This paper introduces a quasi-passive Noise-Shaping Successive Approximation Register Analog-to-Digital converter (NS-SAR ADC) suited for low power Audio Activity Detection (AAD). Exploiting a 2ndorder Error-Feedback (EF) loop filter implemented through a low power open loop amplifier, insensitive to Process-Voltage-Temperature (PVT) variations, and a fully passive Charge-Sharing (CS) summing node, this converter reaches 78 dB of Dynamic Range (DR), achieving a Schreier Figure-of-Merit (FoMs) of 165.3 dB. Fabricated in a 65-nm BCD process, the proposed ADC core occupies 0.129 µm2consuming 14.9 µW from a 1.2-V supply.

This paper describes and analyzes low-density parity-check code families that support variety of different rates while maintaining the same fundamental decoder architecture. Such families facilitate the decoding hardware design and implementation for applications that require communication at different rates, for example to adapt to changing channel conditions. Combining rows of the lowest-rate parity-check matrix produces the parity-check matrices for higher rates. An important advantage of this approach is that all effective code rates have the same blocklength. This approach is compatible with well known techniques that allow low-complexity encoding and parallel decoding of these LDPC codes. This technique also allows the design of programmable analog LDPC decoders. The proposed design method maintains good graphical properties and hence low error floors for all rates.

The performance of a Reed-Solomon (RS) code has an analytical expression if the errors at the input of the decoder are independent. In concatenated schemes, this condition is often obtained through an interleaving device disrupting the correlation between erroneous symbols. Sometimes the ideal depth of such interleaver is too large to implement, and the RS decoder must operate in suboptimal conditions, for which no analytical formulas are available. In this paper, we present a statistical model that allows analytical evaluation of the performances of a concatenated scheme with an inner turbo code and an outer RS code, in the case of under-dimensioned interleavers. The model requires a statistical analysis of the erroneous symbols at the output of the inner decoder.

The prediction of the directivity function of a GPR antenna still remains a partially unsolved problem because of the subject complexity. First, the far-field conditions are often not satisfied and second, the antenna design has little in common with the Hertzian dipole for which an analytical approach can be used. The authors' contribution is both theoretical and experimental. On one side, they solve the (electromagnetic) EM integral equations numerically to derive the wavefield components from near to far-field distances. On the other side, they experiment with two novel techniques for measuring the directivity functions in the near to far-field range on dry and saturated sand. Theoretical and experimental results show that neither the analytic approximation of far-field directivity for the numerical integration of near-field directivity can perfectly match the measured functions, although near-field solutions are generally more consistent. The mismatch should be attributed to the present-day GPR antenna design that includes absorbers and shields. Although the effects of these elements are not included in the present numerical near-field solutions, they believe the approach to be of practical value to predict an average directivity function. A smoothed version of the analytic far-field solution can also be used in the range of the near to far-field transition but near-field solutions are really recommended when TX-RX distances are shorter than five wavelengths.