Optimization problem formulation for semi-digital FIR digital-to-analog converter considering coefficients precision and analog metrics

Abstract

Optimization problem formulation for semi-digital FIR digital-to-analog converter (SDFIR DAC) is investigated in this work. Magnitude and energy metrics with variable coefficient precision are defined for cascaded digital RD modulators, semi-digital FIR filter, and Sinc roll-off frequency response of the DAC. A set of analog metrics as hardware cost is also defined to be included in SDFIR DAC optimization problem formulation. It is shown in this work, that hardware cost of the SDFIR DAC, can be significantly reduced by introducing flexible coefficient precision while the SDFIR DAC is not over designed either. Different use-cases are selected to demonstrate the optimization problem formulations. A combination of magnitude metric, energy metric, coefficient precision and analog metrics are used in different use cases of optimization problem formulation and solved to find out the optimum set of analog FIR taps. A new method with introducing the variable coefficient precision in optimization procedure was proposed to avoid non-convex optimization problems. It was shown that up to 22% in the total number of unit elements of the SDFIR filter can be saved when targeting the analog metric as the optimization objective subject to magnitude constraint in pass-band and stop-band.

A voltage-mode RF DAC for massive MIMO system-on-chip digital transmitters

“…The IQ modulator translates the analog signal to the desired RF band. As the number of antenna elements grows, for instance in LTE-A, to up to eight elements per radio, the integration of the baseband DAC and analog IQ modulator was more efficient in terms of overall radio size and cost [13,14,21]. In massive MIMO however, the number of antenna elements increases dramatically, and a digital transmitter with an RF DAC solution is more beneficial as there is no analog mixer limitation and therefore simultaneous multi-band operation becomes easier.…”

Studies on Selected Topics in Radio Frequency Digital-to-Analog Converters

“…The IQ modulator translates the analog signal to the desired RF band. As the number of antenna elements grows, for instance in LTE-A, to up to eight elements per radio, the integration of the baseband DAC and analog IQ modulator was more efficient in terms of overall radio size and cost [76,79,109].…”

“…Semi-digital FIR filters or sometimes called analog FIR filters, are used as frequency selective filters as well as converting from digital domain to analog domain since it uses analog multipliers as filter taps. The analog multipliers are implemented by means of current sources, in conventional SDFIR filters, if the output of the Σ∆ modulator quantizer is a single bit [116,122,18,34,87,105,124,46,109]. In fact each tap is one-bit DAC and they are weighted according to the filter coefficients.…”

“…The optimization problem formulation for a semi-digital FIR DAC presented in this thesis, considers a linear-phase FIR filter functionality [109]. As a future direction within the semi-digital FIR filter design topic, the work…”

Direct digital-to-RF converter employing semi-digital FIR voltage-mode RF DAC

“…Semi-digital FIR filters or sometimes called analog FIR filters, are used as frequency selective filters as well as converting from digital domain to analog domain since it uses analog multipliers as filter taps. The analog multipliers are implemented by means of current sources, in conventional SDFIR filters, if the output of the Σ∆ modulator quantizer is a single bit [15,16,17,18,19,20,21,12,22]. In fact each tap is one-bit DAC and they are weighted according to the filter coefficients.…”