Hyeong-Seok Yu

Effects of RF impairments in transmitter for the future beyond-3G communications systems

In this paper, the performance degradation of a MIMO OFDM-based beyond-3G system, due to various impairments in the radio frequency (RF) circuitry such as AM-AM distortion of power amplifier (PA), in-phase/quadrature-phase (IQ) mismatch effects, is investigated. In order to accurately assess the overall effects of RF impairments on the system performance, constellation diagram and power spectral density (PSD) of the waveform as well as the traditional quantitative figures of merits like error vector magnitude (EVM) of the complete baseband/RF link are used. By analyzing the experimental results, the specification for the RF impairments that ensures a tolerable level of performance can be determined

Area-efficient and reusable VLSI architecture of decision feedback equalizer for QAM modern

In this paper, an area efficient VLSI architecture of decision feedback equalizer is derived accommodating 64/256 QAM modulators. This architecture is implemented efficiently in reusable VLSI structure using EDA tool due to its regular structure. The main idea is to employ a time-multiplexed design scheme grouping the adjacent filter taps with correlated internal dataflow and with data transfer having same processing sequence between blocks. We simulated the proposed design scheme using SYNOPSYSTM and SPWTM. Index Terms - Decision feedback equalizer, QAM, reusable VLSI implementation, FIR filter.