MULTICHANNEL PARALLEL ANALOG-TO-DIGITAL CONVERTER WITH REFERENCE VOLTAGE OFFSET AND GAIN CORRECTION

Abstract

The paper presents a method for expanding the dynamic range of multichannel analog-to-digital converters (ADC) of parallel type. It is indicated that the analog-to-digital conversion method, which is based on the multichannel architecture of the parallel ADC, allows improving the frequency characteristics of radio engineering systems with digital processing of radio signals.

The qualitative indicators of multichannel ADC will depend on the identity of the ADC parameters in each of the conversion channels. The non-identity of the ADC reference voltage offset values ​​is associated with the spread of the parameters of the built-in operational amplifiers and comparators and the asymmetry of the ADC conversion stages. The non-identity of the gain coefficients in the ADC channels is due to the parasitic capacitances and inductances of the operational amplifiers, as well as the differences in the input parameters of analog comparators.

To find the offset value of the reference voltage, it is necessary to choose the reference voltage of one of the ADC channels as an example. Then the averaged root mean square deviation of the digital signal from the outputs of the parallel ADCs relative to the exemplary ADC will determine the offset of the reference voltage value. The difference in the gain coefficients of the parallel ADCs can be found in a similar way, except that instead of the deviation of the digital signal, it is necessary to determine the modulus of this signal at the output of each ADC channel.

It is proposed to adjust the gain coefficients and reference voltage offsets of individual ADC channels. A structural diagram of a multi-channel parallel ADC with adjustment of the gain coefficients and reference voltage offsets of individual ADC channels has been developed.

An analysis of the effectiveness of the developed method confirmed that the proposed method allows to expand the dynamic range of the ADC by 12 - 15 dB depending on the frequency value of the ADC input signal.

The proposed multi-channel parallel ADC can be used in modern digital radio engineering systems.