X. Wang, U. Moon, G. C.Temes
DIGITAL CORRELATION TECHNIQUE FOR THE ESTIMATION AND CORRECTION OF DAC ERRORS IN MULTIBIT MASH ΔΣ ADCS

A fully digital algorithm is described for acquiring and correcting the errors of the feedback DAC used in a multibit ΔΣ MASH ADC. The method operates in the background and is highly accurate. It is particularly useful for wideband ADCs, where mismatch error shaping becomes ineffective. Combined with an improved digital adaptive compensation technique, which greatly reduces the raw quantization leakage in MASH architecture, it makes the design of fast and accurate ADCs using inaccurate components possible.

Alan J. Davies, Godi Fischer, Hans-Helge Albrecht, Jürgen Hess
IMPROVED NULL CANCELLATION IN A 6^th-ORDER Σ-Δ MODULATOR REALIZED WITH TWO 3^rd-ORDER SECTIONS

This paper presents an improved rnethod to digitally correct for statit, analog circuit imnperfections in a two-stage, 6^th order, cascaded (6-3) sigma-delta modulator. By adding a digital correction term to the output of die digital noise cancellation filter, the first stage parasitic quantization noise due to finite amplifier gain and C-Ratio mismatches can be completely removed. A 6-3 modulator implemented as a fully differential switched-capacitor circuit, designed for an OSR of 16, has heen fabricated in a 1.2 µm double-poly n-well CMOS process. Improvements have been made in the null cancellation leading to approximately a 10 dB increase in SNDR ovor a range of signal amplitudes from 12 µVolts to 500 mV. A peak SNDR/SFDR of 87/100 dB for a 1 MHz sample rate and 84/93 dB for a 2.5 MHz sample rate have heen achieved.

T.H. Pearce
ADC DYNAMIC RANGE IMPROVEMENT FOR WIDEBAND HF RECEIVERS

The development of 14 bit monolithic Analogue to Digital Converters (ADC’s) capable of sampling at 80 MHz has revived interest in digitising the entire 3-30 MHz High Frequency (HF) radio spectrum for use in wideband HF receivers. This enables the ADC to be placed close to the antenna so removing the need for analogue mixing as well as offering a multi-channel reception capability, using multiple digital synthesisers and direct conversion I, Q mixing to baseband ...

J. Roztocil, D. Varga, M. Siroky
ASPECTS OF LOW DISTORTION SINE WAVE GENERATORS MEASUREMENT

This paper deals with testing of ultra-low distortion sine wave generators. Measurement of harmonic distortion based on lock-in amplifiers is described and practical results using fundamental-suppression method are presented.

A.A. Platonov, K. Jędrzejewski, J. Jasnos
MATHEMATICAL AND COMPUTER MODELS IN MULTI-PASS ADC DESIGN AND OPTIMISATION

The paper presents a mathematically grounded approach to the analysis and optimisation of multi-pass analogue-to-digital converters (MADCs) with the algorithmic forming the estimates of converted samples. The approach enables a comprehensive analysis of the converter work using a virtual model of MADC built on the basis of its mathematical model. This model is based on the extended optimal identification algorithms adapted to the particularities of A/D conversion. The obtained sub-optimal algorithms take into account all main parameters of the internal auxiliary ADC and other analogue elements of MADC. The results of advanced simulations confirm a full agreement of theoretical and experimental evaluations, as well as efficiency of the proposed approach as a tool for MADC design support.