Implementation of a High Speed Digital Band-Pass Sigma-Delta Modulator for a Wireless Transmitter

Abstract

Digital sigma-delta modulators are used extensively in CMOS wireless SoC designs to achieve high-resolution data conversion while controlling the quantization noise spectrum. This paper presents an implementation of a 90nm CMOS digital band-pass sigma-delta modulator (SDM), running at 900 MHz. Conventional sigma-delta structures required to achieve such noise shaping are hardware intensive and do not meet the timing requirements when synthesized in 90nm technology using a static CMOS implementation. In this work, we present an unrolled LA architecture to achieve the necessary rate of operation. Unrolling is achieved by running two loops at half the frequency, while maintaining algorithmic equivalency between the original and proposed structures. The proposed architecture meets timing requirements of 900 MHz across all PVT corners at the cost of increase in area. The operating frequency for most of the hardware is halved, resulting in a 20% power consumption reduction.

Enhancement of Coexistence Performance in a DRP Based Multi-Radio Environment of a Mobile Phone

“…To channel interference can then be filtered in the digital minimize the energy of this emission source in specific domain more accurately and efficiently. In addition to the bands, the transmitter may digitally shape the output noise simplification and improvement of the adjacent channel of the I-A modulator as suggested in [2], [3] and [7], having filtering, the higher dynamic-range and sampling rates of an implementation advantage over conventional E-A the ADC enable the receiver to accommodate wideband architectures [6].…”

A Low Area and Low Power Digital Band-Pass Sigma-Delta Modulator for Wireless Transmitters

“…Figure 1 illustrates a typical sigma-delta ADC structure. The same concept can be applied in the implementation of a digital sigma-delta modulator [4], as illustrated in Figure 2. In general, a digital sigma-delta modulator replaces the analog integrator of its analog counterpart by a digital accumulator and the analog quantizer by a digital comparator.…”

“…One of the applications of such a digital band-pass ¦¡ modulator is in the Digital RF Processor (DRP Ì Å ) [4], [5] to enhance the resolution of the digital RF transmitter while controlling the spectrum of its quantization noise. The sigma-delta modulator shapes its quantization noise according to its Noise Transfer Function (NTF), achieving spectral content compliant to the RF specifications.…”

“…The obvious solution is to use a band-pass ¦¡ modulator, which adds zeros (notches) at desired frequencies and attenuates quantization noise in the band of interest [1] and [4]. Referring to Figure 5, the position of such zeros can be controlled by varying the gain parameter Ê.…”

“…However, designing a digital band-pass ¦¡ modulator at RF rate is extremely area intensive and power consuming [4]. The presented architecture of a digital band-pass ¦¡ modulator has different comb-like NTF.…”