In this paper, we focus on the design and analysis of the Analog Fountain Code (AFC) for short packet communications. We first propose a density evolution (DE) based framework, which tracks the evolution of the probability density function of the messages exchanged between variable and check nodes of AFC in the belief propagation decoder. Using the proposed DE framework, we formulate an optimisation problem to find the optimal AFC code parameters, including the weight-set, which minimizes the bit error rate at a given signal-to-noise ratio (SNR). Our results show the superiority of our code design in comparison to existing code designs and thus the validity of the proposed DE framework in the asymptotic block length regime. We then focus on the selection of the precoder to improve the performance of AFC at short block lengths. Simulation results show that lower precoder rates obtain better realised rates over a wide SNR range for short information block length.
An ultra-wideband power amplifier (PA) design employing Real Frequency Technique (RFT) with Gallium Nitride high-electron-mobilitytransistor (GaN HEMT) technology is presented. The practical implementation was done with combination of distributed and lumped elements (mixed lumped elements combination) for the need of industrial requirements for the small form factor and low cost. This is an attractive approach for Software Defined Radio (SDR) products to meet wide bandwidth range of 80-2200 MHz. The measured results of the prototype reported good performance over the bandwidth of the interest (i.e. power of 34 dBm to 43 dBm, efficiency about 39% to 69% and gain in the range of 11 dB to 18 dB), and reasonable agreement with the simulated data. According to author's knowledge, these results are significant for single-ended GaN HEMT device for the wideband operation starting from low frequency 80-2200 MHz.
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