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Jen-Chieh Cheng

Publications and source records attributed to Jen-Chieh Cheng.

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BURSTT: Bustling Universe Radio Survey Telescope in Taiwan

Fast Radio Bursts (FRBs) are bright millisecond-duration radio transients that appear about 1,000 times per day, all-sky, for a fluence threshold 5 Jy ms at 600 MHz. The FRB radio-emission physics and the compact objects involved in these events are subjects of intense active debate. To better constrain source models, the Bustling Universe Radio Survey Telescope in Taiwan (BURSTT) is optimized to discover and localize a large sample of rare, high-fluence, nearby FRBs. This is the population most amenable to multi-messenger, multi-wavelength follow-up, allowing deeper understanding of source mechanisms. BURSTT will provide horizon-to-horizon sky coverage with a half power field-of-view (FoV) of $\sim$10$^{4}$ deg$^{2}$, a 400 MHz effective bandwidth between 300-800 MHz, and sub-arcsecond localization, made possible using outrigger stations hundreds to thousands of km from the main array. Initially, BURSTT will employ 256 antennas. After tests of various antenna designs and optimization of system performance we plan to expand to 2048 antennas. We estimate that BURSTT-256 will detect and localize $\sim$100 bright ($\geq$100 Jy ms) FRBs per year. Another advantage of BURSTT's large FoV and continuous operation will be greatly enhanced monitoring of FRBs for repetition. The current lack of sensitive all-sky observations likely means that many repeating FRBs are currently cataloged as single-event FRBs.

astro-ph.IM

Metal Mesh IR Filter for wSMA

Since the start of full science operations from 2004, the Submillimeter Array has been implementing plans to expand IF bandwidths and upgrade receivers and cryostats. Metal mesh low-pass filters were designed to block infrared (IR) radiation to reduce the thermal load on the cryostats. Filters were fabricated on a quartz wafer through photolithography and coated with anti-reflection (AR) material. The filters were tested from 200 to 400 GHz to verify their passband performances. The measurement results were found to be in good agreement with EM simulation results. They were tested in the far-infrared (FIR) frequency range to verify out-of-band rejection. The IR reflectivity was found to be approximately 70%, which corresponded to the percentage of the area blocked by metal.

astro-ph.IM

Development of digital sideband separating down-conversion for Yuan-Tseh Lee Array

This report presents a down-conversion method involving digital sideband separation for the Yuan Tseh Lee Array to double the processing bandwidth. The receiver consists of a MMIC HEMT LNA frontend operating at a wavelength of 3 mm, and sub-harmonic mixers that output signals at intermediate frequencies of 2 - 18 GHz. The sideband separation scheme involves an analog 90 degree 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 analog to digital converters. A second hybrid is digitally implemented using field programmable gate arrays 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 3.2 GHz window within the aforementioned IF range of the array. Sideband rejection ratios (SRRs) above 20 dB can be obtained across the 3.2 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.

astro-ph.IM