Browsing by Author "Hwang, TS"

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Broad-band (>= 20 GHz) laser-diode-based optoelectronic microwave phase shifter
(1998-10-01)
Lin, GR
;
Hwang, TS
;
Chuang, YH
;
Wang, SC
;
Pan, CL
We demonstrate a new type of broad-band microwave phase shifter with superior performance at frequencies up to 20 GHz. This is implemented by simply adding an offset voltage prior to the loop filter (LF) in a laser-diode-based digital optoelectronic phase-locked loop (OEPLL), Accurate control of the phase of microwave signals with a continuously tunable range exceeding 640 degrees (similar to 3.6 pi) is achieved. The phase fluctuation and long-term drift of ally desired phase shift are as small as +/-0.4 degrees and 0.08 degrees, respectively, at 20 GHz, The relative phase instability can be maintained within 0.09 degrees while operating in a phase-shift-keying (PSK) scheme, We also demonstrate accurate control of relative phase difference between dual phase-locked microwave sources using the phase shifter. Our results indicate potential application of this broad-band optoelectronic phase shifter in a phased-array antenna system.
Delayed precise invalidation - A software cache coherence scheme
(1996-09-01)
Hwang, TS
;
Lu, NP
;
Chung, CP
;
交大名義發表
;
資訊工程學系
Software cache coherence schemes are very desirable in the design of scalable multiprocessors and massively parallel processors. The authors propose a software cache coherence scheme named 'delayed precise invalidation' (DPI). DPI is based on compiler-time markings of references and a hardware local invalidation of stale data in parallel and selectively. With a small amount of additional hardware and a small set of cache management instructions, this scheme provides more cacheability and allows invalidation of partial elements in an array, overcoming some inefficiencies and deficiencies of previous software cache coherence schemes.