Abstract
Sigma-delta (-) modulation techniques have moved into mainstream applications in signal processing and have found many practical uses in areas such as high-resolution A/D, D/A conversions, voice communication, and software radio.- modulators produce a single, or few bits output resulting in hardware saving and thus making them suitable for implementation in very large scale integration (VLSI) circuits. To reduce quantization noise produced, higher-order modulators such as multiloop and multistage architectures are commonly used. The quantization noise behavior of higher-order- modulators is well understood. Based on these quantization noise characteristics, various demodulator architectures, such as filter, optimal FIR filter, and Laguerre filter are reported in literature. In this paper, theory and design of an efficient Kalman recursive demodulator filter is shown. Hardware implementation of Kalman lowpass filter, using field programmable gate array (FPGA), is explained. The FPGA synthesis results from Kalman filter design are compared with previous designs for sinc filter, optimum FIR filter, and Laguerre filter.
Highlights
Σ-Δ modulation techniques have been successfully applied in numerous applications such as low-cost and highresolution A/D and D/A converters, software-defined radio [1, 2], correlators, multipliers, and synchronizers [3].One main reason for popularity of Σ-Δ modulation lies in its ability to trade bandwidth with quantization noise
The quantization noise power resulting from Laguerre lowpass filter is the same as that resulting from an optimum FIR filter
Application specific integrated circuit (ASIC) offers the most efficient hardware implementation, the rapid realization achieved by using field programmable gate array
Summary
Σ-Δ modulation techniques have been successfully applied in numerous applications such as low-cost and highresolution A/D and D/A converters, software-defined radio [1, 2], correlators, multipliers, and synchronizers [3]. The applications of Σ-Δ require proper lowpass filters as demodulators to remove quantization noise. Theory and efficient realization of a Kalman lowpass filter is described and implemented in hardware using field programmable gate array (FPGA). The simulation and synthesis results of FPGA implementation of the filter are reported. Comparison of synthesis results among various FPGA filter designs including sinc filter, optimum FIR filter, Laguerre filter, and Kalman filters, both down-sampled and full-rate, is given.
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