Sungwon Chung

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— We describe a new outphasing transmitter architecture in which the supply voltage for each PA can switch among multiple levels. It is based on a new asymmetric multilevel outphasing (AMO) modulation technique which increases overall efficiency over a much wider output power range than the standard LINC system while maintaining high linearity. For(More)
—We demonstrate energy-efficient low-complexity adaptive linearization for wideband handset power amplifiers (PAs). Due to power overhead and complexity, traditional wideband linearization techniques such as adaptive digital pre-distortion (DPD) thus far have not been used for wideband handset transmitters. Our energy-efficient lookup table training(More)
— We present a high-efficiency transmitter based on asymmetric multilevel outphasing (AMO). AMO transmitters improve their efficiency over LINC (linear amplification using nonlinear components) transmitters by switching the output envelopes of the power amplifiers among a discrete set of levels. This minimizes the occurrence of large outphasing angles,(More)
— We present a high-efficiency wideband transmitter architecture based on asymmetric multilevel out-phasing (AMO), but with a new method of generating discrete amplitude levels from the constituent amplifiers. AMO and multilevel LINC (ML-LINC) transmitters improve their efficiency over LINC by switching the supplies of the power amplifiers (PAs) among a(More)
— We present a new adaptive power amplifier (PA) linearization technique. We leverage analog Cartesian feedback (CFB) to train a Cartesian look-up table, reducing DSP and power amplifier modeling requirements to a minimum and eliminating model convergence as a design issue. Because the CFB system does not continuously operate, we overcome the bandwidth(More)
A method of performing diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) of the fetal brain in utero is proposed. The major difficulty of performing diffusion imaging in utero is the presence of motion. By modifying conventional single-shot spin-echo echo-planar DWI with a short repetition time sequence, a sequence that performs DWI and(More)
We present a digitally assisted subsampler, designed to serve as the downconversion path in adaptive predistorters for 800MHz–5.8GHz RF power amplifiers. We use digital averaging to overcome the noise folding problems of subsampling, obtaining a final SNDR of 73.1dB for signals centered about a 2.4GHz carrier. Using quadra-ture subsampling, we obtain both(More)
Since the complex and transient information in instructional animations requires more cognitive resources, the segmenting principle has been proposed to reduce cognitive overload by providing smaller chunks with pauses between segments. This study examined the effects of different types of activities during pauses in a segmented animation. Four groups were(More)