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An all-digital sigma-delta modulator (SDM) based RF synthesizer is presented. A multiplier-less architecture for the implementation of the band-pass SDM loop filter is proposed. Furthermore, this architecture enables the adjustment of the loop filter central frequency by exploiting homodyne up- and down-conversion. The RF synthesizer is comprised of a direct digital synthesizer (DDS) and the proposed...
Band-pass sigma-delta modulators (SDMs) can be used for all-digital frequency synthesis with low noise in the SDM passband. To avoid mixed-signal components such as DACs, a single-bit output is required. The noise shaping characteristics of single-bit sigma-delta modulators are limited by stability requirements. Look-ahead SDMs have been proposed to increase the bandwidth and signal-to-noise-and-distortion...
All-digital frequency synthesis using two low-pass single-bit Multi-Step Look-Ahead sigma-delta modultors (MSLA SDMs) is presented. MSLA SDMs provide better noise shaping characteristics, i.e. SNDR and bandwidth, than conventional SDMs at the cost of higher hardware complexity. The balance between complexity and performance is adjusted by the number of look-ahead steps, which is an additional design...
All-digital frequency synthesis architectures with direct modulation capability, based on single-bit sigma-delta modulation loop with an innovative homodyne band-pass filter topology are presented focusing on wireless Internet of Things (IoT) applications. A hardware-efficient multiplier-free variation of the homodyne filter is also proposed. MATLAB simulation results for 16-QAM modulation demonstrate...
An all-digital RF transmitter architecture capable of driving directly a switching RF power amplifier and therefore without the need of a high-speed RF DAC is presented. Modulation is achieved by directly modulating a direct digital synthesizer (DDS) generated signal. The proposed architecture is based on single-bit sigma-delta modulation using the introduced homodyne band-pass filter topology, which...
The class of 1-bit Multi-Step Look-Ahead (MSLA) ΣΔ modulators is presented. They take into account current and future quantization errors improving upon the stability and noise shaping characteristics of conventional 1-bit ΣΔ modulators. The MSLA modulator system is found to be equivalent to a number of parallel conventional ΣΔ modulators sharing a multi-input 1-bit quantizer. The number of look-ahead...
A method to calculate the transfer functions of Multi-Step Look-Ahead (MSLA) ΣΔ modulators is presented. MSLA ΣΔ modulators exhibit better noise shaping characteristics and stability than conventional ones. They are comprised of a number of conventional ΣΔ modulators in parallel, sharing a multi-input 1-bit output quantizer. MSLA modulators are highly nonlinear systems due to the multi-input quantizer...
Digital Multi-Step Look-Ahead (MSLA) 1-bit $\Sigma $ -$\Delta $ modulators are introduced. They improve upon the stability and noise shaping characteristics of conventional 1-bit $\Sigma $ -$\Delta $ modulators by minimizing quantization error metrics of the current and future output samples. The mathematical model of the proposed MSLA modulators is analyzed. It is shown that the MSLA modulators...
A configurable single-bit-output Σ-Δ modulator variant is presented, which improves upon stability and dynamic range. The derivation of the proposed modulation scheme from the Σ-Δ error-feedback structure and its mathematical description are analyzed, while its application in fractional-N frequency dividers and all-digital frequency synthesizers is investigated. It is shown that stable high-order...
This work discusses hardware implementation considerations for a novel Multi-Step Look-Ahead modulation architecture which improves on the stability and dynamic range of conventional Σ-Δ modulators for all-digital frequency synthesis applications. The basic theoretical concepts of the architecture are analyzed and an appropriate general hardware implementation of the required mathematical operations...
This paper proposes a compact RF all-digital transmitter that is based on a direct digital synthesizer topology combined with Sigma-Delta modulation and other digital techniques to produce a spurs-free, high-frequency, single or few bit output with improved noise floor performance.
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