converter for YTLA upgrade. The goal was to down convert and digitize any 2 GHz portion of the 2-18 GHz IF spectra from the receiver output using our new in-house board development of a 5 Gsps ADC board (courtesy of H.M. Jiang).

Two of these I/Q down converters were designed and produced to validate the concept of sideband separation. The concept is based on producing two local oscillators that are in phase quadrature with respect to each other and used to separately down convert a single IF signal (2-18 GHz) into two separate baseband (0-2 GHz) I and Q signals. Each of these baseband signals consist of both sidebands, i.e., "lower sideband minus LO" and "LO minus upper sideband". A second quadrature performed within the digital domain allows the separation of lower and upper sidebands by virtue of even and odd functions (cosine is symmetrical about zero where as sine is not). These two prototypes were deemed successful and was followed by a production run of 16 units utilizing a modified mechanical layout. The two prototypes were developed by Derek Kubo and John Kuroda in Hilo and tested by Chaote Li and Homin Jiang in Taipei.